Retrospective study of blood culture isolates, antimicrobial sensitivity, and survival factors from 243 neonatal foals in Normandy (France)

Background Identifying causative bacterial species in neonatal foal bacteremia and their antimicrobial susceptibility profiles is essential for guiding appropriate antibiotic therapy. Hypothesis/Objectives To describe bacterial isolates from blood culture and their antimicrobial susceptibility patterns in neonatal foals from two French institutes, and to assess associations between pretreatment and blood culture positivity, and between in-hospital death (euthanasia or natural death) and the presence of multidrug-resistant (MDR) bacteria. Animals Two hundred forty-three foals (<7 days old) admitted to two equine intensive care units in Normandy with blood cultures. Methods Retrospective cohort study. Associations were assessed using chi-square test. Results Blood cultures were positive in 43% of foals. Pretreatment was not significantly associated with blood culture positivity (P = .62). Gram-positive isolates predominated (65%). The most common isolates were Staphylococcus spp. (25%), Escherichia coli (11%), and Streptococcus spp. (11%). MDR bacteria represented 26% of isolates, predominantly Gram-positive. Low resistance to aminoglycosides, particularly amikacin (17%) and gentamicin (19%), was observed, whereas resistance to penicillin (53%) and ceftiofur (33%) was more common. Moderate resistance to tetracyclines (between 22% and 31%) was measured within overall bacteria. Similar resistance rates to trimethoprim–sulfamethoxazole and ceftiofur were observed among Gram-positive (≈ 35%) and Gram-negative isolates (26%). Presence (vs absence) of MDR isolates was not significantly associated with in-hospital death (P = .52). Conclusions and clinical importance Consistent with recent reports, Gram-positive bacteria predominated among neonatal foal blood isolates in our sample. Despite its designation as a critically important human antibiotic, resistance to ceftiofur in our study necessitates utmost restraint in its use.