Clinical Utilization of Blood and Urine Cultures and Incidences of Bacteremia and Bacteriuria in a Hospital in Thailand.

BACKGROUND To effectively treat sepsis and urinary tract infection (UTI), blood and urine cultures should be used appropriately and relative to incidences of bacteremia and bacteriuria. This study aimed to investigate the use of blood and urine cultures and incidences of bacteremia and bacteriuria in a hospital in Thailand. MATERIAL AND METHODS Medical records of patients admitted from 2016 to 2018 were randomly selected and data in the records were anonymously extracted for investigation. RESULTS From 12 000 records, data on blood and urine cultures were extracted from 9% and 4% of them, respectively. The negative rate of blood culture was 87.48%. Bacteremia was detected in 10.22%. The positive rate of urine culture was 27.38% and the contamination rate was 31.26%. Escherichia coli was the most common cause of community-onset bacteremia and bacteriuria. Methicillin-resistant coagulase-negative staphylococci and Acinetobacter baumannii were the most common cause of hospital-acquired bacteremia while yeasts were the most common cause of hospital-acquired UTI. CONCLUSIONS A high negative rate of blood culture may result not only from its low sensitivity but also from liberal test use to identify sepsis in some conditions. Improper urine collection is the main problem with use of urine culture.

Negative Urinalyses in Febrile Infants Age 7 to 60 Days Treated for Urinary Tract Infection.

The role of the urinalysis (UA) in the management of young, febrile infants is controversial. To assess how frequently infants are treated for urinary tract infection (UTI) despite having normal UA values and to compare the characteristics of infants treated for UTI who have positive versus negative UAs, we reviewed 20,570 wellappearing febrile infants 7-60 days of age evaluated at 124 hospitals in the United States who were included in a national quality improvement project. Of 19,922 infants without bacteremia and meningitis, 2,407 (12.1%) were treated for UTI, of whom 2,298 (95.5%) had an initial UA performed. UAs were negative in 337/2,298 (14.7%) treated subjects. The proportion of infants treated for UTI with negative UAs ranged from 0%-35% across hospitals. UA-negative subjects were more likely to have respiratory symptoms and less likely to have abnormal inflammatory markers than UA+ subjects, indicating that they are mounting less of an inflammatory response to their underlying illness and/or might have contaminated specimens or asymptomatic bacteriuria.

Utility of Urine Cultures in Predicting Blood Culture Susceptibilities in Patients with Bacteremic Urinary Tract Infection.

In a review of 428 patients with bacteremic urinary tract infections, urine culture susceptibility results accurately predicted blood culture results when the same organism was isolated from both cultures. Early targeted therapy using urine culture results can potentially reduce broad-spectrum antibiotic exposure and its associated adverse effects and the length of hospitalization.

Bacteremia complicating urinary tract infection by Pseudomonas aeruginosa: Mortality risk factors.

OBJECTIVES: To examine the clinical risk factors for death within 30 days of diagnosis of Pseudomonas aeruginosa-causing bacteremia after a urinary tract infection. METHODS: A total of 62 patients with Pseudomonas aeruginosa isolated from both urine and blood at the same episode from January 2009 to December 2016 were enrolled in the present study. We retrospectively investigated clinical risk factors for death by comparison between surviving patients and those who died within 30 days after diagnosis of P. aeruginosa bacteremia. The comparison for risk factors for bacteremia-related death included 31 categories, such as age, laboratory data, underlying diseases, clinical history, history of surgery, care in the intensive care unit, P. aeruginosa susceptibility to the antibiotics used at the time of bacteremia diagnosis and consultation with urological department. RESULTS: The study included 48 men and 14 women aged 71.3 ± 10.4 years. Nine patients (14.5%) died of P. aeruginosa bacteremia. Statistical analysis showed that non-survivors had significantly lower albumin levels than survivors (2.07 ± 0.62 vs 2.62 ± 0.65; P = 0.023). The non-survivors had significantly higher rates of ventilator use, history of heart disease, septic shock and lower rates of consultation with urological departments after diagnosis (P < 0.05). CONCLUSIONS: Patients with bacteremia complicating urinary infection by P. aeruginosa have a low death rate. Earlier intervention by urologists might improve patients' outcome. Lower albumin levels, ventilator use, history of heart disease and septic shock are factors associated with higher mortality rate.

The clinical significance of concomitant bacteriuria in patients with Staphylococcus aureus bacteremia. A review and meta-analysis.

BACKGROUND: Staphylococcus aureus bacteriuria (SABU) concomitant to S. aureus bacteremia (SAB) has been associated with deep-seated infections and worse prognosis. However, the relevant studies were small and inconsistent. Here, we aim to provide a review of the relevant literature, and a meta-analysis of these studies. METHODS: We searched PubMed and Scopus for studies comparing patients with SAB and concomitant SABU to patients with SAB without SABU. RESULTS: Nine relevant studies were identified, involving 1429 patients with SAB, of whom 18.5% (n = 265) had concomitant SABU. Pooling the results of those studies, SABU was significantly associated with endocarditis, bone/joint infection and septic embolism. SABU was also associated with persistent SAB, and higher mortality. CONCLUSIONS: Although SABU may be a useful marker of complicated SAB, the current literature has several limitations. Larger prospective studies are required to clarify the value of SABU in clinical decision making.

What is the role of catheter antibiotic prophylaxis for patients undergoing joint arthroplasty?

BACKGROUND: Antimicrobial prophylaxis at the time of urinary catheter insertion and removal is commonly administered in patients undergoing joint arthroplasty, despite the lack of evidence to support this practice. The rationale is the theoretical risk of prosthetic joint infection arising from bacterial seeding from the urinary tract at the time of catheterization. In an era of antimicrobial stewardship, further assessment is warranted. METHODS: This study aimed to investigate the incidence of catheter-associated (CA) bacteriuria and bacteraemia in patients undergoing total joint arthroplasty and to assess the antimicrobial susceptibility of any isolated microorganisms. This prospective observational study undertaken over a 6-month period (May to October 2014) included 99 patients undergoing elective primary hip and knee arthroplasty at St Vincent's Hospital, Melbourne. Urine specimens were collected at insertion and removal of urinary catheters along with blood cultures upon urinary catheter removal. RESULTS: Overall 98% of the cohort received catheter antimicrobial prophylaxis for urinary catheter insertion and removal; the majority of patients received gentamicin (94%). Bacteriuria on catheter insertion had an incidence of 4.4%. The incidence of CA bacteriuria was 1.3%. All cultured organisms were sensitive to commonly used antibiotics including cephazolin. There were no cases of bacteraemia with urinary catheter removal. Increasing age, American Society of Anesthesiologists status and female gender were associated with the development of bacteriuria. CONCLUSION: The incidence of CA bacteriuria and bacteraemia with antimicrobial prophylaxis is low. This study provokes discussion about the requirement of catheter prophylaxis in this surgical context and the utility of preoperative urine screening.

Effect of Bacteremia in Elderly Patients With Urinary Tract Infection.

INTRODUCTION: The clinical effect of bacteremia on outcomes in urinary tract infection (UTI) is still debated. This study aims to examine the clinical effect of bacteremia in elderly patients with UTI requiring hospital admission. METHODS: This retrospective observational study recorded the clinical features, microbiology and outcomes in a Spanish cohort of patients aged ≥65 years hospitalized for UTI in whom blood cultures were performed in the emergency department. The primary outcome of the study was in-hospital mortality. RESULTS: Of 333 patients, with a mean age of 81.6 years, 137 (41.1%) had positive blood cultures. Escherichia coli, with 223 (66.9%) cases, was the most common microorganism isolated. Independent risk factors of bacteremia were temperature >38°C, heart rate >90bpm and inversely both Enterococcus faecalis and Pseudomonas aeruginosa. Bacteremia was not associated with the length of stay in hospital (6.96 ± 3.50 days versus 7.33 ± 5.54 days, P = 0.456). Mortality rate was 9.3% with no significant difference between bacteremic and nonbacteremic cases (8.8% and 9.7%, respectively, P = 0.773). In-hospital mortality analyzed by logistic regression was associated with McCabe index >2 (20.5% survival versus 66.7% death, adjusted odds ratio = 6.31, 95% CI: 2.71-14.67; P < 0.001) but not with bacteremia (41.4% survival versus 38.7% death, adjusted odds ratio = 0.99, 95% CI: 0.43-2.29; P = 0.992). CONCLUSIONS: Our study suggests that the presence or absence of bacteremia in elderly people with UTI requiring hospitalization does not have an influence on outcomes such as in-hospital mortality or length of stay.

Diagnostic accuracy of the urinalysis for urinary tract infection in infants <3 months of age.

BACKGROUND: The 2011 American Academy of Pediatrics urinary tract infection (UTI) guideline suggests incorporation of a positive urinalysis (UA) into the definition of UTI. However, concerns linger over UA sensitivity in young infants. Infants with the same pathogenic organism in the blood and urine (bacteremic UTI) have true infections and represent a desirable population for examination of UA sensitivity. METHODS: We collected UA results on a cross-sectional sample of 276 infants <3 months of age with bacteremic UTI from 11 hospital systems. Sensitivity was calculated on infants who had at least a partial UA performed and had ≥50 000 colony-forming units per milliliter from the urine culture. Specificity was determined by using a random sample of infants from the central study site with negative urine cultures. RESULTS: The final sample included 245 infants with bacteremic UTI and 115 infants with negative urine cultures. The sensitivity of leukocyte esterase was 97.6% (95% confidence interval [CI] 94.5%-99.2%) and of pyuria (>3 white blood cells/high-power field) was 96% (95% CI 92.5%-98.1%). Only 1 infant with bacteremic UTI (Group B Streptococcus) and a complete UA had an entirely negative UA. In infants with negative urine cultures, leukocyte esterase specificity was 93.9% (95% CI 87.9 - 97.5) and of pyuria was 91.3% (84.6%-95.6%). CONCLUSIONS: In young infants with bacteremic UTI, UA sensitivity is higher than previous reports in infants with UTI in general. This finding can be explained by spectrum bias or by inclusion of faulty gold standards (contaminants or asymptomatic bacteriuria) in previous studies.

Urinary proteins, vitamin D and genetic polymorphisms as risk factors for febrile urinary tract infection and relation with bacteremia: a case control study.

OBJECTIVE/PURPOSE: Febrile urinary tract infection (UTI) is a common bacterial disease that may lead to substantial morbidity and mortality especially among the elderly. Little is known about biomarkers that predict a complicated course. Our aim was to determine the role of certain urinary cytokines or antimicrobial proteins, plasma vitamin D level, and genetic variation in host defense of febrile UTI and its relation with bacteremia. METHODS: A case-control study. Out of a cohort of consecutive adults with febrile UTI (n = 787) included in a multi-center observational cohort study, 46 cases with bacteremic E.coli UTI and 45 cases with non-bacteremic E.coli UTI were randomly selected and compared to 46 controls. Urinary IL-6, IL-8, LL37, ß-defensin 2 and uromodulin as well as plasma 25-hydroxyvitamin D were measured. In 440 controls and 707 UTI patients polymorphisms were genotyped in the genes CXCR1, DEFA4, DEFB1, IL6, IL8, MYD88, UMOD, TIRAP, TLR1, TLR2, TLR5 and TNF. RESULTS: IL-6, IL-8, and LL37 are different between controls and UTI patients, although these proteins do not distinguish between patients with and without bacteremia. While uromodulin did not differ between groups, inability to produce uromodulin is more common in patients with bacteremia. Most participants in the study, including the controls, had insufficient vitamin D and, at least in winter, UTI patients have lower vitamin D than controls. Associations were found between the CC genotype of IL6 SNP rs1800795 and occurrence of bacteremia and between TLR5 SNP rs5744168 and protection from UTI. The rare GG genotype of IL6 SNP rs1800795 was associated with higher ß-defensin 2 production. CONCLUSION: Although no biomarker was able to distinguish between UTI with or without bacteremia, two risk factors for bacteremia were identified. These were inability to produce uromodulin and an IL6 rs1800795 genotype.

Hepatorenal dysfunction in sepsis: epidemiological, clinical and laboratory aspects.

UNLABELLED: The major impact of sepsis-induced multiple organ dysfunction on healthcare system in the European Union was estimated at 90.4 cases per 100000 inhabitants, compared to 58 per 100000 for breast cancer. The association of organ dysfunctions in terms of both the number of dysfunctions and the degree of organ dysfunction is the most powerful predictor of death in sepsis. AIM: To find medical and statistical correlations in hepatorenal dysfunction in sepsis patients. MATERIAL AND METHODS: This retrospective study included 117 patients diagnosed with sepsis at the Iasi Infectious Diseases Hospital, patients who presented liver/renal and other organ dysfunctions. The clinical, etiological, and laboratory data, and APACHE II prognostic scores were analyzed. The data were processed using SPSS version 16.0. RESULTS: The etiological agents were Gram positive as well as Gram negative bacteria, and 40% of sepsis patients with hepatic/kidney dysfunction presented hepatorenal syndrome. CONCLUSIONS: Over one-third of patients with sepsis-related hepatorenal dysfunction had a creatinine clearance of less than 30 ml/min, and we found statistical correlations between serum creatinine and APACHE II score. There were no statistically significant differences between the survival curves of patients with hepatorenal syndrome and those with sepsis-related hepatorenal dysfunction.

Streptococcus pneumoniae antigen in urine: diagnostic usefulness and impact on outcome of bacteraemic pneumococcal pneumonia in a large series of adult patients.

BACKGROUND AND OBJECTIVE: Urinary pneumococcal antigen detection provides good results in the diagnosis of pneumococcal pneumonia but has rarely been used in bacteraemic pneumococcal pneumonia and it is not known whether it is associated with outcome in this type of pneumonia. Our objectives were to assess the usefulness of an immunochromatographic technique for detecting the pneumococcal antigen in urine in a large prospective study of patients with bacteraemic pneumococcal pneumonia and explore any potential association with outcomes. METHODS: This study, carried out over 8 years, included all adult immunocompetent patients admitted for bacteraemic pneumococcal pneumonia. An immunochromatographic test for the Streptococcus pneumoniae antigen in urine was performed in the first 24 h. The sensitivity of test was assessed and patients were divided into two groups according to test results to explore differences on admission and during the course of the illness using logistic regression models. RESULTS: Of the 350 patients with bacteraemic pneumococcal pneumonia included, 261 (74.6%) were positive for the antigen. Patient characteristics were very similar on admission and differences in severity (Pneumonia Severity Index) were not statistically significant. In the adjusted analysis, antigen-positive patients had a higher risk of intensive care unit admission, treatment failure and adverse outcome. CONCLUSIONS: The sensitivity of the immunochromatographic urinary antigen test was 74.6% and positive results were associated with poorer clinical outcome. We therefore recommend systematic use of this test when pneumonia is diagnosed in the emergency department.

The bacterial amyloid curli is associated with urinary source bloodstream infection.

Urinary tract infections are the most common cause of E. coli bloodstream infections (BSI) but the mechanism of bloodstream invasion is poorly understood. Some clinical isolates have been observed to shield themselves with extracellular amyloid fibers called curli at physiologic temperature. We hypothesize that curli fiber assembly at 37 °C promotes bacteremic progression by urinary E. coli strains. Curli expression by cultured E. coli isolates from bacteriuric patients in the presence and absence of bacteremia were compared using Western blotting following amyloid fiber disruption with hexafluoroisopropanol. At 37 °C, urinary isolates from bacteremic patients were more likely to express curli than those from non-bacteremic patients [16/22 (73%) vs. 7/21 (33%); p = 0.01]. No significant difference in curli expression was observed at 30 °C [86% (19/22) vs. 76% (16/21); p = 0.5]. Isolates were clonally diverse between patients, indicating that this phenotype is distributed across multiple lineages. Most same-patient urine and blood isolates were highly related, consistent with direct invasion of urinary bacteria into the bloodstream. 37 °C curli expression was associated with bacteremic progression of urinary E. coli isolates in this population. These findings suggest new future diagnostic and virulence-targeting therapeutic approaches.

Metabolic response to Klebsiella pneumoniae infection in an experimental rat model.

Bacteremia, the presence of viable bacteria in the blood stream, is often associated with several clinical conditions. Bacteremia can lead to multiple organ failure if managed incorrectly, which makes providing suitable nutritional support vital for reducing bacteremia-associated mortality. In order to provide such information, we investigated the metabolic consequences of a Klebsiella pneumoniae (K. pneumoniae) infection in vivo by employing a combination of (1)H nuclear magnetic resonance spectroscopy and multivariate data analysis. K. pneumoniae was intravenously infused in rats; urine and plasma samples were collected at different time intervals. We found that K. pneumoniae-induced bacteremia stimulated glycolysis and the tricarboxylic acid cycle and also promoted oxidation of fatty acids and creatine phosphate to facilitate the energy-demanding host response. In addition, K. pneumoniae bacteremia also induced anti-endotoxin, anti-inflammatory and anti-oxidization responses in the host. Furthermore, bacteremia could cause a disturbance in the gut microbiotal functions as suggested by alterations in a range of amines and bacteria-host co-metabolites. Our results suggest that supplementation with glucose and a high-fat and choline-rich diet could ameliorate the burdens associated with bacteremia. Our research provides underlying pathological processes of bacteremia and a better understanding of the clinical and biochemical manifestations of bacteremia.

Development of PCR primers and a DNA macroarray for the simultaneous detection of major Staphylococcus species using groESL gene.

Staphylococcus spp., including S. aureus, S. intermedius, S. hyicus, S. epidermidis, S. saprophyticus, S. haemolyticus, S. xylosus, and S. carnosus, are major bacterial species associated with food poisoning, and human and veterinary clinics. Traditional methods for the identification of these staphylococci are time-consuming, laborious, or inaccurate. Therefore, rapid and accurate diagnostic methods are needed. In this study, we designed the DNA probes and polymerase chain reaction (PCR) primers for the detection of the aforementioned Staphylococcus species. These primers were proved to be specific for the detection of their corresponding target strains. Furthermore, by using a consensus primer pair, we were able to co-amplify the intergenic region of groES-groEL for these staphylococci. Followed by a chromogenic macroarray system with the specific probes on the plastic chips, these staphylococci in milk products or clinical samples could be simultaneously detected. When the system was used for the inspection of milk or urine samples containing N × 10° target cells per milliliter of the sample, all these staphylococcal species could be identified after an 8-h pre-enrichment step. This system also allowed the adequate diagnosis of bacteremia, since N × 10° target cells per milliliter of the blood samples could be detected after a 12-h pre-enrichment. Compared to the multiplex PCR method, this approach has the additional advantage that it allowed the discrimination of more bacterial strains-even some bacterial strains that may generate PCR products with the same molecular sizes.

Urinary tract infections in pediatric oncology patients with fever and neutropenia.

The relevancy of the urinary tract as a source of infection during febrile neutropenia is not known. The authors sought to determine the frequency of urinary tract infections (UTIs) in pediatric cancer patients with febrile neutropenia. Urine was collected from a mid-stream void before the administration of antibiotics. Demographic, clinical, and laboratory data were collected. The frequency of UTI and usefulness of urinalysis and localizing signs in predicting UTI in pediatric cancer patients with fever and neutropenia were determined. Forty-five patients had 58 febrile neutropenic episodes eligible for study participation. No patient presented with localizing signs. The urinalysis was negative in 53 episodes and positive in 5 episodes. Four patients had 5 UTIs. The frequency of UTI was 8.6% (5 of 58 febrile neutropenia episodes). Four patients had bacteremia, none of whom had a UTI. The sensitivity, specificity, and negative predictive value of urinalysis was 40%, 94%, and 94%, respectively, and for localizing signs was undefined, 100%, and 91%, respectively. UTI is as common as bacteremia in the current pediatric cancer patients with fever and neutropenia. Urinalysis and urine culture should be obtained routinely as part of the diagnostic evaluation of patients with fever and neutropenia.

Detection of bacteriuria and bacteremia in newborn calves by a catalase-based urine test.

BACKGROUND: Bacteremia occurs frequently in newborn calves. The predictive value of clinical signs is low, suggesting the use of calf-side diagnostic tests. OBJECTIVES: To investigate testing of urine catalase activity (Uriscreen test) for bacteriuria and bacteremia detection. ANIMALS: Five colostrum-free calves and 3 colostrum-fed control calves. METHODS: Controlled experimental trial. Colostrum-free calves were inoculated PO with Escherichia coli O78+. A clinical score was established to define the onset of the illness. Blood and urine (cystocentesis) samplings and cultures, and Uriscreen tests, were performed 4-6 times from inoculation to death. Three control calves received the same management as 3 inoculated calves, but with colostrum and without inoculation. RESULTS: Bacteremia was demonstrated in all of the inoculated colostrum-free calves and in none of the control calves. The E. coli O78+ strain, E. coli, and Klebsiella spp. were recovered from 4/5, 5/5, and 2/5 inoculated colostrum-free calves, respectively. Urine cultures were negative for the 2 groups at the start of the experiment; 5/5 colostrum-deprived inoculated calves were positive for E. coli thereafter whereas 3/3 controls remained negative. Concordance of Uriscreen tests with bacteremia and bacteriuria was 0.86 and 0.88, respectively. Kappa value of agreement between Uriscreen and bacteremia and bacteriuria was 0.73 and 0.76, respectively. Sensitivity of Uriscreen for bacteremia and bacteriuria was 80.0 and 86.6%, respectively, and specificity was 92.8 and 88.8%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The results suggest that Uriscreen can be used for detection of bacteremia in neonatal calves in connection with a constant bacteriuria.

Successful treatment of daptomycin-nonsusceptible methicillin-resistant Staphylococcus aureus bacteremia with the addition of rifampin to daptomycin.

OBJECTIVE: To report a case in which daptomycin-nonsusceptible methicillin-resistant Staphylococcus aureus (MRSA) bacteremia was successfully treated with the addition of rifampin to daptomycin. CASE SUMMARY: An 84-year-old male presented with fever and chills following cystoscopy. After culturing was conducted, the patient received single doses of vancomycin and gentamicin and then continued on vancomycin plus ceftazidime. Blood cultures grew MRSA, with vancomycin and daptomycin minimum inhibitory concentrations (MICs) of < or =1 microg/mL and 0.25 microg/mL, respectively. Vancomycin was continued, with trough concentrations maintained >15 microg/mL, but results of blood cultures remained positive. On day 10, therapy was switched to daptomycin 6 mg/kg/day, but culture results remained positive. On day 13, testing for vancomycin heteroresistance was negative, with the MIC unchanged. The vancomycin MIC remained unchanged on day 19, but the daptomycin MIC had increased to 2 microg/mL. Rifampin 300 mg orally twice daily was added on day 20; blood cultures obtained 2 days later were sterile. The patient was discharged to complete a 6-week course of antibiotics and was doing well 4 months following therapy. DISCUSSION: Analysis of MRSA isolates obtained on days 1 and 19 showed an increase in the daptomycin MIC from 0.25 to 2 microg/mL. Because intervening isolates were not available for susceptibility testing, it is not possible to associate this increase with exposure to either vancomycin or daptomycin. Although in vitro synergy was not seen in this case, addition of rifampin to daptomycin therapy resolved the bacteremia. CONCLUSIONS: In patients with persistent MRSA bacteremia, isolates should be retested for susceptibility to both daptomycin and vancomycin, including assessment for vancomycin heteroresistance. Addition of rifampin to daptomycin may be effective for persistent MRSA bacteremia, even if daptomycin MICs are elevated. Prospective studies are needed to define the role of combination therapy.

Bacterial overgrowth affects urinary proteome analysis: recommendation for centrifugation, temperature, duration, and the use of preservatives during sample collection.

Bacterial overgrowth is one of the major concerns in collection and storage of biofluids, particularly 24-h urine. However, there is no previous systematic analysis of effects of bacterial overgrowth on urinary proteome analysis, and necessity, type, and appropriate concentration of preservatives to prevent bacterial overgrowth in the urine remain unclear. We, therefore, performed such systematic evaluation. Pooled normal urine was either centrifuged at 1500 g (to remove cell debris) or uncentrifuged. The samples were then added with either sodium azide (NaN3) or boric acid with various concentrations, and kept at room temperature (RT) or at 4 degrees C. Bacterial overgrowth was determined by UV-visible spectrophotometry (lambda620 nm) and Gram staining. At both temperatures, centrifugation to remove cell debris could effectively delay the bacterial overgrowth. At RT, both centrifuged and uncentrifuged samples without any preservative had the detectable overgrowth of Gram-positive and Gram-negative cocci and bacilli as early as 12 and 8 h, respectively, whereas 0.1-1 mM NaN3 and 2-20 mM boric acid could delay bacterial overgrowth, which started at 16-20 h in the centrifuged urine and 12-16 h in the uncentrifuged urine. Greater delay (for at least 48 h) was achieved with 10 mM NaN3 and 200 mM boric acid. At 4 degrees C, no bacterial overgrowth was detected in all centrifuged samples. However, it was observed at 20 h in the uncentrifuged urine without preservative, and at 48 h for the uncentrifuged urine with 0.1 mM NaN3 or 2 mM boric acid. There was no bacterial overgrowth detectable in the uncentrifuged urine preserved with higher concentrations of NaN3 or boric acid. 2-DE showed obvious changes in the urinary proteome profile of the sample with bacterial contamination, and the bacterial proteins could be identified by MALDI-TOF MS. Our data suggest that the urine should be centrifuged to remove cell debris and kept at 4 degrees C, rather than at RT, during the collection interval prior to long-term storage in the freezer. Moreover, the addition of 200 mM boric acid or 10 mM NaN3 is highly recommended for the prevention of bacterial overgrowth in the urine.