Vibrio, Campylobacter, and Helicobacter

Vibrio cholerae

• Not part of the Enterobacteriaceae, but associated with gastrointestinal issues.
• Causative agent of cholera, a frank pathogen.
• Spread via the fecal-oral route.
• Causes a serious diarrheal disease.
• Historically caused global pandemics; still prevalent in areas with natural disasters or refugee situations.
• Treatable today, but historically was not.
• Gram-negative, curved rod (banana-shaped).
• Small and motile.
• Does not produce endospores.
• Produces an AB toxin, the primary virulence factor.
  • Without the toxin, the organism cannot cause human disease.
  • Other Vibrio members exist in marine samples but are not pathogenic without virulence factors.
• Mechanism of Action:
  • Organism replicates in the intestinal tract and produces AB toxin.
  • The exotoxin is released and can enter the bloodstream.
  • B portion opens channels in host cell membranes.
  • A portion enters the host cell and disrupts chloride ion balance.
  • Water flows out of the host cell, leading to profuse watery diarrhea.
• Host cells along the intestinal tract lose water and may undergo plasmoptysis (shrinkage due to water loss) and die.
• The water and sloughed-off host cells result in rice water stool, a characteristic symptom. No other organism is known to cause this specific symptom.
• The toxin initially acts in the intestinal tract, then moves into the bloodstream and affects other host cells.
• Extreme dehydration results from the toxin's effects, with individuals potentially losing 20-30 liters of fluid a day.
• Dehydration impairs tissue function, including the heart.
• Blood becomes thick and viscous due to water loss, making it difficult for the heart to pump.
• Death typically results from heart failure due to dehydration and the heart's inability to pump the thickened blood.
• Highly contagious; historically transmitted through personal belongings of those who died from cholera.
• Treatment includes cholera antitoxin and antibiotics to prevent new cholera cells from forming.
• More prevalent in developing nations with poor water quality and sanitation or after natural disasters.
• With proper medical intervention, complete recovery is possible.
• John Snow and the London Cholera Outbreak (Historical Context):
  • John Snow was a British physician in the mid-1800s.
  • He used ether as anesthesia during childbirth.
  • During a cholera outbreak in London in the 1850s, he advised people to leave the city but stayed to investigate.
  • Created the "ghost map," which showed cholera cases were centered in one area with a central well in Golden Square.
  • He went door-to-door to track cases and water sources.
  • Concluded that the well in the center of Golden Square was the source of the outbreak.
  • The pump handle was removed to prevent water access, but people protested.
  • People didn't understand how something in the water could cause illness.
  • Fecal contamination of the water supply was the cause.
  • Homes had cesspits (unfinished earthen chambers) for waste collection, which often overflowed due to more tenement style living.
  • High heels became fashionable due to people needing to walk from the house to the outhouse without getting waste all over their feet.
  • John Snow is considered the first epidemiologist for tracking the outbreak.
• Different water companies in London: One company collected water directly from the Thames River in London without treatment, while another collected it from outside of London and filtered it by coarse gravel, fine gravel, coarse sand, then fine sand. The company filtering their water had very few cases. John Snow speculated this removed microbes.
• Modern Water Treatment: Today, the process involves coarse gravel, fine gravel, coarse sand, and fine sand filtration, plus chlorination.
  • In Chicago, water is taken from Lake Michigan far offshore to avoid human impact from the shoreline.

Campylobacter jejuni

• Identified in the 1980s, a relatively recent discovery in microbiology.
• A frank pathogen that causes diarrheal disease.
• Normal flora in domesticated animals, especially livestock.
• Common source of infection is poultry.
• Can be contracted from unpasteurized dairy products (goat milk) and non-chlorinated surface waters.
• Outbreaks have occurred in public pools that were not properly chlorinated.
• Gram-negative, curved rod.
• Non-spore former.
• Easily enters water supplies.
• Found in dogs, cats, and birds.
• Transmission via:
  • Ingesting contaminated food or liquids.
  • Fecal-oral route.
  • Person-to-person contact.
• Requires a very small number of cells (500 or fewer) to cause disease.
• Survives the stomach and enters the intestinal tract, generating symptoms.
• Disease is more common in young children and young adults (20-29 age group).
  • Younger individuals are more adventurous and risk-taking in food and beverage choices.
• Incubation period of 2-10 days.
• Symptoms:
  • Begins as simple diarrhea, quickly progressing to bloody diarrhea with abdominal cramping.
  • Fever is not typically present.
• Duration is usually 2-6 days.
• Self-limiting, but often treated with antibiotics.
• Less prevalent in the U.S. due to changes in drinking water supply processes to prevent animal waste contamination.
• Common in areas where animal waste can enter the drinking water supply.
• Invasive: causes bloody diarrhea.

Helicobacter pylori

• Rod-shaped, spiral-shaped bacteria.
• Moves via corkscrew motion, aided by flagella.
• Causes gastric and duodenal ulcers, and sometimes diarrhea, nausea, vomiting, or constipation.
• Diagnosis is typically made when someone has an ulcer.
• Ulcers are open wounds in the stomach or duodenum, causing stomach or chest pain.
• Disrupts the body's protective mechanisms.
• Mechanism:
  • Corkscrews through the thick mucus layer of the stomach.
  • Turns off mucus production.
  • Stomach acid wears away the mucus layer, exposing the stomach wall.
  • Ulcers are essentially acid burns in the stomach.
• Discovered and linked to disease in the 1980s.
• Historical Context:
  • Before discovery, ulcers were believed to be caused by stress and treated with counseling.
  • Now treated with antibiotics (often requiring multiple attempts).
  • Infection can return even after treatment.
• Opportunistic Pathogen:
  • Estimated that 80% of people have been exposed by their fifties.
  • Only 20% develop an infection.
• Transmission:
  • Food and beverages, especially unpasteurized dairy products.
  • Considered ubiquitous.
• Leading cause of gastric and duodenal ulcers.
• Link to Cancer:
  • Does not directly cause cancer, but changes the host's physiology.
  • 80% of stomach cancer patients have a history of ulcers.
  • Mechanism of the link is not well understood.
• Treatment involves antibiotics.
• Stomach ulcers have less than a 5% survival rate.
• Yearly upper GI tests with biopsies are recommended for individuals with a history of ulcers.