A Protein Factor Associated With Serum Resistance in Escherichia Coli

Abstract

IT has long been known that many strains of gram-negative bacteria are insensitive to the bactericidal action of normal human serum despite the presence in the serum of bactericidal antibody and complement (Georgevitch, 1926;Mackie and Finkelstein, 1931); the nature of this resistance remains obscure. Serum resistance in Escherichia coZi has been variously ascribed to the amount of cell-wall lipopolysaccharide (LPS), the length and number of LPS 0-side chains and to both the amount and haemagglutination-inhibiting activity of acidic polysaccharide K antigen (see review by Inoue, 1972). In a recent study (Taylor, 1975), it was found that none of these factors was able to explain the behaviour of serum-resistant mutants derived from smooth, E. coli strains isolated from the urinary tract, and it was suggested that these mutants synthesised an additional surface component, possibly protein in nature, which was responsible for serum resistance.The present study concerns the analysis of one of the serum-resistant mutants and the corresponding parent strain by gel-diffusion techniques and by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis of cellenvelope proteins in an attempt to determine the basis of the mutation to serum resistance. Colonially rough mutants isolated from cultures of the serum-resistant mutant were also examined.MATERIALS AND METHODS BacteriaZ strains. E. coli no. LP729 is a smooth strain of serotype 0 9 which is rapidly killed by human serum after a delay of 1 h; E. coZi no. I7 is a serum-resistant mutant derived from strain LP729 by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (Adelberg, Mandel and Chen, 1965). Both strains produce negligible amounts of K antigen, are stable in 0.2% acriflavine and synthesise LPS containing large amounts of mannose, a sugar confined to the 0-side chain of LPS from E. coli 0 9 strains. E. coli nos. I7fa and I7gb are colonially rough mutants plated from an aged (4-week) nutrient-broth culture of strain 17. E. coli no. I7fa is rapidly killed by serum and is a rfb mutant (Schmidt, Jann and Jann, 1969) with a complete LPS R2 core but defective in the synthesis of the LPS 09-side chain. Strain I7gb possesses a full complement of LPS 0-side chains and interacts with serum in an identical way to strain LP729. Both colonially rough forms spontaneously agglutinate in 0.2 % acriflavine. Whereas strains LP729 and I7 are able to cause kidney infection in an experimental rat model, strains I7fa and I7gb are unable to do so (Taylor and Koutsaimanis, 1975). These strains are described in detail by Taylor (1975).

Serum resistance associated with virulence in Yersinia enterocolitica

“…on August 31, 2020 by guest http://iai.asm.org/ Downloaded from but not at 25°C. Also, in some E. coli strains the presence of an additional protein surface antigen has been shown to be partly responsible for serum resistance (30). Serum resistance is not, of course, the only factor required to convert an otherwise benign strain of Y. enterocolitica into a virulent strain.…”

Differences among Shigella spp. in Susceptibility to the Bactericidal Activity of Human Serum

“…(Joiner et al, 1982), Campylobacter spp. (Blaser et al, 1985), and Escherichia coli (Taylor & Parton, 1977) are known to activate both complement pathways, but Neisseria gonorrhoeae (Shafer et al, 1984), Pseudomonas aeruginosa (Schiller et al, 1984) and Haernophilus ducreyi (Odumeru et al, 1985) activate mainly the classical pathway.…”

Escherichia coliin extra-intestinal infections

“…Disease and stool isolates did not differ in virulence, confirming Sj6stedt's (1946) old observations. Taylor & Parton (1976) described an outer membrane protein with influence on serum sensitivity which was only functional in strains with full development of lipopolysaccharide side chains. Plasmid-determined factors with an influence on serum killing have been described by several investigators and have been reviewed extensively by Taylor (1983).…”