Detection of Staphylococcus aureus Enterotoxins in Raw and Processed Milk in Khartoum State, Sudan

Staphylococcus aureus is a leading cause of foodborne illness due to its production of heat-stable enterotoxins. This study investigated the presence of enterotoxigenic S. aureus in raw, pasteurized, and ultra-high temperature (UHT) processed milk at Khartoum State, Sudan in October 2019. A total of 56 milk samples were collected randomly by purchasing the raw milk from some public markets, meanwhile, different manufacturing batches of pasteurized and UHT milk samples were obtained from the outlets of dairy factories and supermarkets. After isolation and identification of S. aureus, a multiplex PCR assay was used to simultaneously detect sea, seb, sec and sed enterotoxins genes. The S. aureus was found in 48.2% of the milk samples investigated, with isolation rates of 29.6, 14.8 and 55.6% in raw, pasteurized and UHT milk, respectively. The targeted enterotoxin genes revealed positive detection only in the UHT milk as 15 samples were found to harbored enterotoxigenic S. aureus: 8 (14.3%) sea, 5 (8.9%) sec and 2 (3.6%) seb. These findings demonstrate that even commercially processed fluid milks can be contaminated with enterotoxigenic S. aureus and that the direct detection of the classical enterotoxins from fluid milk was possible. The present study discusses and underscore the public health risks of staphylococcal enterotoxins in dairy products and highlight the urgent need for improved hygiene and monitoring for milk safety by the starting routine screening and examination programs for milk and dairy products before offering them for sale. This will help in safeguard the public health from the risks of S. aureus enterotoxins and other pathogens associated with food poisoning in the country.