Chloramphenicol resistance in vancomycin-resistant enterococcal bacteremia: impact of prior fluoroquinolone use?
OBJECTIVE
The prevalence of vancomycin-resistant enterococci (VRE) has increased markedly during the past decade. Few data exist regarding the epidemiology of resistance of VRE to chloramphenicol, one of the few therapeutic options.


METHODS
Survey and case-control study.


METHODS
A 725-bed, tertiary-care academic medical center and a 344-bed urban community hospital.


METHODS
Hospitalized patients with blood cultures demonstrating VRE.


METHODS
We examined the trends in the prevalence of chloramphenicol resistance in VRE blood isolates at our institution from 1991 through 2002 and conducted a case-control study to identify risk factors for chloramphenicol resistance among these isolates.


RESULTS
From 1991 through 2002, the annual prevalence of chloramphenicol-resistant VRE increased from 0% to 12% (P < .001, chi-square test for trend). Twenty-two case-patients with chloramphenicol-resistant VRE bloodstream isolates were compared with 79 randomly selected control-patients with chloramphenicol-susceptible VRE. Independent risk factors for chloramphenicol-resistant VRE were prior chloramphenicol use (odds ratio [OR], 10.9; 95% confidence interval [CI95], 1.72-68.91; P = .01) and prior fluoroquinolone use (OR, 4.74; CI95, 1.15-19.42; P = .03). Chloramphenicol-resistant VRE isolates were more likely to be susceptible to beta-lactams and resistant to tetracycline than were chloramphenicol-susceptible VRE isolates.


CONCLUSIONS
Significant increases in the prevalence of chloramphenicol-resistant VRE may limit the future utility of chloramphenicol in the treatment of VRE infections, and close monitoring of susceptibility trends should continue. The association between fluoroquinolone use and chloramphenicol-resistant VRE, reflecting possible co-selection of resistance, suggests that recent dramatic increases in fluoroquinolone use may have broader implications than previously recognized.
Division of Infectious Diseases, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Carolyn V
CV
Gould
Neil O
NO
Fishman
Irving
I
Nachamkin
Ebbing
E
Lautenbach
D016470:Bacteremia / Q000382:microbiology*; D016022:Case-Control Studies; D002701:Chloramphenicol / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016983:Enterococcus / Q000187:drug effects / Q000302:isolation & purification*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015143:Philadelphia; D012307:Risk Factors; D020713:Vancomycin Resistance
D002701:Chloramphenicol