SPECTRUM OF ACTIVITY OF LEVOFLOXACIN AGAINST NONTUBERCULOUS MYCOBACTERIA AND ITS ACTIVITY AGAINST THE MYCOBACTERIUM-AVIUM COMPLEX IN COMBINATION WITH ETHAMBUTOL, RIFAMPIN, ROXITHROMYCIN, AMIKACIN, AND CLOFAZIMINE

The spectrum of activity of levofloxacin was initially determined agai nst 29 strains belonging to 16 species of atypical mycobacteria by mea suring radiometric MICs, Levofloxacin MICs were 1 to 2 dilutions lower compared with those obtained for ofloxacin and 8 to 64 dilutions lowe r compared with those obtained for its D-isomer, Levofloxacin MICs wer e below its peak level in serum (5.5 mu g/ml following administration of a single oral dose of 350 mg) for 25 of 29 isolates tested, It poss essed MICs below its peak level in serum for M, scrofulaceum, M. szulg ai, M. malmoense, M. xenopi, M. marinum, M. kansasii, M. chelonei, M. abcessus, M. fortuitum, and M. peregrinum. Regarding the M. avium comp lex, the MICs of levofloxacin for 11 clinical isolates (7 from human i mmunodeficiency virus-positive patients and 4 from human immunodeficie ncy virus-negative patients) were 1 to 2 dilutions lower than those of ofloxacin. Among 20 isolates belonging to 12 pathogenic mycobacterial species, the MBC/MIC ratios varied from 1 to 4 for levofloxacin and 2 to 4 for ofloxacin, When drug combinations were screened by using the radiometric x/y quotient methodology against five M, avium complex is olates, levofloxacin activity against all five isolates was enhanced b y ethambutol and activity against three isolates was enhanced by clofa zimine, Screening of three-drug combinations showed that the combinati on levofloxacin-ethambutol with a third potential anti-M. avium drug ( rifampin, roxithromycin, amikacin, or clofazimine) resulted in enhance d activity for all 20 drug combinations screened.