Recurrence of urinary tract infections in adult patients with community-acquired pyelonephritis caused by E. coli: a 1-year follow-up

Longitudinal molecular analysis of clinical and fecal Escherichia coli isolates at a Veterans Affairs Medical Center in Minnesota, USA, 2012-2019

Introduction

Extraintestinal Escherichia coli infections represent a growing public health threat, However, current studies often overlook important factors such as temporal patterns of infection, phylogenetic and clonal background, or the host gut E. coli population, despite their likely significance.

Methods

In this study, we analyzed >7000 clinical E. coli isolates from patients at the Minneapolis Veterans Affairs Health Care System (2012-2019), and concurrent fecal E. coli from uninfected veterans. We assessed phylogenetic group distribution, membership in selected sequence types (STs), and subsets thereof-including the pandemic, resistance-associated ST131-H30R, and ST1193 lineages-and strain type, as defined by pulsed-field gel electrophoresis. We then analyzed these features alongside the temporal patterns of infection in individual hosts.

Results

The H30R lineage emerged as the leading lineage, both overall and among fluoroquinolone-resistant isolates, with ST1193 following among fluoroquinolone-resistant isolates. Recurrences were common, occurring in 31% of subjects and 41% of episodes, and often multiple and delayed/prolonged (up to 23 episodes per subject; up to 2655d post-index). Remarkably, these recurrences typically involved the subject's index strain (63% of recurrences), even when affecting extra-urinary sites. ST131, H30R, ST1193, and fluoroquinolone-resistant strains generally caused significantly more recurrences than did other strains, despite similar recurrence intervals. ST131 strain types shifted significantly over the study period. Infection-causing strains were commonly detectable in host feces at times other than during an infection episode; the likelihood of detection varied with surveillance intensity and proximity to the infection. H30R and ST1193 were prominent causes of fecal-clinical clonal overlap.

Discussion

These findings provide novel insights into the temporal and clonal characteristics of E. coli infections in veterans and support efforts to develop anti-colonization interventions.

Characterization of host and escherichia coli strains causing recurrent urinary tract infections based on molecular typing

BACKGROUND

Escherichia coli is the leading pathogen responsible for urinary tract infection (UTI) and recurrent UTI (RUTI). Few studies have dealt with the characterization of host and bacteria in RUTI caused by E. coli with genetically identical or different strains. This study aimed to investigate the host and bacterial characteristics of E. coli RUTI based on molecular typing.

RESULTS

Patients aged 20 years or above who presented with symptoms of UTI in emergency department or outpatient clinics between August 2009 and December 2010 were enrolled. RUTI was defined as patients had 2 or more infections in 6 months or 3 or more in 12 months during the study period. Host factors (including age, gender, anatomical/functional defect, and immune dysfunction) and bacterial factors (including phylogenicity, virulence genes, and antimicrobial resistance) were included for analysis. There were 41 patients (41%) with 91 episodes of E. coli RUTI with highly related PFGE (HRPFGE) pattern (pattern similarity > 85%) and 58 (59%) patients with 137 episodes of E. coli RUTI with different molecular typing (DMT) pattern, respectively. There was a higher prevalence of phylogenetic group B2 and neuA and usp genes in HRPFGE group if the first episode of RUTI caused by HRPFGE E. coli strains and all episodes of RUTI caused by DMT E. coli strains were included for comparison. The uropathogenic E. coli (UPEC) strains in RUTI were more virulent in female gender, age < 20 years, neither anatomical/ functional defect nor immune dysfunction, and phylogenetic group B2. There were correlations among prior antibiotic therapy within 3 months and subsequent antimicrobial resistance in HRPFGE E. coli RUTI. The use of fluoroquinolones was more likely associated with subsequent antimicrobial resistance in most types of antibiotics.

CONCLUSIONS

This study demonstrated that the uropathogens in RUTI were more virulent in genetically highly-related E. coli strains. Higher bacterial virulence in young age group (< 20 years) and patients with neither anatomical/functional defect nor immune dysfunction suggests that virulent UPEC strains are needed for the development of RUTI in healthy populations. Prior antibiotic therapy, especially the fluoroquinolones, within 3 months could induce subsequent antimicrobial resistance in genetically highly-related E. coli RUTI.

Escherichia coli Causing Recurrent Urinary Tract Infections: Comparison to Non-Recurrent Isolates and Genomic Adaptation in Recurrent Infections

Recurrent urinary tract infection (rUTI) remains a major problem for many women and therefore the pursuit for genomic and phenotypic traits which could define rUTI has been ongoing. The present study applied a genomic approach to investigate recurrent urinary tract infections by comparative analyses of recurrent and non-recurrent Escherichia coli isolates from general practice. From whole-genome sequencing data, phylogenetic clustering and genomic traits were studied on a collection of isolates which caused recurrent infection compared to non-recurrent isolates. In addition, genomic variation between the 1st and following infection was studied on a subset of the isolates. Evidence of limited adaptation between the recurrent infections based on single nucleotide polymorphism analyses with a range of 0-13 non-synonymous single nucleotide polymorphisms (SNPs) between the paired isolates. This included an overrepresentation of SNPs in metabolism genes. We identified several genes which were more common in rUTI isolates, including nine fimbrial genes, however, not significantly after false-discovery rate. Finally, the results show that recurrent isolates of the present dataset are not distinctive by variation in the core genome, and thus, did not cluster distinct from non-rUTI isolates in a SNP phylogeny.

The gene profile of Enterobacteriaceae virulence factors in relation to bacteriuria levels between the acute episodes of recurrent uncomplicated lower urinary tract infection

OBJECTIVES

The pathogenic potential of uropathogens isolated between acute episodes of recurrent lower urinary tract infection (rLUTI) is studied insufficiently. The objectives were to determine the spectrum of virulence genes of Enterobacteriaceae cultured between acute episodes of rLUTI at various levels of bacteriuria.

METHODS

Bacteriological examinations of 169 premenopausal women's midstream urine with rLUTI were performed between acute episodes of UTI. Sixty-two strains of Enterobacteriaceae at concentrations 10²-10⁸ CFU/ml were analyzed for the presence of papA, papE/F, papGII, afa, bmaE, iutA, feoB, fyuA, kpsMTII, and usp virulence factors genes' (VFGs) fragments.

RESULTS

In all strains VFGs were found with numbers from 1 to 10. Four VFGs were found at all levels of bacteriuria (from 10² to 10^7-8) in most strains (>50%): papGII, feoB, fyuA, usp. In total, 28 significant Pearson contingency coefficient (PCC) were determined. Each of the genes, papA, papE/F, usp, was found more often in uropathogens from patients with a higher level of leukocyturia.

CONCLUSIONS

The inter-episode period in rLUTI is associated with varying levels of bacteriuria of enterobacteria. Since enterobacteria virulent potential could be determined at all levels of bacteriuria, there is at all levels of bacteriuria a potential risk for recurrence of LUTI.

Recurrence of urinary tract infections with extended-spectrum β-lactamase-producing Escherichia coli caused by homologous strains among which clone ST131-O25b is dominant

OBJECTIVES

Bacterial features associated with recurrent urinary tract infections (RUTIs) due to extended-spectrum β-lactamase-producingEscherichia coli (ESBL-E. coli) are not well understood. In this study, phylogenetic groups and ST131 subclones were investigated to assess strain homology of ESBL-E. coli isolates in patients with RUTIs in inpatient and outpatient settings in western Sweden.

METHODS

Almost all isolates (319/356) from 123 patients with 2-7 episodes (median 2 episodes) of ESBL-E. coli UTI within 1 year were examined for seven E. coli phylogroups, the ST131-O25b clone and its subclone fimH30-Rx. Antimicrobial resistance and ESBL genes were determined for the index isolates. A subset of isolates was typed using pulsed-field gel electrophoresis (PFGE).

RESULTS

The same phylogroup and ST131 subclones were seen for all recurrences in 119/123 patients, and PFGE confirmed strain homology in recurrences for 43/44 patients tested. Phylogroup B2 dominated (56%), followed by D (19%) and F (10%). ST131-O25b andfimH30-Rx isolates were detected in 44% and 30%, respectively. CTX-M group 1 (71%) predominated. Elderly patients were in the majority. There were no associations between patient demographics or time to recurrence and bacterial characteristics. The fimH30-Rx subclone was associated with a higher number of recurrences (P = 0.015) compared with the remaining B2 isolates.

CONCLUSION

In ESBL-E. coli RUTI, most recurrences were caused by the initial infecting strain. The high frequency of the multidrug-resistant fimH30-Rx subclone and its association with multiple recurrences warrants further attention and early detection of this subclone in patients at risk of developing RUTI with ESBL-E. coli.

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) are important pathogens in humans and certain animals. Molecular epidemiological analyses of ExPEC are based on structured observations of E. coli strains as they occur in the wild. By assessing real-world phenomena as they occur in authentic contexts and hosts, they provide an important complement to experimental assessment. Fundamental to the success of molecular epidemiological studies are the careful selection of subjects and the use of appropriate typing methods and statistical analysis. To date, molecular epidemiological studies have yielded numerous important insights into putative virulence factors, host-pathogen relationships, phylogenetic background, reservoirs, antimicrobial-resistant strains, clinical diagnostics, and transmission pathways of ExPEC, and have delineated areas in which further study is needed. The rapid pace of discovery of new putative virulence factors and the increasing awareness of the importance of virulence factor regulation, expression, and molecular variation should stimulate many future molecular epidemiological investigations. The growing sophistication and availability of molecular typing methodologies, and of the new computational and statistical approaches that are being developed to address the huge amounts of data that whole genome sequencing generates, provide improved tools for such studies and allow new questions to be addressed.

Subsequent infection with extended-spectrum β-lactamase-producing Enterobacteriaceae in patients with prior infection or fecal colonization

In clinical practice, there is a growing need to assess the impact of prior colonization or infection with extended-spectrum β-lactamase-producing Enterobacteriaceae (EPE) on new EPE infections. We have investigated the frequency of, and duration to, a subsequent EPE infection in patients with prior fecal carriage or infection with EPE. Culture data for 3272 EPE-positive patients in Western Sweden during 2004-2014 were evaluated. The median follow-up time was 3.7 years. The first recorded EPE-positive fecal screen, or clinical (urine, blood) culture, and subsequent EPE-positive clinical samples were analyzed, focusing on the first and last recurrence of EPE infection. ESBL Escherichia coli dominated (95%). Almost all (94%) patients initially positive in fecal screen (n = 1436) and 72 and 71% of those initially positive in urine (n = 1717) and blood (n = 119) had no further EPE clinical isolates. Subsequent EPE bacteremia was only detected in 0.7, 1.6, and 4.2% of the respective patient group. Recurrent EPE-positive urine cultures occurred in 27% (460/1717), most (75%) within 6 months, and rarely (13%) after 1 year. Repeated EPE-positive clinical samples were significantly (p < 0.01) more common in patients > 65 years and in men with ESBL Klebsiella pneumoniae. In our low-endemic setting, subsequent EPE infections in previously colonized patients were rare. On the other hand, in patients previously EPE-positive in urine or blood, subsequent EPE urinary tract infections were common, especially within 6 months and in patients > 65 years old.

Cell death-based approaches in treatment of the urinary tract-associated diseases: a fight for survival in the killing fields

Urinary tract-associated diseases comprise a complex set of disorders with a variety of etiologic agents and therapeutic approaches and a huge global burden of disease, estimated at around 1 million deaths per year. These diseases include cancer (mainly prostate, renal, and bladder), urinary tract infections, and urolithiasis. Cell death plays a key role in the pathogenesis and therapy of these conditions. During urinary tract infections, invading bacteria may either promote or prevent host cell death by interfering with cell death pathways. This has been studied in detail for uropathogenic E. coli (UPEC). Inhibition of host cell death may allow intracellular persistence of live bacteria, while promoting host cell death causes tissue damage and releases the microbes. Both crystals and urinary tract obstruction lead to tubular cell death and kidney injury. Among the pathomechanisms, apoptosis, necroptosis, and autophagy represent key processes. With respect to malignant disorders, traditional therapeutic efforts have focused on directly promoting cancer cell death. This may exploit tumor-specific characteristics, such as targeting Vascular Endothelial Growth Factor (VEGF) signaling and mammalian Target of Rapamycin (mTOR) activity in renal cancer and inducing survival factor deprivation by targeting androgen signaling in prostate cancer. An area of intense research is the use of immune checkpoint inhibitors, aiming at unleashing the full potential of immune cells to kill cancer cells. In the future, this may be combined with additional approaches exploiting intrinsic sensitivities to specific modes of cell death such as necroptosis and ferroptosis. Here, we review the contribution of diverse cell death mechanisms to the pathogenesis of urinary tract-associated diseases as well as the potential for novel therapeutic approaches based on an improved molecular understanding of these mechanisms.

Distribution of virulence determinants among antimicrobial-resistant and antimicrobial-susceptible Escherichia coli implicated in urinary tract infections

INTRODUCTION

Uropathogenic Escherichia coli (UPEC) rely on the correlation of virulence expression with antimicrobial resistance to persist and cause severe urinary tract infections (UTIs).

OBJECTIVES

We assessed the virulence pattern and prevalence among UPEC strains susceptible and resistant to multiple antimicrobial classes.

METHODS

A total of 174 non-duplicate UPEC strains from patients with clinically significant UTIs were analysed for susceptibility to aminoglycoside, antifolate, cephalosporin, nitrofuran and quinolone antibiotics for the production of extended-spectrum β-lactamases and for the presence of six virulence determinants encoding adhesins (afimbrial, Type 1 fimbriae, P and S-fimbriae) and toxins (cytotoxic necrotising factor and haemolysin).

RESULTS

Relatively high resistance rates to nalidixic acid, ciprofloxacin, cephalothin and trimethoprim-sulfamethoxazole (82%, 78%, 62% and 59%, respectively) were observed. Fourteen distinct patterns were identified for the virulence determinants such as afaBC, cnfI, fimH, hylA, papEF and sfaDE. The toxin gene, cnfI (75.3%), was the second most prevalent marker to the adhesin, fimH (97.1%). The significant association of sfaDE/hylA (P < 0.01) among antimicrobial resistant and susceptible strains was also observed notwithstanding an overall greater occurrence of virulence factors among the latter.

CONCLUSIONS

This study provides a snapshot of UPEC complexity in Jamaica and highlights the significant clonal heterogeneity among strains. Such outcomes emphasise the need for evidence-based strategies in the effective management and control of UTIs.

Lipopolysaccharide Domains Modulate Urovirulence

Uropathogenic Escherichia coli (UPEC) accounts for 80 to 90% of urinary tract infections (UTI), and the increasing rate of antibiotic resistance among UPEC isolates reinforces the need for vaccines to prevent UTIs and recurrent infections. Previous studies have shown that UPEC isolate NU14 suppresses proinflammatory NF-κB-dependent cytokines (D. J. Klumpp, A. C. Weiser, S. Sengupta, S. G. Forrestal, R. A. Batler, and A. J. Schaeffer, Infect Immun 69:6689-6695, 2001, http://dx.doi.org/10.1128/IAI.69.11.6689-6695.2001; B. K. Billips, A. J. Schaeffer, and D. J. Klumpp, Infect Immun 76:3891-3900, 2008, http://dx.doi.org/10.1128/IAI.00069-08). However, modification of lipopolysaccharide (LPS) structure by deleting the O-antigen ligase gene (waaL) enhanced proinflammatory cytokine secretion. Vaccination with the ΔwaaL mutant diminished NU14 reservoirs and protected against subsequent infections. Therefore, we hypothesized that LPS structural determinants shape immune responses. We evaluated the contribution of LPS domains to urovirulence corresponding to the inner core (waaP, waaY, and rfaQ), outer core (rfaG), and O-antigen (waaL, wzzE, and wzyE). Deletion of waaP, waaY, and rfaG attenuated adherence to urothelial cells in vitro In a murine UTI model, the ΔrfaG mutant had the most severe defect in colonization. The mutation of rfaG, waaL, wzzE, and wzyE resulted in an inability to form reservoirs in mouse bladders. Infection with the LPS mutant panel resulted in various levels of urinary myeloperoxidase. Since the ΔwaaL mutant promoted Th₁-associated adaptive responses in previous studies (B. K. Billips, R. E. Yaggie, J. P. Cashy, A. J. Schaeffer, and D. J. Klumpp, J Infect Dis 200:263-272, 2009, http://dx.doi.org/10.1086/599839), we assessed NU14 for Th₂-associated cytokines. We found NU14 infection stimulated TLR4-dependent bladder interleukin-33 (IL-33) production. Inoculation with rfaG, waaL, wzzE, and wzyE mutants showed decreased IL-33 production. We quantified antigen-specific antibodies after infection and found significantly increased IgE and IgG1 in ΔwaaP mutant-infected mice. Our studies show LPS structural constituents mediate multiple aspects of the UPEC life cycle, including the ability to acutely colonize bladders, form reservoirs, and evoke innate and adaptive immune responses.

Antivirulence C-Mannosides as Antibiotic-Sparing, Oral Therapeutics for Urinary Tract Infections

Gram-negative uropathogenic Escherichia coli (UPEC) bacteria are a causative pathogen of urinary tract infections (UTIs). Previously developed antivirulence inhibitors of the type 1 pilus adhesin, FimH, demonstrated oral activity in animal models of UTI but were found to have limited compound exposure due to the metabolic instability of the O-glycosidic bond (O-mannosides). Herein, we disclose that compounds having the O-glycosidic bond replaced with carbon linkages had improved stability and inhibitory activity against FimH. We report on the design, synthesis, and in vivo evaluation of this promising new class of carbon-linked C-mannosides that show improved pharmacokinetic (PK) properties relative to O-mannosides. Interestingly, we found that FimH binding is stereospecifically modulated by hydroxyl substitution on the methylene linker, where the R-hydroxy isomer has a 60-fold increase in potency. This new class of C-mannoside antagonists have significantly increased compound exposure and, as a result, enhanced efficacy in mouse models of acute and chronic UTI.

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC), the specialized E. coli strains that possess the ability to overcome or subvert host defenses and cause extraintestinal disease, are important pathogens in humans and certain animals. Molecular epidemiological analysis has led to an appreciation of ExPEC as being distinct from other E. coli (including intestinal pathogenic and commensal variants) and has offered insights into the ecology, evolution, reservoirs, transmission pathways, host-pathogen interactions, and pathogenetic mechanisms of ExPEC. Molecular epidemiological analysis also provides an essential complement to experimental assessment of virulence mechanisms. This chapter first reviews the basic conceptual and methodological underpinnings of the molecular epidemiological approach and then summarizes the main aspects of ExPEC that have been investigated using this approach.

Effectiveness of an association of a cranberry dry extract, D-mannose, and the two microorganisms Lactobacillus plantarum LP01 and Lactobacillus paracasei LPC09 in women affected by cystitis: a pilot study

BACKGROUND

Urinary tract infections (UTIs) are the most common bacterial infection in women. Most UTIs are acute uncomplicated cystitis caused by Escherichia coli (86%). This study was undertaken to assess the effectiveness of an association of a cranberry dry extract, D-mannose, a gelling complex composed of the exopolysaccharides produced by Streptococcus thermophilus ST10 (DSM 25246) and tara gum, as well as the 2 microorganisms Lactobacillus plantarum LP01 (LMG P-21021) and Lactobacillus paracasei LPC09 (DSM 24243) in women affected by acute uncomplicated cystitis.

MATERIALS AND METHODS

Thirty-three premenopausal, nonpregnant women diagnosed with acute uncomplicated cystitis were enrolled in a pilot prospective study and completed the treatment protocol. Subjects were instructed to take 2 doses per day during the first month, and then to continue with 1 sachet per day until the sixtieth day. Nitrites and leukocyte esterase on urine dipstick testing were used as indicators of cystitis, with analysis performed at enrollment, after 30 and 60 days, and after 1 month of follow-up. Typical UTI symptoms, namely dysuria, frequent voiding of small volumes, urinary urgency, suprapubic pain, and gross hematuria were scored 0 to 3 and evaluated at each visit.

RESULTS

Positive results for the presence of nitrites and leukocyte esterase were found in 14 and 20 subjects after 30 days and in 9 and 14 women after 60 days, respectively (P<0.001). At the end of the follow-up period, positive results for nitrites and leukocyte esterase were recorded in only 4 and 3 of 24 and 19 subjects (16.7%, P=0.103; 15.8%, P=0.325, respectively), with negative results after 60 days. Typical symptoms of cystitis, specifically dysuria, frequent voiding, urgency, and suprapubic pain were significantly improved as well. No significant differences were recorded in the incidence and severity of hematuria at any visit.

CONCLUSION

The long-term ability of an association of cranberry, D-mannose, an innovative gelling complex, and the 2 microorganisms tested to significantly improve the uncomfortable symptoms reported by women with acute cystitis has been suggested.

From physiology to pharmacy: developments in the pathogenesis and treatment of recurrent urinary tract infections

Urinary tract infections (UTIs) are common, and over half of women report having had at least one in their lifetime. Nearly a third of these women experience recurrent UTI episodes, but the mechanisms of these recurrences are not fully elucidated. Frequent use of antimicrobials for treatment and prevention of UTIs and other infections has contributed to the evolution of multidrug-resistant microorganisms globally. This is a looming worldwide crisis that has created an urgent need for novel strategies for the treatment and prevention of UTIs. Furthering our understanding of the mechanisms of recurrent UTIs, from both host and bacterial perspectives, will be paramount in developing targeted management strategies. In this review, we discuss recent findings regarding recurrent UTIs in women, including progress in our understanding of the mechanisms of recurrence as well as emerging treatments.

Similarity and divergence of phylogenies, antimicrobial susceptibilities, and virulence factor profiles of Escherichia coli isolates causing recurrent urinary tract infections that persist or result from reinfection

In order to obtain a better molecular understanding of recurrent urinary tract infection (RUTI), we collected 75 cases with repeatedly occurring uncomplicated UTI. The genetic relationships among uropathogenic Escherichia coli (UPEC) isolates were analyzed by pulsed-field gel electrophoresis. While 39 (52%) of the RUTI cases were defined as "persistence" of the same strain as the primary infecting strain, 36 (48%) were characterized by "reinfection" with a new strain that is different from the primary strain. We then examined the antimicrobial susceptibilities and phylogenetic backgrounds of 39 persistence and 86 reinfection UPEC isolates, and screened 44 virulence factor (VF) genes. We found that isolates had significant differences in the following: placement in phylogenetic group B2 (41% versus 21%; P = 0.0193) and the presence of adhesin genes iha (49% versus 28%; P = 0.0233) and papG allele I' (51% versus 24%; P = 0.003), iron uptake genes fyuA (85% versus 58%; P = 0.0037), irp-2 (87% versus 65%; P = 0.0109), and iutA (87% versus 58%; P = 0.0014), and an aggregate VF score (median, 11 versus 9; P = 0.0030). In addition, 41% of persistence strains harbored three adhesin genes simultaneously, whereas 22% of reinfection isolates did (P = 0.0289). Moreover, 59% versus 29% (P = 0.0014) of persistence and reinfection isolates contained seven types of iron uptake genes. Taken together, the antimicrobial susceptibilities of UPEC isolates had little effect on the RUTI. Compared with reinfection strains, persistence UPEC isolates exhibited higher VF scores and carried more VF genes than may be involved in the development and progression of RUTI.

Managing recurrent urinary tract infections in women

Recurrent urinary infections are a common problem for women of all ages. Risk factors for urinary infection differ for pre- and postmenopausal women. Management strategies are well established, and include treatment of the acute symptomatic episode, and decreasing the frequency of subsequent episodes. This update focuses on the management of acute uncomplicated urinary infection, the most common bacterial infection in women.

New paradigms of urinary tract infections: Implications for patient management

Urinary tract infections (UTIs) represent one of the most commonly acquired diseases among the general population as well as hospital in-patients, yet remain difficult to effectively and consistently treat. High rates of recurrence, anatomic abnormalities, and functional disturbances of the urinary tract all contribute to the difficulty in management of these infections. However, recent advances reveal important molecular and genetic factors that contribute to bacterial invasion and persistence in the urinary tract, particularly for the most common causative agent, uropathogenic Escherichia coli. Recent studies using animal models of experimental UTIs have recently provided mechanistic insight into the clinical observations that question the effectiveness of antibiotic therapy in treatment. Ultimately, continuing research will be necessary to identify the best targets for effective treatment of this costly and widespread infectious disease.

Persistence of uropathogenic Escherichia coli in the face of multiple antibiotics

Numerous antibiotics have proven to be effective at ameliorating the clinical symptoms of urinary tract infections (UTIs), but recurrent and chronic infections continue to plague many individuals. Most UTIs are caused by strains of uropathogenic Escherichia coli (UPEC), which can form both extra- and intracellular biofilm-like communities within the bladder. UPEC also persist inside host urothelial cells in a more quiescent state, sequestered within late endosomal compartments. Here, we tested a panel of 17 different antibiotics, representing seven distinct functional classes, for their effects on the survival of the reference UPEC isolate UTI89 within both biofilms and host bladder urothelial cells. All but one of the tested antibiotics prevented UTI89 growth in broth culture, and most were at least modestly effective against bacteria present within in vitro-grown biofilms. In contrast, only a few of the antibiotics, including nitrofurantoin and the fluoroquinolones ciprofloxacin and sparfloxacin, were able to eliminate intracellular bacteria in bladder cell culture-based assays. However, in a mouse UTI model system in which these antibiotics reached concentrations in the urine specimens that far exceeded minimal inhibitory doses, UPEC reservoirs in bladder tissues were not effectively eradicated. We conclude that the persistence of UPEC within the bladder, regardless of antibiotic treatments, is likely facilitated by a combination of biofilm formation, entry of UPEC into a quiescent or semiquiescent state within host cells, and the stalwart permeability barrier function associated with the bladder urothelium.

Lactobacillus fermentum ME-3 - an antimicrobial and antioxidative probiotic

The paper lays out the short scientific history and characteristics of the new probiotic Lactobacillus fermentum strain ME-3 DSM-14241, elaborated according to the regulations of WHO/FAO (2002). L. fermentum ME-3 is a unique strain of Lactobacillus species, having at the same time the antimicrobial and physiologically effective antioxidative properties and expressing health-promoting characteristics if consumed. Tartu University has patented this strain in Estonia (priority June 2001, patent in 2006), Russia (patent in 2006) and the USA (patent in 2007). The paper describes the process of the identification and molecular typing of this probiotic strain of human origin, its deposition in an international culture collection, and its safety assessment by laboratory tests and testing on experimental animals and volunteers. It has been established that L. fermentum strain ME-3 has double functional properties: antimicrobial activity against intestinal pathogens and high total antioxidative activity (TAA) and total antioxidative status (TAS) of intact cells and lysates, and it is characterized by a complete glutathione system: synthesis, uptake and redox turnover. The functional efficacy of the antimicrobial and antioxidative probiotic has been proven by the eradication of salmonellas and the reduction of liver and spleen granulomas in Salmonella Typhimurium-infected mice treated with the combination of ofloxacin and L. fermentum strain ME-3. Using capsules or foodstuffs enriched with L. fermentum ME-3, different clinical study designs (including double-blind, placebo-controlled, crossover studies) and different subjects (healthy volunteers, allergic patients and those recovering from a stroke), it has been shown that this probiotic increased the antioxidative activity of sera and improved the composition of the low-density lipid particles (LDL) and post-prandial lipids as well as oxidative stress status, thus demonstrating a remarkable anti-atherogenic effect. The elaboration of the probiotic L. fermentum strain ME-3 has drawn on wide international cooperative research and has taken more than 12 years altogether. The new ME-3 probiotic-containing products have been successfully marketed and sold in Baltic countries and Finland.

Persistence of Escherichia coli clones and phenotypic and genotypic antibiotic resistance in recurrent urinary tract infections in childhood

We assessed the clonality of consecutive Escherichia coli isolates during the course of recurrent urinary tract infections (RUTI) in childhood in order to compare clonality with phenotypic antibiotic resistance patterns, the presence of integrons, and the presence of the sul1, sul2, and sul3 genes. Altogether, 78 urinary E. coli isolates from 27 children, who experienced recurrences during a 1-year follow-up after the first attack of acute pyelonephritis, were investigated. The MICs of sulfamethoxazole, trimethoprim-sulfamethoxazole (SXT), ampicillin, cefuroxime, cefotaxime, and gentamicin and the presence or absence of the intI gene for class 1 integrons and the sulfamethoxazole resistance-encoding genes sul1, sul2, and sul3 were determined. All E. coli strains were genotyped by pulsed-field gel electrophoresis. There were no significant differences in the prevalences of resistance to beta-lactams and SXT between initial and consecutive E. coli isolates (41 versus 45% and 41 versus 29%, respectively). However, the E. coli strains obtained after SXT administration more frequently carried two or more sul genes than the nonexposed strains (9/21 [43%] versus 11/57 [19%], respectively; P = 0.044). In 78% of the patients, the recurrence of unique clonal E. coli strains alone or combined with individual strains was detected. Phenotypic resistance and the occurrence of sul genes were more stable in clonal strains than in individual strains (odds ratios, 8.7 [95% confidence interval {95% CI}, 1.8 to 40.8] and 4.4 [95% CI, 1.1 to 17.7], respectively). Thus, in children with RUTIs, the majority of E. coli strains from consecutive episodes are unique persisting clones, with rare increases in the initially high antimicrobial resistance, the presence of sul genes, and the presence of integrons.

Pulsed-field gel electrophoresis typing of Escherichia coli strains from samples collected before and after pivmecillinam or placebo treatment of uncomplicated community-acquired urinary tract infection in women

The primary infecting Escherichia coli strains from 156 women with community-acquired uncomplicated urinary tract infection (UTI) randomized to pivmecillinam or placebo and the E. coli strains causing UTI at two follow-up visits were typed using pulsed-field gel electrophoresis (PFGE). In the pivmecillinam treatment group PFGE showed that among patients having a negative urine culture at the first follow-up 77% (46/60) had a relapse with the primary infecting E. coli strain and 23% (14/60) had reinfection with a new E. coli strain at the second follow-up. Among patients having E. coli at the first follow-up PFGE showed that 80% (32/40) had persistence with the primary infecting E. coli strain, 15% (6/40) had reinfection with a new E. coli strain, and 5% (2/40) had different E. coli strains at the two follow-up visits (one had reinfection followed by relapse, and the other had persistence followed by reinfection). In the placebo group the majority had E. coli at the first follow-up. PFGE showed that among these patients 96% (50/52) had persistence with the primary infecting E. coli strain and 4% (2/50) had different E. coli strains at the two follow-up visits (both had persistence followed by reinfection). The finding that the majority of UTIs at follow-up are caused by the primary infecting E. coli strain supports the theory of a vaginal and rectal reservoir but could also support the recent discovery that E. coli strains are able to persist in the bladder epithelium despite appropriate antibiotic treatment, constituting a reservoir for recurrent UTI.

Actin-gated intracellular growth and resurgence of uropathogenic Escherichia coli

Strains of uropathogenic Escherichia coli (UPEC) can invade terminally differentiated superficial bladder epithelial cells and subsequently multiply, forming large biofilm-like inclusions referred to as pods. In contrast, within immature bladder cells UPEC enter a more quiescent state and often fail to replicate appreciably. As immature bladder epithelial cells undergo terminal differentiation the actin cytoskeleton is radically diminished, a phenomenon that we reasoned could influence the intracellular fate of UPEC. Here we show that UPEC within undifferentiated bladder cells is trafficked into acidic compartments having key features of late endosomes and lysosomes. These UPEC-containing vacuoles are often enmeshed within a network of actin filaments, the disruption of which stimulates intravacuolar growth and efflux of UPEC in cell culture-based studies. In this in vitro model system, release of UPEC into the host cytosol further stimulates intracellular bacterial growth and the rapid development of pod-like inclusions. These inclusions, as well as those observed using an in vivo mouse model, develop in association with cytokeratin intermediate filaments that may act as scaffolding for intracellular biofilm formation. Our data suggest an aetiological basis for recurrent urinary tract infections, linking bladder cell differentiation and the accompanying redistribution of actin microfilaments with the resurgence of UPEC from quiescent intravacuolar reservoirs within the bladder epithelium.

[Recurrent urinary tract infections in women. Virulence of pathogens and host reaction]

The interactions of host-specific and microbial factors are responsible for recurrent urinary tract infections (rUTI). The anatomical properties of the female urogenital tract favor colonization by uropathogens. Local factors such as glucose concentration of the urine, stability of the lactobacilli population, the influence of estrogens, the activity of Tamm-Horsfall protein or of defensins, and disturbance of the systemic defense mechanisms dictate the course of an infection. The most prominent uropathogen is E. coli. It expresses various virulence factors including adhesions, toxins, iron uptake systems, and a capsule. It is still unclear if there are virulence factors characteristic for E. coli strains causing rUTI. The formation of intracellular reservoirs by invasion of uroepithelial cells by E. coli could be another, as yet little noticed cause for rUTI. Therefore, in cases of rUTI the application of intracellularly active antibiotics should be considered.

Molecular epidemiology of extraintestinal pathogenic (uropathogenic) Escherichia coli

Molecular epidemiological analyses of extraintestinal pathogenic Escherichia coli (ExPEC), which are also called "uropathogenic E. coli" since they are the principle pathogens in urinary tract infection, involve structured observations of E. coli as they occur in the wild. Careful selection of subjects and use of appropriate methods for genotyping and statistical analysis are required for optimal results. Molecular epidemiological studies have helped to clarify the host-pathogen relationships, phylogenetic background, reservoirs, and transmission pathways of ExPEC, to assess potential vaccine candidates, and to delineate areas for further study. Ongoing discovery of new putative virulence factors (VFs), increasing awareness of the importance of VF expression and molecular variants of VFs, and growing appreciation of transmission as an important contributor to ExPEC infections provide abundant stimulus for future molecular epidemiological studies. Published by Elsevier GmbH.

Covert operations of uropathogenic Escherichia coli within the urinary tract

Entry into host cells is required for many bacterial pathogens to effectively disseminate within a host, avoid immune detection and cause disease. In recent years, many ostensibly extracellular bacteria have been shown to act as opportunistic intracellular pathogens. Among these are strains of uropathogenic Escherichia coli (UPEC), the primary causative agents of urinary tract infections (UTIs). UPEC are able to transiently invade, survive and multiply within the host cells and tissues constituting the urinary tract. Invasion of host cells by UPEC is promoted independently by distinct virulence factors, including cytotoxic necrotizing factor, Afa/Dr adhesins, and type 1 pili. Here we review the diverse mechanisms and consequences of host cell invasion by UPEC, focusing also on the impact of these processes on the persistence and recurrence of UTIs.

The role of indirect radionuclide cystography during the acute phase of pyelonephritis in young women

OBJECTIVE

To review our experience using dynamic 99mTc-diethylenetriamine penta-acetic acid renal scintigraphy combined with indirect radionuclide cystography (IRC) in the acute phase of pyelonephritis, as a possible alternative to the conventional imaging, as investigating acute pyelonephritis usually includes imaging the upper urinary tract during the acute phase, to exclude obstruction, and delayed voiding cysto-urethrography (VCUG) when underlying vesico-ureteric reflux (VUR) is suspected.

PATIENTS AND METHODS

Between 1997 and 1999, 47 young women (median age 22 years, range 18-37) were hospitalized for acute pyelonephritis. The combined study was used during the acute phase of the disease, usually within 24 h of hospitalization. The principle of IRC is based on the reappearance of radioactivity in the ureters or kidneys after previously detecting renal clearance of an intravenously injected radioisotope. The increase in radioactivity over the ureters or kidneys indicates VUR. The subsequent follow-up included VCUG, after recovery and at least 6 weeks after discharge.

RESULTS

Overall, 47 patients had early IRC studies; obstruction of the urinary tract during the acute phase of the disease was excluded in all. In 13 (28%) of the patients early IRC studies showed VUR involving 21 upper tract units. The renal parenchymal scan was impaired in 17 (36%) patients, and six of these 17 also had detectable concomitant reflux on IRC. Overall, 24 IRC studies (51%) were considered positive, showing VUR, renal parenchymal pathology or both; 23 (49%) were normal. Follow-up VCUG was used in 32 patients (68%); only three (9%) detected VUR. All of the patients with VUR on follow-up VCUG had also had an abnormal early IRC study, showing either reflux (two) or findings suggestive of pathological renal parenchyma (one).

CONCLUSIONS

In addition to the well-established role of renal scintigraphy in excluding obstruction of the collecting system, early IRC is characterized by high sensitivity and accurate negative predictive value for detecting VUR. It can therefore be used to screen adults presenting with acute pyelonephritis for the presence of VUR. Patients with an abnormal IRC require follow-up VCUG after complete recovery, while those with a negative study may be managed expectantly, with no further radiological evaluation. This proposed strategy may avoid up to half of the delayed VCUG studies, preclude the related inconvenience, and substantially reduce the costs.

Acute pyelonephritis among adults: cost of illness and considerations for the economic evaluation of therapy

Urinary tract infection (UTI) is an infection anywhere in the urinary tract, most commonly due to bacteria. If infection involves the kidney, the UTI is termed acute pyelonephritis (APN). An estimated 10-30% of all patients with APN are hospitalised for treatment; in the US, the incidence of hospitalisation is 11.7 per 10,000 for women and 2.4 per 10,000 for men. Perhaps because of the generally good prognosis of APN when treated with current antibacterial therapies, there have been relatively few studies of patient management and therapeutic options for the disease, or of its epidemiology and risk factors. The most cost-effective outpatient management strategy (immediate discharge, observation followed by discharge, etc.) is currently unknown. Appropriate antimicrobial selection is clearly important, as treatment failures will increase the cost of care and result in additional morbidity for patients. The direct and indirect costs of APN are significant: an estimated 2.14 billion US dollars (year 2000 values). Cost estimates are most sensitive to hospitalisation rates, which are unknown in the US. Additional studies are needed to better define when in-hospital treatment is required. As the pathogens causing APN are increasingly becoming resistant to current therapies, not only are clinical trials in order to test the effectiveness of alternative therapies, but epidemiological studies to identify risk factors for infection with a resistant isolate and effective prevention strategies are required, especially among those with previous episodes of APN.

Viable but nonculturable bacteria are present in mouse and human urine specimens

The presence of viable but nonculturable bacteria in human clean-catch and mouse bladder-isolated urine specimens was investigated. Viable but nonculturable bacteria are alive but do not give rise to visible growth under nonselective growth conditions. Urine specimens obtained from human female volunteers with or without an active urinary tract infection were found to contain, on average, significantly more viable than culturable forms of bacteria. Additional support for the presence of viable but nonculturable cells in urine specimens considered sterile was obtained from examination of urine specimens obtained directly from the bladder of healthy mice. Because the viability assay used to study the viable but nonculturable condition is by necessity growth independent, and hence indirect, the accuracy of this assay that scores cells with intact cell membranes as being viable was studied. Greater than 95% of Escherichia coli cells exposed to lethal doses of UV irradiation were found to lose their membrane integrity within a day, a time frame similar to that used to examine urine specimens. These data suggest that viable but nonculturable cells can occur within regions of the urinary tract previously considered sterile.

Urinary tract infections

Urinary tract infections (UTIs) are a common infectious disease in primary care practice. This article reviews topics highlighting recent research, including UTIs in pregnancy and pediatric UTIs. The authors also discuss catheter-associated UTIs, given the large number of hospitalized patients undergoing catheterization and residents of long-term care facilities, in whom catheters are used frequently, and complicated UTIs.

Effect of trimethoprim-sulfamethoxazole on recurrent bacteriuria and bacterial persistence in mice infected with uropathogenic Escherichia coli

One of the more perplexing aspects of urinary tract infections (UTIs) is their high propensity to recur. It has been proposed that recurrent infections are a result of the reintroduction of bacteria from the gastrointestinal tract (GIT) to the urinary tract (UT); however, since a significant subset of recurrent UTIs are caused by an identical bacterial strain, it has been challenging to formally prove this hypothesis for same-strain recurrences by using epidemiologic approaches. We present data here obtained by using a mouse model of UTIs in which it was shown that 36% (5 of 14) of mice infected with uropathogenic Escherichia coli (UPEC) will have at least one bacteriuric recurrence, with 21% (3 of 14) having more than one recurrence during a 6-week period after an acute UTI. Intraurethrally infected mice develop UPEC reservoirs in both their feces and their bladders. Ten days of trimethoprim-sulfamethoxazole (SXT) therapy reduces urinary recurrences and eradicates fecal colonization, whereas 3 days of SXT treatment has no effect over a twenty-eight-day observation period despite clearing fecal colonization acutely. Interestingly, SXT is unable to eradicate bacteria from the bladder reservoir even after a 10-day treatment regimen, thus demonstrating that the bladder reservoir can persist even in the face of long-term antibiotic therapy.

Recent advances into the pathogenesis of recurrent urinary tract infections: the bladder as a reservoir for uropathogenic Escherichia coli

Recurrent cystitis is a common clinical entity that is becoming increasingly challenging to manage. The current thought regarding the pathogenesis of these infections is evolving as new data emerges to suggest that some recurrences may originate from previously unrecognized reservoirs of uropathogenic Escherichia coli. This article will summarize recent conceptual changes with respect to the aetiology of recurrent urinary tract infections, particularly as it relates to chronic bacterial persistence in the bladder.

Urinary tract infection in geriatric and institutionalized patients

The importance of urinary tract infection in elderly populations and some of the unique features in its evaluation and therapy are becoming better recognized. In elderly populations in the community there are concerns about increasing antimicrobial resistance in infecting organisms. In postmenopausal women, the importance of vaginal estrogen deficiency as a factor which promotes urinary tract infection is becoming increasingly recognized, leading to therapeutic strategies other than antimicrobials. For elderly residents of long term care facilities, urinary tract infection is very common, and most frequent in those with the greatest functional impairment. Whilst it is recognized that asymptomatic bacteriuria should not be treated, the diagnosis of urinary tract infection in this population often presents a dilemma. In particular, the urine culture is useful only in excluding urinary tract infection, not in making a diagnosis of symptomatic infection. There has been a tendency to manage all clinical deterioration in long term care facility residents who have positive urine cultures as urinary tract infection, contributing to excess antimicrobial use and heightening the problem of antimicrobial resistance. Recently published guidelines and commentaries attempt to address this problem.