Draft Genome Sequence of the Bordetella bronchiseptica Swine Isolate KM22

Complete Genome Sequence of Bordetella bronchiseptica Strain KM22

Bordetella bronchiseptica isolate KM22 has been used in experimental infections of swine as a model of clinical B. bronchiseptica infection and to study host-to-host transmission. The draft genome sequence of KM22 was reported in 2014. Here, we report the complete genome sequence of KM22.

Bordetella bronchiseptica isolate KM22 has been used in experimental infections of swine as a model of clinical B. bronchiseptica infection and to study host-to-host transmission. The draft genome sequence of KM22 was reported in 2014. Here, we report the complete genome sequence of KM22.

The Bordetella Bps Polysaccharide Is Required for Biofilm Formation and Enhances Survival in the Lower Respiratory Tract of Swine

Bordetella bronchiseptica is pervasive in swine populations and plays multiple roles in respiratory disease. Additionally, B. bronchiseptica is capable of establishing long-term or chronic infections in swine. Bacterial biofilms are increasingly recognized as important contributors to chronic bacterial infections. Recently the polysaccharide locus bpsABCD has been demonstrated to serve a critical role in the development of mature biofilms formed by the sequenced laboratory strain of B. bronchiseptica We hypothesized that swine isolates would also have the ability to form mature biofilms and the bpsABCD locus would serve a key role in this process. A mutant containing an in-frame deletion of the bpsABCD structural genes was constructed in a wild-type swine isolate and found to be negative for poly-N-acetylglucosamine (PNAG)-like material by immunoblot assay. Further, the bpsABCD locus was found to be required for the development and maintenance of the three-dimensional structures under continuous-flow conditions. To investigate the contribution of the bpsABCD locus to the pathogenesis of B. bronchiseptica in swine, the KM22Δbps mutant was compared to the wild-type swine isolate for the ability to colonize and cause disease in pigs. The bpsABCD locus was found to not be required for persistence in the upper respiratory tract of swine. Additionally, the bpsABCD locus did not affect the development of anti-Bordetella humoral immunity, did not contribute to disease severity, and did not mediate protection from complement-mediated killing. However, the bpsABCD locus was found to enhance survival in the lower respiratory tract of swine.

Acquisition and loss of virulence-associated factors during genome evolution and speciation in three clades of Bordetella species

Background

The genus Bordetella consists of nine species that include important respiratory pathogens such as the ‘classical’ species B. bronchiseptica, B. pertussis and B. parapertussis and six more distantly related and less extensively studied species. Here we analyze sequence diversity and gene content of 128 genome sequences from all nine species with focus on the evolution of virulence-associated factors.

Results

Both genome-wide sequence-based and gene content-based phylogenetic trees divide the genus into three species clades. The phylogenies are congruent between species suggesting genus-wide co-evolution of sequence diversity and gene content, but less correlated within species, mainly because of strain-specific presence of many different prophages. We compared the genomes with focus on virulence-associated genes and identified multiple clade-specific, species-specific and strain-specific events of gene acquisition and gene loss, including genes encoding O-antigens, protein secretion systems and bacterial toxins. Gene loss was more frequent than gene gain throughout the evolution, and loss of hundreds of genes was associated with the origin of several species, including the recently evolved human-restricted B. pertussis and B. holmesii, B. parapertussis and the avian pathogen B. avium.

Conclusions

Acquisition and loss of multiple genes drive the evolution and speciation in the genus Bordetella, including large scale gene loss associated with the origin of several species. Recent loss and functional inactivation of genes, including those encoding pertussis vaccine components and bacterial toxins, in individual strains emphasize ongoing evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3112-5) contains supplementary material, which is available to authorized users.

Cilia-associated bacteria in fatal Bordetella bronchiseptica pneumonia of dogs and cats

Bordetella bronchiseptica frequently causes nonfatal tracheobronchitis, but its role in fatal pneumonia is less recognized. Our study evaluated histologic identification of cilia-associated bacteria as a method for diagnosis of B. bronchiseptica pneumonia. Cases of fatal bronchopneumonia were studied retrospectively, excluding neonates and cases of aspiration pneumonia, minor lung lesions, or autolysis. The study population comprised 36 canine and 31 feline cases of bronchopneumonia. B. bronchiseptica was identified in 8 of 36 canine and 14 of 31 feline cases based on immunohistochemistry (IHC) using serum from a rabbit hyperimmunized with pertactin, PCR testing (Fla2/Fla12), and/or bacterial culture data when available. Of these, IHC was positive in 4 canine and 7 feline cases, PCR was positive in 8 canine and 14 feline cases, and B. bronchiseptica was isolated in 2 of 5 canine and 3 of 9 feline cases tested. Examination of histologic sections stained with hematoxylin and eosin revealed bronchial cilia-associated bacteria in 4 of 36 canine and 5 of 31 feline cases; these were all positive by IHC and PCR. The presence of cilia-associated bacteria had been noted in the pathology report for only 2 of these 9 cases. Thus, the presence of cilia-associated bacteria seems frequently overlooked by pathologists, but is a diagnostically significant feature of B. bronchiseptica pneumonia. A specific diagnosis of B. bronchiseptica pneumonia is important because it suggests primary or opportunistic bacterial pneumonia rather than aspiration pneumonia, and because of the risk of animal-to-animal transmission of B. bronchiseptica, the availability of vaccines for disease prevention, and the potential zoonotic risk to immunocompromised pet owners.

Comparative genomic analysis of the swine pathogen Bordetella bronchisepticastrain KM22

The well-characterized Bordetella bronchiseptica strain KM22, originally isolated from a pig with atrophic rhinitis, has been used to develop a reproducible swine respiratory disease model. The goal of this study was to identify genetic features unique to KM22 by comparing the genome sequence of KM22 to the laboratory reference strain RB50. To gain a broader perspective of the genetic relationship of KM22 among other B. bronchiseptica strains, selected genes of KM22 were then compared to five other B. bronchiseptica strains isolated from different hosts. Overall, the KM22 genome sequence is more similar to the genome sequences of the strains isolated from animals than the strains isolated from humans. The majority of virulence gene expression in Bordetella is positively regulated by the two-component sensory transduction system BvgAS. bopN, bvgA, fimB, and fimC were the most highly conserved BvgAS-regulated genes present in all seven strains analyzed. In contrast, the BvgAS-regulated genes present in all seven strains with the highest sequence divergence werefimN, fim2, fhaL, andfhaS. A total of eight major fimbrial subunit genes were identified in KM22. Quantitative real-time PCR data demonstrated that seven of the eight fimbrial subunit genes identified in KM22 are expressed and regulated by BvgAS. The annotation of the KM22 genome sequence, coupled with the comparative genomic analyses reported in this study, can be used to facilitate the development of vaccines with improved efficacy towards B. bronchiseptica in swine to decrease the prevalence and disease burden caused by this pathogen.