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Pol. J. Food Nutr. Sci. 2009;59(1):53–59
The subject of analysis were three main types of cereals available at retail on the local market. The objective was to assess the extent of the cereals contamination by B. cereus group and to indicate the species dominant in cereals contamination. Bacteria of B. cereus group were present in 89.6% of the retail packs tested. The isolation frequency of B. cereus from pearl barley, buckwheat and wheat cereals was 85%, 85.7% and 100%, respectively, with contamination level, in majority of the analysed samples (60.4%), exceeding 102 MPN/g. The strains prevailing in cereals contamination did not hydrolyse starch and were β hemolytic. Out of the 380 isolated strains, those not hydrolysing starch accounted for 56%, with only 16 strains (4.2%) not able both to hydrolyse starch and non-hemolytic. Amongst the strains growing at 4˚ to 30˚C the ability to hydrolyse starch and to perform β hemolysis – the features attributed to diarrheal strains – was expressed by 36.9% strains. Twenty strains (5.3% of the total number) – non-hemolytic, unable to hydrolyse starch and not growing at 4˚C – were considered as potentially emetic ones. Mesophilic, lecithinase-positive strains, β hemolysis-positive, unable to hydrolyse starch predominant in the tested cereals (208/380) were identified with the API 50 CHB tests (Bio Merieux) as B. cereus type 1. B. cereus type 1 was the prevailing contaminant in barley and wheat cereals. In buckwheat, the most commonly isolated species was B. mycoides.