KINETIC AND BEHAVIOR OF STREPTOCOCCUS EQUI SUBSP. ZOOEPIDEMICUS BIOFILM RELATED WITH YEASTS AND ANTIMICROBIAL AGENTS

ETCHECOPAZ ALEJANDRO; BUSTOS CARLA; MUÑOZ ALEJANDRA; IOVANNITTI CRISTINA; GUIDA NORA; MESPLET MARIA

Reikjavik

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

Dorothy Havemeyer Foundation

KINETIC AND BEHAVIOR OF STREPTOCOCCUS EQUI SUBSP. ZOOEPIDEMICUS BIOFILM RELATED WITH YEASTS AND ANTIMICROBIAL AGENTS Alejandro Nazareno Etchecopaz1, Carla Paola Bustos1, Alejandra Jimena Muñoz1, Cristina Adela Iovannitti2, Nora Guida1, María Mesplet11Universidad de Buenos Aires, Facultad de Ciencias Veterinarias, Cátedra de Enfermedades Infecciosas, Ciudad Autónoma de Buenos Aires, Argentina.2Universidad de Buenos Aires, Facultad de Medicina, Centro de Micología, Ciudad Autónoma de Buenos Aires, Argentina.aetchecopaz@fvet.uba.ar Biofilms are structured three-dimensional communities of microorganisms that are enclosed in a protective matrix of polysaccharides and adhered to each other on a biotic or abiotic surface. Biofilm development confers an increased resistance to the host defense system and antibiotics. Infections caused by bacteria that grown in biofilm are frequently chronic, recurrent and resistant to antibacterial therapy. In horses mucous membranes, different microorganisms cohabit and interact each other and with the host. One of these microorganisms, Streptococcus equi subsp. zooepidemicus (S. zooepidemicus), has great veterinary importance. It is isolated from nasopharyngeal and genital mucous membranes of healthy horses and it is also the most frequently isolated pathogen from endometritis in mares. The ability of biofilm production by S. zooepidemicus, may be one of its virulence factors that allow it to persist and became an opportunistic pathogen when the environment change. The aim of this study was to evaluate in vitro kinetics of S. zooepidemicus biofilm, and to compare its behavior in interaction with yeasts and antimicrobials. Biofilm formation of 29 S. zooepidemicus and 30 yeast isolates that were obtained from healthy horses, were studied by colorimetric method at 24, 48 and 72 h. After that, 3 S. zooepidemicus and 3 yeast isolates (Candida glabrata, Candida albicans and Rodhotorula mucilaginosa) with different biofilm kinetics were selected to study their biofilm behavior. S. zooepidemicus and yeast interaction was determined by mixed biofilm formation at different times (24, 48 and 72 h). Penicillin (PEN) effect on planktonic cells of S. zooepidemicus and its biofilm was analyzed by minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Also, PEN and digluconate of chlorhexidine (CHL) effects on mixed biofilm formation were investigated. Variability was observed in quantity and in kinetics of biofilm production between all the different S. zooepidemicus tested. The three S. zooepidemicus isolates shown interaction with yeasts in biofilm development. Regarding the interaction with Candida glabrata and Rhodotorula mucilaginosa, equal or higher biofilm production was observed, while in the mixed biofilm with Candida albicans an equal or lesser biofilm production was presented. PEN MIC on planktonic cells of S. zooepidemicus was the same that PEN MIC on biofilm. Interestly, MBC on biofilm was 65 times higher than MBC on planktonic cells. Different degrees of eradication of individual S. zooepidemicus biofilm formed were observed with addition of PEN and CHL. On the other hand, different degrees of eradication or inhibition of mixed biofilm formed were also identified with addition of PEN and CHL. These studies showed in vitro development of S. zooepidemicus biofilm and its interaction with yeasts that are usually present in the equine mucous. It is important to highlight that the higher antibiotic resistance to PEN in S. zooepidemicus biofilm respect planktonic cells may be related with therapeutic failures and chronic endometritis in mares. On the other hand, both PEN and CHL shown an inhibitory effect on single and mixed formed biofilm suggesting that they should be useful in endometritis treatment. The study of microbial biofilms is complex and even more range of behaviors that may occur in mucous membranes of animals. This work aims to contribute to understand opportunistic infections by S. zooepidemicus and their recurrences that permits the incorporation of new therapeutic strategies.Acknowledgements: This work was supported by Universidad de Buenos Aires (Projects UBACyT 20020150200205BA and 20020130100299BA).