Community-genotype strains of methicillin-resistant Staphylococcus aureus with high-level mupirocin resistance in a neonatal intensive care unit

Abstract

AimThe aim of this study was to investigate the genotypes of mupirocin-resistant methicillin-resistant Staphylococcus aureus (MR-MRSA) isolates in our neonatal intensive care unit (NICU) and their potential source. Study designOne hundred one MRSA isolates obtained from 59 inborn and 42 outborn infants were identified and their antimicrobial susceptibility determined. Using pulse-field gel electrophoresis (PFGE) analysis, MR-MRSA isolates obtained from the neonatal patients in the NICU were compared with those from adult hospitalized in the same hospital and with community-associated MRSA (CA-MRSA) isolates recovered from different hospitals in Korea. ResultsOverall, 47% of CA-MRSA and 79% of healthcare-associated MRSA isolates exhibited high-level mupirocin resistance (HLMR). Forty-five percent of the outborn infants were considered to have CA-MRSA at the time of admission to our NICU. Most HLMR-MRSA isolates from neonates were grouped into a single cluster by PFGE analysis, and which included CA-MRSA isolates with HLMR recovered from outborn infants who were already colonized when they were transferred to our NICU. They belonged to the same PFGE group as the community-genotype strains isolated from different hospitals in Korea. HLMR-MRSA isolates from adults patients were classified as different clones. None of the attending staff in the NICU were nasal carriers. ConclusionCommunity-genotype strains of MRSA with HLMR may be imported to our NICU through obstetrics clinics and contribute to MRSA colonization or infection in facilities with a high rate of admission of outborn infants.