Bovine mastitis is a disease that has a great impact on Brazilian livestock production. Some bacteria described as mastitis-causing agents are not easily cultivable in conventional media, making their diagnosis difficult. The aim of the present study was to detect bacteria present in milk from mastitic and non-mastitic quarters of dairy cattle in Rio de Janeiro-Brazil, using a culture-independent and culture-dependent method. Milk samples were collected from healthy and mastitic quarters. Blood agar medium was used to isolate bacteria. PCR-DGGE (Polymerase Chain Reaction - Denaturing Gradient Gel Electrophoresis) followed by gene sequencing was used to detect bacterial species. Bacteria were isolated from 12 milk samples and Staphylococcus aureus was the only species identified. Bands unique to mastitis were detected in some animals, signaling possible causative agents of the disease in the herd. Species of the genus Streptococcus identified in these samples could not be isolated in culture medium. The present study concluded that the DGGE technique proved to be efficient in detecting bacteria that have difficulty growing in culture medium.

Keywords: Bovine mastitis, Polymerase Chain Reaction, Staphylococcus aureus, Streptococcus