Klebsiella pneumoniae genotype K1: an emerging pathogen that causes septic ocular or central nervous system complications from pyogenic liver abscess.
BACKGROUND
Since 1986, researchers have noted a syndrome of Klebsiella pneumoniae pyogenic liver abscess that is complicated by endophthalmitis or central nervous system infections. There are limited data regarding the role of bacterial genotype in the pathogenesis of this syndrome.


METHODS
We conducted a retrospective cohort study involving 177 cases of K. pneumoniae pyogenic liver abscess treated during 1997-2005 at a tertiary university hospital in Taiwan. We performed bacterial cps genotyping by polymerase chain reaction detection of serotype-specific alleles at wzy and wzx loci and used an in vitro serum assay to evaluate the virulence of bacterial strains.


RESULTS
Septic ocular or central nervous system complications developed in 23 patients (13%). Logistic regression analysis showed that genotype K1 was the only significant risk factor (adjusted odds ratio, 4.8; 95% confidence interval, 1.5-15.7, P=.009). The serum resistance assay indicated that, on average, K1 strains (n=100) were significantly more virulent than were strains of K2 (n=36), K20/K5/K54 (n=21), or other genotypes (n=20) (P<.001 for each comparison). In addition to the serotype-specific cps region, the genomic background of K1 strains also differed significantly from that of non-K1 strains (20-kb kfu/PTS region, 97/100 vs. 13/77; P<.001). Of the 19 cases in which genotype K1 strains caused complications, 8 patients (42%) did not have identifiable underlying medical diseases.


CONCLUSIONS
K. pneumoniae genotype K1 is an emerging pathogen capable of causing catastrophic septic ocular or central nervous system complications from pyogenic liver abscess independent of underlying diseases in the host.
Fang
Chi-Tai
CT
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan. fangct@ntu.edu.tw
Lai
Shau-Yan
SY
Yi
Wen-Ching
WC
Hsueh
Po-Ren
PR
Liu
Kao-Lang
KL
Chang
Shan-Chwen
SC
D002493:Central Nervous System Diseases / Q000209:etiology* / Q000382:microbiology; D004198:Disease Susceptibility; D015818:Eye Infections, Bacterial / Q000209:etiology*; D005838:Genotype; D006801:Humans; D007711:Klebsiella pneumoniae / Q000145:classification / Q000235:genetics; D046290:Liver Abscess, Pyogenic / Q000150:complications* / Q000382:microbiology; D012703:Serotyping