Comparative evaluation of the in vitro antimycobacterial activities of six aminoglycoside antibiotics using an agar dilution method.

Given the increasing prevalence of mycobacterial resistance to aminoglycoside antibiotics, we examined the susceptibility of 76 clinical isolates of mycobacteria to arbekacin, amikacin, gentamicin, kanamycin, tobramycin and streptomycin using an agar dilution method. Only arbekacin and amikacin showed excellent therapeutic potential (minimum inhibitory concentrationis (MICs) < or =0.25-4 microg/ml) against 30 isolates of rapidly growing mycobacteria, including Mycobacterium fortuitum, M. chelonae and a related organism, Nocardia asteroides. The MIC(90)of tobramycin against 23 isolates of M. avium complex was 8 microg/ml, while that of the other 5 aminoglycosides ranged from 64-256 microg/ml. Of the 23 M. tuberculosis isolates tested, 5 showed aminoglycoside resistance (MICs 128 to > or =1,024 microg/ml), while the others were variably susceptible (MICs < or =0.25-32 microg/ml) to all 6 aminoglycosides. The chemotherapeutic potential of arbekacin, amikacin and streptomycin as treatment of tuberculosis was apparent; however, proper patient management would be required to control against the emergence of the drug-resistant strains during prolonged treatment.