Factors associated with persistent methicillin-resistant staphylococcal bacteremia after initiation of anti-MRSA therapy in the NICU: A retrospective observational study

Background Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCoNS) are important causes of bacteremia in neonatal intensive care units (NICUs). However, clinical factors associated with persistent bacteremia after initiation of anti-MRSA therapy in NICU patients remain poorly defined. Methods We conducted a retrospective observational study of infants with MRSA or MRCoNS bacteremia admitted to a tertiary NICU between 2016 and 2025. Persistent bacteremia was defined as a positive follow-up blood culture on or after day 2 of initial anti-MRSA therapy. Multivariable logistic regression was performed to identify factors independently associated with persistent bacteremia. Results 49 episodes of bacteremia were included, of which 16 (33%) met the criteria for persistent bacteremia. Younger postnatal age at bacteremia onset (adjusted odds ratio per 7-day decrease, 1.32; 95% confidence interval, 1.08–1.85; p = 0.001) and absence of central venous catheter removal or replacement within 2 days of starting initial anti-MRSA therapy (adjusted odds ratio, 11.20; 95% confidence interval, 2.16–86.60; p = 0.003) were independently associated with persistent bacteremia after initiation of anti-MRSA therapy. Conclusions Younger postnatal age and the absence of central venous catheter removal or replacement were independently associated with persistent bacteremia after initiation of anti-MRSA therapy in NICU patients with MRSA or MRCoNS bacteremia. These findings may facilitate early identification of NICU patients at increased risk of persistent bacteremia and support closer monitoring and timely reassessment of treatment response. Prospective multicenter studies are warranted to validate these findings and establish optimal treatment strategies.