Publication
High abundance of the colistin resistance gene mcr-1 in chicken gut-bacteria in Bangladesh
Publisher:
Springer Science and Business Media LLC
Date:
14-10-2020
DOI:
10.1038/S41598-020-74402-4
Abstract: Colistin is considered a last-resort reserved drug for the treatment of critical human infections by Gram-negative bacteria. Phenotypic colistin-resistance is strongly associated with plasmid-mediated mobile colistin resistance ( mcr ) genes. The mcr -bearing Enterobacteriaceae have been detected in many countries from environments, animals, and humans. This study investigated phenotypic colistin-resistance and the distribution of mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes in chicken-gut bacteria in Bangladesh. Bacteria were isolated from poultry- and native-chicken droppings, and their susceptibilities to colistin were determined by agar dilution and E-test minimal inhibitory concentration (MIC) measurements. Multiplex polymerase chain reactions detected mcr-1 to mcr-5 genes. Overall, 61.7% (92/149) of the isolates showed colistin resistance by agar dilution assessment (MIC 2.0 μg/mL). The phenotypic resistance was observed considerably higher in poultry-chicken isolates (64.6%, 64/99) than in native-chicken isolates (56%, 28/50 p = 0.373). All the resistant isolates showed MIC levels between 2 and 128 μg/mL. The mcr -genes ( mcr-1 and mcr-2 combined ) were detected more in poultry gut bacteria (36.4%) than native-chicken isolates (20%, p = 0.06). Despite bacteria sources, mcr- genes appeared to be significantly associated with phenotypic colistin-resistance phenomena ( p 0.001). Prior colistin usage led to a substantial increase in the proportion of bacteria with mcr- genes and phenotypic resistance ( p 0.001).