Mobile colistin-resistant gene; mcr-1, mcr-2, mcr-3 identified in diarrheal pathogens among infants, children, and adults in Bangladesh : implications for the future

Sarker, Shafiuzzaman and Neeloy, Reeashat Muhit and Habib, Marnusa Binte and Urmi, Umme Laila and Al Asad, Mamun and Mosaddek, Abu Syed Md and Khan, Mohammad Rabiul Karim and Nahar, Shamsun and Godman, Brian and Islam, Salequl (2024) Mobile colistin-resistant gene; mcr-1, mcr-2, mcr-3 identified in diarrheal pathogens among infants, children, and adults in Bangladesh : implications for the future. Antibiotics, 13 (6). 534. ISSN 2079-6382 (https://doi.org/10.3390/antibiotics13060534)

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Abstract

Colistin is a last-resort antimicrobial for treating multidrug-resistant Gram-negative bacteria. Phenotypic colistin resistance is highly associated with plasmid-mediated mobile colistin resistance (mcr) genes. mcr-bearing Enterobacteriaceae have been detected in many countries, with the emergence of colistin-resistant pathogens a global concern. This study assessed the distribution of mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes with phenotypic colistin resistance in isolates from diarrheal infants and children in Bangladesh. Bacteria were identified using the API-20E biochemical panel and 16s rDNA gene sequencing. Polymerase chain reactions detected mcr gene variants in the isolates. Their susceptibilities to colistin were determined by agar dilution and E-test by minimal inhibitory concentration (MIC) measurements. Over 31.6% (71/225) of isolates showed colistin resistance according to agar dilution assessment (MIC > 2 μg/mL). Overall, 15.5% of isolates carried mcr genes (7, mcr-1; 17, mcr-2; 13, and mcr-3, with co-occurrence occurring in two isolates). Clinical breakout MIC values (≥4 μg/mL) were associated with 91.3% of mcr-positive isolates. The mcr-positive pathogens included twenty Escherichia spp., five Shigella flexneri, five Citrobacter spp., two Klebsiella pneumoniae, and three Pseudomonas parafulva. The mcr-genes appeared to be significantly associated with phenotypic colistin resistance phenomena (p = 0.000), with 100% colistin-resistant isolates showing MDR phenomena. The age and sex of patients showed no significant association with detected mcr variants. Overall, mcr-associated colistin-resistant bacteria have emerged in Bangladesh, which warrants further research to determine their spread and instigate activities to reduce resistance.