Molecular detection and toxigenic profiling of Bacillus cereus in milk-based sweets of Bikaner, Rajasthan: A public health perspective

Abstract

Milk-based sweets are extensively consumed across India and are often produced under artisanal or small-scale conditions where adherence to strict hygienic practices may be limited, thereby posing risks to microbiological safety. Bacillus cereus, a spore-forming foodborne pathogen, is of particular public health relevance owing to its ability to withstand heat treatment and its capacity to produce a range of enterotoxins responsible for gastrointestinal disorders. In this study, the prevalence and toxigenic potential of B. cereus in milk-based sweets marketed in Bikaner, Rajasthan, were assessed using conventional culture techniques in combination with polymerase chain reaction (PCR). A total of 300 milk-based sweet samples were analysed, comprising 150 mawa-based and 150 chhana-based products. Presumptive B. cereus isolates were molecularly confirmed by PCR amplification of the gyrB gene, followed by screening for virulence-associated genes (nheA, hblA, cytK, and cesB). Overall, B. cereus was detected in 13% of the samples, with a higher prevalence in mawa-based sweets (16.66%; 25 isolates) than in chhana-based sweets (9.33%; 14 isolates). Among isolates from mawa-based sweets, the occurrence of virulence genes was 36% for nheA, 40% for hblA, 16% for cesB, and 48% for cytK. In contrast, isolates recovered from chhana-based sweets showed lower prevalence rates, with 14.28% each for nheA, hblA, and cytK, while cesB was not detected. Notably, several isolates carried more than one toxin gene, suggesting enhanced pathogenic potential. The presence of toxigenic B. cereus in widely consumed traditional milk sweets represents a considerable food safety risk. These findings emphasize the need for regular molecular monitoring and the implementation of improved hygiene and handling practices during the preparation and marketing of traditional dairy products.