Acinetobacter baumannii microbiological and phenotypic characteristics of isolates from Intensive Care Unit of the Department of Internal Medicine at the University Hospital Centre in Zagreb over a four-year period

Acinetobacter baumannii is an opportun-istic nosocomial pathogen and one of the six most important multidrug-resistant microorganisms in intensive care units (ICU). The aim of this study was to determine the prevalence of antimicrobial resistant A. baumannii strains in ICU. We analysed antibiotic susceptibility of A. baumannii isolates collected in University Hospital Centre Zagreb over a four-year period (2011-2014) based on the hospital computer system data (BIS). The data were interpreted according to Clinical and Lab-oratory Standards Institute criteria.All strains from 2014 were found to be resistant to meropenem, which is a sig-nificant increase when compared to 1.4% in 2011 and 81.8% in 2012. The resistance rate to imipenem increased to 95.8% in 2014 from 91.4% in 2011 and 81.8% in 2012. Colistin resistance, confirmed by E test, was found only in one strain in 2013. The resistance rates of other antimicrobial agents were as follows: ampicillin/sulbac-tam 8.6% and 73.9%, netilmicin 70.6% and 83.3%, gentamicin 48.6% and 91.7%, ami-kacin 82.4% and 80.0% and ciprofloxacin 100% and 100% in 2011 and 2014 respec-tively.Our data confirmed a multidrug-resist-ance phenotype in Acinetobacter bauman-nii strains isolated in ICU at the Clinical Hospital Centre, with a significant increase in resistance rates between 2011 and 2014 against certain antimicrobial agents in-cluding ampicilin/sulbactam and carbap-enems.