A novel method for determination of beta-lactamase using the agar dilution method

Area of Science:

• Microbiology
• Biochemistry
• Analytical Chemistry

Background:

• Beta-lactamase enzymes are crucial mediators of bacterial resistance to beta-lactam antibiotics.
• Accurate and rapid detection of beta-lactamase activity is essential for guiding antimicrobial therapy.
• Current methods for beta-lactamase detection can be time-consuming or lack quantitative precision.

Purpose of the Study:

• To introduce a novel, rapid agar dilution test procedure for quantifying beta-lactamase susceptibility.
• To establish a method for expressing beta-lactamase susceptibility comparable to antibiotic Minimum Inhibitory Concentration (MIC) assays.
• To evaluate the correlation between the novel assay results and established bacterial resistance patterns.

Main Methods:

• A modified agar dilution method was developed incorporating a specific amount of beta-lactamase enzyme into the culture broth.
• Test organisms were cultured using the agar dilution technique with the enzyme added.
• Beta-lactamase susceptibility was measured and expressed in quantitative terms (micrograms/ml).

Main Results:

• The novel agar dilution procedure provided a rapid assay for beta-lactamase activity.
• Beta-lactamase susceptibility values obtained were directly comparable to antibiotic MIC values.
• Results using Escherichia coli beta-lactamase demonstrated a strong correlation with the MIC patterns of beta-lactamase-producing strains.

Conclusions:

• The described agar dilution method offers a rapid and quantitative approach to assess beta-lactamase susceptibility.
• This method facilitates a standardized expression of enzyme activity, analogous to antibiotic susceptibility testing.
• The assay shows promise for clinical microbiology laboratories to quickly determine bacterial resistance mechanisms.