Escherichia coli from urine of female patients with urinary tract infections is competent for intracellular bacterial community formation - PubMed (original) (raw)

Escherichia coli from urine of female patients with urinary tract infections is competent for intracellular bacterial community formation

Corinne K Garofalo et al. Infect Immun. 2007 Jan.

Abstract

Nearly 50% of women experience at least one urinary tract infection (UTI) in their lifetime. Studies with mice have revealed that uropathogenic Escherichia coli (UPEC) isolates invade superficial umbrella cells that line the bladder, allowing them to find a safe haven and subvert clearance by innate host responses. Rapid intracellular replication results in the formation of distinctive intracellular bacterial communities (IBCs). In this study, we evaluated whether UPEC strains cultured from the urine of women and classified as causing acute cystitis, recurrent cystitis, asymptomatic bacteriuria, or pyelonephritis could progress through the IBC cascade in a well-characterized mouse model of cystitis. Of 18 UPEC isolates collected from women, 15 formed IBCs. Variations in the size, number, and kinetics of IBC formation were observed with strains isolated from women with different clinical syndromes. Two of the three isolates that did not form IBCs when inoculated alone were able to do so when coinoculated with an isolate that was capable of generating IBCs. The mixed infections dramatically altered the behavior of the coinfecting bacteria relative to their behavior in a single infection. The study also showed that mice with five different genetic backgrounds can support IBC formation. Although UPEC isolates differ genetically in their virulence factors, the majority of UPEC isolates from different types of UTI proceed through the IBC pathway, confirming the generality of IBCs in UTI pathogenesis in mice.

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Figures

FIG. 1.

Immunoblot of pyelonephritis isolates with antibodies against P pili. P pilus antibodies were raised against J96 P pili; thus, J96 and UTI89 were used as positive controls for P pilus production. Both isolates are positive for P pili due to a PapA-specific band at a molecular weight of 16,500 (16.5K). However, the P pilus antibody did not recognize the 16.5K protein for the four pyelonephritis isolates, confirming the lack of the pap operon seen with multiplex PCR. Thus, pyelo1, pyelo2, pyelo3, and pyelo4 do not contain the genes, nor do they produce protein associated with P pili, which are thought to be critical in kidney colonization.

FIG. 2.

UTI89 and CFT073 formed IBCs in multiple mouse strains. UTI89 and CFT073, two commonly used UTI isolates, were inoculated into five different mouse strains. At 6 h postinfection, each mouse strain was able to support IBC formation by each UTI isolate. A to E represent UTI89 IBCs, and F to J represent CFT073 IBCs.

FIG. 3.

IBCs were formed by UPEC strains isolated from women. Clinical isolates (red) were inoculated into female C3H/HeN mice, and bladders were harvested at 3 h, 6 h, and 24 h. Fifteen isolates produced IBCs at either (A and B) 3 h, (C and D) 6 h, or (E and F) 24 h. Each clinical syndrome is represented at the top of each panel. The cell surface (green) was stained with WGA and can be seen bordering the umbrella cells in this cross-sectional view. While the majority of isolates produced IBCs, the sizes and densities of the IBCs varied. Bars, 10 μm.

FIG. 4.

The three non-IBC-forming isolates, rUTI1, acute4, and pyelo3, were deficient in invasion in vivo. Female C3H/HeN mice were inoculated with UTI89, rUTI1, acute4, and pyelo3. At 1 h postinfection, bladders were removed and processed. The luminal fraction represents luminal bacteria, and the intracellular fraction represents invaded bacteria. One hour after inoculation, 4.4% of UTI89 bacteria invaded, whereas for rUTI1, acute4, and pyelo3, only 0.3%, 0.5%, and 1.1% of luminal bacteria invaded, respectively. Thus, the three non-IBC-forming isolates invade poorly relative to UTI89.

FIG. 5.

Coinfection with a clinical isolate and UTI89 altered the behavior of the bacteria. (A and B) rUTI1 (red) produced IBCs only when coinfected with UTI89 (green) and caused UTI89 to produce abnormally large IBCs (compare A to C). (C and D) acute4 (red) formed mixed IBCs with UTI89 (green), which also formed normal IBCs. (E and F) pyelo3 (red) formed large collections of filaments, induced UTI89 (green) to do the same, and prevented UTI89 IBCs. Bars, 10 μm.

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Escherichia coli from urine of female patients with urinary tract infections is competent for intracellular bacterial community formation - PubMed (original) (raw)