General information
Mannheimia haemolytica is a gram-negative, facultative anaerobic bacillus of the genus Mannheimia and the family Pasteurellaceae. It is considered the primary causative agent of enzootic bronchopneumonia in cattle and sheep and, moreover, the pathogen of severe mastitis as well as septicaemia in sheep and goats. In ruminants, however, some of the serotypes described for M. haemolytica are part of the natural microflora of the upper respiratory tract.