A Real-Time PCR-Based Semi-Quantitative Breakpoint to Aid in Molecular Identification of Urinary Tract Infections

This study presents a novel approach to aid in diagnosis of urinary tract infections (UTIs). A real-time PCR assay was used to screen for culture-positive urinary specimens and to identify the causative uropathogen. Semi-quantitative breakpoints were used to screen for significant bacteriuria (presence of ≥10⁵ CFU/ml of uropathogens) or low-level bacteriuria (containing between 10³ and 10⁴ CFU/ml of uropathogens). The 16S rDNA-based assay could identify the most prevalent uropathogens using probes for Escherichia coli, Pseudomonas species, Pseudomonas aeruginosa, Staphylococcus species, Staphylococcus aureus, Enterococcus species and Streptococcus species. 330 urinary specimens were analysed and results were compared with conventional urine culture. Using a PCR Ct value of 25 as semi-quantitative breakpoint for significant bacteriuria resulted in a sensitivity and specificity of 97% and 80%, respectively. In 78% of the samples with monomicrobial infections the assay contained probes to detect the bacteria present in the urine specimens and 99% of these uropathogens was correctly identified. Concluding, this proof-of-concept approach demonstrates that the assay can distinguish bacteriuria from no bacteriuria as well as detect the involved uropathogen within 4 hours after sampling, allowing adequate therapy decisions within the same day as well as drastically reduce consequent urine culturing.     

Toll-Like Receptor Polymorphisms and Susceptibility to Urinary Tract Infections in Adult Women

Background

Although behavioral risk factors are strongly associated with urinary tract infection (UTI) risk, the role of genetics in acquiring this disease is poorly understood.

Methodology/Principal Findings

To test the hypothesis that polymorphisms in Toll-like receptor (TLR) pathway genes are associated with susceptibility to UTIs, we conducted a population-based case-control study of women ages 18–49 years. We examined DNA variants in 9 TLR pathway genes in 431 recurrent cystitis (rUTI) cases, 400 pyelonephritis cases, and 430 controls with no history of UTIs. In the Caucasian subgroup of 987 women, polymorphism TLR4_A896G was associated with protection from rUTI, but not pyelonephritis, with an odds ratio (OR) of 0.54 and a 95% confidence interval (CI) of 0.31 to 0.96. Polymorphism TLR5_C1174T, which encodes a variant that abrogates flagellin-induced signaling, was associated with an increased risk of rUTI (OR(95%CI): 1.81 (1.00–3.08)), but not pyelonephritis. Polymorphism TLR1_G1805T was associated with protection from pyelonephritis (OR(95%CI): 0.53 (0.29–0.96)).

Conclusions

These results provide the first evidence of associations of TLR5 and TLR1 variants with altered risks of acquiring rUTI and pyelonephritis, respectively. Although these data suggest that TLR polymorphisms are associated with adult susceptibility to UTIs, the statistical significance was modest and will require further study including validation with independent cohorts.     

Microbiology of Urinary Tract Infections in Gaborone,Botswana

Objective

The microbiology and epidemiology of UTI pathogens are largely unknown in Botswana, a high prevalence HIV setting. Using laboratory data from the largest referral hospital and a private hospital, we describe the major pathogens causing UTI and their antimicrobial resistance patterns.

Methods

This retrospective study examined antimicrobial susceptibility data for urine samples collected at Princess Marina Hospital (PMH), Bokamoso Private Hospital (BPH), or one of their affiliated outpatient clinics. A urine sample was included in our dataset if it demonstrated pure growth of a single organism and accompanying antimicrobial susceptibility and subject demographic data were available.

Results

A total of 744 samples were included. Greater than 10% resistance was observed for amoxicillin, co-trimoxazole, amoxicillin-clavulanate, and ciprofloxacin. Resistance of E. coli isolates to ampicillin and co-trimoxazole was greater than 60% in all settings. HIV status did not significantly impact the microbiology of UTIs, but did impact antimicrobial resistance to co-trimoxazole.

Conclusions

Data suggests that antimicrobial resistance has already emerged to most oral antibiotics, making empiric management of outpatient UTIs challenging. Ampicillin, co-trimoxazole, and ciprofloxacin should not be used as empiric treatment for UTI in this context. Nitrofurantoin could be used for simple cystitis; aminoglycosides for uncomplicated UTI in inpatients.     

Management of Recurrent Urinary Tract Infections in Healthy Adult Women

Recurrence after urinary tract infection (rUTI) is common in adult women. The majority of recurrences are believed to be reinfection from extraurinary sources such as the rectum or vagina. However, uropathogenic Escherichia coli are now known to invade urothelial cells and form quiescent intracellular bacterial reservoirs. Management of women with frequent symptomatic rUTI can be particularly vexing for both patients and their treating physicians. This review addresses available and promising management strategies for rUTI in healthy adult women.Key words: Recurrent urinary tract infection, Uropathogenic Escherichia coli, ProphylaxisRecurrence after urinary tract infection (rUTI) is common in adult women. One study showed that, with healthy college age women who were followed for 6 months after an index UTI, 20.9% had at least one symptomatic recurrence.¹ In another study of 179 Finnish women who were followed for 1 year after an index Escherichia coli UTI, 44% had a least one rUTI and 5% had more than three rUTIs.² Natural history studies suggest that, after an index infection, rUTIs tend to cluster in the first 3 to 4 months. The most likely time for recurrence is 30 to 60 days, and the frequency of rUTI declines with increasing duration.^3,4The majority of rUTIs are believed to be reinfection from extraurinary sources such as the rectum or vagina. However, uropathogenic E coli (UPEC) are now known to invade urothelial cells and form quiescent intracellular bacterial reservoirs (QIRS). It is thought QIRS may provide a source for bacterial persistence and UTI recurrence.^5–7Management of women with frequent symptomatic rUTI can be particularly vexing for both patients and their treating physicians. For the patient, each UTI recurrence is associated with days of lower urinary tract symptoms, general malaise, and restrictions on everyday activities.⁸ For physicians, an etiology is often never elucidated, making patient counseling difficult. Additionally, current prophylactic measures are limited, often ineffective, and may be associated with untoward side effects.     

Type 1 Fimbriae Contribute to Catheter-Associated Urinary Tract Infections Caused by Escherichia coli

Biofilm formation on catheters is thought to contribute to persistence of catheter-associated urinary tract infections (CAUTI), which represent the most frequent nosocomial infections. Knowledge of genetic factors for catheter colonization is limited, since their role has not been assessed using physicochemical conditions prevailing in a catheterized human bladder. The current study aimed to combine data from a dynamic catheterized bladder model in vitro with in vivo expression analysis for understanding molecular factors relevant for CAUTI caused by Escherichia coli. By application of the in vitro model that mirrors the physicochemical environment during human infection, we found that an E. coli K-12 mutant defective in type 1 fimbriae, but not isogenic mutants lacking flagella or antigen 43, was outcompeted by the wild-type strain during prolonged catheter colonization. The importance of type 1 fimbriae for catheter colonization was verified using a fimA mutant of uropathogenic E. coli strain CFT073 with human and artificial urine. Orientation of the invertible element (IE) controlling type 1 fimbrial expression in bacterial populations harvested from the colonized catheterized bladder in vitro suggested that the vast majority of catheter-colonizing cells (up to 88%) express type 1 fimbriae. Analysis of IE orientation in E. coli populations harvested from patient catheters revealed that a median level of ∼73% of cells from nine samples have switched on type 1 fimbrial expression. This study supports the utility of the dynamic catheterized bladder model for analyzing catheter colonization factors and highlights a role for type 1 fimbriae during CAUTI.     

A Real-Time Impedance Based Method to Assess Rhodococcus equi Virulence

Rhodococcus equi is a facultative intracellular pathogen of macrophages and the causative agent of foal pneumonia. R. equi virulence is usually assessed by analyzing intracellular growth in macrophages by enumeration of bacteria following cell lysis, which is time consuming and does not allow for a high throughput analysis. This paper describes the use of an impedance based real-time method to characterize proliferation of R. equi in macrophages, using virulent and attenuated strains lacking the vapA gene or virulence plasmid. Image analysis suggested that the time-dependent cell response profile (TCRP) is governed by cell size and roundness as well as cytoxicity of infecting R. equi strains. The amplitude and inflection point of the resulting TCRP were dependent on the multiplicity of infection as well as virulence of the infecting strain, thus distinguishing between virulent and attenuated strains.     

Yeast Infections of the Lower Urinary Tract: Recommendations for Diagnosis and Treatment

Yeast infections of the lower urinary tract are common, with the vast majority due to Candida species. Though not life-threatening, candiduria may be a marker for overall severity of illness in hospitalized patients, as it appears to predict increased mortality, particularly in critically ill patients. Diagnosis is relatively simple through culture, but exact definitions of clinical disease are elusive. Management of asymptomatic patients is generally observation with reduction of predisposing factors, whereas symptomatic patients should be treated. Therapeutic options for these infections are limited and not well studied compared with therapies for systemic candidiasis. Further studies are needed to optimize management of these patients.     

Effects of Hydrogel/Silver Coatings on In Vitro Adhesion to Catheters of Bacteria Associated with Urinary Tract Infections

Sections of sterile all-silicone-, hydrogel/silver-all-silicone-, and hydrogel/silver-latex-Foley urinary catheters were exposed to suspensions of bacteria and Candida albicans associated with urinary tract infections. The adhesion of these microorganisms to the catheters was determined with a radiolabel–cell procedure and scanning electron microscopy. Anomalous data with the radiolabel procedure were produced with the hydrogel/silver-latex catheters for certain species. These aberrant data were related to adhesion on the untreated cut ends of the latex catheter. Radiolabel-cell-adhesion procedures that involve sections of coated materials may need to be supplemented with additional procedures such as scanning electron microscopy for valid interpretations of the data. Adhesion to the hydrogel/silver catheters by both Gram-positive- and Gram-negative bacteria most commonly associated with nosocomial urinary tract infections, including a strain of Pseudomonas aeruginosa noted for its superior adhesion capacity, was significantly lower than the adhesion to the control all-silicone catheter. Received: 21 January 2000 / Accepted: 26 February 2000     

Susceptibility of Pseudomonas aeruginosa Urinary Tract Isolates and Influence of Urinary Tract Conditions on Antibiotic Tolerance

Pseudomonas aeruginosa is an opportunistic human pathogen, which can cause severe urinary tract infections (UTIs). Because of the high intrinsic antibiotic resistance of P. aeruginosa and its ability to develop new resistances during antibiotic treatment, these infections are difficult to eradicate. The antibiotic susceptibility of 32 P. aeruginosa isolates from acute and chronic UTIs were analysed under standardized conditions showing 19% multi-drug resistant strains. Furthermore, the antibiotic tolerance of two P. aeruginosa strains to ciprofloxacin and tobramycin was analysed under urinary tract-relevant conditions which considered nutrient composition, biofilm growth, growth phase, and oxygen concentration. These conditions significantly enhance the antibiotic tolerance of P. aeruginosa up to 6000-fold indicating an adaptation of the bacterium to the specific conditions present in the urinary tract. This reversible phenomenon is possibly due to the increased formation of persister cells and is based on iron limitation in artificial urine. The results suggest that the general high antibiotic resistance of P. aeruginosa urinary tract isolates together with the increasing tolerance of P. aeruginosa grown under urinary tract conditions decrease the efficiency of antibiotic treatment of UTIs.     

Rapid Hybridization Probe Assay and PCR for Detection of Chlamydia trachomatis in Urinary Tract Infections: A Prospective Study

Chlamydia trachomatis is a widespread bacterium that causes trachoma and genital tract infections in humans. The fact that the growth of this pathogen does not normally occur outside living cells poses a challenge in its diagnosis. The present study aimed to compare the efficacies of different molecular and cultural methods in the detection of C. trachomatis in urine samples collected from patients with urinary tract infections. Examined detection methods involved the Gen-Probe C. trachomatis (GP-CT) assay, direct antigen detection by enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) method. The efficacies of these methods were compared to that of the cell culture technique depending on sensitivity, specificity, and accuracy. C. trachomatis was detected in 25 out of 50 (50%) of examined urine samples using the cell culture method. Compared with this standard technique, the GP-CT assay was the most sensitive procedure, being able to detect the pathogen in all positive samples, followed by PCR and ELISA, which showed 60% and 40% sensitivities, respectively. PCR and ELISA displayed the highest level of specificity (100%) compared to the cell culture method with the GP-CT assay showing 40% specificity. The rate of accuracy was comparable between the GP-CT, PCR, and ELISA methods ranging from 70–80% of the accuracy of the cell culture method. The above results suggest that C. trachomatis is a frequent pathogen associated with upper and lower urinary tract infections. Both the GP-CT assay and PCR method can be recommended as reliable detection methods for C. trachomatis, and the GP-CT can be used as a screening tool.     

Prevalence of Transferable Drug Resistance in Drug-Resistant Bacteria Isolated from Urinary Tract Infections in Japan

Many urinary isolates which belong to the Enterobacteriaceae and bear multiple drug resistance were shown to harbor transmissible resistance factors (R factors). The levels of resistance were almost uniform in every strain investigated. The resistance markers were usually transferred as a unit. Frequency of transfer varied from host to host even when the same recipient strain was employed. However, no remarkable differences were observed in successive transfers of R factors between substrains of Escherichia coli K-12. The role of R factors in urinary tract infection is discussed.     

A Population Based Study of Seasonality of Skin and Soft Tissue Infections: Implications for the Spread of CA-MRSA

Methicillin resistant Staphylococcus aureus (MRSA) is currently a major cause of skin and soft tissue infections (SSTI) in the United States. Seasonal variation of MRSA infections in hospital settings has been widely observed. However, systematic time-series analysis of incidence data is desirable to understand the seasonality of community acquired (CA)-MRSA infections at the population level. In this paper, using data on monthly SSTI incidence in children aged 0–19 years and enrolled in Medicaid in Maricopa County, Arizona, from January 2005 to December 2008, we carried out time-series and nonlinear regression analysis to determine the periodicity, trend, and peak timing in SSTI incidence in children at different age: 0–4 years, 5–9 years, 10–14 years, and 15–19 years. We also assessed the temporal correlation between SSTI incidence and meteorological variables including average temperature and humidity. Our analysis revealed a strong annual seasonal pattern of SSTI incidence with peak occurring in early September. This pattern was consistent across age groups. Moreover, SSTIs followed a significantly increasing trend over the 4-year study period with annual incidence increasing from 3.36% to 5.55% in our pediatric population of approximately 290,000. We also found a significant correlation between the temporal variation in SSTI incidence and mean temperature and specific humidity. Our findings could have potential implications on prevention and control efforts against CA-MRSA.