Toxigenic and Antibiotic-Resistant Bacillus cereus in Raw Cow Milk from Eastern Cape, South Africa: A Potential Public Health Threat

Abstract

Bacillus cereus sensu lato is widespread and causes significant food spoilage that alters the flavour and structure of milk. The present study investigated the prevalence, enterotoxigenic genes, and resistant profiles of B. cereus strains isolated from raw milk of Bos taurus in South Africa (the Eastern Cape Province). One thousand four hundred samples were obtained from commercial dairy farms and were evaluated for the presence of B. cereus using B. cereus selective agar, and genomic DNA was isolated from B. cereus colonies with specific characteristics. PCR was used to evaluate the presence of enterotoxigenic genes, and antibacterial susceptibility was carried out using the Kirby-Bauer Disc diffusion method. The result revealed that B. cereus was detected in 250 raw milk samples. In addition, 67.2% of the isolates grew when incubated at 4 °C. Among the enterotoxigenic genes studied, ces showed the highest occurrence (88.8%), but hblABC (0%) did not demonstrate amplification from any isolate. Our analysis found two significant patterns (III and V): nheABC-entFM (27.2% and 24.4%) and the ces gene. Total (100%) sensitivity was observed for six of the twelve antibiotics tested, while organisms showed complete resistance to penicillin and rifampicin. This study marks the initial documentation of B. cereus and its enterotoxigenic genes in Bos taurus raw milk sourced from the Eastern Cape Province, South Africa. Enterotoxin FM should be considered the second most crucial enterotoxin, after non-hemolytic enterotoxin, and should be included in the molecular approach used to classify pathogenic B. cereus in nutrimental products. These findings underscore the urgent need for public health awareness, particularly in rural communities where raw milk consumption is prevalent. The high prevalence of antibiotic resistance and toxigenic strains of B. cereus calls for improved milk pasteurization practices to mitigate the risk of foodborne illness.