Mcr-1 expression in progression of colistin resistance gram negative bacilli of clinical specimens derived from Intensive Care Units, wards and hospital setting of Deccan Eco Region of Southern India

The involvement of the "mcr-1" gene in the transmission of this colistin-resistant gram-negative bacteria (GNB) poses a serious threat to current clinical management of human community acquired infections. Current study aim is to determine the prevalence of colistin resistance clinical isolates obtained from patients of ICUs, wards of a tertiary hospital, and to detect the ‘mcr-1’ gene using real-time PCR assay. A total of 2032 different clinical specimens were processed at Microbiology laboratory. From these, 1852 gram-negative isolates further processed for antimicrobial susceptibility test for Colistin resistance through minimum inhibitory VITEK method. Colistin resistant strains were further screened for mcr-1 gene using polymerase chain reaction (PCR). Among the total clinical samples, 91.14% isolates were Gram-negative bacilli. The most predominant isolate among Gram-negatives was K. pneumonia, and E. coli. 20% of E. coli and 25% of K. pneumonia were resistant to carbapenem. From the 1853 GNB isolates, 31 colistin resistance isolates were identified. Among 31 colistin resistant GNB, 41.94% (13/31) were Klebsiella sps, 25.81% (8/31) were E.coli, 19.36 % (6/31) were Pseudomonas sps, 6.45 %(2/31) were Acinetobacter Sps, and 6.45% (2/31) were Enterobacter species respectively. In MIC assay, majority of E. coli and K. pneumonia confirmed as colistin resistant at MIC≥4 µg/ml. K. pneumoniae had a higher prevalence of colistin resistance than compared to E. coli (0.71%vs 0.42%, p<0.05). Overall, the prevalence of colistin resistance was 1.637% (31/1852) and the acquisition rate of ‘mcr-1’ was 6.45% (2/31). Resistance to drug colistin and its isolation of mcr-1 indicate further emergency in infection management. Hence, extensive surveillance, formulation and implementation of effective strategies, and extension of diagnostic facilities can be some remedies to cope with this global crisis.