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Extrachromosomal control of methicillin resistance and toxin production in Staphylococcus aureus
Abstract:
All of 41 naturally occurring coagulase-positive methicillin-resistant strains of Staphylococcus aureus isolated in various laboratories were resistant to several antibiotics and were lipase-negative. Most strains produced hemolysins, and 38 strains produced enterotoxin B. Acriflavine treatment of four strains resulted in elimination of resistance to methicillin and mercury; in one strain, resistance to cadmium was also lost. Production of enterotoxin B and beta-hemolysin was eliminated in all four strains and penicillinase production was eliminated in one strain. In transduction experiments, methicillin resistance and enterotoxin B production were transferred together at a frequency of 0.2 x 10(-8) to 1.1 x 10(-8) by use of ultraviolet-induced phage lysates from naturally lysogenic methicillin-resistant strains. Cotransductions of resistance to mercury and cadmium, as well as production of penicillinase and beta-hemolysin, were obtained to some extent. The extrachromosomal character of these determinants and their possible genetic association are discussed.
Insights
Naturally occurring methicillin-resistant Staphylococcus aureus strains exhibited antibiotic resistance and toxin production. Acriflavine treatment and phage transduction experiments revealed the linked, extrachromosomal nature of methicillin resistance and enterotoxin B production.
Area of Science:
- Microbiology
- Bacterial Genetics
Background:
- Coagulase-positive Staphylococcus aureus strains are a significant concern in healthcare settings.
- Methicillin resistance and toxin production in Staphylococcus aureus are critical virulence factors.
Purpose of the Study:
- To investigate the genetic basis and linkage of antibiotic resistance and toxin production in naturally occurring methicillin-resistant Staphylococcus aureus (MRSA).
- To determine if methicillin resistance and enterotoxin B production are co-located on transferable genetic elements.
Main Methods:
- Phenotypic characterization of 41 MRSA strains for antibiotic resistance, lipase activity, hemolysin production, and enterotoxin B production.
- Acriflavine treatment to assess the effect on resistance and toxin production.
- Transduction experiments using ultraviolet-induced phage lysates to transfer genetic traits.
Main Results:
- All 41 MRSA strains were resistant to multiple antibiotics and lipase-negative. Most produced hemolysins, and 38 produced enterotoxin B.
- Acriflavine treatment eliminated methicillin resistance and enterotoxin B production in tested strains.
- Methicillin resistance and enterotoxin B production were co-transduced, suggesting a genetic association.
Conclusions:
- Methicillin resistance and enterotoxin B production in these MRSA strains are likely linked and carried on extrachromosomal elements.
- The findings have implications for understanding the evolution and spread of virulence and resistance in Staphylococcus aureus.