<i>Bacillus cereus</i> biofilm formation on central venous catheters of hospitalised cardiac patients

Formation of bacterial biofilms is a risk with many <i>in situ</i> medical devices. Biofilm-forming <i>Bacillus</i> species are associated with potentially life-threatening catheter-related blood stream infections in immunocompromised patients. Here, bacteria were isolated from biofilm-like structures within the lumen of central venous catheters (CVCs) from two patients admitted to cardiac hospital wards. Isolates belonged to the <i>Bacillus cereus</i> group, exhibited strong biofilm formation propensity, and mapped phylogenetically close to the <i>B. cereus</i> emetic cluster. Together, whole genome sequencing and quantitative PCR confirmed that the isolates constituted the same strain and possessed a range of genes important for and up-regulated during biofilm formation. Antimicrobial susceptibility testing demonstrated resistance to trimethoprim-sulphamethoxazole, clindamycin, penicillin and ampicillin. Inspection of the genome revealed several chromosomal β-lactamase genes and a sulphonamide resistant variant of <i>folP</i>. This study clearly shows that <i>B. cereus</i> persisting in hospital ward environments may constitute a risk factor from repeated contamination of CVCs.