bronchiseptica cluster [10]. Complex I strains are most commonly isolated from non-human mammalian hosts, whereas the majority of complex IV strains were from humans, many with pertussis-like

symptoms. Complex IV strains were found to exclusively share IS1663 with B. pertussis, suggesting a close evolutionary relationship among check details these lineages. Complex IV strains and B. pertussis are proposed to share a common ancestor, although the genes encoding pertussis toxin (ptxA-E) and the ptl transport locus were found to be missing in the majority of complex IV strains that were sampled [10]. Additionally, several other B. pertussis virulence genes were also found to be absent or highly divergent, including those encoding dermonecrotic toxin, tracheal colonization factor, pertactin, and the lipopolysaccharide biosynthesis locus. Differences between virulence determinants expressed by B. pertussis and complex IV strains have been suggested to be driven by immune find more competition in human hosts [10], a model also proposed for differences observed between B. pertussis and B. parapertussis hu [17]. Given their apparent predilection of complex IV B. bronchiseptica isolates for human infectivity, we have initiated a systematic analysis of their virulence properties and mechanisms. We found that complex IV strains, on average, display significantly elevated levels of cytotoxicity in comparison to complex I isolates. Several MK5108 purchase complex IV strains

are also hyperlethal in mice, and hyperlethality in vivo as well as cytotoxicity in vitro is dependent on the BteA T3SS effector protein [11, 12]. Comparative whole-genome sequence analysis of four complex IV isolates was used to identify similarities and differences between B. bronchiseptica lineages. Results from genome comparisons did not identify significant genomic regions that are unique to complex IV strains but missing from complex I isolates. This implies that complex IV-specific phenotypes are determined by polymorphisms in conserved genes, differential regulation [18], or other epigenetic mechanisms rather than acquisition or retention of unique genomic determinants. Methods Bacterial strains

and growth conditions Strains and plasmids used Aspartate in this study are listed in Table 1. Bacteria were grown in Stainer-Scholte liquid (SS) medium at 37°C [19] or on Bordet–Gengou (BG) agar (Becton Dickinson Microbiology systems) supplemented with defibrinated sheep blood at a concentration of 7.5% and incubated at 37°C. RB50 [20] was grown from archived, low passage, frozen glycerol stock. Antibiotics were added to the following final concentrations: ampicillin (Ap), 100 μg/ml; chloramphenicol (Cm), 25 μg/ml; Streptomycin (Sm), 20 μg/ml; Kanamycin (km), 50 μg/ml; Gentamycin (Gm), 20 μg/ml. Table 1 Bacterial strains, mammalian cells and plasmids used in this study Bacterial strains or plasmids Alternate name Source Genotype or relevant characteristics Reference E.