Bacteraemia in neonatal foals: clinicopathological differences between Gram-positive and Gram-negative infections, and single organism and mixed infections.
Authors: Corley K T T, Pearce G, Magdesian K G, Wilson W D
Journal: Equine veterinary journal
Summary
# Bacteraemia in Neonatal Foals: Clinical Patterns Guide Antimicrobial Selection Clinicians treating bacteraemic foals face pressure to initiate antimicrobial therapy before culture results are available, making early recognition of bacterial class critical for optimising outcomes. This retrospective analysis of 85 neonatal foals (under 10 days old) with positive blood cultures identified distinct clinical and laboratory signatures associated with Gram-negative (n=59), Gram-positive (n=13) and polymicrobial (n=19) infections, examined over a ten-year period at a university hospital. Gram-negative bacteraemia presented with notably depressed white blood cell counts and lymphocyte numbers at admission compared to Gram-positive infections, whilst mixed organism bacteraemias carried the poorest prognosis, characterised by tachycardia, electrolyte abnormalities (elevated sodium, chloride and urea nitrogen), metabolic acidosis, respiratory distress, recumbency and higher mortality. Actinobacillus species specifically correlated with profound leucopenia, neutropenia and lymphopenia alongside clinical depression at presentation. For equine practitioners, these patterns offer practical markers—particularly severely depressed white cell counts and electrolyte disturbances—that may guide empirical antimicrobial choice before definitive culture identification, potentially improving survival rates in this critical neonatal population where rapid intervention substantially influences outcome.
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Practical Takeaways
- •Clinical laboratory patterns can help guide initial antimicrobial selection in neonatal foals with suspected bacteraemia before culture results are available
- •Mixed organism infections carry a poorer prognosis and should prompt aggressive supportive care including management of acidosis, electrolyte abnormalities, and respiratory compromise
- •Recognition of specific clinical presentations (depression, leucopenia, recumbency) may indicate particular bacterial groups and inform treatment strategy
Key Findings
- •Foals with Gram-negative bacteraemia had significantly lower total white blood cell and lymphocyte counts at admission compared to those with Gram-positive infections
- •Mixed organism bacteraemia was associated with tachycardia, elevated serum sodium/chloride/urea nitrogen, acidosis, respiratory distress, recumbency, and non-survival
- •Actinobacillus spp. infections presented with leucopenia, neutropenia, lymphopenia and depression at admission
- •Gram-negative organisms were cultured in 69% of cases (n=59), Gram-positive in 15% (n=13), and mixed organisms in 22% (n=19)