Haemophilus /hēmof″iləs/ [Gk, haima, blood, philein, to love] , a genus of gram-negative rod-shaped pathogenic bacteria frequently found in the respiratory tract of humans and other animals. Examples are H. influenzae, which causes respiratory tract infections and one form of meningitis; H. haemolyticus, a hemolytic species pathogenic in the upper respiratory tract of humans; and H. ducreyi, which causes chancroid. Haemophilus species are generally sensitive to cephalosporins, tetracyclines, and sulfonamides.
