Alcaligenes spp

• A. aquatilis
• A. faecalis

Gram Stain

• Gram negative bacilli / coccobacilli - nonfermenter (aerobic)

Clinical Significance

Many previous Alcaligenes species now belong to Achromobacter species. These organisms are found in the environment and may colonize the skin, ear, and gastrointestinal tracts (especially of hospitalized patients).

Contamination of hospital environments, equipment, or fluids may result in nosocomial infections / pseudoinfections. They are often found in mixed cultures and have been associated with bacteremia (post-surgical or post-chemotherapy), endocarditis, endophthalmitis, chronic otitis, pyelonephritis, peritonitis, pancreatic abscesses, osteomyelitis (following trauma) and respiratory infections in cystic fibrosis patients  (possible patient to patient transmission).

They can cause skin/soft tissue infections in patients with severe peripheral vascular disease.

Usual Susceptibility Pattern

These organisms are resistant to amoxicillin, and 1st/2nd generation cephalosporins but typically susceptible to aminoglycosides, quinolones, TMP/SMX, and carbapenems. Third generation cephalosporin susceptibility is variable as some strains produce an extended spectrum beta-lactamase.

Although they display in vitro susceptibility to beta-lactamase inhibitor combination drugs, clinical efficacy is uncertain.