Background: This study aimed to investigate the effects of stepwise strengthening of methicillinresistant Staphylococcus aureus (MRSA) infection control on the acquisition and identification of risk factors for acquiring MRSA in children undergoing cardiac surgery in the paediatric intensive care unit (PICU).
Methods: Patients who underwent surgery for congenital heart disease between June 2017 and February 2019 were included. As a step-by-step MRSA infection control, step 1 was an active surveillance culture, step 2 was to add preemptive contact isolation, and step 3 was to add a chlorhexidine bed bath. In addition, the medical records of 346 participants were reviewed retrospectively. The difference between the occurrence of MRSA acquisition and timing was analysed using the Kruskal–Wallis, chi-square, and Fisher’s exact tests and the risk factors for children with MRSA were confirmed using logistic regression analysis.
Results: MRSA colonisation occurred in eight patients (6.4%) in stage 1, five (4.0%) in stage 2, and three (3.2%) in stage 3. MRSA infection occurred in one patient (0.8%) admitted in stage 2. The median day of occurrence of MRSA colonisation was 8.5 days in stage 1, 8 in stage 2, and 17 in stage 3. Steroid exposure was an independent factor influencing MRSA acquisition.
Conclusion: Due to the small number of participants and short intervention period, the stepup intervention did not significantly reduce MRSA acquisition. However, as MRSA infection control was strengthened step-by-step, MRSA acquisition tended to decrease.

Keywords: Chlorhexidine, Methicillin-resistant Staphylococcus aureus, Patient isolation, Pediatric intensive care unit, Thoracic surgery