Bacillus Infection Among Children with Hematologic Malignancy, a Single Institution Experience

BACKGROUND: Bacillus species, including B. cereus and other non-anthracis species, are spore-forming, gram-positive rods, found ubiquitously in the environment and cause bacteremia and CNS infection in children with cancer. Case reports have demonstrated that Bacillus spp. infections carry a high morbidity, with rates of CNS involvement of 30%, and mortality as high as 40%. These studies indicate the preponderance of cases occur in children receiving induction chemotherapy for acute lymphoblastic leukemia (ALL). There have been no large, recent studies describing Bacillus spp. infection in children with an underlying oncologic condition.

METHODS: We performed a retrospective medical record review of pediatric cancer patients who received care at the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center and developed Bacillus spp. infection between January 1^st, 2005 and December 31^st 2014.  Given that the majority of these infections were found to occur in children with underlying hematologic malignancy, we provide a more detailed description of cases with these underlying conditions.

RESULTS: Twenty-six children developed Bacillus bacteremia during the study period.  Of the 26 patients, 21 (81%) had acute leukemia (18 ALL; 3 AML), 3 had neuroblastoma, one had Ewing’s sarcoma and one had an optic pathway glioma. The mean age of patients with hematologic malignancies at time of Bacillus spp. infection was 7.3 years [range: 1-17]. Sixteen (76%) children were neutropenic at the time of infection.  Of the children with ALL, 11 (61%) developed infection during the remission induction phase of treatment, 3 during post-induction/pre-maintenance treatment phases and 3 after relapse (1 during stem cell transplant, 1 at a year post-transplant and 1 during re-induction). Of the 26 patients, 5 (19%) developed CNS complications, all during remission induction for ALL, and the overall mortality two-weeks following Bacillus infection was 19%.

DISCUSSION: Bacillus spp. continues to cause serious infections in children with cancer, especially in those with underlying hematologic malignancies. While the mortality at our center is lower than that reported in the literature, the rate of death is still higher than what is typically seen with other organisms and CNS involvement remains common.  Further study in this area will include identification of risk factors for development of this infection and recommendations regarding use of prophylactic antibiotics.