Cross-contamination between samples is one of the most common pre-analytical errors and can cause misleading diagnostic results, Casondra Snow, a first year DVM student at the University of Minnesota, explained during her research presentation at the Allen D. Leman Swine Conference.
As part of a research group that focuses on answering field-based questions and solving issues faced by practitioners in veterinary medicine, Snow said one of the concerns she kept hearing about was the potential for cross-contamination during sample collection.
“Cross contamination is something that can occur during sample collection, especially for deep tracheal catheters since there are so many materials required to come into contact with the catheter,” she explained. “The disinfection of materials between sample collections in order to avoid cross contamination has not previously been standardized for Mycoplasma hyopneumoniae.”
Recent studies illustrating the issue of sample contamination emphasize DNA’s significant resistance to degradation when on environmental surfaces, which is undoubtedly an important problem for PCR testing and posterior result interpretation.
“The objective of this study was to compare the effect of various disinfecting compounds to minimize sample cross-contamination in swine tracheal secretion collection,” she said.
For this study, researchers started by contaminating deep tracheal catheter sampling materials artificially in the lab with cultured M. hyopneumoniae, and naturally, in a farm with pigs that had been infected with M. hyopneumoniae. Then, they collected samples from all the materials after they were contaminated but before disinfecting them.
“We then disinfected them with various disinfecting wipes, including several commercially available products as well as a control treatment. Following disinfection, the materials were rinsed and post-disinfecting samples were collected. We tested all samples with PCR for M. hyopneumoniae to obtain and analyze their results,” Snow said.
The material sets were cleaned with one of the following treatment-based wipes: hydrogen peroxide, alkyl dimethyl benzyl ammonium chloride, bleach, alcohol, or phosphate-buffered saline (PBS).
“The main takeaway of this study was that bleach-based wipes are the best way to completely decontaminate materials and minimize or eliminate the potential for misleading diagnostic results as bleach was the only disinfectant that resulted in the removal (or destruction) of all M. hyopneumoniae genetic material for both artificial and natural contamination methods,” Snow shared.
She said these results are helpful for understanding the bigger picture of biosecurity for M. hyopneumoniae.
“This study can be used as a jumping-off point for further research in developing a M. hyopneumoniae disinfection protocol to be used in production facilities,” Snow added. “It has been a great experience to listen to the people facing diagnostic challenges at farms, to work in the lab and in the field, and communicate the results to the people who can use it. It feels like completing the circle.”
Snow was one of the seven students competing for the 2023 Morrison Swine Innovator Prize.
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