Spread of -Positive Methicillin-Resistant SCC Type II-ST764 Among Elderly Japanese in Nonacute Care Settings.

We investigated the prevalence and molecular epidemiology of methicillin-resistant (MRSA) among 356 residents of nine long-term care facilities (LTCFs) in Japan during 2015 and 2017. In total, 800 specimens were tested and 39 MRSA isolates were recovered from 31 (8.71%) residents. PCR-based open reading frame typing (POT) and pulsed-field gel electrophoresis typing were performed for the 39 MRSA isolates; five of them showing identical pulsotypes, and POT scores were excluded in further analysis. Staphylococcal cassette chromosome (SCC) typing, multilocus sequence typing, and toxin gene detection were performed for one representative MRSA isolate per resident. Among the 34 unrelated MRSA isolates, 15 (44.1%) and 19 (55.9%) were of SCC types II and IV, respectively, and belonged to seven sequence types (STs). Among the 15 SCC II isolates, 11 (73.3%), 3, and 1 belonged to ST764 (clonal complex [CC]5), ST5 (CC5), and ST630 (CC8), respectively. Among the 19 SCC IV isolates, 13 (68.4%), 3, 2, and 1 belonged to ST1 (CC1), ST474 (CC1), ST8 (CC8), and ST380 (CC8), respectively. Among the 14 CC5 lineage-SCC II isolates, one ST5 isolate and 7 of the 11 ST764 isolates (63.6%) carried gene, and 14 (87.5%) of 16 CC1 lineage-SCC IV isolates had gene ( < 0.05). The results indicate that the -positive SCC type II-ST764 clone has spread in Japanese LTCF environments. As LTCF residents have multiple comorbidities and increased susceptibility to infections, it is necessary to monitor MRSA colonization in LTCFs through periodic screening to prevent dissemination.