Capacity of adherence, invasion and intracellular survival of Streptococcus uberis biofilm-forming strains

Abstract

The aim of this study was to examine nine Streptococcus uberis strains, isolated from subclinical mastitis, with different biofilm-forming profiles in relation to their capacity ofadherence and invasion to MAC-T cell lines. In addition, virulence gene were also linked toadherence and invasion.Methods and Results: All S. uberis biofilm-forming strains were able to adhere and invade tothe cells at different levels. UB56 strain, which showed the highest percentage of internalization(3.65%) presented a moderate level of adhesion (4.6 x 106). On the other hand, UB152 was themost adherent strain (8.7 x 106), although it showed a low capacity to internalize (0.65%). Eightstrains were able to persist intracellularly over 96 h regardless of the adherence or invasionlevel. One strain (UB27) was not table to survive. Statistical analysis between biofilm-forming ability and the adhesion capacity of the strains showed no statistically significant differences.Presence of virulence genes involved in adhesion process (gapC, hasABC, lbp, pauA and sua)assayed by PCR showed that the strains harbored different genes and six different patterns canbe observed.Conclusion: Statistical analysis showed no correlation between the virulence gene patterns andthe adhesion capacity or the percentage of internalization. Results showed that biofilm-forming ability did not influence the invasion capacity. Likewise, adherence and invasion capacity maybe strain dependent.Significance and Impact of the Study: The findings from this study provides new insights on biofilm and invasion capacity of S. uberis strains isolated from subclinical infections. Results could help to the design of adequate control strategies.