Efficacy of Elution Solutions to Detect Cyclospora cayetanensis, Cryptosporidium parvum, and Toxoplasma gondii from Basil

Introduction: Parasitic diseases can be acquired by ingestion of contaminated raw or minimally processed fresh produce (herbs and fruits). The sensitivity of methods used to detect parasites on fresh produce depends in part on the efficacy of wash/elution solutions in recovering them from suspect samples.

Purpose: Identify the efficacy of elution solutions to detect Cyclospora, Cryptosporidium, and Toxoplasma oocysts from basil.

Methods: In this study, six wash solutions (sterile E-Pure water, 3% levulinic acid-3% sodium dodecyl sulfate, 1 M glycine, 0.1 M phosphate buffered saline, 0.1% Alconox®, and 1% HCl-pepsin) were evaluated for their effectiveness in recovering Cyclospora cayetanensis, Cryptosporidium parvum, and Toxoplasma gondii from basil. One hundred and 1,000 oocysts of these parasites were inoculated on adaxial surfaces of 25 g of basil leaves placed in stomacher bags, and stored for 1 h at 21°C and 24 h at 4°C. The leaves were hand washed in each wash solution for 1 min. DNA was extracted from the wash solutions and amplified using PCR for the detection of all parasites.

Results: Oocysts inoculated at a concentration of 1,000 oocysts/25 g of basil were detected in all wash solutions. At an inoculum concentration of 100 oocysts/25 g, oocysts were detected in 18.5 to 92.6% of the wash solutions. The lowest variability in recovering oocysts from basil inoculated with 100 oocysts was observed in 1% HCl-pepsin wash solution. Oocyst recovery rates were higher at 1 h compared to 24 h post-inoculation.

Significance: Unlike most bacteria, parasites cannot be enriched; therefore, an optimal recovery process for oocysts from suspected foods is critical. Observations in this study provide guidance concerning the selection of wash solutions giving highest retrieval of parasites oocysts.