Restriction fragment length polymorphisms among uropathogenic Escherichia coli isolates: pap-related sequences compared with rrn operons

Abstract

Among the adhesin-encoding virulence operons associated with uropathogenic Escherichia coli, only pap (pyelonephritis-associated pilus)-related gene clusters typically exhibit variation in their structure and chromosomal copy number. To access further such variability, we compared pap restriction fragment length polymorphisms (RFLPs) with those detected among rRNA (rrn) operons, which encode an essential host function unrelated to virulence. To place such findings in a phylogenetic perspective, the E. coli isolates were also characterized by using multilocus enzyme electrophoresis. Variation in the rrn RFLP profiles correlated with evolutionary divergence resolved by multilocus enzyme electrophoresis; isolates with identical rrn profiles represented the same or closely related electrophoretic types. In contrast, such isolates frequently had different pap-related RFLPs, indicating that these genetic variations have developed recently relative to the changes associated with essential rrn operons or metabolic enzymes. Despite such fluctuations, two lines of evidence indicate conditions under which the pap-related RFLPs can be stably maintained. First, for each of 20 patients with urosepsis, both the primary urinary tract isolate and the concurrent blood isolate were identical. Second, although obtained from different patients, some isolates representing the same electrophoretic type also had identical pap-related RFLPs. Thus, the genotypic diversity of this virulence adhesin operon was not generated during the course of acute infection or during laboratory manipulations. Since fecal E. coli isolates frequently carry chromosomally encoded pap-related gene clusters, these findings suggest that the intraand interchromosomal recombination events generating the polymorphisms associated with the pap-related sequences likely occur among the E. coli of the commensal reservoir.Escherichia coli cause the substantial majority of urinary tract infections (33). As a group, such uropathogenic isolates exhibit properties that are not prevalent among commensal E. coli isolates found in the intestinal flora (40). Prominent among these phenotypes is the expression of adhesins that mediate bacterial attachment to the human uroepithelium and thereby confer a selective advantage in ascending colonization of the upper urinary tract by allowing the bacteria to resist the cleansing effect of urine flow in the ureters (29). pap (pyelonephritis-associated pili) and prs (pap-related sequence) are two structurally and functionally related operon clusters that have been cloned from E. coli J96 and shown to express adhesin pili (9,21,22). pap encodes a P-fimbrial adhesin that specifically recognizes the globoseries of glycolipids present on both human erythrocytes bearing the P blood group antigen and uroepithelial cells (19,21,22). prs encodes an F adhesin that preferentially binds to the Forsmann antigen, which is a major constituent of sheep erythrocyte membranes and is also present on the cells of the human renal pelvis (21,22).In a recent s...

The Link between Phylogeny and Virulence in Escherichia coli Extraintestinal Infection

“…Furthermore, sfa-positive strains of Maslow et al belong only to cluster III, and we have shown in this work and also previously (5) that sfa/foc operons are found only in the phylogenetic B2 group. Similarly, EcoRI rrn RFLPs and hly operon data presented by Arthur et al (1), when studying uropathogenic isolates, allows the conclusion that their group IV, which encompasses the majority of the strains, corresponds to phylogenetic B2 group strains. According to the common O18:K1:H7 strains studied by Selander et al (38) and Bingen et al (5) and to the virulence determinant distribution, most of the neonatal meningitis strains of group 1 of Selander et al correspond to phylogenetic B2 strains.…”

“…The barrier between commensalism and virulence results from a complex balance between the status of the host and the presence and expression of virulence factors in the bacteria. The genetic structure of E. coli can be considered clonal (37), and, indeed, various intestinal (41) or extraintestinal (1,26,38) E. coli infections have been linked to specific clones or groups of related clones. In several cases, pathogenicity has been correlated with the presence of genes encoding virulence factors organized on large blocks, called pathogenicity islands.…”

Conservation of an Actinomyces viscosus T14V type 1 fimbrial subunit homolog among divergent groups of Actinomyces spp

“…An exam-ination of a larger number of strains from various sources will be necessary to establish whether human isolates may have greater genetic diversity than nonhuman Actinomyces strains. Substantial heterogeneity in the chromosomal DNA related to the pyelonephritis-associated pili (pap) among E. coli strains from different sources has been observed (1,32).…”

Domain‐Specific Rearrangement between the Two Arg‐Gingipain‐Encoding Genes in Porphyromonas gingivalis: Possible Involvement of Nonreciprocal Recombination

“…39). In addition, the shuffling by intra-or interspecies horizontal transfer has been found in the E. coli pap pilin (1,34), Haemophilus influenzae capsule (15), Neisseria and Streptococcus species penicillin-binding proteins (4,20,41), Salmonella 0 antigen (37), E. coli 0 antigen (18), Vibrio cholerae 0139 0 antigen (2) and Salmonella enterica flagellin (16). In Streptococcus pyogenes, recombination events have been found in the genes encoding exotoxin A (speA) (29), exotoxin B (speB) (12), exotoxin C (speC) (11), M-protein (43), M-like proteins (44) and streptokinase (10).…”