Comparison of methods available for assay of chloramphenicol in clinical specimens

Eight methods for the assay of chloramphenicol in clinical samples were compared with our own modification of a plate diffusion technique using Sarcina lutea and yeast extract agar. Six of the eight methods were less sensitive than originally reported, and five of them were considered unsuitable for use in clinical microbiology practice. The remaining three methods together with the S. lutea/yeast extract modification were used to assay chloramphenicol in 20 samples of serum. Twenty samples of cerebrospinal fluid were also assayed by the S. lutea/yeast extract method. Our results indicate that only the Bacillus subtilis (sensitivity 6x0 mg/l) and the S. lutea (sensitivity 2x5 mg/l) diffusion methods are suitable for use with clinical samples in routine practice. The problems of chloramphenicol toxicity, appropriate dosage regimens, and the need for assay of the drugs are considered.