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Research article2023Peer reviewed

Novel Genotype of Streptococcus dysgalactiae subsp. equisimilis Associated with Mastitis in an Arabian Filly: Genomic Approaches and Phenotypic Properties

Bustos, Carla Paola; Retamar, Gabriela; Leiva, Romina; Frosth, Sara; Ivanissevich, Ana; Demarchi, Maria Eugenia; Walsh, Saoirse; Frykberg, Lars; Guss, Bengt; Mesplet, Maria; Waller, Andrew


Streptococcus dysgalactiae subsp. equisimilis (Sde) is a commensal bacterium of horses that causes opportunistic infections. The aim of the work was to study genotypic and phenotypic properties of the Sde strain related to equine neonatal mastitis. Sde was isolated from an 8 day-old filly and sequenced for genome analysis, antibiotic susceptibility tests and virulence factor (VF) assays. The Sde strain presented the novel emmsubtype stC839.12 and the novel multilocus-sequence type ST-670, which belonged to a specific equine genotype group. Although no specific genotypic mechanisms related to antibiotic resistance were found, it presented genes encoding efflux pumps and transporters pmrA, bmrC and lmrP. Genes encoding several putative VFs including emm, cpa, fbp-2, adcA , hyl, htrA , tig, slo, and ndk and loci encoding phosphoenolpyruvate-protein phosphotransferase systems were identified. This is the first report of an equine neonatal mastitis case caused by a novel genotype and horse specific Sde strain.(c) 2023 Elsevier Inc. All rights reserved.


Streptococcus dysgalactiae subsp. equisimilis; Neonatal mastitis; Equine; Genomic

Published in

Journal of Equine Veterinary Science
2023, Volume: 130, article number: 104913