An ST11 clone of Pasteurella multocida, widely spread among farmed rabbits in the Iberian Peninsula, demonstrates respiratory niche association

- Pasteurella multocida causes respiratory diseases in all livestock.
- In rabbits, P. multocida causes a variety of clinical conditions (pasteurellosis).
- Field rabbit isolates are heterogeneous in capsule and virulence-associated genes.
- An ST11 clone, capD, is significantly associated with pneumonia in rabbit farms.
- The ST11 clone is widespread among rabbit farms in the Iberian Peninsula.

Pasteurella multocida is a veterinary pathogen causing diseases with considerable economic repercussions in a wide range of animal hosts. In rabbits, P. multocida infections cause a variety of clinical manifestations including rhinitis, pneumonia, septicemia, abscesses, mastitis, and pyometra. In this study, 100 P. multocida isolates from different commercial rabbit farms located throughout the Iberian Peninsula were molecularly characterized by capsular typing, detection of four virulence-associated genes (tbpA, toxA, hgbB, and pfhA), and multilocus sequence typing (MLST). Rabbit P. multocida isolates belonged to three different capsular types: A (47.0%), D (28.0%), and F (25.0%). One group of P. multocida isolates of capsular type D and positive for the hgbB gene was significantly associated with the clinical presentation of respiratory disease (OR 5.91; 95%CI, 1.63-21.38). These isolates belonged to same sequence type, ST11, in the P. multocida Multi-host MLST database. The ST11 clone also includes isolates from porcine and avian pneumonia. This clonal group of epidemiologically unrelated P. multocida isolates could be a virulent clone with some degree of specificity for respiratory disease. These findings could be relevant in the development of vaccines for pasteurellosis prevention, especially respiratory disease.