(E49) Antimicrobial Susceptibility of Bacterial Isolates Recovered from Sick Neonatal Foals

Abstract: Background - Neonatal septicemia and its sequelae cause death and morbidity in foals. Clinicians require knowledge of geographically specific pathogens and their antibiotic resistance (AMR) patterns to guide treatment while awaiting antimicrobial susceptibility results. Data to guide the initial treatment of foals in Ontario are unavailable. Hypothesis/Objectives - Pathogens and AMR and multidrug resistance (MDR) patterns are geographically unique. This study aimed to identify the bacterial species, AMR and MDR of isolates from sick foals in Ontario. Animals – All foals < 1 mo hospitalized at Ontario Veterinary College during 2024. Methods - This study was a prospective cohort study. Blood obtained on admission, 48 h and 72 h, and other samples, underwent aerobic and anerobic bacterial culture and identification. Antimicrobial susceptibilities were determined by minimum inhibitory concentrations. Logistic regression identified factors associated with MDR. Results - Blood (84), umbilicus (5), and synovial fluid (7) submissions from 79 foals produced 99 isolates. Escherichia coli (21%), Enterococcus spp. (18%), Streptococcus spp. (17%) and Staphylococcus spp. (12%) were most common. AMR was highest for tetracyclines (72%; 67/93) and beta-lactams (55%; 52/95). MDR rate was 54%; highest for E. coli (67%;14/21) and Klebsiella spp. (43%; 4/7) isolates. Antibiotic administration (P=0.014), multiple antimicrobials (P=0.002) and use of beta-lactam antibiotics (P=0.003) increased the odds of MDR. Conclusions - The prevalence of MDR, particularly in E. coli and other endemic bacteria from sick neonatal foals in Ontario, preadmission antimicrobial use, and extended hospitalization-associated MDR risk, emphasize the need for targeted stewardship.