Ba813harboringbacillus Cereus, Genetically Closely Related Tobacillus Anthracis, Causing Nosocomial Bloodstream Infection: Bacterial Virulence Factors And Clinical Outcome

Bacillus cereuscommonly causes catheter-related bloodstream infections (BSIs) in hospital settings, and occasionally occurs fatal central nervous system (CNS) complications.B.cereusharboringBa813, a specific chromosomal marker ofBacillus anthracis, has been found in patients with severe infection and nosocomial BSI. However, the bacteriological profile and clinical feature ofBa813(+)B.cereusare unclear. Fifty-three patients withB.cereusBSI were examined. Isolates were evaluated forBa813,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.cereusisolates including five sequence types possessedBa813and were classified into Clade-1/Cereus-III lineage which is most closely related to Anthracis lineage. NoB.cereuspossessedB.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-2B.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 tenBa813(-) 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 thatBa813-harboringB.cereusstrains, genetically closely related toB.anthracis, were abundant amongB.cereusstrains in the hospital setting, and might cause catheter-related nosocomial BSI. However, it did not affect the clinical outcomes.