title: Evolution of the Sterol Biosynthetic Pathway of Pythium insidiosum and Related Oomycetes Contributes to Antifungal Drug Resistance.
abstract: Pythiosis is a life-threatening infectious disease caused by the oomycetePythium insidiosumDirect exposure toPy. insidiosumzoospores can initiate infections of the eye, limb, gastrointestinal tract, or skin/subcutaneous tissue. Treatments for pythiosis have mostly relied on surgery. Antifungal drugs are generally ineffective againstPy. insidiosumHowever, one patient with an invasivePy. insidiosuminfection recovered completely following treatment with terbinafine and itraconazole. Additionally, the drug target sterol biosynthetic enzymes have been identified in the oomyceteAphanomyces euteichesIt remains an open question whetherPy. insidiosumis susceptible to the antifungal drugs and harbors any of the known drug target enzymes. Here, we determined thein vitrosusceptibilities of terbinafine and itraconazole against 30 isolates ofPy. insidiosumWe also analyzed endogenous sterols and searched for genes encoding the sterol biosynthetic enzymes in the genomes ofPy. insidiosumand related oomycetes. The susceptibility assay showed that the growth of each of thePy. insidiosumisolates was inhibited by the antifungal agents, but only at difficult-to-achieve concentrations, which explains the clinical resistance of the drugs in the treatment of pythiosis patients. Genome searches ofPy. insidiosumand related oomycetes demonstrated that these organisms contained an incomplete set of sterol biosynthetic enzymes. Gas chromatographic mass spectrometry did not detect any sterol end products inPy. insidiosumIn conclusion,Py. insidiosumpossesses an incomplete sterol biosynthetic pathway. Resistance to antifungal drugs targeting enzymes in the ergosterol biosynthetic pathway inPy. insidiosumwas due to modifications or losses of some of the genes encoding the drug target enzymes.
authors.affiliation: Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.|Molecular Medicine Program, Multidisciplinary Unit, Faculty of Science, Mahidol University, Bangkok, Thailand.|Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Tassanee
authors.initials: T
authors.lastname: Lerksuthirat
authors.affiliation: Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Areeporn
authors.initials: A
authors.lastname: Sangcakul
authors.affiliation: Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Tassanee
authors.initials: T
authors.lastname: Lohnoo
authors.affiliation: Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Wanta
authors.initials: W
authors.lastname: Yingyong
authors.affiliation: Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Thidarat
authors.initials: T
authors.lastname: Rujirawat
authors.affiliation: Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand mr_en@hotmail.com.
authors.forename: Theerapong
authors.initials: T
authors.lastname: Krajaejun
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D025141:Drug Resistance, Fungal; D008401:Gas Chromatography-Mass Spectrometry; D017964:Itraconazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009281:Naphthalenes / Q000494:pharmacology; D010802:Phylogeny; D058968:Pythiosis / Q000382:microbiology; D011775:Pythium / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D013261:Sterols / Q000096:biosynthesis*; D000077291:Terbinafine
chemical_list: D000935:Antifungal Agents; D009281:Naphthalenes; D013261:Sterols; D017964:Itraconazole; D000077291:Terbinafine
keywords: Pythium insidiosum; antifungal drug; evolution; in vitro susceptibility; pythiosis; sterol biosynthetic enzyme