Antimicrobial Susceptibility Test of an Isolate from a Clinical Specimen

Purpose To determine the antimicrobial susceptibility pattern of an organism isolated from a clinical
specimen (in Experiment 23.2)
Materials Nutrient agar plates (Mueller-Hinton if available)
Antimicrobial disks
Sterile swabs
Forceps
Blood agar plate with pure culture of isolate
Tube of nutrient broth (5.0 ml)
McFarland No. 0.5 turbidity standard

Procedures
  1. Using a sterile swab, take some of the growth of a pure culture you isolated from the clinical specimen in Experiment 23.2, and emulsify it in 5.0 ml of nutrient broth until the turbidity is equivalent to the McFarland 0.5 standard. Discard the swab.
  2. Take another sterile swab, dip it in the broth suspension, drain off excess fluid against the inner wall of the tube.
  3. Inoculate an agar plate as described in Experiment 15.1.
  4. Follow procedures 4 through 7 of Experiment 15.1.
  5. Incubate the agar plate at 35°C for 24 hours.
  6. Examine plates and record results for each antimicrobial disk as S (susceptible), I (intermediate), or R (resistant).
  7. Prepare a report for the “physician.”


Results
Record results:

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