Validity of microscopy for diagnosing urinary tract infection in general practice - a systematic review

Overcoming challenges in the management of recurrent urinary tract infections

INTRODUCTION

Urinary tract infection (UTI) is a major global health concern. While acute UTIs can usually be effectively treated, recurrent UTIs (rUTIs) impact patients for years, causing significant morbidity and can become refractory to front-line antibiotics.

AREAS COVERED

This review discusses the risk factors associated with rUTI, current rUTI treatment paradigms, prophylactic strategies, and challenges in rUTI diagnostics. We specifically discuss common risk factors for rUTI, including biological sex, age, menopause status, and diabetes mellitus. We also review recently available evidence for commonly used treatments, from oral antibiotic therapy to intravesical antimicrobials, electrofulguration of chronic cystitis, and the last-resort treatment, cystectomy. We discuss the most current literature evaluating prophylactic strategies for rUTI including long-term antibiotic prophylaxis, estrogen hormone therapy, and dietary supplements. Finally, we address the important role of UTI diagnostics in effective rUTI management and review the strengths and limitations of both current and emerging UTI diagnostic platforms as well as their ability to operate at point-of-care.

EXPERT OPINION

We discuss the current challenges faced by clinicians in managing rUTI in women and the steps that should be taken so that clinicians, scientists, and patients can work together to better understand the disease and develop better strategies for its management.

Comprehensive insights into UTIs: from pathophysiology to precision diagnosis and management

Urinary tract infections (UTIs) are the second most common infectious disease, predominantly impacting women with 150 million individuals affected globally. It increases the socio-economic burden of society and is mainly caused by Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter spp., and Staphylococcus spp. The severity of the infection correlates with the host factors varying from acute to chronic infections. Even with a high incidence rate, the diagnosis is mainly based on the symptoms, dipstick analysis, and culture analysis, which are time-consuming, labour-intensive, and lacking sensitivity and specificity. During this period, medical professionals prescribe empirical antibiotics, which may increase the antimicrobial resistance rate. Timely and precise UTI diagnosis is essential for addressing antibiotic resistance and improving overall quality of life. In response to these challenges, new techniques are emerging. The review provides a comprehensive overview of the global burden of UTIs, associated risk factors, implicated organisms, traditional and innovative diagnostic methods, and approaches to UTI treatment and prevention.

Dipsticks and point-of-care Microscopy to reduce antibiotic use in women with an uncomplicated Urinary Tract Infection (MicUTI): protocol of a randomised controlled pilot trial in primary care

INTRODUCTION

Uncomplicated urinary tract infections (uUTIs) in women are common infections encountered in primary care. Evidence suggests that rapid point-of-care tests (POCTs) to detect bacteria and erythrocytes in urine at presentation may help primary care clinicians to identify women with uUTIs in whom antibiotics can be withheld without influencing clinical outcomes. This pilot study aims to provide preliminary evidence on whether a POCT informed management of uUTI in women can safely reduce antibiotic use.

METHODS AND ANALYSIS

This is an open-label two-arm parallel cluster-randomised controlled pilot trial. 20 general practices affiliated with the Bavarian Practice-Based Research Network (BayFoNet) in Germany were randomly assigned to deliver patient management based on POCTs or to provide usual care. POCTs consist of phase-contrast microscopy to detect bacteria and urinary dipsticks to detect erythrocytes in urine samples. In both arms, urine samples will be obtained at presentation for POCTs (intervention arm only) and microbiological analysis. Women will be followed-up for 28 days from enrolment using self-reported symptom diaries, telephone follow-up and a review of the electronic medical record. Primary outcomes are feasibility of patient enrolment and retention rates per site, which will be summarised by means and SDs, with corresponding confidence and prediction intervals. Secondary outcomes include antibiotic use for UTI at day 28, time to symptom resolution, symptom burden, number of recurrent and upper UTIs and re-consultations and diagnostic accuracy of POCTs versus urine culture as the reference standard. These outcomes will be explored at cluster-levels and individual-levels using descriptive statistics, two-sample hypothesis tests and mixed effects models or generalised estimation equations.

ETHICS AND DISSEMINATION

The University of Würzburg institutional review board approved MicUTI on 16 December 2022 (protocol n. 109/22-sc). Study findings will be disseminated through peer-reviewed publications, conferences, reports addressed to clinicians and the local citizen's forums.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT05667207.

Urinary tract infections: a review of the current diagnostics landscape

Urinary tract infections are the most common bacterial infections worldwide. Infections can range from mild, recurrent (rUTI) to complicated (cUTIs), and are predominantly caused by uropathogenic Escherichia coli (UPEC). Antibiotic therapy is important to tackle infection; however, with the continued emergence of antibiotic resistance there is an urgent need to monitor the use of effective antibiotics through better stewardship measures. Currently, clinical diagnosis of UTIs relies on empiric methods supported by laboratory testing including cellular analysis (of both human and bacterial cells), dipstick analysis and phenotypic culture. Therefore, development of novel, sensitive and specific diagnostics is an important means to rationalise antibiotic therapy in patients. This review discusses the current diagnostic landscape and highlights promising novel diagnostic technologies in development that could aid in treatment and management of antibiotic-resistant UTIs.

Treating urinary tract infections in the era of antibiotic resistance

INTRODUCTION

Urinary tract infections (UTIs) are associated with 25-40% of antibiotics consumed in primary care and are, therefore, driving antibiotic resistance. The worldwide increase in antibiotic resistance especially in Escherichia coli has complicated the treatment choices for UTIs and absence of effective oral antibiotics may lead to increasing need for more effective treatments.

AREAS COVERED

In this review we focus on the importance of the correct diagnosis of UTI as based on proof of urinary pathogens in the urine and discuss diagnostic measures including microscopy, dipstick, and culture. Antibiotic treatment can often await diagnostic measures with pain relief such as ibuprofen. The risk of an uncomplicated UTI leading to pyelonephritis is low (1-2%) and presence of bacteria in the bladder leaves some time for the immune system to react. Three antibiotics are recommended as based on their activity, and low propensity to select for resistance, i.e. nitrofurantoin, fosfomycin, and pivmecillinam, and in general, 3-5 days of treatment will suffice.

EXPERT OPINION

Understanding the usual benign course of uUTIs can help reduce antibiotic treatment in many cases, e.g. starting treatment by pain relief and awaiting the course of infection without antibiotics. Better rapid tests in primary care are urgently needed to enforce such policies.

What is the Diagnostic Accuracy of Novel Urine Biomarkers for Urinary Tract Infection?

Background

Urinary tract infection (UTI) affects half of women at least once in their lifetime. Current diagnosis involves urinary dipstick and urine culture, yet both methods have modest diagnostic accuracy, and cannot support decision-making in patient populations with high prevalence of asymptomatic bacteriuria, such as older adults. Detecting biomarkers of host response in the urine of hosts has the potential to improve diagnosis.

Objectives

To synthesise the evidence of the diagnostic accuracy of novel biomarkers for UTI, and of their ability to differentiate UTI from asymptomatic bacteriuria.

Design

A systematic review.

Data Sources and Methods

We searched MEDLINE, EMBASE, CINAHL and Web of Science for studies of novel biomarkers for the diagnosis of UTI. We excluded studies assessing biomarkers included in urine dipsticks as these have been well described previously. We included studies of adult patients (≥16 years) with a suspected or confirmed urinary tract infection using microscopy and culture as the reference standard. We excluded studies using clinical signs and symptoms, or urine dipstick only as a reference standard. Quality appraisal was performed using QUADAS-2. We summarised our data using point estimates and data accuracy statistics.

Results

We included 37 studies on 4009 adults measuring 66 biomarkers. Study quality was limited by case-control design and study size; only 4 included studies had a prospective cohort design. IL-6 and IL-8 were the most studied biomarkers. We found plausible evidence to suggest that IL-8, IL-6, GRO-a, sTNF-1, sTNF-2 and MCR may benefit from more rigorous evaluation of their potential diagnostic value for UTI.

Conclusions

There is insufficient evidence to recommend the use of any novel biomarker for UTI diagnosis at present. Further evaluation of the more promising candidates, is needed before they can be recommended for clinical use.

Cultureless enumeration of live bacteria in urinary tract infection by single-cell Raman spectroscopy

Urinary tract infections (UTIs) are the most common outpatient infections. Obtaining the concentration of live pathogens in the sample is crucial for the treatment. Still, the enumeration depends on urine culture and plate counting, which requires days of turn-around time (TAT). Single-cell Raman spectra combined with deuterium isotope probing (Raman-DIP) has been proven to identify the metabolic-active bacteria with high accuracy but is not able to reveal the number of live pathogens due to bacteria replication during the Raman-DIP process. In this study, we established a new approach of using sodium acetate to inhibit the replication of the pathogen and applying Raman-DIP to identify the active single cells. By combining microscopic image stitching and recognition, we could further improve the efficiency of the new method. Validation of the new method on nine artificial urine samples indicated that the exact number of live pathogens obtained with Raman-DIP is consistent with plate-counting while shortening the TAT from 18 h to within 3 h, and the potential of applying Raman-DIP for pathogen enumeration in clinics is promising.

Direct, Rapid Detection of Pathogens from Urine Samples

The problem of rapidly detecting pathogens directly from clinical samples poses significant analytical challenges. Addressing this issue in relation to urinary tract infections, we propose an effective protocol and related immunomagnetic test kits enabling versatile screening for the presence of pathogenic bacteria in unprocessed urine samples. To achieve this, the components of a typical immunomagnetic separation protocol were optimized towards the sensitive assessment of the aggregates formed out of immunomagnetically tagged target pathogens collected from clinical samples. Specifically, a dedicated immunomagnetic material was developed via the functionalization of standardized, micron-sized magnetic beads with generic antibodies against gram-specific bacterial constituents with mannan binding lectin. As such, we demonstrate efficient procedures for achieving the enhanced, specific, and pathogen-mediated cluster formation of these tailored affinity-coated magnetic beads in complex samples. We further show how cluster analysis, in conjunction with the use of nonspecific, inexpensive fluorescent dye, allows for a straightforward optical assessment of the bacterial load directly from urine samples. The optimized sensing protocol and related kits provide, in less than 60 min, qualitative (positive/negative) information on the bacterial load with 85% specificity and 96% sensitivity, which is appropriate to empower clinical microscopy with a new analytic dimension. The procedure is prone to automation, can be conveniently used in clinical microbiology laboratories and, since it preserves the viability of the captured bacteria, can be interfaced with downstream analyses and antimicrobial susceptibility testing. Moreover, the study emphasizes a suite of practical validation assays that are useful for bringing the tool-box of immunomagnetic materials outside the academic laboratory and into real-life applications.

Diagnostic work-up of urinary tract infections in pregnancy: study protocol of a prospective cohort study

INTRODUCTION

Symptoms of urinary tract infections in pregnant women are often less specific, in contrast to non-pregnant women where typical clinical symptoms of a urinary tract infection are sufficient to diagnose urinary tract infections. Moreover, symptoms of a urinary tract infection can mimic pregnancy-related symptoms, or symptoms of a threatened preterm birth, such as contractions. In order to diagnose or rule out a urinary tract infection, additional diagnostic testing is required.The diagnostic accuracy of urine dipstick analysis and urine sediment in the diagnosis of urinary tract infections in pregnant women has not been ascertained nor validated.

METHODS AND ANALYSIS

In this single-centre prospective cohort study, pregnant women (≥16 years old) with a suspected urinary tract infection will be included. The women will be asked to complete a short questionnaire regarding complaints, risk factors for urinary tract infections and baseline characteristics. Their urine will be tested with a urine dipstick, urine sediment and urine culture. The different sensitivities and specificities per test will be assessed. Our aim is to evaluate and compare the diagnostic accuracy of urine dipstick analysis and urine sediment in comparison with urine culture (reference test) in pregnant women. In addition, we will compare these tests to a predefined 'true urinary tract infection', to distinguish between a urinary tract infection and asymptomatic bacteriuria.

ETHICS AND DISSEMINATION

Approval was requested from the Medical Ethics Review Committee of the Academic Medical Centre; an official approval of this study by the committee was not required. The outcomes of this study will be published in a peer-reviewed journal.

Use and quality of point-of-care microscopy, urine culture and susceptibility testing for urinalysis in general practice

Objective: To describe the use and quality of point-of-care (POC) microscopy, urine culture and susceptibility testing performed in general practice in Northern Denmark from 2013 to 2018.Design: Descriptive studySetting: General practices receiving a fee for examining urine samples.Subjects: Simulated urine samples containing uropathogenic bacteria distributed by the organisation for improvement of microbiological quality (MIKAP).Main outcome measures: Percentage of use and correct answers for microscopy, culture and susceptibility testing.Results: A total of 5361 samples were analysed by the use of microscopy (39.7%), culture (66.0%) and/or susceptibility testing (76.5%). For culture, Flexicult SSI urinary kittm (87.6%) demonstrated the highest percentage of correct answers followed by chromogenic agar (85.1%) and 2-plate dipslide (85.2%). Mueller Hinton agar with tablets had the highest percentage of correct answers for susceptibility testing of most bacterial strains (84.6%), followed by Flexicult (77.2%). Furthermore, susceptibility testing with tablets (range: 76.1-84.6%) was found to be more accurate than discs (range: 72.9-75.5%). Overall, the highest percentage of correct answers was obtained when examining urine samples containing Escherichia coli: Microscopy (78.3%), culture (87.0%) and susceptibility testing (range: 84.3-90.7%).Conclusion: The quality of POC testing in general practice was high when examining urine samples containing the most common uropathogen E. coli. Surprisingly, susceptibility testing was more frequently used than culture. This approach may compromise the treatment decision as only cultures contribute with information about the flora composition and bacterial quantification. Interestingly, microscopy was the least used method even though the result may be reached within a few minutes.Key pointsThe quality of POC tests (microscopy, urine culture, susceptibility testing) performed in general practice was high when examining urine containing E. coli, whereas difficulties were observed for samples including S. saprophyticus or K. pneumoniae.Susceptibility testing was more often performed than urine culture, which indicates a problem as only urine cultures contribute with information about the flora composition and bacterial quantification.

Availability of point-of-care culture and microscopy in general practice - does it lead to more appropriate use of antibiotics in patients with suspected urinary tract infection?

Background

Urinary tract infection (UTI) is a common condition in general practice, and urine culture can help reduce inappropriate antibiotic prescriptions. In case of delay of the result, antibiotic treatment can be guided by one or more point-of-care (POC) tests. In Denmark, POC microscopy and POC urine culture are widely used for this purpose.

Objectives

To investigate if availability of POC microscopy or POC culture in general practice was associated with a more appropriate treatment decision in patients with suspected UTI while waiting for the result from the microbiological laboratory.

Methods

This prospective observational study was conducted in 2016 in general practice in the Copenhagen area, Denmark. Data on all patients presenting in general practice with symptoms of UTI were registered anonymously and a urine sample was sent for culture at the microbiological laboratory. The association between the availability of POC tests and the appropriateness of antibiotic prescribing was assessed with multivariable logistic regression.

Results

Seventy-six general practices included 1545 patients (83% female); 71% received appropriate treatment in practices with POC culture available and 65% in practices without POC culture available (p = 0.042). Having a microscope available was not associated with more appropriate treatment (70% vs. 69%, p = 0.54).

Conclusion

Availability of POC culture marginally increased appropriate treatment while waiting for the result from the microbiological laboratory. Practices should adopt a strategy where they either perform culture within the practice or send urine for culture at the microbiological laboratory.

Trial registration number

ClinicalTrials.gov NCT02698332.