Previous Article | Next Article ![]()
Infect. Immun., 03 1995, 847-852, Vol 63, No. 3
K Kabha, L Nissimov, A Athamna, Y Keisari, H Parolis, LA Parolis, RM Grue, J Schlepper-Schafer, AR Ezekowitz and DE Ohman
Klebsiella pneumoniae strains of the K2 capsular serotype are usually
highly virulent in mice, which is in contrast to the low virulence of most
other serotypes. Here we used a genetic approach to examine the relative
contribution of capsule type to the virulence of K. pneumoniae in mice. We
used wild-type strains expressing capsular polysaccharide (CPS) serotypes
K2 (strain KPA1) and K21a (strains KPB1 and KPC1), which were then used to
construct capsule-switched derivatives. The close proximity of the cps gene
cluster to selectable his markers made it possible to mobilize the cps
genes by conjugation from one serotype (donor) to another (recipient) and
to obtain recombinants in which interserotype switching had occurred by
reciprocal recombination. Each capsule-switched derivative examined of the
KPA and KPC strain backgrounds produced a CPS that was immunologically and
structurally identical to that of the donor. Strain background was
confirmed by demonstrating restriction fragment length polymorphism
patterns identical to those of the respective recipients. The parent
strains were then compared with capsule-switched recombinants for
phenotypic properties associated with virulence. Clearance from the
bloodstreams of mice was rapid in serotype K21a strains of either wild-type
or recombinant origin, whereas K2 strains remained viable in the blood
during the period examined. These differences appeared to be dependent upon
the CPS type but independent of strain background. Binding to macrophages
was higher in K21a strains than in those with the K2 capsule and was also
independent of the strain background. Both blood clearance and
macrophage-binding activities were completely inhibited by yeast mannan,
suggesting that they were mediated via the macrophage mannose receptor. The
K2 parent strain was highly virulent to mice (50% lethal dose [LD50], 3 x
10(3)), while the K21a parent strains demonstrated low virulence (LD50,
> 2 x 10(8)). Interestingly, the virulence of recombinant KPC10(cpsK2),
originally of the KPC1(cpsK21a) background, was intermediate (LD50, 4 x
10(5)). In contrast, both cpsK21a recombinants of the originally virulent
KPA1 (cpsK2) background became nearly avirulent (LD50, > 2 x 10(8)). Six
additional serotypes (K12, K24, K32, K55, K62, and K67) were examined, and
all showed a positive correlation between the ability of the Klebsiella
serotype to interact with a human mannose receptor, as expressed by Cos I
cell recombinants, and the LD50 of the serotype. These results suggest that
expression of a capsule which is recognized by the mannose receptor
markedly affects the interaction with macrophages and blood
clearance.(ABSTRACT TRUNCATED AT 400 WORDS)
Copyright © 1995, American Society for Microbiology
Relationships among capsular structure, phagocytosis, and mouse virulence in Klebsiella pneumoniae
Department of Human Microbiology, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|