Occurrence and Antibiotic Susceptibility of Listeria Species Isolated from Ready-to-eat Mixed Vegetable Salad Sold in Fast Food Eateries in Port Harcourt

Abstract

Aims: The study aim to evaluate the occurrence and antibiotic susceptibility of Listeria species in ready-to-eat (RTE) mixed vegetable salad sold in selected fast food eateries in Port Harcourt. Study Design: This work was based on a completely randomized design with two replications and the average values calculated for mean comparison. Place and Duration of Study: The study was done in Food and Industrial Microbiology Laboratory, Department of Microbiology, University of Port Harcourt, Nigeria, between June and December, 2018. Methodology: The study evaluated the occurrence and antibiotic susceptibility of Listeria species isolated from 100 samples of ready-to-eat (RTE) mixed vegetable salad sold in selected fast food eateries in Port Harcourt, using standard procedures involving Fraser broth, polymycin? acriflavin lithium chloride ceftazidime aesculin mannitol (PALCAM) agar, Mueller Hinton agar and multiple antibiotic disc. Results: Of the 100 samples examined, 14% were positive for Listeria species. The Listeria isolates were identified on the basis of their physiological and biochemical characteristics as L. innocua (56.52%), L. welshimeri (34.78%) L. grayi (8.70%). The antibiotic susceptibility results reveal varying resistance against gentamicin (8.69%), augmentin (66.67%), amoxicillin (58.33%), erythromycin (25.00%), tetracycline (45.83%), cotrimoxazole (37.50%), chloramphenicol (41.67%) and cloxacillin (62.50%). Conclusion: Although no L. monocytogenes was detected in the samples examined, the presence of L. innocua often reported as masking L. monocytogenes in growth media is a source of concern to public health experts and a potential threat to consumers.