Detection of mobilized colistin resistance (MCR) gene from livestock wastewater samples

Chua, Amy Jia Xuan (2022) Detection of mobilized colistin resistance (MCR) gene from livestock wastewater samples. Final Year Project, UTAR.

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Abstract

The prolong extensive use of broad-spectrum antibiotics and misuse of antibiotics for numerous purposes have given rise to the rapid emergence of multi drug-resistance (MDR) bacteria. Colistin was once used as the last resort for treating infections caused by these MDR gram-negative bacteria, until the plasmid-mediated mobilized colistin resistance (mcr) gene which allowed the bacteria to resistant to colistin emerged. Given the significant roles of colistin in clinical use, the objectives of this research were to isolate, detect and determine the minimum inhibitory concentration (MIC) of colistin and antibiotics susceptibility of mcr-harbouring bacteria from livestock wastewaters. Livestock wastewater samples were collected from water contaminated with chicken faeces and water used to wash pork intestines and chicken intestines respectively. Gram-negative lactose-fermenting bacteria were isolated using MacConkey agar and the presence of mcr gene was detected using polymerase chain reaction (PCR). The MICs of mcr-positive isolates were studied using broth microdilution method and the antibiotic resistance profile was determined using Kirby-Bauer disc diffusion method. A total of 43 gram-negative lactose fermenting bacteria were isolated from the samples. Among the isolates, mcr-1 gene was detected in 7 out of 43 (16.28 %) isolates, mcr-3 gene was detected in iii 1 out of 43 (2.33 %) isolates, and no mcr-5 was detected in all the isolates. The results of broth microdilutions showed that the MIC of mcr-positive bacteria ranged between 1 µg/mL to 4 µg/mL. Besides, all the isolates harbouring mcr-1 gene were found to co-resistant to 4 to 5 other antibiotics classes while the isolate harbouring mcr-3 was found to co-resistant to another antibiotic class used in the study, suggesting that the mcr-1 positive isolates were multi-drug resistance while the mcr-3 positive isolate was not multi-drug resistance.

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