BACILLUS-CEREUS AND RELATED SPECIES

Bacillus cereus is a gram-positive aerobic of faculatively anaerobic s pore-forming rod. It is a cause of food poisoning, which is frequently associated with the consumption of rice-based dishes. The organism pr oduces an emetic or diarrheal syndrome induced by an emetic toxin and enterotoxin, respectively. Other toxins are produced during growth, in cluding phospholipases, proteases, and hemolysins, one of which, cereo lysin, is a thiol-activated hemolysin. These toxins may contribute to the pathogenicity of B. cereus in nongastrointestinal disease. B. cere us isolated from clinical material other than feces or vomitus was com monly dismissed as a contaminant, but increasingly it is being recogni zed as a species with pathogenic potential. It is now recognized as an infrequent cause of serious nongsterointestinal infection, particular ly in drug addicts, the immunosupprressed, neonates, and postsurgical patients, especially when prosthetic implants such as ventricular shun ts are inserted. Ocular infections are the commonest types of severe i nfection, including endophthalmitis, panophthalmitis, and keratitis, u sually with the characteristic formation of corneal ring abscesses. Ev en with prompt surgical and antimicrobial agent treatment, enucleation of the eye and blindness are common sequelae. Septicemia, meningitis, endocarditis, osteomyelitis, and surgical and traumatic wound infecti ons are other manifestations of severe disease. B. cereus produces bet a-lactamases, unlike Bacillus anthracis, and so is resistant to beta-l actam antibiotics; it is usually susceptible to treatment with clindam ycin, vancomycin, gentamicin, chloramphenicol, and erythromicin. Simul taneous therapy via multiple routes may be required.