Study on the Mobile Colistin Resistance (mcr-1) Gene in Gram-Negative Bacilli in a Rural Tertiary Care Hospital in Western Maharashtra.

Background: Colistin, a last-resort antibiotic for treating multidrug-resistant Gram-negative bacterial infections, has increased resistance as a result of the emergence of the gene. The 1gene, which confers colistin resistance, is often carried on plasmids, facilitating its spread by horizontal gene transfer among bacterial populations. The rising prevalence of 1mediated resistance poses significant challenges for infection control and treatment efficacy. This study aimed to detect and investigate the prevalence of the 1 gene among Gram-negative bacilli isolated from clinical specimens in a rural tertiary care hospital and to analyze the plasmid-mediated mechanisms of colistin resistance.

Materials And Methods: A cross-sectional study was conducted over two years at Krishna Institute of Medical Sciences, Karad. Gram-negative bacilli were isolated from clinical specimens and identified using standard methodology. Antimicrobial susceptibility testing was performed by using the Vitek-2 Compact (bioMerieux, Marcy-l'Étoile, France) method and the colistin-resistance broth microdilution method (BMD). Polymerase chain reaction (PCR) was done for the presence of 1 gene in colistin-resistant isolates.

Results: Out of 359 Gram-negative bacilli isolates, 93 (25.90%) demonstrated resistance to colistin. Among these resistant strains, the -1 gene was identified in 13 (13.97%) of the isolates. The gene was predominantly found in (8, 61.53%), followed by (3, 23.07%) (2, 15.38%) among the 13 isolates. Out of the various specimens received, 1 gene was found in endotracheal tube (4, 30.76%), urine (4, 30.76%), pus (3, 23.07%), sputum (1, 7.69%), and blood (1, 7.69%). Colistin minimum inhibitory concentration (MIC) value for these resistant isolates ranged from 4 to 16 µg/ml.

Conclusion: The study highlights a significant prevalence of 1 plasmid-mediated colistin resistance gene among Gram-negative bacilli in the hospital. This possibly highlights the frequent misuse of colistin in animal husbandry from this rural area. The findings underscore the importance of monitoring resistance patterns and implementing stringent infection control measures.