Molecular typing of Streptococcus uberis strains isolated from cases of bovine mastitis

The discriminatory power of two polymerase chain reaction-based DNA fingerprinting methods, random amplified polymorphic DNA and repetitive extragenic palindrome were compared by subtyping 128 isolates of Streptococcus uberis cultured from cows in six different dairy herds in New Zealand. The typing results demonstrated that the majority of isolates possessed unique fingerprint profiles except on occasions where multiple isolates were obtained from individual cows. On these occasions, individual quarters of the mammary gland were generally, but not exclusively, infected by the same strain of bacteria. Both random amplified polymorphic DNA and repetitive extragenic palindromic typing assays were simple to perform, relatively inexpensive ($11.00 per reaction), and provided reliable and reproducible results. Furthermore, when these assays were used in conjunction with each other, they provided a means of confirmation of the specific DNA fingerprint patterns obtained.