Comparison of USA300 with non-USA300 methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit

Abstract

Objectives: Reports of USA300 methicillin-resistant Staphylococcus aureus (MRSA) strain were still scarce in neonatal intensive care units (NICUs) and the relationship of USA300 MRSA to clinical infections is still controversial. The primary outcome was the incidence of MRSA infections caused by the USA300 and non-USA300 strains at a NICU in Japan. Methods: This retrospective cohort study was conducted between November 2011 and October 2016 at Tokyo Metropolitan Children’s Medical Center in Japan. All MRSA isolated after 48 h of hospitalization were included for analysis by pulsed-field gel electrophoresis (PFGE) using the standard USA300 strain. Genes were tested for Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME). A whole genome sequence was performed for representative isolates of USA300. Results: In total, 109 MRSA isolates were included for analysis. PFGE classified 34 and 75 isolates of USA300 and non-USA300 MRSA, respectively. Both PVL and ACME genes were detected in USA300 and non-USA300 strains at rate of 100% (34/34) and 5.3% (4/75), respectively (P < 0.05). There was no statistically significant difference in the proportion of clinical diseases between USA- 300 and non-USA 300 strains. Conclusions: Infants with USA300 MRSA infection did not differ significantly from those with non-USA300 MRSA infection. Keywords: Methicillin-resistant Staphylococcus aureus, Neonatal intensive care unit, USA300, Panton-Valentine leukocidin, Arginine catabolic mobile element