Related Experiment Videos
Molecular epidemiology of macrolides-lincosamides-streptogramin B resistance in Staphylococcus aureus and
Abstract:
Macrolides-lincosamides-streptogramin B (MLS) resistance is commonly found in Staphylococcus aureus and coagulase-negative staphylococci (22 and 45%, respectively, among isolates from three New Jersey hospitals). We have examined representative subsets of 107 MLS-resistant isolates for the molecular nature of the resistance determinant, the erm gene, by dot blot and Southern hybridization analysis. All of 35 S. aureus isolates examined and 39 of 42 coagulase-negative isolates examined were found to harbor the ermA or ermC evolutionary variant. Genes of the ermC class occurred exclusively on a small plasmid similar to or indistinguishable from one (pNE131) previously described in S. epidermidis. Genes of the ermA class occurred exclusively in the chromosome, and restriction patterns indicated that they were part of a transposon, Tn554, characteristic of the classical S. aureus ermA strain. Unlike S. aureus ermA strains examined previously, which harbor Tn554 at a single specific (primary) site, four of our S. aureus isolates had second inserts at different chromosomal sites. The majority of our coagulase-negative isolates had two or more inserts, neither of which occurred at the classical primary site and many of which differed from one another in location (as inferred from restriction patterns). Coagulase-negative staphylococci constitute a large reservoir of the ermA and ermC class of determinants, with clear potential for interspecies spread.
Insights
Macrolides-lincosamides-streptogramin B (MLS) resistance is prevalent in Staphylococcus aureus and coagulase-negative staphylococci. The ermA and ermC genes, responsible for MLS resistance, are found on plasmids or integrated into the chromosome, with potential for interspecies spread.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Macrolides-lincosamides-streptogramin B (MLS) resistance is a significant clinical concern in Staphylococcus aureus and coagulase-negative staphylococci.
- Prevalence rates of MLS resistance in these bacteria were observed at 22% and 45%, respectively, in isolates from New Jersey hospitals.
Purpose of the Study:
- To investigate the molecular basis of MLS resistance in Staphylococcus aureus and coagulase-negative staphylococci.
- To characterize the erm gene variants and their genetic location (plasmid or chromosome) in resistant isolates.
Main Methods:
- Dot blot and Southern hybridization analyses were employed to detect and characterize the erm gene variants.
- Restriction pattern analysis was used to determine the genomic location and organization of the erm genes, including transposon structures.
Main Results:
- All examined Staphylococcus aureus isolates (35/35) and a majority of coagulase-negative isolates (39/42) harbored either the ermA or ermC gene variants.
- ermC genes were found exclusively on plasmids, while ermA genes were located on the chromosome, often within the Tn554 transposon.
- Multiple chromosomal inserts of Tn554 were observed in Staphylococcus aureus, and coagulase-negative staphylococci frequently displayed multiple, distinct ermA inserts.
Conclusions:
- Coagulase-negative staphylococci serve as a substantial reservoir for ermA and ermC resistance determinants.
- The genetic mobility and varied locations of these resistance genes suggest a significant potential for interspecies spread within staphylococcal populations.