The emergence and spread of carbapenem-resistant Gram-negative bacteria is a worldwide emerging public health threat responsible for large number of nosocomail infections. Metallo-b-lactamases including IMP, VIM, and NDM as well as carbapenem hydrolyzing class D b-lactamase (OXA-48 like) are the predominant types that confer resistance to Carbapenem group of antibiotics. The aim of this study was to identify the carbapenemase encoding genes among Gram negative bacteria isolates. 42 isolates were identified depending on routine morphological tests followed by species identification using the VITEK 2 system. The 16S rDNA gene sequence was used for confirmation of the detection of Enterobacteriaceae and Pseudomonas aeruginosa. Antimicrobial susceptibility testing was performed using VITEK 2 system. For phenotypic detection of carbapenemase activity, modified carbapenem inactivation method (mCIM) was performed. The carbapenemases encoding genes (blaIMP, blaSPM, blaVIM, blaNDM, blaKPC, blaBIC, blaOXA, blaAIM, blaSIM, blaGIM, blaDIM) were amplified by PCR and the amplified products were sequenced. Forty two Gram-negative bacteria isolates including 25 of P. aeruginosa (59.5%) and 17 of Enterobacteriaceae family (40.4%) were identified. According to PCR-based method results, carbapenemase gene blaOXA-48 was detected in 31(73.8%) of isolates, blaVIM in 23 (54.7%) and blaNDM in 2(4.76%) of isolates. Twelve (28.5%) of isolates harbored a combination of blaOXA-48 and blaVIM, (2.4%) coexistence blaOXA-48 and blaNDM gene and (2.4%) of isolates harbored a blaOXA-48, blaVIM and blaNDM genes. No other carbapenemase genes were identified. Based on the present study, it was concluded that the high prevalence was in blaOXA-48 gene, followed by blaVIM gene among carbapenemase-producing Gram-negative bacteria isolates.
Enterobacteriaceae Pseudomonas aeruginosa, Carbapenemases.
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