Enterobacter Cloacae

• Gram negative rod
• Generally a nosocomial pathogen, responsible for various infections, including bacteremia, lower respiratory tract infections, skin and soft-tissue infections, UTIs, endocarditis, intra-abdominal infections, septic arthritis and osteomyelitis
• Risk factors for infection include hsoptialization within previous 2 weeks, invasive procedures within 72 hrs, CVCs, hepatobiliary disease, solid organ or hematologic malignancy
• Enterobacter species contain a subpopulation of organisms that produce a beta-lactamase at low-levels-- Once exposed to broad-spectrum cephalosporins, the subpopulation of beta-lactamase–producing organisms can predominate. Thus, an Enterobacter infection that appears sensitive to cephalosporins at diagnosis may quickly develop into a resistant infection during therapy. Carbapenems and cefepime have a more stable beta-lactam ring against the lactamase produced by resistant strains of Enterobacter.
• Best abx choices: carbapenems, fourth-generation cephalosporins, aminoglycosides, fluoroquinolones, and TMP-SMZ
• First-generation and second-generation cephalosporins are inactive against Enterobacter infections.
• Third-generation cephalosporins frequently show good in vitro activity against Enterobacter, but, as explained above, there is a significant risk of developing full resistance during therapy (resistance develops much less frequently with fourth-generation cephalosporins because they are relatively stable to AmpC beta-lactamase)

(Victoria Kelly MD, 9/24/10)