Interpretive criteria for susceptibility tests with DU-6859a and FK-037 tested against Haemophilus influenzae and Neisseria gonorrhoeae

Abstract

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 ⩽1 μg/ml (5-μg disk zone diameter correlate, ⩾19 mm) or ⩽2 μg/ml (disk zone diameter correlate, ⩾16 mm) and for FK-037 susceptible at ⩽2 μg/ml (30-μg disk zone diameter correlate, ⩾19 mm). No other susceptibility categories were proposed. The gonococcal susceptibility testing criteria were for DU-6859a susceptible at ⩽0.12 μg/ml (disk zone diameter correlate, ⩾34 mm) and for FK-037 susceptible at ⩽0.5 μg/ml (disk zone diameter correlate, ⩾30 mm) and resistant at >1 μg/ml (disk zone diameter correlate, ⩽26 mm). No resistant criterion was proposed for N. gonorrhoeae tests with DU-6859a. No interpretive discrepancies were observed between methods using these proposed testing criteria.