Prevalence, virulence genes, and genetic diversity of Bacillus cereus isolated from convenience food

Abstract

Background. In times when there is a growing interest in ready-to-eat food (RTEF), the presence of potentially pathogenic bacteria, including the toxigenic psychrotolerant bacilli from the B. cereus group, on this type of carrier may pose a real threat to the health of consumers. A significant part of RTEF is represented by vegetable products and food products made with them. The increased production of convenience foods has resulted in their international turnover growing. When coupled with a rising percentage of persons from risk groups (YOPI), including the elderly or immunocompromised, this may mean increased health risks posed by the so-called "novel pathogens", like the toxigenic psychrotolerant B. cereus sensu lato. Materials and methods. Food samples were analyzed for the presence and count of putative B. cereus according to the Polish Standard PN-EN ISO 7932:2005. All genetic analyses were conducted using a qualitative real-time PCR. Results. The presence of B. cereus sensu lato was confirmed in 130 out of the 192 samples of convenience foods, at contamination levels ranging from 1.65 to 3.32 log CFU/g. Among the strains confirmed to belong to the B. cereus group, 23 were identified as emetic B. cereus. The analysis of each strain's ability to grow at temp. 4-10°C demonstrated that 4.9% and 12.7% of the isolates were able to grow at 4°C and 6°C, respectively. In turn, 15.2% were able to grow at 8°C, and 36.3% at 10°C. None of the psychrotrophic strains possessed genes typical of B. weihenstephanensis. The group of psychrotrophic B. cereus included potentially toxigenic strains being carriers of genes that determine the synthesis of the following toxins: NHE, HBL, CytK, and cereulide. Some of them were potent enough to produce more than one toxin. Conclusions. The analyses conducted in this study demonstrate that the psychrotolerant strains of B. cereus (including the toxigenic ones) are frequent microbiological contaminants of RTEF products offered in retail. The presence of emetic strains from the B. cereus group, which are able to grow in a wide range of temperatures and produce enterotoxins and enzymes with the characteristics of toxins, in ready-to-eat foods may pose a real threat to consumer health.

Incorporation of Natural Colourants into Thai Steamed Cupcakes

“…To consider the risk hazard of each food pathogen, B. cereus spores can germinate and grow out rapidly after heat treatment and produce emetic and enteric toxins. Many strains of S. aureus produce staphylococcal enterotoxins, while certain strains of E. coli are used as a faecal contamination index of food sanitation (Angelidis et al, 2006;Dlubala et al, 2021;Olaimat et al, 2021).…”