Isolation And Molecular Detection Of Virulence Genes Of Listeria Monocytogenes From Ready-To-Eat Foods In The Federal Capital Territory Abuja, Nigeria

Abstract

Listeria monocytogenes is a Gram-positive, facultative intracellular food-borne pathogen of significant public health concern, especially due to its presence in ready-to-eat (RTE) food samples. This study determined the prevalence of Listeria monocytogenes in RTE foods across four area councils (Gwagwalada, Bwari, Kuje, and Abaji) in Abuja, Nigeria. A cross-sectional study was conducted, and a total of 225 RTE food samples, comprising tsire (grilled meat), balangu (roasted meat), fermented unpasteurized milk (nono), and soft cheese (wara), were collected
proportionately. Samples were processed using standard microbiological methods for isolation, followed by biochemical identification of Listeria monocytogenes and multiplex PCR targeting the virulence genes (iap, inlA, and hylA) was used for molecular identification. The data were subjected to statistical analysis to determine the level of significance between variables. The percentage of positive results was calculated at each stage of detection. The results revealed that out of 225 samples, 59 (26.2%) were positive for Listeria. Spp. by culture, of these, 31 (13.8%) were identified as Listeria monocytogenes through biochemical tests, while 19 (8.4%) were confirmed by
multiplex PCR to have the Listeria monocytogenesvirulence gene. Abaji area council recorded the highest prevalence rate (48.9%) across all stages. In contrast, Gwagwalada had the lowest prevalence (14.7%). Chi-square tests revealed a statistically significant association (p< 0.05) between the area councils and the detection of Listeria monocytogenes using three diagnostic test outcomes. Two-way analysis of variance also showed a statistically significant difference in the level of Listeria contamination amongst the different RTE foods. The prevalence of Listeria across food types in the various area councils revealed that soft cheese had the highest rate (37.3%), followed
by unpasteurized milk (30.5%), balangu (20.3%), and tsire (11.9%). Amongst the Listeria spp. isolated, Listeria monocytogenes was the most isolated with 13.3%, followed by Listeria ivanovii (8.0%), and Listeria seeligeri (4.4%). Only 8.4% of the Listeria monocytogenes isolates were confirmed by multiplex PCR, from which the virulence genes, iap and inlA, with characteristic band sizes of 131bp and 255bp, respectively, were detected. This study confirms that Listeria contamination of RTE foods in Abuja remains a serious public health concern and a threat to food safety. RTE food should be properly processed and handled to minimise the risk of microbial contamination and foodborne illness. Regular microbiological testing and monitoring should be conducted to ensure
product safety and quality.