Impact of Community-Onset Methicillin-Resistant on Bacteremia in a Central Korea Veterans Health Service Hospital.

Background: No study has examined the epidemiology of methicillin-resistant (MRSA) bacteremia in Korean veterans' hospitals. We investigated the microbiological and clinical epidemiology of bacteremia at the central Veterans Health Services (VHS) hospital in Korea.

Methods: Patients with bacteremia were consecutively enrolled from February to August 2015. Bacteremia was classified as hospital-acquired (HA), community-onset healthcare-associated (COHA), or community-acquired (CA). MRSA bacteremia risk factors were analyzed. Species identification, antimicrobial susceptibility, and presence of and were tested. Staphylococcal cassette chromosome (SCC) typing, sequence typing polymorphism typing, and multilocus sequence typing were performed. Biofilm production and δ-hemolysin activity were measured to determine function.

Results: In total, 60 patients were enrolled (30 HA, 23 COHA, and seven CA bacteremia); 44 (73.3%) had MRSA bacteremia (26 HA, 16 COHA, and two CA). MRSA bacteremia occurred more frequently in non-CA patients and those who had received antibiotic treatment within the past month (<0.05). The major MRSA strains comprised 24 ST5-2-SCCII, 11 ST72- 1-SCCIV, and five ST8-1-SCCIV strains. Of 26 2-SCCII strains, including two MSSA strains, 25 were multidrug-resistant, 18 were -positive, and 13 were -defective, whereas only five of the 18 1-SCCIV strains were multidrug-resistant, and all were -negative and -intact. 1-SCCIV and ST8-1-SCCIV strains were more likely than 2-SCCII strains to be COHA.

Conclusions: MRSA was highly prevalent in both COHA and HA bacteremia. The introduction of virulent CA-MRSA strains may be an important cause of increased HA-MRSA bacteremia in VHS hospitals.