Enterobacteriaceae quality and diversity of vegetables sold in the Johannesburg Metropolis

Abstract

The contamination of street vended vegetables may occur through the usage of manure and contaminated irrigation water, and the consumption of these vegetables, such as ready-to-eat salads, can cause foodborne diseases in consumers. The objective of this study was to investigate the Enterobacteriaceae diversity in vegetables sold at informal markets in the Johannesburg Metropolis. A total of 201 vegetable samples were purchased from randomly selected street vendors from different regions in the Johannesburg Metropolis and analysed for aerobic growth count and Enterobacteriaceae contamination using Plate Count Agar (PCA), and violet red bile glucose agar (VRBGA), respectively. The diversity of bacterial isolates was analysed using sequencing and phylogenetic analysis. The aerobic bacterial growth counts of vegetables from all the regions ranged from 7.66(±0.759) to 8.37(±0.347) log10 cfu/g and the mean aerobic growth counts of vegetables from Soweto and Yeoville were significantly different (p ≤ 0.05) from those of the other regions, but were not significantly (p > 0.05) different across different vegetable types. The Enterobacteriaceae growth counts in vegetables from all the regions ranged from 5.05 (±0.647) to 5.45 (±0.693) log10 cfu/g. The mean Enterobacteriaceae growth counts of vegetables were not significantly (p > 0.05) across each region and different vegetables types. The predominant Enterobacteria genera were Serratia (35%), followed by Hafnia (21%), Aeromonas (17%), and Pseudomonas (5%). In conclusion, this study shows that the vegetables sold at the informal markets in the Johannesburg Metropolis have high aerobic bacterial growth and Enterobacteriaceae contamination due to poor hygiene practices. The dominant Enterobacteriaceae genera isolated are Aeromonas, Hafnia, Serratia, and Pseudomonas, which could be opportunistic pathogens. It is recommended that the Department of Health improves vending and sanitation facilities, to prevent cross contamination.