SCREENING FOR CEPHALOSPORIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE WITH THE KIRBY-BAUER DISK SUSCEPTIBILITY TEST

Kirby-Bauer disk susceptibility tests with five standard cephalosporin disks were performed on 23 penicillin-resistant Streptococcus pneumoniae isolates for which ceftriaxone MICs were 0.125 to 4 mug/ml. Cefuroxime disk inhibition zone diameters distinguished clearly isolates for which ceftriaxone MICs were greater-than-or-equal-to 2 mug/ml from more susceptible strains, whereas cephalothin, ceftizoxime, cefotaxime, and ceftriaxone disks distinguished these isolates less clearly than the cefuroxime disk did.