Mannheimera

Mannheimera is not a recognized genus in current biological nomenclature. It may be a misspelling or confusion with Mannheimia, a bacterial genus in the family Pasteurellaceae.

Mannheimia is a genus of Gram-negative, nonmotile, facultatively anaerobic bacteria within the Pasteurellaceae. The most well-known species is Mannheimia haemolytica, a primary agent of bovine respiratory disease complex (shipping fever) in cattle and a cause of pneumonia in sheep and goats. Other Mannheimia species have been isolated from ruminants and occasionally from other animals. Morphologically, members of the genus are small coccobacilli that can be encapsulated and may require enriched media for growth.

Virulence in Mannheimia haemolytica is driven by factors such as leukotoxins, which target leukocytes, as well as capsules and adhesins that support colonization of the upper respiratory tract and the lungs. Disease typically arises in the context of stress, viral infections, crowding, or transportation, which predispose animals to secondary bacterial invasion and pneumonia. Transmission occurs via respiratory secretions and close contact.

Diagnosis relies on clinical signs, sampling of upper or lower respiratory tract material, culture on appropriate media, and molecular methods such as PCR to identify species and virulence genes. Antimicrobial susceptibility guides treatment, which is complemented by vaccines designed to reduce the incidence and severity of respiratory disease in livestock. Management strategies emphasize vaccination programs, biosecurity, reduced stocking density, and stress minimization to mitigate outbreaks. The genus Mannheimia is primarily of veterinary importance, with limited reports of human infection.