Liofilchem® Daptomycin DAP, Antimicrobial Susceptibility Discs, 30 µg

The Liofilchem® Daptomycin (DAP) Antimicrobial Susceptibility Discs, 30 µg, are designed for the Kirby-Bauer disk diffusion method to assess the susceptibility of bacteria to daptomycin. This method aids in determining the appropriate antimicrobial therapy for bacterial infections.

Test Procedure:

1. Preparation of Inoculum:
   • Select well-isolated colonies from an 18-24 hour culture.
   • Suspend the colonies in sterile saline to achieve a turbidity equivalent to a 0.5 McFarland standard.
2. Inoculation of Agar Plate:
   • Dip a sterile swab into the standardized inoculum suspension.
   • Remove excess liquid by pressing the swab against the tube wall.
   • Evenly streak the swab over the entire surface of a Mueller-Hinton agar plate to ensure a uniform lawn of growth.
3. Application of Daptomycin Discs:
   • Allow the inoculated plate to dry for 3-5 minutes at room temperature.
   • Using sterile forceps, place the 30 µg daptomycin disc onto the agar surface, ensuring even contact.
   • Space multiple discs adequately to prevent overlapping zones of inhibition.
4. Incubation:
   • Invert the plate and incubate at 35 ± 2°C for 16-20 hours in ambient air.
5. Interpretation:
   • After incubation, measure the diameter of the zone of inhibition around each disc to the nearest millimeter.
   • Interpret the results using the latest EUCAST or CLSI guidelines for daptomycin.

Quality Control (QC):

To ensure test accuracy, perform QC using standard reference strains with known susceptibility profiles. The following QC strain is recommended:

Regular QC testing verifies the reliability of the test conditions and the performance of the daptomycin discs. If QC results fall outside the expected range, investigate potential issues with materials, procedures, or environmental conditions.

Storage and Handling:

• Store discs at 2–8°C in their original packaging with a desiccant.
• Allow discs to reach room temperature before opening to prevent condensation.
• Avoid exposure to moisture and direct sunlight.

Comparison Summary:

References:

• Liofilchem® Antibiotic Disc Instructions for Use: https://www.liofilchem.com/images/prodotti-evidenza/antibiotic-disc/F01511-18_AntibioticDisc.pdf
• EUCAST Disk Diffusion Methodology: https://www.eucast.org/ast_of_bacteria/disk_diffusion_methodology/
• CLSI Performance Standards for Antimicrobial Susceptibility Testing.

For detailed procedures and interpretative criteria, always refer to the manufacturer's instructions and the latest EUCAST and CLSI guidelines.