Phenotypic and Molecular Characterization of CTX-M Type B-Lactamases in Gram Negative Bacterial Strains Isolated from Hospitals, Lahore, Pakistan.

One of the principal mechanisms that contribute resistance to antibiotics is the production of extended spectrum beta lactamase (ESBL) in Gram negative bacteria. In the present study, molecular methods were used to evaluate the prevalence of the extended-spectrum beta-lactamase (ESBL)-encoding CTX-M gene among Gram negative bacterial strains. In total, 148 clinical samples were collected from different tertiary care hospitals of Lahore, Pakistan. Disc synergy diffusion method was used to detect the presence of ESBL production. Moreover, antibiotic resistance patterns and molecular detection of bla CTX-M ESBLs, were also studied. The pathogens isolated from the 148 samples included Escherichia coli (43%) followed by Klebsiella sp. (28%), Proteus sp. (18%) and Pseudomonas sp. (11%). In all 148 strains, 95 (64%) were ESBL producers while 53 (36%) were non ESBL producers. The strains which were phenotypically ESBL producers, bla CTX-M were found in 46% E. coli strains, while 50% Klebsiella sp. were harboring the gene. A high resistance rate was observed against cephalosporins (cefopodoxime 67%, cefoperazone 73%, cephalexin 63% sparaxin 61%). Lower resistance was observed against meropenem among all isolated bacterial strains. Genotypic detection of bla CTX-M genes by PCR revealed 46% of E. coli and 50% of Klebsiella strains harbored bla CTX-M gene. The present study showed that ESBLs producers were resistant to commonly used antibiotics. Similarly, bla CTX-M ESBL production is more prevalent in our clinical isolates.