Inadequate double-pseudomonal coverage with ciprofloxacin versus aminoglycosides in the intensive care unit

Introduction:

Pseudomonas aeruginosa is an important gram-negative bacilli often implicated in serious hospital and healthcare-associated infections.  Although controversial, combination antimicrobial therapy with two different classes is likely indicated in certain high-risk patients and severe infections.

Objectives:

This study compared the rates of resistance between ciprofloxacin and aminoglycosides to pseudomonas isolates that are resistant to piperacillin-tazobactam and/or cefepime in the intensive care units at our institution.

Study Design:

This is an observational, retrospective chart review.

Methods:

Medical records of adult patients admitted to any intensive care unit at Beaumont Hospital – Royal Oak between January 1, 2011 and December 31, 2012 were reviewed for microbiological cultures positive for pseudomonas isolates.  Patients’ demographics, source of positive cultures, antibiotic sensitivities, hospital and ICU mortality were documented.

Results:

A total of 323 pseudomonas isolates were identified and able to be evaluated.  The majority of the isolates were identified from sputum, urine and wound cultures.  The number of piperacillin-tazobactam and cefepime resistant isolates that were resistant to ciprofloxacin were 19/33 (57.6%) and 15/26 (57.7%), respectively.  The number of piperacillin-tazobactam and cefepime resistant isolates that were resistant to gentamicin, tobramycin and amikacin were 11/33 (33.3%), 10/33 (30.3%) and 1/9 (11.1%), respectively.

Conclusions:

High-quality data concerning the use of combination or monotherapy for serious infections due to pseudomonas is lacking.  Combination therapy is likely indicated in certain high risk patients and in severe infections.  In our study, we found piperacillin-tazobactam and cefepime resistant pseudomonas isolates cultured from critically ill patients were approximately twice as likely to also be resistant to ciprofloxacin compared to aminoglycosides.  When using combination therapy for treatment of pseudomonas infections in critically ill patients, aminoglycosides should be favored over ciprofloxacin in the absence of contraindications.