Assessment of resistance profiles and virulence genes in Escherichia coli from fresh vegetables: implications for food safety and consumer health in Ogun State, Nigeria.

Abstract

Purpose: Fresh vegetables are essential human dietary components but are increasingly implicated in foodborne infections caused by Escherichia coli. Contamination may occur during cultivation, irrigation, handling, and retail display, and the presence of pathogenic or antimicrobial-resistant E. coli poses significant public health risks. Despite widespread vegetable consumption in Ogun State, Nigeria, limited data exist on the resistance and virulence characteristics of E. coli in these foods. This study therefore assessed antimicrobial resistance profiles and virulence genes in E. coli isolated from tomatoes, carrots, and cucumbers sold across three senatorial districts of Ogun State.

Method: A cross-sectional survey was conducted between March and October 2023, yielding 509 vegetable samples collected aseptically during three visits. Samples were enriched, cultured on MacConkey agar, and identified using standard microbiological methods. Thereafter, antimicrobial susceptibility testing was performed using the Kirby-Bauer disc diffusion method. Genomic DNA was extracted from the microbe, followed by Polymerase Chain Reaction (PCR) to detect key virulence (stx1, stx2, eae) and resistance (blaSHV, blaTEM, blaCTX, NDM, IMP, KPC, OXA-48) genes.

Results: Of the 509 vegetables analysed, 73 (14.4%) tested positive for E. coli: 34 (14.4%) from tomatoes, 27 (24.1%) from carrots, and 12 (7.5%) from cucumbers. Carrots from Ogun Central had an E. coli contamination rate of 9.8% (11/112), while cucumbers from Ogun East had a contamination rate of 1.3% (2/160). Among 34 E. coli isolates confirmed and recovered from the vegetables, 12 originated from Ogun Central, 9 from Ogun East, and 13 from Ogun West. Isolates showed resistance to all antibiotics except gentamicin and levofloxacin. Virulence genes stx1 and stx2 were detected in 3 and 2 isolates, respectively. Also, 47% of isolates carried resistance genes, and 15% carried virulence genes.

Conclusion: Fresh vegetables across the three senatorial districts of Ogun State were contaminated with E. coli, with 15% of isolates carrying virulence genes and 47% carrying antimicrobial resistance genes. The low detection of virulence genes indicates relatively low pathogenic potential, as higher levels typically signal greater infection risk. However, the presence of both virulence and resistance genes still highlights important public health concerns. These findings emphasize the need for improved farming hygiene, stricter antimicrobial regulation, and stronger surveillance.