Antibacterial Assays in Body Fluids
Antibacterial assays are carried out to demonstrate the toxic and
therapeutic level of the antibiotics in blood and other body fluids. In this
method, the MIC of the antibiotic for the test organism is done first by
standard broth dilution method. The test with patient’s serum is done
concurrently. Serial dilutions of the patients’ serum in nutrient broth are
carried out and to each a standard drop of culture is added and incubated for
18 hours. The highest dilution of serum which has inhibited growth of the assay
organism is noted. This is equivalent to the MIC of the antibiotic in question.
Multiplication of the MIC by the serum dilution gives the concentration of the
antibiotic which was present in the patient’s undiluted serum.