Aqueous ozone exposure inhibits sporulation in the Cyclospora cayetanensis surrogate Eimeria acervulina

Authors: BAUMANN, AARON - University Of Tennessee; MYERS, ADDISON - University Of Tennessee; KHAJEH-KAZEROONI, NILOOFAR - University Of Tennessee; Rosenthal, Benjamin; Jenkins, Mark; Obrien, Celia; FULLER, LORRAINE - University Of Georgia; ZHONG, QIXING - University Of Tennessee; MORGAN, MARK - University Of Tennessee; LENAGHAN, SCOTT - University Of Tennessee

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2024
Publication Date: 3/8/2024
Citation: Baumann, A.A., Myers, A.K., Khajeh-Kazerooni, N., Rosenthal, B.M., Jenkins, M.C., Obrien, C.N., Fuller, L., Zhong, Q., Morgan, M., Lenaghan, S.C. 2024. Aqueous ozone exposure inhibits sporulation in the Cyclospora cayetanensis surrogate Eimeria acervulina. Journal of Food Protection. 87(5): Article e10026. https://doi.org/10.1016/j.jfp.2024.100260.
DOI: https://doi.org/10.1016/j.jfp.2024.100260

Interpretive Summary: Produce safety is compromised by contamination with Cyclospora cayetanensis, a cause of enteric disease. Enhancing produce safety by preventing or delaying parasite maturation to its infectious state would benefit consumers and produce growers. Because it is difficult to source (and impossible to grow in the lab) these parasites, few interventions have so far been attempted. Therefore, a USDA research team partnered with academic colleagues to study the responses of related parasites (Eimeria of chickens) to one such intervention: ozonated water. They discovered that the parasites respond in a dose-dependent way to ozonated water, which proved capable of reducing parasite maturation by over 90%, especially when the ozone was stabilized by addition of citric acid. These data herald a promising new approach to managing a harmful produce pathogen and will interest produce growers and packers, grocers, food safety professionals, and parasitologists.

Technical Abstract: Ozone is a potent disinfecting agent used to treat potable water and wastewater, effectively clearing protozoa such as Giardia and Cryptosporidium spp. It is unclear whether ozone treatment of water or fresh produce can reduce the spread of the emerging parasite Cyclospora cayetanensis, which causes cyclosporiasis in humans. Obtaining viable C. cayetanensis oocysts to evaluate inactivation methods is challenging because we lack the means to propagate them in vitro, because of delays in case reporting, and because health departments typically add inactivating fixatives to clinical specimens. Research in various surrogate organisms has sought to bolster understanding of the biology of C. cayetanensis. Among these surrogates is the poultry parasite Eimeria acervulina, a closely related and easily cultured parasite of economic significance. We used this surrogate to evaluate the consequences of ozone treatment, using the sporulation state as an indicator of infectious potential. Treating with ozonated water acidified with citric acid reduced sporulation ability in a dose-dependent manner; treatment with up to 4.93 mg/L initial concentration of ozone resulted in a 93% inactivation of sporulation by 7 days posttreatment. This developmental arrest was accompanied by transcriptional changes in genes involved in regulating the response to reactive oxygen species (ROS) in a time course that is consistent with the production of oxygen free radicals. This study shows that ozone is highly effective in preventing sporulation of E. acervulina, a model coccidian used as a surrogate for Cyclospora. Furthermore, ozone exposure induced molecular responses to general oxidative stress, documented with several well-characterized antioxidant enzymes.