In recent years a high incidence of community-acquired primary liver abscess caused by highly virulent strains of Klebsiella pneumoniae has been documented in Taiwan and other Asian countries. [^1-4]. A syndrome, with metastatic spread to eyes, meninges, brain and other sites, has been described, and is strongly associated with K. pneumoniae strains of capsular serotype K1 of a characteristic hypermucoviscous phenotype [⁴, ⁵]. Two plasmid encoded virulence genes, rmpA (regulator of the mucoid phenotype) and the iron siderophore aerobactin, as well as two chromosomal encoded virulence genes, kfu encoding an iron uptake system and allS associated with allatonin metabolism are significantly correlated with the high virulence of the invasive strains [⁶, ⁷]. These highly virulent strains are so far rare outside of Asia, but case reports from USA, Canada, Spain and Belgium have been published lately [^8-14].

We here report a Swedish patient with this emerging syndrome caused by a highly virulent K. pneumoniae isolate. This is, to our knowledge, the first case described in Northern Europe.

The rising incidence of K. pneumoniae community acquired primary liver abscess in otherwise healthy individuals caused by highly virulent strains and often complicated by severe metastatic infections is disturbing [², ³, ¹⁴]. Whereas this emerging infectious disease so far has been observed mainly in Asia, a rising number of cases from other geographic regions indicate that these infections may develop into a world wide problem. It is remarkable that the majority of cases outside Asia have involved patients of Asian ethnicity. The reasons for the predominance of this syndrome in patients of Asian ethnicity are not known, but suggest that genetic susceptibility may play an important role. Alternatively, it could be speculated that there may be a food source of the virulent bacteria. Cases with no history of traveling to Asia have been reported demonstrating that highly virulent K. pneumoniae strains are present outside of Asia [¹⁰, ¹², ¹³]. However, although our patient had only had Swedish and Vietnamese contacts, he may have been colonized with the strain in Vietnam 10 months before onset of symptoms.

Patients with a recent history of travelling in foreign countries are often thoroughly investigated for infections with virus, bacteria or parasites that are typical for the region visited. Bacterial species that are common all over the world can, with the same antibiotic susceptibility-pattern, vary geographically in regard to virulence-factors corresponding to clinical picture and outcome. A connection between the causative agent, the region visited and the clinical picture is easily overlooked if analyses of these bacterial strains are restricted to identification to species-level and susceptibility-testing. With this case report, we would like to highlight an emerging syndrome caused by a bacterial species common in Europe, but of a serotype and with specific virulence genes still rare outside of Asia.

We thank Dr Johan Rydberg at the Department of Clinical Microbiology and Immunology at the University Hospital in Lund, for his support and valuable comments.