Poultry chicken gut-bacteria carry high extent of colistin resistant mcr-1 gene in Bangladesh

Abstract

Background: The indiscriminate uses of antimicrobials in either human or animal husbandry generate selection pressure to develop resistance in diverse microbial populations. Colistin is a polymyxin group antibiotic used for the treatment of critical human infections by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and veterinary healthcare. In recent years, colistin usage has been expanded considerably in Argo, fishery, and food animal farming in Bangladesh. This study investigated phenotypic colistin-resistance and the prevalence of colistin-resistance mcr-1 gene in bacterial isolates from droppings of poultry chickens and household native chickens. Methods and materials: A cross-sectional study was conducted and colistin usage history to chickens was collected by a structured questionnaire. Bacteria were isolated from chicken droppings by inoculating on different selective culture media. The purified bacterial colonies were identified by conventional biochemical procedures followed by a rapid biochemical-test kit (API 20E, BioMérieux, Durham, NC). A part of bacterial identification was validated further by genotyping using 16S rDNA analyses. The colistin susceptibility of the isolates were determined by disk-diffusion and minimal inhibitory concentration (MIC) measurement. mcr-1 gene was detected by polymerase chain reactions (PCR) and confirmed by sequence blasting. Results: Overall 39.6% (59/159) isolates showed colistin-resistant by disk-diffusion assessment. The resistance prevalence was significantly higher in poultry-chicken isolates (48.5%, 48/99) than in native-chicken isolates (22%, 11/50; p = 002). All the resistant isolates showed MIC level, between >8 μg/mL to >256 μg/mL. Likely, the mcr-1 gene was detected more in poultry gut bacteria (34%) than in native-chicken isolates (14%, p = 0.02). mcr-1 appeared significantly associated with phenotypic colistin-resistance phenomena (p < 0.001). Previous colistin usage yielded a substantially higher proportion of mcr-1 in bacteria (p = 0.06). Conclusion: mcr-1 gene circulates in bacteria isolated from both poultry chicken and native chicken. Higher acquisition of mcr-1 in bacteria was associated with colistin-usage for chickens. The increased mcr-1 prevalence may increase the risk of critical human disease transmission. Specifically, mcr-1 can enter humans via zoonotic infections from poultry-human interface, which poses a big threat to public health.