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Lee-Chung Lin,1 Mao-Cheng Ge,1 Tsui-Ping Liu,1 Jang-Jih Lu1–3 1Department of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan; 2Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan; 3Department of Medicine, College of Medicine, Chang Gung University, Taoyuan, TaiwanCorrespondence: Jang-Jih LuDepartment of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, No. 5, Fu-Shin Street, Kweishan, Taoyuan 333, TaiwanEmail janglu45@gmail.comIntroduction: The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) type SCCmec IV or V is increasing in Taiwan. It has been suggested that the surface protein SasX is responsible for their transmission. However, the sasX gene was not detected in our SCCmec IV or V isolates. Since sasX was originally found in S. epidermidis and believed to be transferred to S. aureus by a prophage, studies were conducted to detect and type this prophage in our clinical isolates.Materials and Methods: A total of 1192 MRSA isolates collected from 2006 to 2014 were examined. Multiplex PCRs were performed to determine SCCmec, sasX, and prophage types.Results: The prevalence of SCCmec IV and V isolates was increased in recent years (from 2006 to 2014). The sasX gene was present in most SCCmec III isolates but was absent in SCCmec IV or V isolates. The Sa5 prophage was found only in SCCmec IV and SCCmec V (or Vt) isolates, and the Sa6 prophage was mainly present in SCCmec III isolates. MRSA isolates harboring prophage combinations Sa1, Sa2, and Sa3; Sa2 and Sa3; Sa2, Sa3, and Sa7; or Sa2 and Sa7 were mainly of SCCmec II, and those that harbored prophage combinations Sa3 and Sa6; Sa3, Sa6, and Sa7; or Sa3 and Sa7 were mostly of SCCmec III. The numbers of SCCmec II isolates containing prophages Sa2, Sa3, and Sa7 and those of SCCmec III isolates containing prophages Sa3 and Sa6 or Sa3, Sa6, and Sa7 were decreased from 2010 to 2014. The number of SCCmec IV isolates with prophage Sa3 or prophages Sa3 and Sa5 was decreased, but that of those with prophage Sa6 or prophages Sa2 and Sa3 was increased from 2010 to 2014.Conclusion: The sasX gene was found to play no role in clonal selection of MRSA. The finding that different SCCmec types of MRSA harbored different types of prophages suggests that these prophages may affect the survival and clonal expansion of certain types of MRSA.Keywords: MRSA, SCCmec, sasX, prophage

Lee-Chung Lin,1 Shih-Cheng Chang,1,2 Mao-Cheng Ge,1 Tsui-Ping Liu,1 Jang-Jih Lu1–3 1Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan; 2Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan; 3Department of Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan Abstract: Prolonged vancomycin usage may cause methicillin-resistant Staphylococcus aureus to become vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA). Mechanisms of vancomycin resistance of VISA and hVISA are still unclear. In this study, analyses of nucleotide sequence variations in 30 vancomycin-sensitive S. aureus (VSSA), 41 hVISA and 16 VISA isolates revealed 29 single-nucleotide variations in 12 genes (fmtC, graR, graS, htrA, mecA, pbp2, pbp4, srtA, tcaA, upps, vicK and vraR) that are related to cell wall synthesis or the two-component system. Six of these 29 single-nucleotide variations were novel and resulted in the following amino acid changes: Q692E in FmtC; T278I, P306L and I311T in HtrA; and I63V and K101E in Upps. Since P306L and I311T in HtrA and I63V in Upps were present in the majority (76.7%–86.7%) of VSSA isolates, these three amino acid variations may not be associated with vancomycin resistance. The other three amino acid variations (T278I in HtrA, K101E in Upps and Q692E in FmtC) were present in the majority (87.5%–93.8%) of hVISA and VISA isolates, but only in a small number (22.9%–25.7%) of VSSA isolates, suggesting that they are associated with vancomycin resistance. Keywords: MRSA, VSSA, hVISA, VISA