Characterisation of Streptococcus uberis from bovine milk

Abstract: Salem Abureema

The goal of this thesis was to investigate three main aspects of mastitis due to Streptococcus uberis; (i) the epidemiology of clinical bovine mastitis, including the relative importance of cow-to-cow transmission and acquisition from an environmental source as well as the occurrence of persistent infection and re-infection, (ii) factors affecting biofilm formation of S. uberis, and (iii) the virulence factors of S. uberis.

Two hundred and twelve Streptococcus uberis isolates were obtained from clinical cases of mastitis in dairy cattle from different farms in Gippsland, Victoria, Australia. Approximately 28% (n = 60) of the isolates were from recurrent infections. Among these 60, S. uberis isolates from 27 cows, with 34 different DNA restriction patterns were observed, indicating a wide variety of S. uberis strains causing clinical mastitis. Most recurrences (n = 20) were due to a new strain, indicating that treatment of the initial infection was usually successful. There were five examples of the same strain being isolated from different cows on the same farm, suggesting either cow-to-cow transmission at milking or acquisition from a common environmental source.