Related Experiment Video
Updated: Feb 22, 2026
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Characterization of two novel variants of staphylococcal cassette chromosome mec elements in oxacillin-resistant
Shih-Cheng Chang1,2, Ming-Hsun Lee3, Chun-Fu Yeh3
1Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Objectives:
Staphylococcus lugdunensis, a species of CoNS, has become an important hospital pathogen because of increasing resistance to β-lactam antibiotics such as methicillin and oxacillin. Methicillin resistance is mainly due to the acquisition of the staphylococcal cassette chromosome (SCC) mec (SCCmec). Little is known about the structure of SCCmec in methicillin- or oxacillin-resistant CoNS.
Methods:
WGS was performed to determine the structure of SCCmec elements of two clinical S. lugdunensis isolates: CMUH-22 and CMUH-25.
Results:
These elements were found to be flanked by DRs and IRs with unique mosaic structures and a common integration site in the 3' end of the rlmH gene. The sequences of the regions located between rlmH and the ISSau4-like transposase genes of both elements were similar to those of SCCmec Vt of Staphylococcus aureus PM1. The SCCmec (type V, 5C2&4) of CMUH-25 harboured a novel ccrC complex and a C2-like mec complex in opposite orientations, similar to the type V SCCmec of S. aureus WIS. The sequences of the ccrA4B4 genes and J1 and J2 regions of CMUH-25 were similar to those of the SCC element of Staphylococcus haemolyticus NCTC 11042. In contrast, portions of the sequence of the J1 region of type Vt (5C2) SCCmec in strain CMUH-22 were highly similar to portions of those of Staphylococcus epidermidis RP62A and the composite SCCmec type V of S. aureus WAMRSA40.
Conclusions:
These observations suggest that the SCCmec elements of CMUH-25 and CMUH-22 evolved separately and assembled through different recombination events.
Insights
The staphylococcal cassette chromosome mec (SCCmec) elements in resistant Staphylococcus lugdunensis isolates show unique structures, suggesting separate evolutionary paths and recombination events. This research clarifies SCCmec diversity in this emerging hospital pathogen.
Area of Science:
- Microbiology
- Molecular Biology
- Genomics
Background:
- Staphylococcus lugdunensis is an emerging hospital pathogen.
- Increasing resistance to beta-lactam antibiotics, like methicillin and oxacillin, is observed.
- Methicillin resistance is often due to staphylococcal cassette chromosome mec (SCCmec) acquisition.
- SCCmec structures in resistant CoNS are not well-understood.
Purpose of the Study:
- To determine the SCCmec structures in two clinical isolates of Staphylococcus lugdunensis (CMUH-22 and CMUH-25).
- To investigate the genetic makeup and evolutionary origins of SCCmec elements in these isolates.
Main Methods:
- Whole Genome Sequencing (WGS) was employed.
- Analysis focused on identifying the structure and genetic elements within the SCCmec regions.
- Comparative sequence analysis was performed against known SCCmec elements from other staphylococcal species.
Main Results:
- SCCmec elements in both isolates were flanked by direct repeats (DRs) and inverted repeats (IRs).
- A common integration site was identified at the 3' end of the rlmH gene.
- CMUH-25 harbored a novel ccrC complex and a C2-like mec complex in opposite orientations.
- CMUH-22 showed sequence similarities to SCCmec Vt and elements from Staphylococcus epidermidis and Staphylococcus aureus.
Conclusions:
- The SCCmec elements in CMUH-25 and CMUH-22 appear to have evolved independently.
- Different recombination events likely contributed to the assembly of these SCCmec elements.
- This diversity highlights the complex evolutionary dynamics of antibiotic resistance in Staphylococcus lugdunensis.
