Inexpensive 4-hour micro-agar dilution susceptibility determination method

Area of Science:

• Microbiology
• Pharmacology
• Clinical Diagnostics

Background:

• Accurate antibiotic susceptibility testing is crucial for effective treatment.
• Traditional methods can be time-consuming and costly.
• A need exists for rapid, cost-effective antimicrobial susceptibility testing methods.

Purpose of the Study:

• To evaluate the accuracy and reproducibility of the micro-agar dilution (MAD) method.
• To compare the MAD method with traditional agar dilution techniques.
• To assess the cost-effectiveness of the MAD method for antibiotic susceptibility testing.

Main Methods:

• 18 antibiotics were tested against 29-32 microorganisms using the micro-agar dilution (MAD) method.
• MICs were read microscopically after 4-h incubation and macroscopically after 18-h incubation.
• Results were compared to traditional agar dilution as the gold standard.

Main Results:

• Microscopic MAD MICs showed 87.1% identical results and 97.9% within one dilution.
• Macroscopic MAD MICs showed 86.8% identical results and 98.4% within one dilution.
• Correlation with agar dilution was high (94.3% microscopic, 97.6% macroscopic).

Conclusions:

• The micro-agar dilution (MAD) method is a reproducible and accurate technique for antibiotic susceptibility testing.
• The method is rapid, inexpensive, and suitable for routine and research laboratories.
• High correlation with agar dilution supports its clinical utility.