COMPARATIVE IN-VITRO ASSESSMENT OF SPARFLOXACIN ACTIVITY AND SPECTRUMUSING RESULTS FROM OVER 14,000 PATHOGENS ISOLATED AT 190 MEDICAL-CENTERS IN THE USA

Sparfloxacin, a new orally administered fluoroquinolone, was tested ag ainst 14,182 clinical strains isolated (generally blood stream and res piratory tract cultures) at nearly 200 hospitals in the United States (USA) and Canada. Sparfloxacin activity was compared with 13 other com pounds by Etest (AB BIODISK, Solna, Sweden), broth microdilution, or a standardized disk diffusion method. Using the Fodd and Drug Administr ation/product package insert MIC breakpoint for sparfloxacin susceptib ility (less than or equal to 0.5 mu g/ml), 94% of Streptococcus pneumo niae (2666 isolates) and 89% of the other streptococci (554 isolates) were susceptible. However, at less than or equal to 1 mu g/ml (the bre akpoint for all nonstreptococcal species) sparfloxacin susceptibility rates increased to 100% and 98%, respectively, for the two groups of s treptococci. Only 50% and 65% of pneumococci were susceptible to cipro floxacin (MIC90, 3 mu g/ml) and penicillin (MIC90, 1.5 mu g/ml), respe ctively. Although there were significant differences between regions i n the USA in the frequency of penicillin-resistant pneumococcal strain s, results indicate that the overall sparfloxacin MIC90 was uniformly at 0.5 mu g/ml. Nearly all (greater than or equal to 99%) Haemophilus species and Moraxella catarrhalis, including those harboring beta-lact amases, were susceptible to sparfloxacin, ciprofloxacin, and amoxicill in/clavulanic acid. Only cefprozil and macrolides demonstrated lower p otency and spectrum against these two species. Sparfloxacin was active against oxacillin-susceptible Staphylococcus aureus (96 to 97%), Kleb siella spp. (95%), and other tested enteric bacilli (93%). Comparison between broth microdilution MIC and disk diffusion interpretive result s for M. catarrhalis, Staphylococcus aureus, and the Enterobacteriacea e showed an absolute intermethod categorical agreement of >95% using c urrent sparfloxacin breakpoints, in contrast to those of cefpodoxime f or S. aureus where a conspicuous discord (98% versus 59%) between meth ods was discovered. These results demonstrate that sparfloxacin posses ses sufficient in vitro activity and spectrum versus pathogens that ca use respiratory tract infections (indications), especially strains res istant to other drug classes such as the earlier fluoroquinolones, ora l cephalosporins, macrolides, and amoxicillin/clavulanic acid. The spa rfloxacin susceptibility breakpoint for streptococci may require modif ication (less than or equal to 1 mu g/ml) based on the MIC population analysis presented here. A modal MIC (0.38 to 0.5 mu g/ml) was observe d at the current breakpoint. Regardless, sparfloxacin inhibited 89% (n onpneumococcal Streptococcus spp.) to 1005 (Haemophilus spp., M. catar rhalis) of the isolates tested with a median activity of 97% against i ndicated species. (C) 1997 Elsevier Science Inc.