SUSCEPTIBILITY OF MYCOBACTERIUM-MALMOENSE TO ANTIBACTERIAL DRUGS AND DRUG-COMBINATIONS

Mycobacterium malmoense is an opportunistic pathogen with increasingly recognized clinical importance. It is mainly isolated in northern Eur ope and Great Britain, most often from patients with pulmonary infecti ons. Conventional therapy of M. malmoense infections with antitubercul osis drugs is often of limited value, and there is thus a need for imp roved drug regimens. The potential efficacies of new alternative drugs , such as quinolones, macrolides, amikacin, and rifabutin, are still u nknown, and so is the pathogen's in vitro susceptibility to most of th ese drugs. In this study, we used the BACTEC system for determining th e pattern of resistance of clinical M. malmoense isolates to a number of antibacterial drugs as well as their possible synergistic interacti ons when each of them was combined with ethambutol. The majority of th e strains were resistant or moderately resistant to the drug when it w as tested alone at selected concentrations. However, pronounced in vit ro synergism was demonstrated for combinations of ethambutol with cipr ofloxacin, amikacin, and rifampin, rendering most isolates susceptible to the combined drugs. Thus, for in vitro susceptibility testing of M . malmoense, examination of the possible synergistic effects of combin ed drugs also can be recommended.