Enterococcus faecalis aggravates pyelonephritis caused by Pseudomonas aeruginosa in experimental ascending mixed urinary tract infection in mice.

Mixed urinary tract infection was caused by simultaneous inoculation of 10(4) CFU each of Enterococcus faecalis TN2005 and Pseudomonas aeruginosa P9 into the bladders of CBA/J mice. Both organisms proliferated in the kidneys, and viable cell counts of E. faecalis TN2005 reached a peak level of 4.1 x 10(5) CFU per pair of kidneys within the first 24 h, while P. aeruginosa P9 counts increased more slowly. The number of P. aeruginosa P9 cells peaked at 8.3 x 10(6) CFU per pair of kidneys 5 days after infection. Five days after mixed infection, infiltration of neutrophils into the renal pelvis and renal medulla was observed. Immunohistochemical staining revealed the presence of E. faecalis antigen in the renal medulla. P. aeruginosa antigen was detected mainly in the renal pelvis 5 days after infection and in the renal medulla as well as the renal pelvis 14 days after infection. Mixed infection induced pyelonephritis within 5 days after mixed infection, while it was not observed until 14 days after infection with P. aeruginosa P9 alone. P. aeruginosa P9 inoculated together with E. faecalis TN2005 was more resistant to eradication from the kidneys by beta-lactam antibiotics than P. aeruginosa P9 inoculated alone. These results suggest that E. faecalis TN2005 invades the renal medulla first in mixed urinary tract infection and induces histological changes which lead to aggravation of the pyelonephritis caused by P. aeruginosa P9.     

Increased severity of urinary tract infection and bacteremia in mice with urinary bladder injury induced by cyclophosphamide.

The effect of cyclophosphamide on urinary tract infection was studied, using Pseudomonas aeruginosa in a murine model. Urinary tract infections were produced by injecting P. aeruginosa through a urethral catheter into the bladders of mice. The number of P. aeruginosa organisms in the bladder tissue and kidneys, histopathology, peripheral leukocyte count, and antibody response to P. aeruginosa was measured. The local effect of cyclophosphamide on the bladder was determined by measuring the bladder tissue water and examining the histopathology. Cyclophosphamide increased the susceptibility of mice to P. aeruginosa urinary tract infection, resulting in marked cystitis and an increase in renal infection, bacteremia, and mortality. These changes correlated with the toxic effect of cyclophosphamide on the wall of the bladder rather than with peripheral leukopenia or failure of antibody response.     

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.     

Murine gastrointestinal tract as a portal of entry in experimental Pseudomonas aeruginosa infections.

Peroral administration of viable Pseudomonas aeruginosa into the stomach of mice resulted in an acute systemic infection, with death occurring within 72 h. One strain, ATCC 19660, a non-encapsulated form of P. aeruginosa, had a median lethal dose of 5.3 X 10(6) colony-forming units, whereas two encapsulated strains, ATCC 17933 and 17934, had median lethal dose values of 5.0 x 10(7) and 5.6 x 10(7) colony-forming units, respectively. Each strain required fewer organisms to establish a lethal infection via the stomach than by intravenous or intraperitoneal routes. The non-encapsulated strain, ATCC 19660, did not cause any diarrhea in the infected animals, whereas the two encapsulated strains, although less virulent, caused diarrhea when administered perorally. No signs of necrosis were noted within the gastrointestinal tract; however, hematogenous spread of the organism resulted in a vasculitis associated with the pulmonary vessels and bacterial invasion of the renal tissues. Treatment of animals with antineoplastic drugs 24 h before or simultaneously with peroral challenge resulted in an increased susceptibility to infection.     

Systemic and gastrointestinal candidiasis of infant mice after intragastric challenge.

Systemic and gastrointestinal infection can be established in infant mice after intragastric challenge with Candida albicans. Differences in virulence of the six strains tested were noted. As early as 3 h after infection, some but not all livers, spleens, and kidneys contained C. albicans, but the peak number of colony-forming units in these organs was seen at 6 h. The early colonization of the organs could not be attributed to aspiration of the inoculum since about 90% of lungs and livers tested yielded no colony-forming units at 10 to 15 min postinfection. In animals with systemic infections, lungs, livers, kidneys, and spleens showed similar numbers of colony-forming units within the organs during the first 6 h postinfection- and then the number declined progressively up to 72 h. The gastrointestinal tract was colonized throughout a 20-day period of study. Counts made at intervals beyond day 1 yielded between 10(5) and 10(6) colony-forming units in the stomach, ileum, and cecum. Preparatory techniques for scanning electron microscopy preserved the yeast, intestinal mucus layer, and epithelial surface and made it possible to visualize the association between the pathogen and host tissues within the digestive tract.     

Visualization of Proteus mirabilis morphotypes in the urinary tract: the elongated swarmer cell is rarely observed in ascending urinary tract infection

Proteus mirabilis, a common cause of nosocomial and catheter-associated urinary tract infection, colonizes the bladder and ascends the ureters to the proximal tubules of the kidneys, leading to the development of acute pyelonephritis. P. mirabilis is capable of swarming, a form of multicellular behavior in which bacteria differentiate from the short rod typical of members of the family Enterobacteriaceae, termed the swimmer cell, into hyperflagellated elongated bacteria capable of rapid and coordinated population migration across surfaces, called the swarmer cell. There has been considerable debate as to which morphotype predominates during urinary tract infection. P. mirabilis(pBAC001), which expresses green fluorescent protein in both swimming and swarming morphotypes, was constructed to quantify the prevalence of each morphotype in ascending urinary tract infection. Transurethral inoculation of P. mirabilis(pBAC001) resulted in ascending urinary tract infection and kidney pathology in mice examined at both 2 and 4 days postinoculation. Using confocal microscopy, we were able to investigate the morphotypes of the bacteria in the urinary tract. Of 5,087 bacteria measured in bladders, ureters, and kidneys, only 7 (0.14%) were identified as swarmers. MR/P fimbria expression, which correlates with the swimmer phenotype, is prevalent on bacteria in the ureters and bladder. We conclude that, by far, the predominant morphotype present in the urinary tract during ascending infection is the short rod-the swimmer cell.     

Human lactoferrin and peptides derived from a surface-exposed helical region reduce experimental Escherichia coli urinary tract infection in mice

Lactoferrin (LF) is a multifunctional immunoregulatory protein that has been associated with host defense at mucosal surfaces through its antibacterial properties. The antibacterial and anti-inflammatory properties of LF were further explored with an animal model of experimental urinary tract infection. Bovine LF (bLF), human LF (hLF), and synthetic peptide sequences based on the antibacterial region of hLF (amino acid residues 16 to 40 [HLD1] and 18 to 40 [HLD2]) were given orally to female mice 30 min after the instillation of 10(8) Escherichia coli bacteria into the urinary bladder. The control groups received phosphate-buffered saline or water. C3H/Tif mice were treated with hLF or bLF, and C3H/HeN mice were treated with bLF only. The numbers of bacteria in the kidneys and bladder of C3H/Tif and C3H/HeN mice were significantly reduced 24 h later by the LF treatments compared to the findings for the control group. The hLF-treated group showed the strongest reduction compared with the vehicle-treated-group (P values were 0.009 and 0.0001 for the kidneys and bladder, respectively). The urinary leukocyte response was diminished in the hLF-treated group. The hLF treatment also significantly reduced the urinary interleukin-6 (IL-6) levels at 2 h and the systemic IL-6 levels at 24 h after infection (P values were 0.04 and < 0.002, respectively). In the bLF-treated animals, no such strong anti-inflammatory effects were obtained. In another series of experiments, C3H/Tif mice perorally treated with HLD1 or HLD2 also showed reduced numbers of bacteria in the kidneys compared with the vehicle-treated mice, although the results were significantly different only for HLD2 (P < 0.01). Analysis of urine from hLF-fed C3H/Tif mice showed that hLF was excreted into the urinary tract at 2 h after feeding. Testing of the in vitro bactericidal activity of LF (1 mg/ml) or the peptides (0.1 mg/ml) in mouse urine against the E. coli bacteria revealed moderate killing only by HLD2. In conclusion, these results demonstrate for the first time that oral administration of hLF or peptides thereof is effective in reducing infection and inflammation at a remote site, the urinary tract, possibly through transfer of hLF or its peptides to the site of infection via renal secretion. The antibacterial mechanism is suggested to involve bactericidal capacities of LF, fragments thereof, or its peptides.     

A three-year study of nosocomial infections associated with Pseudomonas aeruginosa.

During a 3-year study period in a university teaching hospital, 417 nosocomial infections associated with Pseudomonas aeruginosa were documented in 321 patients. The overall rate of P. aeruginosa nosocomial infection was 5.3 cases per 1,000 patients. Residence on the surgery or medicine service, advanced patient age, and exposure to the burn, surgery, or medicine intensive care units correlated with higher rates of infection. The most common sites for P. aeruginosa infection were the lower respiratory tract, urinary tract, blood stream, and surgical wounds. Nosocomial P. aeruginosa lower respiratory tract and blood stream infections were significantly associated with exposure to certain intensive care units, whereas P. aeruginosa urinary tract infections more commonly occurred on the neurology and neurosurgery services. Results of live antigen serotyping showed that serotype 6 was most common, followed by serotypes 1 and 11. Serotype 6 correlated with resistance to carbenicillin, gentamicin, and tobramycin, and serotype 11 correlated with resistance to carbenicillin. Two-thirds of the isolates tested were sensitive to carbenicillin, gentamicin, and tobramycin, but 13.2% were resistant to all three of these drugs. P. aeruginosa isolates resistant to all three drugs were associated with urinary tract infections.     

Role of natural killer cells in resistance to Cryptococcus neoformans infections in mice.

Previous studies have suggested a possible role for natural killer (NK) cells in resistance to some fungal infections, including Cryptococcus neoformans infections. The role of NK cells in early clearance of C neoformans from tissues and in long-term survival was studied in mice following intravenous inoculations of the organism. Mice treated with anti-asialo GM1 antiserum to temporarily reduce NK activity demonstrated an increase in colony-forming units (CFU) of C neoformans in the lung 24 hours after an intravenous inoculation of the organism. CFU in liver, spleen, kidney, and brain were not different in anti-asialo GM1 antiserum-treated versus control mice. An NK-specific reagent, anti-NK 1.1 monoclonal antibody, was used to deplete mice of NK cells in vivo for at least 14 days without affecting other natural defenses. The number of C neoformans retained in the lungs 24 hours after inoculation of the organism was significantly greater in NK cell-depleted mice than in controls, although CFU in other organs were unaffected. Following the intravenous inoculation of C neoformans, the survival of anti-NK 1.1-treated mice was not different from control mice. The effect of NK cell activity on resistance to C neoformans was also determined after an intratracheal inoculation of the organism. Mice pretreated with anti-NK 1.1 demonstrated no increases in CFU in the lungs, spleen, or brain as compared with controls. These data indicate that NK cells can play a role in vivo in early resistance against C neoformans if the organism is delivered via the intravenous route. However, NK cells do not play a role in either determining survival after an intravenous inoculation nor in resistance during an infection acquired via the respiratory tract.     

Inoculation candidiasis in a murine model of severe combined immunodeficiency syndrome.

To further elucidate the importance of T- and B-lymphocyte-mediated responses in host defense against systemic infection with Candida albicans, we studied this infection in a murine model of severe combined immunodeficiency (SCID). The course of inoculation candidiasis in these mice, which lack functional T and B lymphocytes, was compared with that in immunologically normal BALB/c mice. Mice were inoculated intravenously with 10(5) yeast cells. Quantitative cultures of liver, spleen, and kidneys were performed with necropsy specimens obtained 1, 3, 7, 10, 14, and 21 days after this intravenous inoculation. The differences in the time courses of recovery of organisms from liver and spleen specimens were not significantly different in the SCID mice compared with the BALB/c mice. The recovery of C. albicans from the kidneys was significantly lower in the SCID mice, indicating less persistence of the organism in the kidneys of the SCID mice than in those of the BALB/c mice. These data indicate that defense mechanisms other than T- and B-lymphocyte-mediated mechanisms are primarily responsible for host defense against inoculation candidiasis.     

Defined mutants ofProteus mirabilislacking flagella cause ascending urinary tract infection in mice

A clinical isolate ofProteus mirabilis(Pr 990) and an isogenic non-flagellate allelic replacement mutant (Pr M9) were tested for their ability to cause infection in the ascending mouse model of urinary tract infection. Wild-type Pr 990 differentiates into swarmer cells in brain-heart infusion broth. Pr M9 neither has flagella nor does it apparently differentiate into swarmer cells after subculturing. The infectivity of both strains from an initial culture and the sixth subculture was assessed in the ascending urinary tract infection mouse model. Infection was ascertained by determining colony forming units from kidney and bladder homogenates from individual mice 7 days after inoculation. In all cases the non-flagellate mutant Pr M9 was at least as infective as Pr 990. Using bacteria from the first culture, Pr M9 infected 61.5% and Pr 990 infected 45.5% of mice tested. The levels of viable counts were similar between the Pr M9 and the Pr 990 infections. Using bacteria from the sixth subculture, Pr M9 infected 75% and Pr 990 infected 76.5% of mice tested. Again viable counts were similar. Pr 990 increased in infectivity from the first to the sixth subculture, whereas Pr M9 did not, but this may be a reflection of the high initial rate of infectivity with first culture Pr M9. These results suggest that neither flagella nor swarmer cells are required forP. mirabilisinfectivity in ascending urinary tract infections in mice.     

Increased susceptibility to lethal Candida infections in burned mice preinfected with Pseudomonas aeruginosa or pretreated with proteolytic enzymes.

Lethal Candida infections in burn patients are frequently preceded by or occur concomitantly with bacterial infections, which are often due to Pseudomonas aeruginosa. In this study, we developed a burned, mixed-challenge mouse model, which was designed to determine whether and how a recent bacterial infection could influence the development of subsequent candidosis. In this model, burned mice that were preinfected with a sublethal challenge of elastase-producing P. aeruginosa strain WR-5 and then sublethally challenged with Candida albicans exhibited a mortality rate of 60%, while unburned mice challenged in the same way and burned mice that received only one challenge organism exhibited mortality rates of less than 10%. Quantitative microbial counts performed with the kidneys, livers, and eschars of burned mice challenged with both organisms indicated that the deaths were due to Candida infection. Substitution of an elastase-negative P. aeruginosa strain for strain WR-5 in the model resulted in significantly lower mortality rates and lower microbial numbers in the organs. When the Pseudomonas enzyme elastase was substituted for the elastase-positive bacteria in the model, both the mortality rates and the organ counts were comparable to the values found after preinfection with strain WR-5. Another protease, thermolysin, was substituted for the elastase and produced similar mortality results. When the protease inhibitor alpha 2-macroglobulin was given to burned mice infected with the two organisms, it prevented the deaths due to Candida infection. We concluded that this model is one way to study bacterial-fungal infections in burned mice, that recent Pseudomonas infections could predispose burned mice to fatal candidosis, and that the proteolytic activity generated by the bacteria was primarily responsible for the establishment of lethal fungal infections.     

Protective role of intestinal flora against infection with Pseudomonas aeruginosa in mice: influence of antibiotics on colonization resistance.

Swiss white mice were given ampicillin, clindamycin, kanamycin, metronidazole, or streptomycin in drinking water for a period of 3 weeks. One week after the initiation of antibiotic administration, the treated mice and untreated control mice were challenged orally with approximately 10(8) viable, streptomycin-resistant (SR) Pseudomonas aeruginosa isolates. All five of the antibiotics decreased the resistance of the mice to intestinal colonization with SR P. aeruginosa, as reflected by an increased fecal carriage of the organism and an increase in population levels of SR P. aeruginosa in feces as compared with untreated controls. Metronidazole was least effective in this regard. The antibiotics lowered the dose of SR P. aeruginosa that resulted in implantation in 50% of the mice ID50 to various degrees. Administration of streptomycin, the most effective antibiotic, caused a 10,000-fold decrease in ID50 as compared with untreated controls. Oral inoculation of approximately 10(8) organisms of SR P. aeruginosa resulted in translocation of the organism to the mesenteric lymph nodes, spleens, or livers of 13 or 17 streptomycin-treated mice, 1 of 20 clindamycin-treated mice, and 1 of 14 metronidazole-treated mice. Translocation was not observed, however, in ampicillin- or kanamycin-treated animals. Antibiotic activity was detected in the cecal contents of streptomycin-, kanamycin, and clindamycin-treated mice but not in the cecal contents of ampicillin- or metronidazole-treated animals.     

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.     

Synergistic Effect in Viral-Bacterial Infection: Combined Infection of the Murine Respiratory Tract with Sendai Virus and Pasteurella pneumotropica

Synergism was demonstrated between Sendai virus and Pasteurella pneumotropica in the respiratory tract of mice showing no evidence of previous infection with either agent. Mice aerosol challenged with P. pneumotropica invariably eliminated the viable organism from their lungs within 72 h. In contrast, intrapulmonary killing was delayed in animals previously infected with Sendai virus. Maximum synergism was observed when virus infection preceded bacterial challenge by 6 days. At this time, a mortality rate of 37% was observed as compared with 0, 10, 20, and 10%, respectively, in those animals in which the virus infection preceded bacterial challenge by 1, 3, 9, and 12 days. Previous immunization with Sendai virus completely prevented virus infection and thus the synergistic effect. Synergism with endogenous flora was also noted. Six days after virus infection an endogenous Pasteurella sp. began to proliferate in the bronchopulmonary tissues. Up to 10(4) colony-forming units per lung were recovered but no animals died of the endogenous Pasteurella infection.     

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.     

Experimental production of actinomycetoma in BALB/c mice.

Chronic actinomycetoma associated with grain production was induced in BALB/c mice by subcutaneous inoculation of live Nocardia brasiliensis in Freund incomplete adjuvant into the hind footpads. Similar inoculation of N. asteroides and N. caviae resulted in local tumor formation which healed spontaneously after 5 months, the disease disseminating into the peritoneum, where masses or organisms could be detected. Grains were recovered from superficial skin lesions of N. caviae, but not from the N. asteroides-infected mice. Mycetoma lesions, appearing as early as 1 month after inoculation of 1.2 X 10(7) colony-forming units of N. brasiliensis per ml or as late as 3 months with inoculation of 1.0 X 10(5) colony-forming units per ml, became persistent and were readily detectable even 6 months after inoculation. No spontaneous healing occurred, and grains were recovered at different stages of the disease. Saline suspensions of N. brasiliensis also produced typical mycetoma lesions, although the incubation period was ca. 6 months. Adjuvant addition appeared to accelerate the onset of the disease. Experimental production of actinomycetoma in laboratory animals allows the study of many unanswered aspects of the disease and also provides a suitable model for therapeutic trials in the search for new and more effective chemotherapeutic agents.     

Role of type 1 fimbriae in the pathogenesis of ascending urinary tract infection induced by escherichia coli in mice.

Escherichia coli mutants defective in the ability to agglutinate guinea pig erythrocytes (HA-) were isolated from a nalidixic acid-resistant derivative, 31-B, of E. coli TN 675 that produces type 1 fimbriae and induces urinary tract infection in mice fed a 5% glucose solution. All nine HA- mutants were defective not only in their ability to agglutinate Candida albicans cells and erythrocytes from various species, but also in their capacity to adhere to mouse bladder epithelial cells. None of the mutants were agglutinated by anti-type 1 fimbriae antiserum. Although most of the mutants were fimbriated when examined by electron microscopy, their fimbriae differed serologically from type 1 fimbriae. All of the mutants showed 100 to 1,000 times lower bacterial recovery from the bladder walls of mice 3 h after inoculation into the bladder and lacked urinary tract infectivity in mice. These results suggest that all of the HA- mutants are defective in type 1 fimbriae production and that type 1 fimbriae facilitate the development of urinary tract infection in mice, probably by mediating bacterial adherence to the bladder epithelial cells.     

Rapid diagnosis of Pseudomonas aeruginosa urinary tract infections by radioimmunoassay.

A solid-phase radioimmunoassay designed to detect serotype 6 Pseudomonas aeruginosa antigens was evaluated for its ability to rapidly diagnose urinary tract infections. Twelve P. aeruginosa serotypes were easily differentiated in the assay from eight other gram-negative bacterial species. During log-phase growth, the assay detected antigens in culture when approximately 10(6) or more serotype 6 P. aeruginosa organisms were present. Both cell-associated and solubilized antigens were detected. The assay detected antigens in 13 of 17 urine specimens which grew greater than 10(5) P. aeruginosa, 3 of 38 which grew other gram-negative rods, and none of 83 with no growth. Two of the three positive specimens from the other gram-negative rod group probably also contained P. aeruginosa. No preincubation of the urine specimens was required, and results were available within 2.5 h. The assay represents an improvement over other procedures for rapidly diagnosing urinary tract infections in that it allows diagnosis by species and should be adaptable to semiautomation.     

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

A model for ascending unobstructed urinary tract infection was developed in mice to study the pathogenesis of urinary tract infection induced by Escherichia coli associated with urinary tract infection in humans. Specifically, the model was designed to monitor the initial stages of the infectious process, e.g., bacterial adhesion. Mice were selected since the specificity and intensity of bacterial attachment of pyelonephritogenic E. coli strains to human and mouse uroepithelial cells were similar. Female mice were infected by urethral catheterization and installation of bacteria in the urinary bladder. To maximize clearance of unattached bacteria, no obstructive manipulations were performed. After sacrifice, the persistence of bacteria in kidneys and bladder was determined by viable counts on homogenized tissues. The experimental infection was standardized by using one pyelonephritis (HU734) and one normal fecal (414) E. coli isolate. With both strains all of the bladders became infected, but E. coli 414 was eliminated more rapidly than HU734. The percentage of positive kidney cultures increased with the bacterial inoculum concentration and volume. An inoculum of 0.05 ml containing 10(10) bacteria per ml was selected, giving the highest percentage of positive kidney cultures without detectable bacterial spread to the blood stream. The variation in the percentage of positive kidney cultures possibly depended on the degree of vesicoureteric reflux in the individual animals. Both in the kidneys and in the urinary bladders, strain HU734 yielded higher numbers of bacteria at 24 h and persisted longer than did strain 414. Several E. coli pyelonephritis isolates with properties associated with virulence in the human urinary tract consistently were recovered from mouse kidneys and bladders in higher numbers than E. coli strains of human fecal origin lacking those properties. The role of bacterial adhesion per se is the topic of the accompanying paper.