Prevalence of Bacillus cereus in milk and some milk products in Egypt

Abstract

Keywords Bacillus cereus is a spore-forming bacterium that causes food spoilage and poisoning. This study aimed to evaluate the prevalence of enterotoxigenic Bacillus cereus in 180 dairy samples across three cites (Tanta, El-Santa, and El-Mahalla El-Kubra) in El-Gharbia Governorate, Egypt, including raw milk, milk powder and Ras cheese ( 60 of each). Samples were collected from December 2022 to April 2023 and analyzed using traditional isolation, biochemical identification with VITEK 2, and PCR targeting the nhe A gene as a virulence factor for Bacillus cereus . Traditional isolation on selective media indicated a prevalence of 1.66%, 24.99% and 4.99% in raw milk, milk powder and Ras cheese, respectively. However, VITEK 2 only confirmed that Bacillus cereus in milk powder isolates was 24.99%. PCR detection of the nhe A gene revealed that Bacillus cereus in the examined samples completely matched with traditional isolation. Overall, 10.5% of samples were positive for enterotoxigenic Bacillus cereus by PCR. Compared to PCR, traditional isolation showed 100% sensitivity and specificity, while VITEK 2 had 79% sensitivity and 100% specificity. Although biochemical methods like VITEK 2 enabled rapid automated identification, PCR detection of virulence genes provided superior sensitivity for identifying enterotoxigenic Bacillus cereus of clinical significance from dairy samples. Traditional culture techniques remain essential for isolating target bacteria prior to PCR. This study provided insights into the prevalence of enterotoxigenic Bacillus cereus contamination in some Egyptian dairy products.