Preliminary susceptibility testing interpretive criteria were determined for two investigational drugs, DU-6859a and FK-037, when tested against Haemophilus influenzae and Neisseria gonorrhoeae strains. National Committee for Clinical Laboratory Standards (NCCLS) methods with the Haemophilus Test Medium and GC agar base were utilized, and the study design conformed to the NCCLS M23-A guidelines. The proposed H. influenzae susceptibility testing criteria were for DU-6859a susceptible at less than or equal to 1 mu g/ml (5-mu g disk zone diameter correlate, greater than or equal to 19 mm) or less than or equal to 2 mu g/ml (disk zone diameter correlate, greater than or equal to 16 mm) and for FK-037 susceptible al less than or equal to 2 mu g/ml (30-mu g disk zone diameter correlate, greater than or equal to 19 mm). No other susceptibility categories were proposed. The gonococcal susceptibility testing criteria were for DU-6859a susceptible at less than or equal to 0.12 mu g/ml (disk zone diameter correlate, greater than or equal to 34 mm) and for FK-037 susceptible at less than or equal to 0.5 mu g/ml (disk zone diameter correlate, greater than or equal to 30 mm) and resistant at >1 mu g/ml (disk zone diameter correlate, less than or equal to 26 mm). No resistant criterion was proposed for N. gonorrhoeae tests with DU-6859a. No interpretive dis crepancies were observed between methods using these proposed testing criteria.
