Infectious Endometritis in Mares: Microbiological Findings in Field Samples.
Authors: Ravaioli Valentina, Raffini Elisabetta, Tamburini Marco, Galletti Giorgio, Frasnelli Matteo
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Infectious Endometritis in Mares—Microbiological Findings in Field Samples Ravaioli et al.'s five-year retrospective analysis of 394 uterine samples from pre-breeding mares reveals critical insights into the microbiological landscape of equine infectious endometritis, a condition responsible for substantial reproductive losses across the industry. Bacterial culture was performed using both direct smearing and enrichment broth techniques on uterine swabs and lavages, with the latter involving substantially higher fluid volumes. Nearly 60% of samples yielded positive cultures (386 microorganisms from 230 samples), though the detection rate varied markedly: direct smearing identified pathogens in 33% of cases, whilst enrichment culture increased yield by a further 25%, highlighting a significant diagnostic advantage. The microbial profile was dominated by α-haemolytic Streptococcus, *Escherichia coli*, β-haemolytic Streptococcus, and *Staphylococcus* species, though monoculture infections showed different relative frequencies, with α-haemolytic Streptococcus and *Staphylococcus* spp. predominating. Uterine lavage proved substantially superior to swabbing (80% versus 53% positive yield), and differential isolation patterns emerged between Gram-negative bacteria (favouring direct smearing) and Gram-positive organisms (enrichment-dependent)—findings with direct implications for clinicians' sampling protocols and laboratory procedures when pursuing timely, accurate diagnoses that inform targeted antimicrobial therapy and minimise resistance development in subfertile mares.
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Practical Takeaways
- •Use uterine lavage rather than swabs when sampling for endometritis diagnosis, as it significantly improves detection of pathogens in mares before breeding
- •Routine enrichment culturing is essential—it detects an additional 25% of infections that would be missed by direct smearing alone, improving early diagnosis and timely treatment initiation
- •Be aware that the most common causative organisms are α-haemolytic Streptococcus, E. coli, and β-haemolytic Streptococcus, which should inform empirical antibiotic selection pending culture results
Key Findings
- •58% of uterine samples (230/394) were positive for bacterial pathogens, with 33% detected by direct smearing and an additional 25% only after enrichment culture
- •α-haemolytic Streptococcus and Escherichia coli were most frequently isolated (27% each), followed by β-haemolytic Streptococcus (26.1%) and Staphylococcus spp. (19.1%)
- •Uterine lavage demonstrated significantly higher sensitivity (80% positive) compared to uterine swabs (53% positive)
- •Gram-negative bacteria preferentially grew with direct smearing while Gram-positive bacteria were more frequently isolated following enrichment culture