Identification of VIM and IMP genes and metallo-betalactamase enzymes in Escherichia coli isolates by molecular and phenotypic methods in shahrekord educational hospitals

Among urine pathogens, Escherichia coli (E. coli) causes 80% of urinary tract infections (UTIs). Due to the destructive nature of penicillins, cephalosporins and carbapenems (except for monobactam such as aztreonam) and carbapenemase enzymes have created many problems for treating infectious diseases. Therefore, this study aimed to investigate the phenotypic and molecular characterization of metallo-beta-lactamase (MBL) genes produced by E. coli isolates in an educational hospital during 2016-2017.

This cross-sectional study investigated 80 UTI samples affected by E. coli. In addition, antibiotic susceptibility was evaluated by disk diffusion and E-test methods for two antibiotics of meropenem and imipenem. Phenotypic tests containing modified Hodge test, ethylenediaminetetraacetic acid (EDTA) disk synergy test, and AmpC Disk were performed to identify MBL enzyme-producing strains. Finally, the frequency of Verona integron-encoded metallo-β-lactamase (VIM) and imipenemase (IMP) genes was determined by polymerase chain reaction (PCR).

Among 80 E. coli samples, 21 (26.25%) isolates were resistant to meropenem and imipenem as detected by the disk-diffusion method and E-test. Further, phenotypic tests including modified Hodge test, EDS test, and AmpC disk test showed the positivity of 15 (18.75%), 15 (18.75%), and 8 (10%) isolates, respectively (P < 0.001). Eventually, polymerase chain reaction (PCR) test results for the VIM gene showed 19 (23.75%) positive isolates of E. coli, but the IMP gene was observed in none of the isolates (P<0.001).

In general, the emergence of E. coli producing MBL enzymes is a serious threat among clinical infections. The findings of this study indicated the presence of E. coli producing MBL. These enzymes can degrade carbapenems antibiotics, the last class current treatment of multiple drug-resistance infections.