A researcher from the University of Zaragoza discovers the genes that cause meningitis in pigs

• Jesús Arenas, member of the Agri-Food Institute of Aragon (IA2), lays the foundations for the treatment without antibiotics of the pathogen Streptococcus suis
• The journal Virulence publishes the identification of 361 genes essential to causing the infection and their study will allow the creation of a new vaccine
• The pig sector in Spain produces 30 million pigs per year and creates 300.000 direct and one million indirect jobs.

Jesús Arenas, professor at the University of Zaragoza and researcher at the Aragon Agri-Food Institute (IA2) - UNIZAR-CITA joint centre, has discovered the essential genes used by the pathogen Streptococcus suis to cause meningitis and sepsis in pigs. Specifically, he has identified 361 genes essential to causing infection and their study will allow the creation of a new vaccine.

This work, published by the journal Virulence, has special relevance since the pork industry is of great economic importance in Spain; Our country produces around 30 million pigs a year and creates 300.000 direct and one million indirect jobs, which represents 14% of all agricultural and livestock production in Spain. At an international level, in the last five years, Spain has established itself as the first pork producer in the European Union and the third in the world.

This research has been developed at the Wageningen BioVeterinary Research institute (part of Wageningen University, Netherlands) with collaborations from the University of Nijmegen (Netherlands), and has been completed at the University of Zaragoza. It has received funding from the European PIGSs project, in which the molecular microbiologist Jesús Arenas has also led a working group.

Streptococcus suis is a pathogen that causes meningitis, pneumonia and sepsis in young pigs, usually leading to death. Their infections cause economic losses estimated at 200.000 billion a year globally. There are no effective vaccines to prevent infection, although bacterins are used, but these are limited to a certain farm and a certain strain.

Treatment with antibiotics is the most used to prevent and treat infections caused by this pathogen. Its use is extreme; On some farms, about 50% of antibiotics are used to treat infections caused by S. suis. However, the development of numerous antibiotic resistances and social pressure to reduce their use is demanding new alternatives to prevent or more effectively treat S. suis.

Arenas' work is aimed at addressing this problem. She has started from the hypothesis that those structures that the pathogen strictly needs to cause infection will be good candidates for generating new therapies or vaccines. Blocking these structures will prevent the development of infection. This bacteria lives in the environment and also as a commensal, therefore a large part of its genes are dedicated to functions unrelated to its pathogenicity.

The first step has been to know the set of genes that are really involved in the development of the disease and to obtain a wide range to obtain more possibilities. For this, a combination of techniques has been used. On the one hand, a large number of genes have been inactivated in S. suis. In total, about 97% of the bacteria's genome has been inactivated. Pigs have been experimentally infected with these mutants using a new specific infection protocol to cause meningitis, and it has been identified which mutants die during infection using advanced massive sequencing techniques and bioinformatic analysis.

The result has been the identification of 361 genes (about 18% of the genome) that are essential to cause infection and that are involved in a variety of biological processes. Some of them had not been studied before, and studies have been initiated to evaluate their function and their suitability for the creation of a new vaccine. This study not only advances knowledge about how S. suis causes the infection and attempts to prevent it, but could also be useful to understand the homologous pathogen in humans, Streptococcus pneumoniae, for which a more effective vaccine is also being sought.