In vitro activity of gemifloxacin (SB-265805) compared to eleven other antimicrobial agents against streptococcal isolates, excluding Streptococcus pneumoniae

The purpose of the study presented here was to determine the in vitro activ ity of gemifloxacin compared with that of 11 other antimicrobial agents (5 of them quinolones) against 400 isolates of P-haemolytic and viridans group streptococci. The minimum inhibitory concentration values for gemifloxacin against 90% of the streptococci tested were as follows: Lancefield groups A, C and G, 0.06 mug/ml; Lancefield group B, Streptococcus mitis, Streptoco ccus mutans and Streptococcus bovis, 0.125 mug/ml; and Streptococcus miller i, 0.03 mug/ml. Resistance to penicillin, ampicillin and erythromycin was f ound mainly in the Streptococcus mitis isolates; tetracycline showed variab le results, and no vancomycin resistance was encountered. Higher rates of c iprofloxacin resistance were identified in the Streptococcus bovis, mitis a nd mutans isolates. In conclusion, gemifloxacin was the most active quinolo ne tested followed by trovafloxacin, sparfloxacin, grepafloxacin, ciproflox acin and levofloxacin, especially against isolates resistant to beta -lacta m agents, macrolides and tetracycline.