In 1897 he developed an agglutination reaction for diagnosis of typhoid fever, which then was called the Grubler-Durham reaction, subsequently known as the Widal reaction; and also created "Durham tubes" for measuring the amount of gas produced in the bacterial colonies, which are still used universally in microbiology laboratories.
Pada tahun 1897 ia mengembangkan reaksi aglutinasi untuk diagnosis demam tifoid, yang kemudian disebut Grubler-Durham reaksi, kemudian dikenal sebagai reaksi Widal; dan juga menciptakan "Durham tabung" untuk mengukur jumlah gas yang diproduksi di koloni bakteri, yang masih digunakan secara universal di laboratorium mikrobiologi.