Surface Properties of Toxoplasma gondii Oocysts and Surrogate Microspheres

• Published in: Applied and Environmental Microbiology Vol. 75; no. 4; pp. 1185 - 1191
• Main Authors: Shapiro, Karen, Largier, John, Mazet, Jonna A.K, Bernt, William, Ell, John R, Melli, Ann C, Conrad, Patricia A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.02.2009; American Society for Microbiology (ASM)
• Subjects: Animals; Bacteria; Biological and medical sciences; Brackish; Environmental Microbiology; Fresh Water - parasitology; Freshwater ecology; Fundamental and applied biological sciences. Psychology; Humans; Marine; Microbiology; Microspheres; Oocysts - chemistry; Seawater - parasitology; Sedimentation & deposition; Studies; Surface Properties; Toxoplasma - chemistry; Toxoplasma gondii; Water treatment; Surface properties; Protozoa; Apicomplexa; Microsphere; Toxoplasma gondii; Oocyst
• ISSN: 0099-2240; 1098-5336; 1098-6596
• DOI: 10.1128/AEM.02109-08

The physical properties that govern the waterborne transmission of Toxoplasma gondii oocysts from land to sea were evaluated and compared to the properties of carboxylated microspheres, which could serve as surrogates for T. gondii oocysts in transport and water treatment studies. The electrophoretic mobilities of T. gondii oocysts, lightly carboxylated Dragon Green microspheres, and heavily carboxylated Glacial Blue microspheres were determined in ultrapure water, artificial freshwater with and without dissolved organic carbon, artificial estuarine water, and artificial seawater. The surface wettabilities of oocysts and microspheres were determined using a water contact angle approach. Toxoplasma gondii oocysts and microspheres were negatively charged in freshwater solutions, but their charges were neutralized in estuarine water and seawater. Oocysts, Glacial Blue microspheres, and unwashed Dragon Green microspheres had low contact angles, 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 freshwater 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 freshwater and marine water mix, indicating a high risk of exposure for humans and wildlife in estuarine habitats with this zoonotic pathogen. While microspheres did not have surface properties identical to those of 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.