Spontaneous loss and transfer of plasmid-mediated K21 antigen synthesis in Klebsiella pneumoniae.

Abstract

Five epidemiologically related urine isolates of Klebsiella pneumoniae (sensu lato), capsular serotype K21 may spontaneously lose the ability to synthesise K21 antigen in vitro and in vivo. Another four isolates of K. pneumoniae K21+, epidemiologically unrelated to the other five, did not exhibit this effect. Elimination of the ability to synthesise K21 antigen may be enhanced by treatment with acridine orange. Transfer of K21 antigen synthesis from K. pneumoniae to Escherichia coli K12 was observed in eight independent experiments. Elimination from or acquisition of the ability to synthesise K21 antigen is not accompanied by changes in the antibiotic sensitivity patterns or biochemical characteristics of bacteria.

Isolation from Klebsiella and Characterization of Two rcs Genes That Activate Colanic Acid Capsular Biosynthesis in Escherichia coli

“…The capsular polysaccharide of the mucoid E. coli clones contained glucuronic acid, galactose, glucose and fucose in accordance with the reported structure for colanic acid (Garegg et al, 1971) rather than K21 b polysaccharide, which contains glucuronic acid, galactose and rhamnose (unpublished observations). In addition, the mucoid transconjugant reported by Barr (1981) to have received K21-specific genes appeared to produce colanic acid rather than K21 b capsular polysaccharide.…”

“…Characteristically Klebsiella species are surrounded by a hydrophilic polysaccharide capsule and at least 83 different capsular serotypes have been recognized (Nimmich, 1968). It has been reported that the ability to express a sero-specific capsular antigen can be transferred from some strains of K. aerogenes (K. pneumoniae) K21 to Escherichia coli K12 (Barr, 1981). Attempts in this laboratory to transfer the ability to elicit either a mucoid character or K21 antigen per se by conjugation to E. coli or other klebsiellae have proved unsuccessful.…”

Plasmid-mediated conjugative transfer of Klebsiella sp. rcs genes able to induce colanic acid capsular polysaccharide biosynthesis in Escherichia coli

“…Despite repeated attempts, we were unable to transfer the ability to manufacture a capsule from the Klebsiella sp. K21b strain to E. co# in contrast to the report of Barr [7]. However, one strain of K. pneumoniae of serotype K36 proved to be capable of apparent transfer of a mucoid, capsular phenotype to E. coli when selection was made for transfer of the resistance markers it expressed (Table 1).…”

“…The mucoid Klebsiella sp. serotype K21b [3] used by Barr [7] and several other Klebsiella strains were tested for their ability to transfer both resistance markers and a capsular phenotype to a standard restriction-less Escherichia coli recipient. Despite repeated attempts, we were unable to transfer the ability to manufacture a capsule from the Klebsiella sp.…”

“…However, we have shown previously that the presence of colanic acid capsules confers little resistance to the bactericidal activity of human serum, nor does it inhibit phagocytic uptake or intracellular killing [6]. The apparent ability of certain strains of K. pneumoniae (aerogenes) to transfer the genes necessary to produce anti-K21-reactive capsular material, coupled with the evident instability of the capsular phenotype in certain Klebsiella strains, has led to the suggestion that the genes encoding some K antigens may be plasmid-borne [7]. We have shown previously that several different regions of the Klebsiella chromosome which bear rcs genes are able to induce the production of colanic acid when cloned on plasmid vectors in E. coli [8].…”