INCIDENCE OF BACILLUS-CEREUS AND BACILLUS-SUBTILIS IN FOODS IN THE NETHERLANDS

The incidence of B. cereus and B. subtilis in various food products in the Netherlands was investigated. In total, 229 samples (milk, yeast, flour, pasta products, Chinese meals, cocoa, chocolate, bakery produc ts, meat products, herbs and spices) were analysed. Of these 109 (48%) contained B. cereus. The contamination level ranged from 10(2)-10(6) bacteria g(-1) or m(-1) B. subtilis was present in 18 of 72 (25%) samp les examined, the levels varied from 10(2)-10(5) bacteria g(-1). From 12 of these 72 (17%) samples, both B. cereus and B. subtilis could be isolated. In total, 91 presumptive B. cereus colonies were isolated fr om the various samples. According to the ISO conformation tests and th e carbohydrate patterns (API 50 CHB) 81 (89%) of these isolates were c onfirmed to be B. cereus. Of the 50 suspect B. subtilis colonies, 10 i solates were shown to be B. pumilis based on inability to ferment sorb itol and carbohydrate utilization pattern in the API 50 CHB. Of the re maining 40 isolates 30 (75%) were determined to be B. subtilis accordi ng to the confirmation tests and the carbohydrate patterns, four (10%) were B. licheniformis and six (15%) were shown to be B. amyloliquefac iens. These Bacillus species, belonging to the 'B. subtilis group', ar e also suspected as food-poisoning agents. Numbers of B. subtilis appe ared to decrease more readily by processing and storage of food produc ts than those of B. cereus. This phenomenon, and the fact that direct isolation methods for B. subtilis are not available, indicate that the role of B. subtilis in food spoilage and foodborne infections and int oxication may be underestimated. (C) 1996 Academic Press Limited.