ANTIBACTERIAL ACTIVITIES OF TOSUFLOXACIN AGAINST ANAEROBIC-BACTERIA AND THE ELECTRON MICROGRAPH OF ITS BACTERICIDAL EFFECTS

Tosufloxacin, a quinolone, showed a broad antibacterial spectrum again st gram-positive and gram-negative bacteria including anaerobic bacter ia. Tosufloxacin was 4- to 8-fold more active than levofloxacin and ci profloxacin. The MIC90 of tosufloxacin for clinical isolates of Bacter oides fragilis, Bacteroides vulgatus, Bacteroides thetaiotaomicron and Peptostreptococcus asaccharolyticus were 0.78, 0.39, 1.56 and 0.39 mu g/ml, respectively. Morphological observation with the scanning and t ransmission electron microscope revealed that exposure of B. fragilis ATCC 25285 to tosufloxacin resulted in the formation of filamentous ce lls with mesosome-like structures. Tosufloxacin also induced the mini- cell resulting from the unusual cell division system and a number of h oles in the outer membrane. Tosufloxacin at 4 MIC caused some change i n cell wall organization and cell lysis. After exposure of P. asacchar olyticus ATCC 14953 to tosufloxacin, the cells increased considerably in size and the cell wall and cross wall thickening was observed.