Helicobacter pylori

• Spiral rod-shaped bacterium; it can appear coccoid in older samples.
• Very common pathogen; present in about half the world’s population.
• Colonization is life-long; introduction often occurs during childhood, though symptoms of infection occur later in adulthood.
• Bacterial carcinogen.
  Pathology
• Gastritis
  – Inflammation of the stomach lining.
  – Inflammation can be localized or widespread, and can affect the duodenum.
  – Neutrophils infiltrate the mucosa.
• Peptic ulcers
  – Bacteria erode the mucosal lining of the stomach and/or duodenal.
• Gastric adenocarcinoma
  – Associated with chronic, widespread inflammation.
  – Mucosal tissue is replaced by fibrous tissue and intestinal–type epithelium.
• Gastric mucosa-associated lymphoid tissue B-cell lymphomas
  – B-cells migrate to the stomach mucosa and establish lymphomas.

Campylobacter

• Common causes of bacterial gastroenteritis.
  – Also cause extra-intestinal infections.
• Spiral rod-shaped but may appear coccoid in older specimens.
• Campylobacter jejuni
  – Distinct histopathology, with ulcerated and bloody villi, white blood cell infiltration, and the formation of abscesses in the intestinal glands and crypts.
• In some individuals, Campylobacter jejuni infection triggers immune-mediated disorders.
  – Guillain-Barré syndrome occurs when the immune system targets the peripheral nervous system.
  Patients experience tingling and ascending weakness; ultimately, impairment of inspiratory muscles can lead to respiratory failure.
  – Reactive arthritis is characterized by joint pain and swelling.

Vibrio cholerae and Vibrio parahaemolyticus

Vibrio parahaemolyticus is also associated with wound infections.

• Consumed in contaminated food or water.
• Gastroenteritis caused by Vibrio species is characterized by watery diarrhea, cramps, vomiting, and nausea.
• Choleara
  – Two strains of Vibrio cholerae are associated with cholera, which is a severe gastroenteritis that produces profuse watery diarrhea (sometimes referred to as “rice water” diarrhea).
  – If untreated, Cholera can lead to fatal dehydration.