Helicobacter

Helicobacter pylori is a gram-negative bacterium that causes gastric infection. It is the most well known and clinically significant species of Helicobacter. Transmission is believed to occur by ingestion of contaminated food or water; therefore, a higher prevalence of infection is seen in areas with poor sanitation. Certain bacterial features contribute to the pathogenicity of H. pylori: urease production (allowing survival in an acidic environment), motility (permitting movement to the gastric 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), and several toxins (creating local 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). Chronic infection with H. pylori can lead to peptic ulcer disease Peptic ulcer disease Peptic ulcer disease (PUD) refers to the full-thickness ulcerations of duodenal or gastric mucosa. The ulcerations form when exposure to acid and digestive enzymes overcomes mucosal defense mechanisms. The most common etiologies include Helicobacter pylori (H. pylori) infection and prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs). Peptic Ulcer Disease or even gastric cancer Gastric cancer Gastric cancer is the 3rd-most common cause of cancer-related deaths worldwide. The majority of cases are from adenocarcinoma. The modifiable risk factors include Helicobacter pylori infection, smoking, and nitrate-rich diets. Gastric Cancer in severe cases.

Last update:

Table of Contents

Share this concept:

Share on facebook
Share on twitter
Share on linkedin
Share on reddit
Share on email
Share on whatsapp

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: Overview:
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: Overview can be classified according to a lab procedure called Gram staining.
Bacteria with cell walls that have a thin layer of peptidoglycan do not retain the crystal violet stain utilized in Gram staining. 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: Overview do, however, retain the safranin counterstain and thus appear as pinkish-red on the stain, making them gram negative. 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: Overview 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: Overview can be more narrowly identified by growing them on specific media (triple sugar iron (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, oxidase) and their ability to ferment lactose can be tested.
* Stains poorly on Gram stain
** Pleomorphic rod/coccobacillus
*** Require special transport media

Image by Lecturio.

Characteristics

Features:

  • Stains:
    • Gram-negative
    • Detected with silver stain 
  • Morphology:
    • Motile rod
    • Curved shape
    • Contains multiple flagella
  • Growth and culture:
    • Microaerophilic
    • Complex growth requirements (special transport media required)
    • Oxidase-positive, catalase-positive
    • Urease-positive production: creates alkaline environment that permits survival of 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: Overview in acidic mucosa

Helicobacter genus contains about 35 species, with H. pylori being the most well known.

Electron micrograph of helicobacter pylori

Electron micrograph of Helicobacter pylori possessing multiple flagella (negative staining)

Image: “Electron micrograph of helicobacter pylori” by Yutaka Tsutsumi, M.D. License: Public Domain

Related videos

Pathogenesis

Transmission

  • Ubiquitous organism 
  • Humans are the primary reservoir.
  • Acquired by: 
    • Ingestion:
      • Oral–oral transmission: 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: Overview regurgitated with gastric content and temporarily colonize oral cavity
      • Fecal–oral transmission: contaminated food and water supplies (poor sanitation)
    • Person-to-person contact: clusters of infection noted in families
  • Prevalence of infection:
    • Low during childhood
    • 40%–50% in older adults
    • Highest in developing countries
Infection with helicobacter pylori

Infection by Helicobacter pylori via ingestion of a pathogen results in gastric ulcers or gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis.

Image by Lecturio.

Pathogenic features of Helicobacter pylori

  • Urease-positive organism that produces ammonia:
    • Neutralizes gastric acid → hypochloridia → stimulates gastrin production → increased gastric acid → mucosal damage
    • Initial neutralization of gastric acid allows for mucosal colonization.
  • Multiple flagella allow for rapid penetration of the mucosa.
  • Contains mucinase and cytotoxins:
    •  Produces local tissue damage
    • Acts as chemoattractant and activates host inflammatory response 
  • Effects: gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis, development of ulcer(s), gastric carcinoma and gastric MALT lymphomas
Pathogenic features of helicobacter pylori

Pathogenic features of Helicobacter pylori

Image by Lecturio.

Associated Diseases

Gastritis

  • Increased production of 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 acid or damage of the gastric mucosal barrier → irritate the sensitive 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 lining → gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis
  • H. pylori infection is one of the most common etiologies. 
  • May be asymptomatic, or symptoms may include burning abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, dyspepsia, nausea, and vomiting 
  • Management of H. pylori infection: proton pump inhibitors with antibiotics

Gastric and duodenal ulcers

  • Two most common types of peptic ulcers:
    • Gastric ulcers:
      • Located in 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
      • Classically associated with pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain that is worse when eating
    • Duodenal ulcers:
      • Located in the duodenum
      • Typically have improvement in the level of pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain while eating, followed by worsening of pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain after the conclusion of the meal. 
  • Most common etiologies include H. pylori infection and prolonged use of NSAIDs. 
  • Management: 
    • H. pylori eradication (antibiotics and proton pump inhibitors)
    • Eliminating risk factors

Gastric adenocarcinoma

  • Gastric cancer is the formation of malignant neoplasms 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 lining. 
  • Second most common cancer of the GI tract
  • Chronic H. pylori infection: associated with an increased risk of gastric adenocarcinoma

Iron deficiency anemia Iron Deficiency Anemia Iron deficiency anemia is the most common type of anemia worldwide. This form of anemia is caused by insufficient iron due to a decreased supply, an increased loss, or an increased demand. Iron deficiency anemia is seen across all ages, sexes, and socioeconomic strata; however, children, women of childbearing age, and patients from lower socioeconomic strata are at higher risk. Iron Deficiency Anemia and vitamin B12 deficiency

In H. pylori infection:

  • ↓ Absorption of iron in the GI tract is observed, as uptake of iron requires an acidic environment. 
  • Chronic gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis creates inflammatory damage to acid-producing cells → loss of acid production → reduced iron absorption
  • Ongoing 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 likewise leads to loss of parietal cells from which intrinsic factor is produced. 
  • Without intrinsic factor, vitamin B12 deficiency develops.

References

  1. Jensen P. J., Feldman M. (2020). Acute and chronic gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis due to Helicobacter pylori. Retrieved 20 April 2021, from https://www.uptodate.com/contents/acute-and-chronic-gastritis-due-to-helicobacter-pylori
  2. Kusters J. G., van Vliet A. H. M., Kuipers E. J. (2006). Pathogenesis of Helicobacter pylori infection. Clinical Microbiology Reviews 19:449–490.
  3. Riedel S., Hobden J. A., Miller S., et al. (Eds.). (2019). Jawetz, Melnick, & Adelberg’s Medical Microbiology, 28th ed. McGraw-Hill.
  4. Lamont, J. T., Feldman M. (2020). Bacteriology Bacteriology Bacteriology is the branch of microbiology that deals with the morphology, structure, classification, and biochemistry of bacteria. The discipline of bacteriology arose during the 19th century from scientific attempts to prove the "germ theory of disease," namely that diseases were caused by microscopic organisms invading host cells. 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. Management of bacterial disease is generally with antibiotics; however, the choice of antibiotics may vary depending on the bacterial structure and metabolism. Bacteriology: Overview and epidemiology of Helicobacter pylori infection. Retrieved 20 April 2021, from https://www.uptodate.com/contents/bacteriology-and-epidemiology-of-helicobacter-pylori-infection

Learn even more with Lecturio:

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

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.

¡Hola!

Esta página está disponible en Español.

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

Details