bacteriology lecture endterm

• Vibrio spp.


  • Ubiquitous curved gram-negative rod, non-sporeformer, motile with monotrichous flagella
  • Oxidase positive
  • Growth is stimulated in presence of salt (halophilic) except for V. cholerae and V. mimicus

  
• Vibrio cholerae


  • Salt requirement: Halophilic, Nonhalophilic
  • Serogroup (O1, O139, Non-O1/O139)
  • V. cholerae O1 serotype: Inaba - Philippines, Ogawa - India, Hikojima - Japan
  • V. cholerae O1 biotype: Classical, El Tor

  
• Vibrio cholerae O1 is the causative agent of cholera

  
• Vibrio cholerae O1


  • Virulence factors: cholera toxin (choleragen), Zonula occludens toxin, Toxin coregulated pili
  • "rice watery stool"
  • Mode of transmission: ingestion of contaminated water or food

  
• Laboratory Diagnosis of Vibrio cholerae

  1. Direct microscopy: "fish in stream"

  2. Culture: Enrichment broth - APW, Translucent colonies on MAC, Yellow colonies on TCBS

  3. Biochemical ID: Catalase and oxidase positive, String test positive

  
• Vibrio parahaemolyticus


  • First reported in Japan to cause large food poisoning outbreak ("Summer diarrhea")
  • Virulence: polysaccharide capsule, urease enzyme (in few strains)
  • TCBS: green colonies (sucrose NF)
  • Swarming on BAP
  • Associated with "Kanagawa phenomenon"

  
• V. vulnificus


  • Wound infections and septicemia; involvement in gastroenteritis is uncertain
  • Lactose fermenter

  
• V. alginolyticus


  • Ear infections, wound infections; rare cause of septicemia
  • Transmitted via exposure of wound to contaminated water
• Aeromonas spp.


  • Ubiquitous, oxidase-positive, glucose-fermenting, gram-negative rods
  • Gastroenteritis, wound infections, bacteremia, HUS (Shiga-like toxin)
  • Causes: Red leg disease in frogs
  • Growth is not stimulated by NaCl
  • BAP: large, round, raised, opaque, beta hemolytic colonies
• Campylobacter spp.


  • Motile (monotrichous), nonsporing, microaerophilic, curved gram-negative rods; S-shape/ Sea-gull's wing
  • Man: Diarrhea and gastroenteritis (C. jejuni, C. coli, C. upsaliensis, C. lari, C. hyointestinalis)
  • Animal: C. fetus - abortion
  • Triggers the pathogenesis of various other diseases such as: Guillain-Barre syndrome (C. jejuni O19), Alpha chain disease
  • Mode of transmission: ingestion of animal products, direct contact with infected household pets, sexual contact
• Laboratory Diagnosis of Campylobacter spp.

  1. 42-43°C (optimum temperature)

  2. Direct microscopy: Dark ground microscopy demonstrates the darting motility of the bacilli

  3. Culture: 42-43°C (optimum temp.), Skirrow's medium, Butzler medium, Campy BAP, CCDA (Charcoal Cefoperazone Deoxycholate Agar)

  
• Helicobacter pylori


  • Curved/helical/spiral, motile, microaerophilic gram-negative rod
  • Colonizes stomach and is associated with peptic ulcer disease and gastric carcinoma
  • Catalase, urease and oxidase positive
  • Culture: CHOC/ Brucella agar w/ 5% sheep's blood + Wilkins Chalgren agar/ Skirrow