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Journal of Clinical Microbiology, July 2008, p. 2231-2240, Vol. 46, No. 7
0095-1137/08/$08.00+0     doi:10.1128/JCM.01716-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Capsular Polysaccharide Synthesis Regions in Klebsiella pneumoniae Serotype K57 and a New Capsular Serotype

Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan,¹ Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan,² Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada³

Received 29 August 2007/ Returned for modification 12 December 2007/ Accepted 17 March 2008

Community-acquired pyogenic liver abscess caused by Klebsiella pneumoniae is an emerging infectious disease. We explored the capsular polysaccharide synthesis (cps) regions of three non-K1, non-K2 K. pneumoniae strains, A1142, A7754, and A1517, from Taiwanese patients experiencing pyogenic liver abscess. Two of the strains, A1142 and A7754, belonged to capsular serotype K57, while the third belonged to a new capsular serotype, different from the previously reported 77 serotypes. Deletion and complementation experiments suggested that a unique K57 gene, a homologue of wzy, was essential for K57 capsular synthesis and confirmed that this gene cluster was a genetic coding region for K57. Compared to K1 and K2 strains, the three strains were all serum sensitive, suggesting that host factors might also be involved in the three patients. PCR using primers from specific genes for K57 was more sensitive and specific than traditional serotyping. The remaining strain, A1517, did not react to the antisera from any of the 77 serotypes, and none of the 77 reference strains reacted to the serum against this strain. Moreover, PCR analyses using various primer pairs from the serotype-specific open reading frames did not reveal cross-reactivity to any of the 77 reference strains, suggesting that this strain likely represents a new capsular type. We conclude that sequences from these two cps regions are very useful in detecting K57 and the new cps genotype.

Published ahead of print on 28 May 2008.