Toxigenic Staphylococcus aureus contamination in ready-to-eat (RTE) food is a leading cause of foodborne illness in Korea. To monitor food contamination by S. aureus, a total of 3,332 RTE food samp...

Bacillus cereus has long been recognized as an important pathogen in foodborne poisoning worldwide. Fresh vegetables are often contaminated with enterotoxigenic B. cereus and have been implicated as a vehicle for the transmission of this bacterium. This study reports on the occurrence, virulence gene profile, and antibiotic resistance of B. cereus in fresh vegetables. Of 102 examined samples, 48 (47%) of the samples were contaminated with B. cereus (>1 log CFU/g) and 7 (6.8%) of the samples showed more than 3 log CFU/g. In total, 118 B. cereus isolates were examined for the virulence genes nheA, nheB, nheC, hblA, hblC, hblD, cytK, and entFM and for resistance to antibiotics. Of these B. cereus isolates, 70% harbored nheA, nheB, nheC, and cytK. Eighteen (80%) of 21 isolates from bell peppers possessed eight enterotoxin genes. B. cereus isolates were susceptible to imipenem, vancomycin, gentamicin, erythromycin, ciprofloxacin, and chloramphenicol, whereas 22.4% of isolates from garlic chives, 48.7%...

Chemical antibacterials are widely used to control microbial growth but have raised concerns about health risks. It is necessary to find alternative, non-toxic antibacterial agents for the inhibition of pathogens in foods or food contact surfaces. To develop a non-toxic and “green” food-grade alternative to chemical sanitizers, we formulated a multicomponent antibacterial mixture containing Rosmarinus officinalis L., Camellia sinensis L., citric acid, and ε-polylysine and evaluated its bactericidal efficacy against Staphylococcus aureus, Escherichia coli, Bacillus cereus, Salmonella Enteritidis, and Listeria monocytogenes on food contact surfaces. A combination of the agents allowed their use at levels lower than were effective when tested individually. At a concentration of 0.25%, the multicomponent mixture reduced viable cell count by more than 5 log CFU/area, with complete inactivation 24 h after treatment. The inhibitory efficacy of the chemical antibacterial agent (sodium hypochlorite, 200 ppm) and the multicomponent antibacterial mixture (0.25%) on utensil surfaces against S. aureus, E. coli, S. Enteritidis, and L. monocytogenes were similar, but the multicomponent system was more effective against B. cereus than sodium hypochlorite, with an immediate 99.999% reduction on knife and plastic basket surfaces, respectively, and within 2 h on cutting board surfaces after treatment. A combination of these food-grade antibacterials could be a useful strategy for inhibition of bacteria on food contact surfaces while allowing use of lower concentrations of its components than are effective individually. This multicomponent food-grade antibacterial mixture may be a suitable “green” alternative to chemical sanitizers.

The prevalence and characteristics of low-temperature-tolerant Bacillus cereus (psychrotolerant B. cereus) in green leaf lettuce collected during cold chain were investigated. Among the 101 isolated B. cereus samples, only 18 were capable of growth at 7 °C, and these isolates shared potential health hazard characteristics with mesophilic isolates. Most psychrotolerant B. cereus isolates contained various combinations of nheA, nheB, nheC, hblA, hblA, hblC, hblD, cytK, and entFM. Most isolates of psychrotolerant B. cereus possessed at least two enterotoxin genes and 28% of isolates harbored tested nine enterotoxin genes. Additionally, the psychrotolerant B. cereus isolates showed resistance to tetracycline and rifampin and intermediate levels of resistance to clindamycin. A total of 23% of isolates among psychrotolerant B. cereus displayed a high level of biofilm formation at 7 °C than at 10 °C or 30 °C. The results of this study indicate that cold distribution and storage for green leaf lettuce may fail to maintain food safety due to the presence of enterotoxigenic, antibiotic-resistant, and strong biofilm forming psychrotolerant B. cereus isolates, which therefore poses a potential health risk to the consumer. Our findings provide the first account of the prevalence and characteristics of psychrotolerant B. cereus isolated from green leaf lettuce during cold storage, suggesting a potential hazard of psychrotolerant B. cereus isolates to public health and the food industry.

Agricultural water is closely linked to surface and ground water as well as soil; hence, ensuring its safety is an important endeavor. We used the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) method to analyze multi-residue pesticides in agricultural water by using a combined-sorbent-based clean-up procedure. Among the various sorbents examined, clean-up using ENVI-Carb combined with a primary secondary amine sorbent delivered the highest recovery of multi-residue pesticides (>93.9%). While the developed method showed satisfactory linearity (R² > 0.9991), precision, and specificity, recovery was low for pyrazolate (29.1%) and thidiazuron (59.2%). The limits of detection and quantification for the 55 pesticides targeted in this study were in 0.02–3.0 μg L⁻¹ and 0.1–9.9 μg L⁻¹, respectively. The developed method was used to identify and quantify multi-residue pesticides during sample analysis. The results suggest that the QuEChERS method employing a combination of ENVI-Carb and another sorbent can be applied for the effective analysis of multi-residue pesticides in agricultural water.

This study determined the prevalence and toxin profile of Bacillus cereus and Bacillus thuringiensis in doenjang, a fermented soybean food, made using both traditional and commercial methods. The 51 doenjang samples tested were broadly contaminated with B. cereus; in contrast, only one sample was positive for B. thuringiensis. All B. cereus isolates from doenjang were positive for diarrheal toxin genes. The frequencies of nheABC and hblACD in traditional samples were 22.7 and 0%, respectively, whereas 5.1 and 5.1% of B. cereus isolates from commercial samples possessed nheABC and hblACD, respectively. The detection rate of ces gene was 10.8%. The predominant toxin profile among isolates from enterotoxigenic B. cereus in doenjang was profile 4 (entFM-bceT-cytK). The major enterotoxin genes in emetic B. cereus were cytK, entFM, and nheA genes. The B. thuringiensis isolate was of the diarrheagenic type. These results provide a better understanding of the epidemiology of the enterotoxigenic and emetic B. cereus groups in Korean fermented soybean products.