Prevalence of polymyxin-resistant bacterial strains in India: a systematic review and meta-analysis.

Introduction: Polymyxins, the cationic lipopeptide antibiotics, are the last line of therapeutics against the MDR Gram-negative bacterial (GNB) pathogens. Unfortunately, the rising cases of polymyxin-resistant strains from across the globe have adversely impacted their utility. While the molecular mechanisms responsible for developing polymyxin resistance (PolR) are largely understood, the prevalence of PolR strains in India has not been investigated systematically. The current study was undertaken to primarily determine the prevalence of PolR strains in India. Moreover, the extent of the spread of mobile colistin resistance (mcr) genes among the GNB strains in India was also determined.

Method: A systematic search for articles using the relevant inclusion and exclusion criteria was performed in the applicable databases for the period January 2015 to December 2023. The included 41 studies were subjected to a meta-analysis using the Comprehensive Meta-Analysis software (V4.0). Publication biases were assessed using funnel plots and Egger's regression analysis.

Result: Considering a total of 41 studies including 24 589 bacterial isolates the present meta-analysis found the rate of PolR bacteria in India to be at 15.0% (95% CI: 11.2 to 19.8). Among the Indian States, Tamil Nadu topped with the highest prevalence of PolR at 28.3%. Investigating the contribution of the mcr genes, it was observed that among the PolR strains, 8.4% (95% CI: 4.8 to 14.3) were mcr positive.

Conclusion: The study determined the prevalence of PolR strains in India at 15.0%, which is higher than that of the global average at 10%. The study also determined that 8.4% of the PolR strains carried the mcr genes. The mcr-positive strains reported from India could be an underestimation of the actual numbers due to the non-inclusion of mcr screening in many previous studies. This study provides insight into the state of the PolR situation in India, which may be useful to develop a monitoring strategy to contain the spread of such strains and preserve the efficacy of the polymyxins.