Culture-independent quantitative PCR detected mobilized colistin resistance genes (mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5) in chicken-gut contents in Bangladesh

Al Asad, Mamun and Shuvo, Md Sarower Hossen and Mitu, Shomaia Yasmin and Sumia and Zihadi, Md Asief Hossain and Shanta, Ayasha Siddique and Islam, Nahidul and Nahar, Shamsun and Godman, Brian and Islam, Salequl (2024) Culture-independent quantitative PCR detected mobilized colistin resistance genes (mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5) in chicken-gut contents in Bangladesh. Sci, 6 (4). 76. ISSN 2413-4155 (https://doi.org/10.3390/sci6040076)

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Abstract

Inappropriate antimicrobial uses in food animal farming propel antimicrobial resistance (AMR) that affects all health domains. Colistin is a ‘Reserve’ antibiotic for human treatment to be conserved for multidrug-resistant pathogens; however, it is being used as an animal growth promoter in many developing countries. The evolution of mobilized colistin resistance (mcr) gene-mediated colistin resistance has been reported to be associated with rampant colistin uses. This study investigated current variants of mcr gene in chicken gut contents in Bangladesh. A cross-sectional study was designed to assess mcr-1 to mcr-5 genes in 80 fresh poultry droppings from commercial poultry farms and 40 poultry droppings from household farms. DNA was extracted from each poultry dropping using commercial kits (Qiagen GmbH, Hilden, Germany). Real-time quantitative polymerase chain reaction (RT-qPCR) was employed by the qTOWER3 thermal cycler (Analytik Jena GmbH, Jena, Germany) to analyze the mcr gene variants in the extracted DNA. This study observed that 47.5% (57/120) of the samples exhibited the presence of at least one mcr gene out of the five variants investigated. Individual detection of mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes were 42.5% (51/120), 2.5% (3/120), 1.7% (2/120), 5% (6/120), and 9.2% (11/120), respectively. Co-carriage of two or more genes was found in over 10% (10/57) of samples. The triple occurrence of mcr genes was identified in three samples with the combination of mcr-1+mcr-2+mcr-4, mcr-1+mcr-3+mcr-5, and mcr-1+mcr-4+mcr-5. Overall, a significantly higher number of mcr genes were identified in commercial farm chicken droppings compared to household chicken droppings (p=0.007). The existence of mcr genes in poultry feces in Bangladesh emphasizes the importance of proper poultry waste disposal and good hygiene practices in poultry livestock and its value chain. The potential impacts of environmental ARGs should be considered in national and global policy documents. An integrated and combined approach to the One Health concept should be applied in all domains to understand and control the environment’s role in the evolution and transmission of AMR.

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