ATYPICAL STREPTOCOCCUS EQUI SUBSP. EQUI ISOLATES THAT FERMENT LACTOSE AND SORBITOL: ATTENUATION OR INCREASE OF THE VIRULENCE?

BUSTOS CARLA; ETCHECOPAZ ALEJANDRO; DI GENNARO ESTEBAN; PALLAROLS MOLINARI NATALIA; MUÑOZ ALEJANDRA; MESPLET MARIA

Reikjavik

Workshop; Dorothy Havemeyer Foundation Workshop Getting to grips with strangles and other streptococcal diseases; 2019

Dorothy Havemeyer Foundation

Streptococcus equi subsp. equi (S. equi) is usually identified by PCR using different gene targets that encodeM protein (seM), superoxide dismutase (sodA), superantigens H and I (seeH and seeI) or equibactin (eqbGand/or eqbE). Classical phenotypic identification of S. equi includes its classic beta hemolysis and theinability to ferment lactose, trehalose and sorbitol. Nevertheless some S. equi isolates may lose some genesand/or ferment carbohydrates and may be wrongly identified as Streptococcus equi subsp. zooepidemicus(S. zooepidemicus). The aim of this work was to report atypical S. equi isolates that ferment lactose andsorbitol obtained from healthy and sick horses in Argentina. Forty-eight isolates (43 from healthy horses and5 from sick horses) previously identified as S. zooepidemicus by API20 Strep (bioMérieux) were included inthe study. Multiplex and simplex PCR were performed to amplify seM, sodA, seeH and seeI genes1,2. SeMallele types were identified by comparing the nucleotide sequences with the MLST database.A total of 15 isolates were positive for both seM and sodA genes, negative for the seeH gene and variablefor the seeI gene. Twelve of those atypical S. equi isolates were isolated from the nasopharynx of healthyhorses that had recovered from Strangles. These isolates from carriers have presented SeM allele typespreviously described in Argentina (seM 129, 132 and 133). One atypical S. equi was isolated from thesubmandibular lymph node of a foal with mild clinical Strangles that was present as an unique case. Otherisolate was obtained from a bicipital bursitis from a foal without a history of clinical Strangles. Interestingly,the UBA1452-3 isolate was obtained from a pectoral abscess of a horse with bastard Strangles in anoutbreak in Córdoba province. Two typical S. equi isolates (UBA1452-1 and UBA1452-2) that do not fermentlactose and sorbitol and were positive to seM, sodA, seeH and seeI genes were obtained from thesubmandibular lymph nodes of two horses with Strangles in the same outbreak. The most interesting thingis the fact that these three isolates (UBA1452-1, UBA1452-2 and UBA1452-3) presented the same SeM allele(seM 129). Atypical S. equi isolates, which may ferment lactose and/or trehalose, were reported by Grant etal. (1993)3. Recently, Brazilian S. equi isolates that ferment lactose and/or trehalose and/or sorbitol andnegative to seeH and seeI genes were identified from healthy horses4. The loss of genes and the ability touse more carbohydrates may be related with the changes of the bacteria for environment adaptation. Thesechanges may favour the survival of S. equi in the respiratory niche of healthy horses. On the other hand, theisolation of atypical S. equi isolates from atypical localizations such as bicipital bursitis and pectoral abscessmay indicate a greater capacity for invasion of these strains. This is the first report of a Strangles outbreakwith different clinical manifestations associated with two different strains: typical and atypical S. equi. It isimportant to highlight the importance of atypical strains in new presentations of the disease that requires abetter algorithm diagnosis for the differentiation of S. equi and S. zooepidemicus.Acknowledgements:This work was supported by Universidad de Buenos Aires (Projects UBACyT 20020150200205BA and20020130100299BA). We want to thank practitioners and equine farms.