939

Abstract

Introduction: Gram-negative bacteria (GNB) such as Pseudomonas aeruginosa(PSA) and Acinetobacter baumannii(ACB) are a major cause of morbidity and mortality in the critically ill patient.With increasing concern about development of drug resistance, the need for methods to halt the development of resistance is apparent.Among these, antibiotic rotation(AR) has prompted much debate.At our hospital, the use of an AR protocol for empiric broad-spectrum coverage has been used by the surgery/trauma team since Jan 2008.We sought to describe the impact of the protocol on susceptibility of select GNB including PSA, ACB, Serratia spp(SER), Citrobacter spp(CIT). Hypothesis: We hypothesized that the use of AR wouldn’t worsen susceptibility in select GNB. Methods: This retrospective cohort study involved trauma and surgery patients admitted to the STICU from 2007-11.Only patients admitted to the trauma or general surgery services were considered.Only isolates with susceptibility results to antibiotics used in the rotation: piperacillin-tazobactam(PT),cefepime(CE),meropenem(ME),imipenem-cilistatin(IM),levofloxacin(LE),ciprofloxacin(CI), gentamicin(GE),tobramycin(TO) were analyzed. Results: 346 isolates for the specified bacteria were identified and included in the analysis.The majority of isolates were from upper respiratory and wound sources.The percent of PSA isolates susceptible to PT increased during the study period, 77%(2008) to 92% (2011).Increased PSA susceptibility was also noted with CE, 60% (2008) to 75% (2011), LE, 57% (2008) to 72% (2011) and TO, 69% (2008) to 83% (2011).MIC trends for the selected antibiotics also improved.The percent of ACB isolates susceptible to PT also increased, 17% (2008) to 67% (2011).Increased ACB susceptibility was also noted with CE, GE, TO, ME although the number of positive ACB isolates was low.Isolate susceptibilities of SER and CIT were unchanged during the study period. Conclusions: The use of an AR protocol doesn’t appear to worsen susceptibility in the surgical and trauma population.Improvement was noted in PSA and ACB susceptibilities, which was statistically significant.The use of an AR is a viable option to improve susceptibilities, however larger studies are necessary.