title: In vitro activity of pyrvinium pamoate against Entamoeba histolytica and Giardia intestinalis using radiolabelled thymidine incorporation and an SYBR Green I-based fluorescence assay.
abstract: OBJECTIVE
  To assess the in vitro activity of the FDA-approved antihelminthic drug pyrvinium pamoate against Entamoeba histolytica and Giardia intestinalis.
  
  
  METHODS
  A head-to-head comparison of a standard radiolabelled thymidine incorporation assay and the SYBR Green I-based fluorescence assay for determination of in vitro inhibition by pyrvinium and metronidazole was performed.
  
  
  RESULTS
  The 50% inhibitory concentration (IC(50)) for treatment of E. histolytica with pyrvinium was 4-5 microM for both assays compared with 1-2 microM for metronidazole. For pyrvinium treatment of G. intestinalis, an IC(50) of approximately 12 microM was determined by the radiolabelled thymidine assay alone, with maximum inhibition around 60%. In contrast, the IC(50) for metronidazole treatment using this assay was approximately 2 microM.
  
  
  CONCLUSIONS
  Pyrvinium is a potential gut lumen agent for treatment of intestinal amoebiasis, but possibly not for giardiasis. SYBR Green I is an alternative screening method for E. histolytica, but not G. intestinalis.
authors.affiliation: Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
authors.forename: Autumn S
authors.initials: AS
authors.lastname: Downey
authors.forename: Thaddeus K
authors.initials: TK
authors.lastname: Graczyk
authors.forename: David J
authors.initials: DJ
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D052160:Benzothiazoles; D004247:DNA / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects*; D003959:Diamines; D004748:Entamoeba histolytica / Q000187:drug effects*; D016829:Giardia lamblia / Q000187:drug effects*; D020128:Inhibitory Concentration 50; D009930:Organic Chemicals / Q000378:metabolism*; D021261:Parasitic Sensitivity Tests / Q000379:methods; D011774:Pyrvinium Compounds / Q000494:pharmacology*; D011804:Quinolines; D013936:Thymidine / Q000378:metabolism*
chemical_list: D000981:Antiprotozoal Agents; D052160:Benzothiazoles; D003959:Diamines; D009930:Organic Chemicals; D011774:Pyrvinium Compounds; D011804:Quinolines; C098022:SYBR Green I; C024631:pyrvinium; D004247:DNA; D013936:Thymidine
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