Equis ISSN 2398-2977

Penis: bacterial colonization

Contributor(s): Sarah Binns, Terry Blanchard, Graham Munroe, Sarah Stoneham, Prof Peter Timoney, Madeleine L H Campbell

Introduction

  • Bacteria are commonly isolated from the penis; harmless commensals must be differentiated from agents of venereal disease.
  • Cause: significant organisms (agents of venereal, ie contagious disease) are Klebsiella pneumoniae, Pseudomonas aeruginosa and Taylorella equigenitalis.
  • Signs: subclinical infection or colonization on external genitalia of stallions. Most commonly, stallion is lesionless carrier. Rarely, a stallion may have internal accessory sex gland infection with Pseudomonas resulting in purulent material being present in ejaculates.
  • Diagnosis: microbiologic culture of swabs from appropriate sites.
  • Treatment: removal of smegma; administration of antimicrobials if necessary.
  • Prognosis: good with appropriate therapy.

Pathogenesis

Etiology

  • Normal microflora of the stallion's external genitalia rarely produce reproductive tract infection in immunologically competent mares.
  • Bacteria that may cause individual cases of acute endometritis in in-contact mares, usually prone to repeat uterine infections:
  • Bacteria that may cause outbreaks of contagious acute endometritis in in-contact mares:

Predisposing factors

General

  • Normal bacterial flora of penis influenced by:
    • Flora in local environment.
    • Fecal contamination.
    • Housing.
    • Breeding management.

Specific

  • Breeding to a contaminated mare.
  • Removal of commensal bacteria by overzealous washing with antiseptic solutions predisposes stallion to infection with potentially pathogenic bacteria.
  • Iatrogenic transfer between stallions or stallion/mare via breeding area, personnel or equipment. Poor hygiene.
  • Parasitism of the penis and prepuce predispose to secondary bacterial infection.

Pathophysiology

  • Organisms can be transmitted to the mare's reproductive tract at time of breeding.
  • Most bacteria colonizing the penis and prepuce are skin commensals, eg coagulase-negative staphylococci, alpha-hemolytic streptococci and coryneforms.
  • There is unavoidable contamination of the mare's reproductive tract with such organisms.
  • Commenal organisms do not normally cause disease in mares, but some pathogenic organisms, eg Streptococcus zooepidemicus and E. coli, can cause occasional cases of endometritis in susceptible mares bred to the stallion.
  • K. pneumoniae, P. aeruginosa and T. equigenitalis are true venereal pathogens, ie are contagious between stallion and mare and vice versa, and can cause venereal disease in mares.
  • K. pneumoniae, P. aeruginosa, T. equigenitalis → no lesions or systemic disease in stallions (K. pneumoniaemay occasionally cause urethral lesions → hemospermia) → mechanical transmission by smegma → bacterial endometritis Uterus: endometritis - bacterial or contagious equine metritis Uterus: contagious equine metritis in mares. Pseudomonas aeruginosa may occasionally cause infection of accessory sex glands of stallion → resultant purulent material in ejaculates. These organisms persist in the smegma of carrier stallions.
  • Commensals and normal flora in smegma discourage growth of pathogenic bacteria.
  • Disruption of normal flora may result in potentially pathogenic bacteria colonizing penis and prepuce.
  • Bacteria can be spread in fresh, chilled or frozen semen being used for artificial insemination despite the inclusion of antibiotics in semen extenders.

Timecourse

  • Usually persistent colonization or infection.

Epidemiology

  • Commensal bacteria are obtained from the environment (especially soil/water) or fecal contamination.
  • Other bacteria may be transmitted, particularly between stallions and mares, especially the agents that can cause contagious endometritis: K. pneumoniae, P. aeruginosa and T. equigenitalis.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

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