[Clinical laboratory approach for estimating effective administrative dose of cefsulodin]

Reliability of cefsulodin (CFS) disc sensitivity test for estimating approximate values of MICs and its utilization for evaluation of proper administrative dose were studied against 106 strains of Pseudomonas aeruginosa and Staphylococcus aureus isolated from clinical materials using 2 different kind of discs. The disc results were compared with MICs determined using agar dilution method at inoculum level of 10(6) CFU/ml. The results of CFS disc susceptibility test with 8 mm diameter disc (Showa) and 6 mm diameter disc (Wako), both of them contained 30 micrograms, were well correlated with MICs. It is capable to use disc results for estimation of approximate value of MICs. For interpretation of CFS disc tests, three category system has been used in USA and Europe, but four category system in Japan. MIC break points proposed for classifying bacteria into three categories of susceptibility: resistant (R) MIC greater than 32 micrograms/ml, moderately susceptible (MS) MIC 16 approximately 32 micrograms/ml, and susceptible (S) MIC less than or equal to 8 micrograms/ml. Those in four category system were as follows: MIC less than or equal to 3 micrograms/ml, 3 micrograms/ml less than MIC less than or equal to 15 micrograms/ml, (+) 15 micrograms/ml MIC less than or equal to 60 micrograms/ml, (-) MIC greater than 60 micrograms/ml. Based on CFS pharmacokinetic data and the recommended dosage schedule (less than 2 g a day), MIC break points less than 3 micrograms/ml and less than 15 micrograms/ml, appear to be more useful than that of less than or equal to 8 micrograms/ml and less than 32 micrograms/ml for evaluating a proper administrative dose level.(ABSTRACT TRUNCATED AT 250 WORDS)