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Antibiotic susceptibility and resistance testing: an overview
1Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada. smaill@mcmaster.ca
Summary
Antibiotic susceptibility testing predicts treatment success by measuring the minimum inhibitory concentration (MIC) of bacteria. Standardized laboratory methods ensure reliable MIC results for guiding antibiotic selection.
Area of Science:
- Microbiology
- Clinical Laboratory Science
Background:
- In vitro antibiotic susceptibility testing is crucial for predicting clinical treatment response.
- Minimum inhibitory concentration (MIC) determines bacterial susceptibility to antibiotics.
- Breakpoint MIC values classify bacteria as sensitive, intermediate, or resistant, guiding therapy.
Purpose of the Study:
- To explain the significance of in vitro antibiotic susceptibility testing.
- To describe methods for determining MIC values.
- To highlight factors influencing MIC results and the importance of standardization.
Main Methods:
- Broth dilution, agar dilution, and gradient diffusion (E test) measure MIC by serial antibiotic dilutions.
- Disk diffusion assesses susceptibility based on growth inhibition zones around antibiotic disks.
- Standardized protocols from the National Committee for Clinical Laboratory Standards ensure reproducibility.
Main Results:
- MIC values correlate with clinical outcomes, aiding antibiotic selection.
- Different methods (broth dilution, agar dilution, E test, disk diffusion) provide varying ways to assess bacterial susceptibility.
- Laboratory factors significantly influence MIC outcomes, necessitating adherence to standards.
Conclusions:
- In vitro antibiotic susceptibility testing is a vital tool for guiding effective antibiotic therapy.
- Accurate MIC determination relies on standardized laboratory procedures.
- Consistent application of established methods ensures reliable and reproducible susceptibility testing results.