Cefoxitin susceptibility testing is used to determine the resistance of bacterial strains, particularly Staphylococcus aureus, to cefoxitin, a cephamycin antibiotic. This test helps guide appropriate antibiotic therapy.
Method
- Disk Diffusion (Kirby-Bauer) Test:
- A cefoxitin disk is placed on an agar plate inoculated with the bacterial strain.
- Incubate for 18-24 hours.
- Measure the zone of inhibition around the disk.
- Minimum Inhibitory Concentration (MIC) Test:
- Determine the lowest concentration of cefoxitin that inhibits visible growth.
- Performed using broth dilution or automated systems.
Interpretation
- Results are interpreted based on Clinical and Laboratory Standards Institute (CLSI) guidelines.
- Susceptible: Large zone of inhibition or low MIC.
- Resistant: Small or no zone of inhibition or high MIC.
Applications
- Methicillin-Resistant Staphylococcus aureus (MRSA) Detection:
- Cefoxitin is a surrogate marker for detecting mecA-mediated resistance.
- Antibiotic Stewardship:
- Helps in selecting effective antibiotics, preventing misuse.
Cefoxitin susceptibility testing is crucial for identifying antibiotic resistance, ensuring effective treatment, and combating the spread of resistant bacterial strains.
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