Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy.

OBJECTIVES

To study the effect of previously administered antibiotics on the antibiotic susceptibility profile of Enterobacter, the factors affecting mortality, and the emergence of antibiotic resistance during therapy for Enterobacter bacteremia.

DESIGN

Prospective, observational study of consecutive patients with Enterobacter bacteremia.

SETTING

Three university tertiary care centers, one major university-affiliated hospital, and two university-affiliated Veterans Affairs medical centers.

PATIENTS

A total of 129 adult patients were studied.

MEASUREMENTS

The two main end points were emergence of resistance during antibiotic therapy and death.

MAIN RESULTS

Previous administration of third-generation cephalosporins was more likely to be associated with multiresistant Enterobacter isolates in an initial, positive blood culture (22 of 32, 69%) than was administration of antibiotics that did not include a third-generation cephalosporin (14 of 71, 20%; P less than 0.001). Isolation of multiresistant Enterobacter sp. in the initial blood culture was associated with a higher mortality rate (12 of 37, 32%) than was isolation of a more sensitive Enterobacter sp. (14 of 92, 15%; P = 0.03). Emergence of resistance to third-generation cephalosporin therapy (6 of 31, 19%) occurred more often than did emergence of resistance to aminoglycoside (1 of 89, 0.01%; P = 0.001) or other beta-lactam (0 of 50; P = 0.002) therapy.

CONCLUSIONS

More judicious use of third-generation cephalosporins may decrease the incidence of nosocomial multiresistant Enterobacter spp., which in turn may result in a lower mortality for Enterobacter bacteremia. When Enterobacter organisms are isolated from blood, it may be prudent to avoid third-generation cephalosporin therapy regardless of in-vitro susceptibility.