Ch. 23 - Vibrio, Campylobacter and Helicobacter

Vibrio cholerae General characteristics

• Shares many characteristics with Enteric bacteria

• Salt water and freshwater.

• Warm season and poor sanitation

• Undercooked seafood

V. cholerae Microscopic and colony morph

• Comma shaped gram-negative rods

• Shooting star motility in fresh stool

V. cholerae Key Biochemical test:

– String test: 7 mm using 0.5% sodium deoxycholate

– Serology: O1 and O139 antisera

V. cholerae Pathogenesis, Epidemiology, and Disease:

• Cholera:

• “Rice-water stool” is characteristic

• Most important virulence factor is cholera toxin

  • Causes severe loss of fluid and electrolytes

• Rapid dehydration, metabolic acidosis, and shock can occur cardiovascular collapse

• Must rapidly replace fluids and electrolytes then treat with antibiotics

• High mortality if left untreated

V. cholerae Diagnosis

Usually based on characteristic diarrhea

V. cholerae Treatment

• Fluid and electrolyte replacement

• Antimicrobial drugs can reduce exotoxin production and the volume of diarrhea

V. cholerae Prevention

• Proper sewage and water treatment can prevent epidemics

• Oral vaccine provides some protection

Vibrio parahaemolyticus General characteristics

• Warm ocean water

• Raw or undercooked seafood

• Results from ingestion of shellfish

V. parahaemolyticus Colony morph

Thiosulphate citrate bile salt sucrose agar

V. parahaemolyticus Biochemical characteristics

• Halotolerance: requires 1.0% NaCl for growth

• String test: shorter than 3 mm

V. parahaemolyticus Disease

• Causes cholera-like Gastroenteritis Infections in open wound exposed to contaminated water or seafood

• Septicemia in immunocompromised individuals

Vibrio vulnificus Environment:

warm ocean water

V. vulnificus Clinical significance:

• Healthy individuals: gastroenteritis

• Caused by consumption of contaminated shellfish

• Immunocompromised individuals especially with liver disease

  • Aggressive tissue infections

  • Septicemia

Campylobacter jujeni gen characteristics

• Likely most common cause of gastroenteritis in the United States

• Many animals serve as reservoirs for the bacteria

• Humans infected by consuming contaminated food, milk, or water

  • Poultry is the most common source of infection

• Infections produce self-limiting bloody and frequent diarrhea

• Proper food handling and preparation can reduce spread of bacteria

• Microaerophilic and capnophilic atmosphere requirements

C. jujeni Micro morph

• Characteristic gram stain.

• The loose spirals (squiggles) or S shapes are easily recognized by the experienced microbiologist.

C. jujeni colony morph

• Special media

  • Selective

  • Enrichment

• Grows on selective Blood Agar media.

• Microaerophilic, capnophilic atmosphere at 42C.

• Can inhibit normal enteric bacteria to grow while allowing Campylobacter jejuni to proliferate

C. jujeni Biochemical characteristics:

• Oxidase

• Catalase

• Indoxyl acetate

• Molecular and immunologic tests

C. jujeni Virulence

Produces Enterotoxin and cytotoxins

C. jujeni Diseases

Diarrhea and Guillain-Barré syndrome

Helicobacter pylori Gen characterisitics

• Slightly helical, motile bacterium

• Colonizes stomach of its hosts

• Ingestion of bacteria from contaminated hands, well water, or fomites

• Causes gastritis and most peptic ulcers

• Presence of H. pylori can be demonstrated by positive urease test

• Biochemical tests provide a definitive identification

H. pylori’s Numerous virulence factors enable it to colonize the stomach:

1) Proteins that inhibit production of stomach acid

2) Flagella help the bacteria burrow through the stomach lining

3) Adhesins facilitate binding to gastric cells

4) Urease enzymes that help neutralize stomach acid

H. pylori Symptoms

• Belching

• Unpleasant taste in the mouth

• Loss of appetite

• Nausea

• Stomach Fullness

• Bleeding gums

• Pain in the stomach

H. pylori Diseases

• Stomach Ulcer

• Duodenal Ulcer

• Gastritis

• Stomach Cancer

• Duodenitis

• Esophagitis and Heartburn

• Gastroduodenitis

H. pylori Treatment:

Treat with antimicrobial drugs and drugs that inhibit acid

production

H. pylori Prevention:

• Good hygiene

• Adequate sewage treatment

• Proper food handling