Diagnostic performance and application of a real-time PCR assay for the detection of Salmonella in fecal samples collected from hospitalized horses with or without signs of gastrointestinal tract disease.

The research article discusses the efficiency of a real-time PCR (Polymerase Chain Reaction) assay in detecting Salmonella in the fecal samples of hospitalized horses, demonstrating that it can be successfully used for initial screening of the disease in such cases.

Objective of Research

• The primary goal of the investigation was to evaluate the ability of a real-time Polymerase Chain Reaction (PCR) assay to detect Salmonella in fecal samples from hospitalized horses exhibiting symptoms of gastrointestinal (GI) disease.

Methodology of Research

• The research used a PCR assay that utilizes primers and a probe targeting the invA gene of Salmonella.
• The study’s assumptions were 100% sensitivity and 96.6% specificity, based on a disease prevalence of 2%, 5%, and 10-15% amongst the studied horses.

Findings of Research

• The PCR assay yielded a 100% negative predictive value, indicating a high reliability with negative results.
• The positive predictive value varied from 37% in horses without signs of GI disease and negative Salmonella culture, to 60% in symptomatic horses with a negative Salmonella culture, and finally to 76-83% in symptomatic horses testing positive for Salmonella culture.
• This indicates that the value of this assay increases in conjunction with disease symptoms and a positive culture test.

Applications of Research

• The study concludes that the real-time PCR that targets the Salmonella invA gene can serve as an effective screening test for Salmonella detection in fecal samples of hospitalized horses showing signs of GI disease.
• For horses testing positive in the PCR assay, a series of bacteriologic cultures can be undertaken to minimize false positive results or to gather additional relevant information, such as antibiogram and serotyping data. This can help identify potential hospital-acquired (nosocomial) Salmonella infections.