ABSTRACT
I. BACKGROUND Bacillus cereus has a ubiquitous distribution in nature, and this aerobic endospore-forming rod is normally present in soil, dust, and water. Because of its wide and generalized presence in the environment, it can be isolated from a variety of processed and raw foods-particularly in vegetation, which comes directly in contact with the soil. Its presence in foods, however, is not a significant health hazard unless the organism is able to grow (1) and produce toxins giving rise to foodborne illness. However, the isolation of high levels of B. cereus is suggestive of the organism's involvement in food poisoning (2). The consumption of food containing more than 105 viable toxigenic B. cereus organisms per gram of food has resulted in outbreaks of food poisoning (3-5). Although B. cereus was long considered a harmless saprophyte, its role as a potential foodborne pathogen associated with food poisoning was recognized in Europe as early as 1906 (6). Its role as a significant foodpoisoning organism has been recognized since the 1950s (4,7). The first clearly documented outbreak occurred in Great Britain in 1971 (8). All populations appear to be susceptible to food poisoning caused by this organism. Although B. cereus is the most common organism associated with food poisoning, other Bacillus species such as B. licheniformis, B. subtilis, B. pumilus, and B. brevis have also been linked to food-poisoning outbreaks and have been documented elsewhere (5,9,10). Other enterotoxin-producing bacilli, including psychrotrophic B. circulans, B. lentus, B. thuringiensis, B. polymyxa, B. carotarum, and B. pasteurii, have been isolated from foods (11). Moreover, in recent years, B. cereus and other species proven to be sometimes psychrotrophic and isolated from foods stored at refrigeration temperatures have been, in fact, enterotoxigenic and are of increasing concern to the food industries (12-14).
