INTERPRETIVE CRITERIA, QUALITY-CONTROL GUIDELINES, AND DRUG STABILITY STUDIES FOR SUSCEPTIBILITY TESTING OF CEFOTAXIME, CEFOXITIN, CEFTAZIDIME, AND CEFUROXIME AGAINST NEISSERIA-GONORRHOEAE

Cefotaxime, cefoxitin, ceftazidime, and cefuroxime were tested in a multicenter study to establish susceptibility testing criteria and quality control guidelines for Neisseria gonorrhoeae. Interpretive criteria were established by using triplicate testing of at least 100 gonococcal strains having various susceptibility patterns to currently utilized drug regimens. Only a susceptible category was proposed for cefotaxime and ceftazidime (greater-than-or-equal-to-31 mm and less-than-or-equal-to-0.5-mu-g/ml) because of rare resistant isolates. The other interpretive criteria were cefoxitin-susceptible, greater-than-or-equal-to-28 mm (less-than-or-equal-to-2-mu-g/ml); intermediate, 24-27 mm (4-mu-g/ml), and resistant, less-than-or-equal-to-23 mm (greater-than-or-equal-to-8-mu-g/ml); cefuroxime-susceptible, greater-than-or-equal-to-31 mm (less-than-or-equal-to-1-mu-g/ml); moderately susceptible, 26-30 mm (2-mu-g/ml); and resistant, less-than-or-equal-to-25 mm (greater-than-or-equal-to-4-mu-g/ml). Quality control criteria were established by using multiple agar lots, three disk lots, and a number of replicates consistent with National Committee for Clinical Laboratory Standards M23-T guidelines.