Susceptibility of Thai Pythium insidiosum Isolates to Antibacterial Agents.

Human pythiosis is a life-threatening human disease caused by In Thailand, vascular pythiosis is the most common form and carries a mortality rate of 10 to 40%, despite aggressive treatment with radical surgery, antifungal agents, and immunotherapy. Itraconazole and terbinafine have been the mainstay of treatment, until recently, based on case report data showing potential synergistic effects against Brazilian isolates. However, the synergistic effects of itraconazole and terbinafine against Thai isolates were not observed. This study tested the susceptibilities of 27 Thai human isolates (clade II,  = 17; clade IV,  = 10), 12 Thai environmental isolates (clade II,  = 4; clade IV,  = 8), and 11 non-Thai animal isolates (clade I,  = 9; clade II,  = 2) to antibiotics in eight antibacterial classes to evaluate alternative effective treatments. Tetracycline and macrolide antibiotics demonstrated activity against Thai isolates, with doxycycline MICs (1 to 16 μg/ml), minocycline MICs (1 to 4 μg/ml), tigecycline MICs (1 to 4 μg/ml), azithromycin MICs (1 to 16 μg/ml), and clarithromycin MICs (0.125 to 8 μg/ml) being the lowest, on average. Synergistic effects of tetracyclines and macrolides were also observed.