Antimicrobial use, incidence, etiology and resistance patterns in bacteria causing ventilator-associated pneumonia in a clinical-surgical icu

Introduction: Antimicrobial resistance is an increasing threat in hospitalized patients and inappropriate empirical antimicrobial therapy is known to adversely affect outcome in ventilator-associated pneumonia (VAP). The aim of this study was to evaluate antimicrobial usage, incidence, etiology and antimicrobial resistance trends for prominent nosocomial pathogens causing ventilator-associated pneumonia in a clinical-surgical ICU. Methods: Gram-negative bacilli and S. aureus causing VAP, as well as their antimicrobial resistance patterns and data on consumption (defined daily dose (DDD) per 1000 patient-days) of glycopeptides, extended-spectrum cephalosporins and carbapenems in the unit were evaluated in two different periods (A and B). Results: Antimicrobial use was high, mainly of broad-spectrum cephalosporins, with a significant increase in the consumption of glycopeptides ( P< 0.0001) and carbapenems ( P< 0.007) in the period B. For A. baumannii and members of the Enterobacteriaceae family a 5.27 and 3.06–fold increase in VAPs, respectively, were noted and a significant increase in resistance rates was found for imipenem-resistant A. baumannii ( P= 0.003) and 3rd generation cephalosporins-resistant Enterobacteriaceae ( P= 0.01) isolates in this same period. Conclusion: Our results suggest that there is a link between antibiotics usage at institutional levels and resistant bacteria. The use of carbapenems was related to high rate of resistance in A. baumannii and therefore high consumption of imipenem / meropenem could play a major role in selective pressure exerted by antibiotics in A. baumannii strains.