Staphylococcus aureus host adaptive changes during progression of chronic bovine mastitis.

GRUNERT T; DEUTSCH M; BUZZOLA FR; SORDELLI DO; EHLING-SCHULZ M

Conferencia; Staphylococcal Diseases. Gordon Research Conference; 2015

Staphylococcus aureus host adaptive changes during progression of chronic bovine mastitis Tom Grunert1, Monika Deutsch1, Fernanda Buzzola2, Daniel O. Sordelli2 and Monika Ehling-Schulz1 1Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine, Veterinärplatz 1, 1210, Vienna, Austria; 2Instituto de Microbiologia, Parasitologia e Inmunologia, Facultad de Medicina, Universidad de Buenos Aires and CONICE Staphylococcus aureus frequently causes subclinical and persistent intramammary infections (IMI) in dairy cattle. This type of infection is difficult to treat with antibiotics and prone to resurgence. Several studies of persistent IMI suggest that S. aureus adaptation to the udder environment results in the emergence of one predominant clone in a herd. However, the unique properties of these persistent S. aureus strains to make them particularly fit to survive in the bovine mammary gland still need to be elucidated. In this project we study the host adaptive mechanisms of S. aureus during progression of chronic bovine mastitis. During three months weekly monitoring of a naturally infected dairy cattle we were able to follow such a transition towards a S. aureus host adapted phenotype using metabolic fingerprinting by Fourier-transform infrared (FTIR) spectroscopy. Clinical data indicate an exclusive selective pressure through the host immune response on the bacteria, because no antibiotic therapy was given during this period, which finally resulted in the complete replacement of the initial phenotype. Clonality was proven using multilocus sequence typing and pulsed-field gel electrophoresis. The persistence potential of the initial and hostadapted isolate was investigated in vitro by means of biofilm production, adhesion to fibronectin, capsule polysaccharide (CP) expression and protease activity. A comparative exoproteome analysis was performed using 2Ddifferential gel electrophoresis followed by MALDI-TOF mass spectrometry. Preliminary data from a comparison between the initial and host-adapted isolate revealed that host adaptation causes reduced CP expression, increased adherence and biofilm formation. Moreover, the analysis of the exoproteome shows an altered proteolytic cascade of Aur, SspA and SspB resulting in increased enzymatic activity for SspA in the host-adapted isolate, assuming that an increased bacterial proteolysis might play an important role in chronicity. In summary, FTIR spectroscopy was used to follow S. aureus host adaptation and resulted in a unique collection of host-adapted prototype strains. The host-adapted isolate exhibits typical phenotypic features linked to bacterial chronicity and thus we hypothesize a general trend of the adaptation process towards less virulence.