Low salt exposure results in inactivation of Toxoplasma gondii bradyzoites during formulation of dry cured ready-to-eat pork sausage

Authors: Fredericks, Jorrell; Hawkins Cooper, Diane; Hill, Dolores; Luchansky, John; Porto-Fett, Anna; GAMBLE, H - National Academy Of Science; Fournet, Valsin; Urban, Joseph; GAJADHAR, A - University Of Saskatchewan; HOLLEY, R - University Of Manitoba; Dubey, Jitender

Submitted to: Food and Waterborne Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2019
Publication Date: 3/14/2019
Citation: Fredericks, J.N., Hawkins Cooper, D.S., Hill, D.E., Luchansky, J.B., Porto Fett, A.C., Gamble, H.R., Fournet, V.M., Urban Jr, J.F., Gajadhar, A.A., Holley, R., Dubey, J.P. 2019. Low salt exposure results in inactivation of Toxoplasma gondii bradyzoites during formulation of dry cured ready-to-eat pork sausage. Food and Waterborne Parasitology. 15:e00047. https://doi.org/10.1016/j.fawpar.2019.e00047.
DOI: https://doi.org/10.1016/j.fawpar.2019.e00047

Interpretive Summary: The production of safe and healthy food products represents one of the main objectives of the food industry. The presence of microorganisms in meat and products containing meat can result in a range of human health problems, as well as economic losses to producers of these products. However, contaminated meat products continue to initiate serious and large scale outbreaks of disease in consumers. In addition to outbreaks of bacteria and viruses, parasitic organisms, such as Toxoplasma gondii and Trichinella spiralis, are responsible for foodborne infections worldwide, and in the case of T. gondii , is considered the 2nd leading cause of death from foodborne illness in the U.S. Both T. gondii and T. spiralis have historically been linked to the consumption of raw or undercooked meat products, including pork. Specific concerns with respect to pork products are Ready-To-Eat (RTE) pork meals. These are pork or products containing pork that are prepared by curing or drying, and are not intended to be cooked before being consumed. In this study, we have analyzed inactivation of T. gondii in freshly prepared pepperoni batter to determine when inactivation occurs during fermentation, and what parameters of the sausage preparation are involved in inactivation of the parasite. Results indicate that exposure of T. gondii bradyzoites to low concentrations of NaCl in dry cure sausage batter results in complete inactivation of the parasite in less than 2 hours. These data demonstrate that RTE products containing pork can be rendered safe for consumption with respect to T. gondii using low salt curing processes. However, T. spiralis ML survive the batter preparation and fermentation processes, requiring additional treatment to render RTE meats safe from this parasite.

Technical Abstract: Toxoplasmosis is a zoonotic disease that occurs worldwide and is caused by the protozoan parasite Toxoplasma gondii. Toxoplasma has three infectious stages: the rapidly dividing tachyzoite, the slow growing bradyzoite (in tissue cysts), and the quiescent sporozoite (in oocysts). The consumption of raw or undercooked contaminated pork meat is a source of infection that has been regarded as a major route of T. gondii transmission to humans. Another parasitic zoonosis that presents a foodborne health hazard to humans is trichinellosis. Trichinellosis is caused by the parasitic nematode Trichinella spiralis, historically associated with consumption of undercooked game meats and pork containing the encysted 1st stage larvae of the parasite. Key control efforts in many countries have focused on the elimination of T. spiralis from the food chain using strict biosecurity for the management of commercially raised pigs. Ready-to-eat meats are a special concern since these may be consumed without further cooking and have been known to act as a vehicle for transmission of pathogenic microorganisms to consumers. Given the possibility of the presence of T. gondii and T. spiralis in pork meat, the frequent use of pork for RTE products increases the potential risk for transmission of these parasites to consumers. Current meat-curing practices have beneficial effects on meat products, such as inhibiting the growth of microorganisms, and increasing shelf life and stability. Curing methods which inactivate T. gondii and T. spiralis early in the curing process would be of great value to producers. Previous studies have demonstrated that both T. gondii and T. spiralis are inactivated during dry cured sausage preparation. However, surviving T. spiralis larvae required 7 -10 days of drying after fermentation of the sausage meat for complete inactivation, while T. gondii was completely inactivated in the batter during fermentation. In this study, we evaluated the timing of inactivation of T. gondii bradyzoites in sausage batter during fermentation using the low salt concentration identified in the previous study (1.3% NaCl) during preparation of dry cured pork sausage, presuming that this low salt concentration would provide the best-case scenario for survival of bradyzoites in sausage batter during a dry cure process, and using survival of T. spiralis muscle larvae in the same formulation batter as a comparison. Results indicate that exposure of T. gondii bradyzoites to NaCl in dry cure sausage batter in concentrations less than typically used for RTE products results in complete inactivation of the parasite in less than 2 hours. T. spiralis ML survive the low salt batter preparation and fermentation processes, requiring additional treatment to render RTE meats safe from this parasite.