Diagnostic Stewardship for Urine Cultures

Urinary tract infections are among the most common infectious diagnoses in health care, but most urinary tract infections are diagnosed inappropriately in patients without signs or symptoms of infection. Asymptomatic bacteriuria leads to inappropriate antibiotic prescribing and negative downstream effects, including antimicrobial resistance, health care-associated infections, and adverse drug events. Diagnostic stewardship is the process of modifying the ordering, performing, or reporting of test results to improve clinical care. Diagnostic stewardship impacts the diagnostic pathway to decrease inappropriate detection and treatment of asymptomatic bacteriuria. This article reviews diagnostic stewardship methods and closes with a case study illustrating these principles in practice.

Effect of preoperative prophylactic antibiotic use on postoperative infection after percutaneous nephrolithotomy in patients with negative urine culture: a single-center randomized controlled trial

PURPOSE

To compare the effects of different preoperative antibiotic prophylaxis (ABP) regimens on the incidence of sepsis after percutaneous nephrolithotomy (PCNL) in patients with negative urine culture.

METHODS

A single-center, randomized controlled trial (June 2022-December 2023) included 120 patients with negative preoperative urine cultures for upper urinary tract stones who underwent PCNL (chictr.org.cn; ChiCTR2200059047). The experimental group and the control group were respectively given different levofloxacin-based preoperative ABP regimes, including 3 days before surgery and no ABP before surgery. Both groups were given a dose of antibiotics before the operation. The primary outcome was differences in the incidence of postoperative sepsis.

RESULTS

A total of 120 subjects were included, including 60 patients in the experimental group and 60 patients in the control group. The baseline characteristics of the two groups were comparable and intraoperative characteristics also did not differ. The sepsis rate was not statistically different between the experimental and control groups (13.3% vs.13.3%, P = 1.0). A multivariate logistic regression analysis revealed that body mass index (BMI) (OR = 1.3; 95% CI = 1.1-1.6; P = 0.003) and operating time (OR = 1.1; 95% CI = 1.0-1.1; P = 0.012) were independent risk factors of sepsis.

CONCLUSION

Our study showed that prophylactic antibiotic administration for 3 days before surgery did not reduce the incidence of postoperative sepsis in patients with negative urine cultures undergoing PCNL. For this subset of patients, we recommend that a single dose of antibiotics be given prior to the commencement of surgery seems adequate.

The incidence of nosocomial bloodstream infection and urinary tract infection in Australian hospitals before and during the COVID-19 pandemic: an interrupted time series study

BACKGROUND

The COVID-19 pandemic has had a significant impact on healthcare including increased awareness of infection prevention and control (IPC). The aim of this study was to explore if the heightened awareness of IPC measures implemented in response to the pandemic influenced the rates of healthcare associated infections (HAI) using positive bloodstream and urine cultures as a proxy measure.

METHODS

A 3 year retrospective review of laboratory data from 5 hospitals (4 acute public, 1 private) from two states in Australia was undertaken. Monthly positive bloodstream culture data and urinary culture data were collected from January 2017 to March 2021. Occupied bed days (OBDs) were used to generate monthly HAI incidence per 10,000 OBDs. An interrupted time series analysis was undertaken to compare incidence pre and post February 2020 (the pre COVID-19 cohort and the COVID-19 cohort respectively). A HAI was assumed if positive cultures were obtained 48 h after admission and met other criteria.

RESULTS

A total of 1,988 bloodstream and 7,697 urine positive cultures were identified. The unadjusted incident rate was 25.5 /10,000 OBDs in the pre-COVID-19 cohort, and 25.1/10,000 OBDs in the COVID-19 cohort. The overall rate of HAI aggregated for all sites did not differ significantly between the two periods. The two hospitals in one state which experienced an earlier and larger outbreak demonstrated a significant downward trend in the COVID-19 cohort (p = 0.011).

CONCLUSION

These mixed findings reflect the uncertainty of the effect the pandemic has had on HAI's. Factors to consider in this analysis include local epidemiology, differences between public and private sector facilities, changes in patient populations and profiles between hospitals, and timing of enhanced IPC interventions. Future studies which factor in these differences may provide further insight on the effect of COVID-19 on HAIs.

The data and the reality: urine cultures and emergency medicine physicians

BACKGROUND AND OBJECTIVES

The IDSA has published guidelines for the treatment of urinary tract infections, recommending limiting treatment to symptomatic patients and pregnant females. Our objective is to elucidate current practice patterns among emergency physicians (EPs) in treating positive urine cultures in various clinical situations.

METHODS

This study employed a cross-sectional design utilizing a questionnaire addressing nine common scenarios encountered by EPs in the follow-up of a positive urine culture. The questionnaire was conducted using RedCap and distributed via email to current and former physicians and residents across our hospital network. Demographic information included years of training and practice setting. For each of nine clinical scenarios, Physicians were asked if they would treat with antibiotics. Results were then analyzed by tabulating percentage of responses and 95% confidence intervals.

RESULTS

Of 120 respondents, 40.8% worked in academic centers with emergency medicine residencies, 37.5% in large community hospitals, and 20.67% in small community hospitals. Responses came from 14 residents, 33 attendings < 5 years out of training, 23 attendings 5-9 years out of training, 37 attendings 10-20 years out of training, and 13 attendings > 20 beyond training. Asymptomatic young women were treated by 34.2% (95% CI 25.91-43.46%) while asymptomatic elderly women were treated by 50% (95% CI 40.79-59.21%) of EPs. All EPs (95% CI 96.13-100%) chose to treat a symptomatic male and 99.2% (95% CI 94.77-99.96%) chose to treat an asymptomatic pregnant female. Elderly females after a fall were treated by 63.3% (95% CI 54-71.8%) of EPs while elderly males with confusion and a fall were treated by 96.7% (95% CI 91.18-98.93%). Asymptomatic males with a chronic Foley catheter were treated by 28.2% (95% CI 20.67-37.4%) of EPs and 46.7% (95%CI 37.59-55.97%) would treat an asymptomatic middle-aged female with diabetes. Finally, 92.5% (95% CI 85.85-96.3%) of EPs chose to treat an asymptomatic kidney transplant patient.

CONCLUSION

EPs in varied training stages and practice settings have significant practice variation in the treatment of positive urine cultures, particularly in the geriatric population, often prescribing antibiotics to patients where clear, specific and data-driven IDSA guidelines suggest treatment is unnecessary and potentially harmful.

The effect of urine storage temperature and boric acid preservation on quantitative bacterial culture for diagnosing canine urinary tract infection

BACKGROUND

Quantitative bacterial culture (QBC) is the gold standard for diagnosing canine urinary tract infection. Current guidelines recommend QBC within 24 h of urine collection and that unpreserved urine is refrigerated until culture. However, temperature-controlled transport is rarely feasible, indicating a need for alternative storage during transport of urine from primary veterinary practices to the microbiology laboratory. The objective was to investigate the effect of storage temperature and boric acid sponge-preservation on quantitative bacterial culture of canine urine.

RESULTS

Significant bacteriuria was detected in 72 out of 179 samples (40%) collected from 141 dogs. Overall accuracy was 94-98% for both storage conditions and time points. Non-inferiority (15% margin) to reference quantitative bacterial culture was evident for sensitivity, specificity and predictive values for both storage methods and time points, except for the negative predictive value for 48 h boric acid preservation (NPV: 89, 95% CI [79;95]). There was no significant difference between the sensitivity and specificity for either of the time-points (p-value = 0.07-1).

CONCLUSIONS

Boric acid sponge-preservation using Uriswab™ is a useful alternative to refrigeration of urine samples during transport. Reliable quantitative bacterial culture results can be obtained from canine urine up to 48 h after collection if urine is refrigerated, and for at least 24 h if urine is stored using a boric acid-containing urine transport system.

Urine cultures in a long-term care facility (LTCF): time for improvement

Background

Urinary tract infections (UTIs) are the most prevalent infections in long-term care facilities (LTCFs). Numerous studies have described the problem of inadequate UTI diagnosis and treatment. We assessed the role of urine cultures in the diagnosis and treatment of UTIs in a LTCF.

Methods

In a 370-bed non-academic LTCF a retrospective assessment of antibiotic (AB) prescriptions for UTIs and urine cultures was performed from July 2014 to January 2016. The reasons why physicians, including 11 nursing home physicians and 2 junior doctors, ordered urine cultures were recorded using questionnaires.

Results

During the study period, 378 residents were prescribed 1672 AB courses; 803 were for UTIs. One hundred and fifty-five urine cultures were obtained from 135 residents; 66 of these cultures were performed on the same day as ABs were prescribed (8% of all prescriptions for UTI), while 89 were not. There was a discrepancy between the actions that seemed logical based on the culture results and the actions that were actually taken in 75% of the cases. In these cases, initial AB treatment was not adjusted when the isolated microorganism was resistant to the AB prescribed, the urine culture was positive and no ABs had previously been administered, or ABs were prescribed and no microorganism was isolated.

The most frequent reason for ordering a urine culture was to confirm the diagnosis of a UTI.

Conclusion

In the majority of patients, AB therapy was not adjusted when the urine culture results suggested it may be appropriate. The physicians were erroneously convinced that UTIs could be diagnosed by a positive urine culture.

Electronic supplementary material

The online version of this article (10.1186/s12877-018-0909-x) contains supplementary material, which is available to authorized users.

Multicenter Evaluation of an Image Analysis Device (APAS): Comparison Between Digital Image and Traditional Plate Reading Using Urine Cultures

BACKGROUND

The application of image analysis technologies for the interpretation of microbiological cultures is evolving rapidly. The primary aim of this study was to establish whether the image analysis system named Automated Plate Assessment System (APAS; LBT Innovations Ltd., Australia) could be applied to screen urine cultures. A secondary aim was to evaluate differences between traditional plate reading (TPR) and the reading of cultures from images, or digital plate reading (DPR).

METHODS

A total of 9,224 urine samples submitted for culture to three clinical laboratories, two in Australia and one in the USA, were included in the study. Cultures were prepared on sheep blood and MacConkey agar plates and read by panels of three microbiologists. The plates were then presented to APAS for image capture and analysis, and the images and results were stored for later review.

RESULTS

Image analysis of cultures using APAS produced a diagnostic sensitivity and specificity of 99.0% and 84.5%, respectively. Colonies were detected by APAS on 99.0% of blood agar plates with growth and on 99.5% of MacConkey agar plates. DPR agreed with TPR for colony enumeration on 92.1% of the plates, with a sensitivity of 90.8% and specificity of 92.8% for case designation. However, several differences in the classification of colony morphologies using DPR were identified.

CONCLUSIONS

APAS was shown to be a reliable screening system for urine cultures. The study also showed acceptable concordance between DPR and TPR for colony detection, enumeration, and case designation.

How and when nurses collect urine cultures on catheterized patients: A survey of 5 hospitals

BACKGROUND

Obtaining a specimen for urine culture is a key element in evaluating for catheter-associated urinary tract infections (CAUTIs). Evaluating nurses' knowledge regarding appropriate reasons and methods to obtain urine culture specimens are the first steps to improving practice.

METHODS

Nurses at 5 hospitals completed a 40-question survey regarding their knowledge, training, and practices of appropriate reasons for obtaining urine cultures. The survey included different scenarios of patients with urinary catheters and when they would expect to obtain urine cultures. A 12-point scoring system calculated responses regarding urine collection appropriateness.

RESULTS

There were 394 nurses who responded to the survey. Of them, 76.1% reported receiving education on CAUTI risk reduction within the last 12 months. Although 327 (83%) of all nurses surveyed reported that they never collect urine samples by draining directly from the drainage bag, only 58.4% viewed others to be fully compliant with that standard (P < .001). Nurses who considered their knowledge to be above average to excellent had similar knowledge assessment scores (out of 12 points) for triggers to obtain urine cultures (mean score, 4.9 ± 1.72) compared with those that reported average to poor knowledge (mean score, 4.64 ± 1.78; P = .15).

CONCLUSIONS

Important opportunities exist for nurses to optimize the decisions to obtain urine cultures and the process for obtaining them. Addressing nurses' knowledge and practice may lead to more appropriate use of urine cultures.

Laboratory turnaround times in response to an abrupt increase in specimen testing after a natural disaster

OBJECTIVES

Understanding how key indicators change during extreme circumstances could help laboratories maintain high standards when responding to disasters. We assessed the effects of an earthquake on turnaround times (TATs) at a hospital laboratory.

METHODS

We examined TATs for 709,786 potassium tests and 196,795 urine cultures from February 2010 to January 2013. Hospital and community data were evaluated separately and compared during the transport, registration (accessioning), and analysis time phases.

RESULTS

After the earthquake, the laboratory undertook approximately 70% of the nonacute community specimen testing. Initially, community transport times increased by 20 to 27 hours and remained 2 to 3 hours above prequake levels. Registration time increased by 10 to 20 minutes (hospital) and 30 to 45 minutes (community) for a short period. During the initial few months, community urine culture analysis time increased by more than 50 hours.

CONCLUSIONS

The increase in specimen numbers affected short- and long-duration test TATs differently. Streamlining and automating processes reduced registration and analysis times. Increased transport time was outside the control of the laboratory.

Bacteriuria and antibiotic resistance in catheter urine specimens following radical prostatectomy

OBJECTIVE

There are increasing reports of infectious complications following prostate biopsy due to fluoroquinolone resistance. To determine infectious complications at catheter removal following radical prostatectomy (RP), another setting in daily urological practice where fluoroquinolone prophylaxis is frequently used.

MATERIALS AND METHODS

We prospectively examined urine culture results collected from 334 RP patients immediately prior to catheter removal. Patients received prophylactic antibiotics 1 day before, the day of, and for 5 days after catheter removal. Culture results were reviewed for bacterial species and antimicrobial susceptibilities. Patients with positive urine cultures resistant to the prophylactic antibiotic were switched to culture-specific antibiotic therapy and underwent follow-up culture. The frequency of urinary tract infection (UTI), complications, additional antibiotic therapy, and repeat urine cultures was determined within 60 days.

RESULTS

Of the 334 patients identified, 203 (61%) had cultures with no bacterial growth, and 48 (14%) had colony counts of <1,000 bacteria or Candida albicans and received no further antibiotics. The remaining 83 (25%) had positive culture results, of which 7% were resistant to ciprofloxacin. Twenty-four bacterial species were identified, with Pseudomonas aeruginosa (5%) Escherichia coli (4%), and Staphylococcus epidermidis (3%) being the most frequent. Only two (0.6%) men developed clinical symptoms consistent with UTI (i.e., suprapubic pain, fever) prior to catheter removal, and no serious complications occurred.

CONCLUSIONS

A substantial proportion of RP patients have positive urine cultures at the time of catheter removal, despite the administration of prophylactic fluoroquinolone antibiotics. Potentially virulent organisms are commonly cultured, and ciprofloxacin resistance is frequent. However, outcomes are favorable when culture-specific oral antibiotic therapy is initiated.