ANTIMICROBIAL SUSCEPTIBILITY PROFILE OF LISTERIA SPECIES ISOLATED FROM READY-TO-EAT FOOD SAMPLES IN FOUR AREA COUNCILS OF ABUJA, NIGERIA.

Abstract

Listeria species, particularly Listeria monocytogenes, pose a significant public health threat due to their ability to contaminate ready-to-eat (RTE) foods and develop resistance to commonly used antibiotics. This study aimed to evaluate the antibiotic susceptibility profiles of Listeria monocytogenes (n = 31), L. ivanovii (n = 18), and L. seeligeri (n = 10) isolated from various RTE foods in Abuja, Nigeria. The isolates were tested against a panel of twelve antibiotics using the disc diffusion method following Clinical and Laboratory Standards Institute (CLSI) guidelines. The results showed that all Listeria species exhibited complete resistance (100%) to Bacitracin and near-complete resistance to Azithromycin, especially L. monocytogenes (96.8%). However, complete sensitivity (100%) was observed to Cloxacillin across all species. L. monocytogenes displayed variable sensitivity, with highest susceptibility to Erythromycin (51.6%) and Tetracycline (41.9%), but lower sensitivity to Levofloxacin (29.0%) and Penicillin G (29.0%). L. ivanovii exhibited high sensitivity to most antibiotics, notably Tetracycline (94.4%), Penicillin G (94.4%), and Erythromycin (94.4%). L. seeligeri showed moderate sensitivity to most antibiotics but recorded 50% resistance to Gentamicin. Overall susceptibility profile shows that all 59 isolates were susceptible to cloxacillin (100%), tetracycline (64.4%), and cotrimoxazole (55.9%). But moderately effective to gentamicin (44.1%), ciprofloxacin, amoxicillin/clavulanic acid, and penicillin G each had (50%-47%), clindamycin (49.2%) and levofloxacin (44.1%). Ineffective antibiotics were bacitracin (100%) and azithromycin (94.9%) The emergence of resistance among Listeria species in RTE foods highlights a growing concern in food safety and public health. These findings underscore the need for routine monitoring of antibiotic resistance in foodborne pathogens and implementing stricter food safety protocols to limit consumer exposure. Moreover, the resistance patterns observed suggest the need for targeted antibiotic stewardship and highlight the importance of the One Health approach in addressing antimicrobial resistance. Future studies should explore the genetic mechanisms underlying these resistance patterns to better inform control strategies.

Keywords: Listeria monocytogenes, antibiotic resistance, ready-to-eat food, Nigeria, public health, antimicrobial susceptibility.