Phenotypic and Molecular Characterisations of Coliforms in Tomato Fruits from Ondo Metropolis Markets

Abstract

Background: Tomato fruits are widely consumed in Nigeria but are susceptible to microbial contamination during cultivation, transportation and marketing. Aim: Tomatoes (Solanum lycopersicum) are widely consumed in Nigeria and constitute a major component of daily diets. However, their susceptibility to microbial contamination during cultivation, transportation and marketing poses serious public health concerns. This study investigated the phenotypic traits, molecular characterisations and antibiotic susceptibility of coliforms isolated from both ripened and rotten tomato fruits sold in selected markets within Ondo Metropolis. Methodology: Both rotten and ripened tomato samples were collected from five major markets in Ondo Metropolis and analysed using standard microbiological procedures. Coliforms were isolated and identified through cultural, morphological and biochemical tests, and were further characterised using molecular identification by extracting DNA from bacterial cells and amplifying the gene of interest (16S rRNA) with primers to identify the proposed coliforms. Antibiotic susceptibility testing was carried out using the disc diffusion method. Results: The microbial load of the rotten tomatoes was higher than that of the ripened tomatoes. The results revealed that the microorganisms in tomato samples across all markets were: Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa and Bacillus spp. Molecular analysis confirmed the identity of the isolates, with high sequence similarity (>99%) to reference strains in the National Center for Biotechnology Information database. All microorganisms isolated demonstrated resistance to at least one antibiotic tested. Pseudomonas aeruginosa exhibited the highest susceptibility to ciprofloxacin, gentamicin and tetracycline. Conclusion: The study provided additional information on the coliforms found in tomatoes and highlighted the need for improved hygiene practices, effective monitoring of fresh produce and stronger antimicrobial stewardship policies in Nigeria.