Vibrio spp. Aeromonas spp. Campylobacter, and Helicobacter

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  • Vibrio

    • Family Vibrionacceae
    • Asporongenous, gram-negative rods that measure approximately 0.5 to 0.8 m in diameter by 1.4 to 2.6 m, facultative anaerobic, curved or comma-shaped rods
    • Motile, catalase, and oxidase positive
    • Gram negative bacilli, curved or comma-shaped rods, facultative anaerobes, and motile
    • Could have monotrichous flagella or peritrichous
    • Able to reduce nitrate to nitrate except V. metschnikovii
    • Found in marine and surface waters
    • Can grow within a broad temperature range (14-40°C)
    • Halophilic except for V. cholerae and V. mimicus
    • Susceptible to the vibriostatic compound O/129 (2,4 diamino-6,7-diisopropylpteridine)
    • Positive string test – mucoid "stringing" reaction
  • Vibrio cholerae

    • Cause of cholera
    • Curved or Comma-shaped, curved rod 2-4 m long
    • Motile-polar flagellum [monotrichous, peritrichous, lophotrichous]
    • Grows in brackish and marine waters
    • Not part of our normal flora
  • Vibro is known as "rice water stool"
  • Diarrheal fluid loss: >1 L/h
  • Cholera toxin, or choleragen

    • Powerful enterotoxin; virulence factor
    • Heat-labile enterotoxin
    • Once ingested, the bacteria will colonize our small intestine where they'll multiply and produces choleragen
  • Basis of classification or categorization of Vibrio cholerae
    • V. cholerae O1
    • V. cholerae 0139
    • V. cholerae non- O1
  • V. cholerae O1, V. cholerae 0139, V. cholerae non- O1

    Share a common flagellar (H) antigen and somatic (O) antigen
  • V. cholerae O1
    • Ogawa (A,B)
    • Inaba (A,C)
    • Hikojima (A,B,C)
  • V. cholerae O139

    Cause epidemic and pandemic cholera
  • V. cholerae non-O1

    Resemble V. cholerae but fail to agglutinate [does not agree] in O1 antisera
  • Two biotypes of epidemic V. cholerae
    • Classic
    • El tor
  • Classic

    Does not produce hemolysis [chicken RBC]; negative in VPT, and susceptible in polymyxin B
  • El tor

    Produces a hemolysin, gives positive result on the Voges-Proskauer test, and is resistant to polymyxin B
  • Virulence factors of Vibrio cholerae
    • Cholera toxin (CT)
    • zonula occludens (Zot) toxin (enterotoxin)
    • accessory cholera enterotoxin (Ace) toxin
    • O1 and O139 somatic antigens
    • hemolysin/cytotoxins
    • Motility and chemotaxis
    • Mucinase production
  • Zot toxin

    Disrupts the tight junction of our intestinal cells, effectively decreasing tissue resistance
  • Motility and chemotaxis

    Being motile is a virulence factor because it has the capability to be distributed in our body, depending on where the signal of the food or other organisms
  • Mucinase production

    Important in penetration in mucous layers; small intestines can be colonized and infected by V. cholorae toxin coregulated pili (TCP) pili
  • TCP pili

    Provide means for the bacteria to attach to the mucosal cells
  • Vibrio parahaemolyticus

    • Primary cause of so-called summer diarrhea in Japan
    • Haemophilic bacterium
    • Causes acute gastroenteritis after ingestion of contaminated seafood such as raw fish or shellfish
    • Incubation period: 12-24 hours
    • Halophilic requirement: 1% to 8% NaCl
    • Facultative anaerobe, Gram-negative rod
    • Does not grow well on some of the routine differential media used to grow salmonellae and shigellae, but it does grow well on blood agar
    • Grows well on TCBS agar [Thiosulfate Citrate Bile Salt Sucrose] – green colonies (does not ferment sucrose)
  • V. parahaemolyticus serotype O3:K6 = implicated in numerous food-borne outbreaks in various parts of the world
  • TCBS agar
    • pH indicator: Bromthymol Blue
    • Acid: yellow colonies [utilized sucrose]
  • Kanagawa phenomenon

    Heat stable hemolysin produced by V. parahaemolyticus that is able to lyse human erythrocytes [RBC] in a special, high- salt mannitol medium (Wagatsuma agar)
  • Vibrio vulnificus

    • Can utilize/ferment lactose
    • Most vibrios only ferment sucrose
    • Vibrio doesn't only cause gastrointestinal infection, it can also cause septicemia and wound infections
    • Secondary to Vibrio cholerae, this is the second most common organism that causes septicemia
  • Infections caused by Vibrio vulnificus
    • Primary septicemia
    • Wound infections (aquatic wound that often presents as a cellulitis)
  • Treatment of choice for Vibrio vulnificus infections
    Fluroquinolones, third-generation cephalosporins (e.g. ceftriaxone), and doxycycline
  • Vibrio alginolyticus

    • If associated with infections, they are associated in wound infections and eye infections
    • Least pathogenic for humans
    • Strict halophile: requiring at least 1% NaCl
    • Able to tolerate up to 10% NaCl
    • Occupational hazard: people in constant contact with seawater, such as fishermen or sailors
  • Specimen collection for vibrios
    • Stool: inoculated within 2-4 hours of collection onto appropriate agar media
    • For delayed processing: mixed in a Cary-Blair transport medium and refrigerated
  • APW (Alkaline Peptone Water)

    Enrichment medium for vibrios in stool samples
  • Stools are non-sterile [maraming normal flora]. Those normal flora are almost all gram negative bacilli.
  • Buffered glycerol saline

    Not recommended as a transport or holding medium for vibrios
  • Direct microscopic examination of vibrios
    • Gram negative bacilli
    • Dark-field or phase-contrast microscopy
    • "shooting star" motility: V. cholerae O1
  • Culture media for vibrios
    • Nutrient Agar or SBA (0.5% NaCl)
    • MacConkey Agar – non-fermenters
    • Thiosulfate Citrate Bile Salt Sucrose (TCBS) agar
    • Alkaline peptone broth or water, containing 1% NaCl with a pH of 8.5
    • Taurocholate peptone broth (pH, 8.0-9.0)
    • CHROMagar Vibro – V. cholerae, V. parahemolyticus, and V. vulnificus
  • Sucrose-fermenting (yellow colonies) Vibrio species
    • V. cholerae
    • V. alinolyticus
    • V. fluvialis
    • V. furnissil
    • V. cincinnatiensis
    • V. metschnikovii
    • Some V. vulnificus
  • Nonsucrose-fermenting (green) Vibrio species
    • V. mimicus
    • V. parahaemolyticus
    • P. damsela (Photobacterium)
    • Most V. vulnificus strains
  • Not all Vibrio spp. grow on TCBS, especially Grimontia hollisae (formerly Vibrio)
  • Colony appearance of vibrios
    • Medium to large, smooth, opaque, iridescent with a greenish hue
    • V. cholerae, V. fluviasis, and V. mimicus can be beta- hemolytic NLF except V. vulnificus, which may be LF
  • Identification tests for vibrios
    • Oxidase test
    • Nutrient broth with 6% salt – to differentiate V. cholerae, V. mimicus, and Aeromonas spp.
    • String test – to differentiate Vibrio spp. [susceptible] from Aeromonas spp. [resistant]
    • Vibrio static test 0/129 (2,4-diamino-6,7- disopropylpteridine) – to differentiate vibrios (susceptible) from other oxidase positive glucose fermenters (resistant) and to differentiate V. cholerae O1 and non-O1 (susceptible) from other Vibrio spp. (resistant)
  • Aeromonas
    • Enterobacteriaceae family
    • Enteric bacilli
    • Enteric gastrointestinal bacteria
    • Vibrio spp., Aeromonas sp
  • Colony appearance of vibrios
    • Medium to large, smooth, opaque, iridescent with a greenish hue
    • V. cholerae, V. fluviasis, and V. mimicus can be beta- hemolytic NLF except V. vulnificus, which may be LF
  • Identifying gram negative bacilli
    1. Use McConkey agar
    2. Use BAP for gram positive