Susceptibility testing of Malassezia pachydermatis using the urea broth microdilution method

The in vitro susceptibility of 24 isolates of Malassezia pachydermatis to four antifungal drugs in combination with lysozyme was determined using a urea broth microdilution method. The antifungal activities of each drug alone against 24 isolates of M. pachydermatis were determined as the mean minimal inhibitory concentrations (MICs). MICs of bifonazole, itraconazole, amorolfine and terbinafine were 3.2 microg ml(-1), 1.6 microg ml(-1), 25 microg ml(-1) and 3.2 microg ml(-1), respectively. Lysozyme alone inhibited the growth of M. pachydermatis in a dose-dependent manner, although the lysozyme was unable to kill the cells of M. pachydermatis at the highest concentration of 20 microg ml(-1). Furthermore, the mean MICs of bifonazole, itraconazole, amorolfine and terbinafine in combination with lysozyme were the same as the results for each drug alone. Although the activity of antifungal drugs in combination with lysozyme is enhanced for other fungi. These results suggested that M. pachydermatis might not be affected by the host's natural defences.