Virulence of wild-type E. coli uroisolates in experimental pyelonephritis

This study was designed to analyze the colonizing and invasive properties of wild-type bacteriuric E. coli possessing a variety of phenotypic characteristics in experimental nonobstructive pyelonephritis (P and Type 1 [T] fimbriae, hemolysin [Hly], presence of K capsules, flagella [H], serotype, biotype, human and mouse serumcidal resistance). Special emphasis was on the role of Gal-Gal adhesin (P fimbriae) of non-genetically engineered uroisolates. It was shown that organisms that are P+ or T+ or Hly+ are more likely to colonize bladders than strains negative for those parameters (P less than 0.001). Additionally, P+ strains were more often associated with kidney histopathology than P- E. coli (P less than 0.05). However, the data also indicated that fimbriae (P and Type 1) were not sole determinants of virulence since two strains devoid of fimbriae, hemolysin, K capsules and sensitive to human serumcidal activity caused incipient and acute pyelonephritis. Even among identical serotypes and biotypes, the presence/absence of fimbriae did not appear to be the critical factor in urovirulence, nor did the presence of several positive characteristics (hemolysin, K capsule, flagella, serum resistance) in a given strain enhance uropathogenicity. Therefore, these properties do not need to work together to render an E. coli urovirulent. These phenotypic characters may simply represent associated or serologic markers with the host serving as the dominant determinant of susceptibility to urinary infection. The findings emphasize the inherent limitations in relating and extrapolating colonizing and invasive properties of genetically engineered strains to those of naturally occurring, wild-type E. coli human uroisolates causing pyelonephritis.     

Detailed histopathological examination contributes to the assessment of Escherichia coli urovirulence.

To determine the usefulness of detailed histopathological evaluation in the assessment of urovirulence of different Escherichia coli strains in a mouse model of ascending, unobstructed urinary tract infection, and to evaluate the relationship between susceptibility to urinary tract infection and renal levels of P fimbrial receptor glycolipids in different mouse strains, female Swiss Webster and Balb/c mice were inoculated transurethrally with one of four different well-characterized wild type E. coli strains or with an E. coli K-12 laboratory strain, and renal glycolipid levels were determined for both mouse strains. In Swiss Webster mice, each of the wild type E. coli strains was more virulent than the laboratory strain by both microbiological and histopathological criteria. Despite the common origin and identical virulence factor profiles of the three urosepsis isolates studied, one was significantly less urovirulent than the other two. Paradoxically, this strain stimulated a greater degree of leukocytosis than did the more urovirulent strains. Balb/c mice were significantly more susceptible to infection with this strain than were Swiss Webster mice, a difference possibly contributed to by the significantly higher renal levels of P fimbrial receptor glycolipids in Balb/c mice. Detailed histopathological analysis revealed significant differences in virulence between bacterial strains, and in susceptibility to infection between different mouse strains, that were inapparent from culture results alone.     

Biofilm formation in uropathogenic Escherichia coli strains: relationship with prostatitis, urovirulence factors and antimicrobial resistance

PURPOSE: Escherichia coli strains are the most frequent cause of urinary tract infections. Biofilm formation allows the strains to persist a long time in the genitourinary tract and interfere with bacterial eradication. We determined the possible relationships between the different urinary tract infections, and in vitro biofilm formation, the presence of urovirulence factors and nalidixic acid resistance. MATERIALS AND METHODS: A total of 151 E. coli strains collected from patients with cystitis (44 strains), pyelonephritis (75) and prostatitis (32) were analyzed for in vitro biofilm formation, the phylogenetic group, the presence of several urovirulence factors and resistance to nalidixic acid. RESULTS: E. coli strains causing prostatitis produced biofilm in vitro more frequently than those causing other urinary tract infections and had a higher frequency of hemolysin (p = 0.03 and 0.0002, respectively). However, only hemolysin was independently associated with prostatitis. On the other hand, strains forming biofilm presented a significantly higher frequency of hemolysin and type 1 fimbriae expression. CONCLUSIONS: Although hemolysin is the main virulence factor by which E. coli causes acute prostatitis, the association between hemolysin and biofilm formation may result in increased ability of E. coli strains to persist in the prostate.     

Outer membrane proteins of E. coli in the host-pathogen interaction in urinary tract infection.

Outer membrane protein patterns (Omp) of Escherichia coli obtained directly from the urine of bacteriuric patients without passage on artificial culture media (ACM) were studied by polyacrylamide gel electrophoresis (SDS-PAGE) in an effort to determine whether in vivo conditions of growth affected the expression of these bacterial surface structures. Seventeen strains studied showed two distinct Omp patterns: one protein band appeared at the level of porin proteins (40 kDa) in both patterns, but Omp A protein was at the level of 36 kDa in the first pattern and a new protein was observed at 21.5 kDa in the second pattern suggesting that it is a fragment of Omp A. High molecular weight proteins were also observed in most of the strains and this finding was related to lack of free iron when the same strains were grown under iron restricted conditions in vitro. The same strains grown in pooled urine from normal females showed the first pattern mentioned above. Comparative growth on ACM of urinary strains and E. coli strains isolated from blood, feces and wounds showed an increase in the number of porins expressed (from 1 to 2 or 3, with some variability observed between strains). Differences in osmolality between pooled urine and ACM used, plus in vitro studies varying the osmolality of culture media, showed that osmolality accounted for differences in the number of porins expressed: porin expression decreased in urine the ACM of high osmolality, suggesting that the same phenomena occurred in vivo. It is concluded that host factors including low availability of iron and high osmolality present in the urinary tract influence the expression of several E. coli surface proteins. These proteins may relate to the ability of E. coli to colonize and invade the urinary tract by regulating the physiologic and/or metabolic state of the bacterial cell favoring survival of the organism in a hostile environment. Specific immune responses directed against porins could influence the outcome of this host-parasite interaction.     

Virulence of Escherichia coli strains in relation to their hemolysin formation, mannose-resistant hemagglutination, hydroxamate production, K 1-antigen and the plasmid profile in patients with chronic pyelonephritis

Microorganisms initiating infections of the kidneys and the upper urinary tract are characterized by specific properties. In 96 patients with non-obstructive chronic pyelonephritis, Escherichia coli strains were isolated and their virulence properties studied. Most frequently hemolysin formation and mannose-resistant hemagglutination (n = 39/40%), less frequently the ability to produce hydroxamate/aerobactin (n = 18/19%) and the K 1-antigen (n = 13/14%) were detected. In 34 E. coli strains (35%) two and more virulence factors were found. A statistically significant correlation exists between mannose-resistant hemagglutination (evidence of P- and F7-F14 fimbriae) and hemolysin formation on the one hand and hydroxamate production and K 1-antigen on the other (confidence intervals are 0.56-0.75 and 0.75-0.89, respectively). Disease activity and pathogenicity of E. coli strains showed a statistically significant association (chi 2-value, DF 1: hemolysin 29.5, mannose-resistant hemagglutination 17.1, K 1-antigen 4.8, hydroxamate 0.5). The analysis of the plasmid profile yielded species in molecular weight range from 0-170 Md. A correlation between single virulence features and certain plasmid combinations failed to be demonstrated. The results revealed a close connection between certain virulence properties of E. coli strains and a specific uropathogenicity. The clinical significance of this observation should be further elucidated.     

URODYNAMIC FACTORS INFLUENCE THE DURATION OF ESCHERICHIA COLI BACTERIURIA IN DELIBERATELY COLONIZED CASES

Purpose

We evaluated the influence of urodynamic factors on the establishment of bacteriuria, after deliberate intravesical inoculation with Escherichia coli.

Materials and Methods

Nine women and 7 men with recurrent symptomatic urinary tract infections underwent intravesical injection of E. coli 83972. This strain had documented ability to persist in the urinary tract and it lacks expressed virulence factors associated with urinary tract infection.

Results

Successful long-term colonization (5 months to 3 years) was achieved in 6 of 12 patients with neurogenic bladder disorder, including normal or high bladder capacity, normal or low detrusor pressure and residual urine. Short-term bacteriuria (13 days) occurred in 1 but long-term bacteriuria was not established in the 4 patients with normal lower urinary tract function. Occasionally urine samples from the colonized patients contained other bacterial strains, which cleared spontaneously except for a Klebsiella strain that became established in 2 and subsequently eliminated E. coli 83972.

Conclusions

E. coli 83972 bacteriuria could only be established in a subset of patients with defective bladder voiding, suggesting that urodynamic defects permit a nonvirulent strain to establish in the urinary tract, but that additional host factors determine if bacteriuria will persist.     

Adherence of E. coli to bladder epithelia in compromised mice and plasma endotoxin level]

The role of bacterial adherence in association with complicated urinary tract infections (UTI) and the correlation between bacterial adherence and plasma endotoxin (ET) levels were experimentally investigated by using mouse UTI models. Mice with foreign bodies induced in the bladder or voiding dysfunction were more susceptible to UTI than untreated mice. But diabetic or granulocytopenic mice were little susceptible to UTI in comparison with other two models. Adherence activities of 6 strains of E. coli to mice bladder epithelia in the 4 compromised models showed no difference when compared with those in normal control. Binding patterns of 8 kinds of lectins and mouse uromucoid polyclonal antibody to the mice bladder epithelia in compromised models appeared to be almost the same as those in the normal bladder epithelia. These results suggested that the reason for the susceptibility to UTI in the compromised mice was not necessarily explained based on the increased adherence of E. coli due to qualitative or quantitative changes in receptors on the bladder mucosa. Impairment of other host defense mechanisms may be considered in this regard. Three strains of E. coli expressing type 1 pili adhered to the bladder epithelia in greater numbers in vivo than non piliated strains. E. coli No. 113 strain expressing both type 1 and p pili appeared to be the most virulent in vivo among all 6 strains. Plasma ET levels increased 6 to 24 hours after inoculation of 2 strains of E. coli expressing only type 1 pili or p pili, while a little increase in the levels was observed in mice inoculated with non piliated E. coli. Bacterial adherence to the bladder epithelia may play an important role for the increase in ET levels.     

Escherichia coli strains causing urinary tract infection in uncircumcised infants resemble urosepsis-like adult strains

PURPOSE: Urinary tract infection (UTI) is the most frequent bacterial infection in infants younger than 90 days, and mainly affects uncircumcised males. In an attempt to unravel further the pathophysiology of UTI in this age group we used molecular methods to characterize Escherichia coli strains responsible for community acquired UTI in male and female infants and in adults. MATERIALS AND METHODS: A total of 79 E. coli isolates from uncircumcised male and female infants with UTI and no urinary tract abnormalities and 41 E. coli pyelonephritis isolates from nonhost compromised adults with bacteremia were characterized in terms of phylogenic relatedness and virulence factors. RESULTS: Males were infected by strains with a genetic background and virulence factors different from those affecting females but similar to those of adult pyelonephritis strains. CONCLUSIONS: Our molecular approach indicates that uncircumcised male infants are at higher risk for infection with highly virulent uropathogenic E. coli strains than are females. Preputial colonization may have a key role in the selection of such strains.     

Adherence of Escherichia coli and Proteus mirabilis to human transitional cells

This study utilizes a light microscopy assay for bacterial adherence to human male transitional cells. Prior light microscopy studies have used voided squamous cells, periurethral cells or scraped vaginal cells, which are less representative of the cells lining the majority of the urinary tract. Using a modification of previous bacterial adherence assays, the mean adherence for 28 strains of E. coli in 92 bacteria-cell incubations was 10.2 +/- 11.5 (standard deviation) bacteria per cell. The mean adherence for 20 strains of P. mirabilis in 60 bacteria cell incubations was 8.1 +/- 11.4. No statistically significant difference in adherence between E. coli and P. mirabilis was found (p greater than 0.05). Studies comparing the adherence of E. coli isolated from the urine of patients with pyelonephritis (eight strains), cystitis (10 strains) and anal swabs of females without urinary tract infections (10 strains), showed no statistically significant differences in mean adherence (p greater than 0.05). However, there was a trend toward higher adherence in the more virulent groups. Experiments comparing the adherence of P. mirabilis isolated from infected renal stones to P. mirabilis isolated from anal swabs of female patients without history of P. mirabilis UTI revealed no statistically significant differences in mean adherence between the two groups (p greater than 0.05). These data do not support previous contentions that P. mirabilis adhere poorly to human transitional cells. The absence of a significant difference in adherence among strains of E. coli and P. mirabilis that differ in clinical pathogenicity suggests that factors other than adherence contribute to their virulence.     

Urinary Escherichia coli causing recurrent infections--a prospective follow-up of biochemical phenotypes.

Twenty-three women with non-obstructive acute pyelonephritis due to Escherichia coli were prospectively studied during 880 patient months, mean observation time 38 months. Each patient had between 1 and 4 new episodes of E. coli bacteriuria during the study period (altogether 49 recurrencies). All E. coli isolates were typed by biochemical fingerprinting. Twenty-six of the recurrencies were caused by an E. coli strain identical to one of those that had previously appeared. Sixteen of these infections were caused by a strain identical to the one that gave rise to the original acute pyelonephritis. Ten further recurrencies were due to an E. coli strain that had previously caused symptomatic or asymptomatic bacteriuria during the observation period. Despite appropriate treatment and repeated negative urine cultures post-treatment, infections caused by identical E. coli strains occurred up to 35 months after the initial episode of acute pyelonephritis. We suggest that the infecting E. coli strain may survive in the fecal flora or is harboured in the patient's surroundings, and after recolonizing the patient, these strains may give rise to further urinary tract infections.     

Tamm-Horsfall protein knockout mice are more prone to urinary tract infection: rapid communication

BACKGROUND: Human colon contains many bacteria that commonly colonize the perineum and frequently enter the urinary tract. Uropathogenic Escherichia coli are the most common cause of urinary tract infection. Type 1 fimbriated E. coli have been associated with cystitis, and P fimbriated E. coli with pyelonephritis. Factors involved in clearing bacteria from the urinary tract are poorly understood. Tamm-Horsfall protein (THP), the most abundant protein in mammalian urine, has been postulated to play a role in defense against urinary tract infection but definitive proof for this idea has been lacking. METHODS: In this study, we generated THP gene knockout mice by the technique of homologous recombination, and examined if the THP-deficient (THP-/-) mice were more prone to urinary tract infection. Various strains of E. coli expressing type 1 or P fimbriae were introduced transurethrally into the bladders of the THP-/- and genetically similar wild-type (THP+/+) mice. Urine, bladder, and kidney tissues were obtained from the mice and cultured for bacterial growth. RESULTS: THP-/- mice inoculated with type 1 fimbriated E. coli had a longer duration of bacteriuria, and more intense colonization of the urinary bladder in comparison with THP+/+ mice. When inoculated with a P fimbriated strain of E. coli, the THP-/- mice showed no difference in kidney bacterial load when compared with the THP+/+ mice. CONCLUSION: These findings support the idea that THP serves as a soluble receptor for type 1 fimbriated E. coli and helps eliminate bacteria from the urinary tract.     

The effect of E coli virulence on bacterial translocation and systemic sepsis in the neonatal rabbit model

In the surgical neonate, three factors that promote bacterial translocation and systemic infection are: (1) intestinal bacterial colonization and overgrowth; (2) compromised host defenses; and (3) disruption of the mucosal epithelial barrier. The newborn rabbit provides an excellent model to study these factors. Like the human, there is early closure of the gut mucosa to macromolecules, and nutrition can be maintained by breast or formula feeding. This study examines translocation and systemic sepsis after colonization with virulent K1 and avirulent K100 strains of Escherichia coli. New Zealand white rabbit pups (2 to 5 days old) were studied. The gastrointestinal tracts of 12 were colonized with K1 E coli; 14 were colonized with K100 E coli; 12 control animals were not inoculated. Mesenteric lymph node (MLN), liver, spleen, and colon homogenate were cultured 72 hours postinoculation. No bacteria were isolated from the colons of all but one control animal. Translocation or systemic sepsis did not occur. Translocation to the MLN was significantly increased (P less than .03) in K1 (50%) and K100 (36%) groups compared with controls (0%). Translocation to liver and spleen (systemic sepsis) was significantly increased (P less than .03) in K1 animals (67%) compared with K100 (0%) or controls (0%). Colonization by both strains of E coli led to translocation to the MLN, but only K1 E coli caused systemic sepsis. This suggests that although colonization by E coli in the newborn leads to translocation to the MLN, progression to systemic sepsis is the result of characteristics of the bacteria and/or neonatal host responses.     

Renal Allograft Injury Is Associated with Urinary Tract Infection Caused by Escherichia coli Bearing Adherence Factors

Urinary tract infections are the most common infection in renal transplant patients and Escherichia coli (E. coli) is the most common clinical isolate. Although acute allograft injury (AAI) secondary to urinary tract infection (UTI) has been reported, the incidence of AAI associated with UTI, the virulence factors express by uropathic E. coli and whether virulence factors are associated with renal allograft outcome have not been described. We collected E. coli from our renal transplant patients with UTI, determined O:H serotypes, P and Dr fimbriae expression and the clinical presentation and allograft function during the UTI and post-UTI period. Pyelonephritis occurred in 40% of our patients, 82% of which had AAI (>20% increase in SCr). Sixty-two percent of E. coli isolates that expressed P fimbriae were associated with AAI, whereas only 29% that did not express P fimbriae had AAI (p = 0.03). The pattern of P fimbriae and O serotypes differed from reported isolates, as the P fimbriae PapG class II and the O25 serotype were the most common. Dr adhesin was expressed on 7 isolates, including 2 of 3 with urosepsis. We propose a unique pattern of uropathogenic serotypes and adherence factors contribute to acute allograft injury in renal transplant patients with UTI.     

The presence of the virulence island containing the usp gene in uropathogenic Escherichia coli is associated with urinary tract infection in an experimental mouse model

PURPOSE: A putative virulence island commonly noted in the genome of uropathogenic Escherichia coli strains has recently been reported. We have observed that the island includes a gene consisting of a protein designated uropathogenic specific protein (usp) and 3 small open reading frames (orfU1-3). In our current study we assessed the importance of the genes located in the putative virulence island in the pathogenesis of urinary tract infection using a mouse pyelonephritis model. MATERIALS AND METHODS: A total of 427 E. coli strains isolated from the urine of 194, 76 and 107 subjects suffering from cystitis, pyelonephritis and prostatitis, respectively, and 50 isolates from the feces of healthy individuals were examined for genotypes and serotypes. In addition, several recombinant E. coli strains possessing usp and/or orfU1 to 3 were constructed for evaluating the significance of these genes using an experimental pyelonephritis mouse model. RESULTS: The usp was significantly more often associated with uropathogenic E. coli strains (79.4% from cystitis, 93.4% from pyelonephritis and 88.8% from prostatitis) than with fecal E. coli strains from healthy individuals (24%). Furthermore, usp was frequently associated with all common serotypes of uropathogenic E. coli (71.7% to 100%). In challenge experiments using the mouse urinary tract infection model the vector possessing usp significantly enhanced the infectibility of the E. coli host cell, whereas the 3 small proteins at the downstream of usp failed to show the effect. CONCLUSION: Our results indicate that usp may contribute to the causation of urinary tract infection and may be considered a major virulence determinant of uropathogenic E. coli.     

Virulence factors of Escherichia coli contribute to acute renal failure

BACKGROUND: The development of acute renal failure (ARF) significantly enhances the mortality of patients with Gram-negative septic shock. The role of specific bacterial virulence factors different from lipopolysaccharides (LPS) in the deterioration of renal function in septic shock remains to be determined. METHODS: An Escherichia coli wild-type strain (536/21 WT, O6:K15:H31) was isolated from a patient suffering from a urinary tract infection. The strain expresses various virulence factors (e.g. hemolysin, fimbriae) genetically encoded by pathogenicity islands. The spontaneous deletion mutant 536/21 Del lacks the expression of these virulence factors. Isolated rat kidneys were perfused with a suspension (5 x 10(4)/ml) of the respective strain or control perfusion medium and the renal functional parameters were analyzed. Intrarenal deposition of E. coli was detected by immunohistology and Gram staining. RESULTS: The perfusion of the isolated perfused rat kidney with a uropathogenic E. coli wild-type strain (536/21 WT) caused an acute deterioration of renal function which was not observed in kidneys exposed to a deletion mutant of E. coli 536/21 lacking the expression of virulence factors. The glomerular filtration rate and the urine flow rate significantly decreased only in kidneys perfused with the E. coli wild-type strain, while there was no change versus controls in kidneys perfused with the deletion mutant. CONCLUSIONS: Distinctive bacterial virulence factors different from LPS such as hemolysin and the presence of different fimbriae may contribute to the development of ARF in sepsis induced by E. coli. Anti-LPS strategies may not be sufficient to reduce the risk of ARF in Gram-negative septic shock.     

Bacterial interference for prevention of urinary tract infection: an overview

Urinary tract infection (UTI) is the most common infection in patients with spinal cord injury (SCI) and is a major cause of morbidity and mortality in this population. The bladders of patients with SCI, particularly those with indwelling bladder catheters, can become colonized by a variety of organisms, including those that may, and others that may not, cause symptoms of infection. The latter group of bacteria, so-called benign colonizers, are often left untreated because they may provide some protection against symptomatic infection with more pathogenic bacteria. In recent years, deliberate urogenital tract colonization with benign bacterial strains was studied with the objective of offering some protection against invasion by uropathogenic strains. When well-characterized strains of Lactobacillus sp. were used to colonize the vagina of women prone to frequent UTI, a moderate reduction in the rate of recurrent UTI was observed. In other studies, a non-pathogenic prototype of Escherichia coli (strain 83,972) causing asymptomatic bacteriuria was used for deliberate bladder colonization. These preliminary observations encourage the examination of the safety and preventive efficacy of this approach in human subjects.     

Bacterial Interference for Prevention of Urinary Tract Infection: An Overview

Abstract

Urinary tract infection (UTI) is the most common infection in patients with spinal cord injury (SCI) and is a major cause of morbidity and mortality in this population. The bladders of patients with SCI, particularly those with indwelling bladder catheters, can become colonized by a variety of organisms, including those that may, and others that may not, cause symptoms of infection. The latter group of bacteria, so-called benign colonizers, are often left untreated because they may provide some protection against symptomatic infection with more pathogenic bacteria. In recent years, deliberate urogenital tract colonization with benign bacterial strains was studied with the objective of offering some protection against invasion by uropathogenic strains. When well-characterized strains of Lactobacillus sp. were used to colonize the vagina of women prone to frequent UTI, a moderate reduction in the rate of recurrent UTI was observed. In other studies, a non-pathogenic prototype of Escherichia coli (strain 83972) causing asymptomatic bacteriuria was used for deliberate bladder colonization. These preliminary observations encourage the examination of the safety and preventive efficacy of this approach in human subjects.     

Characterization of Escherichia coli strains causing urinary tract infections in patients with transposed intestinal segments

PURPOSE: Transposition of intestinal segments into the urinary tract predisposes to urinary tract infections. We characterized bacterial infections in these patients and examined the virulence genotype and persistence of Escherichia coli isolates. MATERIALS AND METHODS: We followed 26 patients who underwent bladder reconstructive surgery using transposed intestinal segments. E. coli strains isolated from the urine of these patients were genotyped for established virulence determinants and the frequency of carriage was compared with E. coli strains isolated from community acquired urinary infections and the fecal flora of anonymous volunteers. A longitudinal study of E. coli strains in 9 patients was also done using pulsed field gel electrophoresis. RESULTS: E. coli was the most frequently isolated organism, responsible for 59% (62 of 105) of monobacterial infections. Other bacteria isolated included Klebsiella species, Proteus species and Enterococcus faecalis. Community acquired E. coli strains were more likely to carry multiple determinants for particular adhesins (P and S fimbriae) and toxins (alpha-hemolysin and cytotoxic necrotizing factor) than fecal strains. Carriage frequency for bladder reconstruction strains was intermediary and not significantly different. The key finding was that E. coli strains persisted for prolonged periods, including 2 years in certain patients, often despite various antimicrobial treatments. CONCLUSIONS: This study highlights that further steps must be taken to prevent and treat urinary tract infections in this susceptible group. Particular attention should be given to the treatment of persistent infections.     

Type 1 fimbriate strains of Escherichia coli initiate renal parenchymal scarring

The renal scarring which characterizes chronic pyelonephritis is initiated by bacterial infection and is independent on the activation of an inflammatory response. Although the presence of polymorphonuclear leukocytes (PMN) is essential for initiating the scarring process, the bacterial structures responsible for their activation have not been investigated. In an animal model of chronic pyelonephritis the surface area of the renal scars produced by Type 1 fimbriate escherichia coli (E. coli) was significantly greater than that of those produced by P fimbriate and non-fimbriate strains (P less than 0.01). The activation of human PMN by the same Type 1 fimbriate organisms resulted in a significant release of lysosomal neutral protease activity (P less than 0.001) and activation of the respiratory burst (P less than 0.01). The neutral protease release in response to P fimbriate and non-fimbriate organisms was not significantly increased. The extent of renal scarring also correlated with the release of neutral protease activity (P less than 0.02) and with the degree of activation of the respiratory burst (P less than 0.05). These results demonstrate that the ability of E. coli strains to cause renal scars may be related to their capacity to express Type 1 fimbria, which may be a causative factor in the in vivo activation of the inflammatory response.     

THE SIGNIFICANCE OF THE DIFFERENCE IN BACTERIAL ADHERENCE BETWEEN BLADDER AND ILEUM USING RAT ILEAL AUGMENTED BLADDER

OBJECTIVES: Intestinal segments are frequently used in the reconstruction of the urinary tract. Chronic bacteriuria is frequently observed in these patients, but the reason is not clearly understood. Therefore, we studied the difference in bacterial adherence between bladder and ileum using the rat ileal augmented bladder model to investigate the cause of chronic bacteriuria. MATERIALS AND METHODS: Augmentation of the bladder using ileum and a sham operation were performed under sodium pentobarbital in 102 and 10 Sprague-Dawley rats, respectively. At three months after the operation, urinary pH and plasma concentration of sodium, chloride and potassium were measured and urinary culture was done. Urovirulence factors of Escherichia coli aspirated from augmented bladder were detected by polymerase chain reaction (PCR). Five to six rats with negative urinary cultures after the augmentation were used for each experimental cystitis. E. coli with type I pili aspirated from augmented rats and three clinically isolated strains of E. coli, C5 (type I pili, aerobactin), C92 (type I pili, aerobactin, P fimbriae), and C189 (type I pili, aerobactin, P fimbriae, CNF), were transurethrally inoculated into the augmented bladder of rats. Fourteen days after inoculation, rats were sacrificed and colony-forming units (CFU) per mg. of tissue of bladder and ileum were measured. RESULTS: After operation, urinary pH and the serum level of chloride in all augmented groups were higher than those of the controls. Bacterial colonization was observed in 56 of 89 rats. Most of them were E. coli having only type I pili as a virulence factor. In contrast, the sham operated group revealed no bacterial colonization. In experimental cystitis, E. coli with only type I pili aspirated from augmented rats and E. coli C5 were clearly adhered to ileum rather than to bladder, but E. coli C92 and C189 showed no significant difference with respect to adherence to the two tissues. In experimental cystitis II, E. coli C5 with D-mannose were washed out in 3 of 5 rats by 14 days, while E. coli C5 without D-mannose were not washed out in all rats by 14 days. CONCLUSIONS: These results suggested that the difference in bacterial adherence due to urovirulence factors, especially type I pili, is one of the main causes of asymptomatic bacteriuria after urinary reconstruction.