Predominance of class II papG allele of Escherichia coli in pyelonephritis in infants with normal urinary tract anatomy

Transcriptomic analysis reveals that the small protein MgtS contributes to the virulence of uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is the most common pathogen causing urinary tract infections (UTIs). The pathogenesis of UPEC relies on the formation of intracellular bacterial communities (IBCs) after invading bladder epithelial cells (BECs). In this study, the gene expression profiles of UPEC after invading BECs were comprehensively analyzed using RNA sequencing to reveal potential virulence-related genes. The small protein MgtS, which is transcriptionally upregulated in BECs, was further investigated. It was found that MgtS contributed positively to UPEC invasion of BECs and colonization in murine bladders. A two-component regulatory system, PhoPQ was confirmed as a direct activator of mgtS expression in BECs, and magnesium limitation is proposed as a host cue for the activation. This study provides the first comprehensive analysis of the transcriptome profile of UPEC during its intra-BECs life, revealing a new virulence-associated gene and its regulatory mechanism.

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.

PerC Manipulates Metabolism and Surface Antigens in Enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli is an important cause of profuse, watery diarrhea in infants living in developing regions of the world. Typical strains of EPEC (tEPEC) possess a virulence plasmid, while related clinical isolates that lack the pEAF plasmid are termed atypical EPEC (aEPEC). tEPEC and aEPEC tend to cause acute vs. more chronic type infections, respectively. The pEAF plasmid encodes an attachment factor as well as a regulatory operon, perABC. PerC, a poorly understood regulator, was previously shown to regulate expression of the type III secretion system through Ler. Here we elucidate the regulon of PerC using RNA sequencing analysis to better our understanding of the role of the pEAF in tEPEC infection. We demonstrate that PerC controls anaerobic metabolism by increasing expression of genes necessary for nitrate reduction. A tEPEC strain overexpressing PerC exhibited a growth advantage compared to a strain lacking this regulator, when grown anaerobically in the presence of nitrate, conditions mimicking the human intestine. We show that PerC strongly down-regulates type I fimbriae expression by manipulating fim phase variation. The quantities of a number of non-coding RNA molecules were altered by PerC. In sum, this protein controls niche adaptation, and could help to explain the function of the PerC homologs (Pch), many of which are encoded within prophages in related, Gram-negative pathogens.

Multidrug- and Extensively Drug-Resistant Uropathogenic Escherichia coli Clinical Strains: Phylogenetic Groups Widely Associated with Integrons Maintain High Genetic Diversity

In recent years, an increase of uropathogenic Escherichia coli (UPEC) strains with Multidrug-resistant (MDR) and Extensively Drug-resistant (XDR) profiles that complicate therapy for urinary tract infections (UTIs) has been observed and has directly impacted costs and extended hospital stays. The aim of this study was to determine MDR- and XDR-UPEC clinical strains, their virulence genes, their phylogenetic groups and to ascertain their relationship with integrons and genetic diversity. From a collection of 500 UPEC strains, 103 were selected with MDR and XDR characteristics. MDR-UPEC strains were mainly associated with phylogenetic groups D (54.87%) and B2 (39.02%) with a high percentage (≥70%) of several fimbrial genes (ecpA, fimH, csgA, and papGII), an iron uptake gene (chuA), and a toxin gene (hlyA). In addition, a moderate frequency (40–70%) of other genes (iutD, tosA, and bcsA) was observed. XDR-UPEC strains were predominantly associated with phylogenetic groups B2 (47.61%) and D (42.85%), which grouped with ≥80 virulence genes, including ecpA, fimH, csgA, papGII, iutD, and chuA. A moderate frequency (40–70%) of the tosA and hlyA genes was observed. The class 1 and 2 integrons that were identified in the MDR- and XDR-UPEC strains were associated with phylogenetic groups D, B2, and A, while the XDR-UPEC strains that were associated with phylogenetic groups B2, D, and A showed an extended-spectrum beta-lactamase (ESBL) phenotype. The modifying enzymes (aadA1, aadB, aacC, ant1, dfrA1, dfrA17, and aadA4) that were identified in the variable region of class 1 and 2 integrons from the MDR strains showed resistance to gentamycin (56.25 and 66.66%, respectively) and trimethoprim-sulfamethoxazole (84.61 and 66.66%, respectively). The MDR- and XDR-UPEC strains were distributed into seven clusters and were closely related to phylogenic groups B2 and D. The diversity analysis by PFGE showed 42.68% of clones of MDR-UPEC and no clonal association in the XDR-UPEC strains. In conclusion, phylogenetic groups including virulence genes are widely associated with two integron classes (1 and 2) in MDR- and XDR-UPEC strains.

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.

Escherichia coli virulence patterns may help to predict vesicoureteral reflux in paediatric urinary tract infections

AIM

Ultrasound and biological tools are used to predict high-grade vesicoureteral reflux, but other markers are needed to better select patients who need voiding cystography. Our aim was to determine whether studying Escherichia coli virulence factors would help to predict vesicoureteral reflux in patients with their first acute pyelonephritis.

METHODS

We included children presenting with E. coli-related acute pyelonephritis or cystitis. Vesicoureteral reflux was assessed by voiding cystography. Virulence factors were identified by multiplex polymerase chain reaction. Statistical analysis was performed using logistic regression and the mean c-statistic test.

RESULTS

We included 198 patients: 30 with cystitis and 168 with acute pyelonephritis, including 46 with vesicoureteral reflux. High-grade reflux was associated with acute pyelonephritis caused by the E. coli lacking virulence factors papGII (82% versus 47%, p < 0.001) or papC (85% versus 53%, p < 0.001) or belonging to phylogenetic group A or B1. When we added genetic data (lack of papGII, fyuA and phylogenetic groups) to classical predictors of vesicoureteral reflux (ultrasound examination, gender, age), the ability to predict high-grade reflux increased, with the c-statistic rising from 0.88 to 0.93.

CONCLUSION

Bacterial virulence factors and clinical factors helped to predict high-grade reflux and may help to avoid unnecessary voiding cystographies.

[Virulence factors and pathophysiology of extraintestinal pathogenic Escherichia coli]

Extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections, bacteraemia or meningitis are characterized by a particular genetic background (phylogenetic group B2 and D) and the presence, within genetic pathogenicity islands (PAI) or plasmids, of genes encoding virulence factors involved in adhesion to epithelia, crossing of the body barriers (digestive, kidney, bloodbrain), iron uptake and resistance to the immune system. Among the many virulence factors described, two are particularly linked with a pathophysiological process: type P pili PapGII adhesin is linked with acute pyelonephritis, in the absence of abnormal flow of urine, and the K1 capsule is linked with neonatal meningitis. However, if the adhesin PapGII appears as the key factor of pyelonephritis, such that its absence in strain causing the infection is predictive of malformation or a vesico-ureteral reflux, the meningeal virulence of E. coli can not be reduced to a single virulence factor, but results from a combination of factors unique to each clone, and an imbalance between the immune defenses of the host and bacterial virulence.

Genetic polymorphisms and susceptibility to parenchymal renal infection among pediatric patients

BACKGROUND

Patient susceptibility to bacterial urinary tract infections, which is determined by complex pathogen-host interactions, varies between individuals due to genetic variation. The neutrophil-dependent innate immune system is an important part of keeping the urinary tract sterile. This study was performed to explore single nucleotide polymorphisms (SNPs) in genes associated with neutrophil-dependent immunity in pediatric patients with severe parenchymal infections.

METHODS

The subjects included patients who fulfilled the diagnostic criteria of acute pyelonephritis (APN) and acute lobar nephronia (ALN) without underlying disease or structural anomalies (excluding vesicoureteral reflux). Genotyping of the genes encoding toll-like receptor 4 (TLR-4), interleukin-8 (IL-8), and IL-8 receptors CXCR1 and CXCR2 was performed by matrix-assisted laser desorption/ionization time-of-flight-based mini-sequencing analysis.

RESULTS

A total of 17 SNPs, including missense SNPs and those located in promoter regions, were initially selected for genotyping. Only 4 SNPs with a heterozygosity rate >0.01 were evaluated further. The observed genotype frequencies satisfied Hardy-Weinberg equilibrium. Statistical analysis revealed that only IL-8 (rs4073, -251A>T) showed significant differences in genotype and allele frequency between the control and APN or ALN cases. Following the elimination of vesicoureteral reflux, which is a significant risk factor for severe parenchymal infection, a single SNP in IL-8 (rs4073) was found to be associated with clinically severe ALN.

CONCLUSIONS

The AA genotype and A allele of the IL-8 SNP is related to patient susceptibility to parenchymal infection and is correlated with the severity of infection in pediatric APN and ALN patients, probably due to the upregulation of IL-8 expression.

Comparison of extended virulence genotypes for bacteria isolated from pediatric patients with urosepsis, acute pyelonephritis, and acute lobar nephronia

BACKGROUND

Despite recent advances in molecular epidemiology and pathogenecity analyses of extraintestinal Escherichia coli infections, detailed analyses identifying virulence factors of E. coli isolates from pediatric urosepsis patients have not been reported. This study was conducted to explore and differentiate bacterial virulence factors associated with urosepsis and 2 other severe parenchymal infections, acute pyelonephritis (APN) and acute lobar nephronia (ALN), in pediatric patients.

METHODS

Patients included in this study were those who fulfilled the diagnostic criteria of urosepsis, APN, and ALN, without underlying disease or structural anomalies, excluding those with vesicoureteral reflux. Patients with cystitis were included as controls. E. coli isolates from urine (cystitis, APN, and ALN) or blood (urosepsis) specimens were analyzed using polymerase chain reaction (PCR) for 25 virulence genes.

RESULTS

A total of 147 children (24 cystitis, 45 APN, 48 ALN, and 30 urosepsis) were enrolled in the study. Distinct syndrome-specific differences in the distribution for certain virulence genes, but conservation across syndromes for others, were found. In addition, urosepsis isolates presented higher aggregate virulence factor scores (P < 0.0001) compared with cystitis, APN, and ALN isolates. By contrast, cystitis isolates showed significantly lower aggregate virulence factor scores than all 3 invasive urinary bacterial infections; APN (P < 0.01), ALN (P < 0.01), and urosepsis (P < 0.0001).

CONCLUSIONS

Our findings suggested that urosepsis isolates carry more virulence factors and are likely more urovirulent compared with cystitis, APN, and ALN isolates.

Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

Phylogenetic groups and virulence factors of Escherichia coli strains causing pyelonephritis in children with and without urinary tract abnormalities

Escherichia coli isolates causing acute pyelonephritis in 93 children (25% with urinary tract abnormalities) were tested for nine virulence factors (papC, papGII, papGIII, sfa/foc, hlyC, cnf1, iucC, fyuA and iroN) and their phylogenetic groups were determined. Isolates lacking papGII were more frequent among patients with urinary tract abnormalities (58% vs. 10%, p 0.0003), as were non-virulent phylogenetic group A isolates (25% vs. 5%, p 0.043). Pyelonephritis caused by less virulent E. coli strains was more frequent among patients with significant urinary tract abnormalities. Further studies are required to determine whether screening for E. coli virulence factors may help to identify children warranting anatomical investigations.

Comparison of urovirulence factors and genotypes for bacteria causing acute lobar nephronia and acute pyelonephritis

BACKGROUND

Acute lobar nephronia (ALN) is a severe renal parenchymal inflammatory disease that has been diagnosed with increasing frequency as a result of newer noninvasive diagnostic modalities. Escherichia coli is the most common bacterial pathogen isolated from the urine samples of ALN patients. This prospective study was conducted to elucidate and distinguish the bacterial virulence factors associated with ALN and acute pyelonephritis (APN) in pediatric patients.

METHODS

Patients included in the present study were those suspected of an upper urinary tract infection who underwent ultrasonographic, computed tomographic and technetium 99m-dimercaptosuccinic acid scintigraphic evaluation to distinguish between ALN and APN. The E. coli isolates from the urine samples of patients were screened with polymerase chain reaction analysis for various urovirulence genes. Pulsed-field gel electrophoresis was used to analyze the genetic association of the isolates.

RESULTS

A total of 88 patients were enrolled. Forty-six patients were diagnosed with ALN and 42 with APN. Demographic characteristics and clinical results were similar except for longer fever duration before admission, longer fever continuation following antibiotic treatment and higher C-reactive protein values noted in the ALN group. Diverse genotypes were found among the E. coli isolates in both groups. Among the pathogenetic determinants examined, multivariate logistic regression analysis indicated that a papG II allele was the only significant urovirulence factor associated with ALN (P < 0.005; odds ratio, 17.16). This association was independent of the presence of VUR.

CONCLUSIONS

While no specific genetic lineage was identified among the E. coli isolates studied, a papG II gene was found to be strongly associated with the cause of ALN among pediatric patients.

Vesicoureteral reflux increases the risk of renal scars: a study of unilateral reflux

The aim of this study was to assess the impact of vesicoureteral reflux (VUR) on renal scar following acute pyelonephritis by comparing the refluxing renal units with nonrefluxing renal units in children with unilateral primary VUR. Forty-eight children with unilateral primary VUR diagnosed after the first pyelonephritis were enrolled. Mean age of patients was 1.0+/-1.6 years (29 boys and 19 girls). All patients underwent renal ultrasonography and renal 99 m-technetium dimercaptosuccinic acid (DMSA) scan within three days following the diagnosis of pyelonephritis, and voiding cystourethrography (VCU) was performed soon after fever subsided and the infection was controlled. The DMSA scan was rechecked six months after the initial study when the first scan showed a renal defect. The first DMSA showed renal defects in 34 (70.8%) out of 48 of the refluxing renal units and in 13 (27.1%) out of 48 of the nonrefluxing renal units (P<0.01, OR: 6.54). At six months after the infection, 23 (47.9%) out of 48 refluxing renal units and seven (14.6%) out of 48 nonrefluxing renal units had renal scars on DMSA scan (P<0.01, OR: 5.39). The prevalence of renal scars did not vary significantly according to the grade of VUR. The CRP level on admission was significantly higher in patients with acute renal defect and scar. In conclusion, VUR increases the risk of post-pyelonephritic renal scars in children.

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.

Post-pyelonephritic renal scars are not associated with vesicoureteral reflux in children

PURPOSE

Children with pyelonephritis are at risk for renal damage. We assess the value of clinical signs and urological abnormalities in predicting renal scars in children following pyelonephritis.

MATERIALS AND METHODS

A total of 64 hospitalized children (29 females and 35 males, median age 2.9 years) underwent ultrasonography and technetium labeled dimercapto-succinic acid (DMSA) scintigraphy imaging within 1 week following the diagnosis of the first pyelonephritis. Voiding cystourethrography was performed 8 weeks after the diagnosis. Followup DMSA scintigraphy was performed in 58 patients after 2 years of followup.

RESULTS

Urological abnormalities observed were vesicoureteral reflux (VUR, grade 2 or higher) in 11 patients (19%), nonrefluxing and nonobstructed megaureter in 2 (4%) and pyeloureteral obstruction in 1 (2%). The first DMSA scintigraphy showed parenchymal defects in 48% of patients. VUR did not increase the risk of renal defects. At 2 years after the infection 12 of the 58 patients (21%) had renal scars. Nine of these patients did not have VUR. However, 2 patients with high grade VUR and repeat infections demonstrated deterioration of kidney function during followup. The patients with renal scars were older than those without scars (3.1 vs 0.8 years, p = 0.0291) at the time of infection.

CONCLUSIONS

Renal scars after first pyelonephritis are in most cases not associated with abnormalities of the urinary tract, but are caused by the infection itself. However, structural abnormalities may predispose to recurrent infections. Following pyelonephritis new renal scars may develop in all age groups in both sexes.

Predominance of the papGII allele with high sequence homology to that of human isolates among avian pathogenic Escherichia coli (APEC)

Avian pathogenic Escherichia coli (APEC) are often found in poultry and are responsible for a set of diseases, commonly referred to as avian colibacillosis. One of the important virulence factors is adhesion to different epithelial surfaces, which is mediated by pili. P pili are thought to play a role by means of their PapG adhesin, which occurs in three molecular variants: PapGI, PapGII and PapGIII. This study is the first to determine and analyse the distribution of the different papG alleles in APEC. Our results show a significant predominance of the papGII allele above all other alleles or allele combinations. No statistically significant associations could be found between papG allele distribution and the type of bird, organ of isolation and O serogroup. Finally, the papGII and papGIII sequences showed high homology with mammalian (including human) source papG sequences.

Differences in virulence factors among clinical isolates of Escherichia coli causing cystitis and pyelonephritis in women and prostatitis in men

Differences in the presence of nine urovirulence factors among clinical isolates of Escherichia coli causing cystitis and pyelonephritis in women and prostatitis in men have been studied. Hemolysin and necrotizing factor type 1 occur significantly more frequently among isolates causing prostatitis than among those causing cystitis (P < 0.0001) or pyelonephritis (P < 0.005). Moreover, the papGIII gene occurred more frequently in E. coli isolates associated with prostatitis (27%) than in those associated with pyelonephritis (9%) (P < 0.05). Genes encoding aerobactin and PapC occurred significantly less frequently in isolates causing cystitis than in those causing prostatitis (P < 0.01 and P < 0.0001, respectively) and pyelonephritis (P < 0.01 and P < 0.0001, respectively). No differences in the presence of Sat or type 1 fimbriae were found. Finally, AAFII and Bfp fimbriae are no longer considered uropathogenic virulence factors since they were not found in any of the strains analyzed. Overall, the results showed that clinical isolates producing prostatitis need greater virulence than isolates producing pyelonephritis in women or, in particular, cystitis in women (P < 0.05). Overall, the results suggest that clinical isolates producing prostatitis are more virulent that those producing pyelonephritis or cystitis in women.

Adhesion and entry of uropathogenic Escherichia coli

To effectively colonize a host animal and cause disease, many bacterial pathogens have evolved the mechanisms needed to invade and persist within host cells and tissues. Recently it was discovered that uropathogenic Escherichia coli, the primary causative agent of urinary tract infections, can invade and replicate within uroepithelial cells. This can provide E. coli with a survival advantage, allowing the microbes to better resist detection and clearance by both innate and adaptive immune defence mechanisms. Adhesive organelles, including type 1, P, and S pili along with Dr adhesins, promote both bacterial attachment to and invasion of host tissues within the urinary tract. Interactions mediated by these adhesins can also stimulate a number of host responses that can directly influence the outcome of a urinary tract infection.

pap genotype and P fimbrial expression in Escherichia coli causing bacteremic and nonbacteremic febrile urinary tract infection

Escherichia coli strains from patients with febrile urinary tract infections (n=73) were examined for pap genotype and P fimbrial expression in relation to bacteremia and patients' background variables. Most isolates were pap(+) by DNA hybridization (n=51), and 36 were papG(IA2)(+) and 18 prsG(J96)(+) by polymerase chain reaction. The pap and papG genotypes of the infecting strain were shown to vary with host compromise, sex, and age. Bacteremia in noncompromised patients was caused by papG(IA2)(+) strains, but compromised hosts carried a mixture of papG(IA2)(+), prsG(J96)(+), and pap(-) strains. Women of all ages were infected with papG(IA2)(+) strains. Infected men carried prsG(J96)(+) or pap(-) strains and were older, and most had compromising conditions. papG(IA2)(+) strains predominated among patients with medical illness, whereas prsG(J96)(+) strains predominated among patients with urinary tract abnormalities. These findings emphasize the strong influence of host factors on the selection of E. coli strains causing febrile urinary tract infections.

Predictive factors associated with significant urinary tract abnormalities in infants with pyelonephritis

BACKGROUND

Major urinary tract abnormalities are detected in 20 to 40% of infants with acute pyelonephritis (APN). Early detection of structural defects is essential for protecting the kidneys from reinfection and subsequent scarring. The purpose of this study was to investigate whether any factors present during the acute phase of infection could predict the presence of existing significant urinary tract abnormalities in infants.

METHODS

A prospective study of 180 infants, aged 1 to 24 months, with APN was conducted. Blood and urine samples were collected. Renal ultrasound (US) was performed within 0 to 6 days from admission. Final diagnosis of the urinary tract anatomy was elucidated using the results of two or more radiologic imaging studies.

RESULTS

Risk factors for the presence of significant urinary tract abnormalities in infants were pathogens other than Escherichia coli in urine [relative risk (RR) 3.4, 95% confidence interval (CI) 2.2 to 5.3; P = 0.001], positive blood culture (RR 2.3, 95% CI 1.3 to 4.0; P = 0.039), young age (1 to 6 months) (RR 2.2, 95% CI 1.3 to 3.9; P = 0.004), lack of papG adhesin genes of E. coli in urine (RR 2.1, 95% CI 1.2 to 3.9; P = 0.016) and abnormal renal US (RR 2.0, 95% CI 1.2 to 3.4; P = 0.008).

CONCLUSIONS

Infants 1 to 6 months of age with APN caused by bacteria other than E. coli or by papG-negative E. coli strain, positive blood culture and abnormal renal US carry an increased risk for significant urinary tract abnormalities and need enforced follow-up.

Urinary tract infection: new perspectives on a common disease

Urinary tract infection is an important cause of morbidity in children, and affects up to 10% of the childhood population. Recent information suggests that the long-term outcome for children with urinary tract infection is much better than previously believed, with causal links to end-stage renal disease and hypertension not demonstrated despite 20-year cohort studies. Improvements in the use of dipstick and clinical features as diagnostic tools have occurred, but culture is still needed if the diagnosis of urinary tract infection is to be definitively established. Interventions to prevent recurrent urinary tract infection, particularly low-dose, long-term antimicrobial agents may not be effective and placebo-controlled trials are now required.

Novel molecular variants of allele I of the Escherichia coli P fimbrial adhesin gene papG

P fimbriae of extraintestinal pathogenic Escherichia coli mediate digalactoside-specific adherence via the tip adhesin molecule PapG, which occurs in three known variants (I to III), which are encoded by the corresponding three alleles of papG. In the present study, newly discovered variants of papG allele I and the respective wild-type source strains were characterized. One of the new papG allele I variants conferred a unique agglutination phenotype that combined the phenotypes associated with papG alleles I, II, and III. Comparative hydrophilicity analysis of predicted PapG peptides revealed regions that might explain the observed phenotypic similarities and differences between the PapG variants. The new papG allele I variants occurred either as the sole papG allele or together with both papG alleles II and III, rather than with only papG allele III, as in archetypal strains J96 and CP9. They also occurred in the absence of the usual F13 papA allele. One of the new papG allele I variants occurred in a serogroup O6 strain that, according to random amplified polymorphic DNA analysis, was phylogenetically distant from the "J96-like" clonal group of E. coli O4:H5, which includes all previously identified examples of papG allele I. Cluster analysis of nucleotide and predicted peptide sequences suggested that papG allele I represents the earliest evolutionary branch from a common papG ancestor. These results demonstrate unexpected diversity within papG allele I and, together with previous findings, suggest that the J96-like clonal group of E. coli O4:H5 may represent the original source of papG within the species.

Canine feces as a reservoir of extraintestinal pathogenic Escherichia coli

To test the canine reservoir hypothesis of extraintestinal pathogenic Escherichia coli (ExPEC), 63 environmental canine fecal deposits were evaluated for the presence of ExPEC by a combination of selective culturing, extended virulence genotyping, hemagglutination testing, O serotyping, and PCR-based phylotyping. Overall, 30% of canine fecal samples (56% of those that yielded viable E. coli) contained papG-positive E. coli, usually as the predominant E. coli strain and always possessing papG allele III (which encodes variant III of the P-fimbrial adhesin molecule PapG). Multiple other virulence-associated genes typical of human ExPEC were prevalent among the canine fecal isolates. According to serotyping, virulence genotyping, and random amplified polymorphic DNA analysis, over 50% of papG-positive fecal E. coli could be directly correlated with specific human clinical isolates from patients with cystitis, pyelonephritis, bacteremia, or meningitis, including archetypal human ExPEC strains 536, CP9, and RS218. Five canine fecal isolates and (clonally related) archetypal human pyelonephritis isolate 536 were found to share a novel allele of papA (which encodes the P-fimbrial structural subunit PapA). These data confirm that ExPEC representing known virulent clones are highly prevalent in canine feces, which consequently may provide a reservoir of ExPEC for acquisition by humans.