Bacillus cereus bacteraemia: comparison between haematologic and nonhaematologic patients

Abstract

Bacillus cereus bacteraemia can be severe, especially among patients with haematologic malignancy. We retrospectively reviewed first episodes of true B. cereus bacteraemia (more than one positive bottle plus signs of infection) at our institution between 1997 and 2013 with the aim to compare haematologic versus nonhaematologic patients and analyse episodes with complicated outcome. Among 56 episodes of positive-blood cultures for B. cereus, 21 were considered significant. Median age was 54 years (range 23-82 years). Ten patients (48%) had a haematologic malignancy; all were neutropenic at the time of B. cereus bacteraemia. Nonhaematologic patients were either intravenous drug users (n = 3, 14%), polytraumatized (n = 3, 14%) or had multiple chronic comorbidities (n = 5, 24%). Most episodes were hospital acquired (15, 71%). Sources of bacteraemia were intravascular catheter (n = 11, 52%), digestive tract (n = 6, 29%), drug injection (n = 3, 14%) and wound (n = 1, 5%). Adequate antibiotic therapy was provided to 18 patients (86%) during a median of 17 days (range 2-253 days). The intravascular catheter was removed in eight cases (42%). Three haematologic patients had a complicated course with neurologic complications (meningoencephalitis and cerebral abscesses). Complications appeared to be associated with catheter infection (100% of complicated cases vs. 29% of noncomplicated cases). In conclusion, B. cereus bacteraemia can have a complicated course in a subset of patients, mainly those with haematologic malignancy. Catheter infection may be associated with a worse outcome with frequent neurologic complications.

Keywords: Bacillus cereus; bacteraemia; central nervous system; intravascular catheter; neutropenia.

Fig. 1

Timing of infection and underlying diseases. Haematologic disease (n = 10): acute myeloid leukemia (n = 5), myelodysplastic syndrome (n = 3), acute lymphatic leukemia (n = 2). Chronic disease (n = 4): end-stage renal disease (n = 2), autoimmune hepatitis (n = 1), diabetes mellitus (n = 1), pseudomyxoma peritonei (n = 1). Polytrauma (n = 3). Intravenous drug use (IVDU, n = 3).

Fig. 2

Antibiotic susceptibility of 21 Bacillus cereus strains. I, intermediate; R, resistant; S, susceptible.

Fig. 3

Brain imaging of haematogenous cerebral abscesses complicating Bacillus cereus bacteraemia in a 63-year-old man with relapsing acute myeloid leukemia. At day 13 after induction chemotherapy, the patient presented with neutropenic fever, headache, photopsia and left leg paresis. Magnetic resonance imaging (MRI) at first neurologic symptoms revealed a focal lesion in the paracentral lobule with focal oedema and contrast enhancement on T2- and T1-weighted images (arrows) (A). B. cereus was grown from blood cultures on the same day. Contrast-enhanced computed tomography performed to investigate neurologic deterioration (progression of paresis, lethargy and hemineglect) showed a significant increase in perilesional edema and appearance of new abscesses (arrowhead) (B). Antibiotic therapy (imipenem switched to oral levofloxacin at discharge), initially associated with high-dose corticoids, was carried on for a total of 8.5 months. Neurologic deficits regressed completely. Last follow-up MRI T2- and T1-weighted images showed an inactive lesion with minimal gliosis and no contrast enhancement (arrowhead) (C).