Invasive ability of different Staphylococcus aureus strains isolated from bovine intramammary infections selected according genotypic profiles and clinical behavior?

SACCO S; RENNA M.S; LOVATO M; BARAVALLE, C; PEREYRA EAL; CALVINHO L.F; DALLARD, B.E

Mar del Plata

Congreso; LXI Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica (SAIC; 2016

The aim of the study was to evaluate the invasion ability in a bovine mammary epithelial cell line (MAC-T) of different Staphylococcus aureus strains isolated from bovine intramammary infections (IMI), selected according genotypic and clinical outcome. Seven S. aureus strains with different genetic virulence profile (ica, bap, agr, blaZ, cap), biofilm production capacity and clinical behavior were used. Three strains (806, 3, 179) were isolated only once from a mammary quarter and not re-isolated in all lactation period (nonpersistent-NP strains). Three strains (5011, 5128, 037) were obtained from the same mammary quarter in three or more consecutive monthly milk samplings over a period of six months (persistent-P strains). All isolates were tested by pulsed field gel electrophoresis showing different pulsotypes. Strain V329 was used as bap-positive and strong biofilm producer. Firstly, MAC-T cells were incubated with two strains subjected to two different growth times (2 h, exponential phase) and (16 h, plateau phase). No differences were observed in the number of intracellular CFU/ml recovered between strains obtained from 2 or 16 h of bacterial growth. The number of intracellular UFC/ml recovered from co-culture with S. aureus strain obtained after 2 h of bacterial growth showed lower standard deviation than those recovered from co-culture obtained after 16 h. Hence, this condition was selected to compared the invasive ability between 7 selected strains. We observed significant differences (p