Page 181 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Evaluation of antimicrobial combination

1- Checkerboard

• the assay is performed in in a 96-well microplate

• two antimicrobics are tested in tow-fold serial dilutions (including 1/16 MIC -

2X MIC)

• The concentration of each drug is tested both alone and in combination

• The resulting checkerboard yields every combination of the two antibiotics, from

a tube that contains no antibiotic at one corner to a tube that contains the highest

concentration of each at the opposite corner

• The minimal inhibitory concentration (MIC) of each antibiotic alone or in

combination was determined as the lowest concentrations showing no turbidity

after incubation for 24 and 48 hr at 37ºC.

• Interpretation of results:

➢ Fractional inhibitory concentration (FIC) index

➢ plot Isobologram.

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