A Reliable Two-Hour Staphylococcus Plate Assay of Rifampicin, Erythromycin, Lincomycin, Chloramphenicol and Amikacin in Human Sera

Summary

A simple and precise agar diffusion microassay was developed for rifampicin (RIF) in serum. The method involved the addition of sera containing RIF (0.125-4.0 μg/ml) to wells cut in an agar medium (pH 6.6) surface seeded with an adjusted inoculum of Staphylococcus aureus ATCC 6538 P and incubated for 2h at 40° C. Repetitive assays of sera containing known concentrations of RIF revealed an average mean recovery of 93.6% with a coefficient of variation of 5.7%. This rapid method allowed accurate determination of RIF in the presence of erythromycin, chloramphenicol, lincomycin and amikacin. These four antibiotics were also separately measured in sera by the rapid assay at different pH values.

Key Words:

• Rapid bio-assay
• antibiotics in sera
• rifampicin
• erythromycin
• amikacin
• chloramphenicol
• lincomycin.