Extended Spectrum β Lactamase-Producing Enterobacteriaceae (ESBL-E) Shedding in Hospitalized and Healthy Farm Horses -

Anat Shnaiderman Torban ¹ Shiri Navon-Venezia ⁶ Ziv Dor ⁶ Yossi Paitan ^2,3 Haia Arielly ³ Wiessam Abu Ahmad ⁵ Gal Kelmer ¹ Marcus Fulde ⁴ Amir Steinman ¹

¹Koret School of Veterinary Medicine (KSVM), The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Israel
²Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Israel
³Clinical Microbiology Lab, Meir Medical Center, Israel
⁴Department of Veterinary Medicine, Institute of Microbiology and Epizootics, Freie Universität Berlin, Germany
⁵Hadassah Braun School of Public Health and Community Medicine, Hebrew University of Jerusalem, Israel
⁶Molecular Biology, Faculty of Natural Science, Ariel University, Israel

Background: Companion animals, including horses, may serve as zoonotic reservoir for multidrug resistance.

Aim: To investigate prevalence, molecular characteristics and risk factors of ESBL-E shedding in different equine cohorts.

Methods: A prospective study (Oct 2015-Sep 2018) was performed sampling three cohorts: (i) on-admission horses in the Koret School of Veterinary Medicine-Veterinary Teaching Hospital (n=168); (ii) farm horses, originating from 13 different farms (n=192); (iii) Horses hospitalized for ≥72 hours re-sampled from cohort (i) (n=86). Enriched rectal swabs were plated onto CHROMagar ESBL plates and ESBL-production was confirmed (CLSI). Identification and antibiotic susceptibility were determined (Vitek-2). CTX-M ESBL genes were identified (PCR). Medical records and owners’ questioners were reviewed for risk factor analysis (SPSS).

Results: ESBL-E colonization rate increased from 20% (n=34/168, 95% CI 14-27%) on admission, to 78% (n=67/86, 95% CI 68-86%) during hospitalization (p<0.0001). Overall, 145 bacteria were isolated. The main species were E.coli (51%, 74/145), Enterobacter sp. (19%, 28/145) and Klebsiella pneumoniae (15%, 22/145). The main gene was CTX-M-1 (75%). Resistance rates were: trimethoprim-sulfa-89%, quinolones-25%, gentamicin-75%, amikacin-8%, with no resistance to carbapenems. Within farm horses, colonization rate was 21% (n=40/192, 95% CI 15-27%), with 48 bacteria isolated. The major species was E. coli (79%, 38/45) and the major gene-CTX-M-1 (95%). Resistance rates were: trimethoprim-sulfa-90%, quinolones-6%, gentamicin-75%, and 100% susceptibility to amikacin and carbapenems. Risk factors for ESBL-E colonization in farms: sex (Stallion, OR=4.18), younger-age (OR=0.899), previous hospitalization (OR=1.752) and antibiotic treatment (OR=10.624).

Conclusions: We demonstrated the potential zoonotic reservoir of ESBL-E in equine clinics and farms, as well as significant nosocomial acquisition.

Significance: Horses serve as a companion animal, accessible to both adults (veterinary hospital and farms staff) and children (mainly in farms). In light of our findings, active surveillance programs are recommended.