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Risk Factors Associated With Resistance to Ciprofloxacin in Clinical Bacterial Isolates From Intensive Care Unit Patients

  • Phillip D. Levin (a1) (a2), Robert A. Fowler (a1) (a3) (a4), Cameron Guest (a1) (a4), William J. Sibbald (a1) (a3) (a4), Alex Kiss (a5) (a4) and Andrew E. Simor (a3) (a6) (a4)...



To determine risk factors and outcomes associated with ciprofloxacin resistance in clinical bacterial isolates from intensive care unit (ICU) patients.


Prospective cohort study.


Twenty-bed medical-surgical ICU in a Canadian tertiary care teaching hospital.


All patients admitted to the ICU with a stay of at least 72 hours between January 1 and December 31, 2003.


Prospective surveillance to determine patient comorbidities, use of medical devices, nosocomial infections, use of antimicrobials, and outcomes. Characteristics of patients with a ciprofloxacin-resistant gram-negative bacterial organism were compared with characteristics of patients without these pathogens.


Ciprofloxacin-resistant organisms were recovered from 20 (6%) of 338 ICU patients, representing 38 (21%) of 178 nonduplicate isolates of gram-negative bacilli. Forty-nine percent of Pseudomonas aeruginosa isolates and 29% of Escherichia coli isolates were resistant to ciprofloxacin. In a multivariate analysis, independent risk factors associated with the recovery of a ciprofloxacin-resistant organism included duration of prior treatment with ciprofloxacin (relative risk [RR], 1.15 per day [95% confidence interval {CI}, 1.08-1.23]; P < .001), duration of prior treatment with levofloxacin (RR, 1.39 per day [95% CI, 1.01-1.91]; P = .04), and length of hospital stay prior to ICU admission (RR, 1.02 per day [95% CI, 1.01-1.03]; P = .005). Neither ICU mortality (15% of patients with a ciprofloxacin-resistant isolate vs 23% of patients with a ciprofloxacin-susceptible isolate; P = .58 ) nor in-hospital mortality (30% vs 34%; P = .81 ) were statistically significantly associated with ciprofloxacin resistance.


ICU patients are at risk of developing infections due to ciprofloxacin-resistant organisms. Variables associated with ciprofloxacin resistance include prior use of fluoroquinolones and duration of hospitalization prior to ICU admission. Recognition of these risk factors may influence antibiotic treatment decisions.


Corresponding author

Department of Microbiology, Sunnybrook Health Sciences Centre, B121-2075 Bayview Avenue, Toronto, Ontario, CanadaM4N 3M5 (


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