Presented Bernardo Bello-Orti’s PhD thesis: Haemophilus parasuis host-pathogen interactions in the respiratory tract

In the veterinary field, Glässer’s disease is a common disease that leads to considerable economic losses. This disease is caused by the bacterium Haemophilus parasuis. Many studies have focused in understanding the factors involved in disease outcome, but the pathogenesis of this bacterium is not completely understood yet. Different H. parasuis strains exist, ranging from non-virulent to highly virulent. Virulent strains have mechanisms to produce damage in the host, while nonvirulent strains only colonize the upper respiratory tract and are unable to cause disease. It is expected that these different virulence degrees can be appreciated also during the early steps of infection. Using samples from the respiratory tract of piglets infected with two virulent strains and two non-virulent strains, we showed that virulent H. parasuis was able to attach to respiratory tract epithelia, invade and disseminate into the host. Additional details showed that virulent H. parasuis was associated to macrophages and neutrophils in lung, but also to pneumocyte-like cells. On the contrary, non-virulent strains were barely detected in the respiratory tract.

Biofilm-like patterns were displayed by virulent Nagasaki strain in trachea and this made us question the role of biofilm formation in infection. However, our results confirmed that the capacity to form biofilm in vitro was mainly presented by non-virulent strains. Thus, we sequenced the transcriptome and showed that under biofilm conditions H. parasuis showed a low metabolic state. Some of the genes induced under biofilm conditions were specific of non-virulent strains, as the filamentous hemagglutinin fhaB, which has been associated to biofilm formation in other bacteria.

Additionally, the observation of virulent H. parasuis strains in the lung during infection inspired us to sequence the transcriptome of a pathogenic strain in this location. Gene expression showed a reduced metabolism and higher expression of genes involved in nutrient acquisition, which could indicate a survival strategy under these conditions. Genes unique of virulent H. parasuis strains coding for outer membrane proteins were also detected during lung infection. These genes would require further characterization as virulent factors and could be also useful to develop new antimicrobials and vaccines.

 

Virulent H. parasuis (dark brown) in the lung of a pig intranasally inoculated

 

 

Pipeline for the detection of up-regulated genes under biofilm formation

 


Samples used for the analysis of H. parasuis up-regulated genes during lung infection


 

H. parasuis genes induced during lung infection

 

To contact with this thesis director, Dra. Aragon:

Dra. Virginia Aragón
Investigadora de l’IRTA del programa de Sanitat Animal al CReSA
Email: virginia.arargon@irta.cat 
Telèfon: +34 93 581 44 94
Campus UAB, Edifici CReSA s/n,  08193  Bellaterra (Cerdanyola del Vallès) Spain

REF. PROJECT:

Bernardo Bello Ortí studies were funded by a FPI grant from  Ministerio de Economía y Competitividad (MINECO). This work was funded by projects AGL2010-15232 and AGL2013-45662 of the Ministerio de Economía y Competitividad (MINECO).

About IRTA:

IRTA is a research institute devoted to R+D+I in a variety of agri-food areas, such as vegetal production, animal production, food industries, environment and global change, and agri-food economy. The transfer of scientific advances contribute to the modernization, competitiveness and sustainable development of agriculture, food and aquaculture sectors, the supply of healthy and quality foods for consumers and, consequently, improving the welfare of the population. IRTA is assigned to the Departament d’Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural (DAAM, Department of Agriculture) of the Generalitat de Catalunya (Government of Catalonia).

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