Streptococcus equi subsp. zooepidemicus Strains Isolated from Mares

Streptoccoccus species are generally considered sensitive to penicillin related antibiotics. This research found a hoigh incidence of resistance to penicillins and amikacin but continued sensitivity to ceftiofur. The emphasis here is the caution of inappropriate antibiotic use: proper diagnosis and sensitivity testing should guide treatment to help ameliorate the growing problem of antibiotic resistance.
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Occurrence and Antimicrobial Susceptibility Profiles of Streptococcus equi subsp. zooepidemicus Strains Isolated from Mares with Fertility Problems
Antibiotics (Basel). 2021 Dec 27;11(1):25.
Authors
Francesca Paola Nocera 1 , Elena D’Eletto 1 , Monica Ambrosio 1 , Filomena Fiorito 1 , Ugo Pagnini 1 , Luisa De Martino 1 2
Affiliations

1 Department of Veterinary Medicine and Animal Production, University of Naples “Federico II”, Via F. Delpino 1, 80137 Naples, Italy.
2 Task Force on Microbiome Studies, University of Naples “Federico II”, Naples, 80137, Italy.

Abstract

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus), is a β-hemolytic Streptococcus belonging to the Lancefield group C; it is a rare human pathogen, but in horses, it is frequently associated with endometritis. This study aimed to isolate S. zooepidemicus strains, associated with bacterial endometritis in mares, and to define their antimicrobial resistance profile. Twenty-three isolates were recovered from one hundred ninety-six equine uterine swabs (11.7%). Bacterial identification was carried out by Api 20 Strep and confirmed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), while antimicrobial susceptibility testing was performed by disk diffusion method on Muller Hinton agar plates. The antibiotic resistance profiles of the isolates revealed a high percentage of resistance to amikacin (95.6%), ampicillin (73.9%) and tetracycline (69.6%), while ceftiofur and ceftriaxone were highly effective with 82.6% and 78.3% of the isolates inhibited, respectively. An intriguing value of resistance to penicillin (34.8%), which represents the first-choice antibiotic in equine S. zooepidemicus infections, was observed. Furthermore, a high prevalence of multidrug-resistant strains (82.6%) was recorded. Continuous surveillance of this potential zoonotic pathogen and an appropriate antimicrobial stewardship program with the promotion of correct use of antimicrobials, after a proper diagnosis, are needed to allow an effective therapy.

Keywords: Streptococcus equi subsp. zooepidemicus; antibiotic resistance; endometritis; mares.