engleski

Carbapenemases in urinary isolates of Enterobacteriaceae from Croatia

Recently, emergence of carbapenem-resistance was observed among Enterobacteriaceae causing urinary tract infections in Croatia. The aim of the study was to characterize the carbapenem-resistance mechanisms and the molecular epidemiology of carbapenem resistance in urine isolates of Enterobacteriaceae from Croatia. MATERIAL AND METHODS The antimicrobial susceptibility to a wide range of antibiotics was determined by broth microdilution method. Double-disk-synergy test (DDST) was performed to detect ESBLs and modified Hodge test (MHT) was used to screen for production of carbapenemases. MBL E-test was used to screen for production of metallo-β-lactamases. Additionally the isolates were tested by combined disks tests using four disks of meropenem or imipenem one without and the other three with 3-aminophenylboronic acid test with 0.1 M EDTA or both 3-aminophenylboronic and EDTA to screen for KPC, MBLs or simoultaneous production of MBL and KPC, respectively. The transferability of meropenem resistance was determined by conjugation (broth mating method) employing E. coli A15R- strain resistant to rifampicin. The presence of genes encoding broad and extended-spectrum β-lactamases (blaSHV, blaTEM, blaCTX-M and blaPER-1), plasmid-mediated AmpC beta-lactamases, group A carbapenemases (blaKPC, blaSME, blaIMI, blaNDM), metallo β-lactamases (blaVIM, blaIMP and blaNDM), and carbapenem hydrolyzing oxacillinases (blaOXA-48) was determined by PCR. RESULTS In total 47 strains (31 Enterobacter spp., 12 Klebsiella pneumoniae, 2 Citrobacter spp., and one Escherichia coli and Serratia marcescens, respectively) with reduced susceptibility to carbapenems, isolated from urine during 2012-2013 from two large hospital centres in Croatia were analyzed. All strains were resistant to amoxycillin alone and combined with clavulanate, cefuroxime, ceftazidime, cefotaxime and ceftriaxone. The strains showed variable degree of susceptibility to cefepime, imipenem, meropenem, ertapenem, aminoglycosides and ciprofloxacin. Except colistin (all isolates were susceptible), potent activity against carbapenemase producing isolates exhibited also amikacin (50% susceptible isolates). Genes encoding carbapenemases were found in 38 isolates, with VIM-1 metallo-enzyme being the most prevalent and found in 34 strains (25 enterobacter isolates ; one strain coharboured VIM-1 and NDM-1, 6 klebsiella strains, 2 citrobacter and one serratia isolate, respectively), NDM-1 was found in one Enterobacter cloacae, and KPC-2 in three Klebsiella pneumoniae strains. Nine strains were negative for true carbapenemases and harboured only ESBL belonging to CTX-M family. Plasmids encoding VIM MBLs belonged to widespread IncA/C or L/M PBRT. CONCLUSIONS The study demonstrated emergence of carbapenemase-producing enterobacteriaceae associated with urinary tract infections which could pose a serious therapeutic problem. The predominance of VIM-1 and KPC-2 β-lactamase was observed. In the previous studies enterobacteriaceae positive for ESBLs belonging to CTX-M family were found to be dominant multiresistant pathogen among urinary isolates but continuing shift to carbapenemase producers is observed.

carbapenemase; VIM-1; NDM-1; resistance; urinary tract infections

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