Ba813 harboring Bacillus cereus, genetically closely related to Bacillus anthracis, causing nosocomial bloodstream infection: Bacterial virulence factors and clinical outcome.

Tetsuji Aoyagi,Makiko Yoshida,Hajime Kanamori,Shiro Endo,Koichi Tokuda,Mitsuo Kaku,Hiroaki Baba,Kengo Oshima,Baochuan Lin

doi:10.1371/journal.pone.0235771

Tetsuji Aoyagi, Makiko Yoshida + Show 7 more

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https://doi.org/10.1371/journal.pone.0235771

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Abstract

Bacillus cereus commonly causes catheter-related bloodstream infections (BSIs) in hospital settings, and occasionally occurs fatal central nervous system (CNS) complications. B. cereus harboring Ba813, a specific chromosomal marker of Bacillus anthracis, has been found in patients with severe infection and nosocomial BSI. However, the bacteriological profile and clinical feature of Ba813 (+) B. cereus are unclear. Fifty-three patients with B. cereus BSI were examined. Isolates were evaluated for Ba813, B. anthracis-related and food poisoning-related virulence, multilocus sequencing typing, and biofilm formation. Patients’ clinical records were reviewed retrospectively. The 53 isolates were comprised of 29 different sequence types in two distinct clades. Seventeen of the 53 (32%) B. cereus isolates including five sequence types possessed Ba813 and were classified into Clade-1/Cereus-III lineage which is most closely related to Anthracis lineage. No B. cereus possessed B. anthracis-related virulence genes. Ba813 (+) strains showed a lower prevalence of enterotoxin genes than Clade-2 strains (n = 4), but no difference from Clade-1. Ba813 (+) strains showed significantly lower biofilm formation than Clade-1/non-Cereus-III (n = 22) and Clade-2 strains, respectively. Compared to Clade-1/non-Cereus-III and Clade-2 B. cereus, Ba813 (+) strains were isolated more frequently from elderly patients, patients with indwelling central venous catheter rather than peripheral venous catheter, and patients who remained in the hospital for longer before BSI onset. No significant differences in disease severity or mortality were observed. Though two of the ten Ba813 (-) strains in Clade-1/Cereus III were isolated from the patients with CNS complication, no significant difference was observed in the bacterial profile and clinical characteristics among Clade-1/Cereus III strains. In conclusion, our report suggested that Ba813-harboring B. cereus strains, genetically closely related to B. anthracis, were abundant among B. cereus strains in the hospital setting, and might cause catheter-related nosocomial BSI. However, it did not affect the clinical outcomes.

Highlights

Bacillus cereus, a gram-positive bacillus, is widely distributed in natural environments including water and soil
Forty-nine B. cereus isolates were classified into the Bacillus group Clade-1
Ba813 (+) B. cereus bacteremia is not associated with severity and high mortality in the hospital setting

Summary

Introduction

A gram-positive bacillus, is widely distributed in natural environments including water and soil. B. cereus is an important pathogen causing food poisoning and can cause fatal systemic infection, in immunocompromised patients [1]. B. cereus nosocomial blood stream infection (BSI) can have fatal outcomes complicated with central nerve systemic (CNS) infection, meningitis, and brain abscess [1, 2]. The pathogenicity of B. cereus that causes systemic infections including nosocomial BSI remains unclear. B. cereus strains G9241 [5] and 03BB102 [6], which are genetically close to B. anthracis, produce B. anthracis toxin and/or capsular toxins and cause community-onset pneumonia and fatal outcomes in healthy persons. Ba813-harboring B. cereus has been isolated from a patient with septic shock arising due to wound infection after surgery [10]. Though Ba813 is considered to a crucial genetic marker in B. cereus isolated from hospitalized patients, the distribution and clinical characteristics of Ba813-harboring B. cereus BSI in the hospital setting is unknown

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