Aeromonas spp

• A. bestiarum
• A. caviae
• A. hydrophila
• A. jandaei
• A. media
• A. popoffii
• A. schuberti
• A. veronii biovar sobria
• A. veronii biovar veronii
  
  Note - other species have been isolated from human specimens but are not thought to be pathogenic

Gram Stain

• Gram negative coccobacilli/bacilli straight with rounded ends (singly, in pairs or short chains)-fermenter (facultative anaerobic)

Clinical Significance

These organisms are found in water sources (fresh/marine) as well as various food sources.

They are associated with gastroenteritis (mild to severe), especially in summer months. Infections are typically self-limited. It may present as a severe cholera like illness in patients with hepatobiliary disease and/or immunosuppression. The infection can progress to bacteremia, septicemia, or hemolytic uremic syndrome

Aeromonas spp are also associated with various extraintestinal infections including skin and soft tissue infections (cellulitis, myonecrosis, echthyma gangrenosa, and wound infections related to leech therapy), bone and joint infections, pneumonia, ophthalmic infections, and septicemia. Infections may occur secondary to intestinal infections or following injury/contact with contaminated water.

Usual Susceptibility Pattern

These organisms are resistant to ampicillin and 1st/2nd cephalosporins.

They produce a variety of beta-lactamases including cephalosporinases and carbapenemases (inducible in A. hydrophila and A. caviae) that may not be easy to detect in vitro.

They are usually susceptible to quinolones, tetracyclines, TMP/SMX, and aminoglycosides.