Molecular Identification of Escherichia coli Strains from Locally Produced Soy Milk Sold in Enugu Metropolis

Abstract

Soy milk is a nutritious plant-based beverage widely consumed because of its affordability, health benefits and suitability as an alternative to dairy milk. However, its rich nutrient composition makes it highly susceptible to bacterial contamination when it is produced under poor hygienic conditions. This study was conducted to identify Escherichia coli in locally produced soy milk sold in selected markets in Enugu metropolis. A total of fifty (50) soy milk samples were collected from five markets in Enugu metropolis and analysed using standard microbiological, biochemical and molecular techniques. The mean total viable bacterial count ranged from 1.1 × 10⁶ CFU/mL in Ogbete Market to 2.6 × 10⁶ CFU/mL in New Market, while Mayor, Garriki and Eke-Agbani markets recorded 2.1 × 10⁶, 1.9 × 10⁶ and 1.7 × 10⁶ CFU/mL, respectively. Escherichia coli was detected in 16 (32%) of the 50 samples examined, with occurrence rates of 50%, 40%, 30%, 30% and 10% in New, Mayor, Eke, Garriki and Ogbete markets, respectively. Amplification of the 16S rRNA gene revealed closest matches to Escherichia coli reference strains E94, ET201, MS20674 and CE2050. Sequence similarity among the isolates and reference sequences ranged from 95.22% to 98.56%. Phylogenetic analysis demonstrated close genetic relatedness among the isolates while also indicating genetic diversity. The findings indicate poor bacteriological quality of commercially sold soy milk and highlight the public health risks associated with contaminated products. Improved hygiene, routine microbial surveillance and strict food-safety measures are recommended to enhance consumer safety and product quality.