Bacillus spp. among hospitalized patients with haematological malignancies: clinical features, epidemics and outcomes.

Between April 2000 and May 2005, 350 bacteraemic episodes occurred among patients treated in our haematology unit. Two hundred and twenty-eight of these episodes were caused by Gram-positive pathogens, most commonly coagulase-negative staphylococci and Staphylococcus aureus. One hundred and twenty-two episodes were due to Gram-negative pathogens, with a predominance of Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa. Bacillus bacteraemias constituted 12 of these episodes occurring in 12 patients, and accounted for 3.4% of all bacteraemic episodes. Of the 12 strains evaluated, seven were Bacillus licheniformis, three were Bacillus cereus and two were Bacillus pumilus. Seven episodes presented with bloodstream infection, three with pneumonia, one with severe abdominal pain and deterioration of liver function, and one with a catheter-related bloodstream infection. B. licheniformis was isolated from five patients who had been hospitalized at the same time. This outbreak was related to non-sterile cotton wool used during skin disinfection. B. cereus and B. licheniformis isolates were susceptible to cefepime, carbapenems, aminoglycosides and vancomycin, but B. pumilus isolates were resistant to all antibiotics except for quinolones and vancomycin. Two deaths were observed. In conclusion, Bacillus spp. may cause serious infections, diagnostic and therapeutic dilemmas, and high morbidity and mortality in patients with haematological malignancies. Both B. cereus and B. licheniformis may be among the 'new' Gram-positive pathogens to cause serious infection in patients with neutropenia.