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Transfer of drug-resistance-plasmids in mixed cultures of Staphylococci
Abstract:
Transfer of pen- and chl-plasmids does not only occur between strains of Staph, aureus but also betwen strains of Staph, aureus and Staph, epidermidis. In Staph, aureus, the frequency of transfer of a tet-plasmid is less frequent than the transfer of pen- and chl-plasmids. Lysogenization of the donor strain by a sero-group-B-phage has no influence on the frequency of transfer. The transfer is not inhibited by gamma-globulin. gamma-globulin inhibits unspecifically phage adsorption and also the transduction by phage 80. The transfer is also possible when an encapsulated recipient strain is used. Phages are inhibited by the capsular material (SCHEER and KOFT, 1975); a transduction to an encapsulated strain is impossible. These results speak against a phage-mediated transfer in mixed cultures. A dilution of the incubation mixture leads to an unproportional decrease of the frequency of transfer. A prerequisite to the transfer is probably a close cell-to-cell contact.
Insights
Plasmid transfer occurs between Staphylococcus aureus and Staphylococcus epidermidis strains. Close cell-to-cell contact, not phage activity, is likely essential for this bacterial conjugation.
Area of Science:
- Microbiology
- Bacteriology
- Molecular Biology
Background:
- Plasmids, like those conferring penicillin (pen) and chloramphenicol (chl) resistance, can transfer between bacterial strains.
- Understanding plasmid transfer mechanisms is crucial for controlling antibiotic resistance spread.
Purpose of the Study:
- To investigate the frequency and mechanism of plasmid transfer between Staphylococcus aureus and Staphylococcus epidermidis.
- To determine the role of bacteriophages and cell-to-cell contact in plasmid transfer.
Main Methods:
- Conjugation experiments were performed using strains of Staphylococcus aureus and Staphylococcus epidermidis carrying different plasmids (pen, chl, tet).
- The influence of bacteriophages (lysogenization, gamma-globulin inhibition) and recipient strain characteristics (encapsulation) on transfer frequency was assessed.
- The effect of incubation mixture dilution on transfer frequency was analyzed.
Main Results:
- Penicillin and chloramphenicol plasmids transferred between S. aureus and S. epidermidis, with tet-plasmid transfer being less frequent in S. aureus.
- Lysogenization of donor strains and gamma-globulin did not affect transfer frequency, but gamma-globulin inhibited phage transduction.
- Transfer occurred even with encapsulated recipient strains, suggesting it is not phage-mediated.
- Dilution experiments indicated that close cell-to-cell contact is likely a prerequisite for plasmid transfer.
Conclusions:
- Plasmid transfer between Staphylococcus species is efficient and not solely dependent on phage activity.
- Bacterial conjugation, requiring close cell-to-cell contact, appears to be the primary mechanism for pen- and chl-plasmid transfer.
- These findings highlight the importance of cell-to-cell interactions in the dissemination of antibiotic resistance genes.