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Interaction between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus
1Department of Microbiology, University Hospital Lewisham, London SE13 6LH, UK. gopal.rao@uhl.nhs.uk
The Journal of Hospital Infection
|October 8, 2003
Summary
Endemic methicillin-resistant Staphylococcus aureus (EMRSA) strains can outcompete and eliminate methicillin-sensitive Staphylococcus aureus (MSSA) in vitro. This complex interaction influences MRSA colonization in patients.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Interactions
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Understanding the competitive dynamics between MRSA and methicillin-sensitive Staphylococcus aureus (MSSA) is crucial for infection control.
Purpose of the Study:
- To investigate the in vitro interaction between various strains of endemic MRSA (EMRSA) and MSSA.
- To determine if EMRSA strains can outcompete MSSA strains in mixed cultures.
Main Methods:
- In vitro incubation of mixed bacterial cultures of MSSA and EMRSA strains.
- Subculturing at one, two, and seven days.
- Assessment of MRSA proportion in randomly selected colonies.
Main Results:
- All tested EMRSA strains (1, 3, 15, 16) rapidly outgrew and eradicated the reference MSSA strain (NCTC 11561) within 24 hours.
- Interactions between patient-derived MSSA (PMSSA) strains and EMRSA were variable.
- Specific EMRSA strains (1 and 3) significantly outcompeted PMSSA strains 1 and 2, while EMRSA 15 showed modest growth, and EMRSA 16 did not increase proportionally.
Conclusions:
- A complex and strain-specific interaction exists between EMRSA and MSSA.
- The competitive ability of EMRSA against MSSA may play a role in MRSA colonization dynamics in patients.