Prevalence and Characteristics of qacA/B-positive Methicillin-resistant Staphylococcus aureus (MRSA) Bloodstream Infection Isolates in a Tertiary Hospital

BACKGROUND: The increasing use of chlorhexidine (CHG) for MRSA decolonization has raised concerns about the emergence of resistance or tolerance to these agents. METHODS: We evaluated the frequency and characteristics of qacA/B chlorhexidine tolerance genes among MRSA bloodstream infection (BSI) isolates at a tertiary hospital in Korea. MRSA BSI isolates collected from 2011 to 2016 was examined for carriage of qacA/B and smr genes and high-level mupirocin resistance. Staphylococcal cassette chromosome mec (SCCmec) and spa typing was also performed. RESULTS: Of the 203 MRSA BSI isolates, 57 (28.1%) were positive for qacA/B, 6 (3.0%) were positive for smr, and 15 (7.4%) were mupirocin resistant. Table 1 shows characteristics of qacA/B-positive vs. qacA/B-negative MRSA BSI. Patients with qacA/B-positive isolates were more often diagnosed with nosocomial BSI and catheter related BSI, but were less often diagnosed with bone and soft-tissue infections. The qacA/B-positive isolates were more often resistant to mupirocin, clindamycin, and ciprofloxacin and more often had a CHG MIC of >= 4mg/L. The qacA/B-positive isolates were more likely to belong to SCCmec II or III (84.2% vs. 38.5%, P < 0.001), which are common healthcare-associated (HA) MRSA strains in Korea. Most common spa types in qacA/B positive isolates were t2460 (64.9%) and t9353 (14.0%). CONCLUSION: The qacA/B carriage among MRSA BSI isolates are not uncommon in this study and showed the features of HA-MRSA BSI. DISCLOSURES: All authors: No reported disclosures.