Abstract
Hypervirulent Klebsiella pneumoniae is an emerging cause of community-acquired pyogenic liver abscess. First described in Asia, it is now increasingly recognized in Western countries, commonly afflicting those with Asian descent. This raises the question of genetic predisposition versus geospecific strain acquisition. We leveraged on the Antibiotics for Klebsiella Liver Abscess Syndrome Study (A-KLASS) clinical trial ongoing in ethnically diverse Singapore, to prospectively examine the profiles of 70 patients together with their isolates’ genotypic and phenotypic characteristics. The majority of isolates belonged to capsule type K1, a genetically homogenous group corresponding to sequence-type 23. The remaining K2, K5, K16, K28, K57 and K63 isolates as well as two novel cps isolates were genetically heterogeneous. K1 isolates carried higher frequencies of virulence-associated genes including rmpA (regulator of mucoid phenotype A), kfu (Klebsiella ferric uptake transporter), iuc (aerobactin), iro (salmochelin) and irp (yersiniabactin) than non-K1 isolates. The Chinese in our patient cohort, mostly non-diabetic, had higher prevalence of K1 infection than the predominantly diabetic non-Chinese (Malays, Indian and Caucasian). This differential susceptibility to different capsule types among the various ethnic groups suggests patterns of transmission (e.g. environmental source, familial transmission) and/or genetic predisposition unique to each race despite being in the same geographical location.
Highlights
A new, hypervirulent variant of Klebsiella pneumoniae has been increasingly described in the last two decades
K. pneumoniae isolated from healthy carriers has identical pulsed-field gel electrophoresis profile as well as similar virulence-associated genes and median lethal dose values in mouse lethality assays as hypervirulent variant of Klebsiella pneumoniae (hvKP) isolated from patients with liver abscess[17]
While hvKP was first discovered in the Asia Pacific Rim (e.g. Taiwan) in the mid-1980s19, it is increasingly recognized in Western countries (e.g. North America)[15,20,21]
Summary
A new, hypervirulent variant of Klebsiella pneumoniae (hvKP) has been increasingly described in the last two decades. Between these two distinct groups, clonal K1 isolates carried significantly higher frequencies of virulence-associated genes (kfu, iuc, iro, irp and rmpA) compared to non-clonal, non-K1 isolates (Fig. 1). The Chinese (n = 53) in our patient cohort had a significantly higher probability of infection with K1 compared to the non-Chinese (n = 17) consisting of Malays, Indian and Caucasian (71.7% vs 41.2%; P = 0.040; Fig. 3a).
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