title: Changing molecular epidemiology and high rates of mupirocin resistance among meticillin-resistant Staphylococcus aureus in Singaporean hospitals.
abstract: A prospective cross-sectional study was performed to determine the continuing shift in the molecular epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) in Singapore. In total, 666 MRSA isolates from screening cultures performed between 7 and 20 January 2013 were obtained from all seven public sector hospitals in Singapore and were subjected to molecular typing using multilocus variable-number tandem-repeat fingerprinting with confirmatory multilocus sequencing typing for clustered isolates. Isolates were also tested for the presence of the orfX-ACME insert and the high-level mupirocin resistance gene ileS-2. The major circulating clones in Singaporean hospitals were ST22 (63.2%), ST45 (18.9%) and ST239 (10.7%). The orfX-ACME insert was only found in ST239 isolates (31/71, 43.7%), but ileS-2 was found in 207 (31.1%) of the MRSA isolates, varying between 10.0% and 47.8% among the hospitals. In conclusion, the molecular epidemiology of MRSA in Singaporean hospitals has continued to change, with ST45 now replacing ST239 in addition to the ongoing replacement of the latter by ST22. Although a greater proportion of ST239 isolates carry the orfX-ACME insert, the actual clinical impact may be marginal as ST239 MRSA continues to decline. Finally, high-level mupirocin resistance rates are remarkably high in local healthcare-associated MRSA, with implications for MRSA decolonisation and infection prevention. Further surveillance is required to monitor the changing epidemiological trends.
authors.affiliation: Department of Medicine, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 10, Singapore 119228, Singapore.
authors.forename: Pei Yun
authors.initials: PY
authors.lastname: Hon
authors.affiliation: Department of Medicine, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 10, Singapore 119228, Singapore; Department of Pathology, Singapore General Hospital, The Academia, 20 College Road, Singapore 169856, Singapore.
authors.forename: Tse Hsien
authors.initials: TH
authors.lastname: Koh
authors.affiliation: Department of Laboratory Medicine, Changi General Hospital, 2 Simei Street 3, Singapore 529889, Singapore.
authors.forename: Thean Yen
authors.initials: TY
authors.lastname: Tan
authors.affiliation: Department of Laboratory Medicine, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Prabha
authors.initials: P
authors.lastname: Krishnan
authors.affiliation: Department of Laboratory Medicine, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Janice Wai-Yeng
authors.initials: JW
authors.lastname: Leong
authors.affiliation: Department of Laboratory Medicine, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 10, Singapore 119228, Singapore.
authors.forename: Roland
authors.initials: R
authors.lastname: Jureen
authors.affiliation: Department of Laboratory Medicine, Khoo Teck Puat Hospital, 90 Yishun Central, Singapore 768828, Singapore.
authors.forename: Joey
authors.initials: J
authors.lastname: Chan
authors.affiliation: Department of Laboratory Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore 229899, Singapore.
authors.forename: Nancy Wen-Sim
authors.initials: NW
authors.lastname: Tee
authors.affiliation: Department of Laboratory Medicine, Jurong General Hospital, 378 Alexandra Road, Singapore 159964, Singapore.
authors.forename: Jagadeesan
authors.initials: J
authors.lastname: Murugesh
authors.affiliation: Department of Pathology, Singapore General Hospital, The Academia, 20 College Road, Singapore 169856, Singapore.
authors.forename: Kian Sing
authors.initials: KS
authors.lastname: Chan
authors.affiliation: Department of Medicine, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 10, Singapore 119228, Singapore. Electronic address: liyang_hsu@yahoo.com.
authors.forename: Li Yang
authors.initials: LY
authors.lastname: Hsu
keywords: Epidemiology; High-level mupirocin resistance; Meticillin-resistant Staphylococcus aureus; ileS-2