Ascending, unobstructed urinary tract infection in mice caused by pyelonephritogenic Escherichia coli of human origin

Bacterial adherence in urinary tract infections: preliminary studies in a primate model

Escherichia coli with both P and type 1 fimbriae caused vaginal colonization in the female green monkey, while only the P-fimbriated bacteria frequently caused ascending bladder infection. Bladder inoculation caused only short-lived bladder infection from type 1 fimbriated E. coli, but those with P-fimbriae caused acute pyelonephritis even in the absence of vesicoureteral reflux. Thus, type 1 fimbriae of E. coli, while causing vaginal colonization, did not often cause ascending infection in the non-compromised host as did P-fimbriated bacteria.

Interleukin-6 induced at mucosal surfaces by gram-negative bacterial infection

Interleukin-6 (IL-6) was produced in response to mucosal and systemic infection of mice with gram-negative bacteria. The IL-6 response was controlled by the lipopolysaccharide gene, Lps; in C3H/HeN mice (Lpsn/Lpsn), the urinary IL-6 levels increased within 30 min after challenge with Escherichia coli, but no response occurred in C3H/HeJ mice (Lpsd/Lpsd). In lipopolysaccharide-responder mice, the levels of local and systemic IL-6 were related to the degree of infection. The urinary response dominated after intravesical challenge, and the serum response dominated after intraperitoneal challenge. The results demonstrate that IL-6 is activated as part of lipopolysaccharide-induced mucosal and systemic responses to gram-negative bacterial infections.

P-fimbriae vaccines. I. Cross reactive antibodies to heterologous P-fimbriae

To test for cross-protective capacity of two different P-fimbriae vaccines we vaccinated baboons with fimbriae purified from either Escherichia coli strain ER2 or strain JR1. The vaccinated animals showed elevated antibody titers to P-fimbriae from each of the E. coli strains used, suggesting cross-reactivity as was expected from the results of immunoprecipitation of the fimbriae. Enzyme-linked immunosorbent assay inhibition by heterologous P-fimbriae proved this to be true immunologic cross-reactivity.

Binding characteristics of Escherichia coli adhesins in human urinary bladder

We studied domains in the human bladder that acted as receptors for Escherichia coli P, S, type 1, type 1C, and O75X fimbriae or adhesin and domains in the human kidneys that were receptors for E. coli type 1C fimbriae. Binding sites in frozen tissue sections were localized by direct staining with fluorochrome-labeled recombinant strains and by indirect immunofluorescence with the purified adhesins. In the bladder, the P and S fimbriae showed closely similar binding to the epithelial and muscular layers, and the S fimbriae also bound to the connective tissue elements. Type 1 fimbriae bound to vascular walls and to muscle cells, whereas the O75X adhesin bound avidly to connective tissue elements and to some extent to epithelial and muscle cells of the bladder. The type 1C fimbriae bound to distal tubules and collecting ducts of the kidney and to vascular endothelial cells in both the kidney and bladder. The binding of all adhesin types was inhibited by specific receptor analogs or Fab fragments. The results reveal a possible mechanism by which the type 1C fimbriae may help invasion of E. coli in the kidneys but do not support a pathogenetic role for type 1 fimbriae. Similar tissue specificity of P and S fimbriae in the human urinary tract indicates that the presence of binding sites on uroepithelia does not fully explain the virulence properties of P fimbriae in human urinary tract infections.

Identification of factors in human urine that inhibit the binding of Escherichia coli adhesins

Earlier studies on the binding of Escherichia coli adhesins to the human urinary tract have indicated that the ability to recognize binding sites on the urinary tract epithelial cells is not a characteristic for P fimbriae only, but is also shared by some other adhesins that are not associated with pyelonephritis, especially S fimbriae. In the present study we have investigated whether human urine contains inhibitors of the binding of E. coli adhesins. Normal human urine was found to inhibit hemagglutination by S and type 1 fimbriae but not P fimbriae. The major inhibitor of S fimbriae in normal urine was identified as Tamm-Horsfall glycoprotein, and the interaction with S fimbriae is probably mediated by its sialyloligosaccharide chains. No significant variation was observed in the inhibitory effect of T-H glycoprotein preparations originating from different individuals. In contrast to S fimbriae, the major inhibitors of type 1 fimbriae in urine were identified as low-molecular-weight compounds. Gel filtration and ion-exchange chromatography and alpha-mannosidase treatment indicated that they were neutral alpha-mannosides, probably manno-oligosaccharides with three to five saccharides. Studies of urine samples collected from several individuals indicated the common occurrence of these inhibitory alpha-mannosides. Type 1 fimbriae bound to immobilized T-H glycoprotein, but, unlike S fimbriae, their binding was poorly inhibited by soluble T-H glycoprotein. Some urine samples were also found to contain low-molecular-weight inhibitors for the O75X adhesin of E. coli. These results emphasize that to function as a virulence factor in human urinary tract infections, an adhesin must evidently recognize such receptor structures at the infection sites that are not excreted in soluble form in urine. This prerequisite is filled by P fimbriae but not by type 1 or S fimbriae.

Induction of inflammation by Escherichia coli on the mucosal level: requirement for adherence and endotoxin

Bacterial infection of the mouse urinary tract is followed by the recruitment of leukocytes to the mucosal surface. This study examined the bacterial components involved in the induction of this response. Escherichia coli of serotype O75:K5:H- expressing adhesins specific for the Gal alpha 1-4Gal beta- (Gal, galactose) and mannose-containing receptors were instilled into the urinary bladder of lipopolysaccharide responder (C3H/HcN) and lipopolysaccharide nonresponder (C3H/HeJ) mice. The inflammation was quantitated as the number of leukocytes excreted into the urine at various times after infection. The response was first shown to depend on the Lps genotype of the mouse. The leukocyte excretion that occurred within 24 h after infection of C3H/HeN mice was absent in C3H/HeJ mice. The components triggering the response were present on both live and Formalin-killed bacterial cells, and the response was mimicked by intravesical inoculation of isolated lipid A. Pretreatment of bacteria with soluble receptor oligosaccharides resulted in inhibition of attachment in vitro and of the inflammation in vivo. A direct synergy between adhesins specific for Gal alpha 1-4Gal beta receptors and lipid A was demonstrated. Mixtures of these components induced a leukocyte response higher than the sum of the responses to each component alone. These results suggest that the inflammation induced by gram-negative bacteria in the urinary tract can be triggered at the level of the epithelial cells by endotoxin presented by an attaching bacterial cell and that intact function at the Lps locus of the host is required for this to occur.

Interaction of Escherichia coli with polymorphonuclear leukocytes in pathogenesis of urinary tract infection in mice

Two type 1 fimbria-producing strains of Escherichia coli, 31-B and K12W1-3, and two type 1 fimbriae-defective mutants derived from 31-B, BH5 and BH9, were compared for their capacity to induce vesical infection in mice undergoing water diuresis and to interact in vitro with murine peritoneal exudate polymorphonuclear leukocytes (PMN). Strains 31-B and BH5 caused rapid bacterial multiplication in the bladder wall after being inoculated intrabladderly; their log-phase cells grown at 37 degrees C, in striking contrast to their stationary-phase or 17 degrees C-grown cells, resisted phagocytic killing by PMN in the presence of normal murine serum. Strains K12W1-3 and BH9 failed to cause vesical infection, and their cells were always susceptible to the opsonophagocytic killing by PMN irrespective of the growth conditions. Nevertheless, the log-phase cells of the three isogenic strains, 31-B, BH5, and BH9, grown at 37 degrees C gave almost the same chemiluminescent response patterns during incubation with PMN in normal serum. The phagocytic resistance in strains 31-B and BH5 was eliminated by briefly treating bacterial cells with EDTA. These results suggest that the two virulent strains may express an antiphagocytic activity during their growth in the bladder and continue to stimulate the oxidative metabolic burst of PMN without being ingested and killed, and that the antiphagocytic activity may be related to a bacterial surface component(s) that is removed by EDTA.

A block of urovirulence genes encoding multiple fimbriae and hemolysin in Escherichia coli O4:K12:H-

Cosmid gene libraries were constructed from a uropathogenic isolate of Escherichia coli O4:K12:H- that secretes alpha-hemolysin and produces the F14, F12-rel, F1C, and F13 fimbrial antigens. A series of overlapping clones was generated, and individual cosmid clones were found to express various combinations of fimbriae and hemolysin, suggesting that the genes for these potential virulence factors are closely linked. By using Southern hybridization analysis and restriction endonuclease mapping, it was demonstrated that the cosmid clones carried a nested set of overlapping, cloned, genomic DNA fragments. A comparison of the phenotypic properties of individual cosmid clones and subclones allowed the order of the gene clusters encoding these factors to be deduced. The cloning also revealed the presence of a fifth fimbria that had P-adhesin specificity.

Synthetic peptides corresponding to protective epitopes of Escherichia coli digalactoside-binding pilin prevent infection in a murine pyelonephritis model

Synthetic peptides corresponding to five segments of a globoside (Gal-Gal)-binding pilin sequence [residues 5-12 (R5-12), R65-75, R93-104, R103-116, and R131-143], cyanogen bromide fragment II (CNBr-II, R53-163), and purified, intact Gal-Gal pili were prepared as vaccines and tested for their efficacy in a BALB/c murine model of pyelonephritis. Intact Gal-Gal pili, CNBr-II, and synthetic peptides R5-12 and R65-75 engendered antibodies that bound the homologous pilin protein and prevented urine and renal colonization in most vaccine recipients. Protection correlated with serum anti-pilus IgG ELISA titers greater than or equal to 1:250. The efficacy afforded by synthetic peptides R5-12 and R65-75 in vaccinated mice indicates that linear "antigenic" determinants in separate cyanogen bromide fragments encode "protective" epitopes. Peptides R93-104, R103-116, and R131-143 lacked efficacy, indicating that not all regions of the sequence are serologically equivalent. The crossreactivity of the peptide antisera for different Gal-Gal pilins was also assessed and correlated with the sequence homology of the corresponding regions. Antiserum to peptide R65-75, which corresponds to a region of unconserved sequence in heterologous pilins, bound only the homologous pilin. Thus, it specifies a type-specific protective epitope. Antiserum to synthetic peptide R5-12, which corresponds to a region of conserved sequence, bound Gal-Gal pilins from seven of eight pyelonephritis strains, indicating that it specifies a crossreacting protective epitope.

The ecology and pathogenicity of urease-producing bacteria in the urinary tract

Urease activity is a physiological function of many bacteria that enables these organisms to utilize urea as a source of nitrogen. The association of ureolytic bacteria with human or animal hosts varies widely from a commensal relationship as demonstrated with skin microflora, a symbiotic relationship in the gastrointestinal tract, to a pathogenic relationship in the urinary tract. Since similar or identical species of bacteria such as Staphylococcus aureus are found in all three environments, the effect of urease activity on the host must be solely a function of the environment of these organisms. In this review, the importance of urease to bacteria is discussed, identifying the gastrointestinal tract as a major reservoir of ureolytic bacteria and investigating the urinary tract environment and the infectious struvite stone production that often accompanies urease-producing bacteria there. Finally, an infection model is presented which explains the development and growth of these urinary calculi and their remarkable persistence in spite of modern urological treatments.

Ascending urinary tract infections in rats induced by Staphylococcus saprophyticus and Proteus mirabilis

Ascending pyelonephritis was induced by Staphylococcus saprophyticus and Proteus mirabilis both by inoculating the organisms separately and in combination into rat bladders. Bacterial cultures of tissue homogenates showed that pyelonephritis by both bacteria occurred significantly more often in rats where the two organisms were instilled concomitantly, suggesting a synergistic virulence between the two species. The antibody response to the different organisms was the same either the bacteria were instilled separately or in combination.

Expression of type 1 fimbriae may be required for persistence of Escherichia coli in the catheterized urinary tract

Long-term urinary catheterization results in polymicrobial bacteriuria and is complicated by fever, bacteremia, acute pyelonephritis, and death. Escherichia coli is a common urine isolate from catheterized patients and can persist for months. We hypothesized that fimbria-mediated adherence contributes to its persistence. For 1 year, urine specimens were collected from 51 patients greater than or equal to 65 years of age who were catheterized for greater than or equal to 30 days. E. coli was isolated at greater than or equal to 10(5) CFU/ml from 447 (36%) of 1,230 weekly urine specimens from 26 patients. Week 1 isolates from 52 definable episodes were tested for hemagglutination, hybridization with gene sequences from the pil and pap operons, in vitro adherence to catheter material, binding of 125I-labeled Tamm-Horsfall protein, hemolysin and colicin V production, and serum resistance. The proportions of isolates of short (1 week only), medium (2 to 11 weeks) and long (greater than or equal to 12 weeks) episodes of bacteriuria which expressed type 1 fimbriae as assayed by mannose-sensitive hemagglutination were 59, 65, and 92%, respectively. Isolates with the pil operon (the genome for type 1 fimbriae) from episodes lasting greater than 1 week expressed mannose-sensitive hemagglutination more frequently (P = 0.011) than pil-positive isolates from episodes of less than or equal to 1 week. Isolates from episodes of greater than 1 week also bound significantly more Tamm-Horsfall protein than isolates from episodes of less than or equal to 1 week (P = 0.044). Although nearly half of the isolates produced P fimbriae, an important virulence factor for the development of pyelonephritis, no correlation with persistence could be made. Overall, the E. coli isolates expressed traits similar to those of strains that caused cystitis. Type 1 fimbriae appear to be important for the persistence of E. coli in the long-term-catheterized urinary tract.

Host parasite interaction in urinary tract infection

The last decade has provided new insight into the mechanisms of host-parasite interactions in the urinary tract. Reduction of host resistance appears to reduce the requirement for bacterial virulence, whereas the resistant host becomes infected with bacteria of high virulence. In the resistant host, bacterial virulence can be defined as the sum of properties required to colonize the urinary tract and induce tissue reactions. The ability to attach to uroepithelial cells is the single property most frequently associated with pyelonephritogenic clones. Attachment to the Gal alpha 1-4Gal beta-containing receptors promotes localization of bacteria to the kidney and the induction of lipopolysaccharide-mediated inflammation. Other virulence factors, defined by increased frequency in acute pyelonephritis compared with asymptomatic bacteriuria, include haemolysin and aerobactin production. Among the factors which influence the natural resistance to urinary tract infection are urinary flow and reactivity to endotoxin. The resistance induced by natural exposure to infection or immunization may be protective in experimental models, but the importance of this is not yet defined. The localization, severity and sequelae of urinary tract infection are determined by the balance between bacterial virulence and host resistance. Although disease is a result of the interaction between bacterial virulence and host resistance, these components are discussed separately for clarity.

Uropathogenicity in rats and mice of Providencia stuartii from long-term catheterized patients

Providencia stuartii, a frequent and persistent isolate from the urinary tract of chronically catheterized elderly patients, is multiply antibiotic resistant and may cause fatal bacteremia in those patients. We studied P. stuartii strains in rats and mice to determine differences in uropathogenicity. Strains studied varied in expression of factors which contribute to pathogenicity of other bacterial species. Urinary tract responses following challenge with P. stuartii strain HO (factors expressed) were similar to responses reported for uropathogenic E. coli strains both in bacterial persistence and histologic change. In animals similarly challenged with P. stuartii strain RO (factors not expressed), responses were similar to those reported for non-uropathogenic E. coli strains. Results indicate that: a) animal model studies may be useful in differentiating P. stuartii strains based on uropathogenicity, b) P. stuartii uropathogenicity may be related to identifiable factors associated with virulence in other species, and c) the CBA mouse model appears to be the most suitable for studies of P. stuartii uropathogenicity.

The PapG protein is the alpha-D-galactopyranosyl-(1----4)-beta-D-galactopyranose-binding adhesin of uropathogenic Escherichia coli

Uropathogenic Escherichia coli adhere to uroepithelial cells by their digalactoside alpha-D-galactopyranosyl-(1----4)-beta-D-galactopyranose [alpha-D-Galp-(1----4)-beta-D-Galp or Gal alpha (1----4)Gal]-binding pili, which are composed of repeating identical subunits. The major subunit (PapA) of these pili is not required for binding, but the papF and papG gene products are essential for adhesion. Transcomplementation analysis between the pap gene cluster and a related gene cluster encoding a different binding specificity showed that PapG and not PapF is the Gal alpha (1----4)Gal-specific adhesin. Antibodies against PapG were obtained upon immunizing with whole Pap pili, showing that the adhesin is a pilus component. Antisera specific for different Pap proteins were used to demonstrate that a pilin protein, either PapA or PapE, together with both PapG and PapF, must be exposed on the cell surface to allow E. coli to bind. The DNA sequence of the papG gene is presented, and the deduced primary structure showed similarities both to the B-chain sequence of the digalactoside-binding Shigella toxin and to established amino acid sequences of pilins.

Effect of immunization with Escherichia coli K1 antigen on the course of experimental infection of the urinary tract of the rat

The influence of vaccination with an immunogenic K1 antigen of Escherichia coli on the course of pyelonephritis induced experimentally in rats by infection with Escherichia coli O2:K1:H4 was investigated. The immunogenic properties of K1 antigen are poor. A conjugate of K1 antigen with bovine serum albumin (BSA) was therefore tested. Preliminary experiments showed that the K1-BSA conjugate is immunogenic. Renal inflammatory activity in rats after retrograde infection was significantly reduced after vaccination of the animals with K1-BSA conjugate within six weeks of infection.

Bacterial virulence versus host resistance in the urinary tracts of mice

The relative contributions of host resistance and bacterial virulence were analyzed in a mouse model for ascending urinary tract infection. The congenic mouse strains C3H/HeJ and C3H/HeN were used in parallel. They differ in their reactivity to lipopolysaccharide (LPS) and susceptibility to experimental urinary tract infection. C3H/HeJ cells are susceptible to infection and are nonresponders to LPS (Lpsd Lpsd), whereas C3H/HeN cells respond to LPS and are resistant to infection (Lpsn Lpsn). The Escherichia coli pyelonephritis isolate GR-12, serotype O75K5, expressing adhesins specific for globoseries glycolipids (P fimbriae) and for mannosides (type-1 fimbriae), and its derivatives deficient in these factors were used, either singly or in combination, to establish experimental infections. In C3H/HeN mice, the relative persistence of E. coli was inversely proportional to its phagocytosis in vitro. Loss of the O75 and K5 antigens increased the tendency toward hydrophobic interaction, promoted phagocytosis, and reduced persistence in the kidneys. This was not the case in C3H/HeJ mice, in which O75- and K5- serotypes persisted in the same extent as did the parent strain. The total number of bacteria recovered from the kidneys of C3H/HeJ mice was about 1,000-fold higher than the number recovered from kidneys of C3H/HeN mice 24 h after infection. Previous studies have demonstrated a delayed influx of polymorphonuclear leukocytes into the urinary tracts of C3H/HeJ mice. The results are consistent with the hypothesis that phagocyte activation through LPS is a major defense mechanism against E. coli in the kidney, a property in which C3H/HeJ mice are deficient.

Relationship of type 1 pilus expression in Escherichia coli to ascending urinary tract infections in mice

The role of type 1 pili and P adhesins during the in vivo growth of Escherichia coli inoculated into the urethras of BALB/c mice was studied. Strains which produced type 1 pili when grown in broth but lost this trait when grown on agar (regulated variants) were tested. Broth-grown organisms colonized the bladder of every animal tested, with counts of 10(3) to 10(4) viable organisms recovered from bladder homogenates. Agar-grown organisms gave lower rates of infection and the number of viable organisms recovered from bladders was significantly reduced. The degree of inoculum piliation influenced bladder colonization in a direct way: as piliation increased, the number of bacteria recovered from bladders also increased. After intraurethral inoculation, all of the bladders and 44% of the kidneys were colonized on day 1, and by day 5, 94% of the bladders and 16% of the kidneys were positive. Hemagglutination titers remained high for the bladder isolates, but the organisms colonizing the kidneys became significantly less piliated with time. Bacteriuria was unrelated to bladder or renal colonization. Strains that demonstrated random phase variation of type 1 pili during growth on agar produced similar colonizations of the urinary tract with broth- and agar-grown inocula. Strains that produced only P adhesins were less effective in colonizing the urinary tract than were type 1 piliated organisms. Other strains which did not produce pili only minimally colonized the bladder. The results suggest that type 1 pili play an essential role in ascending infections of the urinary tract.

Interaction of a pyelonephritogenic Escherichia coli strain with the tissue components of the mouse urinary tract

Immediately following the introduction of cells of a pyelonephritogenic strain of Escherichia coli (expressing both GS and MS adhesins) into the mouse bladder, these cells were found to be randomly distributed on the mucosal surfaces of both the bladder and the kidney. After 24 hr. these adherent bacterial cells had proliferated to form nonrandomly distributed adherent microcolonies on both mucosal surfaces and large masses within the renal ducts. Large amounts of amorphous material, which we presume to be of both host and bacterial origin, was associated with the bacterial microcolonies on the infected tissues. The removal of urinary slime and tissue coat material by acid pretreatment increased both the degree and the apparent avidity of bacterial adhesion to the bladder mucosa. The adherent bacteria on the bladder mucosa were radically elongated, while those on the kidney mucosa usually retained their short rod-like morphological characteristics. These data suggest that pyelonephritogenic bacteria adhere to mucosal surfaces in both the bladder and kidney, and proliferate to form adherent microcolonies within which bacteria are associated with large amounts of amorphous extracellular material.

Experimental haematogenous pyelonephritis in mice with uropathogenic, enteropathogenic and enterotoxigenic Escherichia coli

Acute haematogenous pyelonephritis was produced with known uropathogenic (075), enteropathogenic (0111) and enterotoxigenic (H10407) Escherichia coli in mice. The enterotoxigenic E. coli showed the highest bacterial counts in kidney and urine and was found to have the same potential for causing pyelonephritis as a known pyelonephritogenic strain both in untreated and corticosteroid treated mice. Enteropathogenic E. coli was found to be less pyelonephritogenic in untreated mice, but under the effect of corticosteroids it showed similar pyelonephritogenic potential.

Escherichia coli in extra-intestinal infections

When Theodor Escherich (1885a, b) first describedEscherichia colihe looked on it as a saprophytic organism. Soon several investigators found that colibacteria could be isolated from intestinal infections and from many infections outside the intestine, like urinary tract infections (UTI), cholecystitis, wound infections, meningitis, septicaemia, pulmonary infections, and many more. Uhlenhuth (1897) showed that coli strains from pathological processes were more pathogenic in animal experiments than strains isolated from the normal intestine. Smith (1927), who examined strains from white scours in calves, showed that spontaneous acapsular mutants could be obtained from certain colibacteria, and that such mutants were less virulent when injected intra-peritoneally into guinea-pigs.

Role of type 1 pili and effects of phase variation on lower urinary tract infections produced by Escherichia coli

Phase variation of type 1 pili (fimbriae) was studied during the in vivo growth of Escherichia coli in two animal models. In the first, a heavily piliated urinary tract isolate (strain 149) was placed in 1-cm polypropylene chambers sealed with 0.22-micron-pore-size filters. The chambers were surgically implanted intraperitoneally in mice and recovered at various times. Piliation, as determined by electron microscopy and by measuring the minimum number of bacteria needed to produce mannose-sensitive hemagglutination, gradually decreased, and by day 5, most of the organisms were nonpiliated. In the second model, piliated and nonpiliated E. coli phase variants were inoculated into the bladders of BALB/c mice via urinary catheters, and their fate in the lower urinary tract was studied. Viable counts of bladder homogenates revealed that piliated phase variants were significantly more effective in colonizing the bladder urothelium than were their nonpiliated counterparts. Specific antibody to type 1 pili prevented colonization by the piliated organisms. After inoculation of piliated variants, the bladder-associated bacteria gave rise to approximately 80% mannose-sensitive hemagglutination-positive colonies, and immunocytochemistry of bladder lavages revealed large numbers of type 1 piliated bacteria adhering to the bladder transitional cells. Electron microscopy confirmed the presence of piliated bacteria in association with the bladder urothelium. The urine of these mice, whose bladders were colonized with piliated bacteria, frequently showed no growth, and when bacteria were present, strain 149 yielded less than 30% hemagglutination-positive colonies. The results suggest that for some E. coli strains, phase variation may be a factor in determining the fate of the E. coli in the urinary tract and that the urine may not necessarily reflect the bacteriologic state of the bladder mucosa.

Comparison of the antibacterial effect of uroepithelial cells from healthy donors and children with asymptomatic bacteriuria

Bacterial attachment to uroepithelial cells (UEC) and the effect of UEC on bacterial growth was investigated in 15 healthy persons and 12 patients suffering from asymptomatic bacteriuria (ABU) with recurrent urinary tract infections (UTI). Desquamated UEC and mannose-resistant Escherichia coli were co-cultivated for up to 90 min. While no difference in bacterial adherence was observed between healthy controls and patients, 33.4% of the bacteria attached to normal UEC were found to be dead under microscopic evaluation (acridine orange staining), whereas no killing effect could be observed in patients' UEC 5 min after the onset of incubation. This phenomenon was confirmed by investigating the E. coli growth rate in the presence of UEC, measured by counting bacterial colony forming units (CFU) on agar plates. While E. coli showed exponential growth in RPMI medium, the addition of normal UEC suppressed bacterial growth (P less than 0.01). UEC from patients with ABU, however, did not show this effect. It has been concluded that bacterial adhesion may initiate an epithelial defence function, present in healthy controls and lacking in ABU patients.

Prevention of urinary tract infection in rats with an indigenous Lactobacillus casei strain

Our previous studies have shown that indigenous bacteria are able to block the in vitro attachment of uropathogenic bacteria to human uroepithelial cells. In the present study, we applied the concept of competitive exclusion to an animal model. A chronic urinary tract infection was established in female rats with bacteria incorporated into agar beads injected periurethrally into the urinary bladder via a no. 3 French ureteral catheter. Five strains of uropathogenic organisms were used in the first set of experiments, and their colonization of the bladder and kidneys of the animals was confirmed up to 2 months after injection. The uropathogens stimulated an immune response, detected by serum antibodies against the uropathogens, and an inflammatory response noted in sections of the kidneys stained with hematoxylin and eosin. Using this animal model, we established the persistent adherence of bacteria in the urinary tract without the need for creation of obstruction or implantation of a foreign body. In a second set of experiments, an isolate of Lactobacillus casei GR1 taken from the urethra of a healthy woman was incorporated into agar beads, instilled within the rat bladders on day 1, and then swabbed twice weekly for 21 days onto the introitus before challenge with uropathogens instilled into the urinary bladder. In 21 of 25 animals, no uropathogenic bacteria were recovered from the bladder and kidney tissues up to 60 days after challenge, and no immune response was detected. Our results show that L. casei prevented onset of urinary tract infection in 84% of the animals tested. The lactobacilli appeared to exclude the uropathogens from colonizing the urinary tract, within the first 48 hours after challenge, and the net effect was a complete eradication of bacteria from the uroepithelium. It is hoped that the demonstration of a protective role for indigenous bacteria in preventing urinary tract infection in an animal model will lead to the application of this technology to prevent recurrent urinary tract infection in female patients.

Experimental pyelonephritis in the monkey. VII. Ascending pyelonephritis in the absence of vesicoureteral reflux

Six adult male nonrefluxing monkeys were experimentally infected by inoculation of P-fimbriated E. coli into the bladder. Eight control monkeys were inoculated with a non-P-fimbriated E. coli strain. Inoculation with the P-fimbriated E. coli resulted in marked leukocytosis, prolonged bacteriuria and loss of renal function with a 66 per cent incidence of pyelonephritis. Death secondary to bilateral pyelonephritis was seen in 2 monkeys inoculated with P-fimbriated E. coli. Pyelonephritis was not seen in any of the monkeys inoculated with non-P-fimbriated E. coli. The study shows that ascending pyelonephritis can occur in monkeys in the absence of vesicoureteral reflux.

Non-antibiotic prevention of urinary tract infection

The identification of several glycoconjugates as receptors for attaching bacteria has resulted in optimism regarding the use of receptor analogues in preventing infection. The structure of receptor-active oligosaccharides and the patient groups which might benefit from such treatment are most thoroughly understood for urinary tract infections. Prevention of adhesion and delay or decrease of infection was achieved using oligosaccharides from the globoseries of glycolipids containing Gal alpha 1----4Gal. This minimal receptor structure as a free saccharide was, however, not sufficient. It was the intact P, P1 and pk determinants which showed optimal activity in vitro. In addition, protection against experimental UTI results from previous exposure to whole bacteria or isolated antigens. The mechanism(s) of protection and their relevance in clinical UTI remain to be defined.

Genetic factors in host resistance to urinary tract infection

In patients with recurrent pyelonephritis, the pathogenetic events proceed through intestinal colonization, spread to the urinary tract and persistence, seemingly uninterrupted by host defense mechanisms. The factors responsible for the deficient bacterial clearance from the kidneys of these patients, and the genetic control, have not been identified. The susceptibility to colonization has been linked to an increased receptivity for attaching bacteria of the uroepithelia, and to an overrepresentation of the P1 blood group phenotype. To evaluate the role of defects in host defense for the susceptibility to pyelonephritis, experimental UTI in mouse strains with known deficiencies was used. A highly significant increase in susceptibility was noted for C3H/HeJ compared to C3H/HeN mice. The bacterial recovery was inversely correlated to the mitogenic response to LPS. Back-cross analysis revealed a linkage of susceptibility to the Lpsd/Lpsd genotype. In contrast, T and B lymphocyte and complement (C5) defects had little effect on the clearance of Escherichia coli from the kidneys. It is concluded that the inflammatory mechanisms induced by LPS are essential for resistance to experimental pyelonephritis.

Molecular basis of Escherichia coli colonization of the upper urinary tract in BALB/c mice. Gal-Gal pili immunization prevents Escherichia coli pyelonephritis in the BALB/c mouse model of human pyelonephritis

Most human pyelonephritis Escherichia coli isolates express both mannose (MS)- and globoside (Gal-Gal)-binding pili. An ascending E. coli urinary tract infection model was established in the 16-wk-old female BALB/c mouse to compare the pathogenic significance of MS and Gal-Gal pili and their efficacy as vaccines for the prevention of pyelonephritis. The distribution and density of pilus receptor compounds in urogenital tissues and as soluble compounds in urine were determined with antibodies to the synthetic receptor analogues, alpha D-Gal(1----4) beta D-Gal and alpha D-Man(1----2) alpha D-Man. Both carbohydrates were detected in vagina, bladder, ureter, and renal pelvis epithelium and in collecting duct and tubular cells. A pilus receptor compound also was detected in urine. It competitively inhibited the binding capacity of MS pili and was found to be physically, chemically, and immunologically related to Tamm-Horsfall uromucoid. Infectivity and invasiveness were quantitatively and histologically characterized for four E. coli strains: J96, a human pyelonephritis strain that expresses both MS and Gal-Gal pili; two recombinant strains prepared from J96 chromosomal DNA encoding MS pili or Gal-Gal pili; and the nonpiliated K12 recipient. Intravesicular administration of J96 (10(6) colony-forming units [CFU]) resulted in renal colonization and invasion in each of nine mice. The Gal-Gal clone (10(6) CFU) colonized the kidneys in each of 10 mice but did not invade. In contrast, the MS clone (10(6) CFU) did not colonize renal epithelium or invade. This effect was superceded when larger doses (greater than or equal to 10(10) CFU) of the MS clone were administered in volumes that cause acute vesicoureteric reflux. The efficacy was determined of vaccines composed of pure MS or Gal-Gal pili or the lipopolysaccharide containing O somatic antigen of the challenge strain, J96. The Gal-Gal pilus vaccine blocked renal colonization in 19 of 22 mice and renal invasion in 10 of 11 mice. Gal-Gal pili may be useful immunogens for the prevention of pyelonephritis in anatomically normal urinary tracts.

Difference in susceptibility to gram-negative urinary tract infection between C3H/HeJ and C3H/HeN mice

The difference in susceptibility to urinary tract infection between C3H/HeJ and C3H/HeN mice was tested for with gram-negative strains differing in lipopolysaccharide composition. Recently, impaired clearance of Escherichia coli from the kidney of C3H/HeJ compared to C3H/HeN mice was shown to be correlated with the LPS low responsiveness. In this study, a difference in clearance from the kidneys of C3H/HeJ and C3H/HeN mice was found only with lipopolysaccharide-containing bacteria. Gram-positive bacteria, e.g., Staphylococcus saprophyticus and Streptococcus agalactiae, were recovered in essentially equal numbers from the kidneys of mice of both strains. In contrast, of the lipopolysaccharide-containing strains used, all persisted in higher numbers in the kidneys of C3H/HeJ mice than in the kidneys of C3H/HeN mice. Variations in the O side chain did not eliminate this difference. E. coli Hu734 O75+K5+ and the rfb- mutant O75-K5+ remained in similar numbers in C3H/HeJ mice, although O75-K5+ was eliminated more rapidly in C3H/HeN mice. The core structure did not affect the differential persistence in the two mouse strains. The rfb mutants with R1-R4 cores were eliminated after 24 h from the C3H/HeN mice, but remained in significant numbers in the kidneys of C3H/HeJ mice. Even the Re mutant of Salmonella minnesota persisted in low numbers in C3H/HeJ mice. The relative bacterial recovery from either mouse strain was related to the overall virulence of the infecting bacterial strain, but the difference between C3H/HeJ and C3H/HeN mice was associated with responsiveness to parts of lipopolysaccharide common to the bacterial strains tested.

Non-antibiotic prevention of urinary tract infection

The identification of several glycoconjugates as receptors for attaching bacteria has resulted in optimism regarding the use of receptor analogues in preventing infection. The structure of receptor-active oligosaccharides and the patient groups which might benefit from such treatment are most thoroughly understood for urinary tract infections. Prevention of adhesion and delay or decrease of infection was achieved using oligosaccharides from the globoseries of glycolipids containing Gal alpha 1----4Gal. This minimal receptor structure as a free saccharide was, however, not sufficient. It was the intact P, P1 and pk determinants which showed optimal activity in vitro. In addition, protection against experimental UTI results from previous exposure to whole bacteria or isolated antigens. The mechanism(s) of protection and their relevance in clinical UTI remain to be defined.

Adherence of cervical, vaginal and distal urethral normal microbial flora to human uroepithelial cells and the inhibition of adherence of gram-negative uropathogens by competitive exclusion

The adherence of the normal flora to human uroepithelial cells was examined using scanning and transmission electron microscopy and an in vitro adhesion assay. The normal flora were isolated from human cervical, vaginal and distal urethral surfaces. Human uroepithelial cells were obtained from healthy females (controls) and from female patients with recurrent urinary tract infection. The results indicate that: 1) there was no significant difference between the mean adherence of the normal flora to the uroepithelial cells from controls or patients, but there were quantitative differences between different bacterial species of the normal flora attaching to uroepithelial cells; 2) bacterial species isolated from the distal urethral and vaginal surfaces attached in larger numbers to uroepithelial cells from controls than from patients at day 10 of the menstrual cycle (peak value of adherence); 3) the adherence patterns of the cervical and vaginal microbial flora were bicyclic and appeared to be related to the human menstrual cycle; 4) complete or partial inhibition of adherence of several Gram-negative uropathogens was achieved by preincubating the uroepithelial cells with several bacterial species of the normal flora. Results from this study suggest that the normal flora of the urinary tract may play an important protective role against attachment of uropathogens to the surfaces of uroepithelial cells, and that the blocking capacity of these organisms may vary over the menstrual cycle.

Genetic factors in host resistance to urinary tract infection

In patients with recurrent pyelonephritis, the pathogenetic events proceed through intestinal colonization, spread to the urinary tract and persistence, seemingly uninterrupted by host defense mechanisms. The factors responsible for the deficient bacterial clearence from the kidneys of these patients, and the genetic control, have not been identified. The susceptibility to colonization has been linked to an increased receptivity for attaching bacteria of the uroepithelia, and to an overrepresentation of the P1 blood group phenotype. To evaluate the role of defects in host defense for the susceptibility to pyelonephritis, experimental UTI in mouse strains with known deficiencies was used. A highly significant increase in susceptibility was noted for C3H/HeJ compared to C3H/HeN mice. The bacterial recovery was inversely correlated to the mitogenic response to LPS. Back-cross analysis revealed a linkage of susceptibility to the Lpsd/Lpsd genotype. In contrast, T and B lymphocyte and complement (C5) defects had little effect on the clearance of Escherichia coli from the kidneys. It is concluded that the inflammatory mechanisms induced by LPS are essential for resistance to experimental pyelonephritis.

Mannose-sensitive and Gal-Gal binding Escherichia coli pili from recombinant strains. Chemical, functional, and serological properties

Chromosomal genes encoding the MS and Gal-Gal binding properties have been cloned into separate recombinants and their respective pili characterized. Hapten inhibition of hemagglutination with synthetic carbohydrate receptor analogues and carbohydrate-adsorbed latex agglutination studies indicate that Gal-Gal and MS pili collectively exhibit the binding properties of the parent strain. MS pili migrated in SDS-PAGE with an Mr of 19 kdaltons and 17 kdaltons; the Mr of Gal-Gal pili was 17.5 kdaltons. The pili are chemically similar by amino acid composition and when the N-terminal cysteines are aligned, 8 of the 13 residues between positions 9 and 22 are homologous. Further, carboxy-terminal sequence homology was inferred from the carboxypeptidase digestion of a MS pili and the sequence of a carboxy-terminal tryptic peptide from Gal-Gal pili.

Contribution of adhesion to bacterial persistence in the mouse urinary tract

The affinity of uropathogenic Escherichia coli to kidneys and bladders of experimentally infected mice was shown to be determined in part by the adhesive properties of the infecting bacteria. Mice were infected with various pairwise combinations of two homogeneic sets of bacteria: (i) mutants derived from a human pyelonephritis E. coli isolate which were selected to express either or both adhesins specific for globoseries glycolipid receptors or for "mannosides"; and (ii) transformants of a normal fecal isolate which harbored recombinant plasmids encoding the genes for one or the other adhesin or which harbored only the vector plasmid. The relative efficiency of survival of the strains to be compared was evaluated in each animal by plating on selective media of samples of homogenized kidneys and bladders taken 24 h after intravesical inoculation. The presence of adhesins specific for globoseries glycolipid receptors, which mediate the in vitro mannose-resistant attachment to human and mouse uroepithelial cells, enhanced bacterial recovery from both kidneys and bladders of infected animals. The addition to the infecting strain of adhesins binding mannoside residues further improved bacterial recovery from the bladder, but not from the kidney. The mutants and transformants with adhesins binding only mannosides were recovered in higher numbers from the bladder than those expressing adhesins specific for the globoseries glycolipids only. There was apparent selection in vivo decreasing expression of mannoside binding adhesins in the kidneys, but not in the bladders, of animals infected with the mutant expressing both types of adhesins. Regardless of adhesive properties, the mutants of the pyelonephritis isolate were recovered in significantly higher numbers than the fecal isolate with adhesins encoded on recombinant plasmids. We conclude that the adhesive properties in part determine the localization and retention of bacteria in the mouse urinary tract. However, the addition of adhesins to a commensal E. coli strain was not sufficient to confer colonization capacity comparable to that of a pyelonephritis strain.