Untreated asymptomatic bacteriuria in girls: I--Stability of urinary isolates

Evidence-based clinical practice guideline for management of urinary tract infection and primary vesicoureteric reflux

We present updated, evidence-based clinical practice guidelines from the Indian Society of Pediatric Nephrology (ISPN) for the management of urinary tract infection (UTI) and primary vesicoureteric reflux (VUR) in children. These guidelines conform to international standards; Institute of Medicine and AGREE checklists were used to ensure transparency, rigor, and thoroughness in the guideline development. In view of the robust methodology, these guidelines are applicable globally for the management of UTI and VUR. Seventeen recommendations and 18 clinical practice points have been formulated. Some of the key recommendations and practice points are as follows. Urine culture with > 104 colony forming units/mL is considered significant for the diagnosis of UTI in an infant if the clinical suspicion is strong. Urine leukocyte esterase and nitrite can be used as an alternative screening test to urine microscopy in a child with suspected UTI. Acute pyelonephritis can be treated with oral antibiotics in a non-toxic infant for 7-10 days. An acute-phase DMSA scan is not recommended in the evaluation of UTI. Micturating cystourethrography (MCU) is indicated in children with recurrent UTI, abnormal kidney ultrasound, and in patients below 2 years of age with non-E. coli UTI. Dimercaptosuccinic acid scan (DMSA scan) is indicated only in children with recurrent UTI and high-grade (3-5) VUR. Antibiotic prophylaxis is not indicated in children with a normal urinary tract after UTI. Prophylaxis is recommended to prevent UTI in children with bladder bowel dysfunction (BBD) and those with high-grade VUR. In children with VUR, prophylaxis should be stopped if the child is toilet trained, free of BBD, and has not had a UTI in the last 1 year. Surgical intervention in high-grade VUR can be considered for parental preference over antibiotic prophylaxis or in children developing recurrent breakthrough febrile UTIs on antibiotic prophylaxis.

A multinational survey on the management of the urinary tract in newborns with spina bifida: Are we following current EAU/ESPU guidelines?

AIMS

In August 2019, the European Association of Urology (EAU) and European Society for Paediatric Urology (ESPU) published updated guidelines on the management of neurogenic bladder in children and adolescents. Our study aimed to establish whether members of the ESPU are adhering to these guidelines.

METHODS

We designed a survey comprising 26 questions using SurveyMonkey®. Respondents were asked about management of neurogenic bladder at birth in newborns with spina bifida (SB), urological investigations, as well as short and long-term follow-up in their institutions.

RESULTS

There were 103 respondents to the survey (754 recipients, giving a response rate of 14%) spanning 36 countries. 100% of respondents carry out a renal/bladder ultrasound at birth. Only 53% routinely commence clean intermittent catheterization soon after birth as recommended by the guidelines. Only 56% recommend anticholinergic medications after abnormal videourodynamics (VUDs). The guidelines recommend the use of continued antibiotic prophylaxis if there is evidence of vesicoureteral reflux and hostile bladder/non-conclusive results on VUDs which is followed by only 30% of providers. 63% of respondents carry out baseline VUDs at the recommended time. Seeing larger volumes of SB patients, having a formal SB protocol, having formal SB multidisciplinary clinics and working in a tertiary referral center did not make respondents more likely to adhere to guidelines.

CONCLUSIONS

Our survey demonstrated that large variations from the EAU/ESPU guidelines exist in practice. The study confirms that further work is required across institutions and countries to implement these evidence-based recommendations for standardized practice.

EAU/ESPU guidelines on the management of neurogenic bladder in children and adolescent part I diagnostics and conservative treatment

BACKGROUND

In childhood, the most common reason for a neurogenic bladder is related to spinal dysraphism, mostly myelodysplasia.

AIMS

Herein, we present the EAU/ESPU guidelines in respect to the diagnostics, timetable for investigations and conservative management including clean intermittent catheterization (CIC).

MATERIAL AND METHODS

After a systematic literature review covering the period 2000 to 2017, the ESPU/EUAU guideline for neurogenic bladder underwent an update.

RESULTS

The EAU/ESPU guideline panel advocates a proactive approach. In newborns with spina bifida, CIC should be started as soon as possible after birth. In those with intrauterine closure of the defect, urodynamic studies are recommended be performed before the patient leaves the hospital. In those with closure after birth urodynamics should be done within the next 3 months. Anticholinergic medication (oxybutynin is the only well-investigated drug in this age group-dosage 0.2-0.4 mg/kg weight per day) should be applied, if the urodynamic study confirmed detrusor overactivity. Close follow-up including ultrasound, bladder diary, urinalysis, and urodynamics are necessary within the first 6 years and after that the time intervals can be prolonged, depending on the individual risk and clinical course. In all other children with the suspicion of a neurogenic bladder due to various reasons as tethered cord, inflammation, tumors, trauma, or other reasons as well as those with anorectal malformations, urodynamics-preferable video-urodynamics, should be carried out as soon as there is a suspicion of a neurogenic bladder and conservative treatment should be started soon after confirmation of the diagnosis of neurogenic bladder. With conservative treatment the upper urinary tract is preserved in up to 90%, urinary tract infections are common, but not severe, complications of CIC are quite rare and continence can be achieved at adolescence in up to 80% without further treatment.

DISCUSSION AND CONCLUSIONS

The transition into adulthood is a complicated time for both patients, their caregivers and doctors, as the patient wants to become independent from caregivers and treatment compliance is reduced. Also, transition to adult clinics for patients with neurogenic bladders is often not well-established.

[Not Available]

Question Je connais la fréquence des infections des voies urinaires (IVU) chez les enfants, de même que leurs séquelles potentielles si elles ne sont pas traitées. Par conséquent, dans notre clinique, nous traitons par antibiothérapie tous les enfants souffrant d’IVU symptomatiques. Par ailleurs, devrions-nous en faire autant chez les enfants qui ont une bactériurie asymptomatique?

Réponse La bactériurie asymptomatique (BUA) était habituellement traitée avec des antibiotiques dans toutes les populations, y compris les enfants. Par ailleurs, selon les données probantes plus récentes, l’antibiothérapie ne s’est pas révélée bénéfique et entraîne même souvent des préjudices dans le traitement de la BUA chez l’enfant. Certaines études font valoir qu’en raison de la microbiologie différente en cause dans la BUA, celle-ci ne devrait pas être considérée comme appartenant au spectre des IVU. Ces enfants ne devraient pas recevoir d’antibiothérapie à moins d’avoir subi une greffe de rein ou des interventions urologiques invasives.

Management of asymptomatic bacteriuria in children

Question I am aware of how common pediatric urinary tract infection (UTI) is, and of the potential long-term sequelae if left untreated. Therefore, in our practice we treat every child who presents with symptomatic UTI with antibiotics. However, should the same practice be applied to children with bacteriuria that is asymptomatic?Answer Historically, asymptomatic bacteriuria (ABU) was treated with antibiotics in all populations, including in children. However, more recent evidence has shown no benefit and often harm associated with the use of antibiotics to treat pediatric ABU. Some studies suggest that owing to the different microbiology associated with ABU it should not be considered in the spectrum of UTI. These children should not be treated with antibiotics unless they have received a renal transplant or have undergone invasive urologic procedures.

Asymptomatic Bacteriuria and Bacterial Interference

Asymptomatic bacteriuria is very common. In healthy women, asymptomatic bacteriuria increases with age, from <1% in newborns to 10% to 20% of women age 80 years, but is uncommon in men until after age 50 years. Individuals with underlying genitourinary abnormalities, including indwelling devices, may also have a high frequency of asymptomatic bacteriuria, irrespective of age or gender. The prevalence is very high in residents of long-term-care facilities, from 25% to 50% of women and 15% to 40% of men. Escherichia coli is the most frequent organism isolated, but a wide variety of other organisms may occur. Bacteriuria may be transient or persist for a prolonged period. Pregnant women with asymptomatic bacteriuria identified in early pregnancy and who are untreated have a risk of pyelonephritis later in pregnancy of 20% to 30%. Bacteremia is frequent in bacteriuric subjects following mucosal trauma with bleeding, with 5% to 10% of patients developing severe sepsis or septic shock. These two groups with clear evidence of negative outcomes should be screened for bacteriuria and appropriately treated. Asymptomatic bacteriuria in other populations is benign and screening and treatment are not indicated. Antimicrobial treatment has no benefits but is associated with negative outcomes including reinfection with antimicrobial resistant organisms and a short-term increased frequency of symptomatic infection post-treatment. The observation of increased symptomatic infection post-treatment, however, has led to active investigation of bacterial interference as a strategy to prevent symptomatic episodes in selected high risk patients.

Long-term, low-dose prophylaxis against urinary tract infections in young children

Urinary tract infection (UTI) affects about 2 % of boys and 8 % of girls during the first 6 years of life with Escherichia coli as the predominant pathogen. Symptomatic UTI causes discomfort and distress, and carries a risk of inducing renal damage. The strong correlation between febrile UTI, dilating vesicoureteral reflux (VUR), and renal scarring led to the introduction of antibiotic prophylaxis for children with VUR to reduce the rate of UTI recurrence. It became common practice to use prophylaxis for children with VUR and other urinary tract abnormalities. This policy has been challenged because of a lack of scientific support. Now, randomized controlled studies are available that compare prophylaxis to no treatment or placebo. They show that children with normal urinary tracts or non-dilating VUR do not benefit from prophylaxis. Dilating VUR may still be an indication for prophylaxis in young children. After the first year of life, boys have very few recurrences and do not benefit from prophylaxis. Girls with dilating VUR, on the other hand, are more prone to recurrences and benefit from prophylaxis. There has been a decline in the use of prophylaxis due to questioning of its efficacy, increasing bacterial resistance, and a propensity to low adherence to medication. Alternative measures to reduce UTI recurrences should be emphasized. However, in selected patients carefully followed, prophylaxis can protect from recurrent UTI and long-term sequelae. 1. There is a strong correlation between UTI, VUR, and renal scarring. 2. Children with normal urinary tracts or non-dilating VUR do not benefit from prophylaxis. 3. Young children, mainly girls, with dilating VUR are at risk of recurrent UTI and acquired renal scarring and seem to gain from antibiotic prophylaxis. 4. Increasing bacterial resistance and low adherence with prescribed medication is a major obstacle to successful antibiotic prophylaxis.

A prospective multi-center trial of Escherichia coli extract for the prophylactic treatment of patients with chronically recurrent cystitis

We have assessed the efficacy and safety of Escherichia coli extract (ECE; Uro-Vaxom) which contains active immunostimulating fractions, in the prophylactic treatment of chronically recurrent cystitis. Forty-two patients with more than 2 episodes of cystitis in the proceeding 6 months were treated for 3 months with one capsule daily of ECE and observed for a further 6 months. The primary efficacy criterion was the number of episodes of recurrent cystitis during the 6 months after treatment compared to those during the 6 months before treatment. At the end of the 9-month trial, 34 patients (all women) were eligible for statistical analysis. Their mean age was 56.4 yr (range, 34-75 yr), and they had experienced recurrent urinary tract infections for 7.2+/-5.2 yr. The number of recurrences was significantly lower during the 6-month follow-up period than during the 6 months preceding the trial (0.35 vs. 4.26, P<0.001). During the follow-up, 28 (82.4%) patients had no recurrences and 4 (11.8%) had 1 each. In patients who relapsed, ECE alleviated cystitis symptoms, including painful voiding, frequency and urgency. There were no serious adverse events related to the study drug. Our study demonstrates the efficacy and safety of ECE in the prophylactic treatment of chronically recurrent cystitis.

Asymptomatic bacteriuria in the elderly: high prevalence and high turnover of strains

Asymptomatic bacteriuria (ASB) was followed in repeated prevalence surveys in a cohort of non-institutionalized residents (n=330), aged>or=80 y. Urine samples were collected at baseline, and at 6, and at 18 months. Phenotyping (PhenePlate) was performed on isolates of Escherichia coli to evaluate strain relatedness. ASB occurred in 19.0, 19.4, and 19.9% in women, and in 9.4, 9.6 and 7.9% in men, at baseline and at the 6- and 18-months follow-up, respectively, and ASB was found at least once in 37% of women and in 20% of men. Of those with ASB at baseline, 60% also had ASB in the 2 subsequent surveys. Among those with persisting E. coli bacteriuria, 76% and 40%, respectively, carried the same strain at the 6- and 18-months follow-ups. In women, we found that the risk of developing a symptomatic urinary tract infection within 24 months was higher among those with ASB at baseline than in those without bacteriuria (p=0.019). ASB is common and often persistent, but we found a high turnover of strains, indicating a high rate of recolonization.

Meningomylocele: An update

Therapy-resistant overactivity of detrusor or small capacity and poor compliance, will usually need to be treated by bladder augmentation. Ileal or colonic patches are used frequently for augmenting the bladder, with either intestinal segment appearing to be equally useful. Stomach is rarely used because of the associated complications, but it is the only available intestinal segment for patients with impaired renal function. Concerns regarding long-term effects of associated metabolic acidosis, including abnormalities in linear growth and bone metabolism are misplaced. Ureterocystoplasty offers an attractive urothelium-preserving alternative, avoiding the metabolic complications, mucus production and cancer risk of heterotopic epithelium associated with enterocystoplasty. Though ideal for patients with dilated ureter and nonfunctioning kidney, in patients with functioning kidney it carries added risks associated with transuretero-ureterostomy, mainly obstruction. Ureteral dilatation in meningomyelocele patients is avoidable with proper follow-up and treatment. Therefore they rarely should be candidates for this operation. Alternative urothelium-preserving techniques, such as auto augmentation and seromuscular cystoplasty, have not proven to be as successful as standard augmentation with intestinal segment. Work is in progress on various bioengineering techniques to culture and combine bladder cells in tissue culture for regeneration. Early efforts are exciting, but preliminary.

Bacterial interference—is deliberate colonization with Escherichia coli 83972 an alternative treatment for patients with recurrent urinary tract infection?

The increasing microbial antibiotic resistance motivates research for non-antibiotic treatment alternatives. In recurrent urinary tract infections (UTIs), 'bacterial interference' has attracted interest as a possible alternative treatment option. The observation that asymptomatic bacteriuria (ABU) protects against recurrent UTI has prompted clinical trials with deliberate colonization of the human urinary tract as an alternative approach in patients with recurrent UTI. The strain used for colonization, the ABU isolate Escherichia coli 83972, has been shown to cause symptom-free colonizations for long periods of time. Patients on long-term colonization report a subjective benefit, and UTI treatments are rare in colonized patients. This report presents an update on open long-term E. coli 83972 colonization trials and describes the design of an ongoing randomized trial.

Escherichia coli, fimbriae, bacterial persistence and host response induction in the human urinary tract

Urinary tract infections (UTI) are among the most common bacterial infections in humans. Symptomatic UTIs may be acute, recurrent or chronic but the most frequent form of UTI is asymptomatic bacteruria (ABU). In ABU, the mucosa remains inert, despite the presence of large bacterial numbers in urine. The difference in disease severity reflects the virulence of the infecting strain and the propensity of the host to respond to infection. It is essential to understand the molecular basis of disease diversity and the molecular interactions between bacteria and host that determine asymptomatic carriage and the transition to disease. We discuss the initial interactions between bacteria and the mucosal surfaces in the human urinary tract, and the bacterial factors involved in the breach of mucosal inertia. Specifically, the contribution of P and type 1 fimbriae to bacterial establishment and host response induction are investigated. The results show that P fimbriae serve as independent virulence factors when expressed by an ABU strain, by promoting the establishment of bacteriuria and the innate host response, which is the cause of symptoms and tissue damage. P fimbriae thus fulfil the molecular Koch postulates as independent virulence factors in the human urinary tract. Type 1 fimbriae, in contrast, did not act as virulence factors in this model, and thus appear to serve a different function in man than in the murine model.

Toll-like receptor 4 expression and cytokine responses in the human urinary tract mucosa

Mucosal pathogens trigger a local innate host response by activating epithelial cells. Bacterial adherence and Toll-like receptor 4 (TLR4) signaling have been implicated as key events in this process. This study addressed the molecular basis of the epithelial response to gram-negative infection in the human urinary tract. Mucosal biopsies were obtained from kidneys, ureters, and bladders of patients undergoing urinary tract surgery, and epithelial TLR4 and CD14 expression was examined by immunohistochemistry. TLR4 was detected in epithelial cells lining the entire urinary tract and in the renal tubular epithelium. CD14, in contrast, was completely absent from the epithelial tissue. The response of the epithelial cells to infection was studied by in vitro challenge of the biopsies with uropathogenic Escherichia coli bacteria. A rapid cytokine response was observed, with production of interleukin-1beta (IL-1beta), IL-6, and IL-8 but not of IL-4 or gamma interferon. Adhering, P- or type 1-fimbriated E. coli activated IL-6 and IL-8 production more efficiently than the nonfimbriated control, as shown by cellular staining and analysis of secreted cytokines. The results demonstrate that human uroepithelial cells possess the molecular machinery needed to respond to uropathogenic E. coli. This includes recognition receptors for fimbriae and TLR4 for transmembrane signaling. We speculate that the lack of membrane-bound CD14 allows the epithelium to regulate its sensitivity to lipopolysaccharide and to discriminate between more-virulent and less-virulent strains.

Asymptomatic bacteriuria: when to screen and when to treat

Asymptomatic bacteriuria is common. Populations with structural or functional abnormalities of the genitourinary tract may have an exceedingly high prevalence of bacteriuria, but even healthy individuals frequently have positive urine cultures. Asymptomatic bacteriuria is seldom associated with adverse outcomes. Pregnant women and individuals who are to undergo traumatic genitourinary interventions are at risk for complications of bacteriuria and benefit from screening and treatment programs. Although screening is recommended for renal transplant recipients, the benefits for these patients are less clear. For other populations, including most bacteriuric individuals, negative outcomes attributable to asymptomatic bacteriuria have not been described. Treatment of asymptomatic bacteriuria in these patients is not beneficial and, in fact, may be associated with harmful outcomes, such as increased short-term frequency of symptomatic infection, adverse drug effects, and reinfection with organisms of increased antimicrobial resistance. Screening for asymptomatic bacteriuria and treatment is recommended for only selected groups where benefit has been shown. Many research questions still need to be addressed. Different populations have unique risk factors, and the benefits and risks of different management approaches for asymptomatic bacteriuria must continue to be addressed systematically in appropriate clinical trials.

Urinary tract infections: what's new?

PURPOSE

This review provides practicing urologists with important basic information about urinary tract infections (UTIs) that can be applied to everyday clinical problems.

MATERIALS AND METHODS

A review is presented of provocative and controversial concepts in the current literature.

RESULTS

Bacterial virulence mechanisms are critical for overcoming the normal host defenses. Increasing antimicrobial resistance of uropathogens has led to reconsideration of traditional treatment recommendations in many areas. For effective patient management the first issue is to define complicating urological factors. Managing complicated urinary tract infections, particularly in urology, is determined by clinical experience to define the pertinent anatomy and to determine the optimal interventions. New clinical data are summarized on UTIs in long-term care patients, behavioral risks for UTI in healthy women and anatomical differences associated with an increased risk for UTI. The rationale is presented for UTI prophylaxis using cranberry juice, immunization and bacterial interference. Current treatment trends for UTI include empiric therapy (without urine culture and sensitivity testing), short-course therapy, patient-administered (self-start) therapy and outpatient therapy for uncomplicated pyelonephritis.

CONCLUSIONS

Recommendations for treating patients with UTIs have changed based on basic science and clinical experience.

P fimbriae enhance the early establishment of Escherichia coli in the human urinary tract

This study examined the role of P fimbriae in the establishment of bacteriuria. Patients (n = 17) were subjected to intravesical inoculation with an asymptomatic bacteriuria strain, Escherichia coli 83972, or its P-fimbriated (pap+/prs+) transformants. As shown by groupwise analysis, the pap+/prs+ transformants established bacteriuria more rapidly than E. coli 83972 (P = 0.021) and required a lower number of inoculations to reach 105 cfu ml-1 (P = 0.018). Intraindividual analysis showed that the pap+/prs+ transformants established bacteriuria more rapidly than E. coli 83972 in the patients who subsequently became carriers of both strains. Finally, bacterial establishment was shown to vary with the in vivo expression of P fimbriae. Bacterial counts were higher when P-fimbrial expression was detected than when the pap+/prs+ strain showed a negative phenotype. The results suggested that P fimbriae enhance the establishment of bacteriuria and fulfil the molecular Koch postulates as a colonization factor in the human urinary tract.

Virulence properties of Escherichia coli 83972, a prototype strain associated with asymptomatic bacteriuria

Little is known about bacteria associated with asymptomatic bacteriuria (ABU) with regard to urinary tract colonization mechanisms. In this study, virulence properties of Escherichia coli 83972, a strain that was isolated from a clinical ABU episode, were examined. The genetic potential for expression of P and type 1 pili was demonstrated, and DNA sequences related to type 1C and G (UCA) pilus genes were also detected. However, E. coli 83972 did not express D-mannose-resistant or D-mannose-sensitive hemagglutination after growth under standard conditions in vitro or upon isolation from the urine of colonized test subjects. Limited uroepithelial cell adherence was observed in vivo, and weak D-mannose-sensitive hemagglutination was detected after extended growth in urine in vitro.

The natural history of bacteriuria in childhood

Urinary tract infections are common during infancy and childhood but are easily overlooked because of the unspecific symptoms. Prevention of renal scarring and its potential long-term consequences is possible but requires an increased awareness of the diagnosis, the imaging revealing anomalies within the urinary tract, and the long-term supervision. This should include any possibility of the child having pyelonephritic recurrences, which should be treated without delay; however, asymptomatic bacteriuria in infants and children is an innocent condition and screening is not recommended.

Bacterial adherence and mucosal cytokine responses. Receptors and transmembrane signaling

By attaching to cells or secreted mucosal components, microbes are thought to avoid elimination by the flow of secretions that constantly wash mucosal surfaces. The attached state enhances their ability to trap nutrients and allows the bacteria to multiply more efficiently than do unattached bacterial cells. Attachment is therefore regarded as an end result in itself, and emphasis has been placed on the role of adherence for colonization of mucosal surfaces. Specific adherence was shown to be essential for the tissue tropism that is to guide microbes to their respective sites of colonization/infection. Attachment is not only a mechanism of tissue targeting but also a first step in the pathogenesis of many infections. The attaching bacteria engage in a "cross-talk" with the host cells through the mutual exchange of signals and responses. Enteropathogenic E. coli induce attaching and effacing lesions (Finley et al., this issue). Shigella and Listeria sp. invade the cells and cause actin polymerization (Sansonetti et al., this issue). This review describes the ability of bacteria to trigger mucosal inflammation through activation of cells in the mucosal lining. The results suggest that receptors for bacterial adhesins bind their ligands with a high degree of specificity and that ligand-receptor interactions trigger transmembrane signaling events that cause cell activation. Receptors for microbial ligands thus appear to fulfill also the same criteria as those used to define receptors for other classes of ligands such as hormones, growth factors, and cytokines.

Bacteriuria in children with neurogenic bladder treated with intermittent catheterization: natural history

OBJECTIVE

To determine whether bacteriuria unassociated with symptoms in patients with neurogenic bladder will lead to symptomatic infection and/or deterioration of the upper urinary tract if left untreated, we examined whether bacteriuria persisted in bladder urine of children with neurogenic bladder treated with clean intermittent catheterization (CIC) and whether persistence of bacteria led to symptomatic infection or deterioration of the upper urinary tract.

DESIGN

Weekly home visits were made during 6 months of surveillance of 14 children on the CIC regimen with a normal upper urinary tract and no reflux (as determined by renal ultrasonography, voiding cystourethrography, and serum creatinine measurement). During visits a sample of bladder urine was obtained by CIC, and signs and symptoms of urinary tract infection and all medications were recorded.

RESULTS

Fourteen children were observed for 323 weeks. Cultures of 70% (172/244) of the urine samples collected were positive for organisms (> or = 10(4) colony-forming units per milliliter), 152 (88%) for the usual pathogens and 20 (12%) for commensal organisms. Bacteriuria was associated with pyuria two thirds of the time, regardless of bacterial species. Carriage of the same pathogen for 4 weeks or longer, with associated pyuria, was common during surveillance. Despite frequent episodes of bacteriuria with associated pyuria, there were only five symptomatic infections during the 323 patient-weeks. Children remained clinically well during the study period, and their upper urinary tract did not deteriorate.

CONCLUSION

Bacteriuria persists for weeks in symptom-free children being treated with CIC for neurogenic bladder associated with a normal upper urinary tract. Before attempts are made to eradicate bacteriuria, treatment should be proved to be beneficial to this population.

Biochemical fingerprinting of urinary Escherichia coli causing recurrent infections in women with pyelonephritic renal scarring

A biochemical fingerprinting system, especially designed for subtyping of Escherichia coli and suitable for screening large number of bacterial strains was used in a long-term follow-up study of 19 women with non-obstructive pyelonephritic renal scarring and recurrent urinary infections in order to examine whether recurrent infections mostly are relapses or reinfections in this group of patients. Seventy-six recurrent infections occurred during a 47-month follow-up (0.09 infections per observation month). The majority of the recurrences were reinfections (58/76, 76%) and 18 (24%) were relapses caused by E. coli. Approximately 50% of relapses and reinfections caused by E. coli were symptomatic while the majority of reinfections caused by other bacteria were asymptomatic (23/30, 77%). In one patient a relapse of E. coli infection occurred more than two years (745 days) after the initial infection. Reinfections may occur early (7 days) after cessation of antimicrobial therapy in this group of patients. Two patients had an episode of symptomatic bacteriuria 51 and 56 days after asymptomatic bacteriuria with the same E. coli strain was detected. Biochemical fingerprinting of the E. coli isolates revealed that they belong to a wide variety of biochemical phenotypes which indicates that they are not members of widespread uropathogenic clones.

Persistence of Escherichia coli bacteriuria is not determined by bacterial adherence

The role of bacterial adherence in the persistence of bacteria in the human urinary tract was analyzed. Women with chronic symptomatic urinary tract infections were subjected to deliberate colonization with nonvirulent Escherichia coli, after eradication of their current infections. E. coli organisms were instilled into the bladder through a catheter. The strain used for colonization, E. coli 83972, was isolated from a patient with stable bacteriuria. It lacked expressed adherence factors and did not belong to the uropathogenic O:K:H serotypes. Strain 83972 was transformed with the pap and pil DNA sequences encoding Gal alpha 1-4Gal beta- and mannose-specific (type 1) adhesins. Patients were colonized with a mixture of the wild-type and the transformed strains. E. coli 83972 caused stable bacteriuria for greater than 30 days in 7 of 12 individuals. In contrast, the Gal alpha 1-4 Gal beta-recognizing or mannose-binding transformants were eliminated within 48 h. The consistent superiority of the wild-type strain in establishing stable bacteriuria when compared with the adhesive transformants did not appear to be due to differences in growth rates or to plasmid segregation. Rather, the transformants expressing the adhesin determinants were selectively eliminated by the host. This suggested that the acquisition of adherence factors is not sufficient to increase the fitness of E. coli for survival in the urinary tract of humans.

Selection and evolution of virulence in bacteria: an ecumenical excursion and modest suggestion

Why do parasites kill their hosts? During this past decade, research in three different areas; evolutionary ecology, medical microbiology, and population genetics has provided theory and data that address this and related questions of selection and the evolution and maintenance of parasite virulence. A general theory of parasite-host coevolution and the conditions for selection to favour parasite virulence has been put forth. Considerable advances have been made in elucidating the mechanisms of pathogenicity and inheritance of virulence in bacteria. The population genetic structure and the relationship between pathogenic and non-pathogenic forms has been determined for a number of species of bacteria. We critically review these developments and their implications for questions of selection and the evolution and maintenance of virulence in bacteria. We postulate how selection may operate on specific types of bacterial virulence and present a general protocol to experimentally test hypotheses concerning selection and the evolution of virulence in bacteria.