Imipenem resistance among pseudomonas aeruginosa isolates: risk factors for infection and impact of resistance on clinical and economic outcomes.
OBJECTIVE
To identify risk factors for infection with imipenem-resistant Pseudomonas aeruginosa and determine the impact of imipenem resistance on clinical and economic outcomes among patients infected with P. aeruginosa.


METHODS
An ecologic study, a case-control study, and a retrospective cohort study.


METHODS
A 625-bed tertiary care medical center.


METHODS
All patients who had an inpatient clinical culture positive for P. aeruginosa between January 1, 1999, and December 31, 2000.


RESULTS
From 1991 through 2000, the annual prevalence of imipenem resistance among P. aeruginosa isolates increased significantly (P<.001 by the chi (2) test for trend). Among 879 patients infected with P. aeruginosa during 1999-2000, a total of 142 had imipenem-resistant P. aeruginosa infection (the case group), whereas 737 had imipenem-susceptible P. aeruginosa infection (the control group). The only independent risk factor for imipenem-resistant P. aeruginosa infection was prior fluoroquinolone use (adjusted odds ratio, 2.52 [95% confidence interval {CI}, 1.61-3.92]; P<.001). Compared with patients infected with imipenem-susceptible P. aeruginosa, patients infected with imipenem-resistant P. aeruginosa had longer subsequent hospitalization durations (15.5 days vs 9 days; P=.02) and greater hospital costs (81,330 dollars vs 48,381dollars ; P<.001). The mortality rate among patients infected with imipenem-resistant P. aeruginosa was 31.1%, compared with 16.7% for patients infected with imipenem-susceptible P. aeruginosa (relative risk, 1.86 [95% CI, 1.38-2.51]; P<.001). In multivariable analyses, there remained an independent association between infection with imipenem-resistant P. aeruginosa and mortality.


CONCLUSIONS
The prevalence of imipenem resistance among P. aeruginosa strains has increased markedly in recent years and has had a significant impact on both clinical and economic outcomes. Our results suggest that curtailing use of other antibiotics (particularly fluoroquinolones) may be important in attempts to curb further emergence of imipenem resistance.
Lautenbach
Ebbing
E
Division of Infectious Diseases, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104-6021, USA. elautenb@cceb.med.upenn.edu
Weiner
Mark G
MG
Nachamkin
Irving
I
Bilker
Warren B
WB
Sheridan
Angela
A
Fishman
Neil O
NO
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D003428:Cross Infection / Q000188:drug therapy* / Q000401:mortality; D024881:Drug Resistance, Bacterial; D006801:Humans; D015378:Imipenem / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D010414:Pennsylvania / Q000453:epidemiology; D015995:Prevalence; D011552:Pseudomonas Infections / Q000188:drug therapy* / Q000191:economics / Q000401:mortality; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity*; D012307:Risk Factors
D015378:Imipenem