COMPARISON OF WILKINS-CHALGREN MEDIUM SUPPLEMENTED WITH NICOTINAMIDE ADENINE-DINUCLEOTIDE AND HAEMOPHILUS TEST MEDIUM FOR SUSCEPTIBILITY TESTING OF CLINICAL HAEMOPHILUS ISOLATES

Haemophilus test medium (HTM) was compared with Wilkins-Chalgren agar (WCA; supplemented with 15 mu g/ml nicotinamide adenine dinucleotide ( NAD)) for antibiotic susceptibility testing of 74 clinical isolates of Haemophilus influenzae and Haemophilus parainfluenzae. The Bauer-Kirb y agar disk diffusion method and the agar dilution procedure were the two tests employed. WCA + NAD and HTM yielded comparable results for t he following antimicrobial drugs and drug combinations: ampicillin, am oxicillin plus clavulanic acid, ampicillin plus sulbactam, cefotaxime, cefuroxime, chloramphenicol, ciprofloxacin,and doxycycline. However, WCA + NAD slightly antagonized rifampin. Co-trimoxazole was significan tly antagonized by WCA + NAD. WCA + NAD was much simpler with regard t o in-house preparation, and WCA plates could be supplemented with NAD following pouring, solidification and storage of the plates simply by surface spreading the required amount of NAD with a glass spatula, thu s adding considerably to laboratory flexibility. It is suggested that additional laboratories comparatively and critically examine WCA + NAD medium for antibiotic susceptibility testing of clinical Haemophilus isolates.