Antibiotic Susceptibility Testing (AST)
Organisms' sensitivity to drugs are measured in diameter of their colonies in the presence of the drug
AST, Antibiotic Susceptibility Testing
A la Wikipedia, Antibiotic Sensitivity as the susceptibility of bacteria to antibiotics
Antibiotic susceptibility testing, AST, is carried out to determine which antibiotic will be most successful in treating a bacterial infection. Minimum Inhibitory Concentration (MIC) is at its heart
Small wafers containing antibiotics are placed onto a plate upon which bacteria are growing. If the bacteria are sensitive to the antibiotic, a clear ring, or zone of inhibition, is seen around the wafer indicating poor growth.
Clinically, minimum inhibitory concentrations are used to determine the amount of antibiotic that a patient will receive and also the type of antibiotic used
Also see https://senaiteast.readthedocs.io/en/latest/index.html
Qualitative Outcomes
The plates are incubated for say 24 hours and the results are determined by the diameter of the growth inhibition around each antibiotic disk and reported in accordance with e.g. EUCAST's definitions
Recommended thresholds, breakpoints, for the diameter of the ring sizes per susceptibility category, are available for most known bacterium and antibiotics combinations. These are the concentrations at which bacteria are susceptible to successful treatment
The numeric diameter readings are interpreted using the breakpoint tables and reported as:
S - Susceptible, standard dosing regimen, when there is a high likelihood of therapeutic success using a standard dosing regimen of the agent.
I: Susceptible, increased exposure, exposure to the agent is increased by adjusting the dosing regimen
R: Resistant, not effective at inhibiting the growth of the organism
An example, P aeruginosa has breakpoints for the antibiotic Cefepime of S ≥ 50 mm and R < 13 mm
This configuration is broken down as:
Microorganisms
Configure the Microorganisms in their categories, then select them from there for identification tests, and use in AST panels
Antibiotics
Set up the Antibiotics you are going to use
Breakpoint Tables
Set-up the breakpoint tables for the organism-antibiotics combinations for looking up the growth diameters for interpretation