OxyFile #191

UI  - 92143592
AU  - Labatiuk CW
AU  - Schaefer FW 3d
AU  - Finch GR
AU  - Belosevic M
TI  - Comparison of animal infectivity, excystation, and fluorogenic
      dye as measures of Giardia muris cyst inactivation by ozone.
AD  - Department of Civil Engineering, University of Alberta, Edmonton,
AB  - Giardia muris cyst viability after ozonation was compared by
      using fluorescein diacetate-ethidium bromide staining, the
      C3H/HeN mouse-G. muris model, and in vitro excystation.
      Bench-scale batch experiments were conducted under laboratory
      conditions (pH 6.7, 22 degrees C) in ozone-demand-free phosphate
      buffer. There was a significant difference between fluorogenic
      staining and infectivity (P less than or equal to 0.05), with
      fluorogenic staining overestimating viability compared with
      infectivity estimates of viability. This suggests that viable
      cysts as indicated by fluorogenic dyes may not be able to
      complete the life cycle and produce an infection. No significant
      differences between infectivity and excystation and between
      fluorogenic staining and excystation (P less than or equal to
      0.05) were detected for inactivations up to 99.9%. Only animal
      infectivity had the sensitivity to detect inactivations greater
      than 99.9%. Therefore, the animal model is the best method
      currently available for detecting high levels of G. muris cyst
LA  - Eng
SO  - Appl Environ Microbiol 1991 Nov;57(11):3187-92