Table 1 Description of cultured based antibiotic resistance assessment
Method | Growth media | Description | Resistance indicator |
|---|---|---|---|
Serial dilution and broth microdilution | Broth or Agar | Antimicrobial agent is serially diluted and added to either broth or agar. Bacteria are then subsequently grown in the media. | Presence of growth indicates resistance. |
Disk diffusion | Agar | Bacteria are streaked evenly across plate, paper disks containing antibiotic at known concentrations are added. | Presence of growth around disk indicates resistance. If susceptible a zone of inhibition will be present around disk. |
Strip diffusion (gradient method) | Agar | Bacteria are streaked evenly across a plate, and a strip containing an antibiotic gradient concentration is added. The top of the strip been at a much higher concertation to that of the bottom (or vice versa) | The strip has markers indicating the different antibiotic concentrations. The marker at which a zone of inhibition begins is the highest resistance the bacteria can grow up to. |
