The Occurrence of Colistin Resistance in Potential Lactic Acid Bacteria of Food‑Producing Animals in India.

The overuse of colistin, the last-resort antibiotic, has led to the emergence of colistin-resistant bacteria, which is a major
concern. Lactic acid bacteria which are generally regarded as safe are known to be reservoirs of antibiotic resistance that
possibly pose a threat to human and animal health. Therefore, this study assessed the prevalence of colistin antimicrobial
resistance in livestock in India, that is lactic acid bacteria in healthy chickens, sheep, beef, and swine of Mysore. Diverse
phenotypic and genotypic colistin resistance were examined among the lactic acid bacterial species (n = 84) isolated from
chicken (n = 44), sheep (n = 16), beef (n = 14), and swine (n = 10). Hi-comb, double-disk diffusion tests, Minimum Inhibitory
Concentration (MIC), and biofilm formation were assessed for phenotypic colistin resistance. Specific primers for
colistin-resistant genes were used for the determination of genotypic colistin resistance. Around 20%, 18%, and 1% were
colistin-resistant Lactobacillus, Enterococcus, and Pediococcus species, respectively. Among these, 66.67% exhibited MDR
phenotypes, including colistin antibiotic. The identified resistant isolates are Levilactobacillus brevis LBA and LBB (2),
Limosilactobacillus fermentum LBF (1), and Pediococcus acidilactici CHBI (1). The mcr-1 and mcr-3 genes were detected
in Levilactobacillus brevis LBA, LBB, and Pediococcus acidilactici CHBI isolated from chicken and sheep intestines
respectively. The study identified colistin resistance determinants in lactobacilli from food animals, emphasizing the need
for enhanced surveillance and monitoring of resistance spread. These findings underscore colistin resistance as a significant
medical concern and should be integrated into India’s ongoing antimicrobial resistance monitoring programs.