Shortly thereafter, the outbreak of meningococcus arrived in California from China. Because of this, Branham's career shifted paths, and she began working for what is now the National Institutes of Health (NIH) (then, known as the Hygienic Laboratory of the United States Public Health Service) in Bethesda, Maryland as a senior bacteriologist, in order to study meningococcus. Branham stayed at the NIH for the rest of her career. She remained in the role for over 25 years until she was promoted to the Chief of Bacterial Toxins of the Division of Biological Standards in 1955. Branham married retired businessman Philip S. Matthews in 1945. Matthews died four years later. Branham retired from the NIH in 1958 at the age of seventy from the position of Chief of the Section on Bacterial Toxins, and died November 16, 1962 after a sudden heart attack. She is buried in Oxford, Georgia in her family's plot. Broadly, Sara Branham's research was based in the field of infectious diseases, including influenza, salmonella, shigella, diphtheria, dysentery, and psittacosis. She studied the toxins produced by Shigella dysenteriae. The main focus of Branham's work at the NIH, however, was meningitis. This focus was Branham responding to what was quickly becoming a health crisis: an untreatable form of meningitis had arrived in the United States and began spreading quickly. She is credited with the discovery and isolation of "Neisseria meningitidis". Neisseria is a common causative organism of meningitis, and its taxonomy is well characterized by Branham throughout her work. She also discovered that the infection could be treated with sulfa drugs rather than antiserums that were used at the time, but that were ineffective in treating this strain. Branham was considered an international expert on the strain of disease: due to her great contributions to the knowledge about it, Neisseria catarrhalis was renamed Branhamella caterrhalis in 1970, years after Branham's death. The new name was officially accepted in the 1974 edition of Bergey's Manual of Systematic Bacteriology. Branham's studies in infectious disease were nationally known, and she came to be considered as one of the "grand ladies of microbiology". In a biographical article about Branham published in the Atlanta Constitution, the huge impact of her work was summarized in the exclamation: "She killed millions of killers!"