Isolation and identification of bacterial microorganisms with public health implications in tomatoes sold in Pietermaritzburg, KwaZulu-Natal

N.C. Mbili, S.P.N. Shude
Apart from fruits and vegetables being considered as nutritious and healthy foods, a rising concern of these foods being vectors for human pathogens to their human hosts exists. This study was aimed at identifying and isolating bacterial pathogens that pose a threat to human health from tomatoes sold in Pietermaritzburg, South Africa. Forty tomato samples were collected from two sources (supermarket and street vendor). This resulted in four batches (AR, AO, BR, BO): ripe samples from source A, overripe samples from source A, ripe samples from source B and overripe samples from source B. These tomato samples were homogenized and serial dilutions from dilution 10‑2 to 10‑4 were prepared. Spread plates on nutrient agar (NA), MacConkey (MAC) agar and eosin methylene blue (EMB) agar were conducted and incubated at 37°C for 24 h. Colony counts and morphologies were recorded and the obtained colonies were subjected to bacterial staining. Biochemical test were conducted and the isolates were identified. A positive correlation between the average pH and the average cfu mL-1 was observed. Sample type BO had the highest average cfu mL-1 followed by sample type AO, AR and BR. Nine bacterial genera were identified and all of them are known to be pathogenic to humans. The most prevalent genus was Enterobacter spp. followed by Klebsiella spp., Escherichia spp. and Bacillus spp. The average cfu mL-1 for the aerobic, coliform and faecal coliform counts exceeded the acceptable limit. Therefore, the consumption of these tomatoes could present health effects upon human ingestion suggesting a need for control measures.
Mbili, N.C. and Shude, S.P.N. (2020). Isolation and identification of bacterial microorganisms with public health implications in tomatoes sold in Pietermaritzburg, KwaZulu-Natal. Acta Hortic. 1292, 313-320
DOI: 10.17660/ActaHortic.2020.1292.41
https://doi.org/10.17660/ActaHortic.2020.1292.41
foodborne pathogens, tomatoes, coliforms, food safety
English

Acta Horticulturae