Surface properties of Toxoplasma gondii oocysts and surrogate microspheres

Appl Environ Microbiol. 2008 Dec 5. [Epub ahead of print]

Surface properties of Toxoplasma gondii oocysts and surrogate microspheres

Shapiro K, Largier J, Mazet JA, Bernt W, Ell JR, Melli AC, Conrad PA.

Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis CA 95616; Department of Environmental Science and Policy, University of California, Davis CA 95616; Wildlife Health Center, School of Veterinary Medicine, University of California, Davis. CA 95616; Particle Characterization Laboratories, Novato CA 94945; Department of Chemistry, University of California, Davis CA 95616.

Physical properties that govern waterborne transmission of Toxoplasma gondii oocysts from land to sea were evaluated and compared to properties of carboxylated microspheres that could serve as surrogates for T. gondii oocysts in transport and water treatment studies. Electrophoretic mobilities of T. gondii oocysts, lightly carboxylated Dragon Green microspheres, and heavily carboxylated Glacial Blue microspheres were determined in ultrapure water, artificial fresh water with and without dissolved organic carbon, artificial estuarine water, and artificial sea water. The surface wettabilities of oocysts and microspheres were determined using a water contact angle approach. Toxoplasma gondii oocysts and microspheres were negatively charged in fresh water solutions, but their charge was neutralized in estuarine and sea waters. Oocysts, Glacial Blue microspheres, and unwashed Dragon Green microspheres had a low contact angle indicating that they were hydrophilic; however, once washed, Dragon Green microspheres became markedly hydrophobic. The hydrophilic nature and negative charge of T. gondii oocysts in fresh water could facilitate widespread contamination of waterways. The loss of charge observed in saline waters may lead to flocculation and subsequent accumulation of T. gondii oocysts in locations where fresh and marine waters mix, indicating a high risk of exposure to humans and wildlife with this zoonotic pathogen in estuarine habitats. While microspheres did not have identical surface properties as T. gondii, similar properties shared between each microsphere type and oocysts suggest that their joint application in transport and fate studies could provide a range of transport potentials in which oocysts are likely to behave.

PMID: 19060174 [PubMed - as supplied by publisher]