Abstract:

Luego de adherirse, las bacterias pueden desarrollarse en forma de biofilm, es decir, una comunidad de células bacterianas adheridas y envueltas en una matriz extracelular producida por ellas mismas. Streptococcus equi subsp. equi (S equi) es una bacteria adaptada al equino que produce la Adenitis equina, y que puede permanecer en nasofaringe y bolsas guturales de animales recuperados que actúan como portadores y fuentes de infección. Se ha propuesto por diversos investigadores la producción de biofilm bacteriano como modelo de infecciones crónicas y de portadores asintomáticos en humanos y animales. Por lo tanto, el objetivo de este trabajo fue evaluar la capacidad productora de biofilm de S equi. Se trabajó con 84 aislamientos de S equi utilizando el método colorimétrico de la microplaca y el del portaobjetos observando microscópicamente la presencia de polisacárido extracelular (PSE) y la formación de aglomerados celulares. En el método colorimétrico, se obtuvieron valores homogéneos a las 18 h de incubación sin encontrarse diferencias con los distintos medios testeados (p valor >0.05). La mayor producción fue a las 36 h de incubación, alcanzándose los valores más altos en presencia de plasma equino (p valor <0.05). El 66% de los aislamientos presentó PSE, sin observarse diferencias entre los aislamientos de enfermos y de portadores. Se encontró asociación entre la formación de aglomerados celulares y producción de PSE (p valor <0.05). Se logró demostrar por primera vez la capacidad de S equi para producir biofilm, observándose la formación de una sustancia compatible con el PSE que podría favorecer la permanencia de la bacteria en los caballos portadores. Además, algún componente plasmático del equino sería estimulante de la formación de biofilm como se ha observado en Streptococcus zooepidemicus. Se propone profundizar en el estudio del biofilm para contribuir al conocimiento del comportamiento de S equi en los portadores.

After attached, bacteria can grow in biofilms as a community of cells surrounded by an extracellular matrix synthesized by themselves. Streptococcus equi subsp. equi (S. equi) is a microorganism that produces strangles in horses. It can remain in nasopharynx and guttural pouches of recovered animals, situation that plays an important role in the dissemination of the infection. Some researchers have proposed the production of bacterial biofilm as a model of chronical infection and asymptomatic carriers in animals and human beings. The aim of this work was evaluate the capacity of biofilm production of S. equi. Eighty-four isolates of S. equi were studied by colorimetric and glass slides methods showing the presence of extracellular polysaccharide (PSE) and cell agglomerates. Values were obtained by a colorimetric method at 18 h of incubation and no difference was found with different culture media (p>0.05). The biggest production of biofilm was obtained at 36 h of incubation with highest values in the presence of equine plasma (p<0.05). Sixty-six percent of isolates showed PSE and no difference was observed between isolates of carriers and sick animals. There was a significant correlation between agglomerate and PSE formation (p<0.05). This is the first report of the capacity of biofilm production of S. equi and the presence of a substance compatible with extracellular polysaccharide which may favor the persistence of bacteria in carrier horses. Furthermore, some plasmatic component may be facilitating the formation of biofilm as it was previously observed for Streptococcus zooepidemicus. Further assays are needed to study this virulence factor to understand the behavior of S. equi in carrier horses.

Author affiliation: Bustos, Carla Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Marfil, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Lanza, Natalia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Guida, Nora. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Abstract:

Strangles is one of the most frequently diagnosed equine respiratory infectious diseases in the world. It is caused by Streptococcus equi subsp. equi (S. equi), and it is an acute infection characterized by pyrexia, nasal discharge, pharyngitis, and abscessation of lymph nodes. Frequently, healthy horses might continue to harbor S. equi after clinical recovery. Although the genetic distance between S. equi isolates is short, strains can be differentiated by pulsed-field gel electrophoresis (PFGE) and single locus sequence typing for epidemiological studies. The aim of this study was to characterize by PFGE Argentine isolates of S. equi obtained from horses with acute strangles and those that had recovered. Bacterial isolation and identification of 80 S. equi isolates by phenotypic and genotypic tests were performed using samples from 29 horses with acute strangles and 95 from healthy animals. Also, the isolates were characterized by PFGE using Bsp120I and SmaI. Visual comparison of macrorestriction patterns generated with both enzymes revealed three different DNA fragment profiles with variations of one or two bands. Interestingly, an identical profile was found in isolates from the same horse and from horses that were infected at the same time, and the horses recovered from strangles continue to carry the same strain. Some vaccinated horses have been mild infected for a different strain from that of carriers suggesting other source of infection. This is the first molecular characterization of Argentine isolates of S. equi, which shows the presence of three strains between 2010 and 2013 in Buenos Aires.

Author affiliation: Bustos, Carla Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Guida, Nora. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Casamayor, Almudena. Universidad Complutense de Madrid; España

Author affiliation: Muñoz, Alejandra Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Fernández Garayzábal, José Francisco. Universidad Complutense de Madrid; España

Author affiliation: Vela Alonso, Ana Isabel. Universidad Complutense de Madrid; España