Campylobacter, Helicobacter, and Vibrio Species

Campylobacter, Helicobacter, and Vibrio Species

Overview of Lecture Topics

  • Covering the bacterial genera: Campylobacter, Helicobacter, and Vibrio.

  • All organisms discussed are major causative agents for diarrheal diseases and various infections.

Campylobacter Species

  • Primary species of concern: Campylobacter jejuni and Campylobacter fetus.

  • General characteristics:

    • Many species of Campylobacter are pathogenic.

    • Zoonotic transmission: Spread through direct contact with infected animals, primarily poultry.

    • Causes diarrheal disease, but also associated with infections in immunocompromised individuals.

Campylobacter jejuni

  • Known for causing the most common diarrheal illness worldwide.

  • Presents symptoms of:

    • Diarrhea with mild abdominal pain.

    • Cramps and bloody diarrhea.

    • Less common: fever and chills, rarely nausea or vomiting.

    • Symptoms are usually self-limiting, resolving within 2 to 6 days.

  • Transmission routes include:

    • Raw milk, improperly cooked poultry, and contaminated water.

    • Does not multiply in food; unlike Salmonella or Staphylococcus.

Campylobacter fetus

  • Significant for causing abortions in domestic animals (cattle, sheep, pigs).

  • Noticeable isolation from blood cultures, especially in immunocompromised or older adult patients.

Post-Infection Complications

  • Reactive arthritis and Guillain-Barre syndrome:

    • Approximately 20-40% of Guillain-Barre syndrome patients had a Campylobacter jejuni infection 1-3 weeks prior to onset.

Specimen Collection

  • Common specimens include:

    • Stool samples (use Cary Blair transport medium if delayed).

    • Rectal swabs (risk of contamination, less preferred).

Cultivating Campylobacter

  • Requires specialized media such as:

    • Campi blood agar: Brucella agar base with 10% sheep blood and antimicrobials.

    • Skeros blood agar, CVA agar.

  • Growth conditions:

    • Microaerophilic environment: Requires 5% oxygen.

    • Optimal growth temperature: 42°C.

    • Colony Morphology: Moist, spreading, non-hemolytic colonies.

Identification of Campylobacter Species
Campylobacter jejuni:

  • Colony morphology notable for runny, moist appearance.

  • Characteristic growth conditions and tests:

    • Growth at 37°C and 42°C.

    • Oxidase positive, sodium hypurate positive, nalidixic acid sensitive, cephalothin resistant.

Campylobacter fetus:

  • Similar morphology but grows at 25°C (not at 42°C).

  • Key tests:

    • Oxidase positive, sodium hypurate negative, nalidixic acid resistant, cephalothin sensitive.

Summary Table for Campylobacter Identification

  • Species | Growth Temp | Primary Isolation Source | Sodium Hypurate | Nalidixic Acid | Cephalothin

  • Campylobacter jejuni | 37/42°C | Stool | Positive | Sensitive | Resistant

  • Campylobacter fetus | 25°C | Blood | Negative | Resistant | Sensitive

Helicobacter Species

  • Unique characteristics:

    • Curved, helical, spiral, or fusiform gram-negative rods.

    • Microaerophilic; produces urease.

Importance of Urease

  • Urease hydrolyzes urea to form ammonia, which increases pH around the infection site, providing protection from gastric acidity.

  • Unique motility allows the organism to penetrate gastric mucosa.

Helicobacter pylori

  • Known to colonize the stomach causing:

    • Low grade inflammatory processes.

    • Associated with gastritis and peptic ulcers.

  • Immune response: Antibodies produced are not protective against the organism.

Identification Techniques

  • Techniques for identification include:

    • Biopsy placed in urea broths or commercial urease kits (CLO test).

    • Urea Breath Test: Patient ingests radioactive urea; presence of H. pylori detected by breakdown of urea leading to release of radioactive carbon dioxide in breath.

    • Culture on specialized media (chocolate agar, brucella).

  • Time for growth detection can take up to 7 days.

Treatment of Helicobacter pylori

  • Common treatment protocol includes:

    • Triple Drug Therapy: Metronidazole, bismuth salt, and amoxicillin or tetracycline.

  • Treatment duration: 1-2 weeks; challenge with patient compliance.

Vibrio Species

  • Characteristics: Gram-negative organism, curved appearance, oxidase positive; primarily found in saltwater.

  • Halophilic nature: Grows well in environments with high salt concentrations.

  • Common routes of transmission: Exposure or ingestion of infected water or seafood.

Vibrio cholerae

  • Major groups include:

    • O1 (causes cholera), non-O1 (milder disease).

  • Cholera epidemics:

    • Historical pandemics since 1817; mostly asymptomatic infections

Cholera Symptoms and Effects

  • Profuse watery diarrhea termed rice water stool;

    • Patients may exhibit dehydration, hypovolemic shock, metabolic acidosis.

  • Bowel movements can be up to 30 times daily.

    • Death can occur rapidly if dehydration not managed effectively.

Treatment for Cholera

  1. Rehydration: Oral or IV fluids to restore hydration.

  2. Antibiotic therapy to reduce bacterial load (not primary treatment).

Isolation and Cultivation of Vibrio

  • Stool samples collected in Cary Blair medium.

  • Special media for culturing:

    • Thiosulfate citrate bile salt sucrose (TCBS) agar (high pH of 8.5-9.5).

    • Color differential:

    • Sucrose fermenters: Yellow colonies.

    • Non-sucrose fermenters: Green colonies.

Additional Identification Tests

  • Historically used string test: Positive when noting string formation after emulsifying in sodium desoxycholate.

  • Treatment challenges: Monitor resistance, particularly to tetracyclines.