Demonstration of regulatory cross-talk between P fimbriae and type 1 fimbriae in uropathogenic Escherichia coli

Abstract

The majority of Escherichia coli strains isolated from urinary tract infections have the potential to express multiple fimbriae. Two of the most common fimbrial adhesins are type 1 fimbriae and pyelonephritis-associated pili (Pap). Previous research has shown that induced, plasmid-based expression of a Pap regulator, papB, and its close homologues can prevent inversion of the fim switch controlling the expression of type 1 fimbriae. The aim of the present study was to determine if this cross-regulation occurs when PapB is expressed from its native promoter in the chromosome of E. coli K-12 and clinical isolates. The regulation was examined in three ways: (1) mutated alleles of the pap regulatory region, including papB and papI, that maintain the pap promoter in either the off or the on phase were exchanged into the chromosome of both E. coli K-12 and the clinical isolate E. coli CFT073, and the effect on type 1 fimbrial expression was measured; (2) type 1 fimbrial expression was determined using a novel fimS : : gfp + reporter system in mutants of the clinical isolate E. coli 536 in which combinations of complete fimbrial clusters had been deleted; (3) type 1 fimbrial expression was determined in a range of clinical isolates and compared with both the number of P clusters and their expression. All three approaches demonstrated that P expression represses type 1 fimbrial expression. Using a number of novel genetic approaches, this work extends the initial finding that PapB inhibits FimB recombination to the impact of this regulation in clinical isolates. INTRODUCTIONUrinary tract infections (UTIs) are common, affecting a large proportion of the population. It is estimated that 20 % of women develop a UTI in their lifetime, and antibiotic treatment results in approximately 110 000 prescriptions per million inhabitants per annum in Europe (Naber, 2000). Escherichia coli strains are the predominant cause of uncomplicated UTIs, responsible for between 60 and 80 % of the cases reported in the UK each year (Graham & Galloway, 2001). Many infections are asymptomatic, especially in the elderly (Nicolle, 2001), but others result in cystitis. If the infection ascends to the kidney, then pyelonephritis can occur. Such infections are a significant origin of Gramnegative sepsis.Fimbrial adhesins are important virulence factors that allow binding of the bacteria to specific receptors on epithelial cells of the urinary tract. The two adhesins most commonly associated with UTI are type 1 fimbriae, and pyelonephritisassociated pili (Pap) and Pap-related fimbriae (Prf); the last two are collectively termed P fimbriae in this study. Type 1 fimbriae mediate binding to a-D-mannose-containing receptors and extracellular matrix components, whereas P fimbriae bind to glycoreceptors containing the aGal(1-4)bGal moiety (Lindberg et al., 1984). Although type 1 fimbriae are common to the majority of E. coli isolates, the FimH adhesin has been shown to be important in a mouse model of UTI, and a degranulation response to the fimbriae is asso...

Functional Analysis of Antigen 43 in UropathogenicEscherichia coliReveals a Role in Long-Term Persistence in the Urinary Tract

“…In our forced Ag43 expression strains this effect would be enhanced even further as a result of constitutive gene expression (i.e., the genes are already "on"). In support of this model others have demonstrated the existence of an inverse relationship between type 1 fimbrial gene expression and P fimbrial gene expression (20,50,57). It has been proposed that during the course of an infection type 1 fimbriae are important in the early stages; however, as the infection progresses, increased expression of motility and P fimbrial genes occurs at the expense of type 1 fimbrial expression (5).…”

In Vivo Gene Expression Analysis Identifies Genes Required for Enhanced Colonization of the Mouse Urinary Tract by Uropathogenic Escherichia coli Strain CFT073 dsdA

“…The two loci may produce fimbriae that have different specificities or structural properties, or perhaps each locus is required under distinct spatial or temporal conditions and thus responds to different environmental signals. It is known that one pap operon can affect the expression of a second pap or other fimbrial operon present in a strain (24,31). It may be that such cross talk is necessary for function of the two CFT073 pap operons during mouse UTI.…”

Nicotinamide dependence of uropathogenic Escherichia coli UTI89 and application of nadB as a neutral insertion site

“…7. This demonstrated that the nadB gene can be used as a neutral site to integrate genes into the chromosome of E. coli, in addition to other possible sites like the lac operon (Holden et al, 2006), the unique insertion site of Tn7 (Craig, 1991) or functionless genes in bacterial genome (Ochman & Davalos, 2006).…”