Pathogens frequently associated with multi-drug resistant (MDR) phenotypes,
including extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae
(ESBL-E) and Acinetobacter baumannii isolated from horses admitted to horse
clinics, pose a risk for animal patients and personnel in horse clinics. To
estimate current rates of colonization, a total of 341 equine patients were
screened for carriage of zoonotic indicator pathogens at hospital admission.
Horses showing clinical signs associated with colic (n = 233) or open wounds
(n = 108) were selected for microbiological examination of nostril swabs,
faecal samples and wound swabs taken from the open wound group. The results
showed alarming carriage rates of Gram-negative MDR pathogens in equine
patients: 10.7% (34 of 318) of validated faecal specimens were positive for
ESBL-E (94%: ESBL-producing Escherichia coli), with recorded rates of 10.5%
for the colic and 11% for the open wound group. 92.7% of the ESBL-producing E.
coli were phenotypically resistant to three or more classes of antimicrobials.
A. baumannii was rarely detected (0.9%), and all faecal samples investigated
were negative for Salmonella, both directly and after two enrichment steps.
Screening results for the equine nostril swabs showed detection rates for
ESBL-E of 3.4% among colic patients and 0.9% in the open wound group, with an
average rate of 2.6% (9/340) for both indications. For all 41 ESBL-producing
E. coli isolated, a broad heterogeneity was revealed using pulsed-field gel
electrophoresis (PFGE) patterns and whole genome sequencing (WGS) -analysis.
However, a predominance of sequence type complex (STC)10 and STC1250 was
observed, including several novel STs. The most common genes associated with
ESBL-production were identified as blaCTX-M-1 (31/41; 75.6%) and blaSHV-12
(24.4%). The results of this study reveal a disturbingly large fraction of
multi-drug resistant and ESBL-producing E. coli among equine patients, posing
a clear threat to established hygiene management systems and work-place safety
of veterinary staff in horse clinics