Hypermucoviscous Klebsiella pneumoniae is an emerging cause of community-acquired liver abscess in Asian populations worldwide, affecting predominantly diabetic individuals with a normal biliary system. In Singapore, Klebsiella liver abscess (KLA) is now the most common cause of liver abscess. Septic metastases may occur, particularly to eye, brain and lung. Bacterial capsular serotypes K1 and K2 have been shown to be major virulence factors. We aimed to recruit a prospective cohort of KLA patients to characterize demographic, biochemical and radiologic features, and identify strains associated with KLA in Singapore.
Patients with KLA were identified from 3 tertiary hospitals in Singapore. Inclusion criteria included liver abscess on imaging, with positive cultures for K. pneumoniae from blood or abscess fluid. Informed consent was obtained to collect demographics, imaging results, and blood or abscess fluid for strain typing and PCR genotyping of virulence-associated genes.
59 patients were recruited over 16 months. 47 (80%) were male and 28 (48%) had diabetes mellitus. Median age was 59 (SD 11.6). 47 (80%) were bacteremic and 22 (37%) had positive abscess culture. 33 (56%) had a single abscess, 26 (44%) had multiple. Median maximal abscess diameter was 4.8 cm (SD 3.2). 16 (27%) had metastatic disease (mainly lung). All K. pneumoniae strains were sensitive to ceftriaxone, ciprofloxacin and co-trimoxazole. 54 (92%) were hypermucoviscous phenotype. 37 (63%) were K1 capsule type by PCR, 12 (20%) were K2 and 4 (7%) were K5. 5 (9%) were untypeable. 31 (53%) were positive for magA, 56 (95%) for rmpA and 56 (95%) for aerobactin. 50 (85%) isolates were highly serum resistant (grade 5; viable counts after 3 hours incubation in healthy pooled human serum ≥ 100% of the initial inoculum), 3 (5%) were serum resistant (grade 4; 70 - 99%), 3 (5%) were poorly serum resistant (grade 2; 1 - 29%), and 3 (5%) were not serum resistant (grade 1; 0%). Interestingly, the allS gene (allantoin metabolism) which was previously thought to be serotype K1-specific, was detected in 2 (17%) of serotype K2 isolates.
KLA afflicts a predominantly middle-aged male population in Singapore. Previous studies have associated KLA exclusively with K1 and K2 capsule types. We identified a small number due to K5 or untypeable capsule strains.
J. S. Molton,
J. Teo, None
S. Kalimuddin, None
D. Lye, None
Y. H. Gan, None
S. Archuleta, None