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.
Authors: Ekiri A B, Long M T, Hernandez J A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Real-time PCR for Salmonella Detection in Hospitalized Horses Salmonella screening in hospitalised horses remains clinically important given the risk of nosocomial transmission, yet conventional culture methods are slow and labour-intensive. Ekiri and colleagues evaluated a real-time PCR assay targeting the invA gene as a diagnostic tool for Salmonella detection in faecal samples from hospitalised horses, with and without gastrointestinal clinical signs, comparing PCR results against culture as the reference standard. The assay demonstrated excellent negative predictive value (100%), meaning a negative PCR result reliably excludes Salmonella infection; however, positive predictive value varied substantially depending on clinical presentation and culture status, ranging from 37% in asymptomatic, culture-negative horses to 83% in symptomatic, culture-positive animals. For equine practitioners, this suggests real-time PCR performs well as a rapid screening tool in horses showing gastrointestinal disease, particularly when combined with follow-up culture testing to confirm positives, obtain antimicrobial sensitivities, and identify serotypes for infection control purposes. The high sensitivity and negative predictive value make PCR particularly valuable for ruling out Salmonella quickly, whilst reflexive culture of positive samples provides both diagnostic confirmation and epidemiological data essential for managing potential nosocomial outbreaks in hospital settings.
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Practical Takeaways
- •Real-time PCR is a reliable screening tool for detecting Salmonella in hospitalized horses showing GI signs; negative results effectively rule out infection
- •Always confirm PCR-positive results with bacterial culture to reduce false positives and obtain additional diagnostic data (antibiogram, serotype) for infection control
- •Use this test strategically in hospitalized populations to identify potential nosocomial Salmonella infections and implement appropriate isolation/management protocols
Key Findings
- •Real-time PCR targeting invA gene showed 100% sensitivity and 96.6% specificity for Salmonella detection in equine fecal samples
- •Negative predictive value was 100%, providing reliable rule-out capability for Salmonella in hospitalized horses
- •Positive predictive value ranged from 37% to 83% depending on disease presentation and culture status, indicating need for confirmatory testing
- •PCR assay is suitable as screening test for Salmonella in horses with GI disease signs, with follow-up culture recommended for PCR-positive cases