Risk Factors Associated with Acquisition of Carbapenem-Resistant Acinetobacter baumanii in Intensive Care Unit (ICU) A, December—February, 2008-2009

Background: Carbapenem-resistant Acinetobacter baumanii (CR-AB) can cause serious infections among critically ill, hospitalized patients, resulting in significant morbidity and mortality. In December 2008, it was observed that ICU A had an unexpectedly large number of patients receiving care from a particular service acquire CR-AB while patients receiving care from a different service, but housed within the same ICU, did not acquire CR-AB.

Objective: We investigated this cluster of cases in order to identify risk factors associated with CR-AB acquisition in ICU A from December—February, 2008-2009.

Methods: We conducted a case-control study to assess odds ratios (OR) of potential risk factors for CR-AB acquisition.  Routine surveillance cultures for CR-AB were obtained from all patients upon admission to all ICU, every 7 days thereafter, and upon discharge from the ICU according to institutional policy.  Case definition criteria included admission to ICU A, involvement of a particular service in patient care, and subsequent positive culture results for CR-AB after negative surveillance cultures for CR-AB upon admission to the unit. Controls were admitted to the same ICU for at least 24 hours within one week of a case’s admission date and cared for by the same service but did not acquire CR-AB. Electronic medical charts were reviewed, and univariate and bivariate analyses were conducted.

Results: Eleven cases of CR-AB culture positive patients and sixteen controls were identified. Cases spent a mean of 20.2 days in ICU A, while controls spent a mean of 6.1 days in ICU A. More than half (54.6%) of cases were CR-AB culture positive from a wound culture. Cases had a mean of 4.9 trips to the operating room, while controls had a mean number of 1.8 trips to the operating room. CR-AB acquisition was associated with having had 5 or greater number of trips to the operating room [OR=18; 95% Confidence Interval (CI) = 1.42, 881.05], wound irrigation in the operating room [OR=12.9; 95% CI = 1.16, 618.42), and Piperacillin/Tazobactam prior to CR-AB culture positivity [OR=9.9; 95% CI = 1.22, 115.8].

Conclusions: CR-AB acquisition was associated with longer stay in ICU A, frequent trips to the operating room, wound irrigation in the operating room, and the use of piperacillin-tazobactam. Further investigation into procedures in the operating room, including wound irrigation, as well as improved antimicrobial stewardship in the ICU are warranted.