Expression of type 1 and P fimbriae in situ and localisation of a uropathogenic Escherichia coli strain in the murine bladder and kidney.

:Adhesion is an important aspect of bacterial colonisation and induction of human disease. Escherichia coli which infects and causes disease of the urinary tract expresses several adherence factors including type 1 and P fimbriae. Their expression has been implicated in the virulence of E. coli strains infecting the urinary tract, however, the evidence for the expression of these fimbriae in situ has been implied rather than proven. Here we describe in situ detection of E. coli and of fimbrial expression in urinary tract tissue. Kidneys and bladders were isolated from mice infected with the uropathogenic isolate E. coli AD110. The tissue was sectioned and subjected to DNA-rRNA hybridization and indirect immunofluorescent staining with antibodies against type 1 and P fimbriae. Sections of both kidney and bladder stained positive for bacterial cells using a Cy3-labelled E. coli-specific rRNA probe. The same cells in these sections also stained positive for type 1 or P fimbriae using fluorescein-labelled antibodies. Tissue taken from several different time points (2, 6, and 24 hours post infection) showed the presence of bacterial cells which stained positive for fimbrial expression. Bacteria in kidney and bladder sections were observed either as individual cells associated with the mucosa or as members of microcolonies.

Connell H ，Poulsen LK ，Klemm P 《INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY》

Blocking adherence of uropathogenic Escherichia coli isolate to HEP-2 cells and bladder of mice in the presence of antibody against p-fimbriae.

Presence of fimbriae on Escherichia coli isolated from the urine of patients with urinary tract infection was related to the ability of the bacteria to attach to human uroepithelial cells. One of the 50 isolates that expresses high MRHA p-fimbriae, selected and antibody against p-fimbriae from it, showed blocking of attachment of bacteria to HEP-2 cell in 1:1024 titer. Also, 1:512 titer of this antiserum to blocking of attachment in bladder tissue of mice is significant.

Bidhendi SM ，Sattari M ，Pourbakhsh SA ，Mobarez A ，Vandyousefi J ，Khaki P ，Heidari MH ，Kazemnejad A ... -  《BIOLOGICALS》

In vivo detection of Escherichia coli type 1 fimbrial expression and phase variation during experimental urinary tract infection.

Adhesion mediated by fimbriae is thought to play an important role in the pathogenesis of urinary tract infections (UTI) by Escherichia coli. The majority of clinical isolates of E. coli from UTI are able to express type 1 fimbriae. However, the importance of these fimbriae as a virulence factor has been controversial. To investigate the expression of type 1 fimbriae in vivo during UTI, mice were transurethrally infected with uropathogenic E. coli C175-94 and type 1 fimbrial expression was determined directly by two independent methods at 2 h, 1 d and 3 d after infection. By use of an assay combining in situ rRNA hybridization and immunofluorescence, all bacterial cells detected in urine, bladders and kidneys from mice sacrificed 1 and 3 d after onset of infection were found to express type 1 fimbriae. In contrast, the majority of cells in the suspension used for infection of mice and specimens from mice sacrificed 2 h after inoculation were found to be non-fimbriated. Similar results were obtained with a PCR assay revealing the orientation of the invertible promoter driving the transcription of type 1 fimbrial genes. Whilst the promoter in both ON and OFF positions could be amplified from the suspension used for infection and specimens from mice sacrificed 2 h after inoculation, at 1 and 3 d after onset of infection only the promoter in the ON orientation could be amplified. These results show that introduction of E. coli C175-94 into the mouse urinary tract leads to markedly enhanced expression of type 1 fimbriae.

Struve C ，Krogfelt KA 《MICROBIOLOGY-SGM》

Do type 1 fimbriae promote inflammation in the human urinary tract?

Type 1 fimbriae have been implicated as virulence factors in animal models of urinary tract infection (UTI), but the function in human disease remains unclear. This study used a human challenge model to examine if type 1 fimbriae trigger inflammation in the urinary tract. The asymptomatic bacteriuria strain Escherichia coli 83972, which fails to express type 1 fimbriae, due to a 4.25 kb fimB-fimD deletion, was reconstituted with a functional fim gene cluster and fimbrial expression was monitored through a gfp reporter. Each patient was inoculated with the fim+ or fim- variants on separate occasions, and the host response to type 1 fimbriae was quantified by intraindividual comparisons of the responses to the fim+ or fim- isogens, using cytokines and neutrophils as end-points. Type 1 fimbriae did not promote inflammation and adherence was poor, as examined on exfoliated cells in urine. This was unexpected, as type 1 fimbriae enhanced the inflammatory response to the same strain in the murine urinary tract and as P fimbrial expression by E. coli 83972 enhances adherence and inflammation in challenged patients. We conclude that type 1 fimbriae do not contribute to the mucosal inflammatory response in the human urinary tract.

Bergsten G ，Wullt B ，Schembri MA ，Leijonhufvud I ，Svanborg C ... -  《CELLULAR MICROBIOLOGY》

Role of phase variation of type 1 fimbriae in a uropathogenic Escherichia coli cystitis isolate during urinary tract infection.

Type 1 fimbrial phase-locked mutants of uropathogenic Escherichia coli cystitis isolate F11 were used to assess the role of the invertible element during urinary tract infection. Compared to the wild type, the phase-locked off mutant was attenuated, and constitutive production of type 1 fimbriae by the phase-locked on mutant did not provide a competitive advantage.

Snyder JA ，Lloyd AL ，Lockatell CV ，Johnson DE ，Mobley HL ... -  《-》