Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants.

Authors: Nadruz Veridiana, Beard Laurie A, Delph-Miller Katherine M, Larson Robert L, Bai Jianfa, Chengappa Muckatira M

Journal: Journal of veterinary internal medicine

DOI: 10.1111/jvim.16740 PubMed: 37232523Log in to save

Summary

# Editorial Summary: Endoscope Disinfection and Strangles Control Strangles outbreaks require guttural pouch endoscopy for diagnosis and treatment, but contaminated endoscopes pose a significant re-infection risk if disinfection protocols fail to eliminate *Streptococcus equi* subspecies *equi* (the causative agent). Nadruz and colleagues (2023) evaluated whether two commonly used high-level disinfectants could reliably remove both viable bacteria and residual DNA from deliberately contaminated endoscopes, since detection of DNA alone via qPCR can create false-positive diagnoses in cleared horses. Their testing demonstrated differential efficacy between the disinfectants: one successfully eliminated both bacterial viability and DNA, whilst the other removed viable organisms but left detectable DNA fragments behind—a critical distinction when interpreting post-treatment diagnostic samples. For equine practitioners managing strangles cases, these findings underscore the importance of both rigorous endoscope disinfection protocols and careful interpretation of qPCR results in the context of culture status, particularly when determining whether a horse has genuinely cleared infection or merely appears positive due to residual DNA from previous contamination.

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Practical Takeaways

•Ensure endoscopes are properly disinfected between horses during S. equi outbreak investigations to avoid false positive carrier diagnoses from residual DNA
•Use both culture and qPCR testing on guttural pouch lavage samples, as qPCR may detect residual DNA if disinfection is inadequate
•Verify that your disinfection protocol eliminates both live bacteria and DNA to reliably identify truly infected horses versus those with equipment contamination

Key Findings

•Study evaluated efficacy of two different disinfectants for eliminating S. equi and its DNA from contaminated endoscopes
•Disinfection must eliminate both bacterial cells and DNA to prevent false positive diagnoses in carrier horse screening
•Endoscopic lavage of guttural pouches combined with culture and qPCR testing is the recommended approach for post-outbreak disease prevention

Conditions Studied

streptococcus equi subspecies equi contaminationendoscope disinfectionguttural pouch infection

Related References

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Verheyen K, Newton J R, Talbot N C, de Brauwere M N, Chanter N(2000)Equine veterinary journal

Development of a real-time PCR to detect Streptococcus equi subspecies equi.

North S E, Wakeley P R, Mayo N, Mayers J, Sawyer J(2014)Equine veterinary journal

Control of strangles outbreaks by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi.

Newton J R, Verheyen K, Talbot N C, Timoney J F, Wood J L, Lakhani K H, Chanter N(2000)Equine veterinary journal

A study of the environmental survival of Streptococcus equi subspecies equi.

Durham A E, Hall Y S, Kulp L, Underwood C(2018)Equine veterinary journal

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