Inactivation of Giardia lamblia cysts by cobalt-60 irradiation.

Cysts of Giardia lamblia can be a contaminant of water and food that can infect humans and cause the zoonotic disease giardiasis. Irradiation by a cobalt-60 source was investigated for its ability to inactivate cysts such that they would not be infective to gerbils. Cysts that received doses of radiation ranging from 0.25 to 2.0 kGy, with a recovery period of 6 hr or less, did not infect gerbils. Cysts that were irradiated at 0.25 kGy and allowed to recover at 23 C in water for 24 hr or longer were infective. Temperature had an effect on the ability of cysts to regain infectivity in that cysts allowed to recover at 4 C after irradiation were not infective. Therefore, recovery time and temperature are important parameters for determination of the doses that are necessary for inactivation of this pathogen. The ability of staining with propidium iodide to predict infectivity of cysts was tested. Cysts that were damaged by higher doses of radiation and were not infective to gerbils stained similarly to viable cysts that were infective. Thus, propidium iodide is not a reliable indicator of viability and infectivity of cysts that have been treated with gamma radiation.

Comparable growth of Tritrichomonas mobilensis in two commercially available culture media.

The investigation reported herein was undertaken to determine which medium is more practical for the axenic laboratory culture of trichomonads. The growth of Tritrichomonas mobilensis was monitored in 2 different types of commercially available growth media. Although Roswell Park Memorial Institute (RPMI) 1640 medium is typically used as a mammalian cell culture medium, it was found to support the growth of trichomonads as well as the American Type Culture Collection (ATCC) medium 745 under similar conditions. Environmental variables, such as temperature and pH, known to affect the success of trichomonad cultures were controlled. The mean generation times (MGTs) of T. mobilensis in the log phase of growth were 5.1 and 4.9 hr for RPMI 1640 and ATCC medium 745, respectively. A stationary phase of zero growth was reached more quickly in the ATCC medium 745 cultures, and in both media a phase of rapid attrition followed this period of static growth. In assessing the practicality of the media, total cell amplification, as well as factors such as cost, ease of preparation, and storage capacity, were considered.

Localization of post-translationally modified alpha-tubulin and pseudocyst formation in tritrichomonads.

The distribution of acetylated tubulin was investigated in members of the Tritrichomonadinae subfamily using a specific monoclonal antibody and indirect immunofluorescence microscopy. Species probed in this study were: Tritrichomonas foetus, T. mobilensis, T. muris, and an unnamed tritrichomonad isolated from the cecum of cotton rats (Sigmodon hispidus). Additionally, the distribution of glutamylated tubulin in T. muris was investigated using the GT 335 antibody to the glutamyl motif. Although acetylated alpha-tubulin was ubiquitously distributed throughout the axostyle and flagella of T. foetus and T. mobilensis, a distinct and unusual labeling pattern was observed in 'T. muris'-type or pseudocyst-forming trichomonads. In trophozoite stages of T. muris and the cotton rat isolate, flagella were intensely labeled, but acetylation of axostylar tubulin appeared to be limited to the anterior and posterior thirds. However, trophozoites labeled with an antibody to alpha-tubulin or glutamylated tubulin demonstrated no such discontinuity in axostylar staining. Additionally, pseudocysts labeled with anti-alpha-tubulin and anti-acetylated alpha-tubulin were all found to possess continuously fluorescent axostyles. That the mid-region axostyle remained unlabeled by anti-acetylated tubulin in trophozoites indicates possible deacetylase activity, which may have functional implications with respect to the life cycle. Glutamylated tubulin appeared to be distributed throughout the axostyle and flagella, which fluoresced brightly in T. muris.