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Chromosomal map location of the methicillin resistance determinant in Staphylococcus aureus
Abstract:
Three-factor genetic crosses performed by transformation have shown that the methicillin resistance determinant of Staphylococcus aureus strain DU4916 (the mec-4916 marker) is linked to a novobiocin resistance (Novr) marker (nov-142) and mutational sites affecting pyrimidine (pyr-141), purine (pur-102), and histidine (hisG15) biosynthesis in S. aureus strain 8325. The linkage group thus defined is pyr-141-hisG15-nov-142-pur-102-mec-4916. Phage 80alpha previously propagated on a novobiocin-resistant, methicillin-sensitive (Mecs) 8325 strain was used to infect 21 novobiocin-sensitive, methicillin-resistant clinical isolates (including strain DU4916). Among the novobiocin-resistant transductants so obtained from each recipient, between 1 and 5% were methicillin sensitive (reflecting cotransduction of Novr and Mecs). These results are consistent with the genetic determinant of methicillin resistance having a single chromosomal locus in most, if not all, strains of S. aureus.
Insights
Methicillin resistance in Staphylococcus aureus is genetically linked to novobiocin resistance and other markers. This suggests methicillin resistance often resides in a single chromosomal location.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Methicillin resistance in Staphylococcus aureus (MRSA) is a significant public health concern.
- Understanding the genetic basis of antibiotic resistance is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the genetic linkage of the methicillin resistance determinant (mec-4916) in Staphylococcus aureus.
- To determine the chromosomal location of the genetic determinant for methicillin resistance.
Main Methods:
- Three-factor genetic crosses using transformation in Staphylococcus aureus.
- Phage transduction experiments using phage 80alpha to cotransduce antibiotic resistance markers.
- Analysis of linkage between methicillin resistance, novobiocin resistance, and auxotrophic markers.
Main Results:
- The methicillin resistance determinant (mec-4916) was found to be linked to novobiocin resistance (nov-142) and markers for pyrimidine, purine, and histidine biosynthesis.
- A defined linkage group was established: pyr-141-hisG15-nov-142-pur-102-mec-4916.
- Cotransduction of novobiocin resistance and methicillin sensitivity occurred in 1-5% of transductants, supporting the linkage.
Conclusions:
- The genetic determinant for methicillin resistance in Staphylococcus aureus is linked to other chromosomal markers.
- These findings are consistent with the methicillin resistance determinant residing in a single chromosomal locus in most S. aureus strains.