Infectious Diseases at KI DS – Johan Ursing's research group

We conduct clinical and translational research into severe respiratory tract infections, prosthetic infections, malaria, hepatitis, and antimicrobial resistance. Our work is based at the Department of Infectious Diseases at Danderyd Hospital and combines clinical trials, observational cohort studies, and molecular epidemiology. The aim is to improve the diagnosis, treatment, and management of common and difficult-to-treat infections.

The group conducts clinical and translational research into infectious diseases, with a focus on severe respiratory tract infections, Clostridioides difficile infection, Staphylococcus aureus bacteraemia, prosthetic joint infections, antimicrobial drug safety and malaria.

The work is based at Danderyd Hospital and draws on clinical trials, retrospective and prospective cohort studies, and molecular methods. The findings are regularly published in leading international journals in the fields of clinical infectious diseases, microbiology and antimicrobial therapy.

Our research

Severe respiratory tract infections

Mycoplasma pneumoniae

The group is studying severe M. pneumoniae pneumonia in adults.

Following retrospective studies of cases in Stockholm and corticosteroid treatment, an open-label, multicentre RCT of adjuvant betamethasone in severe M. pneumoniae pneumonia was conducted.

The results, published in 'Lancet Regional Health – Europe', showed that low-dose cortisone accelerated clinical stabilisation and shortened the length of hospital stay in cases of infection requiring oxygen therapy, providing an important scientific basis for future international treatment guidelines.

Mucosal immunity and vaccination

Ulrika Marking is pursuing a parallel line of research focusing on the immune response in the respiratory tract mucosa to SARS-CoV-2.

Through studies published in 'The Lancet Infectious Diseases' and 'EBioMedicine', the group has demonstrated how systemic vaccination and subsequent breakthrough infections affect the local mucosal IgA response over time.

This research is central to the development of future vaccines that can more effectively halt the spread of infection directly in the airways.

Sepsis and viral dynamics

During the COVID-19 pandemic, the group investigated the relationship between SARS-CoV-2 viraemia, disease progression and mortality in hospitalised patients.

Studies published in journals such as 'Clinical Infectious Diseases' show that detectable viraemia increases the risk of severe disease, as well as how remdesivir affects viral dynamics. A systematic review in 'Lancet Microbe' summarises the clinical significance of viraemia in respiratory viral infections.

Aetiology and optimised diagnosis of pneumonia

In his research, Niclas Johansson focuses on identifying microbiological agents in community-acquired pneumonia (CAP) in adults using highly sensitive PCR techniques.

Studies published in journals including 'The Lancet Infectious Diseases' and 'Clinical Infectious Diseases' have demonstrated a high prevalence of mixed infections and highlighted the hidden burden of disease associated with non-bacteraemic pneumococcal pneumonia.

The group has also investigated bacterial secondary infections during the pandemic and shown that these are significantly less common in COVID-19 compared with influenza and RSV.

Evidence-based guidelines and pre-hospital management

Carl Spindler’s research focuses on clinical management, risk stratification and quality improvement in lower respiratory tract infections.

Through extensive clinical cohort studies published in 'Infectious Diseases', this research has formed the backbone of the Swedish Society of Infectious Diseases’ national, evidence-based guidelines for the management of community-acquired pneumonia.

Another key project involves the development and implementation of pre-hospital decision support systems (DSS) for the ambulance service, enabling the early identification of patients with critical infectious conditions, including severe pneumonia and sepsis, for direct referral to the optimal level of care.

Clostridioides difficile and faecal microbiota transplantation

The group is investigating the epidemiology, risk factors and treatment of recurrent Clostridioides difficile infection.

A randomised, double-blind Phase I trial of frozen, encapsulated autologous faecal microbiota transplantation (FMT) has been published in 'PLOS ONE' (2023) and demonstrated acceptable safety and tolerability, marking a step towards simpler and more accessible FMT treatment.

A retrospective cohort study in 'BMC Infectious Diseases' (2025) identified clinical predictors of further recurrence following first and second relapses. The group is establishing a biobank of donated microbiota at Danderyd Hospital for future clinical studies on dosing and treatment efficacy.

Staphylococcus aureus bacteraemia

The group is investigating clinical and microbiological risk markers for Staphylococcus aureus bacteraemia.

In a retrospective cohort study published in 'Clinical Infectious Diseases' (2025), a short time to a positive blood culture was identified as an independent risk marker for infective endocarditis, with potential application as an early decision-making aid for further investigation and a shorter time to appropriate treatment.

Prosthetic infections

The group conducts research into antibiotic treatment and diagnosis of prosthetic infections. The work is based on a large cohort comprising over 600 episodes of infection at Danderyd Hospital since 2011.
Ongoing studies are evaluating risk factors for treatment failure in DAIR surgery, the side effects of long-term antibiotic treatment, and the efficacy of low-dose clindamycin and standard-dose amoxicillin in the treatment of prosthetic infections.

A parallel line of research is investigating the long-acting drug dalbavancin and its pharmacokinetics with and without rifampicin.

The group is also investigating diagnostic methods for prosthetic joint infections. A retrospective cohort study of microbiological findings and diagnostic outcomes during the period 2010–2022 is complemented by a prospective study of 200 patients evaluating the sensitivity and specificity of histopathology and synovial fluid leukocytes compared with conventional culture – methods that are recommended internationally but not routinely used in Sweden.

The results are expected to contribute to evidence-based diagnostic guidelines and safer empirical antibiotic treatment for prosthetic joint infections.

Malaria and drug-resistant malaria

The group has long been conducting research into the treatment of Plasmodium falciparum malaria and the molecular epidemiology of antimalarial resistance, with the majority of its fieldwork taking place in Guinea-Bissau.

The studies have characterised the efficacy, safety and pharmacokinetics of high-dose chloroquine in children and described a dormancy-like survival mechanism in chloroquine-exposed parasites ('Journal of Antimicrobial Chemotherapy', 2022).

The group participates in the WorldWide Antimalarial Resistance Network (WWARN) and contributes to meta-analyses of individual patient data on antimalarial treatment, with direct implications for the treatment and monitoring of drug resistance in low-income countries where the disease burden is greatest.

Publications

All publications from group members

Collaborations

We also conduct research into multidrug-resistant Gram-negative bacteria and phage therapy (Malin Vading), as well as chronic hepatitis C and its long-term effects (Magnus Hedenstierna, Charlotta Millbourn).

The group collaborates with several national university hospitals and, internationally, with organisations including the Bandim Health Project in Guinea-Bissau, the University of Southern Denmark, the University of Helsinki and WWARN.