Studies on Fucose Synthesis Genes in Klebsiella Pneumoniae: Implication in Bacterial Virulence (I)

Our previous studies on Klebsiella pneumoniae (KP) showed that KP (KpL) isolated from liver abscess diabetic patient exhibited greater virulence than that (KpU) from urinary tract infection (UTI) patients in mice survival test. Analysis of capsular composition indicated that KpL (3 clinical isolates) strains contain high amount of fucose that is not seen in KpU strains (3 clinical isolates). Surface glycotope analysis revealed thatLewis antigens are present in the capsule of KpL strains but not that of KpU strains. Lewis antigens have been implicated in hepatic tropism and molecular mimicry for bacteria to evade host immunity. We consider Lewis antigens are important characteristics for virulent KP strains. Examining the sugar composition of the capsular polysaccharide, we also found that KpU contains large amount of mannose but no fucose. Bacteria derive fucose from mannose with two enzymes, namely GDP-Man 4,6 dehydratase (GMD) and GDP-Keto-6- deoxymannose 3,5 epimerase/4-reductase(GMER), and the fucose is added to the polysaccharide backbone by enzyme fucosyltransferase (FucT) to form Lewis antigens. Therefore our hypothesis is that the KpU has defect in the mannose to fucose conversion system, probably due to absence or mutation in the gmd or gmer genes. This proposal will study the gmd and gmer genes in KpL and KpU or other less virulent KP strains. We will start from the six strains that we have been studying. The gmd and gmer genes will be amplified using primers from KP genome sequence of from Helicobacter pylori sequence. The gmd and gmer genes will be cloned; DNA sequences will be determined and compared. The gene product will be analyzedfor enzyme activities. The amount of mRNA will be studies by RT-PCR/Northern or real-time PCR and the promoter activities will be characterized using reporter system. From the DNA sequence comparisons, we will design primers or specific probes as a tool for screening clinical isolates.

Project ID:PA9506-0070
External Project ID:NSC95-3112-B182-005