Risk factors for methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in patients with or without prior...

Methicillin-resistant Staphylococcus aureus (MRSA), a major cause of healthcare-associated infections, is endemic in hospitals. Despite interventions, hospital-onset (HO)-MRSA bacteraemia rates remain high. Infection prevention and control efforts mainly target colonised patients, yet non-colonised patients also carry distinct risks. Identifying risk differences is essential for prevention.

We conducted a case-control study of 253 HO-MRSA cases and 253 controls matched by month, specialty, and status at 2 tertiary hospitals (2016-2022). Multi-nomial regression identified risk factors.

Among colonised patients, risk factors were immunosuppressive therapy (relative risk ratio 3.53, 95% confidence interval [CI]: 1.80-6.91), fluoroquinolone exposure (RRR: 2.29, 95% CI: 1.08-4.84), glycopeptide exposure (RRR: 2.57, 95% CI: 1.23-5.39), thrombophlebitis (RRR: 21.25, 95% CI: 5.67-79.58), and peripherally inserted central catheter (PICC) presence (RRR: 7.68, 95% CI: 1.39-42.54). Among non-colonised patients, risk factors were days at risk 22-28 (RRR: 3.57, 95% CI: 1.05-12.14), immunosuppressive therapy (RRR: 2.37, 95% CI: 1.13-4.97), fluoroquinolone exposure (RRR: 2.19, 95% CI: 1.06-4.53), glycopeptide exposure (RRR: 2.51, 95% CI: 1.18-5.31), thrombophlebitis (RRR: 20.80, 95% CI: 4.35-99.35), and chronic haemodialysis (RRR: 3.08, 95% CI: 1.03-9.16). Most risk factors were similar, but prolonged stay and haemodialysis were unique to non-colonised patients and presence of PICC to colonised patients.

These differences challenge assumptions of uniform risk and support tailored prevention efforts. To mitigate bacteraemia risk, hospitals can reinforce PICC care in colonised patients and implement repeat screening for non-colonised patients and haemodialysis patients with prolonged hospitalisation.