Characteristics and distribution of plasmids in a clonally diverse set of methicillin-resistant Staphylococcus aureus...

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global health threat.
• Understanding the genetic factors contributing to MRSA's diversity and virulence is crucial for effective treatment and control.
• Plasmids are known to carry important genes, including those for antibiotic resistance and virulence factors.

Purpose of the Study:

• To investigate and compare the plasmid profiles of MRSA strains belonging to different clonal clusters (CCs).
• To identify specific plasmids associated with particular MRSA lineages.
• To elucidate the role of plasmids in the evolution of MRSA clonal diversity.

Main Methods:

• Collection of MRSA isolates from 15 Czech hospitals between 2000-2008.
• Detection and characterization of plasmid DNA using techniques such as restriction endonuclease analysis, plasmid elimination, DNA hybridization, and sequencing.
• Classification of MRSA strains into different clonal clusters (CCs).

Main Results:

• Plasmid DNA was detected in 89% of the analyzed MRSA strains, with 33 strains harboring multiple plasmid types.
• A total of 24 distinct plasmid types, ranging from 1.3 to 55 kb, were identified.
• Conjugative, erythromycin resistance, and enterotoxin D encoding plasmids were found across different CCs.
• Chloramphenicol and tetracycline resistance plasmids, along with most penicillinase and cryptic plasmids, were lineage-specific.
• pUSA300-like plasmids were exclusively found in USA300 clone strains.

Conclusions:

• Significant diversity in plasmid content exists among MRSA strains from different clonal clusters.
• Specific plasmids are associated with particular MRSA lineages, suggesting horizontal gene transfer and adaptation.
• Plasmids play a substantial role in the evolution and diversification of MRSA clonal lineages.