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Acute bacterial meningitis is not an uncommon central nervous system infection. In severe cases, it can be associated with various neurological or systemic complications. However, acute spinal cord dysfunction rarely occurs. We report a case of bacterial meningitis complicated with spinal cord infarction despite adequate treatment with antibiotics and corticosteroid therapy. He had residual paraplegia and was fully dependent in the activity of daily living., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2018. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Extracts from the leaves of Orthosiphon stamineus are used in phytotherapy for treatment of uncomplicated urinary tract infections., Purposes: Evaluation of an aqueous extract against infection with uropathogenic Escherichia coli in vivo; investigation of underlying microbiological mechanisms., Study Design: In vivo studies in mice and in vitro investigations on cytotoxicity, antiadhesive potential, influence on bacterial gene expression and quorum sensing., Methods: Extract OWE was prepared by hot water extraction. For in vivo studies BALB/c mice were used in an UPEC infection model. The effect of OWE on bacterial load in bladder/kidney tissue was monitored in pre- and posttreatment. Cytotoxicity of OWE against different UPEC strains, T24 bladder/A498 kidney cells, gene expression analysis, monitoring of phenotypic motility and quorum sensing was investigated by standard methods of microbiology., Results: OWE was quantified (UHPLC) according to the content of rosmarinic acid, cichoric acid, caffeic acid. Three- and 5-day treatment of animals with OWE (750mg/kg) after transurethral infection with UPEC CFT073 reduced the bacterial load in bladder and kidney, similar to norfloxacin. Four- and 7-day pretreatment of mice prior to the infection with UPEC NU14 reduced bacterial bladder colonization. In vitro investigations indicated that OWE (≤2mg/ml) has no cytotoxic or proliferation-inhibiting activity against different UPEC strains as well as against T24 bladder and A498 kidney cells. OWE exerts a dose dependent antiadhesive activity against UPEC strains NU14 and UTI89. OWE reduced gene expression of fimH, but evoked increase of the expression of motility/fitness gene fliC. Increase of bacterial motility on gene level was confirmed by a changed bacterial phenotype by an increased bacterial motility in soft agar assay. OWE inhibited in a concentration-dependent manner bacterial quorum sensing., Conclusion: OWE is assessed as a strong antiadhesive plant extract for which the traditional use in phytotherapy for UTI might be justified., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Objectives: Traditionally, the urinary tract has been thought to be sterile in the absence of a clinically identifiable infection. However, recent evidence suggests that the urinary tract harbors a variety of bacterial species, known collectively as the urinary microbiome, even when clinical cultures are negative. Whether these bacteria promote urinary health or contribute to urinary tract disease remains unknown. Emerging evidence indicates that a shift in the urinary microbiome may play an important role in urgency urinary incontinence (UUI). The goal of this prospective pilot study was to determine how the urinary microbiome is different between women with and without UUI. We also sought to identify if characteristics of the urinary microbiome are associated with UUI severity., Methods: We collected urine from clinically well-characterized women with UUI (n = 10) and normal bladder function (n = 10) using a transurethral catheter to avoid bacterial contamination from external tissue. To characterize the resident microbial community, we amplified the bacterial 16S rRNA gene by PCR and performed sequencing using Illumina MiSeq. Sequences were processed using the workflow package QIIME. We identified bacteria that had differential relative abundance between UUI and controls using DESeq2 to fit generalized linear models based on the negative binomial distribution. We also identified relationships between the diversity of the urinary microbiome and severity of UUI symptoms with Pearson's correlation coefficient., Results: We successfully extracted and sequenced bacterial DNA from 95% of the urine samples and identified that there is a polymicrobial community in the female bladder in both healthy controls and women with UUI. We found the relative abundance of 14 bacteria significantly differed between control and UUI samples. Furthermore, we established that an increase in UUI symptom severity is associated with a decrease in microbial diversity in women with UUI., Conclusions: Our study provides further characterization of the urinary microbiome in both healthy controls and extensively phenotyped women with UUI. Our results also suggest that the urinary microbiome may play an important role in the pathophysiology of UUI and that the loss of microbial diversity may be associated with clinical severity.

Inhibiting antibodies targeting receptor-binding pockets in proteins is a major focus in the development of vaccines and in antibody-based therapeutic strategies. Here, by using a common mannose-specific fimbrial adhesin of Escherichia coli, FimH, we demonstrate that locking the adhesin in a low-binding conformation induces the production of binding pocket-specific, adhesion-inhibiting antibodies. A di-sulfide bridge was introduced into the conformationally dynamic FimH lectin domain, away from the mannose-binding pocket but rendering it defective with regard to mannose binding. Unlike the native, functionally active lectin domain, the functionally defective domain was potent in inducing inhibitory monoclonal antibodies that blocked FimH-mediated bacterial adhesion to epithelial cells and urinary bladder infection in mice. Inhibition of adhesion involved direct competition between the antibodies and mannose for the binding pocket. Binding pocket-specific inhibitory antibodies also were abundant in polyclonal immune serum raised against the functionally defective lectin domain. The monoclonal antibodies elicited against the binding-defective protein bound to the high-affinity conformation of the adhesin more avidly than to the low-affinity form. However, both soluble mannose and blood plasma more strongly inhibited antibody recognition of the high-affinity FimH conformation than the low-affinity form. We propose that in the functionally active conformation the binding-pocket epitopes are shielded from targeted antibody development by ligand masking and that strong immunogenicity of the binding pocket is unblocked when the adhesive domain is in the nonbinding conformation.

Epithelial integrity in metazoan organs is maintained through the regulated proliferation and differentiation of organ-specific stem and progenitor cells. Although the epithelia of organs such as the intestine regenerate constantly and thus remain continuously proliferative, other organs, such as the mammalian urinary bladder, shift from near-quiescence to a highly proliferative state in response to epithelial injury. The cellular and molecular mechanisms underlying this injury-induced mode of regenerative response are poorly defined. Here we show in mice that the proliferative response to bacterial infection or chemical injury within the bladder is regulated by signal feedback between basal cells of the urothelium and the stromal cells that underlie them. We demonstrate that these basal cells include stem cells capable of regenerating all cell types within the urothelium, and are marked by expression of the secreted protein signal Sonic hedgehog (Shh). On injury, Shh expression in these basal cells increases and elicits increased stromal expression of Wnt protein signals, which in turn stimulate the proliferation of both urothelial and stromal cells. The heightened activity of this signal feedback circuit and the associated increase in cell proliferation appear to be required for restoration of urothelial function and, in the case of bacterial injury, may help clear and prevent further spread of infection. Our findings provide a conceptual framework for injury-induced epithelial regeneration in endodermal organs, and may provide a basis for understanding the roles of signalling pathways in cancer growth and metastasis., (©2011 Macmillan Publishers Limited. All rights reserved)

Background: Pelvic pain is a major component of the morbidity associated with urinary tract infection (UTI), yet the molecular mechanisms underlying UTI-induced pain remain unknown. UTI pain mechanisms probably contrast with the clinical condition of asymptomatic bacteriuria (ASB), characterized by significant bacterial loads without lack symptoms., Methods: A murine UTI model was used to compare pelvic pain behavior elicited by infection with uropathogenic Escherichia coli strain NU14 and ASB strain 83972., Results: NU14-infected mice exhibited pelvic pain, whereas mice infected with 83972 did not exhibit pain, similar to patients infected with 83972. NU14-induced pain was not dependent on mast cells, not correlated with bacterial colonization or urinary neutrophils. UTI pain was not influenced by expression of type 1 pili, the bacterial adhesive appendages that induce urothelial apoptosis. However, purified NU14 lipopolysaccharide (LPS) induced Toll-like receptor 4 (TLR4)-dependent pain, whereas 83972 LPS induced no pain. Indeed, 83972 LPS attenuated the pain of NU14 infection, suggesting therapeutic potential., Conclusions: These data suggest a novel mechanism of infection-associated pain that is dependent on TLR4 yet independent of inflammation. Clinically, these findings also provide the rational for probiotic therapies that would minimize the symptoms of infection without reliance on empirical therapies that contribute to antimicrobial resistance.

Strains of uropathogenic Escherichia coli (UPEC) encode filamentous adhesive organelles called type 1 pili that promote bacterial colonization and invasion of the bladder epithelium. Type 1 pilus-mediated interactions with host receptors, including alpha3beta1 integrin, trigger localized actin rearrangements that lead to internalization of adherent bacteria via a zipper-like mechanism. Here we report that type 1 pilus-mediated bacterial invasion of bladder cells also requires input from host microtubules and histone deacetylase 6 (HDAC6), a cytosolic enzyme that, by deacetylating alpha-tubulin, can alter the stability of microtubules along with the recruitment and directional trafficking of the kinesin-1 motor complex. We found that disruption of microtubules by nocodazole or vinblastine treatment, as well as microtubule stabilization by taxol, inhibited host cell invasion by UPEC, as did silencing of HDAC6 expression or pharmacological inhibition of HDAC6 activity. Invasion did not require two alternate HDAC6 substrates, Hsp90 and cortactin, but was dependent upon the kinesin-1 light chain KLC2 and an upstream activator of HDAC6, aurora A kinase. These results indicate that HDAC6 and microtubules act as vital regulatory elements during the invasion process, possibly via indirect effects on kinesin-1 and associated cargos.

Components of bacteria have been shown to induce innate antiviral immunity via Toll-like receptors (TLRs). We have recently shown that FimH, the adhesin portion of type 1 fimbria, can induce the innate immune system via TLR4. Here we report that FimH induces potent in vitro and in vivo innate antimicrobial responses. FimH induced an innate antiviral state in murine macrophage and primary MEFs which was correlated with IFN-beta production. Moreover, FimH induced the innate antiviral responses in cells from wild type, but not from MyD88(-/-), Trif(-/-), IFN-alpha/betaR(-/-) or IRF3(-/-) mice. Vaginal delivery of FimH, but not LPS, completely protected wild type, but not MyD88(-/-), IFN-alpha/betaR(-/-), IRF3(-/-) or TLR4(-/-) mice from subsequent genital HSV-2 challenge. The FimH-induced innate antiviral immunity correlated with the production of IFN-beta, but not IFN-alpha or IFN-gamma. To examine whether FimH plays a role in innate immune induction in the context of a natural infection, the innate immune responses to wild type uropathogenic E. coli (UPEC) and a FimH null mutant were examined in the urinary tract of C57Bl/6 (B6) mice and TLR4-deficient mice. While UPEC expressing FimH induced a robust polymorphonuclear response in B6, but not TLR4(-/-) mice, mutant bacteria lacking FimH did not. In addition, the presence of TLR4 was essential for innate control of and protection against UPEC. Our results demonstrate that FimH is a potent inducer of innate antimicrobial responses and signals differently, from that of LPS, via TLR4 at mucosal surfaces. Our studies suggest that FimH can potentially be used as an innate microbicide against mucosal pathogens.

Background: Mast cells trigger inflammation that is associated with local pain, but the mechanisms mediating pain are unclear. Interstitial cystitis (IC) is a bladder disease that causes debilitating pelvic pain of unknown origin and without consistent inflammation, but IC symptoms correlate with elevated bladder lamina propria mast cell counts. We hypothesized that mast cells mediate pelvic pain directly and examined pain behavior using a murine model that recapitulates key aspects of IC., Methods and Findings: Infection of mice with pseudorabies virus (PRV) induces a neurogenic cystitis associated with lamina propria mast cell accumulation dependent upon tumor necrosis factor alpha (TNF), TNF-mediated bladder barrier dysfunction, and pelvic pain behavior, but the molecular basis for pelvic pain is unknown. In this study, both PRV-induced pelvic pain and bladder pathophysiology were abrogated in mast cell-deficient mice but were restored by reconstitution with wild type bone marrow. Pelvic pain developed normally in TNF- and TNF receptor-deficient mice, while bladder pathophysiology was abrogated. Conversely, genetic or pharmacologic disruption of histamine receptor H1R or H2R attenuated pelvic pain without altering pathophysiology., Conclusions: These data demonstrate that mast cells promote cystitis pain and bladder pathophysiology through the separable actions of histamine and TNF, respectively. Therefore, pain is independent of pathology and inflammation, and histamine receptors represent direct therapeutic targets for pain in IC and other chronic pain conditions.

The initial treatment of bladder cancer is transurethral resection (TUR), but this cancer recurs at an important rate, and has 14% chance of progression after TUR alone. Intravesical chemotherapy with Bacillus Calmette-Guerin (BCG) is effective against recurrence and progression of bladder cancer. However, this therapeutic expose to many local and systemic side-effects. We report a case of 63-year-old man who presented bladder tuberculosis after a BCG therapy, which required 6 months of antitubercular therapy.

The role of dendritic cells (DC) in urinary tract infections (UTI) is unknown. These cells contribute directly to the innate defense against various viral and bacterial infections. Here, we studied their role in UTI using an experimental model induced by transurethral instillation of the uropathogenic Escherichia coli (UPEC) strain 536 into C57BL/6 mice. While few DC were found in the uninfected bladder, many had been recruited after 24 h, mostly to the submucosa and uroepithelium. They expressed markers of activation and maturation and exhibited the CD11b+ F4/80+ CD8- Gr-1- myeloid subtype. Also, tumor necrosis factor alpha (TNF-alpha)- and inducible nitric oxide synthase (iNOS)-producing CD11bINT DC (Tip-DC) were detected, which recently were proposed to be critical in the defense against bacterial infections. However, Tip-DC-deficient CCR2-/- mice did not show reduced clearance of UPEC from the infected bladder. Moreover, clearance was also unimpaired in CD11c-DTR mice depleted of all DC by injection of diphtheria toxin. This may be explained by the abundance of granulocytes and of iNOS- and TNF-alpha-producing non-DC that were able to replace Tip-DC functionality. These findings demonstrate that some of the abundant DC recruited in UTI contributed innate immune effector functions, which were, however, dispensable in the microenvironment of the bladder.

A first step in urinary tract infection (UTI) pathogenesis in the otherwise healthy host is the movement of uropathogenic Escherichia coli from the intestinal tract to the urinary tract. We conducted a genomic subtraction to isolate genetic regions associated with this movement. A representative UTI isolate present in the rectum, vagina, and bladder of a woman with UTI was chosen as the tester; the driver was a phylogenetically distant rectal isolate (based on pulsed-field gel electrophoresis analysis) with a profile of uropathogenic virulence genes similar to that of the tester. Tester-specific regions identified by the subtraction were screened, using DNA dot blot hybridization, against a collection of 88 uropathogens isolated from the rectum, urine, and/or vagina of women with UTIs and 54 E. coli isolates from the same women that were found only in the rectum. Twelve genetic regions occurred more often in multisite isolates than in rectal site-only isolates. Eleven of these 12 genetic regions are homologous to regions in the sequenced uropathogenic E. coli CFT073 strain.

This report describes an elderly patient with urinary symptoms who showed surface colonisation of the transitional mucosa of the bladder by an unusual haematoxophilic microorganism superficially resembling the "blue fuzz" seen in colonic biopsies showing intestinal spirochaetosis. Special stains showed that the organisms were Gram and Giemsa positive, weakly argyrophilic, and Ziehl-Nielsen negative. Immunostains were negative for Helicobacter pylori and electron microscopy revealed curious curved bodies, which were difficult to classify. Therefore, this condition was described as pseudospirochaetosis of the urinary bladder. The urinary symptoms regressed on treatment with ciprofloxacin. The clinicopathological relevance of these findings is discussed in the report.

Escherichia coli entry into the bladder is met with potent innate defenses, including neutrophil influx and epithelial exfoliation. Bacterial subversion of innate responses involves invasion into bladder superficial cells. We discovered that the intracellular bacteria matured into biofilms, creating pod-like bulges on the bladder surface. Pods contained bacteria encased in a polysaccharide-rich matrix surrounded by a protective shell of uroplakin. Within the biofilm, bacterial structures interacted extensively with the surrounding matrix, and biofilm associated factors had regional variation in expression. The discovery of intracellular biofilm-like pods explains how bladder infections can persist in the face of robust host defenses.

A gram-negative Buttiauxella gaviniae-like organism (LBV449) was isolated from a urine sample of a patient suffering from urine bladder pathology and neurological problems. The isolate was positive for adonitol fermentation and L-arginine dihydrolase and negative for melibiose and L-ornithine decarboxylase. The API 20E code was 3004113. Retrospectively, another isolate (ENT107), from a leg wound, was recovered from our collections and was shown to have similar biochemical characteristics. DNA-DNA hybridization showed 77% similarity between both strains, and strain LBV449 revealed 74% DNA-DNA similarity to the type strain of B. gaviniae. Neither 16S rRNA gene sequencing nor fatty acid analysis were useful for identification. The characteristic tRNA-PCR patterns obtained for these two clinical isolates consisted of fragments with lengths of 102.2, 105.4, 116.6, and 136.9 bp and most resembled the tRNA-PCR pattern obtained for B. gaviniae, but they lacked the B. gaviniae fragments of 88.2 and 239.5 bp. To our knowledge, no clinical cases with Buttiauxella strains have been described thus far.

We have previously shown (M. Aronson, O. Medalia, D. Amichay, and O. Nativ, Infect. Immun. 56:1615-1617, 1988) that shedding of viable uroepithelial cells (elicited by invading microorganisms) constitutes an antimicrobial defense mechanism. The present study deals with two different stress-involving procedures, in which increased uroepithelial shedding rendered female mice resistant to vesical infection. Moderate stress was induced in female mice by exposing the animals either to constant illumination for 96 h or to 37 degrees C heat for 24 h. In both cases, the rate of infection was considerably reduced as a result of increased epithelial shedding (P < 0.0001). Stress was manifested by both reduced thymic weight and increased blood corticosterone levels. Shedding was also elicited by intraperitoneal injection of norepinephrine together with hydrocortisone or by intravesical injection of corticosterone. Constant illumination as well as heat enormously facilitated the migration of polymorphonuclear cells into the bladder following the action of chemotactic stimuli. Male mice subjected to identical stress-generating conditions did not display considerable epithelial shedding or increased migration of polymorphonuclear cells, and they were not protected from intravesical infection.

Objective: To study the effectiveness of preoperative bladder washing with povidone-iodine to prevent postprostatectomy wound infection., Design: Patients with an indwelling catheter and scheduled for prostatectomy were divided into two groups. In patients in group 1 (n = 76) the indwelling catheter was simply removed without bladder irrigation. Patients in group 2 (n = 80) had their bladder washed with a nondiluted solution of povidone-iodine before surgery., Patients: One hundred fifty-six consecutive patients with an indwelling catheter and bacteriuria. Mean age was 64 years. All patients had an open prostatectomy during the 12-month study period. Patients undergoing open prostatectomy during the first 6 months of the study had no bladder irrigation and served as the control group. Patients undergoing open prostatectomy during the following 6 months had a bladder instillation with povidone-iodine., Results: Wound infection appeared in 17 of 76 patients (22.4%) without bladder washing and in 4 of 80 patients (5%) when 50 to 60 ml of the solution was retained in the bladder for 10 to 13 minutes (p = .001). The incidence of postoperative bacteriuria remained unchanged in the control group (100%) but was reduced to 22.5% in the treated group (p = .001). Statistical comparisons of incidence were done using the chi square test., Conclusions: It has been demonstrated that the use of preoperative bladder instillation of povidone-iodine may be highly effective in the prevention of postprostatectomy wound infection and in reducing the incidence of bacteriuria in patients with an indwelling catheter and urine colonization.

A healthy 54 year old man was investigated for haematuria. In spite of a proven urinary tract infection a cystoscopy was carried out with no antibiotic therapy. As a result he developed systemic infection leading to two independent, and potentially fatal, complications: vertebral osteomyelitis and a mycotic false aneurysm.

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.

Quantitative culture of midstream urine fails to yield a significant microorganism in many patients with acute urinary symptoms. We cultured bladder urine, obtained by aspiration, from symptomatic adults with equivocal findings on standard testing of midstream urine for low numbers of conventional uropathogens and fastidious bacteria. We found 561 (31%) of 1817 women and 36 (12%) of 300 men to be culture positive. Five hundred eighty-one (70%) of 830 isolates were fastidious bacteria; 191 (34%) of 561 culture positive women and 0 of 36 culture-positive men had polymicrobic bacteriuria. Bacterial counts were less than 10(5) colony-forming units/mL in 67% of samples; 204 of 406 patients with single-species infections had increased leukocyte counts in urine. Patients with symptoms of urinary tract infection who are culture negative on standard testing may harbor fastidious bacteria or low numbers of conventional uropathogens in the bladder. In these patients, culture of bladder aspiration urine for low counts and fastidious species is necessary to diagnose bacteriuria.

The possible role of pili in the pathogenesis of urinary tract infection caused by Klebsiella pneumoniae was investigated in a rat model of cystitis by utilizing piliated- and nonpiliated-phase organisms derived from a single parent strain. Bladder surfaces were examined for evidence of infection by scanning electron microscopy. In animals infected with piliated-phase organisms, foci of infection were evident in the majority of bladders examined. Rat bladders associated with nonpiliated-phase bacteria showed little evidence of infection. The ability of methyl-D-mannoside, a known inhibitor of pilus-mediated adherence to mammalian cells, to protect the bladder surface from colonization was also tested. The results showed a significant decrease in the ability of piliated-phase K. pneumoniae to establish infection in bladders. These observations suggest that pili may play an integral role in the ability of K. pneumoniae to cause urinary tract infections by mediating the attachment of the bacteria to the uroepithelial surface.

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.

The response of a sensitive strain of Escherichia coli to a variety of antibiotics was examined in an in vitro model which simulates the hydrokinetic features of the urinary bladder. Recovery of bacterial cultures from antibiotic effects was observed following exposure to bactericidal and bacteristatic antibiotics and no substantial difference was noted between the effectiveness of bacteristatic and bactericidal agents except that bacteristatic antibiotics were more influenced by alteration of the conditions of "diuresis" and "frequency of micturition". The response of dense bacterial populations to high concentrations of 3 beta-lactam antibiotics varied markedly under the different hydrokinetic conditions. Possible reasons for these variations are discussed.

Sixty-two gnotobiotic pigs were used in three experiments to determine the means whereby two related strains of Escherichia coli colonized the intestinal tract. Pigs were exposed by a method simulating neonatal contamination of the umbilical stump. Bacteremia was produced within one and one half hours, and by 24 hours the infection was generally well established in the gastrointestinal tract. By 48 hours after exposure, the bacteremia had subsided so that only an occasional isolation from organs other than the gastrointestinal tract was made. Oral exposure of one litter of germfree pigs produced heavy colonization of the entire gastrointestinal tract within four hours. Evidence of intermittent bacteremia was present in pigs of this litter. Diarrhea appeared earlier when pigs were exposed orally than when they were exposed by way of the umbilical stump.