Novel Pseudomonas aeruginosa Therapy in a Stallion — Case Report

Although embedded pathogenic presence in the stallion’s reproductive tract is a comparatively rare condition, it can lead to significant complications which may include shedding of the pathogen in the semen. If the pathogen is transmissible to mares, then that can lead to infections in mare subsequent to cover or insemination. This novel Pseudomonas aeruginosa therapy in a stallion, presented at the 2025 International Symposium on Stallion Reproduction, reviews a possible new treatment protocol.

Novel Pseudomonas aeruginosa Therapy - stallion surrounded by Pseudomonas aeruginosa bacteriaCase Presentation:

  • 14-year-old Holsteiner stallion; pre-cryopreservation infectious screening
  • Pseudomonas aeruginosa (PA) isolated from urethral fossa (UF), urethral orifice (UO), and pre-ejaculatory fluid (PF); sensitivity restricted to amikacin only

Phase 1 — Topical Penile Therapy (7 days):

  • Hypochlorous acid rinse + silver sulfadiazine cream under light sedation
  • Partial response by Day 4; pyospermia and Pseudomonas aeruginosa confirmed Day 5
  • Transrectal ultrasound indicated seminal vesiculitis
  • Pseudomonas aeruginosa returned at all 4 sites 4 days post-therapy — treatment insufficient alone

Phase 2 — Urethroscopic Vesicle Intervention:

  • Trans-endoscopic catheterisation and lavage of both seminal vesicles
  • Gelified amikacin infusion (pH 7.3): amikacin sulphate + sodium bicarbonate + carboxymethylcellulose
  • Right vesicle confirmed Pseudomonas aeruginosa-positive; both vesicles culture-negative by 4th treatment

Phase 3 — Repeat Penile Therapy + Microbiome Restoration:

  • 6-day penile treatment repeated across urethral fossa, urethral orifice, and penile sheath (PS)
  • Novel commensal bacterial broth (Guar gum-gelified) applied for 3 days
  • Final screening: PCR and culture negative at all sites

Outcome & Significance:

  • Semen PCR-negative at 53-day follow-up
  • Confirms penile surface therapy alone is insufficient when accessory gland involvement is present
  • Gelified local drug delivery and microbiome restoration represent novel therapeutic strategies in equine reproductive medicine

(Crabtree J, Romero Serrano Y, Cooke C. 2025. Novel therapy of Pseudomonas aeruginosa in the stallion: A case report. JEVS 145:105277 – Presented in Association with and by Permission of the International Society for Equine Reproduction)