Ph.D. Defence by Louise Bruun Østergaard
Louise Bruun Østergaard will defend her Ph.D. thesis on "Staphylococcus aureus bactere-mia – host factors influencing the human infection risk"
04.03.2019 kl. 14.00 - 17.00
Staphylococcus aureus bacteremia (SAB) is of great concern worldwide due to the frequently fatal outcome, or endocarditis as a dreaded complication with a one-year mortality rate of 30–40%. Multiple factors increasing the risk of SAB have been identified, but whether socioeco-nomic status is associated with the adult risk of SAB or subsequent endocarditis has not been established. Further, knowledge on risk factors in the pediatric population is sparse and the current literature is limited by small numbers of patients and study design. Additionally, to the best of our knowledge a possible familial clustering of SAB has never been investigated. To improve future diagnosis, treatment and prognosis for patients with SAB, identification of ex-posures associated with increased rate of the disease, are essential to ensure early diagnosis. Moreover, a familial clustering of SAB would point towards a possible genetic component in the human susceptibility to S. aureus.
We cross-linked national registries at an individual level by use of each individual’s personal identification number to obtain information on demographics, education, comorbidities, medi-cation, surgical procedures, family relations, and microbiologically verified SAB.
The main results of this thesis were: Paper I) in adults, a low socioeconomic status was associ-ated with an increased risk of SAB, and this association declined with advancing age. The level of socioeconomic status did not influence the risk of subsequent infective endocarditis in pa-tients with bacteremia. Paper II) In children aged 5–18 years, the highest rates of SAB were observed in children receiving dialysis or plasmapheresis, transplanted children, children with cancer, congenital heart disease, atopic dermatitis and in children with recent surgery. How-ever, more than every third child with bacteremia were presumably healthy prior to the hospital admission for SAB. Neither parental socioeconomic status nor prematurity were associated with the risk of SAB in these children. Paper III) Having a first-degree relative previously hos-pitalized with SAB was associated with a more than two-fold increased rate of the disease compared with the background population. The highest risk of acquiring the bacteremia was observed if a first-degree relative was a sibling with non-hospital acquired SAB. Contagion could probably not explain our findings, since the causative S. aureus strain differed genetically in more than 80% of the infected families, and no increased risk was observed in spouses.
Knowledge on risk factors for SAB in both adults and children (Paper I and Paper II) may increase the awareness of the disease, thus improving early diagnosis and correct treatment. Lastly, knowledge on familial clustering of the disease can pave the way for future clinical genetic studies leading to prevention of familiar clustering.
Department of Health Science and Technology, Aalborg University