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The Canadian veterinary journal = La revue veterinaire canadienne2023; 64(6); 549-552;

Relationship between quantitative real-time PCR cycle threshold and culture for detection of Streptococcus equi subspecies equi.

Abstract: To compare PCR and culture results for the detection of subspecies . Respiratory tract samples (N = 158) from horses being tested for Bacterial culture was carried out on samples from which was detected by quantitative real-time PCR. was isolated from 12 (7.6%) samples: 4/9 (44%) samples when the PCR cycle threshold (C) was ≤ 30, 7/30 (23%) when the C was 30.1 to 35, and 1/119 (0.8%) when the C was 35.1 to 40. The highest C sample from a sample that yielded a positive culture was 36.9. The optimal Youden's J value was at a C of 34.2, the same value as determined by number needed to misdiagnose when the cost of a false negative is deemed to be either 5 or 10 × that of a false positive. Viable was only detected in a minority of quantitative PCR (qPCR) positive samples. A qPCR C of 34.2 was a reasonable breakpoint for likelihood of the presence of culturable Evaluation of C values may be useful as a proxy to indicate the likelihood of cultivable being present and could be useful as part of risk assessments. Relation entre le seuil du cycle de PCR quantitatif en temps réel et la culture pour la détection de sous-espèce . Comparer les résultats de PCR et de culture pour la détection de sous-espèce (). Échantillons des voies respiratoires (N = 158) de chevaux testés pour . La culture bactérienne a été réalisée sur des échantillons à partir desquels a été détecté par PCR quantitatif en temps réel. a été isolé à partir de 12 échantillons (7,6 %) : 4/9 (44 %) échantillons lorsque le seuil du cycle de PCR (C) était ≤ 30, 7/30 (23 %) lorsque le C était de 30,1 à 35 et 1/119 (0,8 %) lorsque le C était de 35,1 à 40. L’échantillon C le plus élevé d’un échantillon ayant donné une culture positive était de 36,9. La valeur J optimale de Youden était à un C de 34,2, la même valeur que celle déterminée par le nombre nécessaire pour un mauvais diagnostic lorsque le coût d’un faux négatif est estimé à 5 ou 10 × celui d’un faux positif. Du viable n’a été détecté que dans une minorité d’échantillons positifs pour le PCR quantitatif (qPCR). Un C qPCR de 34,2 était un seuil raisonnable pour la probabilité de la présence de cultivable. L’évaluation des valeurs C peut être utile comme approximation pour indiquer la probabilité de présence de cultivable et pourrait être utile dans le cadre d’une évaluation des risques.(Traduit par D Serge Messier).
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Publication Date: 2023-06-02 PubMed ID: 37265809PubMed Central: PMC10204887
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research investigated the correlation between PCR testing and culture results for detecting Streptococcus equi subspecies equi in horses. The study demonstrated that a PCR cycle threshold of 34.2 is a reasonable breakpoint to measure the probability of culturable bacteria being present, which could be useful for risk assessments.

Research method and objectives

  • The study was conducted to compare the results obtained from PCR (Polymerase Chain Reaction) testing and bacterial cultivation for detecting the presence of Streptococcus equi subspecies equi in horses’ respiratory samples.
  • The respiratory tract samples were collected from horses being tested for this bacteria.
  • These samples were subjected to quantitative real-time PCR testing, and bacterial culture was carried out on samples where the Streptococcus equi subspecies equi was detected via the PCR.

Findings and Analysis

  • The bacteria Streptococcus equi subspecies equi was isolated from 7.6% of the total samples. A higher rate (44%) of positive cultures was observed when the PCR cycle threshold was less than or equal to 30, this rate drops to 23% when the threshold was between 30.1 and 35, and falls significantly to 0.8% when the threshold was 35.1 to 40.
  • The PCR cycle threshold, referred to here as C, of a sample that yielded a positive culture was highest at 36.9.
  • A cycle threshold (C) of 34.2 was found to be the optimal border point to measure the likelihood of culturable bacteria being present according to the Youden’s J value. The same value (34.2) was identified as the optimal point when considering the consequences of misdiagnosis, specifically when the cost of a false negative diagnosis is either 5 or 10 times that of a false positive.

Conclusion and Implications

  • Viable Streptococcus equi subspecies equi was only detected in a minority of the PCR positive samples, indicating a limited correlation between quantitative PCR positive results and the presence of culturable bacteria.
  • The study affirmed that a PCR cycle threshold of 34.2 could be a reasonable indicator for the presence of culturable Streptococcus equi subspecies equi bacteria. This threshold could potentially be incorporated as part of risk assessments.
  • The study emphasizes the role of cycle threshold values as a significant proxy for assessing the likelihood of culturable bacteria being present. This understanding could aid in future research and diagnostics relating to Streptococcus equi subspecies equi and similar bacterial infections.

Cite This Article

APA
Weese JS, Saab M, Moore A, Cai H, McClure JT. (2023). Relationship between quantitative real-time PCR cycle threshold and culture for detection of Streptococcus equi subspecies equi. Can Vet J, 64(6), 549-552.

Publication

The Canadian veterinary journal = La revue veterinaire canadienne
ISSN: 0008-5286
NlmUniqueID: 0004653
Country: Canada
Language: English
Volume: 64
Issue: 6
Pages: 549-552

Researcher Affiliations

Weese, J Scott
  • Department of Pathobiology and Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario NIG 2W1 (Weese); Diagnostic Services (Saab) and Department of Health Management (Saab, McClure), Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3; Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs, 5th Floor NW, 1 Stone Road West, Guelph, Ontario N1G 4Y2 (Moore); Animal Health Laboratory, University of Guelph, 419 Gordon Street, Guelph, Ontario N1G 2W1 (Cai).
Saab, Matt
  • Department of Pathobiology and Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario NIG 2W1 (Weese); Diagnostic Services (Saab) and Department of Health Management (Saab, McClure), Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3; Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs, 5th Floor NW, 1 Stone Road West, Guelph, Ontario N1G 4Y2 (Moore); Animal Health Laboratory, University of Guelph, 419 Gordon Street, Guelph, Ontario N1G 2W1 (Cai).
Moore, Allison
  • Department of Pathobiology and Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario NIG 2W1 (Weese); Diagnostic Services (Saab) and Department of Health Management (Saab, McClure), Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3; Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs, 5th Floor NW, 1 Stone Road West, Guelph, Ontario N1G 4Y2 (Moore); Animal Health Laboratory, University of Guelph, 419 Gordon Street, Guelph, Ontario N1G 2W1 (Cai).
Cai, Hugh
  • Department of Pathobiology and Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario NIG 2W1 (Weese); Diagnostic Services (Saab) and Department of Health Management (Saab, McClure), Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3; Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs, 5th Floor NW, 1 Stone Road West, Guelph, Ontario N1G 4Y2 (Moore); Animal Health Laboratory, University of Guelph, 419 Gordon Street, Guelph, Ontario N1G 2W1 (Cai).
McClure, J Trenton
  • Department of Pathobiology and Centre for Public Health and Zoonoses, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario NIG 2W1 (Weese); Diagnostic Services (Saab) and Department of Health Management (Saab, McClure), Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3; Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs, 5th Floor NW, 1 Stone Road West, Guelph, Ontario N1G 4Y2 (Moore); Animal Health Laboratory, University of Guelph, 419 Gordon Street, Guelph, Ontario N1G 2W1 (Cai).

MeSH Terms

  • Animals
  • Horses
  • Real-Time Polymerase Chain Reaction / veterinary
  • Streptococcus equi / genetics
  • Streptococcal Infections / diagnosis
  • Streptococcal Infections / veterinary
  • Horse Diseases / diagnosis
  • Horse Diseases / microbiology

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This article includes 11 references
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Citations

This article has been cited 1 times.
  1. Dehghani M, Norouzi H, Dehghan S, Spruill ML, Goodarzi M, Lee KH, Martin HL. Comparative diagnostic evaluation of real-time PCR and culture for detecting pathogens in podiatric wound infections. Microbiol Spectr 2026 Jan 6;14(1):e0264925.
    doi: 10.1128/spectrum.02649-25pubmed: 41269024google scholar: lookup
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