Level Of Bacteriuria Research Articles

Lipocalin 2 imparts selective pressure on bacterial growth in the bladder and is elevated in women with urinary tract infection.

Competition for iron is a critical component of successful bacterial infections, but the underlying in vivo mechanisms are poorly understood. We have previously demonstrated that lipocalin 2 (LCN2) is an innate immunity protein that binds to bacterial siderophores and starves them for iron, thus representing a novel host defense mechanism to infection. In the present study we show that LCN2 is secreted by the urinary tract mucosa and protects against urinary tract infection (UTI). We found that LCN2 was expressed in the bladder, ureters, and kidneys of mice subject to UTI. LCN2 was protective with higher bacterial numbers retrieved from bladders of Lcn2-deficient mice than from wild-type mice infected with the LCN2-sensitive Escherichia coli strain H9049. Uropathogenic E. coli mutants in siderophore receptors for salmochelin, aerobactin, or yersiniabactin displayed reduced fitness in wild-type mice, but not in mice deficient of LCN2, demonstrating that LCN2 imparts a selective pressure on bacterial growth in the bladder. In a human cohort of women with recurrent E. coli UTIs, urine LCN2 levels were associated with UTI episodes and with levels of bacteriuria. The number of siderophore systems was associated with increasing bacteriuria during cystitis. Our data demonstrate that LCN2 is secreted by the urinary tract mucosa in response to uropathogenic E. coli challenge and acts in innate immune defenses as a colonization barrier that pathogens must overcome to establish infection.

Use of d‐mannose in prophylaxis of recurrent urinary tract infections (UTIs) in women

Recurrent UTIs, defined as at least two UTIs in 6 months or three UTIs in 1 year, are a significant burden for the patient and result in high costs to the health system. There are several options for preventing recurrent UTIs, including antibiotic prophylaxis, methenamin prophylaxis and topical oestrogen. The two most commonly used strategies are long-term low-dose antibiotic prophylaxis and post-coital antibiotic prophylaxis for women who have UTI associated with sexual intercourse. Large reviews have shown that antibiotic prophylaxis lasting from 6 to 12 months (or even longer) significantly reduces the number of clinical recurrences in women with recurrent UTIs, but there is no consensus on when to start the prophylaxis, on how long it should last or at which dose and schedule the antibiotic should be taken. Several prophylactic antibiotic regimens can be used with the same efficiency. The most commonly prescribed regimens are trimethoprim-sulfamethoxazole (or trimethoprim alone), nitrofurantoin, cephalexin and the fluoroquinolones at a quarter of the usual daily dose for 6 months. The downsides of long-term antibiotic prophylaxis are possible adverse reactions (although rare), costs and increasing bacterial resistance to antibiotics; therefore, alternative prophylactic agents, such as cranberry juice and probiotics have been extensively studied. One such agent is D-mannose, which is normally present in human metabolism and has an important role, especially in the glycosylation of certain proteins. The supposed mechanism of action is inhibition of bacterial adherence to urothelial cells. In vitro experiments have shown that D-mannose binds and blocks FimH adhesin, which is positioned at the tip of the type 1 fimbria of enteric bacteria. During bacterial colonization, FimH binds to carbohydrate-containing glycoprotein receptors on the epithelium of the urinary tract. As it is similar in structure to the binding site of urothelial glycoprotein receptors, D-mannose acts as a competitive inhibitor of bacterial adherence; in sufficient concentration in urine D-mannose causes saturation of FimH adhesins and prevents the bacteria from binding to urothelial receptors. As well as in vitro, reduction of bacteriuria levels has also been confirmed in in vivo animal UTI models [1]. A similar anti-adhesive effect mechanism has been suggested for Tamm–Horsfall protein. The mannose-containing side chains of the protein bind bacteria and facilitate their elimination [2]. It is important to note that the anti-adhesive effect of mannose depends on the configuration of the molecule. Only D-isomer and α-anomer (α-D-mannose) can bind and block the FimH adhesin. Other carbohydrates have little or no anti-adhesive effect [3].

MICROBIOTA URINE BEFORE AND AFTER LITHOTRIPSY FOR RENAL STONES

Extracorporeal shock wave lithotripsy (ESWL) in spite of the low invasiveness and high efficiency is accompanied by an infectious- inflammatory complications and renal parenchymal injury . Dynamics of microbial spectrum urine and the impact of postoperative antibiotic therapy currently remains unexplored. The study included 30 patients subjected to ESWL. Bacteriological study was midstream morning urine before ESWL, 1, 3 days after ESWL, and midstream urine in the first urination after ESWL. All patients were divided into 2 groups. Group I consisted of patients (46.7%) with antibiotic therapy . Group II patients (53.3 %) antibiotic therapy was performed. In most cases (97.8 %) were bacteriuria , while in 75% of cases highlighted in the various options bacterial associations representation aerobic- anaerobic mixed infection, among which was dominated by non-clostridial anaerobic bacteria in all samples. Revealed that after ESWL microbial spectrum urine does not change in any case within 3 days , except for Enterobacteriaceae, but the frequency of occurrence and level of bacteriuria vary for different periods after surgery and fees or absence of antibiotic therapy.

Prevalence Of Urinary Tract Infection During Pregnancy

Urinary tract infections (UTI) are the most common bacterial infections during pregnancy. Untreated UTI can be associated with serious obstetric complications. This cross-sectional study was carried out to determine the prevalence of UTI among pregnant women attending in two private tertiary medical college hospital of Dhaka. A total of 250 pregnant women were enrolled in this study. UTI was diagnosed using mid stream urine (MSU) culture. Using > 105 colony forming unit per milliliter as significant level of bacteriuria, the prevalence was found to be 26.0%. There was a high incidence in 21–25 years age group (44.61%). There was also high incidence of infection in the third trimester of pregnancy (78.46%) comparid to first (9.23%) and second trimester (12.30%). Multiparty is associated with increased urinary tract infection in pregnancy. Regarding education 10% were literate and 90% were illiterate. Prevalence of bacteriuria was 94% in women who had past history of urinary tract infection. 80% were sexually active. E.coli was the most frequently isolated pathogen (88.15%).These findings underscores the importance of screening all pregnant women for significant bacteriuria, so that positive cases should be treated subsequently with antibiotics in order to reduce the adverse effects on both maternal and fetal health DOI: http://dx.doi.org/10.3329/jdnmch.v17i2.12200 J. Dhaka National Med. Coll. Hos. 2011; 17 (02): 8-12

597 ANTIMICROBIAL RESISTANCE PATTERNS OF ESCHERICHIA COLI IN UNCOMPLICATED COMMUNITY-ACQUIRED URINARY TRACT INFECTIONS AMONG ADULTS: A META-ANALYSIS

You have accessJournal of UrologyInfections/Inflammation of the Genitourinary Tract: Kidney & Bladder1 Apr 2010597 ANTIMICROBIAL RESISTANCE PATTERNS OF ESCHERICHIA COLI IN UNCOMPLICATED COMMUNITY-ACQUIRED URINARY TRACT INFECTIONS AMONG ADULTS: A META-ANALYSIS Frank J. Penna, Jack S. Elder, and Mireya Diaz Frank J. PennaFrank J. Penna More articles by this author , Jack S. ElderJack S. Elder More articles by this author , and Mireya DiazMireya Diaz More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.911AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Resistance to recommended antibiotic regimens for community-acquired (CA) Escherichia coli (E. coli)-associated urinary tract infections (UTI) is increasing. Determination of resistance patterns is essential to define regimens that correlate with better outcomes. The present study sought to estimate the resistance rates to four commonly prescribed antibiotics from contemporary cohorts. METHODS A MEDLINE search was performed for articles published after 1999 using the terms “urinary tract infections” and “antibiotic resistance”, and a combination of specific antibiotics. All articles reporting resistance patterns from CA E. coli-UTIs were selected. Cohorts including isolates from ER visits, inpatients, or if the number of isolates for uncomplicated cases could not be determined were excluded. For each study, characteristics related to the design, average patient, UTI, and bacteria were extracted. The overall resistance rates to ampicillin (AMP), ciprofloxacin (CIP), trimethoprim-sulfamethoxazole (SXT), and nitrofurantoin (NIT) were estimated using mixed effects. RESULTS A total of 84,074 E. coli isolates were tested between 1998 and 2007 among North American and European cohorts. The majority of studies prospectively collected samples from symptomatic women, and used standard thresholds for MIC, but defined bacteriuria disparately. Figure 1 shows Forest plots with estimates and their 95% confidence intervals, number of isolates, region, level of bacteriuria, and initial accrual year for each study. Heterogeneity was present, with studies clustering above and below the overall rate, but no single characteristic could identify these groupings. Cohorts including isolates from before 2000 found significantly decreased rates for all antibiotics, while studies with three or four significantly increased resistance rates started after 2000. Patterns of SXT resistance were similar to those of CIP and AMP in 78% of studies, increased in 57% (4 out 7) of these. CONCLUSIONS Increasing resistance patterns to four first line antibiotics represent a challenge to the empirical management of uncomplicated CA-UTI. The single or cross-resistant nature among these antibiotics is a matter of future studies. Detroit, MI© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e235 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Frank J. Penna More articles by this author Jack S. Elder More articles by this author Mireya Diaz More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Bacteriuria in patients with an orthotopic ileal neobladder: urinary tract infection or asymptomatic bacteriuria?

To investigate the prevalence of asymptomatic bacteriuria (ABU) and urinary tract infection (UTI), and the local and systemic inflammatory response, in patients with ileal neobladder. The study included 40 patients who had a radical cystectomy and ileal neobladder. Two urine samples, one for chemical and physical analysis, and cytofluorimetry, and one for urine culture, were collected every 3 months for 9 months after surgery. Of 119 urine cultures, 69 (57%) were positive for bacteria. Only nine of the 40 patients had no bacteriuria on urine culture. Escherichia coli strains were cultured from eight of 10 patients with persistently positive urine. The incidence of bacteriuria was different according to gender. There was a high concentration of leukocytes (0-6 microL) in 118 of 119 samples. The mean concentration of leukocytes in sterile urine culture was 1181/microL, while in patients with ABU the mean was 491 (P < 0.05). A positive urine culture is a very common finding in patients with an orthotopic bladder. The most interesting results was the absence of elevated inflammatory indices and/or symptoms, even in those patients with high levels of bacteriuria. Probably this is due to the completely different inflammatory response of ileal mucosa against bacteria than has bladder mucosa. Indeed, the leukocyte concentration detected in urinary sediment was inversely association with bacterial growth in urine cultures. These findings suggest a redefinition of ABU and UTI in patients with an orthotopic neobladder.

Asymptomatic bacteriuria of pregnancy in Ibadan, Nigeria: a re-assessment

Asymptomatic bacteriuria in pregnancy is the major risk factor for developing symptomatic urinary tract infection during pregnancy. In the present study, 300 pregnant women are screened for significant asymptomatic bacteriuria in order to provide an insight into the prevalence in developing countries, reassessment of some predisposing factors and aetiological agents and their susceptibility tests. The mean age of the patients in the study is 26.8 years (SD: 5.8 years, range: 16–40 years). Using 103 organisms/mL as a significant level of bacteriuria, the prevalence was found to be 21.0%. One hundred and fifty-eight samples had no pus cells with 25 showing significant bacteriuria, 116 samples contained 1–4 pus cells/high power field (hpf) with 25 showing significant bacteriuria, while 26 samples had ≥5 pus cells/hpf with 13 showing significant bacteriuria. There was no particular trend associated with age and rate of infection. However, there was a decline in the rate of infection in the 26–30 age group, with a sharp increase as age increased. There was high incidence of bacteriuria during the third trimester of pregnancy (21.9%) compared with that in the first trimester (7.7%), while the level in the second trimester was 22.5%. Multiparity is associated with increased bacteriuria in pregnancy. Thirty-one (49.2%) isolates grew Gram-negative bacilli; 27 (42.9%) grewGram-positive cocci and the remainder (7.9%) grew yeast-like cells. Staphylococcus aureus was the most frequent pathogen (41.3%), followed by Klebsiella species (33.3%) and Escherichia coli (11.1%). Bacterial isolates from this study were most sensitive to ceftazidime, followed by ceftriazone, and least susceptible to co-trimoxazole.

Outils du diagnostic biologique des infections urinaires nosocomiales (IUN) : analyse critique

Nosocomial urinary tract infections (NUTI) are the most frequent nosocomial infections. They are often associated with vesical catheterization. The current criteria of definition are based on the presence of symptoms, of vesical catheterization, and on the level of pyuria and bacteriuria determined by urinalysis. These definitions do not take into account all situations and must be reviewed. The conditions of sampling, transfer to the laboratory, and conservation of urines greatly influence the level of pyuria and the level and nature of bacteriuria. The interpretation of the urinalysis must take into account various clinical and epidemiological situations. Patients harboring an urinary catheter are often asymptomatic; they present a nonspecific pyuria all the more frequent that the duration of catheterization is long. Among these patients, the diagnosis of NUTI is based primarily on the level of the bacteriuria which is generally polymicrobial and always present after long-term catheterization. The absence of pyuria is a good negative predictor for non-catheterized symptomatic patients. Pyuria associated with bacteriuria, even low (10 3 to 10 5 cfu mL –1), proves the presence of UTI in these patients. Screening by urinary reagent strips cannot replace urinalysis for either symptomatic or catheterized patients. The systematic screening of UTI (using either a urinary reagent strips or urinalysis) is justified only when treatment is required in case of positive results.

The prevalence of bacteriuria in older institutionalized patients

We set out to determine the prevalence of bacteriuria in elderly patients institutionalised in 10 homes in Northumberland. Single mid-stream urine (MSU) specimens were collected from 161 asymptomatic patients aged 64-101 years. Thirty-four (21%) samples had > 100 white blood cells (WBC/microliter) on microscopy as well as a significant bacteriuria of > 10(8) bacteria/l, being suggestive of a true urinary tract infection. A total of 115(71%) samples had < 100 WBC. Seventy-five (46%) samples could be described as 'contaminated' or 'infection unlikely' but of these only 31 (19.2% of all samples) were reported as 'contaminated' by the laboratory. This study confirms previous work in America to indicate the high level of bacteriuria in institutionalised elderly patients as well as the very high number (46%) who may show bacteriuria but no rise in the number of WBC suggesting contamination only. Nurses and GPs must be very cautious in interpreting MSU results from such patients.

Criteria for the diagnosis of urinary tract infection

Despite years of clinical experience with urinary tract infection, the criteria for the diagnosis of this common condition are controversial. Accumulating evidence confirms prior suggestions that criteria must be flexible and varied, depending on the clinical syndrome encountered. The combination of pyuria and bacteriuria, with a uropathogen present at a urine colony count level predictive of infection, offers the best way to distinguish infection from contamination of the collected urine specimen. The level of bacteriuria on quantitative urine culture that should be considered significant varies from 10(2) to 10(5) colonies or more per milliliter of urine, depending on the clinical setting.

Rapid isolation and presumptive diagnosis of uropathogens by using membrane filtration and differential media

Random urine samples from hospitalized patients (n = 550) and seeded sterile filtered urine samples (n = 730) were used to test a membrane filtration technique, Qualture (Future Medical Technologies International, Inc., West Palm Beach, Fla.), for the detection and identification of uropathogens. Results for each sample were compared with those obtained by the calibrated loop (0.01 ml) method to demonstrate the sensitivity of the method as a screening tool and the specificity of the presumptive diagnosis obtained from the pattern of growth on differential media. The medium was supplied as dehydrated nutrient pads (Sartorius AG, Goettingen, Germany) and was activated by rehydration by the addition of the liquid specimen. With a threshold of 10(4) CFU/ml defining a positive culture, the sensitivity of the Qualture was 100%. At lower levels of bacteriuria, the Qualture was more sensitive than the calibrated loop method. Significant infections were presumptively diagnosed at 4 h by filtration rather than at 24 h on agar medium. The specificity of uropathogen identification ranged from 99% for Enterococcus spp. to 83% for Pseudomonas spp. Citrobacter spp. could not be differentiated from Escherichia coli and Providencia spp. could not be differentiated from Proteus spp., which does not create a therapeutic dilemma. Filtration, isolation, quantitation, and presumptive diagnosis are performed in one step, without subculture. Membrane filtration is a sensitive and rapid technique, with the advantage that it can be used as a collection and transport device without the use of growth inhibitors.

Laboratory in the Diagnosis and Management of Urinary Tract Infections

The laboratory is essential in the diagnosis and management of UTIs. The presence of pyuria and bacteriuria, the two most important indicators of UTIs, are most accurately determined by standard techniques. In quantitating pyuria, the finding of greater than or equal to 10 leukocytes/mm3 of urine by either hemocytometry or direct microscopy correlates highly with symptomatic, culture-proven UTIs. The determination of bacteriuria by direct microscopy is inaccurate, particularly at lower levels of bacteriuria; thus, quantitative urine cultures remain the most accurate measure of bacteriuria. Significant bacteriuria, previously defined as greater than or equal to 10(5) CFU/ml of urine, has been redefined with the observation that as few as 10(2) CFU/ml can be associated with significant pyuria and symptoms suggestive of cystitis. The need for routine and posttreatment urine cultures in nonpregnant women with acute dysuria remains controversial, but current data suggest that they are usually unnecessary. Rapid diagnostic tests for detection of pyuria and bacteriuria are designed to increase efficiency and decrease cost in the diagnosis of UTI. Unfortunately, none of these techniques can quantitate pyuria or bacteriuria as accurately as the standard methods, but the level of accuracy offered by the standard methods is not always necessary in the care of patients with uncomplicated UTIs. These tests are particularly well suited for screening asymptomatic high-risk populations. Noninvasive localization techniques continue to be explored as possible alternatives to invasive localization procedures, but they remain largely research tools that are not readily available to the practicing clinician. Understanding the applicability and appropriate use of newer technologies in the evaluation of patients with UTIs and how these technologies complement the standard diagnostic techniques will lead to better, more efficient, and less costly patient care.

Rapid Bacteriuria Screening in a Urological Setting: Clinical Use

The clinical use of a commercially available semiautomated bacteriuria screening device was evaluated in a urological setting. The 1,300 consecutive urine specimens processed by the device were contrasted with results of standard semiquantitative culture. A small number (2 per cent) were screened unsuccessfully owing to a clogged filter. With greater than 105 colony-forming units per ml. the sensitivity of the device was 91 per cent but it was only 81 per cent with bacteriuria levels greater than 104 colony-forming units per ml. More importantly, the predictive value of a negative test was 99 per cent with more than 105 colony-forming units per ml. and 96 per cent with more than 104 colony-forming units per ml. This capability promotes safe urological instrumentation and timely patient care.

Bacteriuria in the catheterized patient. What quantitative level of bacteriuria is relevant?: Stark, R. P., and D. G. Maki. 1984. N. Engl. J. Med. 311:560–564

Bacteriuria in the catheterized patient. What quantitative level of bacteriuria is relevant?: Stark, R. P., and D. G. Maki. 1984. N. Engl. J. Med. 311:560–564

Use of rapid screening tests in processing urine specimens by conventional culture and the AutoMicrobic system.

Two rapid urine screening tests, the Chemstrip LN (BioDynamics, Indianapolis, Ind.) and the Bac-T-Screen urine screening device (Marion Laboratories, Inc., Kansas City, Mo.), were evaluated as techniques to predict bacteriuria as quantitated by either conventional culture or the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.). A total of 666 urine specimens were analyzed by both screening tests as well as the AutoMicrobic system and quantitative culture. The sensitivities of both Chemstrip LN and Bac-T-Screen for the detection of low levels of bacteriuria (greater than or equal to 10(3) CFU/ml) were comparable (73.3 and 74.4%, respectively) and were too low to recommend their use as a primary urine screen. Their excellent predictive value of a negative result at the 10(5) CFU/ml level (96 and 97.5%, respectively) makes them potentially useful in predicting urine specimens with less than 10(5) CFU/ml. The use of either of these tests in combination with the AutoMicrobic system markedly decreased the time required to classify urine specimens. Their low cost relative to the AutoMicrobic system urine card makes the use of either test cost effective as a screen for the AutoMicrobic system.

Bacteriuria: Colonization or Infection-Reply

In Reply.— Dr Kozinn and colleagues call attention to the semantic confusion that exists regarding the terms used to define UTI in asymptomatic catheterized patients. Ideally, one would like to distinguish between colonization, asymptomatic infection, and symptomatic infection. 1 Colonization is usually defined as the multiplication of organisms in or on a host without apparent evidence of invasiveness or tissue injury, while clinical, histologic, or immunologic evidence of host injury or invasion accompanies infection. 1 The distinction between colonization and infection in the urinary tract thus rests on (1) the presence of symptoms or signs indicating tissue invasion, (2) the presence of pyuria and/or hematuria, (3) a serological response, or (4) cystoscopic or histologic evidence of mucosal injury. It is not clear that any quantitative level of bacteriuria in catheterized patients correlates with infection rather than colonization. Indeed, patients with lower bacterial counts generally progress to higher counts (≥10 5

An evaluation of a leukocyte esterase/nitrite test strip and a bioluminescence assay for detection of bacteriuria

A leukocyte esterase/nitrite (Chemstrip LN TM) and a bioluminescence assay (Lumac TM) were evaluated for detection of bacteriuria in 1,000 urine specimens. Both devices provided high predictive negative values (95.4–97.8%); however, false-negative values at levels of bacteriuria ≥10 4 CFU/ml were 22.6% and 12.3%, respectively, for the leukocyte esterase/nitrate and the bioluminescence assay tests. The corresponding false-negative values at levels of bacteriuria of ≥10 5 CFU/ml were 16.5% and 3.9%, respectively.

Rapid screening of urine for significant bacteriuria by Gram stain, acridine orange stain, and the Autobac MTS system

Urine specimens submitted for microbiologic examination were screened for evidence of bacteriuria by three rapid methods: Gram staining, acridine orange staining, and the Autobac MTS system. The screening results were compared with those obtained by semiquantitative colony counts on agar plates. In this comparative study 1055 urine specimens were examined, of which 146 (13.8%) had colony counts of ≥1 × 10 5/ml. All thre urine screening methods detected this level of bacteriuria at a sensitivity of 98% and a specificity of 55.2% (acridine orange), 66.0% (Gram stain), and 83.2% (Autobac), respectively. Of the 1055 urine specimens examined, 185 (17.5%) had colony counts of ≥1 × 10 4/ml, at which level the sensitivity of the three methods was 93% and the specificity was 56.7% (acridine orange), 68.0% (Gram stain), and 86.0% (Autobac), respectively. For any level of sensitivity, the Autobac urine screen was shown to be more specific than either the Gram stain or the acridine orange method. The acridine orange stain was the least specific urine screen, especially at the upper limits of sensitivity.

Effect of D-mannose and D-glucose on Escherichia coli bacteriuria in rats.

The effect of D-mannose and D-glucose on bacteriuria due to Escherichia coli with mannose-sensitive adhesins was investigated in adult male Sprague-Dawley rats undergoing diuresis. Inocula of 10(5), 10(7), or 10(8) bacteria in 0.1 ml of normal saline or 2.5% or 10% D-mannose or D-glucose were injected intravesically and urine was cultured 1, 3, 5, 7 and 9 days later. The levels of bacteriuria on days 1 and 5 were significantly lower in rats inoculated with 10(5) E coli and 10% D-mannose than in controls (p less than 0.05 and 0.01 respectively) and the percentages of rats with less than 100 bacteria/ml were higher on days 1 and 3 (p = 0.05 and 0.02 respectively). Bacteriuria was significantly lower in rats inoculated with 10(7) bacteria and 10% D-mannose than in controls on days 5 and 7 (p less than 0.01 for each day) and the percentage of rats with less than 100 bacteria/ml was higher on day 7 (p = 0.01). D-glucose reduced bacteriuria significantly only with a concentration of 10% after instillation of 10(5) E. coli (p less than 0.05, day 1). The results indicate that D-mannose and D-glucose can significantly reduce bacteriuria within 1 day and that their efficacy is dependent upon the concentration of both saccharide and bacteria.

Evaluation and optimization of urine screening by Autobac.

The purpose of this investigation was to evaluate the effectiveness of the Autobac (Pfizer Inc., New York, N.Y.) urine screen for detection of bacteriuria in 3,026 urine specimens and to establish the optimum procedure for the Autobac system. Overall, 97% of urine specimens having greater than 10(5) colony-forming units (CFU) per ml were detected within 5 h by the Autobac system. The system detected 66, 90, and 94% of such specimens after 2, 3, and 4 h of incubation, respectively. Of specimens having 10(4) to 10(5) CFU/ml, the Autobac system detected 10, 45, 53, and 95% after 2, 3, 4, and 5 h of incubation, respectively. The rate of false-positive results increased from 0% after 2 h to 2% after 3 h to 6% after 4 h and 25% after 5 h of incubation. The specificity of the urine screening results also varied with the incubation time. Percentages of specimens having greater than 10(5) CFU/ml that gave positive urine screening results at various times were as follows: 96% at 2 h, 74% at 3 h, 29% at 4 h, and 9% at 5 h. These findings suggest that a 3- or 4-h urine screening procedure will effectively detect bacteriuria of greater than 10(5) CFU/ml, with few false-positive results. However, a 5-h procedure, which gives more false-positive results, may be needed for detection of lower levels of bacteriuria.