Evaluation of a nested PCR test and bacterial culture of swabs from the nasal passages and from abscesses in relation to diagnosis of Streptococcus equi infection (strangles).
Abstract: Streptococcus equi is the cause of strangles in horses. To improve diagnostic sensitivity, development and evaluation of DNA-based methods are necessary. Objective: To evaluate diagnostic methods and observe the pattern of bacterial shedding during natural outbreaks. Methods: Two herds with natural outbreaks of strangles were visited over a period of 15 weeks and 323 samples originating from 35 horses investigated. The diagnostic use of a nested PCR test was evaluated using a collection of 165 isolates of Lancefield group C streptococci (species specificity) and swabs from nasal passages or from abscesses from horses infected with S. equi (diagnostic sensitivity). Results: All 45 S. equi isolates tested positive in the nested PCR, whereas no amplicon was formed when testing the other 120 Lancefield group C isolates. A total of 43 samples were collected from 11 horses showing clinical signs of strangles during the study period. The diagnostic sensitivity for PCR test was 45% and 80% for samples from the nasal passages and abscesses, respectively; the corresponding diagnostic sensitivity for cultivation was 18% and 20%. The diagnostic sensitivity was significantly higher for PCR than for bacterial cultivation. Furthermore, the shedding of S. equi in 2 infected horse populations was evaluated. An intermittent shedding period of S. equi of up to 15 weeks was recorded in this part of the study. It was also shown that shedding of S. equi occurred both from horses with and without clinical signs. Conclusions: The nested PCR test represents a species-specific and -sensitive method for diagnosis of S. equi from clinical samples. It may, however, be desirable in future to develop detection methods with high diagnostic sensitivity and specificity without the potential problems inherent in nested PCR.
Publication Date: 2006-01-18 PubMed ID: 16411588DOI: 10.2746/042516406775374324Google Scholar: Lookup
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Summary
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This research article investigates the effectiveness of a nested PCR test and bacterial culture for diagnosing Streptococcus equi infection (strangles) in horses, noting that the PCR test had higher diagnostic sensitivity. The study also observes the pattern of bacterial shedding during natural outbreaks.
Research Methodology
- The study conducted over 15 weeks involved two herds experiencing natural strangles outbreaks. A total of 323 samples from 35 horses were examined.
- The researchers evaluated a nested PCR test’s diagnostic use using a collection of 165 isolates of Lancefield group C streptococci for species specificity. They also tested swabs from nasal passages or abscesses from horses infected with S. equi for diagnostic sensitivity.
Results
- All 45 S. equi isolates tested positive in the nested PCR, indicating high species sensitivity. The other 120 Lancefield group C isolates tested revealed no amplicon, corroborating the PCR’s specificity.
- For samples taken from the nasal passages and abscesses, the PCR test had a diagnostic sensitivity of 45% and 80% respectively. In comparison, bacterial cultivation showed diagnostic sensitivity of 18% and 20%, identifying the PCR test as significantly more sensitive.
- Researchers assessed the shedding of S. equi in two infected horse populations, revealing an intermittent shedding period of up to 15 weeks. Shedding was noted from horses both with and without clinical signs, offering new insights into the pathogen’s biology.
Conclusions
- The study found the nested PCR test a highly species-specific and sensitive method for diagnosing S. equi from clinical samples, demonstrating its potential as a reliable diagnostic tool.
- However, it is recommended that future work should aim to develop detection methods with even higher diagnostic sensitivity and specificity, without the potential problems inherent in the nested PCR methodology.
Cite This Article
APA
Grønbaek LM, Angen O, Vigre H, Olsen SN.
(2006).
Evaluation of a nested PCR test and bacterial culture of swabs from the nasal passages and from abscesses in relation to diagnosis of Streptococcus equi infection (strangles).
Equine Vet J, 38(1), 59-63.
https://doi.org/10.2746/042516406775374324 Publication
Researcher Affiliations
- Danish Institute for Food and Veterinary Research, Bülowsvej 27, DK- Copenhagen V, Denmark.
MeSH Terms
- Abscess / microbiology
- Animals
- DNA, Bacterial / analysis
- Denmark / epidemiology
- Disease Outbreaks / veterinary
- Horse Diseases / diagnosis
- Horse Diseases / epidemiology
- Horses
- Nose / microbiology
- Polymerase Chain Reaction / methods
- Polymerase Chain Reaction / veterinary
- Reproducibility of Results
- Sensitivity and Specificity
- Species Specificity
- Streptococcal Infections / diagnosis
- Streptococcal Infections / epidemiology
- Streptococcal Infections / veterinary
- Streptococcus equi / isolation & purification
Citations
This article has been cited 5 times.- Weese JS, Saab M, Moore A, Cai H, McClure JT. Relationship between quantitative real-time PCR cycle threshold and culture for detection of Streptococcus equi subspecies equi.. Can Vet J 2023 Jun;64(6):549-552.
- Brankston G, Rossi TM, O'Sullivan TL, Greer AL. Diagnostic testing patterns for Streptococcus equi subsp. equi in Ontario horses during the years 2008 to 2018.. Can Vet J 2021 Jun;62(6):629-636.
- Pilchová V, Seinige D, Hennig-Pauka I, Büttner K, Abdulmawjood A, Kehrenberg C. Development and Validation of a Loop-Mediated Isothermal Amplification (LAMP) Assay for Rapid Detection of Glaesserella (Haemophilus) parasuis.. Microorganisms 2020 Dec 25;9(1).
- Boyle AG, Stefanovski D, Rankin SC. Comparison of nasopharyngeal and guttural pouch specimens to determine the optimal sampling site to detect Streptococcus equi subsp equi carriers by DNA amplification.. BMC Vet Res 2017 Mar 23;13(1):75.
- Boyle AG, Rankin SC, D￮ L, Boston RC, Wheeler-Aceto H. Streptococcus equi Detection Polymerase Chain Reaction Assay for Equine Nasopharyngeal and Guttural Pouch Wash Samples.. J Vet Intern Med 2016 Jan-Feb;30(1):276-81.
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