Susceptibility Testing Methods

1
Susceptibility Testing Methods
Incubate plate 18-24 hr, 35 C Measure and record
zone of inhibition around each disk
Innoculate MH plate
Place disks on agar plate
2
Disk Diffusion Susceptibility Testing
Mueller Hinton agar good disk placement
Improper agar disk placement
Use Mueller Hinton agar
3
Antimicrobial susceptibilitytesting using
micro-broth dilutions
ug/ml 64 32 16 8 4 2
96 well microtiter plate
4
Antimicrobial Gradient TestingE-test
Read plates after recommended Incubation
Read MIC where elipse intersects scale
5
Focus on Gram Positives (MIC)
Susceptibility Testing

• 10 random samples that cultured coagulase
  negative Staph spp. (CN Staph) and 10 random
  samples that cultured environmental Strep spp.
• Based upon the results, the MIC50, MIC75 and
  MIC90 for each group of organisms were calculated
  (antibiotic susceptibility levels for 50, 75
  and 90 of each group)