Occurrence, Antimicrobial Susceptibility and Biofilm Production in Listeria ‎monocytogenes Isolated from Pork and other Meat Processing Items at Oko-‎Oba Abattoir, Lagos State, Nigeria‎

Unhygienic slaughtering practices are associated with meat contamination by pathogens including Listeria monocytogenes. This study investigated the occurrence, bacterial load, antimicrobial susceptibility and biofilm formation of L. monocytogenes in pork, slaughter facilities and water from Oko-Oba abattoir, Lagos State, Nigeria. A total of 216 samples; 146, 30, 20 and 20 from pork, water, table swabs and knife swabs respectively were collected for bacteriological analysis. Listeria selective media was used to isolate and characterise L. monocytogenes, antimicrobial susceptibility of the isolated bacteria was also determined. Biofilm production by the isolates for periods of 12, 24 and 36 hours were evaluated. Glucose, ethanol and crystal violet binding assay were used as nutrient, stressor and indicator respectively. The occurrence of L. monocytogenes in pork, water samples, table and knife swabs were 64.5%, 75%, 90% and 95% respectively, while overall prevalence was 73.3%. The mean load per gram were 3.78 ± 2.85, 4.27 ± 2.54, 5.60 ± 1.95 and 5.52 ± 1.41 (p ˂ 0.05) for pork, water table and knife swab samples, respectively. Fifty five percent of the isolates exhibited multidrug resistance (MDR) patterns to erythromycin (55%), tetracycline (55%), augmentin (85%), amoxicillin (90%), cotrimoxazole (95%), and cloxacillin (100%). The isolates produced biofilms at different concentrations of glucose and ethanol with the highest concentrations of biofilm produced at 36 hours. There were significant differences in mean biofilm values produced by the isolates. The occurrence of L. monocytogenes and the bacterial load in different samples are of economic and public health importance. Hygienic meat production from the abattoir could prevent contamination of pork by L. monocytogenes.