Genotypic to Phenotypic Resistance Discrepancies Identified Involving β-Lactamase Genes, KPC, IMP, NDM-1, and VIM in Uropathogenic .

INTRODUCTION

carbapenemase (KPC) belongs to the Group-A β-lactamases that incorporate serine at their active site and hydrolyze various penicillins, cephalosporins, and carbapenems. Metallo-beta-lactamases (MBLs) are group-B enzymes that contain one or two essential zinc ions in the active sites and hydrolyze almost all clinically available β-lactam antibiotics. remains the pathogen with the most antimicrobial resistance to KPC and MBLs.

METHODS

This research investigated the KPC, and MBL genes, namely, IMP, VIM, and NDM-1 and their phenotypic resistance to isolated from urinary tract infections (UTI) in Bangladesh. Isolated UTI were identified by API-20E and 16s rDNA gene analysis. Their phenotypic antimicrobial resistance was examined by the Kirby-Bauer disc diffusion method, followed by minimal inhibitory concentration (MIC) determination. KPC, IMP, NDM-1, and VIM genes were evaluated by polymerase chain reactions (PCR) and confirmed by sequencing.

RESULTS

Fifty-eight were identified from 142 acute UTI cases. Their phenotypic resistance to amoxycillin-clavulanic acid, cephalexin, cefuroxime, ceftriaxone, and imipenem were 98.3%, 100%, 96.5%, 91.4%, 75.1%, respectively. Over half (31/58) of the isolates contained either KPC or one of the MBL genes. Individual prevalence of KPC, IMP, NDM-1, and VIM were 15.5% (9), 10.3% (6), 22.4% (13), and 19% (11), respectively. Of these, eight isolates (25.8%, 8/31) were found to have two genes in four different combinations. The co-existence of the ESBL genes generated more resistance than each one individually. Some isolates appeared phenotypically susceptible to imipenem in the presence of KPC, IMP, VIM, and NDM-1 genes, singly or in combination.

CONCLUSION

The discrepancy of genotype and phenotype resistance has significant consequences for clinical bacteriology, precision in diagnosis, the prudent selection of antimicrobials, and rational prescribing. Heterogeneous phenotypes of antimicrobial susceptibility testing should be taken seriously to avoid inappropriate diagnostic and therapeutic decisions.