Vibrio and Aeromonas

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Vibrio and Aeromonas

• Gram-negative
• Falcultatively anaerobic
• Fermentative rods
• Positive oxidase reaction
• Polar flagella

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Vibrio

• Curved rods
• V. cholerae, V. parahaemolyticus, V. vulnificus

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Physiology and Structure

• Cultivation
• Simple nutrition requirement
• Broad Tem. Range (14oC 40oC)
• Require Salt for growth
• Wide range of pH (pH6.5 9.0) susceptible to
  stomach acids

• Structure
• polar flagella (mobility)
• toxin co-regulated pilus (virulence)
• LPS lipid A (endotoxin), core polysaccharide, O
  polysaccharide
• O polysaccharide (serogroups)
• V. cholerae 140 serogroups (O1-O140)
• - O1, O139 produce chorela
  toxin associated with endemics
• - O1 three serotypes Inaba,
  Ogawa, Hikojima (can shift)
• V. parahaemolyticus 13 O serogroups
• V. vulnificus 7 O serogroups
• Polysaccharide capsules V. vulnificus, non-O1
  V. chorelae
• V. chorelae O1 no capsule do not spread

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Pathogenesis and Immunity
Table 31-2. Virulence Factors of Vibrio Species
Species Virulence Factor Biologic Effect
V. cholerae Cholera toxin Hypersecretion of electrolytes and water
V. cholerae Toxin co-regulated pilus Binding site for CTXF mediates adherence to intestinal mucosal cells
V. cholerae Chemotaxis protein Adhesin factor
Accessory cholera enterotoxin Increases intestinal fluid secretion
Zonula occludens toxin Increases intestinal permeability
Neuraminidase Modifies cell surface to increase GM1 binding sites for cholera toxin
V. parahaemolyticus Kanagawa hemolysin Enterotoxin that induces chloride ion secretion (watery diarrhea)
V. vulnificus Polysaccharide capsule Antiphagocytic
  Cytolysins, proteases, collagenase Mediates tissue destruction

• Cholerae toxin
• Complex A-B toxin
• B subunit ganglioside GM1 receptors
  (intestinal epithelial cells)
• A subunit G proteins (ADP-ribosylation) ?
  adenylate cyclase ? cAMP
• hypersecretion of water and electrocytes

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Cholera -therapy

• massive secretion of ions/water into
• gut lumen

• dehydration and death

• therapy
• fluid and electrolyte replacement
• antibiotic therapy (Azithromycin)

• vaccination
• partially effective
• not generally used
• international travelers

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Aeromonas

• Gram-negative, facultatively anaerobic
  fermentative rod
• Human pathogens
• A. hydrophila, A. caviae, A. veronii
• Diarrheal disease
• Wound infections
• Opportunistic systemic disease
• Ingestion of contaminated water or food
• Ciprofloxacin