Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization.
Authors: Theelen Mathijs J P, Wilson W David, Byrne Barbara A, Edman Judy M, Kass Philip H, Mughini-Gras Lapo, Magdesian K Gary
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Neonatal sepsis in foals frequently requires antimicrobial adjustment when clinical improvement plateaus, yet little was known about how the bacterial population and drug susceptibility profiles change during hospitalization. Researchers retrospectively analysed bacteriological cultures from 267 septic foals admitted to neonatal intensive care, comparing isolates obtained at admission against those cultured ≥48 hours into hospitalization, and evaluated antimicrobial susceptibility patterns across both timepoints. Notable shifts in bacterial prevalence emerged after 48 hours, with Enterococcus spp. rising from 4.8% to 19.6% of isolates, Pseudomonas spp. increasing from 3.0% to 7.6%, and Acinetobacter spp., Klebsiella spp., and Serratia spp. similarly becoming more frequently isolated—concerning given that bacteria cultured later in hospitalisation demonstrated reduced susceptibility to nearly all tested antimicrobials, with imipenem as the notable exception. These findings support the clinical practice of reculturing and repeating susceptibility testing in hospitalised foals whose condition fails to improve, as relying solely on admission cultures may lead to inappropriate antimicrobial coverage against opportunistic, multidrug-resistant organisms acquired during the hospital stay itself.
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Practical Takeaways
- •Repeat bacteriological culture and susceptibility testing should be performed in hospitalized foals with sepsis that are not responding clinically, as bacterial isolates and their antimicrobial resistance profiles change significantly after 48 hours
- •Enterococcus and Pseudomonas species become much more prevalent after 48 hours of hospitalization, suggesting nosocomial acquisition; adjust treatment protocols accordingly if initial therapy fails
- •Imipenem may retain efficacy against later isolates when other antimicrobials show reduced susceptibility in non-responsive foals
Key Findings
- •Isolation rates of Enterococcus spp. (4.8% to 19.6%), Pseudomonas spp. (3.0% to 7.6%), Acinetobacter spp. (0.6% to 3.3%), Klebsiella spp. (5.1% to 10.9%), and Serratia spp. (3.0% to 5.4%) significantly increased after ≥48 hours of hospitalization
- •Bacteria isolated after ≥48 hours of hospitalization demonstrated decreased susceptibility to all tested antimicrobial drugs except imipenem
- •57 of 267 foals (21.3%) had positive cultures obtained ≥48 hours after admission, compared to 231 foals (86.5%) with positive cultures at admission