John Elmerdahl Olsen

John Elmerdahl Olsen


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    John Elmerdahl Olsen is a veterinarian by training, and he has specialized in clinical and molecular microbiology. He is head of the research group "Molecular Veterinary Bacteriology". Here he works in a team consisting of himself, three Associate Professors (Line Elnif Thomsen, Henrik Christensen and Arshnee Moodley), and a varying number of Post Doc fellows, PhD students, Graduate Students and one Technician. The research focuses on prevention of bacterial diseases and antimicrobial resistance in animals. Where relevant, problems are viewed in a one health perspective. Currently, his own research projects are:


    1) Molecular mechanisms behind host-specificity of Salmonella serovars.

    The most severe Salmonella infections are caused by serovars which are host specific. This project studies the avian specific Salmonella serovar, S. Gallinarum, to understand why it only infects avians, and why it has such a high ability to cause Typhoid-like systemic infection in these species. It uses a combination of genomic, molecular-biology and infection biology approaches to identify how this serovar differs from closely related serovars without host-restriction and without the tendency to cause systemic infection.

    The project is funded by Independent Research Fund Denmark, and it is carried out in collaboration with other researchers within the Department (Immunology) and Professor Ferric Fang, University of Washington, US.


    2) Metabolic responses in antibiotic resistant Escherichia coli to treatment with antibiotics to which the strain is resistant.

    Antimicrobial resistance is a world health problem and we need to find ways to be able to treat infections caused by antimicrobial resistant bacteria. This project identifies genes, besides the actual resistance genes, which are essential for the ability of antimicrobial resistant E. coli to grow in the presence of high concentrations of antimicrobials, to which the strain is resistant. Such genes are termed "the secondary resistome", and the proteins encoded by such genes are putative targets for helper drugs, which, when used along with antimicrobials, may re-sensitize resistant bacteria to treatment. Relevant genes are identified by tranposon guided differential insertion sequencing technique (TraDIS). Libraries have been constructed in E. coli which are resistant to antibiotics of the classes: beta-lactams (cephalosporin), aminoglycosides, sulphonamides and trimethoprim. Metabolic modelling in collaboration with Oxford Brookes University, UK, is used to understand, which metabolic pathways are changed in response to treatment. 

    The project is financed by the EU-funded Ph.D training school (ITN-network) "INNOTARGETS" and a PhD scholarship from Pakistan. The training school is a collaboration between four Universities, two sector research institutes and two drug developing companies in Europe. John Elmerdahl Olsen is the coordinator of the ITN training network.  


    3) Inactivation of bacteria in stables using UV-light.

    Use of antimicrobials for livestock in Denmark is particularly high in pig production, and we need to find ways to reduce pathogen load to reduce the number of infections, which needs to be treated. This project, UVIBA, determines inactivation of pathogenic bacteria and virus by LED-UV light. The idea is that lamps in stables can deliver this type of light in addition to traditional white-light, and that constant or cyclic use of UV-light may reduce pathogenic load in the air and dust in the stables. This may lead to reduced problems with diseases. Inactivation is determined under laboratory conditions with models of the lamp and selected indicator and pathogenic bacteria, as well as for pathogenic bacteria and virus in stables with pigs and proto-type lamps.


    The project is funded by GUDP, and it is headed by the company FarmLight, which has developed the lamps. Other partners include DTU and Århus University.


    4) Escherichia coli pathotypes associated with diarrhoea in new borne calves.

    Diarrhoea in calves due to E. coli is common in the first one to two weeks of age and is an important reason for use of antimicrobials in young calves. Traditionally, the disease has been associated with the pathotype Enterotoxigenic E. coli (ETEC), characterized by production of enterotoxins and fimbriae which specifically allows colonization of the small intestine of calves, and current vaccines are directed against this pathotype. However, in recent years, this type of E. coli is not so commonly isolated from cases of diarrhoea in calves in Denmark. The project uses whole genome sequencing of isolates subjected to diagnostic laboratories or collected as part of dedicated sampling strategies, as well as metagenomic approaches with Nanopore sequencing of faecal samples, to elucidate which pathotypes, other can ETEC, one can detect in faeces from calves with E. coli diarrhoea.


    The project is funded by a stipend from the African Research Excellence Foundation and from the Danish Contingency Program. It is carried out in collaboration with Associate professor Jibril Abdurrahman, Sokoto University, Nigeria and other researchers at the Department (Food Safety). 



    5) Development of improved vaccines against post weaning diarrhoea in pigs.

    Diarrhoea in the post weaning period is the single most important reason for use of antimicrobials in Danish livestock. This project, PigVac, develops and tests novel vaccines against the three most common bacteria associated with diarrhoea in the period from weaning to when pigs are transferred to the fattening unit. The vaccines are based on so-called virus like particles, where antigens are coupled to the surface of empty virus particles. The structure of these particles with high density of antigens on the surface are known to give optimal priming of the immune system. The tested vaccines are directed against Entotoxigenic E. coli of fimbria types F4 and F18, Lawsonia intracellularis and Brachyspira pilisicoli. Prototype vaccines are first tested in mice models of infection and then in pigs. Outcome measurements include antibody responses, tolerance to vaccines, as well as the ability to protect against infections.


    The project is funded by Innovation Fund Denmark, and it is carried out in collaboration with researchers at Department of Microbiology and Immunology, KU, SEGES and the vaccine company AdaptVac. 


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