Molecular characterization and in silico analysis of naturally occurring TEM beta-lactamase variants among pathogenic Enterobacteriaceae infecting Indian patients.

Abstract

Cephalosporin resistance, particularly due to bla TEM encoded β-lactamases, among Enterobacteriaceae is, though, an increasing public health problem in India; their circulating genetic variants remain unknown. The present study deals with determination of bla TEM variants among 134 pathogenic Enterobacteriaceae of Indian origin. Their resistance profile against 3rd generation cephalosporins was determined. The presence of bla TEM variants among the bacterial plasmids was characterized by PCR followed by sequencing. Intergenic relations among the variants was determined by phylogenetic analysis. bla TEM protein were modeled by Modeller9v5 and verified. The catalytic pockets were characterized, and their interaction with cephalosporins was analyzed using AutoDock tools. More than 87% of isolates showed cephalosporin resistance with ESBL production among 57.8% of Escherichia coli and 50.6% of klebsiella pneumoniae. bla TEM-1 (84.21%), bla TEM-1 like (3.94%), bla TEM-33 (3.94%), bla TEM-116 (3.94%), bla TEM-169 (3.94%), and bla TEM-190 (7.89%) were detected in 76 isolates. Four variants, namely, bla TEM-1like, bla TEM-33, bla TEM-169, and bla TEM-190, coexisted in 3 isolates. The largest catalytic pocket of bla TEM-33 explained its expanded activity towards β-lactam-β-lactamase inhibitor combinations. Molecular docking indicated differential resistance pattern of bla TEM variants.