Susceptibility of extended spectrum beta-lactamase producing bacterial strains against to various antibiotics

2. ABSTRACT SUSCEPTIBILITY OF EXTENDED SPECTRUM BETA-LACTAMASE PRODUCING BACTERIAL STRAINS AGAINST TO VARIOUS ANTIBIOTICS Extended spectrum of beta-lactamases have become a major beta- lactam resistance mechanism in Gram negative enteric bacilli, in recent two decades. The number of the choice of antibiotic that is appropriate for usage in the infections by extended spectrum beta-lactamase producing organisms is severely limited. The aim of this study is to detect the in vitro activity of some beta-lactam and non beta-lactam antibiotics against the ESBL producing bacterial species that were isolated from the patients in Firat Medical Center. Also, an another purpose is to investigate the distribution of the antibiotic resistance in medical clinics, in our institute. This study was included in total 208 ESBL (+) organisms that were isolated from nearly 200 inpatients or outpatients in Firat University's hospital, between Nov-2001 and May-2003. Isolates were identified at species level by using conventional bacterial identification methods. Eighty- eight of 208 were identified as Klebsiella pneumoniae, 39 were identified as Klebsiella oxytoca, 71 were identified as Escherichia coli, 6 were identified as Proteus mirabilis, 1 was identified as Proteus vulgaris and 3 were Enterobacter aerogenes. In vitro activity of isepamicin, amikacin, gentamicin, ciprofloxacin, moxifloxacin, cefoperazon-sulbactam and piperacillin-tazobactam were measured with using microdiution and E-Test methods. Antibiotic susceptibility of ESBL producing isolates were determined as isepamicin 92%, amikacin 90%, gentamicin 49%, ciprofloxacin 65%moxifloxacin 60%, cefoperazon-sulbactam 45% and piperacillin-tazobactam 56%. We did not find any significant difference at antibiotic susceptibility between ESBL producing bacterial species. It was found that the MIC50 and MICgo values of isepamicin and amikacin were both in susceptible boarders. The MIC50 of the both quinolones, ciprofloxacin and moxifloxacin, were in susceptible boarders, whereas MIC90 of these antibiotics were in resistant boarders. Furthermore, neither MIC50 nor MIC90 values of cefoperazon- sulbactam, piperacillin-tazobactam and gentamicin were in susceptible boundaries. The highest resistance rates of the tested antibiotics were found in surgical isolates. Quinolone resistance of the surgical isolates was detected as 4 fold higher than the pediatric isolates. As a result, we found that isepamicin and amikacin were have the highest activity, ciprofloxacin and moxifloxacin were have the moderate activity and cefoperazon-sulbactam, piperacillin-tazobactam and gentamicin were have the lowest activity against ESBL producing strains. Appropriate antibiotic usage and more active infection control committees are provided for reduction of ESBLs prevalence in the hospitals. Key Words: ESBL, MIC, isepamicin, amikacin, gentamicin, ciprofloxacin, moxifloxacin, cefoperazon-sulbactam, piperacilin-tazobactam. E. coli, Klebsiella, Proteus, Enterobacter.