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Cadmium-resistance plasmid in Staphylococcus lugdunensis
F Poitevin-Later1, F Vandenesch, K Dyke
1Hôpital Louis Pradel, Laboratoire de Bactériologie, Lyon, France.
Abstract:
Plasmids that confer resistance to cadmium (MIC > or = 125 microM), were found in 18 out of 30 independent Staphylococcus lugdunensis strains from clinical specimens. Variants that were cured of their plasmid were cadmium sensitive. Restriction endonuclease sites of a 3.2-kb cadmium-resistance plasmid of S. lugdunensis, designated pLUG10, were similar to those of pOX6, a S. aureus cadmium-resistance plasmid containing the cadB gene. Southern-blot hybridisation was performed with a probe intragenic to cadB. Hybridisation was found with the cadB probe in the cadmium-resistant S. lugdunensis isolates to the 2.9-, 3.2- and 3.7-kb plasmids. These findings suggest that cadmium-resistance in some S. lugdunensis strains is due to a gene sharing homology with the cadB gene of S. aureus.
Insights
Cadmium resistance in Staphylococcus lugdunensis is often plasmid-mediated. This resistance is linked to a gene homologous to the cadB gene found in Staphylococcus aureus.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Plasmids are extrachromosomal DNA elements that can carry genes conferring antibiotic resistance.
- Staphylococcus lugdunensis is a species of bacteria found in clinical settings.
- Cadmium is a heavy metal that can be toxic to bacteria.
Purpose of the Study:
- To investigate the prevalence and genetic basis of cadmium resistance in Staphylococcus lugdunensis.
- To determine if cadmium resistance in S. lugdunensis is plasmid-mediated.
- To compare the genetic elements responsible for cadmium resistance with known resistance mechanisms in other Staphylococcus species.
Main Methods:
- Isolation and characterization of cadmium-resistant Staphylococcus lugdunensis strains from clinical specimens.
- Plasmid curing experiments to assess the role of plasmids in cadmium resistance.
- Restriction endonuclease digestion and Southern-blot hybridization using a cadB gene probe.
Main Results:
- Eighteen out of 30 S. lugdunensis strains exhibited high-level cadmium resistance (MIC ≥ 125 µM).
- Cadmium sensitivity was restored in strains cured of their plasmids, indicating plasmid-mediated resistance.
- Restriction analysis revealed similarities between a cadmium resistance plasmid (pLUG10) and a known S. aureus cadmium resistance plasmid (pOX6).
- Southern-blot hybridization confirmed the presence of a cadB homologous gene on plasmids of varying sizes (2.9, 3.2, and 3.7 kb) in resistant S. lugdunensis isolates.
Conclusions:
- Cadmium resistance in a significant proportion of clinical Staphylococcus lugdunensis isolates is mediated by plasmids.
- The findings suggest that the cadmium resistance mechanism in these S. lugdunensis strains involves a gene homologous to the cadB gene of Staphylococcus aureus.
- This implies horizontal gene transfer or a shared evolutionary origin for cadmium resistance genes in staphylococci.