Contemporary Methicillin-Resistant Staphylococcus aureus Clones in Hong Kong

Two hundred nonduplicate methicillin-resistant Staphylococcus aureus (MRSA) isolates causing bacteremia in patients in four major Hong Kong hospitals during the period 2000 to 2001 were characterized by antibiogram, pulsed-field gel electrophoresis (PFGE) using SmaI restriction enzymes, and determination of staphylococcal cassette chromosome mec (SCC mec ) types. Nine PFGE types, A to I, were obtained. PFGE type A constituted 50% (99/200) of all isolates and was present in isolates from all four hospitals. PFGE types A to E, had previously been identified as the major types at one of the hospitals from 1988 to 2000. The majority had a resistance profile to tetracycline (T), erythromycin (E), clindamycin (D), gentamicin (G), tobramycin (To), and ciprofloxacin (Ci), and belonged to SCC mec type III; and representatives belonged to clonal complex 239 (CC239) (MRSA with SCC mec type III and sequence type 239, designated ST239-MRSA-III). PFGE types F to I were new patterns that had not been previously identified in isolates from Hong Kong. PFGE type F constituted 18% (35/200) of MRSAs, had resistance profile TEGToCi, and belonged to CC5 (ST5-MRSA-II). PFGE type G included 13% (26/200) of MRSAs, had resistance profile TECi, and belonged to CC45 with SCC mec type I or II. PFGE type H had characteristics similar to those of CC239, while PFGE type I included three isolates, two of which expressed resistance to oxacillin and fusidic acid only. Two of these strains had SCC mec IVa and carried sequence type 389, with a multilocus sequence typing allelic profile of 3-35-19-2-20-26-39. Contemporary MRSAs causing bacteremia in Hong Kong hospitals belong to three clonal complexes (CC5, CC45, and CC239). The most prevalent MRSA clone in Hong Kong belongs to CC239, with PFGE types A to E and H, SCC mec type III, ST239, and a resistance profile of TEDGToCi.