Microbiological Quality and Safety of Ready-to-Eat Street-Vended Foods in Johannesburg, South Africa

Abstract

Fifty-one ready-to-eat street foods, 18 dishwater, and 18 surface swab samples were collected from six vendors in Johannesburg, South Africa. Food temperatures were recorded at the time of sampling. Standard methods were used to determine aerobic plate counts (APCs), spore counts (SCs), and Enterobacteriaceae counts (ECs) for food samples as well as coliform counts (CCs) for water and swab samples. In addition, Petrifilm Escherichia coli count (PC) plates were used for the enumeration of coliforms in food, water, and swab samples. The presence of selected foodborne pathogens in the food samples as well as the presence of nonpathogenic E. coli 1 (in food and water samples) was also tested for. Predominant colonies isolated from APC plates were characterized to the genus level. Holding temperatures for cooked meats and gravies ranged from 42.0 to 94.0°C, and those for uncooked salads ranged from 29.0 to 39.0°C. Mean APC values of 3.4 (±0.4) log CFU/g, 4.0 (±1.2) log CFU/ml, and 2.1 (±0.4) log CFU/25 cm2 were obtained for food, water, and swab samples, respectively. Mean SC values of 1.6 (±0.2) log CFU/g and 1.5 (±0.3) log CFU/25 cm2 were obtained for food and swab samples, respectively. A mean EC value of 2.0 (±0.4) log CFU/g for food samples and mean CC values of 2.5 (±0.3) log CFU/ml and 1.3 (±0.3) log CFU/25 cm2 for water and swab samples, respectively, were determined. Mean PC values of 1.6 (±0.1) log CFU/g, 1.9 (±0.6) log CFU/ml, and 1.4 (±0.4) log CFU/25 cm2 were determined for food, water, and swab samples, respectively. Bacillus cereus was detected in 22%, Clostridium perfringens in 16%, Salmonella spp. in 2%, and E. coli (non-O157:H+) in 2% of the 51 food samples. E. coli was found in 14 water samples (78%) and in 3 food samples (6%). Campylobacter spp., Listeria monocytogenes, Staphylococcus aureus, Vibrio cholerae, and Yersinia enterocolitica were also tested for in the food samples, but they were not detected. The 340 isolates obtained from APC plates for food, water, and swab samples were predominantly Bacillus spp., Micrococcus spp., and Staphylococcus spp. for all three sample types. It was concluded that the foods analyzed in this study were of acceptable quality and safety.