Prevalence of plasmid-encoded carbapenemases in multi-drug resistant Escherichia coli from patients with urinary tract infection in northern Iran

OBJECTIVE(S): Resistance to carbapenems as the last line for controlling resistant bacteria is increasing due to production of carbapenemase. The aim of this study was to detect the plasmid-encoded carbapenemases using phenotypic methods and multiplex PCR among the multi-drug resistant (MDR) isolates from patients with urinary tract infection (UTI) in northern Iran. MATERIALS AND METHODS: Antimicrobial susceptibility testing and extended spectrum β-lactamase (ESBL) production test were performed for 91 MDR Escherichia coli strains by disc diffusion and double disk synergy tests (DDST), respectively. Carbapenemases production was confirmed using Hodge test, EDTA double disk synergy test (EDST) and combined disk test (CDT). The isolates were subjected to PCR targeting bla(IMP), bla(VIM), bla(KPC) and bla(OXA-48) β-Lactamase genes. RESULTS: Resistance of isolates to 1(st), 2(nd), 3(rd), and 4(th) generations of cephalosporins, carbapenems, and penicillins were 73%, 84.5%, 62%, 37.5%, 17.5%, and 76%, respectively. Based on CDT and Hodge test, 1 (3%) and based on EDST, 2 (6%) of 33 ESBL producers synthesize a type of carbapenemase. The frequency of bla(IMP), bla(VIM), bla(KPC), and bla(OXA-48) genes was 8.7%, 9.8%, 2.1%, and 15.3%, respectively. Existence of bla(IMP) conferred more resistance to cephalotin, fosfomycin, and piperacillin (P≤0.01) and carrying bla(VIM) caused more resistance to cephalotin, cefepime, and ceftazidime (P≤0.01). The presence of bla(KPC) conferred more resistance to cephalotin and presence of bla(OXA-48) caused more resistance to chloramphenicol and piperacillin (P≤0.05). CONCLUSION: Identification and controlling of this nearly low frequent ESBL and carbapenemase producing strains are important due to the presence of plasmid genes encoding carbapenemase.