A microbiologist carries out milk ring test, which is positive. What is the most likely organism?: (A) Salmonella, (B) Brucella, (C) Bordetella, (D) Bacillus anthracis
Answer is B. 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