Caracterização fenotípica e genotípica de Streptococcus equi subespécie equi isolados de equinos doentes e portadores no Rio Grande do Sul

• Ano de defesa: 2018
• Autor(a) principal: Tasca, Caiane
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Medicina Veterinária; UFSM; Programa de Pós-Graduação em Medicina Veterinária; Centro de Ciências Rurais
• Palavras-chave em Português: Portadores; Cápsula; Fermentação de açucares; Biofilme; Resistência aos anti-microbianos; Equibactin; Carriers; Capsule; Fermentation of sugars; Biofilm; Antimicrobial resistance; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA
• Link de acesso: http://repositorio.ufsm.br/handle/1/18668

Streptococcus equi subspecies equi (S. equi) is the causative agent of srangles, one of the most frequently diagnosed infectious disease worldwide. After the short duration acute disease, characterized by abscess formation in the head and neck lymph nodes, some horses remain as S. equi carriers for long periods. Equine carriers are the key point for the bacteria maintenance and occurrence of the disease continuously. Therefore, it becomes important to understand what triggers the carrier state, why not all animals can eliminate the bacteria after clinical improvement. This dissertation describes the phenotypic and genotypic characterization of S. equi strains isolated from diseased horses (n = 42) and carriers (n = 18) in the Rio Grande do Sul state. Evaluating colonies’ color and appearance, sugars fermentation tests (ribose, lac-tose, trehalose and sorbitol), capsule visualization, antimicrobial susceptibility test, biofilm formation capacity and detection of virulence factors encoding genes (hasA, hasB, hasC, eqbE, eqbG, seeH and seeI) it was possible to show considerable differences between the two groups of isolates. S. equi isolated from equine carriers presented dry, opaque and white-gray colonies (100%), capsule in small quantity (38.9%) or absent (61.1%), capable of fermenting at least two sugars tested (100%) and resistance on average to 3.6 (1-7) antimicrobials classes. On the other hand, strains isolated from diseased horses had predominantly mucoid and honey color colonies (95.2%), with a large capsule (92.8%), unable to ferment any of the sugars (92.8%) and resistant in mean to 2.1 (0-7) antimicrobials classes. A higher proportion of multiresistant strains was observed in the isolates from carrier animals group (13/18 = 72.2%) compared to the group of isolates from diseased animals (5/42 = 11.9%). Biofilm formation capacity was detected in 94.4% of the isolates from diseased animals and 78.6% from carriers, with no difference between the groups. All the equine carriers’ isolates showed deletion of the eqbE gene and 66.7% of them also in hasA and hasB genes. The loss of these gene loci by isolates from carrier horses had already been reported in another study. Thus, our results complement those of the international literature by associating the genotypic characteristics of the isolates of animal carriers with their phenotypic characteristics, and evidencing differ-ences with those isolated from horses with clinical manifestation. Further studies are needed to elucidate which other events are associated to the persistence of S.equi in the host after clinical cure.