The aim of this study was to assess the germination and growth of two strains of Bacillus cereus following the artificial inoculation of six selected hot dishes with spores which were then stored at temperatures of 40, 50, and 60 °C for 0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 h. The water activity of the prepared meals varied between 0.967 and 0.973 and the salt content between 0.74 and 1.40%. The pH value of four dishes exceeded 6.0, but for two (tomato sauce and ratatouille) it was 4.6. The tested strain DSM 4312 showed good growth abilities and attained a population exceeding 6.0 log CFU/g within 4 h at 40 °C in foods with pH values > 6.0. The study demonstrated that a drop in food temperatures to 40 °C is risky, while no growth of B. cereus was detected within 4 h at 50 and 60 °C. The growth rate of B. cereus is conditioned not merely by environmental conditions (temperature, pH values, food composition), but also by the bacterial strain.

• Keywords
• Bacillus cereus spores, artificial contamination, hot dishes, pH value,
• Publication type
• Journal Article MeSH

In the food industry, the increasing antimicrobial resistance of food-borne pathogens to conventional sanitizers poses the risk of food contamination and a decrease in product quality and safety. Therefore, we explored alternative antimicrobials N-Acetyl-l-cysteine (NAC), rhamnolipids (RLs), and usnic acid (UA) as a novel approach to prevent biofilm formation and reduce existing biofilms formed by important food-borne pathogens (three strains of Salmonella enterica and two strains of Escherichia coli, Listeria monocytogenes, Staphylococcus aureus). Their effectiveness was evaluated by determining minimum inhibitory concentrations needed for inhibition of bacterial growth, biofilm formation, metabolic activity, and biofilm reduction. Transmission electron microscopy and confocal scanning laser microscopy followed by image analysis were used to visualize and quantify the impact of tested substances on both planktonic and biofilm-associated cells. The in vitro cytotoxicity of the substances was determined as a half-maximal inhibitory concentration in five different cell lines. The results indicate relatively low cytotoxic effects of NAC in comparison to RLs and UA. In addition, NAC inhibited bacterial growth for all strains, while RLs showed overall lower inhibition and UA inhibited only the growth of Gram-positive bacteria. Even though tested substances did not remove the biofilms, NAC represents a promising tool in biofilm prevention.

• Keywords
• N-Acetyl-l-cysteine, acute cytotoxicity, antimicrobial efficacy, bacterial growth, biofilm, food-borne pathogens, minimum inhibitory concentrations, rhamnolipids, usnic acid,
• MeSH
• Acetylcysteine pharmacology   MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Anti-Infective Agents pharmacology   MeSH
• Benzofurans pharmacology   MeSH
• Biofilms drug effects   MeSH
• Cell Line MeSH
• Escherichia coli drug effects   MeSH
• Glycolipids pharmacology   MeSH
• Food Contamination prevention & control   MeSH
• Humans MeSH
• Listeria monocytogenes drug effects   MeSH
• Microbial Sensitivity Tests MeSH
• Foodborne Diseases drug therapy   microbiology   MeSH
• Food Microbiology methods   MeSH
• Salmonella enterica drug effects   MeSH
• Staphylococcus aureus drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcysteine MeSH
• Anti-Bacterial Agents MeSH
• Anti-Infective Agents MeSH
• Benzofurans MeSH
• Glycolipids MeSH
• rhamnolipid MeSH Browser
• usnic acid MeSH Browser