Transcriptional Portrait of Actinobacillus pleuropneumoniae during Acute Disease - Potential Strategies for Survival and Persistence in the Host

Abstract

BackgroundGene expression profiles of bacteria in their natural hosts can provide novel insight into the host-pathogen interactions and molecular determinants of bacterial infections. In the present study, the transcriptional profile of the porcine lung pathogen Actinobacillus pleuropneumoniae was monitored during the acute phase of infection in its natural host.Methodology/Principal FindingsBacterial expression profiles of A. pleuropneumoniae isolated from lung lesions of 25 infected pigs were compared in samples taken 6, 12, 24 and 48 hours post experimental challenge. Within 6 hours, focal, fibrino hemorrhagic lesions could be observed in the pig lungs, indicating that A. pleuropneumoniae had managed to establish itself successfully in the host. We identified 237 differentially regulated genes likely to encode functions required by the bacteria for colonization and survival in the host. This group was dominated by genes involved in various aspects of energy metabolism, especially anaerobic respiration and carbohydrate metabolism. Remodeling of the bacterial envelope and modifications of posttranslational processing of proteins also appeared to be of importance during early infection. The results suggested that A. pleuropneumoniae is using various strategies to increase its fitness, such as applying Na+ pumps as an alternative way of gaining energy. Furthermore, the transcriptional data provided potential clues as to how A. pleuropneumoniae is able to circumvent host immune factors and survive within the hostile environment of host macrophages. This persistence within macrophages may be related to urease activity, mobilization of various stress responses and active evasion of the host defenses by cell surface sialylation.Conclusions/SignificanceThe data presented here highlight the importance of metabolic adjustments to host conditions as virulence factors of infecting microorganisms and help to provide insight into the mechanisms behind the efficient colonization and persistence of A. pleuropneumoniae during acute disease.

Adhesion Protein ApfA of Actinobacillus pleuropneumoniae Is Required for Pathogenesis and Is a Potential Target for Vaccine Development

“…This result is in accordance with a previous study, which showed that the type IV fimbrial promoter is induced upon contact with host cells via the luxAB reporter system (22). Besides, two recent studies that looked at A. pleuropneumoniae gene expression during natural and experimental infections in pigs also indicated the upregulation of genes coding for type IV fimbriae (36,37).…”

Actinobacillus pleuropneumoniaegenes expression in biofilms cultured under static conditions and in a drip-flow apparatus

“…To identify genes that might be involved in host-pathogen interactions and biofilm formation, transcriptomes from this study were cross-referenced with previous transcriptional study performed by our and other laboratories [19,21,38]. The drip-flow biofilm was the condition that shared the most genes with a natural infection analysis (20 genes; Table 3; [21]) and an experimental infection analysis (13 genes; Table 3; [38]).…”

“…The drip-flow biofilm was the condition that shared the most genes with a natural infection analysis (20 genes; Table 3; [21]) and an experimental infection analysis (13 genes; Table 3; [38]). The 4h-static biofilm and the 6h-static biofilm shared 4 and 14 genes with the natural infection analysis and shared 4 and 8 genes with the experimental infection analysis.…”

A computational strategy for the search of regulatory small RNAs in Actinobacillus pleuropneumoniae

“…We used aerobiosis as it is the typical atmosphere used in experiments involving A. pleuropneumoniae and anaerobiosis as, based on mutant Jacobsen et al 2005;Buettner et al 2009) or transcriptome (Deslandes et al 2010;Klitgaard et al 2012) studies, it is representative of the growth conditions found in necrotic lungs of pigs. As shown in Figure 4 and Table 1, some trans-acting sRNA candidates, like Arrc05 and Arrc08, are located between genes within operons, which could allow them to be mistaken for subproducts of polycistronic mRNA maturation.…”