Pyelonephritis In Mice Research Articles

Kidney medullary sodium chloride concentrations induce neutrophil and monocyte extracellular DNA traps that defend against pyelonephritis in vivo

Urinary tract infections are common. Here, we delineate a role of extracellular DNA trap (ET) formation in kidney antibacterial defense and determine mechanisms of their formation in the hyperosmotic environment of the kidney medulla. ET of granulocytic and monocytic origin were present in the kidneys of patients with pyelonephritis along with systemically elevated citrullinated histone levels. Inhibition of the transcription coregulatory, peptidylarginine deaminase 4 (PAD4), required for ET formation, prevented kidney ET formation and promoted pyelonephritis in mice. ETs predominantly accumulated in the kidney medulla. The role of medullary sodium chloride and urea concentrations in ET formation was then investigated. Medullary-range sodium chloride, but not urea, dose-, time- and PAD4-dependently induced ET formation even in the absence of other stimuli. Moderately elevated sodium chloride promoted myeloid cell apoptosis. Sodium gluconate also promoted cell death, proposing a role for sodium ions in this process. Sodium chloride induced myeloid cell calcium influx. Calcium ion-free media or -chelation reduced sodium chloride-induced apoptosis and ET formation while bacterial lipopolysaccharide amplified it. Autologous serum improved bacterial killing in the presence of sodium chloride-induced ET. Depletion of the kidney sodium chloride gradient by loop diuretic therapy diminished kidney medullary ET formation and increased pyelonephritis severity. Thus, our data demonstrate that ETs may protect the kidney against ascending uropathogenic E.coli and delineate kidney medullary range sodium chloride concentrations as novel inducers of programmed myeloid cell death.

Renal Denervation Exacerbates LPS- and Antibody-induced Acute Kidney Injury, but Protects from Pyelonephritis in Mice.

Renal denervation (RDN) is an invasive intervention to treat drug-resistant arterial hypertension. Its therapeutic value is contentious. Here we examined the effects of RDN on inflammatory and infectious kidney disease models in mice. Mice were unilaterally or bilaterally denervated, or sham operated, then three disease models were induced: nephrotoxic nephritis (NTN, a model for crescentic GN), pyelonephritis, and acute endotoxemic kidney injury (as a model for septic kidney injury). Analytical methods included measurement of renal glomerular filtration, proteinuria, flow cytometry of renal immune cells, immunofluorescence microscopy, and three-dimensional imaging of optically cleared kidney tissue by light-sheet fluorescence microscopy followed by algorithmic analysis. Unilateral RDN increased glomerular filtration in denervated kidneys, but decreased it in the contralateral kidneys. In the NTN model, more nephritogenic antibodies were deposited in glomeruli of denervated kidneys, resulting in stronger inflammation and injury in denervated compared with contralateral nondenervated kidneys. Also, intravenously injected LPS increased neutrophil influx and inflammation in the denervated kidneys, both after unilateral and bilateral RDN. When we induced pyelonephritis in bilaterally denervated mice, both kidneys contained less bacteria and neutrophils. In unilaterally denervated mice, pyelonephritis was attenuated and intrarenal neutrophil numbers were lower in the denervated kidneys. The nondenervated contralateral kidneys harbored more bacteria, even compared with sham-operated mice, and showed the strongest influx of neutrophils. Our data suggest that the increased perfusion and filtration in denervated kidneys can profoundly influence concomitant inflammatory diseases. Renal deposition of circulating nephritic material is higher, and hence antibody- and endotoxin-induced kidney injury was aggravated in mice. Pyelonephritis was attenuated in denervated murine kidneys, because the higher glomerular filtration facilitated better flushing of bacteria with the urine, at the expense of contralateral, nondenervated kidneys after unilateral denervation.

Activation of Endogenous Anti-Inflammatory Mediator Cyclic AMP Attenuates Acute Pyelonephritis in Mice Induced by Uropathogenic Escherichia coli

The pathogenesis of pyelonephritis caused by uropathogenic Escherichia coli (UPEC) is not well understood. Here, we show that besides UPEC virulence, the severity of the host innate immune response and invasion of renal epithelial cells are important pathogenic factors. Activation of endogenous anti-inflammatory mediator cAMP significantly attenuated acute pyelonephritis in mice induced by UPEC. Administration of forskolin (a potent elevator of intracellular cAMP) reduced kidney infection (ie, bacterial load, tissue destruction); this was associated with attenuated local inflammation, as evidenced by the reduction of renal production of proinflammatory mediators, renal infiltration of inflammatory cells, and renal myeloperoxidase activity. In primary cell culture systems, forskolin not only down-regulated UPEC-stimulated production of proinflammatory mediators by renal tubular epithelial cells and inflammatory cells (eg, monocyte/macrophages) but also reduced bacterial internalization by renal tubular epithelial cells. Our findings clearly indicate that activation of endogenous anti-inflammatory mediator cAMP is beneficial for controlling UPEC-mediated acute pyelonephritis in mice. The beneficial effect can be explained at least in part by limiting excessive inflammatory responses through acting on both renal tubular epithelial cells and inflammatory cells and by inhibiting bacteria invasion of renal tubular epithelial cells.

Functionally relevant neutrophilia in CD11c diphtheria toxin receptor transgenic mice

Transgenic mice expressing the diphtheria toxin receptor (DTR) in specific cell types are key tools for functional studies in several biological systems. B6.FVB-Tg(Itgax-DTR/EGFP)57Lan/J (CD11c.DTR) and B6.Cg-Tg(Itgax-DTR/OVA/EGFP)1Gjh/Crl (CD11c.DOG) mice express the DTR in CD11c(+) cells, allowing conditional depletion of dendritic cells. We report that dendritic-cell depletion in these models caused polymorphonuclear neutrophil (PMN) release from the bone marrow, which caused chemokine-dependent neutrophilia after 6-24 h and increased bacterial clearance in a mouse pyelonephritis model. We present a transgenic mouse line, B6.Cg-Tg(Itgax-EGFP-CRE-DTR-LUC)2Gjh/Crl (CD11c.LuciDTR), which is unaffected by early neutrophilia. However, CD11c.LuciDTR and CD11c.DTR mice showed late neutrophilia 72 h after dendritic cell depletion, which was independent of PMN release and possibly resulted from increased granulopoiesis. Thus, the time point of dendritic cell depletion and the choice of DTR transgenic mouse line must be considered in experimental settings where neutrophils may be involved.

The impact of serine/threonine phosphorylation in Staphylococcus aureus

In prokaryotes and eukaryotes, phosphotransfer represents a common mechanism to regulate cellular functions. Recent work revealed that modulation of cellular processes by eukaryote-like serine/threonine kinases (STKs) and phosphatases (STPs) are widespread in bacteria. During the last two years, first evidence on the role of Ser/Thr phosphorylation/dephosphorylation in Staphylococcus aureus has emerged leading to the identification of a functional STK and corresponding STP. Due to homology to known STKs/STPs in other bacterial species the kinase was designated PknB or alternatively Stk/Stk1, and the phosphatase Stp. The role of these enzymes in S. aureus has been examined by use of knock-out mutants and a kinase-overexpressing strain. These studies uncovered PknB/Stk and Stp as modulators of cell wall structure and susceptibility to cell wall-acting antibiotics such as certain β-lactams and tunicamycin. By utilizing transcriptional profile analysis a strong regulatory impact of PknB/Stk on the expression of genes encoding proteins which are involved in purine and pyrimidine biosynthesis, cell wall metabolism, autolysis, and glutamine synthesis could be identified. Moreover, PknB/Stk is able to phosphorylate MgrA, thereby regulating activity of the efflux pump NorA. In a mouse pyelonephritis model PknB/Stk has been shown to play a role in virulence. Overall, Ser/Thr phosphorylation/dephosphorylation is a common theme in regulation of cellular functions determining metabolic activity and virulence also in the major human pathogen S. aureus.

Characterization of a Serine/Threonine Kinase Involved in Virulence of Staphylococcus aureus

Staphylococcus aureus is a common human cutaneous and nasal commensal and a major life-threatening pathogen. Adaptation to the different environments encountered inside and outside the host is a crucial requirement for survival and colonization. We identified and characterized a eukaryotic-like serine/threonine kinase with three predicted extracellular PASTA domains (SA1063, or Stk1) and its associated phosphatase (SA1062, or Stp1) in S. aureus. Biochemical analyses revealed that Stk1 displays autokinase activity on threonine and serine residues and is localized to the membrane. Stp1 is a cytoplasmic protein with manganese-dependent phosphatase activity toward phosphorylated Stk1. In-frame deletions of the stk1 and stp1 genes were constructed in S. aureus strain 8325-4. Phenotypic analyses of the mutants revealed reduced growth of the stk1 mutant in RPMI 1640 defined medium that was restored when adenine was added to the medium. Furthermore, the stk1 mutant displayed increased resistance to Triton X-100 and to fosfomycin, suggesting modifications in cell wall metabolism. The stk1 mutant was tested for virulence in a mouse pyelonephritis model and found to be strongly reduced for survival in the kidneys (approximately 2-log-unit decrease) compared to the parental strain. Renal histopathological analyses showed severe inflammatory lesions in mice infected with the parental S. aureus SH1000 strain, whereas the Deltastk1 mutant led to only minimal renal lesions. These results confirm the important role of Stk1 for full expression of S. aureus pathogenesis and suggest that phosphorylation levels controlled by stk1 are essential in controlling bacterial survival within the host.

TUMOR NECROSIS FACTOR-α GENE POLYMORPHISM IN REFLUX NEPHROPATHY

Interstitial scarring contributes to the progression of renal failure in reflux nephropathy. The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) has been implicated in the disease susceptibility and pathogenesis of several inflammatory diseases promoting interstitial infiltration of inflammatory cells. We evaluate the frequency of TNF-alpha gene polymorphism in patients with reflux nephropathy. Renal scarring was evaluated with technetium dimercapto-succinic acid renal scan. Genotyping was performed on 104 patients with reflux nephropathy and 30 controls for the TNF-alpha gene polymorphisms using polymerase chain reaction and restriction digest. This polymorphism involved a guanidine to adenosine transition at position -308 and was designated as TNF1 (-308G) and TNF2 (-308A). The allele frequencies of TNF1 and TNF2 were 18.8% and 81.2% in patients with reflux nephropathy and 76.7% and 23.3% in controls, respectively. The genotype distribution of TNF-alpha-AA was significantly higher (66.4% vs 10%, p <0.05), while the TNF-alpha-GG was lower (13.4% vs 60%, p <0.05) in patients with reflux nephropathy compared to controls. This study demonstrates for the first time the association of the cytokine TNF-alpha gene polymorphism in patients with reflux nephropathy. Our data suggest that patients with vesicoureteral reflux and TNF-alpha AA genotype may have increased susceptibility to reflux nephropathy.

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

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. 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. 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. 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.

CYTOKINE GENE EXPRESSION DURING EXPERIMENTAL ESCHERICHIA COLI PYELONEPHRITIS IN MICE

We studied nine inflammatory and immunoregulatory cytokines in acute pyelonephritis and urethral obstruction in mice to better understand the processes underlying kidney inflammation and scarring. Experimental acute pyelonephritis was established in Bki NMRI outbred mice by bladder inoculation of Escherichia coli, followed by 6 h urethral obstruction. The numbers of cytokine mRNA expressing cells for interleukin-1 (IL-1), IL-4, IL-6, IL-10, IL-12, tumor necrosis factor alpha (TNF-alpha), TNF-beta, transforming growth factor beta (TGF-beta) and interferon gamma (IFN-gamma) were determined in the kidneys and spleens from the infected, non-infected but obstructed and untouched mice using in situ hybridization with radio-labelled oligonucleotide probes at 12 h, 48 h and 6 d after release of the urethral obstruction. Kidney cell expression of IL-1, IL-6 and TNF-alpha mRNA was observed already at 12 h and persisted on day 6 in the infected animals. A significant proinflammatory cytokine response occurred also in the non-infected obstructed animals, albeit later and at lower levels. A marked increase of IL-4, IL-10, TGF-beta and IFN-gamma mRNA producing cells was also found in the kidneys of these two groups again with higher levels in the infected animals. Very high numbers of splenocytes expressing mRNA for IL-1 were observed especially in the infected animals. A high proportion of splenocytes further expressed mRNA for IL-6, TNF-alpha, IL-4, IL-10, IFN-gamma and TGF-beta, again with highest numbers in the infected group of animals. The present study extends previous knowledge about the local and systemic cytokine expression profiles during acute pyelonephritis and after urethral obstruction. Of particular interest was the marked kidney cell expression of mRNA for TGF-beta, presumed to be important both for obstructive and post-infectious renal scarring.

Urethral obstruction of 6 hours or less causes bacteriuria, bacteremia, and pyelonephritis in mice challenged with "nonuropathogenic" Escherichia coli.

Urethral obstruction may be caused by prostatic hypertrophy, urethral stricture, or encrustation of a urethral-catheter lumen. Bacteriuria often complicates these obstructions. The sequelae include fever, acute pyelonephritis, chronic renal inflammation, and death. We hypothesized that even brief obstruction of the urinary tract containing a nonvirulent bacterium would result in these complications. Mice challenged transurethrally with Escherichia coli FN414, which is rapidly eliminated from normal mice without causing bacteriuria, bacteremia, or renal pathology, were subjected to reversible urethral obstruction by coating the urethral meatus with collodion for 1, 3, or 6 h. The majority of mice obstructed for 1 h demonstrated parenchymal renal inflammation 48 h later. At the end of 3 h of obstruction, 9 of 10 mice were bacteremic; some bacteremias were present at 48 h after removal of the obstruction. At that time, more severe renal inflammation was seen in these mice. As little as 6 h of obstruction resulted not only in the acute changes described above but also in chronic renal inflammation and fibrosis in the majority of animals sacrificed 3 and 6 weeks later. Additional studies demonstrated that urethral obstruction enhanced the uropathogenicity of another nonpathogenic E. coli strain (K-12 strain HB101) and caused more severe renal lesions in mice challenged with E. coli CFT073, isolated from a patient with symptoms of pyelonephritis. These findings demonstrate that brief urethral obstruction may (i) induce organisms which are cleared rapidly from the normal urinary tract to cause bacteriuria, bacteremia, and pyelonephritis and (ii) intensify the renal lesions caused by a uropathogen.

Alpha-hemolysin contributes to the pathogenicity of piliated digalactoside-binding Escherichia coli in the kidney: efficacy of an alpha-hemolysin vaccine in preventing renal injury in the BALB/c mouse model of pyelonephritis.

Digalactoside-binding (Gal-Gal) pili and alpha-hemolysin of Escherichia coli have been implicated as important virulence determinants in the pathogenesis of human ascending, nonobstructive pyelonephritis. The pathogenic significance of these determinants was evaluated in vitro and in the BALB/c mouse pyelonephritis model by employing wild-type, avirulent laboratory, and genetically defined cosmids, transformants, and recombinant strains. In vitro data suggest that the cytolytic activity of hemolysin is significantly (P less than 0.05) enhanced among digalactoside-binding strains which agglutinate erythrocytes. The basis of increased hemolysis is related presumably to more efficient delivery of the toxin to target lipid substrate in the host plasma membrane. Intravesicular administration of bacteria that express both digalactoside binding and hemolysin generally resulted in greater mortality and renal parenchymal injury in mice than strains that expressed none or only one of these determinants. Analyses convincingly demonstrate that digalactoside-binding pili are correlated with upper urinary tract colonization and that hemolysin is correlated with septicemia and renal parenchymal damage. These determinants collectively constitute the minimal virulence factors to produce disease in this model. Their efficacy as vaccines for the prevention of pyelonephritis was also assessed. A purified Gal-Gal pilus vaccine prevented (P less than 0.05) subsequent colonization by a challenge wild-type strain that exhibited homologous pili. The hemolysin vaccine did not abrogate subsequent bacterial renal colonization on challenge, but it did protect (P less than 0.05) mice which survived challenge from subsequent renal injury compared with those in the saline control group. The combination of these determinants was also protective. The combination of Gal-Gal pili and hemolysin in a vaccine preparation represents a potentially worthwhile strategy for human immunoprophylaxis against pyelonephritis by interdicting several steps in the pathogenesis of a bacterial mucosal infection.

Electron microscopic study of acuteretrograde pyelonephritis in mice

A strain of Escherichia coli 06:H-, which was isolated from a patient with acutepyelonephritis, was used to produce ascending pyelonephritis in mice. The histologic features at the early stage of acute pyelonephritis and the pathways of bacterial invasion and distribution in the infected kidneys were studied by using transmission electron microscope. The histologic changes were characterized by degeneration and destruction of renal pelvic and tubular epithelial cells, and a massive infiltration of polymorphonuclear leukocytes. Bacteria invaded the pelvic surface and spread over the renal medulla and cortex by contiguity twelve hours after infection. It was also shown that bacteria ascended the tubules, multiplied in the tubular lamina, destroyed the tubular epithelial cells, and spread over the renal cortex by twelve hours. In addition, bacteria and leukocytes phagocytizing bacteria were present in the capillaries in the renal interstitium twelve hours after infection.

Comparative antibacterial activities of temafloxacin hydrochloride (A-62254) and two reference fluoroquinolones

The in vitro and in vivo properties of a new 1-difluorophenyl-6-fluoroquinolone, temafloxacin hydrochloride (A-62254), were compared with those of difloxacin and ciprofloxacin. Temafloxacin hydrochloride was as active as ciprofloxacin and difloxacin against staphylococci and as active as ciprofloxacin and 2 twofold dilutions more active than difloxacin against streptococci. Against gram-negative enteric bacteria and Pseudomonas aeruginosa, temafloxacin hydrochloride was 2 twofold dilutions more active than difloxacin but 2 to 4 twofold dilutions less active than ciprofloxacin. The MICs of temafloxacin hydrochloride and difloxacin were increased by 2 to 5 twofold dilutions in urine at pH 6.5 compared with 4 to 5 twofold-dilution increases in the MICs of ciprofloxacin. The MICs of temafloxacin hydrochloride, difloxacin, and ciprofloxacin were increased by 1 to 3 twofold dilutions in serum. The MICs of temafloxacin hydrochloride, difloxacin, and ciprofloxacin were the same or within 1 to 2 twofold dilutions at pHs 6.5, 7.2, and 8.0. When administered orally in mouse protection tests, temafloxacin hydrochloride was as active as difloxacin and 5 to 10 times more active than ciprofloxacin against infections with Staphylococcus aureus and streptococci. Against infections with gram-negative enteric bacteria and P. aeruginosa, temafloxacin hydrochloride was as active as difloxacin and ciprofloxacin. Temafloxacin hydrochloride was three times less active than difloxacin but was five times more active than ciprofloxacin against infections with Salmonella typhimurium. Temafloxacin hydrochloride was as active as difloxacin and ciprofloxacin against P. aeruginosa and Proteus mirabilis pyelonephritis in mice. The peak serum concentration and serum half-life of temafloxacin hydrochloride in mice were approximately one-half and one-sixth, respectively, that of difloxacin after oral administration. The peak serum concentration of temafloxacin hydrochloride in mice after oral administration was six times higher than that of ciprofloxacin, and the serum half-life was equal to that of ciprofloxacin.

The frequency of in-vitro resistance development to fluoroquinolones and the use of a murine pyelonephritis model to demonstrate selection of resistance in vivo

The frequency of development of resistance to the fluoroquinolones in vitro was generally low with Escherichia coli (in the order of 10(-7) to less than 10(-9) and high with Pseudomonas aeruginosa (in the order of 10(-5) to 10(-7)). Susceptibility to the fluoroquinolones also decreased after serial transfer in increasing concentrations of the drug. Although the MICs for the resistant E. coli variants were higher than that of the parent organism, they were still susceptible to achievable serum concentrations of all the quinolones except nalidixic acid. On the other hand some of the P. aeruginosa variants selected for resistance were resistant to achievable serum concentrations of all the quinolones. When E. coli pyelonephritis in mice was treated with the fluoroquinolones, difloxacin, A-56620, and ciprofloxacin were more effective than norfloxacin and nalidixic acid in lowering viable bacterial counts in the kidneys. The susceptibility of E. coli isolated from kidneys of mice treated with the quinolones was the same as that of the parent strain. When P. aeruginosa pyelonephritis in mice was treated with the fluoroquinolones an initial reduction in the cell count was seen, followed by an increase in the number of resistant variants. The resistant variants differed in their colony morphology and cell envelope proteins. The levels of resistance for the P. aeruginosa variants ranged from a two- to a 64-fold increase in the MIC.

Experimental haematogenous pyelonephritis in mice with uropathogenic, enteropathogenic and enterotoxigenic

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.

The virulence of glucose non-fermentative organisms in experimental pyelonephritis in mice.

The virulence of clinical isolates of Acinetobacter calcoaceticus, Pseudomonas cepacia, and Pseudomonas maltophilia in urinary tract in mice was studied.In general, the virulence of these organisms in urinary tract of normal mice was relatively mild.The effect of anti-inflammatory and immunosuppressive drugs on pathogenicity of these organisms was studied in mice.The mice previously treated with betamethasone or prednisolone as anti-inflammatory drug, and with cyclophosphamide or azathiopurine as immunosuppressive drug, were more susceptible to these bacterial infections than were the non-treated ones.As for the capacity of bacterial attachment to the epithelial cells of the bladder, these organisms were generally shown to have low adhesion.Furthermore, the hemagglutination patterns were mannose-sensitive in human and guinea pig erythrocytes.

Ascending pyelonephritis with Pseudomonas aeruginosa in mice.

Elastase- and protease- producing strain of Pseudomonas aeruginosa induced ascending pyelonephritis in mice by intracystic challenge. The pelvis was the site of primary foci development and necrotic, purulent lesions spread from the pelvis to the perihilar area and to the cortex. Severe necrosis was a characteristic of the present infection and caused systemic infection and host death without the development of chronic lesions. In animals challenged with inocula great enough to destroy the cystic mucosa, immediate hematogenous systemic infection without cellular responses led to host death.

EXPERIMENTAL PYELONEPHRITIS IN MICE FOLLOWING ASCENDING INFECTION WITH E. COLI

Adhesive and invasive strains of Escherichia coli induced chronic pyelonephritis in mice following the acute phase. The pathological features of the induced chronic pyelonephritis were different between the groups of mice infected with these strains. In piliated adhesive strain (E77156)‐infection, the kidneys with viable bacilli showed pyonephrosis with incomplete obstruction or atrophy with coarse scar. Mice with these renal lesions showed high serum antibody levels, but histologically recurrent infection was frequent. On the other hand, in non‐piliated invasive strain (633–65)‐infection, sterile pyelonephritis developed. This chronic lesion was characterized by the migration of antigen‐bearing macrophages and lymphocytes and by a negative serum antibody response. In infections with either strain the predominant lymphocytes in the renal lesions were smooth‐surfaced T‐lymphocytes.

EXPERIMENTAL PYELONEPHRITIS IN MICE FOLLOWING ASCENDING INFECTION WITH E. COLI

The initial interaction between uroepithelial cells and Escherichia coli which has adhesive or invasive activity for cultured cells was studied ultrastructurally at the in situ site of infection in the model of ascending pyelonephritis in mice. The densely piliated adhesive strain E77156 isolated from the urine of a patient with urinary tract infection adhered to the pelvic and renal tubular epithelial cells and colonized on their cell surfaces and thereafter in the cytoplasm. The non‐piliated invasive strain 633–65 isolated from a patient with dysentery‐like syndrome did not colonize on the uroepithelial cell surfaces but easily penetrated into the cytoplasm of these cells. Thereafter multiplication was observed in their cytoplasm. Neither strain scarcely penetrated into the interstitium via the basement membrane of the renal tubules.

Effect of active and passive immunization on the development of experimental Pseudomonas aeruginosa pyelonephritis in mice

Experimental pyelonephritis was produced in mice by the intravenous injection of Pseudomonas aeruginosa. Immune response to infection was studied by passive hemagglutination antibody titers. Vaccination of mice with live P. aeruginosa or culture filtrates (Pseudomonas antigen) induced antibodies and resulted in a high degree of protection against death and pyelonephritis following subsequent hematogenous challenge with the homologous strain. Transfer of immune serum protected mice against death following infection with the homologous strain and with a heterologous strain. However, immune serum failed to protect mice from kidney infection by the heterologous strain. These data indicate that immune serum seemed to protect against early, overwhelming bacteremia but did not prevent a chronic course of kidney infection by a heterologous strain.