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Lab Manual for Moffitt-Long and Mount Zion

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Antimicrobial susceptibility testing

Item Value
Approval req'd? No, for aerobic bacteria. Contact Infectious Diseases Service or ID Pharmacy to obtain approval for susceptibilities on yeast and anaerobes
Available Stat? No
Test code
MIC by broth dilution B045
Disk Diffusion B046
MIC by Etest B047
Agar dilution B048
Performed by Microbiology
In House Availability Set up daily on day shift
Method Broth dilution, Disk Diffusion, Etest, or Agar diffusion
Container type
Sample type
Units µg/mL (mcg/mL) for MICs
Normal range
Synonyms Anaerobic sensitivity; Broth dilution susceptibility; Sensitivity testing; Drug susceptibility; Yeast susceptibility; Disk diffusion; E-test; MIC; Minimum inhibitory concentrasion; agar dilution
Turn around times 1-3 days
Additional information Susceptibity testing of bacterial isolates is performed and charged separately where appropriate for the specific culture request and isolate.

Susceptibility testing may be performed by various techniques, including broth dilution, disk diffusion, Etest, and agar dilution. The method is primarily dependent on the organism and specimen type.

Broth dilution is the method used for the majority of routine testing to provide minimum inhibitory concentration (MIC).

Disk diffusion is performed as a preliminary test on gram negative rods from blood cultures. Also performed routinely on:
1. Group B Streptococcus from OB patients if penicillin allergic
2. Streptococcus pneumoniae from respiratory sites
3. Mucoid strains of Pseudomonas aeruginosa, and Pseudomonas aeruginosa and Burkholderia cepacia from patients with cystic fibrosis
4. Haemophilus influenza and Neisseria gonorrhoeae upon request

Etest is performed on anaerobes, upon request, to provide MICs.

Agar dilution, using a concentration of 6 mcg/mL of vancomycin, is used for screening Enterococcus spp. from inpatients for vancomycin resistance.

Yeast susceptibility testing is only performed on Candida spp. Testing is performed by broth dilution and provides MICs. The antifungal agents tested include fluconazole, voriconazole, itraconazole, and 5-flucytosine.

For information on specific antibiotics reported on organisms, and range of concentration tested and interpretive criteria for broth dilution MICs Click here


CPT coding
Broth dilution 87186
Disk diffusion 87184
Etest and agar dilution 87181
LDT or Mod FDA? No
Last Updated 5/22/2013 11:47:26 AM
Entry Number 43

If you have additional questions regarding this test, please call: 415-353-1667

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