[A study of the disc sensitivity test for cephapirin]

Area of Science:

• Microbiology
• Antimicrobial Susceptibility Testing

Background:

• Accurate determination of bacterial susceptibility to antibiotics is crucial for effective treatment.
• Cephapirin (CEPR) is a cephalosporin antibiotic used in clinical settings.
• Standard methods for susceptibility testing include agar dilution and disc diffusion.

Purpose of the Study:

• To evaluate the correlation between Minimum Inhibitory Concentration (MIC) determined by agar dilution and inhibition zone diameter from the single-disc method for cephapirin (CEPR).
• To assess the applicability of the single-disc assay for CEPR across different incubation times, including rapid assays.

Main Methods:

• Tested 203 bacterial strains from 34 species/subspecies against cephapirin (CEPR).
• Determined MIC using the 2-fold agar dilution method.
• Measured inhibition zone diameter using the single-disc method with varying incubation periods (conventional, delayed, and rapid assays).

Main Results:

• A significant correlation was observed between MIC values and inhibition zone diameters for CEPR.
• The single-disc assay demonstrated applicability across conventional (16h), delayed (24h), and rapid (3-6h) incubation times.
• Regression equations were established to relate zone diameter to MIC for different assay conditions, including for beta-lactamase producing Staphylococci.

Conclusions:

• The single-disc assay is a reliable method for determining bacterial susceptibility to cephapirin (CEPR).
• The established regression equations allow for accurate interpretation of disc diffusion results for CEPR.
• Rapid disc diffusion assays can be effectively utilized for CEPR susceptibility testing.