Identification of Arg32Ser, His92Tyr and Leu147Phe novel mutations in chromosomally mediated β-lactamase SHV and in silico characterization to understand their substrate activity imparting resistance

The emergence of beta-lactam resistance is yearning for clinical significance in Enterobacteriaceae, which are categorized under global priority pathogen lists by the World Health Organization. Likewise, the prevalence of numerous beta-lactamase enzymes, mutational propensity in such bacteria, and their role in accelerating resistance is still a major concern. Thus, the present work intends to characterize the beta-lactamase producing bacteria isolated from acute diarrheal patients to understand their chromosomally acquired resistance pattern through molecular characterization and in silico approaches. The current study highlights the first identified Escherichia fergusonii and Escherichia marmotae species and their beta-lactamase encoding genes, blaOKP-A, blaNDM and blaOXA from the unexplored Enterobacteriaceae family from North East India. First-ever reported point mutations such as Arg32Ser, His92Tyr, and Leu147Phe were observed in BlaSHV protein of two Klebsiella pneumoniae isolates S-35 and S-46. In molecular docking, non-catalytic site H-bond interactions of Arg 218, Ala 223, Asn 128, Ser 126, Gln 95, Asp 100, Tyr 101, Ser 102, Ala 274 with a low binding affinity towards BlaSHV was found. This correlates with the high imipenem, ceftazidime, cefuroxime, ceftriaxone, and cefpodoxime resistance in Klebsiella pneumoniae S-35 with the complementary effect of mutations Arg32Ser and Leu147Phe. Besides, the role of His92Tyr mutation in controlling the resistance in Klebsiella pneumoniae S-46 is also illustrated. Thus, our study highlights the novel mutations of beta-lactamase and its clinical importance with altered resistance profiles. This could be useful to design better therapeutics and to readjust antibiotic treatment regimes against them and control to grow more resistance under selective pressure.

Automated summary

The study identified novel mutations of beta-lactamase and their clinical importance in Enterobacteriaceae family, highlighting the resistance pattern and molecular mechanisms in bacteria isolated from acute diarrheal patients. The identified mutations in BlaSHV protein and their interactions with antibiotics provide insight into antibiotic resistance in Klebsiella pneumoniae isolates.