title: Characterizing clinical isolates of Acanthamoeba castellanii with high resistance to polyhexamethylene biguanide in Taiwan.
abstract: OBJECTIVE
  Acanthamoeba keratitis (AK), a painful infectious corneal disease, is caused by the free-living pathogenic species Acanthamoeba. The symptoms include corneal infiltrate, epithelial, and stromal destruction, and loss of vision. Current treatment generally involves an hourly application of polyhexamethylene biguanide (PHMB) over a period of several days; however, even this is not entirely effective against all strains/isolates. The aims of this study were to confirm the existence of pathogenic strains in Taiwan which are highly resistant to drugs and to characterize the behavior of these strains.
  
  
  METHODS
  An in vitro Acanthamoeba species culture platform was established to observe the effectiveness of treatment and chart the morphological changes that occur under the effects of drugs using a light microscope and time-lapse recording. Changes in gene expression were examined using reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR.
  
  
  RESULTS
  Over 90% of the standard strain cells (ATCC 30010) were lysed after being treated with PHMB for 1 hour; however, clinical isolates of Acanthamoeba castellanii that differed in their susceptibility to the treatment drug were only partly lysed. Following treatment with PHMB, National Cheng Kung University Hospital isolation B (NCKH_B) transformed into a pseudocyst under the effects of drug stress; however, National Cheng Kung University Hospital isolation D (NCKH_D), an isolate with higher tolerance for PHMB, did not transform.
  
  
  CONCLUSIONS
  Our results confirm the existence of clinical isolates of A. castellanii with high resistance to PHMB in Taiwan and present the alternative drug tolerance of A. castellanii in addition to the transformation of pseudocyst/cyst.
authors.affiliation: Department of Ophthalmology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Fu-Chin
authors.initials: FC
authors.lastname: Huang
authors.affiliation: Department of Ophthalmology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Min-Hsiu
authors.initials: MH
authors.lastname: Shih
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Kai-Fei
authors.initials: KF
authors.lastname: Chang
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Jian-Ming
authors.initials: JM
authors.lastname: Huang
authors.affiliation: Department of Parasitology, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Jyh-Wei
authors.initials: JW
authors.lastname: Shin
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Department of Parasitology, National Cheng Kung University, Tainan, Taiwan. Electronic address: wcnikelin@mail.ncku.edu.tw.
authors.forename: Wei-Chen
authors.initials: WC
authors.lastname: Lin
mesh_terms: D048248:Acanthamoeba castellanii / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D000562:Amebiasis / Q000469:parasitology; D001645:Biguanides / Q000494:pharmacology*; D003315:Cornea / Q000469:parasitology / Q000473:pathology; D004351:Drug Resistance; D004361:Drug Tolerance; D015870:Gene Expression; D006801:Humans; D008853:Microscopy; D021261:Parasitic Sensitivity Tests; D016053:RNA, Protozoan / Q000302:isolation & purification; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013624:Taiwan; D013997:Time Factors
chemical_list: D001645:Biguanides; D016053:RNA, Protozoan; D012337:RNA, Ribosomal, 18S; C031233:polihexanide
keywords: Acanthamoeba keratitis; drug tolerance; polyhexamethylene biguanide