Enterotoxigenic Profiles of psychrotolerant and mesophilic strains of the Bacillus cereus group isolated from food in Morocco

The species Bacillus cereus, known for its ability to cause food borne disease, consists of a large variety of strains. An important property for discrimination of strains is their growth temperature range. Fifty-two strains of Bacillus cereus isolated from different sources of food (milk, dairy product, spices and rice salad) for two years were determined to be either mesophilic or psychrotrophic by growth at 6 °C and at 43° C on optimal agar medium. The strains were also screened by real time polymerase chain reaction to discriminate between mesophilic and psychrotrophic types. The result obtained allowed highlighting eight profiles. Thirty seven of the 52 strains were able to grow at 6°C, but only thirteen conformed to the new psychrotolerant species Bacillus weihenstephanensis. The presence of the gene components encoding production of enterotoxins Nhe, Hbl, EntT and a recently described cytotoxin K was determined by PCR. All the strains possessed genes for at least one of these toxins. The nhe genes were detected in a higher proportion than hbl genes. Haemolytic enterotoxin was detected in 71.1 per cent of the isolates. Results of this study indicate that there are intermediate forms between B. cereus and B. weihenstephanensis, these results might be of importance for gaining further understanding of the growth properties of B. weihenstephanensis and psychrotolerant B. cereus as well as their contribution to food poisoning. However, no relationship among haemolysis test, enterotoxin genes and growth temperatures of the strains