Cystatin C, Ammonia, and Bicarbonate Measurements in the Saliva of Pigs: Analytical Validation and Changes in S. suis Infection.

Simple Summary: The use of saliva as a sample for the measurements of biomarkers is growing in pigs due to its easy collection, which does not produce stress in animals. Cystatin C, ammonia, and bicarbonate have been reported to be biomarkers of sepsis and inflammation in humans, but there is a lack of information about assays for the measurement of these analytes in pigs. The objective of this report was to validate commercially available assays for the measurement of Cystatin C, ammonia, and bicarbonate in the saliva of pigs and study the variations of these analytes in a septic disease such as Streptococcus suis (S. suis) infection. The assays showed adequate precision and accuracy for the measurements of the three analytes in the saliva of pigs. In addition, −80 °C was the temperature recommended to store samples for the measurement of these analytes. Pigs with S. suis infection have higher mean concentrations of cystatin and ammonia and lower concentrations of bicarbonate in their saliva than healthy pigs. Based on these results, cystatin C, ammonia, and bicarbonate can be measured in the saliva of pigs and can be potential biomarkers in this species. Cystatin C, ammonia, and bicarbonate have been described to be biomarkers of sepsis and inflammation in humans. The saliva of pigs can be used to detect a wide range of pathogens but also many biomarkers that can be analyzed to evaluate different conditions such as stress (i.e., cortisol and alpha amylase), immune system (i.e., ADA, S100 proteins), inflammation (i.e., acute phase proteins), redox status (i.e., various antioxidants and oxidants), and general metabolism or the status of different organs and tissues. However, there is a lack of assays for the possible measurement and use of cystatin C, ammonia, and bicarbonate in saliva as biomarkers of sepsis or inflammation in pigs. The objective of this study was to validate commercially available automated assays for the measurement of cystatin C, ammonia, and bicarbonate in the saliva of pigs, having the advantage of using a noninvasive sample that is easy to collect. The assays were precise and accurate, and the recommended storage condition for the saliva samples was −80 °C. In addition, cystatin and ammonia showed significant increases in the saliva of pigs with S. suis infection, whereas bicarbonate decreased. Further studies would be recommended to increase knowledge about the possible potential applications of the measurements of these three analytes in the saliva of pigs as biomarkers to evaluate the animals' health and welfare. [ABSTRACT FROM AUTHOR]