Molecular detection of CTX-M gene in extended spectrum β-lactamases producing multidrug-resistant Gram-negative bacterial isolates

Abstract

Production of β-lactamases is the most important mechanism for bacterial resistance to penicillin, cephalosporins, and carbapenems.Antibiotic resistant bacterial isolates pose a higher burden to health care settings.In this study, extended spectrum β-lactamase (ESBL), metallo β-lactamase (MBL) and AmpC β-lactamase (AmpC) production were screened among Gram-negative bacterial isolates from the clinical specimens and the positivity of CTX-M gene among ESBL producers was analyzed. ESBLs, MBL, and AmpC producers were identified using Combination Disc Method(CDM). Antibiotic susceptibility of bacterial isolates was screened using Kirby-Bauer disc diffusion method. Positivity of CTX-M genein ESBL producing bacterial isolates wasanalyzed by Polymerase chain reaction and DNA sequencing. Out of 73 bacterial isolates, 38 were Escherichia coli, 21Klebsiella pneumoniae, 10Pseudomonas aeruginosa,3 Proteus vulgaris, and 1Enterobacter aerogenesA total of45 isolates were identified as ESBL producers followed by 14were AmpC, 11 wereboth ESBL and AmpC,and only 2 wereMBL producers. Five ESBL producing isolates showed positive for CTX-M andsequencing analysis showed all five were belonging to CTX-M-15 type.This study finding revealed thatCTX-M-15 type variant was found among ESBL producers. CTX-M-15 gene positive isolates showed positive for multiple β-lactamase production and possess high level of drug resistance profile compared to non-CTX-M positive ESBL producers.