Carlos Eduardo Gamero Aguilar

Bacillus cereus is a spore-forming, Gram-positive bacterium that causes foodborne illness and dairy spoilage. This study analyzed B. cereus s.s. isolates from milking environments, raw milk, and dairy products to assess their genotypic and phenotypic traits. From 466 samples, 61 isolates were obtained: 27 from milking environments, 9 from dairy environments, 8 from raw milk, and 17 from dairy products. Genomic sequencing identified genes encoding proteolytic (BC5350, BC0666, BC2984, BC0598, BC5351, BC3383, BC2735), lipolytic (BC4862, BC2141, BC1027, BC4123, BC4345, BC5402, BC5401), and esterase (BC1954, BC4515, BC3413, BC3606) enzymes. Plate assays confirmed enzymatic activities. Proteolytic genes were more prevalent in environmental samples, followed by raw milk and dairy products. Lipolytic genes were most frequent in raw milk, followed by environmental samples and dairy products. Esterase genes were most common in dairy environments. These findings suggest that dairy processing influences the enzymatic profile of B. cereus s.s., potentially impacting food safety and quality in the dairy industry. Understanding the distribution of these genes may help develop strategies to mitigate spoilage and contamination risks in dairy products.

With the objective to evaluate the hygienic and sanitary conditions of grated parmesan cheese acquired from the retail business, total 120 cheese samples were acquired: 60 of which were obtained from four different brands of cheese that were grated in factories, and the other 60 samples were obtained from another four brands of cheese that are normally acquired by retailers (supermarkets) in blocks and grated at the moment of sale. The population of heterotrophic mesophilic microorganisms ranged from 1.2×10³ to 1.1×10⁷ colony-forming units (CFU)·g^-1. All samples analyzed contained Staphylococcus spp. with populations varying from 1.2×10³ to 8.7×10⁶CFU·g^-1, from which 60.0% were classified as coagulase-positive Staphylococcus and 52.5% of the samples possessed populations above the permissible limit set by legislation. Staphylococcus aureus was detected in 57.5% of the samples. Population of molds and yeasts varied from 6CFU·g^-1. Salmonella spp. was not isolated in this research. A difference was observed between the parmesan cheese grated in factories and that grated in supermarkets, where the former presented better microbiological quality than the latter. Thus, procedures must be proposed to minimize the presence of pathogenic agents reported in grated parmesan cheeses evaluated in the present study because of the public health risk associated with food bacterial contamination.