Plasmid DNA content of multiresistant Staphylococcus aureus strains

Area of Science:

• Microbiology
• Epidemiology
• Molecular Genetics

Background:

• Multiresistant Staphylococcus aureus, including methicillin-resistant strains, exhibit diverse resistance patterns.
• Traditional epidemiological markers like antibiotic resistance and serotyping are often used.
• Molecular and genetic properties of plasmid DNA offer additional insights into strain relationships.

Purpose of the Study:

• To conduct an epidemiological study of two groups of S. aureus strains in France.
• To investigate the role of plasmid DNA in the spread of new resistance characters.
• To explore potential phylogenetic relationships among strains based on plasmid content.

Main Methods:

• Analysis of resistance patterns to antibiotics and metal ions.
• Characterization of plasmid DNA content and restriction cleavage patterns.
• Epidemiological sampling of S. aureus strains since 1975.

Main Results:

• Tm-SgR strains showed resistance to gramin components A and B (Sg), encoded by a single plasmid, with some strains suggesting clonal origin.
• Tob-GenR strains exhibited resistance to aminoglycosides like tobramycin (Tob) and gentamicin (Gen), linked to a 22-kb plasmid.
• Most resistance characters, including new ones, are likely encoded by chromosomal genes, but plasmid spread is implicated in specific resistance traits.

Conclusions:

• Plasmid DNA content can indicate close phylogenetic relationships and clonal spread among S. aureus strains.
• The spread of novel resistance characters, such as Sg and aminoglycoside resistance, may be associated with the dissemination of specific ancestral plasmids or clones.
• Understanding the genetic basis and epidemiological spread of resistance is crucial for controlling multiresistant bacteria.