Molecular Identification of CTX-M and SHV Betalactamase Genes in Escherichia Coli Clinical Isolates in Isfahan

Antimicrobial resistance is a worldwide problem causing health threats. Escherichia coli is one of the most important bacteria that causes resistance problems. The aim of the present study was to evaluate the frequency of Escherichia coli, a extended spectrum beta-lactamase producing CTX-M and SHV, in hospital and non-hospital clinical specimens in Isfahan.

In the present cross-sectional descriptive study conducted in 2019, 100 samples of hospital and non-hospital of Escherichia coli strains were collected and confirmatory biochemical tests were performed to identify these strains. Resistance of strains to common antibiotics was assessed by disk diffusion method according to CLSI instructions. To perform phenotypic confirmation test of extended spectrum beta-lactamase producing strains, the combined disk method based on CLSI instructions was used. PCR was performed with specific primers to examined of encoding genes presence of SHV and CTX-M. The collected data were analyzed using statistical tests based on one-way analysis of variance and independent t-test.

From the studied samples, the highest antibiotic resistance was related to cefotaxime (45%) and the least antibiotic resistance was related to cefepime (39%). The results of the initial screening test showed that out of 100 Escherichia coli approved by differential tests, 38 (38%) were resistant to cephalosporin representatives and possibly produced extended-spectrum beta-lactamase. Among these samples, 33 (86.8%) after Combined disk method were confirmed as extended spectrum beta–lactamases (ESBL) producing, of which 69.7% (23 strains) had both genes encoding CTX- M and SHV had 15.2% (5 strains) of the gene encoding CTX-M and 12.1% (4 strains) had the gene encoding SHV. In one sample (3%) none of the genes encoding CTX-M and SHV were present.

Based on the performed experiments and statistical analysis on hospital and non-hospital isolates, it was concluded that the SHV and CTX-M beta-lactamase genes in Escherichia coli had a significant increase in frequency. There was a significant relationship between SHV and CTX-M genes in hospital and non-hospital samples, so that the frequency of SHV and CTX-M genes in Escherichia coli was higher in hospital samples than non-hospital samples. There was no significant relationship between the genes identified and the type of isolates collected.