Abstract
Background/Objectives:Staphylococcus haemolyticus is a common commensal bacterium that has emerged as an important nosocomial pathogen. Its multi-antibiotics resistance presents substantial therapeutic challenges in healthcare settings worldwide. Despite its growing clinical relevance, most investigations into antimicrobial resistance determinants have been focused on Staphylococcus aureus or Staphylococcus epidermidis, leaving S. haemolyticus comparatively understudied. This study aimed to elucidate the genetic basis of multi-drug resistance by characterizing mobile genetic elements associated with predominant S. haemolyticus clones circulating in Taiwan. Methods: From 2010 to 2017, 140 clinical targeted isolates of S. haemolyticus were obtained from individual patients. Two representative strains, SH53 (ST3) and SH51 (ST42), were sequenced using the PacBio(TM) platform. The structural organization of SCCmec cassettes and phage-associated resistance islands in the remaining 138 isolates was analyzed by polymerase chain reaction (PCR) using specifically designed primers. Results: Of the 140 isolates, 92 (65.7%) were ST42 and 48 (34.3%) were ST3. PCR analysis showed that over two-thirds harbored heavy metal resistance genes. cadD, cadX, arsC, arsB, and arsR occurred in 90.2% of ST42 isolates, with copA in 71.7%. In ST3, these five genes were present in 89.6%, and copA in 64.6%. Fusidic acid (FA) resistance was more frequent in ST42 (46.7%) than ST3 (22.9%) (p = 0.015). Only one ST42 isolate carried fusC. The remaining 52 FA-resistant isolates contained a type I aj1-leader peptide (LP)-fusB structure downstream of smpB, except for a single ST42 isolate with the type IV structure. Conclusions: MDR ST42 S. haemolyticus carrying SCCmec cassettes with heavy metal resistance genes and phage-related islands carrying type I aj1-leader peptide (LP)-fusB structures may represent emerging opportunistic pathogens in Taiwan. Continued longitudinal surveillance is warranted to track the evolution of resistance-associated mobile elements under selective antimicrobial pressure.