Antibiogram, antibiotic resistance genes and health risks of Listeria species from fruits and vegetables in selected locations in Nigeria.

BACKGROUND

Fresh produce is a vital vehicle for the transmission of foodborne pathogens, yet data from low- and middle-income countries on contamination levels and associated health risks remain scarce.

METHODS

This study provided an analysis of Listeria species contamination in 208 fruit and vegetable samples from major geopolitical regions in Nigeria. Conventional microbiological techniques and molecular methods were used for the analysis.

RESULTS

We reported a high prevalence (38.5%) and substantial bacterial loads (up to 8.33×10 2 CFU/25g) among the organically grown crops, with produce from Northern states exhibiting the highest contamination. Genetic characterisation revealed significant diversity, including novel strains and others closely related to global clones, confirming a resilient environmental presence. Importantly, antibiotic susceptibility testing uncovered alarming resistance rates to vancomycin (83.1%) and oxacillin (88.1%), with hierarchical clustering identifying distinct multidrug-resistant clusters. The presence of resistance genes ( vanA, vanB, tetL, tetM) and the virulence gene hly was confirmed. A quantitative microbial risk assessment (QMRA), incorporating this empirical data, estimated the annual probability of illness, highlighting high-risk produce-region combinations.

CONCLUSIONS

These findings demonstrate that fresh produce in Nigeria is a significant reservoir of pathogenic, antimicrobial-resistant L. monocytogenes, posing a serious public health threat. This study highlights the urgent need for targeted interventions, including enhanced agricultural water safety and strengthened surveillance of antimicrobial resistance, to mitigate risks and support evidence-based food safety policies in Nigeria and similar regions.