Achieve Mastery of Medical Concepts

Study for medical school and boards with Lecturio

USMLE Step 1     |     USMLE Step 2   |    COMLEX Level 1   |     COMLEX Level 2   |     ENARM   |    NEET

Create your free account
The Lecturio Medical Concept Library
Shigella

Shigella

Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular Facultative intracellular Yersinia spp./Yersiniosis bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli. Because it is resistant to acid, Shigella spp. survive transit through the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy; thus, only a small amount of inoculum is needed to cause disease. Shigellosis (Shigella dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis) results in fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, abdominal pain Abdominal Pain Acute Abdomen, and bloody diarrhea Bloody diarrhea Diarrhea, which are effects of the toxins and epithelial-cell invasion of the organism. In the majority of cases, symptoms resolve within a few days. However, complications of dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration, hemolytic uremic syndrome Hemolytic uremic syndrome A syndrome that is associated with microvascular diseases of the kidney, such as renal cortical necrosis. It is characterized by hemolytic anemia; thrombocytopenia; and acute renal failure. Hypocoagulable Conditions, toxic megacolon Toxic megacolon An acute form of megacolon, severe pathological dilatation of the colon. It is associated with clinical conditions such as ulcerative colitis; Crohn disease; amebic dysentery; or Clostridium enterocolitis. Megacolon, or reactive arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis can arise. Treatment is primarily using fluid and electrolyte replacement and antibiotics.

Last updated: 16 Feb, 2021

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Classification

Gram negative bacteria classification flowchart

Gram-negative bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology:
Most bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology can be classified according to a lab procedure called Gram staining Gram staining Bacteriology.
Bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology with cell walls that have a thin layer of peptidoglycan Peptidoglycan Penicillins do not retain the crystal violet stain utilized in Gram staining Gram staining Bacteriology. These bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology do, however, retain the safranin counterstain and thus appear as pinkish-red on the stain, making them gram negative Gram negative Bacteria which lose crystal violet stain but are stained pink when treated by gram’s method. Yersinia spp./Yersiniosis. These bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology can be further classified according to morphology (diplococci, curved rods, bacilli, and coccobacilli) and their ability to grow in the presence of oxygen (aerobic versus anaerobic). The bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology can be more narrowly identified by growing them on specific media (triple sugar iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements (TSI) agar) where their enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes can be identified ( urease Urease An enzyme that catalyzes the conversion of urea and water to carbon dioxide and ammonia. Nocardia/Nocardiosis, oxidase Oxidase Neisseria) and their ability to ferment lactose can be tested.
* Stains poorly on Gram stain Gram stain Klebsiella
** Pleomorphic Pleomorphic Bacteroides rod/coccobacillus
*** Require special transport media

Image by Lecturio.

General Characteristics

Shigella spp.

  • General characteristics:
  • Associated disease: shigellosis ( dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis or Shigella diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea)

Clinically relevant species

Serogroups defined by specific O antigens:

  • S. dysenteriae (serogroup A)
  • S. flexneri (serogroup B)
  • S. boydii (serogroup C)
  • S. sonnei (serogroup D)

Epidemiology

  • Shigellosis worldwide: 164,000 deaths annually
  • In low- to middle-income countries: 
    • Shigella: the most common etiology of dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis in children
    • Most common: S. flexneri, followed by S. sonnei
    • S. dysenteriae: causes epidemic dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis
    • Insufficient sewage disposal is one of the main culprits.
  • In the United States:
    • Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 4.8 cases per 100,000 population
    • Children most affected
    • Most common: S. sonnei (> 75%), S. flexneri
    • Settings:
      • Institutions such as daycare centers
      • Untreated recreational water

Related videos

4:08
Shigella – Enteric Bacteria

Pathogenesis

Reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli and transmission

  • Reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli: human intestinal tract
  • Transmission:
    • Contaminated food or water, usually fecal-oral transmission
    • Person-to-person contact (e.g., lack of hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy washing, sexual transmission in men who have sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria with men)

Mnemonic

To help remember the modes of transmission of Shigella, remember the “4 Fs:”

  • Fingers
  • Flies
  • Food
  • Feces

Virulence factors Virulence factors Those components of an organism that determine its capacity to cause disease but are not required for its viability per se. Two classes have been characterized: toxins, biological and surface adhesion molecules that affect the ability of the microorganism to invade and colonize a host. Haemophilus

  • Endotoxin Endotoxin Toxins closely associated with the living cytoplasm or cell wall of certain microorganisms, which do not readily diffuse into the culture medium, but are released upon lysis of the cells. Proteus: 
    • Toxic lipopolysaccharide Lipopolysaccharide Lipid-containing polysaccharides which are endotoxins and important group-specific antigens. They are often derived from the cell wall of gram-negative bacteria and induce immunoglobulin secretion. The lipopolysaccharide molecule consists of three parts: lipid a, core polysaccharide, and o-specific chains (o antigens). When derived from Escherichia coli, lipopolysaccharides serve as polyclonal b-cell mitogens commonly used in laboratory immunology. Klebsiella
    • Causes bowel-wall irritation
  • Shiga toxin Shiga toxin A class of toxins that inhibit protein synthesis by blocking the interaction of ribosomal RNA; with peptide elongation factors. They include shiga toxin which is produced by Shigella dysenteriae and a variety of shiga-like toxins that are produced by pathologic strains of Escherichia coli such as Escherichia coli o157. Diarrheagenic E. coli: 
    • Produced by S. dysenteriae type 1 Type 1 Spinal Muscular Atrophy
    • Inhibits binding of aminoacyl- tRNA tRNA The small RNA molecules, 73-80 nucleotides long, that function during translation (translation, genetic) to align amino acids at the ribosomes in a sequence determined by the mRNA (RNA, messenger). There are about 30 different transfer rnas. Each recognizes a specific codon set on the mRNA through its own anticodon and as aminoacyl trnas (RNA, transfer, amino Acyl), each carries a specific amino acid to the ribosome to add to the elongating peptide chains. RNA Types and Structure to the 60S ribosome, leading to cessation of protein synthesis Synthesis Polymerase Chain Reaction (PCR) 
    • Causes colonic mucosal damage, leading to sloughing and dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis
    • Other changes (noted in hemolytic uremic syndrome Hemolytic uremic syndrome A syndrome that is associated with microvascular diseases of the kidney, such as renal cortical necrosis. It is characterized by hemolytic anemia; thrombocytopenia; and acute renal failure. Hypocoagulable Conditions ( HUS HUS Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by shiga-like toxin-producing bacteria. Hemolytic Uremic Syndrome)):
      • The toxin is translocated into circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment and induces endothelial damage, particularly in the glomeruli.
      • Damaged endothelium Endothelium A layer of epithelium that lines the heart, blood vessels (vascular endothelium), lymph vessels (lymphatic endothelium), and the serous cavities of the body. Arteries: Histology causes platelet aggregation Platelet aggregation The attachment of platelets to one another. This clumping together can be induced by a number of agents (e.g., thrombin; collagen) and is part of the mechanism leading to the formation of a thrombus. Hemostasis. 
      • RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology are lysed → schistocytes Schistocytes Hemolytic Uremic Syndrome/schizocytes (fragmented RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology)
  • Shigella enterotoxin Enterotoxin Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc. ; most common enterotoxins are produced by bacteria. Diarrhea 1 (ShET1; S. flexneri) and Shigella enterotoxin Enterotoxin Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc. ; most common enterotoxins are produced by bacteria. Diarrhea 2 (ShET2; 4 species) cause fluid secretion Secretion Coagulation Studies and subsequent watery diarrhea Watery diarrhea Rotavirus.
  • Type III secretion Secretion Coagulation Studies system:
    • Directly delivers virulence Virulence The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its virulence factors. Proteus effectors to the host cell
    • Facilitates bacterial invasion of epithelial cells
  • Resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to gastric acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance:
    • Shigella can survive the acidic environment of the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy during transit.
    • Thus, only a small inoculum is required to produce disease.

Disease process

  • Shigella:
    • Technically immobile
    • Invade host cells ( ileum Ileum The distal and narrowest portion of the small intestine, between the jejunum and the ileocecal valve of the large intestine. Small Intestine: Anatomy and colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy) by induced phagocytosis Phagocytosis The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (phagocytes). Innate Immunity: Phagocytes and Antigen Presentation
  • Invasion:
    • Entry via microfold (M) cells of the intestinal Peyer’s patches Patches Vitiligo (transcytosis):
      • M cells M cells Salmonella engulf the pathogen from the lumen and then transport it to the sub- epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology.
      • From the M cells M cells Salmonella, the pathogen is taken up by subepithelial Subepithelial Membranoproliferative Glomerulonephritis macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation (also by neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation, dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions).
      • Macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation undergo apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage, and the released pathogen invades intestinal epithelial cells. 
    • During apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage, released cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response recruit polymorphonuclear leukocytes Leukocytes White blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes). White Myeloid Cells: Histology (PMNs):
      • PMNs destabilize the junctions between epithelial cells, allowing the pathogen to go across the disrupted junction.
      • PMN transmigration Transmigration Leukocyte Adhesion Deficiency Type 1 is another entryway for Shigella sp., leading to further invasion.
    • Uptake in epithelial cells:
      • Once in the epithelial cytosol Cytosol A cell’s cytoskeleton is a network of intracellular protein fibers that provides structural support, anchors organelles, and aids intra- and extracellular movement. The Cell: Cytosol and Cytoskeleton, the pathogen hijacks the host cell actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction nucleators.
      • Then, the host actin filaments Actin filaments Fibers composed of microfilament proteins, which are predominately actin. They are the smallest of the cytoskeletal filaments. The Cell: Cytosol and Cytoskeleton ( actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction tail) are used to move within the cell ( actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction-based motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility (ABM)).
    • Protrusion formation and resolution:
      • ABM propels the pathogen to the membrane and a protrusion is created in the membrane into the neighboring cell.
      • The protrusion elongates and resolves as a double-membrane vacuole. 
      • The pathogen lyses the vacuole, escapes, and infects the adjacent cell (cell-to-cell spread).
    • Invasion does not involve deep penetration Penetration X-rays; thus, no hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread
    • Effects: inflammatory response ( colitis Colitis Inflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever. Pseudomembranous Colitis) → mucosal ulcerations, abscesses, bleeding, and formation of a “ pseudomembrane Pseudomembrane Candida/Candidiasis” on the ulcerated area
Invasion and cell-to-cell spread by shigella

Invasion and cell-to-cell spread by Shigella:

1. Pathogen invades and is engulfed by the M cell (transcytosis).
2. Pathogen reaches subepithelial Subepithelial Membranoproliferative Glomerulonephritis macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation and dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions, then induces macrophage apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage. Shigella sp. is released along with interleukin-1 Interleukin-1 A soluble factor produced by monocytes; macrophages, and other cells which activates T-lymphocytes and potentiates their response to mitogens or antigens. Interleukin-1 is a general term refers to either of the two distinct proteins, interleukin-1alpha and interleukin-1beta. The biological effects of il-1 include the ability to replace macrophage requirements for t-cell activation. Interleukins (IL-1) and other cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response. The pathogen is then engulfed into the adjacent epithelial cell in a membrane-bound compartment (epithelial-cell entry).
3. Released interleukins Interleukins Interleukins are a type of cytokines (signaling proteins) that communicate messages between different parts of the immune system. The majority of interleukins are synthesized by helper CD4 T lymphocytes along with other cells such as monocytes, macrophages, and endothelial cells. Interleukins also recruit polymorphonuclear leukocytes Leukocytes White blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes). White Myeloid Cells: Histology (PMNs), which destabilize the cellular junctions. This is another entryway for the pathogen (PMN transmigration Transmigration Leukocyte Adhesion Deficiency Type 1).
4. Shigella sp. passes through the disrupted tight junctions Tight junctions Cell-cell junctions that seal adjacent epithelial cells together, preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other. The Cell: Cell Junctions and then the pathogen enters the epithelial cell. Once inside, the host cell actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction nucleators are hijacked. Actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction-based motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility (ABM; actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction tail) propels the pathogen to reach the plasma membrane Plasma membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane, where the infected cell contacts another cell.
5. Multiplication and intercellular spread are facilitated by cellular protrusion (with Shigella) and elongation Elongation Polymerase Chain Reaction (PCR) into the adjacent cell. The protrusion resolves as a double-membrane vacuole. The pathogen lyses the membrane, escapes, and enters the adjacent cell. The adjacent cell is infected and this process is repeated in other cells.
6. As each invaded epithelial cell dies, fluids are lost.

Image by Lecturio.

Clinical Presentation

  • Shigellosis:
    • Incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period: 1–4 days
    • Watery diarrhea Watery diarrhea Rotavirus initially, then dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis ( diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea with blood and mucus)
    • Accompanied by abdominal pain Abdominal Pain Acute Abdomen, tenesmus, and fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • In the majority of cases, resolution is noted within 5 days.
    • In high-risk populations ( immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis, elderly, and children < 5 years of age), fluid and electrolyte losses can lead to dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration and possible death.
  • Other complications:
    • HUS HUS Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by shiga-like toxin-producing bacteria. Hemolytic Uremic Syndrome:
      • Shigella is the 2nd most common cause of HUS HUS Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by shiga-like toxin-producing bacteria. Hemolytic Uremic Syndrome.
      • Mediated by Shiga toxin Shiga toxin A class of toxins that inhibit protein synthesis by blocking the interaction of ribosomal RNA; with peptide elongation factors. They include shiga toxin which is produced by Shigella dysenteriae and a variety of shiga-like toxins that are produced by pathologic strains of Escherichia coli such as Escherichia coli o157. Diarrheagenic E. coli
      • Usually occurs in children under 10 years of age
      • Typically associated with S. dysenteriae type 1 Type 1 Spinal Muscular Atrophy
    • Toxic megacolon Toxic megacolon An acute form of megacolon, severe pathological dilatation of the colon. It is associated with clinical conditions such as ulcerative colitis; Crohn disease; amebic dysentery; or Clostridium enterocolitis. Megacolon:
      • Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation involves the smooth muscular layer resulting in colonic paralysis and dilation.
      • Abdominal distention Abdominal distention Megacolon and tenderness
    • Other intestinal sequelae: bowel obstruction Bowel obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Ascaris/Ascariasis, perforation Perforation A pathological hole in an organ, blood vessel or other soft part of the body, occurring in the absence of external force. Esophagitis
    • Rectal prolapse Rectal prolapse Rectal prolapse, also known as rectal procidentia, is the protrusion of rectal tissue through the anus. The tissue may include just the mucosa or the full thickness of the rectal wall. Common risk factors include chronic straining, constipation, bowel motility disorders, and weakening of the pelvic floor muscles. Rectal Prolapse:
      • Due to inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation in the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy
      • Affects young children
    • Reactive arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis:
      • Associated with S. flexneri
      • Joint pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways 1–4 weeks after infection ( oligoarthritis Oligoarthritis Ankylosing Spondylitis, enthesitis Enthesitis Ankylosing Spondylitis, dactylitis Dactylitis Ankylosing Spondylitis, inflammatory back pain Back pain Back pain is a common complaint among the general population and is mostly self-limiting. Back pain can be classified as acute, subacute, or chronic depending on the duration of symptoms. The wide variety of potential etiologies include degenerative, mechanical, malignant, infectious, rheumatologic, and extraspinal causes. Back Pain)
      • Extraarticular findings: conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis, urethritis Urethritis Inflammation involving the urethra. Similar to cystitis, clinical symptoms range from vague discomfort to painful urination (dysuria), urethral discharge, or both. Urinary tract infections (UTIs), oral ulcers Oral ulcers A loss of mucous substance of the mouth showing local excavation of the surface, resulting from the sloughing of inflammatory necrotic tissue. It is the result of a variety of causes, e.g., denture irritation, aphthous stomatitis; necrotizing gingivitis, toothbrushing, and various irritants. ChĂ©diak-Higashi Syndrome
    • Neurological effects:
      • Generalized seizures Generalized Seizures Seizures: associated with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and more common in children
      • Encephalopathy Encephalopathy Hyper-IgM Syndrome
    • Leukemoid reaction:

Diagnosis and Management

Diagnosis

  • Gram stain Gram stain Klebsiella and culture: fresh stool or rectal swab
    • Gram negative Gram negative Bacteria which lose crystal violet stain but are stained pink when treated by gram’s method. Yersinia spp./Yersiniosis
    • Differential media: eosin methylene blue (EMB) or MacConkey’s agar, showing non-lactose-fermenting colonies
    • Selective media: HE agar (green transparent colonies) or xylose-lysine-deoxycholate agar
    • Triple sugar iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements (TSI): alkaline slant, acid at the bottom, and no Hâ‚‚S
  • Polymerase chain reaction Polymerase chain reaction Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) ( PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR)): Shigella-specific deoxyribonucleic acid Deoxyribonucleic acid A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure ( DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure) in stool detected
  • Additional work-up especially in severe infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
    • Complete blood count ( anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types and thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia in HUS HUS Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by shiga-like toxin-producing bacteria. Hemolytic Uremic Syndrome)
    • Metabolic panel ( renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome and electrolyte abnormalities in dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration or HUS HUS Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by shiga-like toxin-producing bacteria. Hemolytic Uremic Syndrome)
  • Shigellosis

    Shigellosis (“Shigella dysentery Dysentery Acute inflammation of the intestine associated with infectious diarrhea of various etiologies, generally acquired by eating contaminated food containing toxins, biological derived from bacteria or other microorganisms. Dysentery is characterized initially by watery feces then by bloody mucoid stools. It is often associated with abdominal pain; fever; and dehydration. Gastroenteritis”): Stool sample from a patient with shigellosis ( diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea with bloody stools, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and abdominal cramps Cramps Ion Channel Myopathy). Shigella seen as rods in the smear

    Image: “Shigella stool” by Centers for Disease Control and Prevention Public Health Image Library. License: Public Domain
  • Shigella on hektoen enteric agar

    Shigella on Hektoen enteric (HE) agar: Colonies of S. boydii grown on HE agar have a raised, green, and moist appearance.

    Image: “Shigella boydii 01” by CDC. License: Public Domain

Management

  • Management through oral hydration and electrolyte replacement
  • In high-risk populations ( immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis, malnourished, elderly, children): intravenous fluid replacement
  • Avoid anti-diarrheal medications (e.g., loperamide Loperamide One of the long-acting synthetic antidiarrheals; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally. Antidiarrheal Drugs); may worsen infection
  • Antibiotics:
    • Shortens duration of infection
    • Prevents spread of infection
    • Options: ciprofloxacin Ciprofloxacin A broad-spectrum antimicrobial carboxyfluoroquinoline. Fluoroquinolones, ceftriaxone Ceftriaxone A broad-spectrum cephalosporin antibiotic and cefotaxime derivative with a very long half-life and high penetrability to meninges, eyes and inner ears. Cephalosporins, cefixime
    • For antibiotic-resistant infection: azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides
    • Trimethoprim Trimethoprim The sulfonamides are a class of antimicrobial drugs inhibiting folic acid synthesize in pathogens. The prototypical drug in the class is sulfamethoxazole. Although not technically sulfonamides, trimethoprim, dapsone, and pyrimethamine are also important antimicrobial agents inhibiting folic acid synthesis. The agents are often combined with sulfonamides, resulting in a synergistic effect. Sulfonamides and Trimethoprim– sulfamethoxazole Sulfamethoxazole A bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. Its broad spectrum of activity has been limited by the development of resistance. Sulfonamides and Trimethoprim (TMP-SMX) and ampicillin Ampicillin Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic. Penicillins: 
      • Associated with high resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing in the United States
      • Given if culture shows sensitivity Sensitivity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Blotting Techniques

Prevention

  • Fly control and proper sewage disposal
  • Sanitary measures (water, food, and milk) and proper hygiene
  • Isolation of infected patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • Detection of cases and carriers Carriers The Cell: Cell Membrane, especially food handlers and treatment of infected individuals

Comparison with Salmonella

Shigella and Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella invade the gastrointestinal tract, causing diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea.

Table: Shigella and Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella
Shigella Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella
Gram stain Gram stain Klebsiella/structure Gram-negative bacilli Gram-negative bacilli
Lactose fermentation Non-lactose-fermenting Non-lactose-fermenting
Oxidase Oxidase Neisseria Negative Negative
H2S production No Yes
Motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility No Yes (with flagella Flagella A whiplike motility appendage present on the surface cells. Prokaryote flagella are composed of a protein called flagellin. Bacteria can have a single flagellum, a tuft at one pole, or multiple flagella covering the entire surface. In eukaryotes, flagella are threadlike protoplasmic extensions used to propel flagellates and sperm. Flagella have the same basic structure as cilia but are longer in proportion to the cell bearing them and present in much smaller numbers. Helicobacter)
Virulence factors Virulence factors Those components of an organism that determine its capacity to cause disease but are not required for its viability per se. Two classes have been characterized: toxins, biological and surface adhesion molecules that affect the ability of the microorganism to invade and colonize a host. Haemophilus Endotoxin Endotoxin Toxins closely associated with the living cytoplasm or cell wall of certain microorganisms, which do not readily diffuse into the culture medium, but are released upon lysis of the cells. Proteus, Shiga toxin Shiga toxin A class of toxins that inhibit protein synthesis by blocking the interaction of ribosomal RNA; with peptide elongation factors. They include shiga toxin which is produced by Shigella dysenteriae and a variety of shiga-like toxins that are produced by pathologic strains of Escherichia coli such as Escherichia coli o157. Diarrheagenic E. coli Endotoxin Endotoxin Toxins closely associated with the living cytoplasm or cell wall of certain microorganisms, which do not readily diffuse into the culture medium, but are released upon lysis of the cells. Proteus, Vi capsular antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination
Reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli Humans Humans (S. typhi), animals Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, animalia was one of the kingdoms. Under the modern three domain model, animalia represents one of the many groups in the domain eukaryota. Cell Types: Eukaryotic versus Prokaryotic
Dose to produce disease Small inoculum (acid stable) Large dose (inactivated by acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance)
Infection spread Cell-to-cell (no hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread) Can spread hematogenously

Differential Diagnosis

  • Other infectious Infectious Febrile Infant colitis Colitis Inflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever. Pseudomembranous Colitis: presents with acute-onset fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea. Other causative enteric pathogens include Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella, Campylobacter Campylobacter Campylobacter (“curved bacteria”) is a genus of thermophilic, S-shaped, gram-negative bacilli. There are many species of Campylobacter, with C. jejuni and C. coli most commonly implicated in human disease. Campylobacter, Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli (O157:H7), Yersinia Yersinia Yersinia is a genus of bacteria characterized as gram-negative bacilli that are facultative anaerobic with bipolar staining. There are 2 enteropathogenic species that cause yersiniosis, Y. enterocolitica and Y. pseudotuberculosis. Infections are manifested as pseudoappendicitis or mesenteric lymphadenitis, and enterocolitis. Yersinia spp./Yersiniosis, and Clostridioides difficile. These infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease can be confirmed based on stool cultures Cultures Klebsiella and PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR). Course may be self-limiting Self-Limiting Meningitis in Children or may require antibiotic treatment. 
  • Ulcerative colitis Colitis Inflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever. Pseudomembranous Colitis ( UC UC Ulcerative colitis (UC) is an idiopathic inflammatory condition that involves the mucosal surface of the colon. It is a type of inflammatory bowel disease (IBD), along with Crohn’s disease (CD). The rectum is always involved, and inflammation may extend proximally through the colon. Ulcerative Colitis): a type of inflammatory bowel disease (IBD) characterized by inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy. Disease commonly involves the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation may extend continuously through the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy. Presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor includes bloody diarrhea Bloody diarrhea Diarrhea, abdominal pain Abdominal Pain Acute Abdomen, and tenesmus. Diagnosis is established via endoscopy Endoscopy Procedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body. Gastroesophageal Reflux Disease (GERD) with biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma. Findings include diffuse friability and erosions Erosions Corneal Abrasions, Erosion, and Ulcers with bleeding. 
  • Crohn’s disease: a chronic, recurrent condition causing patchy transmural inflammation Transmural inflammation Crohn’s Disease that can involve any part of the gastrointestinal tract. The terminal ileum Ileum The distal and narrowest portion of the small intestine, between the jejunum and the ileocecal valve of the large intestine. Small Intestine: Anatomy and colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy are usually affected. Disease typically presents with chronic intermittent diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea (bloody or non-bloody) and crampy abdominal pain Abdominal Pain Acute Abdomen. Extraintestinal manifestations may occur. Diagnosis is established based on endoscopy Endoscopy Procedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body. Gastroesophageal Reflux Disease (GERD) and biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma.
  • Celiac disease Celiac disease Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Celiac Disease: a disease associated with IgA IgA Represents 15-20% of the human serum immunoglobulins, mostly as the 4-chain polymer in humans or dimer in other mammals. Secretory iga is the main immunoglobulin in secretions. Immunoglobulins: Types and Functions anti-tissue transglutaminase antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions. Symptoms include abdominal pain Abdominal Pain Acute Abdomen and diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea following gluten Gluten Prolamins in the endosperm of seeds from the triticeae tribe which includes species of wheat; barley; and rye. Celiac Disease consumption. Diagnosis is confirmed based on intestinal biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma demonstrating villous atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation, crypt hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation, and mucosal inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation.

References

  1. Corry, J., Curtis, G., Baird, R. (2003) Progress in industrial microbiology. Elsevier Vol. 37 pp 481-483, https://www.sciencedirect.com/science/article/pii/S0079635203800565?via%3Dihub
  2. Goldberg, M., Calderwood, S., Edwards, M., Bloom, A. (2020) Shigella infection: Epidemiology, microbiology, and pathogenesis. UpToDate. Retrieved 3 Jan 2021 from https://www.uptodate.com/contents/shigella-infection-epidemiology-microbiology-and-pathogenesis
  3. Kroser, J., Singh, A. (2019) Shigellosis. Medscape. Retrieved 5 Jan 2020, from https://emedicine.medscape.com/article/182767-overview#a3
  4. Lucchini, S., Liu, H., Jin, Q., Hinton, J., Yu, J. (2005) Transcriptional adaptation of Shigella flexneri during infection of macrophages and epithelial cells: Insights into the strategies of a cytosolic bacterial pathogen. Infect Immun. 73(1): 88–102.
  5. Mattock, E., Blocker, J. (2017) How do the virulence factors of Shigella work together to cause disease? Front. Cell. Infect. Microbiol. 7:64. doi: 10.3389/fcimb.2017.00064
  6. Riedel S. et al. (Eds.). (2019). Jawetz, Melnick, & Adelberg’s Medical Microbiology, 28e. McGraw-Hill. 
  7. Sansonetti P.J. et al. (Eds.). Harrison’s Principles of Internal Medicine, 20e. McGraw-Hill.
  8. Weddle, E., Agaisse, H. (2018) Principles of intracellular bacterial pathogen spread from cell to cell. Retrieved 3 Jan 2021 from https://doi.org/10.1371/journal.ppat.1007380
© 2021 Lecturio GmbH. All rights reserved.

USMLE™ is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). MCAT is a registered trademark of the Association of American Medical Colleges (AAMC). NCLEX®, NCLEX-RN®, and NCLEX-PN® are registered trademarks of the National Council of State Boards of Nursing, Inc (NCSBN®). None of the trademark holders are endorsed by nor affiliated with Lecturio.

Study on the Go

Lecturio Medical complements your studies with evidence-based learning strategies, video lectures, quiz questions, and more – all combined in one easy-to-use resource.

Learn even more with Lecturio:

Complement your med school studies with Lecturio’s all-in-one study companion, delivered with evidence-based learning strategies.

START NOW FOR FREE

User Reviews

¡Hola!

Esta página está disponible en Español.

Versión en Español

🍪 Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement.

got it
Details