Actinobacillus pleuropneumoniae is the etiologic agent of porcine contagious pleuropneumonia, a cause of considerable world wide economic losses in the swine industry. We sequenced the complete genome of A. pleuropneumoniae, JL03, an isolate of serotype 3 prevalent in China. Its genome is a single chromosome of 2,242,062 base pairs containing 2,097 predicted protein-coding sequences, six ribosomal rRNA operons, and 63 tRNA genes. Preliminary analysis of the genomic sequence and the functions of the encoded proteins not only confirmed the present physiological and pathological knowledge but also offered new insights into the metabolic and virulence characteristics of this important pathogen. We identified a full spectrum of genes related to its characteristic chemoheterotrophic catabolism of fermentation and respiration with an incomplete TCA system for anabolism. In addition to confirming the lack of ApxI toxin, identification of a nonsense mutation in apxIVA and a 5′-proximal truncation of the flp operon deleting both its promoter and the flp1flp2tadV genes have provided convincing scenarios for the low virulence property of JL03. Comparative genomic analysis using the available sequences of other serotypes, probable strain (serotype)-specific genomic islands related to capsular polysaccharides and lipopolysaccharide O-antigen biosyntheses were identified in JL03, which provides a foundation for future research into the mechanisms of serotypic diversity of A. pleuropneumoniae.

Haemophilus parasuis is the aetiological agent of Glässer's disease, which has received more attention in the past decade due to the increasing economic losses in the pig industry worldwide. Little is known about the mechanisms by which H. parasuis survives in the host. In this study, selective capture of transcribed sequences (SCOTS) was used to identify H. parasuis genes upregulated in necrotic porcine lung 7 days post infection. Thirty-eight genes were identified that were upregulated during infection of the lung tissue of pigs, compared with growth in culture medium. In two examples chosen gene expression was not confined to the lungs, there being variation between tissues. The data support biofilm formation being an important mode of growth for colonization and/or persistence. Results from the in vitro studies suggest that, as for other pathogens, iron and oxygen restriction and heat stress are important environmental signals to regulate gene expression. This study has identified genes of H. parasuis that are upregulated during infection of porcine lung tissue as compared with in vitro growth conditions.

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