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 Escape With constant immune mechanisms holding unstable tumor cells in equilibrium, tumor-cell variants may emerge. These cancer cells may express fewer antigens on their surfaces or lose their MHC class I expression.Variants may also protect themselves from T-cell attack via expression of IC molecules on their surfaces, like normal cells.Creation of an immunosuppressive state in the microenvironment is another way to grow without immunologic interference. Cancer Immunotherapy the GI tract, infecting the urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as 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. E. coli is transmitted via a fecal–oral route, which can occur with unsanitary food preparation, contamination of meat or produce by manure, irrigating or washing crops/fruits with contaminated water, and consumption of contaminated water.
Last updated: 31 Mar, 2022
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
Bacilli
Shigella, 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
Triple sugar iron
Shigella (
TSI
TSI
Shigella) 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
Photomicrograph of Escherichia coli
Image: “E. coli 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” by NIAID. License: CC BY 2.0Pathogen | Pathogenesis/ 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 factor | Signs and Symptoms |
---|---|---|
ETEC |
|
No 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 or invasion → traveler’s 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 (watery) |
EPEC |
|
Mild 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 → watery diarrhea Watery diarrhea Rotavirus with mucus |
EAEC |
|
Mild 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 → watery diarrhea Watery diarrhea Rotavirus |
EHEC |
|
Severe 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 → 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 ( bloody diarrhea Bloody diarrhea Diarrhea) |
EIEC | Direct invasion of the intestinal 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 and formation of enterotoxins → necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage 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 | Severe 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 → 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 ( bloody diarrhea Bloody diarrhea Diarrhea) similar to Shigella Shigella Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir. Shigella |
ETEC attaches via colonization Colonization Bacteriology factor antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination or CFA ( adhesion Adhesion The process whereby platelets adhere to something other than platelets, e.g., collagen; basement membrane; microfibrils; or other ‘foreign’ surfaces. Coagulation Studies). The heat Heat Inflammation stable (ST) enterotoxin Enterotoxin Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc. ; most common enterotoxins are produced by bacteria. Diarrhea causes cGMP cGMP Guanosine cyclic 3. Phosphodiesterase Inhibitors accumulation in cells, and secretion Secretion Coagulation Studies of fluid and electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes into the intestinal lumen. The heat Heat Inflammation labile (LT) enterotoxin Enterotoxin Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc. ; most common enterotoxins are produced by bacteria. Diarrhea acts like cholera Cholera An acute diarrheal disease endemic in india and southeast Asia whose causative agent is Vibrio cholerae. This condition can lead to severe dehydration in a matter of hours unless quickly treated. Vibrio toxin, which increases cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors by activating adenylyl cyclase (AC). General effect is water and chloride Chloride Inorganic compounds derived from hydrochloric acid that contain the Cl- ion. Electrolytes hypersecretion and inhibited sodium reabsorption Sodium reabsorption Tubular System. Non-invasive enterotoxins remain within the intestinal lumen and do not invade the epithelial cells.
Image by Lecturio.EPEC Pathogenesis:
EPEC uses intimin
adhesion
Adhesion
The process whereby platelets adhere to something other than platelets, e.g., collagen; basement membrane; microfibrils; or other ‘foreign’ surfaces.
Coagulation Studies molecules to adhere to the intestinal cells. Binding causes cell deformation (
brush border
Brush border
Tubular System degeneration and loss of microvilli).The characteristic effect of
attachment
Attachment
The binding of virus particles to virus receptors on the host cell surface, facilitating virus entry into the cell.
Virology and effacement is thought to be the primary cause of
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.