Enterobacter cloacae complex

Gram Stain

• Gram negative bacilli - fermenter

Clinical Significance

These organisms are widely distributed in the environment (water, soil and vegetation). They are opportunistic pathogens that rarely cause infection in healthy individuals but can be associated with serious infections in immunocompromised patients. 

They are frequent colonizers of the gastrointestinal tract of hospitalized patients, especially those who have received broad spectrum antibiotics.

They are associated with nosocomial infections, including respiratory, urinary tract, skin/soft tissue (especially ulcers and burn wounds) and bone/joint infections, meningitis, endocarditis, and bacteremia. 

Bacteremias are often polymicrobial.

Usual Susceptibility Pattern

These organisms produce an inducible cephalosporinase (AmpC) rendering them resistant to ampicillin  and 1st/2nd generation cephalosporins.  Therapy with 3rd generation cephalosporins is not recommended as clinical failures can occur despite in vitro susceptibility. 

Beta-lactamase inhibitor combinations are not recommended as the cephalosporinase is not inhibited by the beta-lactamase inhibitor.

They are typically susceptible to ciprofloxacin, aminoglycosides, and carbapenems (meropenem has better activity than imipenem).  Some strains of E. cloacae produce a chromosomal carbapenemase.

Susceptibility to TMP/SMX is variable.

They are predictably resistant to fosfomycin.

They are resistant to nitrofurantoin.