TnphoA-mediated disruption of K54 capsular polysaccharide genes in Escherichia coli confers serum sensitivity.


Journal Article

To assess whether non-K1, group 2 capsular serotypes are important in conferring serum resistance to extraintestinal isolates of Escherichia coli, a K54 blood isolate (CP9) was evaluated as a model pathogen. Transposon mutagenesis (TnphoA) was used to generate isogenic capsule-negative mutants. CP9 was resistant to the bactericidal effects of serum, growing in 80% serum. In contrast, all of the capsule-negative mutants had an increased sensitivity to 80% normal human serum, undergoing a 2- to 3-log kill over 3 h when starting inocula of 10(4) to 10(7) CFU/ml were used. The killing of the capsule-negative strains was mediated through the alternative complement pathway and not by lysozyme or beta-lysins. The protective effect of the K54 capsule against the bactericidal activity of serum was not through inhibition of the complement cascade, nor did it appear to be through a difference in the binding of C3.

Full Text

Cited Authors

  • Russo, TA; Moffitt, MC; Hammer, CH; Frank, MM

Published Date

  • August 1993

Published In

Volume / Issue

  • 61 / 8

Start / End Page

  • 3578 - 3582

PubMed ID

  • 8392976

Pubmed Central ID

  • 8392976

International Standard Serial Number (ISSN)

  • 0019-9567

Digital Object Identifier (DOI)

  • 10.1128/IAI.61.8.3578-3582.1993


  • eng

Conference Location

  • United States