Mannheimia granulomatis

Mannheimia granulomatis is a species of Gram-negative, facultatively anaerobic bacteria in the family Pasteurellaceae. It was originally described as Pasteurella granulomatis in 1990 and reclassified under the genus Mannheimia in 1999 based on DNA–DNA hybridization and 16S rRNA gene sequencing studies.

Morphology and physiology

Mannheimia granulomatis is a non-motile, Gram-negative, rod-shaped bacterium. It is mesophilic, growing optimally at 37 °C, and exhibits facultatively anaerobic metabolism. Colonies are typically 1–2 mm in diameter, smooth, and grayish on blood agar. The bacterium is non-hemolytic on bovine blood agar but hemolytic on sheep blood agar.
Biochemically, M. granulomatis is positive for alkaline phosphatase, beta-galactosidase, and gamma-glutamyltransferase activities. It ferments glucose, fructose, maltose, and sucrose, producing acid, but does not hydrolyze urea or produce indole.

Genomic insights

The genome of the type strain DSM 19156 has been sequenced, revealing a circular chromosome of approximately 2.28 Mbp with a GC-content of 39.2%. The genome encodes over 2,000 protein-coding genes and 82 RNA genes. Genomic analysis indicates the presence of genes associated with central carbohydrate metabolism pathways such as glycolysis, gluconeogenesis, and the pentose phosphate pathway.

Pathogenicity

Mannheimia granulomatis has been isolated from a variety of animal hosts. It was originally linked to granulomatous lesions in cattle and has since been identified in other disease contexts, including subcutaneous abscesses and bronchopneumonia in wild and domestic ruminants.