Phenotypic and Genotypic Investigation of Metallobetallactamase Resistance in Clinical Isolates of Escherichia Coli and Klebsiella Pneumoniae

The use of broad-spectrum cephalosporins in the treatment of infections has led to the emergence of a new class of beta-lactamases called metallobetalactamase, these enzymes belong to Ambler's class B beta-lactamases. Group A and B metallobetalactamases in Enterobacteriaceae cause problems in treatment. The present study was conducted with the aim of phenotypic investigation of Escherichia coli and Klebsiella pneumoniae metallobetalactamase producing strains, as well as molecular investigation of SPM, VIM, SIM, IMP and GIM genes.

The present descriptive-quantitative study was conducted on 185 patients hospitalized in the special care units of Milad Hospital in Tehran from March to May 2018-2019, and 45 strains of Escherichia coli and 62 strains of Klebsiella pneumoniae were selected. In order to check the antibiotic resistance of the strains, diffusion test in agar was used and also to check the phenotypic of the metallobetalactamase producing strains, the combined disc method was used. Molecular investigation of metallobetalactamase producing genes was done by PCR method. The collected data were analyzed using Fisher's test.

In the present study, the highest antibiotic resistance of Escherichia coli and Klebsiella pneumoniae strains was observed to cotrimoxazole and cefepime antibiotics, respectively. 14.5% of Klebsiella pneumoniae strains and 15.5% of Escherichia coli strains produced metallobetalactamase enzyme in the phenotypic method. Also, 88.9% of the studied Escherichia coli strains carried the SPM gene, 40% carried the VIM gene, 66.7% carried the SIM gene, and 15.6% carried the IMP gene. SPM, VIM, SIM, IMP and GIM genes were found to be 54.8, 41.9, 58.1, 3.2 and 8.1% in Klebsiella pneumoniae strains, respectively.

In the present study, there was a high percentage of genes producing metallobetalactamase enzyme in bacteria, while 14.5% of Klebsiella pneumoniae strains and 15.5% of Escherichia coli strains were producing metallobetalactamase enzyme in the phenotypic method. that genes producing enzymes exist in bacteria and are not expressed in high amounts. There waS also the possibility that these genes were expressed, but could not be checked with the usual phenotypic methods, so efforts should be made to find reliable, cheap and easy phenotypic methods for phenotypic examination.