engleski

vidence of coproduction of VIM-1 and NDM-1 metallo-beta-lactamase and persistant predominance of metallo-beta-lactamases among Enterobacteriaceae from Croatia

Objectives The first carbapenem –resistant strain of Klebsiella pneumoniae was isolated in 2008. in University Hospital Center in Zagreb. A remarkable increase in the in the number of carbapenem resistant isolates was observed in 2011 and 2012. . The carbapenem resistance of these isolates was analysed and VIM-1 was found to be the most prevalent type, followed by NDM-1 and KPC-2. In 2013 an increasing trend of carbapenem-resistant Enterobacteriaceae was observed. Te aim of the study was to analyse the carbapenem-resistance and the molecular epidemiology of these strains. Methods In total 41 carbapenem non-susceptible strains of Enterobacteriaceae were collected from January till October 2013 from two hospital centers located in different geographic regions in Croatia. The strains were identified by Vitec automated system. The antimicrobial susceptibility to a wide range of antibiotics was determined by broth microdilution method according to CLSI. Double-disk-synergy test (DDST) was performed to detect ESBLs, combined disk test with PBA to detect plasmid-mediated ampC β-lactamases and modified Hodge test (MHT) was used to screen for production of carbapenemases. Combined disk test with meropenem combined with EDTA and PBA was used to screen for metallo and KPC beta-lactamases, respectively. The presence of genes encoding broad and extended-spectrum β-lactamases (blaSHV, blaTEM, blaCTX-M and blaPER-1), plasmid-mediated AmpC β-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 Thirteen strain originated from urine and stool, respectively, seven from rectal swab, five from tracheal aspirate and one from sputum, blood culture and wound swab , respectively. . The majority of strains were obtained from heamatology unit (18) and intensive care unit (12). Three strains originated from urology and medical ward respectively and one from neurology, oncology and surgery ward respectively. All strains were resistant to amoxycillin alone and combined with clavulanate and piperacillin with tazobactam, cefuroxime, cefazoline, ceftazidime, cefotaxime, ceftriaxone and ertapenem. Above 90% of the strains were resistant to imipenem, meropenem and cefoxitin. Only one strain was resistant to colistin. Amikacin and ciprofloxacin demonstrated moderate activity with 39% and 33% of resistant strains, respectively. Double disk-synergy test was positive in 32 strains indicating the production of ESBL. Ten strains were phenotypically positive for plasmid-mediated ampC beta-lactamases. All strains were positive in Hodge test indicating the production of carbapenemase. Combined disk test with PBA was positive in 12 and with EDTA in 27 strains indicating the production of KPC and metallo-beta-lactamases, respectively. All MBL-producing strains were positive in phenotypic tests for ESBLs. Twenty-seven strains were positive for blaVIM-1 as shown in Fig. 1, 12 for blaKPC-2 and two for blaNDM-1. Twenty-three strains coharboured blaTEM and 14 blaCTX-M genes. Two strains were found to coproduce VIM-1 and NDM-1 (C. freundii and E. cloacae). The production of KPC β-lactamases was associated with high level of resistance to all three carbapenems in contrast to VIM and NDM producing organisms which showed variable level of resistance to carbapenems. Conclusions The study found the persistence of VIM-1 and NDM-1 among our Enterobacteriaceae. To our knowledge this is the first report of coproduction of VIM-1 and NDM-1 and of the emergence of colistin resistance among Enterobacteriaceae from Croatia. Loss of colistin activity against carbapenem-resistant Enterobacteriaceae can pose a serious therapeutic problem because there are no options left for the treatment of infections associated with such isolates. Carbapenemase encoding genes are located on mobile genetic elements and thus their accurate detection is of uppermost importance.

metallo-beta-lactamases; KPC; Enterobacteriaceae;

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