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Updated: Jan 13, 2026
Heuristic Mining of Hierarchical Genotypes and Accessory Genome Loci in Bacterial Populations
Published on: December 7, 2021
Multidrug-Resistant Staphylococcus haemolyticus ST42 Carrying ΨSCCmec57395-like SCCmec and Resistant Islands with
Cheng-Mao Ho1,2,3,4, Lee-Chung Lin5, Yu-Hsiang Ou5
1Division of Clinical Pathology, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427213, Taiwan.
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 PacBioTM 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.
Insights
Multi-drug resistant Staphylococcus haemolyticus clones in Taiwan carry mobile genetic elements conferring heavy metal and fusidic acid resistance. These findings highlight emerging opportunistic pathogens and the need for ongoing surveillance of resistance evolution.
Area of Science:
- Molecular biology and microbiology
- Genetics of antimicrobial resistance
- Nosocomial infections
Background:
- Staphylococcus haemolyticus is an emerging nosocomial pathogen with significant multi-antibiotic resistance.
- Antimicrobial resistance determinants in S. haemolyticus are understudied compared to S. aureus and S. epidermidis.
- Understanding resistance mechanisms is crucial for managing healthcare-associated infections.
Purpose of the Study:
- To investigate the genetic basis of multi-drug resistance in prevalent S. haemolyticus clones in Taiwan.
- To characterize mobile genetic elements, including SCCmec cassettes and phage-associated islands, associated with resistance.
- To elucidate the mechanisms of resistance to heavy metals and fusidic acid.
Main Methods:
- Analysis of 140 clinical S. haemolyticus isolates collected between 2010 and 2017.
- Whole-genome sequencing of two representative strains (ST3 and ST42) using PacBio platform.
- Polymerase chain reaction (PCR) to analyze SCCmec cassettes and phage-associated resistance islands in remaining isolates.
Main Results:
- Two predominant sequence types (STs) were identified: ST42 (65.7%) and ST3 (34.3%).
- Over two-thirds of isolates harbored heavy metal resistance genes (e.g., cadD, cadX, arsC, arsB, arsR, copA).
- Fusidic acid resistance was significantly higher in ST42 (46.7%) than ST3 (22.9%), primarily mediated by type I aj1-leader peptide (LP)-fusB structures.
Conclusions:
- Multi-drug resistant ST42 S. haemolyticus strains carrying SCCmec cassettes and phage-related islands represent potential emerging opportunistic pathogens in Taiwan.
- The co-occurrence of heavy metal and fusidic acid resistance genes on mobile elements facilitates resistance dissemination.
- Longitudinal surveillance is essential to monitor the evolution of resistance-associated mobile elements under antimicrobial pressure.
