Physical characteristics of spores of food-associated isolates of the Bacillus cereus group.

All 47 food-borne isolates of Bacillus cereus sensu stricto, as well as 10 of 12 food-borne, enterotoxigenic isolates of Bacillus thuringiensis, possessed appendages. Spores were moderately to highly hydrophobic, and each had a net negative charge. These characteristics indicate that spores of food-associated B.

Survival during cooking and growth from spores of diarrheal and emetic types of Bacillus cereus in rice.

Bacillus cereus is a gram-positive, spore-forming, facultative anaerobe that is responsible for two types of gastrointestinal diseases: emesis and diarrhea. A significant difference in the D(95 degrees C)-values of spores of the emetic and the diarrheal types was initially determined. A mixture of B.

Detection of toxigenic Bacillus cereus and Bacillus thuringiensis spores in U.S. rice.

Bacillus cereus is a gram-positive, endospore forming pathogenic bacterium that is ubiquitous in the environment and is frequently associated with emetic and diarrheal types of foodborne illness. In this study, 178 samples of raw rice from retail food stores were analyzed for the presence of B. cereus spores.

Elevation of the Heat Resistance of Vegetative Cells and Spores of Clostridium perfringens Type A by Sublethal Heat Shock.

The degree of heat resistance conferred on Clostridium perfringens by a heat shock, the kinetics of this development, and its duration were determined. A sublethal heat shock at 55°C for 30 min increased the heat tolerance of vegetative cells at least two- to threefold. The acquired tolerance was maintained for 2 h after the heat shock treatment.

Lack of Correlation between the Enterotoxigenicity of Clostridium perfringens Isolates and Propionic Acid Formation or Amylase Activity at 46°C.

The absence in the supernatant fluid of either extracellular amylase in cultures grown at 46°C or propionic acid has been proposed for the presumptive identification of enterotoxin-positive strains of Clostridium perfringens . However we found that propionic acid was formed by several enterotoxin-positive, as well as enterotoxin-negative, strains of this organism. In addition 4 of 13 ent stains produced extracellular amylase during growth at 46°C.

Enumeration and Confirmation of Clostridium perfringens.

A number of media have been proposed for the enumeration and confirmation of Clostridium perfringens in food and water. Most of these employ sulfite and iron together with selective antibiotics. This report discusses these various media and conditions for their use.

Evaluation of Plating Media for Recovery of Heated Clostridium perfringens Spores.

Four selective and eight non-selective plating media were evaluated for their ability to enumerate six strains of heat-activated and heat-injured spores of Clostridium perfringens . Trypticase-sulfite-neomycin (TSN) agar and sulfite-polymyxin-sulfadiazine (SPS) agar gave higher counts of heat-activated spores than non-selective media. In the case of heat-injured spores, wide variation in recovery was obtained depending on strain and medium.