Bacillus cereus is often considered a contaminant when it is isolated from blood culture; however, it can also cause bloodstream infections (BSI) in patients with significant underlying conditions. The 30-day mortality rates among patients with a B. cereus BSI ranged from 3.4% to 9.5% in previous studies. The aim of this study was to describe the clinical characteristics of B. cereus BSI in a tertiary care hospital in Japan.
We performed a hospital-based retrospective case analysis. All episodes in which B. cereus was isolated from blood cultures from January 2006 to December 2015 were identified using our laboratory database at the Kameda Medical Center. This is a tertiary care hospital with 925 beds. BSI was defined as follows: (1) more than two sets of positive blood cultures; (2) more than one set of positive blood culture with a positive catheter tip culture; or (3) more than one set of positive blood culture with persistent positive blood cultures. Demographics and clinical information (e.g., age, gender, underlying disease, presence of central venous catheter, use of parenteral nutrition, and 30-day mortality) were reviewed for BSI episodes.
In total, B. cereus was isolated from the blood cultures of 163 episodes and 66 were identified as BSI (median age 74 years, 50% men). The true BSI rate was 40.5%. The most frequent comorbidity was a solid tumor (32.3%) followed by cerebrovascular disease (27.7%) and hematologic malignancy (26.2%). Parenteral nutrition was given in 39 episodes (59.1%). Catheter-related bloodstream infection (80% peripheral catheter-related and 20% central venous catheter-related BSI) was the most frequent source (53.8%) of infection. The 30-day mortality rate was 18.2%.
In the present study, both the true BSI rate and 30-day mortality were much higher than previously reported. Careful attention should be paid for true BSI when B. cereus is isolated from blood cultures.
Y. Otsuka, None
N. Hosokawa, None