Pasteurella multocida: from zoonosis to cellular microbiology

Abstract

In a world where most emerging and reemerging infectious diseases are zoonotic in nature and our contacts with both domestic and wild animals abound, there is growing awareness of the potential for human acquisition of animal diseases. Like other Pasteurellaceae, Pasteurella species are highly prevalent among animal populations, where they are often found as part of the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts. Many Pasteurella species are opportunistic pathogens that can cause endemic disease and are associated increasingly with epizootic outbreaks. Zoonotic transmission to humans usually occurs through animal bites or contact with nasal secretions, with P. multocida being the most prevalent isolate observed in human infections. Here we review recent comparative genomics and molecular pathogenesis studies that have advanced our understanding of the multiple virulence mechanisms employed by Pasteurella species to establish acute and chronic infections. We also summarize efforts being explored to enhance our ability to rapidly and accurately identify and distinguish among clinical isolates and to control pasteurellosis by improved development of new vaccines and treatment regimens.

Fig 1

Pasteurellosis deaths in the United States, 1993 to 2006. Data are based on CDC general mortality tables (http://www.cdc.gov/nchs/nvss/mortality_tables.htm).

Fig 2

Phylogenetic relationships of Pasteurella multocida and related Pasteurellaceae bacteria based on 16S rRNA genes. The maximum-likelihood phylogenetic tree was calculated by using MEGA5 (575), based on full-length 16S rRNA gene sequences. Nodes with bootstrap values of greater than 30% after 1,000 replicates are indicated.

Fig 3

Phylogenetic comparison among selected Pasteurella multocida and Haemophilus influenzae species with completed genome sequences. (A) Phylogenetic relationships among the strains based on 16S rRNA genes. The maximum-likelihood tree was calculated by using MEGA5 (575), based on the 16S rRNA genes from each of the indicated strains of P. multocida (Pm) or H. influenzae (Hi) with complete genome sequences. Nodes with bootstrap values of greater than 30% after 1,000 replicates are indicated. (B) Genome-wide comparison based on the fractions of common genes among the strains. The neighbor-joining tree was calculated by using MEGA5 with distances derived from the fraction of genes that are common between each pair of genomes and have >90% coverage in BLASTN alignment. (C) Genome-wide comparison based on the similarity among the common genes among the strains. The neighbor-joining tree was calculated by using MEGA5 with distances derived from the average BLASTN identity for common genes with >90% coverage in alignment.

Fig 4

Phylogenetic comparison of the capsule biosynthesis (cap) gene locus among selected Pasteurella multocida strains. The maximum-likelihood tree was calculated by using MEGA5 (575) with distances derived from genes within the cap locus of P. multocida serotypes B:2 (strain M1404), A:1 (strain X73), A:3 (strain P1590), and D (strain HN06), as well as the cap loci from serotype A strains 3480 and 36950.

Fig 5

Atrophic rhinitis in swine. Shown are transverse sections of the nasal cavities of pigs exhibiting pathological symptoms of atrophic rhinitis ranging from mild (left panel) to moderate (middle panel) to severe (right panel) caused by infection with toxinogenic P. multocida. (Photos courtesy of the University of Illinois Veterinary Diagnostics Laboratory, Urbana, IL; reproduced with permission.)

Fig 6

Bovine pasteurellosis bronchopneumonia lung. Shown is an image of a lung lobe from a calf exhibiting pathological symptoms of bronchopneumonia, including extensive hemorrhagic lesions (dark areas), caused by infection with P. multocida. (Courtesy of Peter G. Moisan, Veterinary Diagnostic Laboratory, Kansas State University; reproduced with permission.)