CTX-M-15 Producing Escherichia coli Sequence Type 361 and Sequence Type 38 Causing Bacteremia and Umbilical Infection in a Neonate Foal.
Authors: Shnaiderman-Torban Anat, Navon-Venezia Shiri, Dahan Roee, Dor Ziv, Taulescu Marian, Paitan Yossi, Edery Nir, Steinman Amir
Journal: Journal of equine veterinary science
Summary
# Editorial Summary A critically ill neonatal foal presented with classic sepsis and enterocolitis, which on investigation revealed a dual infection: two distinct multidrug-resistant *Escherichia coli* strains harbouring CTX-M-15 extended-spectrum β-lactamase (ESBL) genes were isolated from blood and umbilical tissue cultures respectively. The case involved an eighteen-hour-old Tennessee Walking Horse exhibiting leukopenia, left shift, and gastrointestinal signs, with umbilical ultrasound identifying fluid accumulation consistent with omphalitis, prompting surgical intervention and microbiological sampling. Genomic analysis identified the blood isolate as sequence type (ST) 361 and the umbilical isolate as ST38, each carrying different plasmids encoding the same *bla*CTX-M-15 resistance determinant, confirming independent pathogenic populations rather than a single clonal infection. Despite escalation to carbapenems and aminoglycosides following antimicrobial susceptibility results, the foal's condition deteriorated, with postmortem examination revealing severe ulcerative enteritis, bowel perforation and acute renal infarcts. This case underscores the emerging threat of multiclonal ESBL-producing *E. coli* infections in neonatal foals and highlights the critical importance of comprehensive microbiological investigation (including both umbilical and systemic sampling) and antimicrobial stewardship when confronted with treatment-refractory sepsis, particularly given the foal's initial response to β-lactams prior to resistance identification.
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Practical Takeaways
- •Umbilical infection in neonatal foals should be investigated urgently with culture and ultrasound imaging; fluid pockets warrant surgical intervention to prevent sepsis progression
- •ESBL-producing E. coli sepsis in foals requires culture results and resistance testing before antibiotic selection, as empirical broad-spectrum coverage may prove inadequate
- •Neonatal sepsis presenting with gastrointestinal signs, leukopenia, and multi-organ involvement carries grave prognosis even with intensive supportive care and appropriate antibiotics
Key Findings
- •An 18-hour-old foal developed sepsis from two different multidrug-resistant ESBL-producing E. coli strains (ST38 from umbilicus and ST361 from blood) harboring CTX-M-15 genes
- •Umbilical ultrasound identified a fluid pocket adjacent to the umbilical vein, leading to omphalectomy as therapeutic intervention
- •Despite treatment with imipenem and amikacin after initial cephalosporin therapy, the foal deteriorated with postmortem findings of severe ulcerative enteritis, intestinal perforation, and acute renal infarcts
- •Multiple different ESBL-producing E. coli strains can cause neonatal sepsis in foals, requiring targeted antimicrobial susceptibility testing and appropriate antibiotic selection