A microbiologist carries out milk ring test, which is positive. What is the most likely organism?

Milk Ring Test (M) is positive for Brucella. It is used for detection of infected animals in dairy farms, etc. A sample of whole milk is mixed with a drop of Brucella antigen and incubated at 70 degC for 40-50 min. If antibodies are present in the milk the bacilli are agglutinated and rise with the cream to form a blue ring at the top, leaving the milk unstained (M positive). If antibodies are absent, the milk remains uniformly blue (M negative) Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition