Genetic diversity of capsular polysaccharide biosynthesis in Klebsiella pneumoniae clinical isolates

Abstract

Klebsiella pneumoniae is an enteric pathogen causing community-acquired and hospital-acquired infections in humans. Epidemiological studies have revealed significant diversity in capsular polysaccharide (CPS) type and clinical manifestation of K. pneumoniae infection in different geographical areas of the world. We have sequenced the capsular polysaccharide synthesis (cps) region of seven clinical isolates and compared the sequences with the publicly available cps sequence data of five strains: NTUH-K2044 (K1 serotype), Chedid (K2 serotype), MGH78578 (K52 serotype), A1142 (K57 serotype) and A1517. Among all strains, six genes at the 59 end of the cps clusters that encode proteins for CPS transportation and processing at the bacterial surface are highly similar to each other. The central region of the cps gene clusters, which encodes proteins for polymerization and assembly of the CPS subunits, is highly divergent. Based on the collected sequence, we found that either the wbaP gene or the wcaJ gene exists in a given K. pneumoniae strain, suggesting that there is a major difference in the CPS biosynthesis pathway and that the K. pneumoniae strains can be classified into at least two distinct groups. All isolates contain gnd, encoding gluconate-6-phosphate dehydrogenase, at the 39 end of the cps gene clusters. The rmlBADC genes were found in CPS K9-positive, K14-positive and K52-positive strains, while manC and manB were found in K1, K2, K5, K14, K62 and two undefined strains. Our data indicate that, while overall genomic organization is similar between different pathogenic K. pneumoniae strains, the genetic variation of the sugar moiety and polysaccharide linkage generate the diversity in CPS molecules that could help evade host immune attack.

Effect in virulence of switching conserved homologous capsular polysaccharide genes fromKlebsiella pneumoniaeserotype K1 into K20

“…19 A cluster of genes are involved in capsule synthesis and driven by 2 promotors. 6 Previous studies have shown that 6 genes, galF, acidPPc, wzi, wza, wzb and wzc, are conserved among different capsular serotypes. 5,6 These conserved genes have also been proposed for the identification of capsular serotypes, including wzi and wzc.…”

“…6 Previous studies have shown that 6 genes, galF, acidPPc, wzi, wza, wzb and wzc, are conserved among different capsular serotypes. 5,6 These conserved genes have also been proposed for the identification of capsular serotypes, including wzi and wzc. 5,20 In this study, we have tried to elucidate the role of these conserved genes in virulence and whether they can function in a similar manner after exchanging a homologous gene from one serotype to another.…”

“…Each of these structural genes is serotype specific, and may or may not be replaceable with the homologous gene from another serotype. 6 Although previous study has transferred plasmid carrying whole CPS genes cluster of serotype K2 into K21, 7 homologous replacement of individual gene has not been studied.…”

“…Previous studies have shown that the capsule synthesis gene cluster in the different serotypes has 2 distinct regions. 5,6 One region consists of highly conserved genes (>50% nucleotide sequence similarity) while the other region is hypervariable. Each of these structural genes is serotype specific, and may or may not be replaceable with the homologous gene from another serotype.…”

The contribution of capsule polysaccharide genes to virulence of Klebsiella pneumoniae

“…12 While deletion of galF and acidPPC genes, which are driven by the P1 promoter, 13 had limited effect on virulence, the deletion of genes driven by the P2 promoter (wzi, wza, wzb, and wzc) exhibited moderate to high effects on virulence. The deletion mutants of the latter genes, which are responsible for surface assembly, CPS polymerization, and CPS production, also showed high susceptibility to neutrophilic phagocytosis and to serum.…”