Distinct phenotypic traits of Staphylococcus aureus are associated with persistent, contagious bovine intramammary infections

GRUNERT, T; STESSL B; WOLF F; SORDELLI DO; BUZZOLA FR; EHLING-SCHULZ M

Scientific Reports

Nature Research

Año: 2018

Staphylococcus aureus causing persistent, recurrent bovine intramammary infections are still a majorchallenge to dairy farming. Generally, one or a few clonal lineages are predominant in dairy herds,indicating animal-to-animal transfers and the existence of distinct pathotypic traits. The aim of thisstudy was to determine if long term persistence and spreading of S. aureus are associated with specificphenotypic traits, including cellular invasion, cytotoxicity and biofilm formation. Mastitis isolateswere collected over a 3-years period from a single dairy herd, resulting in two persistent subtypes, thehigh within-herd prevalent subtype ST9 (CC9)-methicillin-susceptible S. aureus (MSSA), designatedHP/ST9, and the low within-herd prevalent subtype ST504 (CC705)-MSSA, designated LP/ST504.Characterization of the two different coexisting persistent subtypes showed that the followingphenotypic traits are particularly associated with high within-herd prevalence: lack of capsularpolysaccharide expression, high cellular invasiveness, low cytotoxicity and high biofilm/ poly-Nacetylglucosamine(PNAG) production, which may concomitantly contribute to the spreading of HP/ST9 within the herd. By contrast to HP/ST9, LP/ST504 is characterized by the formation of colonydendrites, which may help the bacteria to access deeper tissues as niches for persistence in singleanimals. Thus, within a single herd, two different types of persistence can be found in parallel, allowinglongtime persistence of S. aureus in dairy cattle. Furthermore, this study indicates that ST9 (CC9)-MSSAstrains, which are currently thought to have their primary reservoir in swine and humans, can alsosuccessfully spread to new hosts and persist in dairy herds for years.