TENTATIVE CRITERIA FOR CONFIRMING THE IN-VITRO SUSCEPTIBILITIES OF HAEMOPHILUS-INFLUENZAE AND NEISSERIA-GONORRHOEAE TO 2 FLUOROQUINOLONES (SPARFLOXACIN AND LEVOFLOXACIN), INCLUDING QUALITY-CONTROL PARAMETERS

Sparfloxacin and levofloxacin were evaluated against 150 Haemophilus i nfluenzae isolates and 149 Neisseria gonorrhoeae isolates in order to define susceptibility testing parameters. Sparfloxacin-susceptible H. influenzae strains were defined as those for which the MICs were less- than-or-equal-to 0.25 mug/ml and the zones were greater-than-or-equal- to 30 mm, and N. gonorrhoeae susceptible strains were those for which the MICs were less-than-or-equal-to 0.03 mug/ml and the zones were gre ater-than-or-equal-to 39 mm (5-mug disks). Levofloxacin-susceptible st rains of H. influenzae included those for which the MICs were less-tha n-or-equal-to 0.12 mug/ml and the zones were greater-than-or-equal-to 32 mm and N. gonorrhoeae susceptible strains were those for which the MICs were less-than-or-equal-to 0.12 mug/ml and the zones were greater -than-or-equal-to 37 mm (5-mug disks). Criteria for a resistant catego ry cannot yet be defined for either quinolone. In multilaboratory stud ies with different lots of Haemophilus Test Medium, replicate tests wi th the standard control strain of H. influenzae (ATCC 49247) were eval uated. For sparfloxacin disk tests, the proposed zone size limits were 33 to 42 mm and broth microdilution MIC limits were 0.004 to 0.016 mu g/ml, whereas for levofloxacin tests, zone size limits were 32 to 41 m m and broth microdilution MIC limits were 0.008 to 0.03 mug/ml. Other multilaboratory studies evaluated tests with supplemented GC agar and N. gonorrhoeae ATCC 49226; for both drugs, zone size limits were 44 to 52 mm and agar dilution MIC limits were 0.004 to 0.016 mug/ml.