微生物与生化技术杂志

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Prevalence, Genotyping of Escherichia coli and Pseudomonas aeruginosa Clinical Isolates for Oxacillinase Resistance and Mapping Susceptibility Behaviour

Manu Chaudhary and Anurag Payasi

In the present study, multi-drug resistant isolates of Escherichia coli and Pseudomonas aeruginosa were obtained from different clinical specimens and were subjected to molecular typing to detect the genes encoding oxacillinases in these isolates. Subsequently, antibacterial activity of drugs was tested against selected clinical isolates. Two hundred ninety six isolates including 98 of E. coli and 148 of P. aeruginosa were collected from clinical specimens of different centers across India. Out of 246, 123 isolates showed weak synergy for ceftazidime or cefepime and imipenem or clavulanate and were considered as oxacillinase producers. Polymerase chain reaction (PCR) was performed to identify the variants of oxacillinases genes. Our results show a great diversity of occurance of oxacillinase (OXA) genes among clinical isolates. OXA-48 and OXA-10 was more prevalent in both E. coli (32.6% OXA-48; 16.3% OXA-10) and P. aeruginosa (OXA-48 32.4%; 27.0%) as evident by PCR. The incidence of other OXA genes in E. coli and P. aeruginosa varied from 4.0 to 12.1%. Of the tested drugs, cefepime plus sulbactam was found to be the most efficacious antibacterial agents with 86.5 to 87.8% susceptibility. Cefepime plus tazobactam was second most active antibacterial agent with 72.2 to 73.5% susceptibility. Surprisingly, imipenem plus cilastatin showed susceptibility to less than 35% isolates. From the above results, it is evident that cefepime plus sulbactam has enhanced in vitro antibacterial activity compared to cefepime and imipenem plus cilastatin and tazobactam combination in oxacillinases. One significant finding of this study was that cefepime was found to be effective only against the isolates caring OXA-1 and OXA-2 but found to be resistant to OXA-10, OXA-23, OXA-24, OXA-48, OXA-51 and OXA-58 genes; whereas cefepime in combination with sulbactam was found to be the most effective against all of these OXA genes in comparison to tazobactam combination.