Serious infections caused by Bacillus species

Thirty-eight patients with serious infections caused by organisms belonging to the genus Bacillus are described. Our experience, and that reported in the literature, indicates that, in most cases, isolated Bacillus bacteremia is not a particularly serious disease. Therefore, under most circumstances, empiric antibiotic therapy designed specifically for treatment of Bacillus is probably not necessary. Endocarditis can occur, but apparently follows bacteremia only infrequently. When these bacteria cause localized infection such as pneumonia, pan-ophthalmitis, visceral abscess, or musculoskeletal infections, tissue necrosis and profound morbidity are the rule. The frequency of these complications following bacteremia appears to be low but cannot be estimated from our experience or that reported in the literature reviewed. The role of intravascular devices and trauma as predisposing factors is emphasized. Immunocompromised hosts and intravenous drug abusers appear predisposed, but intravascular devices in the former group may play an important role in the pathogenesis of Bacillus infections. Antibiotics which appear especially useful in the treatment of Bacillus infections are clindamycin and vancomycin, to which the vast majority of strains are susceptible in vitro. Beta-lactam antibiotics, including the new cephalosporins and penicillins, are of little value in this setting.