Plasmid-Borne Mobile Colistin Resistant Gene (Mcr-1) Detection and Multidrug Resistant Bacteria Isolated from Some Abattoir Environments in Benin City, Edo State, Nigeria

Antibiotics resistance is an increasing public health challenge globally, and very recently, global attention has focused on colistin, which is  termed “last resort antibiotics”. This study was aimed at investigating the prevalence of plasmid-borne mobile colistin resistant and multidrug resistant bacteria from 6 major abattoirs located in Benin City, Edo State, Nigeria. Two hundred and eighty-eight samples from  fresh water, wastewater, utensils, and handlers were obtained over a 6-months period. Mean mesophilic aerobic bacteria (MAB) and thermotolerant coliform bacteria (TCB) were determined by pour plate method, while the indoor air of the abattoirs was sampled using  passive sedimentation technique. Bacterial isolates were identified by morphological, biochemical and 16S rRNA analysis. Phenotypic detection of colistin-resistance as well as multi-drug resistant profile of all isolates was done by the modified Kirky Bauer method. The  presence and/or absence of colistin-resistance gene (mcr-1 to mcr-8) were investigated by polymerase chain reaction. The MAB ranged from 0.3 ± 0.0 cfu/m3 in indoor air from both Holy Ghost B and Bob Izua abattoir to 2.6 ± 0.3 cfu/ml in wash water from Holy Ghost A  abattoir, while the TCB ranged from 0.0 ± 0.0 cfu/ml in wastewater from Lawal and Sons abattoir to 0.6 ± 0.1 cfu/ml in wash water from Osazee abattoir. A total of 149 bacterial isolates, belonging to 6 different species (Pseudomonas aeruginosa PA01, Enterobacter ludwigii  EN-119, Providencia stuartii PRV00010, Klebsiella quasipneumoniae strain KqPF26, Enterococcus saccharolyticus ATCC 43076 and Provincia  rettgeri strain AR_0082) were obtained with the majority (>90%) being multidrug resistant. Seven (4.7%) of the isolates were  phenotypically resistant to colistin, while only 3 harbored the mcr-1 gene. This result shows that plasmid-borne colistinresistant and  multidrug resistant bacteria are prevalent in abattoir environment located in Benin City, Edo State, Nigeria. This is an indication that  abattoir facilities could be a source of human exposure to colistin resistant bacteria, and efforts must be made at reducing the high  dependence of antibiotics in farm animals.