The etiology of urinary tract infection: traditional and emerging pathogens

The microbial etiology of urinary infections has been regarded as well established and reasonably consistent. Escherichia coli remains the predominant uropathogen (80%) isolated in acute community-acquired uncomplicated infections, followed by Staphylococcus saprophyticus (10% to 15%). Klebsiella, Enterobacter, and Proteus species, and enterococci infrequently cause uncomplicated cystitis and pyelonephritis.The pathogens traditionally associated with UTI are changing many of their features, particularly because of antimicrobial resistance. The etiology of UTI is also affected by underlying host factors that complicate UTI, such as age, diabetes, spinal cord injury, or catheterization. Consequently, complicated UTI has a more diverse etiology than uncomplicated UTI, and organisms that rarely cause disease in healthy patients can cause significant disease in hosts with anatomic, metabolic, or immunologic underlying disease. The majority of community-acquired symptomatic UTIs in elderly women are caused by E coli. However, gram-positive organisms are common, and polymicrobial infections account for up to 1 in 3 infections in the elderly. In comparison, the most common organisms isolated in children with uncomplicated UTI are Enterobacteriaceae. Etiologic pathogens associated with UTI among patients with diabetes include Klebsiella spp., Group B streptococci, and Enterococcus spp., as well as E coli. Patients with spinal cord injuries commonly have E coli infections. Other common uropathogens include Pseudomonas and Proteus mirabilis.Recent advances in molecular biology may facilitate the identification of new etiologic agents for UTI. The need for accurate and updated population surveillance data is apparent, particularly in light of concerns regarding antimicrobial resistance. This information will directly affect selection of empiric therapy for UTI.     

Reducing the risk of catheter-related urinary tract infection

It is estimated that 10-12 per cent of hospital patients and four per cent of patients in the community have a urinary catheter at any one time (Stamm, 1998). Urinary tract infections (UTIs) account for almost half of all health care-associated infection (HAI), and a significant number of these infections are related to the insertion of urinary catheters (Pratt et al, 2001). Recent research has estimated that a patient who has a catheter for 20 days is almost certain to develop a catheter-related UTI and that the cost of treatment of UTI is estimated as being 1,327 pounds sterling per patient (Roadhouse and Wellsted, 2004). Plowman et al (1999) have estimated that a UTI can extend the length of a patient's stay in hospital by six days.     

Antibiotic susceptibility of bacterial strains isolated from urinary tract infections in Poland

Worldwide data show that there is increasing resistance among urinary tract pathogens to conventional drugs. The aim of this study was to obtain data on susceptibility patterns of pathogens responsible for urinary tract infections (UTIs) in Poland to currently used antimicrobial agents. A multicentre study of 141 pathogens from hospital-acquired infections and 460 pathogens from community-acquired infections was carried out between July 1998 and May 1999. The most prevalent aetiological agent was Escherichia coli (73.0%), followed by Proteus spp. (8.9%) and other species of Enterobacteriaceae (9.6%). Few community infections were caused by Gram-positive bacteria (2.2%). Gram-positive cocci were isolated more frequently from a hospital setting (14.1%) and the most common were Enterococcus spp. (8.5%). Pseudomonas aeruginosa was found only among hospital isolates and was responsible for 10.7% of infections. E. coli isolates from both community and hospital infections were highly susceptible to many antimicrobial agents with the exception of those isolates producing extended-spectrum beta-lactamases (ESBLs). Of all Enterobacteriaceae tested, 38 strains (6.9%) were capable of producing ESBLs.     

Investigation of the rate of meningitis in association with urinary tract infection in infants 90 days of age or younger

Objective: To test the hypothesis that urinary tract infections (UTI) in young infants are rarely associated with meningitis. Methods: We undertook a review of the laboratory results from 322 infants, 90 days of age or younger, with an admission or discharge diagnosis of UTI or meningitis. The study was conducted in a tertiary paediatric hospital. The primary outcome measure was the incidence of coexisting urinary tract and cerebrospinal fluid sepsis. Results: In total, 161 of the 322 (50%) infants with an admission or discharge diagnosis of UTI or meningitis were subsequently shown to have a culture‐proven UTI. Of the children with a culture‐proven UTI, 75 (47%) had cerebrospinal fluid obtained. We detected one case of probable bacterial meningitis in association with UTI. Conclusion: UTI is rarely associated with meningitis in infants 90 days of age or younger.     

Catheterization and urinary tract infections: microbiology

Patients with urinary catheters are a substantial proportion of the total patient population and catheter care is an important area of nursing practice. Urinary tract infection associated with catheterization is known to be the most common nosocomial (hospital-acquired) infection. Urinary tract infections can be caused by exogenous microorganisms or endogenous faecal or urethral microorganisms. The different microorganisms which are responsible for causing urinary tract infections have particular characteristics. Many microorganisms form a biofilm, a living layer of cells which stick to the surfaces of the catheter and the catheter bag. Biofilms not only lead to urinary tract infections, but also they are associated with encrustation and catheter blockage. The article considers the microorganisms implicated in catheter-associated urinary tract infections and aims to develop an increased awareness of the characteristics of different pathogens which could lead to enhanced nursing practice and improved patient care.     

儿童原发性肾病综合征合并尿路感染的病原菌及耐药性分析

目的探讨原发性肾病综合征（PNS）合并尿路感染（UTI）患儿的病原菌分布及其耐药性,为临床合理使用抗菌药物提供参考。方法以2009年1月-2012年12月住院治疗且尿液细菌培养阳性的218例PNS合并UTI患儿为研究对象,回顾性分析致病菌分布和药物敏感（药敏）情况。结果75．7％（165／218）的PNS患儿表现为无症状UTI。共分离培养出249株致病菌,G-杆菌是PNS合并UTI的主要致病菌,占64.3％（160／249）,其中63．8％（102／160）的致病菌为大肠埃希菌;G＋球菌占31．7％（79／249）,其中59．5％（47／79）为粪肠球菌,真菌占4．0％。药敏结果提示,大肠埃希菌对羟苄西林、头孢唑林和头孢曲松等耐药率高（〉50％）,而对头孢哌酮／舒巴坦钠和亚胺培南等耐药率低（〈10％）。粪肠球菌对利福平耐药率（74．6％）高,而对万古霉素和利奈唑胺等耐药率低（〈10％）。结论PNS患儿多表现为无症状UTI,大肠埃希菌是其主要致病菌,但肠球菌感染的比例亦不低,这些致病菌对常规抗菌药物耐药明显且多数为多药耐药。     

Risk factors for ciprofloxacin resistance among Escherichia coli strains isolated from community-acquired urinary tract infections in Turkey

OBJECTIVES: To determine the risk factors for community-acquired ciprofloxacin-resistant Escherichia coli urinary tract infection (UTI). METHODS: The study was performed with isolates from community-acquired UTIs collected from 15 centres representing six different geographic regions of Turkey. All microbiological procedures were carried out in a central laboratory. Multivariate analysis was performed for detection of risk factors for resistance. Use of quinolones more than once within the last year, living in a rural area, having a urinary catheter, age >50 and complicated infections were included in the model as variables and logistic regression was performed. RESULTS: A total of 611 gram-negative isolates were studied: 321 were isolated from uncomplicated UTI and 290 were isolated from complicated UTI. E. coli was the causative agent in 90% of the uncomplicated UTIs and in 78% of the complicated UTIs (P < 0.001). Seventeen percent of E. coli strains isolated from uncomplicated cases and 38% of E. coli strains isolated from complicated UTI were found to be resistant to ciprofloxacin. In multivariate analysis, age over 50 [odds ratio (OR): 1.6; confidence interval (CI): 1.08-2.47; P = 0.020], ciprofloxacin use more than once in the last year (OR: 2.8; CI: 1.38-5.47; P = 0.004) and the presence of complicated UTI (OR: 2.4; CI: 1.54-3.61; P < 0.001) were found to be associated with ciprofloxacin resistance. Detection of strains of E. coli producing extended-spectrum beta-lactamase (ESBL) enzymes was two times more common in the patients who received ciprofloxacin than those who did not (15% versus 7.4%). CONCLUSIONS: The increasing prevalence of infections caused by antibiotic-resistant bacteria makes the empirical treatment of UTIs more difficult. One of the important factors contributing to these high resistance rates might be high antibiotic use. Urine culture and antimicrobial susceptibility testing are essential in Turkey for patients with UTI who have risk factors for resistance, such as previous ciprofloxacin use. Fluoroquinolone-sparing agents such as nitrofurantoin and fosfomycin should be evaluated as alternative therapies by further clinical efficacy and safety studies.     

Species and antimicrobial resistance of uropathogens isolated from patients with urinary catheter

A large number of hospitalized patients have an indwelling urinary tract catheter (IUC) placed at some time during their hospital stay and may suffer from catheter-associated urinary tract infections, the leading cause of nosocomial infections. Here we investigated the prevalence of uropathogens associated with catheter-associated urinary tract infections and assessed the resistances of these pathogens to commonly prescribed antibiotics. In total, 2,997 urine samples were examined at a regional hospital in Taipei, Taiwan in 2004: 1,948 (65%) samples from hospitalized patients and 1,049 (35%) samples from outpatients. Patients with IUCs accounted for 1,381 samples (46%). Stratified analyses were used to calculate the age- and gender-adjusted odds ratio (OR) of antimicrobial resistance associated with the use of IUCs. Compared to the urine specimens of the patients without IUCs, those isolated from catheterized patients had a lower prevalence rate of Escherichia (E.) coli (23.4% vs 36.8%) and higher rates of resistant strains including Pseudomonas species (16.4% vs 8.6%) and rare gram-negative bacilli (5.8% vs 4.5%). Additionally, IUCs significantly increased the antimicrobial resistance of E. coli (OR 2.41-3.07), other species of Enterobacteriaceae (OR 1.57-2.38), and rare gram-negative bacilli (OR 2.41-5.21) to nearly all antibiotics tested, such as trimethoprim/sulfamethoxazole. Thus, IUCs increased the prevalence of urinary tract infections caused by some highly resistant pathogens. Moreover, IUCs were associated with the increased risk of concurrent resistance of Enterobacteriaceae. Clinicians are advised to exercise better management of urinary catheter in order to further reduce and control catheter-associated urinary tract infections in hospitals.     

老年脑梗死患者尿路感染的病原菌分布及耐药性分析

目的探讨老年脑梗死患者尿路感染的病原菌分布及耐药特性,为临床合理使用抗菌药物提供科学依据。方法收集住院老年脑梗死患者尿路感染病原菌183株进行细菌鉴定,并用K-B纸片法作药敏分析。结果老年脑梗死患者尿路感染病原菌以革兰阴性杆菌为主(72.1%),分别为前3位的是大肠埃希菌(49.7%)、肠球菌属(10.9%)和肺炎克雷伯菌(10.4%.)。细菌对各种抗菌药物有不同程度的耐药率,表现为多重耐药。结论革兰阴性杆菌为尿路感染的主要病原菌,对常用抗菌药物耐药率呈上升趋势,细菌培养和药敏分析对指导临床合理使用抗菌药物,选择有效抗菌药物治疗具有重要意义。     

The means of improvement of urine bacteriologic analysis

The article outlines the information on the etiology of urinary tracts infections, the diagnostic methods and the detection of sensitivity to antiinfection pharmaceuticals of bacteria isolated from urine. In the last 20 years, the criteria of assessment of clinical significance of urinary tracts bacterial infections are refined. Also, the methodic base and arsenal of means of urine bacteriological analysis improved drastically. These changes are to be implemented in the national laboratory practice.     

187例医院内尿路感染病原分布和抗生素耐药分析

目的 :了解医院内尿路感染的病原分布和对抗生素的耐药情况及其比较与院外尿路感染的差别 ,企图以此指导临床用药。方法 :收集 187例医院内尿路感染和同期住院的 14 5例院外尿路感染进行比较。结果 :医院内尿路感染的优势菌依次为 :大肠埃希菌 2 8.2 4 % ,肠球菌 2 1.37% ,念珠菌 14 .89% ,克雷伯杆菌 8.0 2 % ,假单胞菌 7.2 5 %和链球菌 4 .96 %。其中医院内念珠菌的感染率较院外显著升高 (P <0 .0 1)。有尿路操作者中大肠埃希菌 33.33% ,肠球菌 16 .92 % ,念珠菌 16 .4 1%和假单胞菌8.2 1%。其中念珠菌和假单胞菌的感染率显著高于无尿路操作者 (P <0 .0 5 ,P <0 .0 1)。在院内感染者中 ,大肠埃希菌对环丙沙星和头孢哌酮的耐药性 ,肠球菌对青霉素的耐药性药明显高于院外感染者 (P <0 .0 5 ,P <0 .0 5 ,P <0 .0 5 )。结论 :院内尿路感染中有较多尿路操作和广谱抗生素的使用史 ,念珠菌的感染率明显升高 ,细菌对抗生素耐药的情况较多 ,应注意调整治疗方案。     

Reagent strip diagnosis of UTI in a high-risk population

A study was undertaken to determine the accuracy of reagent strip diagnosis of urinary tract infection (UTI) in patients seen in the ED who were subsequently admitted to hospital with this diagnosis. The reagent strip results of 100 patients were recorded and the sensitivity and specificity of various parameters in the diagnosis of UTI were calculated. Our results indicate that even in a group of patients with high clinical probability of UTI and with symptoms severe enough to be hospitalized, reliance on positivity of any single parameter alone gives unacceptably low sensitivity: 89%, 39%, 68%, and 63% for WBC, nitrite, RBC, and protein, respectively. We conclude that dipstick analysis is not sufficiently sensitive for diagnosis of UTI in high risk patients in whom missed diagnosis would have serious consequences.     

Urinary tract infections

Urinary tract infection (UTI), with its diverse clinical syndromes and affected host groups, remains one of the most common but widely misunderstood and challenging infectious diseases encountered in clinical practice. Antimicrobial resistance is a leading concern, with few oral options available to treat infections caused by Gram-negative organisms resistant to trimethoprim-sulfamethoxazole and fluoroquinolones, especially for patients with upper tract disease. Efforts should be made not to detect or treat asymptomatic bacteriuria and funguria; to ensure an appropriate duration of therapy for symptomatic infections; and to limit the use of broad-spectrum agents, especially fluoroquinolones, if narrower spectrum agents are available. Further research is needed regarding rapid diagnosis of UTI, accurate presumptive identification of patients with resistant pathogens, and development of new antimicrobials for drug-resistant UTI.     

Urinary tract infection in the impaired host

In general, defects in phagocytosis and in humoral or cellular immunity do not appear to predispose to the acquisition of UTI but do influence the clinical manifestations and the severity, microbiology, and complications of infection once it is established. The incidence of UTI in immunosuppressed patients other than diabetics or renal transplant recipients is not higher than the incidence in nonimmunosuppressed individuals. The higher frequencies of infection seen in diabetics and in renal transplant recipients correlate best with the duration of bladder instrumentation rather than with glycosuria or immunosuppressive regimen. Neutropenia blunts the clinical manifestations of UTI and predisposes to bacteremia. Use of broad spectrum antibiotics results in alterations in indigenous flora, promotes urinary infections with resistant nosocomial pathogens, and predisposes to fungemia with hematogenous seeding of the urinary tract. Routine screening for detection of asymptomatic bacteriuria and prompt institution of antimicrobial therapy is indicated only in renal transplant recipients within 3 months of their surgery and not in any of the other diseases discussed.     

Does urinary tract infection caused by extended-spectrum β-lactamase-producing Escherichia coli show same antibiotic resistance when it recurs?

This study was performed to evaluate what percentage of urinary tract infections (UTIs) caused by extended spectrum β-lactamase (ESBL)-producing strains recurs with ESBL-producing strains during follow up and to assess the risk factors for recurrence with ESBL-producing Escherichia coli strains on subsequent first recurrence episode. We enrolled female patients with UTIs caused by ESBL-producing E. coli between May 2012 and December 2015, who were longitudinally followed up for at least 24 months. Among the 206 patients with ESBL positive UTI, 180 completed the study. 60 (60/180, 33.3%) of patient with first episode of UTI caused by ESBL-producing E. coli experienced recurrent UTIs during follow up. Of 60 patients, 43 (43/60, 71.7%) recurred with ESBL-producing E. coli on the first UTI recurrence episode. On multivariate analysis, the time to recurrence and history of cephalosporin usage in the last 6 months were identified as risk factors for recurrence with ESBL-producing E. coli per se (odds ratio [OR] = 0.9, 95% confidence interval [CI] 0.8–1.0, p = 0.030 and OR = 27.0, 95% CI 2.4–299.8, p = 0.007, respectively). These findings show that high proportion of patient with UTI caused by ESBL-producing E. coli recurs with ESBL-producing E. coli on subsequent recurrence episode. While result of antibiotic susceptibility cannot be identified on the visit day empirical treatment should be referred to the antecedent antibiotic resistance profile in patients whose previous UTIs were due to ESBL-producing strains.     

Susceptibility of Recent Bacterial Isolates to Cefdinir and Selected Antibiotics among Children with Urinary Tract Infections

Background: Cefdinir, an extended‐spectrum cephalosporin administered orally, is approved by the U.S. Federal Drug Administration for treatment of skin and respiratory tract infections. During the last two years at the authors' institution, this agent has been used as an off‐label treatment for urinary tract infections in children. Objectives: To evaluate antimicrobial susceptibility testing data in children to determine whether there is support for this prescribing practice. Methods: In this retrospective study (2003–2004), the authors compared the susceptibility patterns of urinary pathogens to cefdinir and selected antibiotics in children who were evaluated for urinary tract infections in an urban tertiary academic pediatric emergency department. Pathogens (community acquired vs. opportunistic or nosocomial) were categorized as susceptible, indeterminate, or resistant on the basis of antibiotic susceptibility breakpoints. The frequency of these categorizations for individual drugs was determined. Results: Seven hundred five isolates were recovered from urine during the study period. Pathogens isolated most frequently were Escherichia coli, Klebsiella spp, and Proteus spp. Of 431 isolates retained in the data set, 412 (95.6%) were susceptible to cefdinir. This rate was comparable or superior to rates observed for other antibiotics: 49.4% for ampicillin, 84.9% for trimethoprim–sulfamethoxazole, 88.4% for cefazolin, 93.3% for nitrofurantoin, 94.2% for ticarcillin–clavulanate potassium, 97.5% for gentamicin, and 97.7% for ceftriaxone. Cefdinir, however, had lower activity (64.7%) against 17 bacterial isolates categorized as opportunistic or nosocomial pathogens. Conclusions: Cefdinir provides good coverage against common pathogens responsible for urinary tract infections in children and compares favorably with other oral and parenteral antibiotics that are used in the empiric treatment of this infection.     

What are the risk factors for recurrent UTI with repeated ESBL-producing Enterobacteriaceae? A retrospective cohort study

IntroductionA previous study has shown that two-thirds of patients with urinary tract infections (UTIs) caused by extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae experience recurrence with the same bacteria on subsequent UTI episodes. However, little is known about which patients suffer from UTI due to ESBL-producing Enterobacteriaceae repeatedly. This study aimed to investigate the risk factors for recurrent UTI due to repeated ESBL-producing organism infections.MethodsThis retrospective, single-center, observational cohort study screened all patients with UTI caused by ESBL-producing strains between January 2012 and April 2019. Among the patients who were followed up, patients who experienced UTI recurrence were enrolled and divided into two groups: ESBL recurrence group and non-ESBL recurrence group. Multivariable Cox proportional hazards regression analyses were performed to evaluate the association between patient characteristics and the development of recurrent UTI caused by ESBL-producing Enterobacteriaceae.ResultsA total of 330 patients were followed up after the diagnosis of UTI caused by ESBL-producing organisms. Among the patients, 115 (34.8%) experienced UTI recurrence, and 71 (61.7%) of them experienced subsequent recurrent UTI due to ESBL-producing organisms. Patient's age (hazard ratio [HR], 1.02; 95% confidence interval [CI], 1.00–1.04; P = 0.046) and recurrent UTI history (HR, 1.69; 95% CI, 1.05–2.72; P = 0.031) were significantly associated with an increased risk of recurrence with ESBL-producing Enterobacteriaceae.ConclusionThese findings showed that a history of previous frequent UTI recurrence is the risk factor for recurrence of UTI due to repeated ESBL producing Enterobacteriaceae infections.