Investigation of the antibiotic susceptibility patterns of pathogens causing nosocomial infections

The aim of this study is to determine the resistance patterns of bacteria causing nosocomial infections. The outcome of this resistance was followed for 3 years. This study was carried out during 2000 to 2002 at a university hospital in Turkey. The resistance patterns of 570 bacteria (390 Gram-negative, 180 Gram-positive) against meropenem, imipenem, ceftazidime, cefotaxime, cefepime, piperacillin/tazobactam, ciprofloxacin and tobramycin were investigated using the E-test. Extended-spectrum beta-lactamase (ESBL) production was determined using ceftazidime and ceftazidime/clavulanic acid E-test strips. Meropenem was the most effective antibiotic against Gram-negative organisms (89.0%); this was followed by imipenem (87.2%) and piperacillin/tazobactam (66.4%). The most active antibiotic against Gram-positive bacteria was imipenem (87.2%) and this was followed by piperacillin/tazobactam (81.7%) and meropenem (77.8%). The rates of production of ESBL by Escherichia coli were 20.9%, Klebsiella pneumoniae 50% and Serratia marcescens were 46.7%. Extended-spectrum beta-lactamase production increased each year (21.7%, 22.1% and 45.5%). All of the ESBL producing isolates were sensitive to meropenem and 98.5% sensitive to imipenem. AmpC beta-lactamase was produced by 20.9% of the Enterobacter species spp, Citrobacter spp. and Serratia marcescens. All of these were sensitive to meropenem and 77.8% to imipenem and ciprofloxacin. Multi-drug resistance rates in Acinetobacter spp were 45.4% and 37.7% in Pseudomonas aeruginosa isolates. As in the entire world, resistance to antibiotics is a serious problem in our country. Solving of this problem depends primarily on prevention of the development of resistance.