False-positive Cultures Research Articles

Blood Culture Contamination Mitigation: Sustaining Success and Stewardship Systemwide

Background: False-positive blood cultures compromise care; extended stays, Clostridioides difficile risk increases and renal woes tagged to antibiotic alms contribute to the doubling of patient in-hospital mortality that is observed relative to true negative diagnostic results. False-positive affiliated central line-associated bloodstream infection reports can further obfuscate the quality of care provided. Between personnel performance pressures, laboratory resource losses and the risk for financial penalty under Value-Based Purchasing and Hospital-Acquired Condition Reduction Programs (Centers for Medicare & Medicaid Services), it becomes difficult to brush aside the burden of a non-zero blood culture contamination rate. Following unsuccessful and unsustainable endeavors that included educational exercise and waste tube employment, initial-specimen diversion devices designed to shift performance burdens from technicians to technology were co-opted in an effort to secure reliable blood culture contamination rate reductions. Methods: A 3.6% blood culture contamination rate was observed systemwide prior to intervention, which began in 2020. Among seventeen facilities that share a data system, twelve co-opted initial-specimen diversion device technology as the evidence-based anchor to a trifurcate intervention strategy that included value analysis and cultural curation. Results: The 2023 systemwide blood culture contamination rate was 1.95%; down from 2.8% in 2022 and 3.2% in 2021. The average cost per false-positive event was $2,111, with intervention amounting to systemwide savings of $4.1 million in 2023 as approximately 1,920 patients avoided false-positive incidents. Critical to year-over-year systemwide uptick in adoption of interventive technology was consistent and near real-time communication to caretakers regarding outcomes. Conclusion: The sustained success of the multifactorial solution showcased herein stems from the coupling of an evidence-based action with an ongoing assessment of value and communication channels carefully constructed to celebrate and perpetuate value observed. Layered uncertainties often cloud the crux of a multifactorial solution to a complex conundrum; for many decades the literature-supported solution to high blood culture contamination rates was to educate every person involved in every possible way. Only recently, following recommended practice revisions endorsed by the Clinical and Laboratory Standards Institute and Centers for Disease Control and Prevention, did it become apparent nationwide that education alone was insufficient; some contaminant pathways persist without meticulously mechanical closure. Antimicrobial stewardship requires the respectful removal of adaptable pressures from microorganisms, but the inverse is equally important; by setting an ambitious systemwide blood culture contamination rate target of 1% or less, it is hoped that all facilities involved herein respond to this pressure with optimism, introspection and innovation.

The False-Positive Rate of Synovial Fluid Culture at a Single Clinical Laboratory Using Culture Bottles.

Introduction Synovial fluid (SF) cultures can yield false-positive or negative results when diagnosing periprosthetic joint infection (PJI). False-positives may arise during sample collection or from laboratory contamination. Understanding false-positive SF culture rates is crucial for interpreting PJI laboratory data, yet clinical laboratories rarely report these rates. This study aimed to define the false-positive SF culture rate at a major specialized clinical laboratory. Methods This study retrospectively analyzed prospectively collected data at a single clinical laboratory that receives SF for clinical testing for PJI. A total of 180,317 periprosthetic SF samples from the hip, knee, and shoulder were identified from January 2016 to December 2023, which met the inclusion criteria for this study. Samples were classified by both a modified 2018 International Consensus Meeting (ICM) score and an inflammation score that combined the SF-C-reactive protein, alpha-defensin, SF-white blood cell count, and SF-polymorphonuclear% into one standardized metric. Logistic regression was utilized to evaluate the impact of various collection-based characteristics on culture positivity, including inflammation biomarkers, the source joint, quality control metrics, and days of specimen transport to the laboratory. SF culture false-positivity was calculated based on the ICM category of "not-infected" or low inflammation score. Results Overall, 13.3% (23,974/180,317) of the samples were associated with a positive culture result: 12.5% for knee samples, 20.3% for hip samples, and 14.7% for shoulder samples. The false-positive SF culture rate among 131,949 samples classified as "not-infected" by the modified 2018 ICM definition was 0.47% (95%CI: 0.43 to 0.51%). Stratification by joint revealed a false-positive rate of 0.34% (95%CI: 0.31 to 0.38%) for knee samples, 1.24% (95%CI: 1.05 to 1.45%) for hip samples, and 3.02% (95%CI: 2.40 to 3.80%) for shoulder samples, with p < 0.0001 for all comparisons. The false-positive SF culture rate among 90,156 samples, representing half of all samples with the lowest standardized inflammation scores, was 0.47% (95%CI: 0.43 to 0.52%). Stratification by joint revealed a false-positive rate of 0.33% (95%CI: 0.29 to 0.37%) for knee samples, 1.45% (95%CI: 1.19 to 1.77%) for hip samples, and 3.09% (95%CI: 2.41 to 3.95%) for shoulder samples, with p<0.0001 for all comparisons. Multivariate logistic regression demonstrated the joint source (hip, shoulder) and poor sample quality as collection-based factors associated with a false-positive culture. Evaluation of a cohort of samples selected to minimize collection-based causes of false-positive culture demonstrated a false-positive rate of 0.30%, representing the ceiling limit for laboratory-based SF culture false-positivity. Conclusions This study utilizes two methods to estimate the false-positive SF culture rate at a single specialized clinical laboratory, demonstrating an overall false-positive rate of approximately 0.5%. Stratification of samples by source joint demonstrated that periprosthetic SF from the shoulder and hip have a substantially higher false-positive culture rate than that of the knee. The lowest false-positive SF culture rate (0.30%) was observed among samples from the knee-passing quality control. Culture positivity due to contamination at this specific laboratory is less than 0.30% because all specimens undergo identical processing.

The operational and financial impact of adding anaerobic screening of platelets.

We evaluated the operational and safety impact of implementing anaerobic culture screening of apheresis and pooled platelets at the American Red Cross on the already established use of the aerobic culture screening of each donation performed no sooner than 24 h following collection. Platelets were screened for bacterial contamination with the BACT/ALERT 3D® (bioMérieux, Durham, NC) microbial detection testing system. The addition of anaerobic culture to the already existing aerobic culture resulted in sampling an additional 8-10 mL from each donation. Implementation of anaerobic testing resulted in an approximate 3.5-fold increased rate of False Positive BACT/ALERT alarms. There was a modest increase in the rate of True Positive alarms of 1.4-fold with increased detection of Klebsiella and Propionibacterium species, including Cutibacterium acnes. In addition, there was an approximate 3.5-fold increase rate of False Positives and a 13.5-fold increase rate of Indeterminates, the majority (~57%) were due to Cutibacterium acnes. The combined costs and lost revenue associated with adding anaerobic screening increased by ~$1,000,000/year due to testing cost and product discards. The addition of anaerobic culture to aerobic culture to the original donation (without the introduction of sampling delay) resulted in a significant increase in the rate of alerts. The 40% increased rate of True Positive alarms may have modestly improved platelet safety. However, there was a disproportionate increase in the rate of False Positive and Indeterminate bacterial culture alarms, which added substantial cost and overall loss of platelet products.

The impact of the COVID-19 pandemic on blood culture practices and bloodstream infections.

Bacterial infections are a significant cause of morbidity and mortality worldwide. In the wake of the COVID-19 pandemic, previous studies have demonstrated pandemic-related shifts in the epidemiology of bacterial bloodstream infections (BSIs) in the general population and in specific hospital systems. Our study uses a large, comprehensive data set stratified by setting [community, long-term care (LTC), and hospital] to uniquely demonstrate how the effect of the COVID-19 pandemic on BSIs and testing practices varies by healthcare setting. We showed that, while the number of false-positive blood culture results generally increased during the pandemic, this effect did not apply to hospitalized patients. We also found that many infections were likely under-recognized in patients in the community and in LTC, demonstrating the importance of maintaining healthcare for these groups during crises. Last, we found a decrease in infections caused by certain pathogens in the community, suggesting some secondary benefits of pandemic-related public health measures.

Non-touch treatment to solve the persistent contamination of culture plates with Aspergillus niger in a clinical microbiology laboratory of Spain.

A pseudo-outbreak of Aspergillus caused by false positive cultures can have a high sanitary impact. We determined the effectiveness (fungal load elimination) of a non-touch disinfection system, vs conventional disinfection methods, to solve steady contamination of culture plates with Aspergillus niger at a clinical microbiology laboratory. Routine cleaning-disinfection (RCD), intensive cleaning-disinfection (ICD), and terminal airborne disinfection (TAD) were employed in stages. Air sampling was carried out before and after each procedure. The effectiveness of TAD on contact surfaces was tested by surface sampling. After RCD, ICD, and TAD, there was a mean decrease of 5.4 (95% CI = 1.8-9.0), 19.2 (95% CI = 12.4-26.0), and 4.4 (95% CI = 2.5-6.3) CFU per tested area, and 46.2%, 21.7%, and 95.5% of contaminated areas became sterile, respectively. There was a mean decrease of 30.6CFU per tested surface (p < 0.0007) and 50% of tested surfaces became sterile. Global effectiveness of RCD, ICD, and TAD was 68.8% (95% CI = 68.5-69.1), 82.2% (95% CI = 82.1-82.3), and 99.0% (95% CI = 98.8-99.2), respectively. The effectiveness was higher with TAD (4.1CFU/cm2 less than with ICD; p = 0.0290). No further contamination has occurred since then. When construction and renovation activities are discarded and RCD and ICD practices are insufficient, non-touch disinfection remove residual dust contamination and avoid recurrence.

Evaluating the Proportion of Low-Value Blood Cultures Obtained in a Pediatric Emergency Department.

Existing literature suggests that for some pediatric conditions, blood cultures may be of low value in specific clinical circumstances. The goals of our study were to: 1) identify common pediatric illnesses and define criteria for low-value blood cultures in children aged from 91 days to 19 years, 2) apply these criteria retrospectively to identify the patients in our emergency department (ED) who had low-value blood cultures obtained, and 3) describe this cohort and assess the proportion of true bacteremia in low-value blood cultures. The study team reviewed the literature and developed consensus criteria to identify conditions in which blood cultures were of low value for our study population. The criteria were applied retrospectively to well-appearing patients aged from 91 days to 19 years, without a central venous catheter, and evaluated in our ED with a peripheral blood culture from June 2018 to April 2020. Children admitted to the intensive care/hematology-oncology/cardiology/pulmonary units, those transferred from our ED to an outside facility, who transferred to our ED due to a positive blood culture from an outside facility, and repeat visits of a patient within 30 days from a previous visit were excluded from the study. After chart review, children with fever for 7 days or more, who were unvaccinated, immunosuppressed, had implanted devices, had a complex medical history, or had provider concerns for bacteremia/sepsis were excluded. The study population consisted of 1436 children. Children at risk for bacteremia (n = 718) were excluded. Four hundred twenty-four children had discharge diagnoses not included in our study. There were 294 (20.5%) patients who had low-value cultures per our study criteria. Nine children (9/294, 3.1%) had false-positive blood cultures, and three (3/294, 1.0%) had true-positive blood cultures. We identified a cohort of patients in our ED with blood cultures obtained when available literature indicates they were of low value.

Mitigating Concerns Over Transport Delays: An Analysis of Synovial Fluid Culture Results in Arthroplasty.

There is a concern in the field of arthroplasty that synovial fluid transport delays may reduce the accuracy of synovial fluid culture. However, synovial fluid samples collected in the office, and sometimes in a hospital setting, often require transport to a third-party central or specialty laboratory, causing delays in the initiation of culture incubation. This study investigated the impact of transportation delays on synovial fluid culture results. A retrospective review of prospectively collected data at one clinical laboratory, from 2016 to 2022, was conducted. A total of 125,270 synovial fluid samples from knee arthroplasties, from 2,858 different US institutions, were transported to a single clinical laboratory for diagnostic testing including synovial fluid culture (blood culture bottles). Synovial fluid to be cultured was transported in red top tubes without additives.Samples were grouped into six-time cohorts based on the number of days between aspiration and culture initiation (1-day-delay to 6-day-delay). Metrics such as culture positivity, false-positive culture rate, culture sensitivity, and proportional growth of top genera of organisms were assessed across the cohorts. Of the 125,270 samples in this study, 71.2% were received the day after aspiration (1-day-delay), with an exponential decrease in samples received on each subsequent day.Culture-positive rates for synovial fluid samples received after 1, 2, 3, 4, 5, and 6 days of transport time were 12.2%, 13.3%, 13.5%, 13.1%, 11.6%, and 11.0%, respectively. The maximum absolute difference in culture-positive rate compared to the 1-day-delay cohort was an increase of 1.3% in the 3-day-delay cohort, which was not considered a clinically meaningful difference. The estimated false-positive culture rate remained relatively consistent across time cohorts, with values of 0.3%, 0.4%, 0.3%, 0.2%, 0.5%, and 0.5% for 1, 2, 3, 4, 5, and 6 days of transport time, respectively. None of the cohorts showed a statistically significant difference after adjustment for multiplicity compared to the 1-day-delay cohort.Culture sensitivity was estimated at 68.2%, 67.2%, 70.5%, 70.7%, 65.9%, and 70.7% for 1, 2, 3, 4, 5, and 6 days of transport time, respectively. None of the cohorts showed a statistically significant difference after adjustment for multiplicity compared to the 1-day-delay cohort.Organism proportions were consistent across time cohorts, with Staphylococcus being the most commonly identified organism. No statistically significant differences were found in the proportional contribution of major genera across the cohorts. Synovial fluid culture exhibited surprisingly consistent results despite variable transport time to the destination laboratory, with differences that have minimal clinical importance. While the authors of this study advocate for short transport times as a best practice to expedite diagnosis, it appears that concerns regarding the rapid degradation of culture results due to synovial fluid transportation is unwarranted.

Manual Homogenization Improves the Sensitivity of Microbiological Culture for Patients with Pyogenic Spondylitis.

This study aimed to investigate the effects of manual homogenization on the sensitivity of microbiological culture for patients with pyogenic spondylitis. From October 2018 to March 2021, patients undergoing fluoroscopy-guided biopsy or open debridement due to pyogenic spondylitis were recruited. Their demographic data and baseline characteristics were recorded. Tissue samples were obtained through fluoroscopy-guided biopsy or open debridement. Tissue samples were divided into three parts: manual homogenization (MH), manual mixture (MM), and pathological examination. Sterile normal saline was set as the negative control to exclude false-positive culture results. The Chi-square test was used to detect the difference of microbiological culture results. Twenty-four consecutive patients (33 tissue cultures) with pyogenic spondylitis treated in our department between October 2018 and March 2021 were recruited in this study. The average age was 61.7±3.2 years old and 10 patients were female. The MH group had a significantly higher positive rate compared with the MM group in aerobic conditions: 78.8% (26 isolates) vs 54.5% (18 isolates), P=0.037 and anaerobic condition: 63.6% (21 isolates) vs 39.4% (13 isolates), P=0.049. The results of subgroup analyses showed that MH could improve the culture sensitivity for patients with previous antibiotics use and without paravertebral abscesses but not reach a significant level on statistics. Based on the present study, manual homogenization could improve the sensitivity of microbiological cultures for patients with pyogenic spondylitis.

Factors affecting blood culture contamination rates and effective reduction measures

Blood culture collection is a crucial procedure used universally in hospital settings to identify bloodstream infections. A false positive culture arises when contamination occurs during culture collection or when handling the culture in the laboratory. These contaminated cultures cause inaccurate diagnoses resulting in longer hospital stays, increased cost, and unnecessary antimicrobial treatments. It is therefore vital to limit the rate of blood culture contamination. Here we discuss various factors that play roles in blood culture contamination rates. The roles of phlebotomy teams, the coronavirus disease 2019 pandemic, blood draw location, and hospital department on blood culture contamination rates will be discussed. Potential methods that can be deployed to decrease blood culture contamination rates will be compared.

What do positive and negative Cutibacterium culture results in periprosthetic shoulder infection mean? A multi-institutional control study.

Deep tissue culture specimens obtained at the time of revision shoulder arthroplasty are commonly positive for Cutibacterium. Clinical interpretation of positive cultures can be difficult. This was a multi-institutional study evaluating the accuracy of cultures for Cutibacterium using positive control (PC) and negative control (NC) samples. The relationship between time to culture positivity and strength of culture positivity was also studied. Eleven different institutions were each sent 12 blinded samples (10 PC and 2 NC samples). The 10 PC samples included 2 sets of 5 different dilutions of a Cutibacterium isolate from a failed total shoulder arthroplasty with a probable periprosthetic infection. At each institution, the samples were handled as if they were received from the operating room. Specimen growth, time to culture positivity, and strength of culture positivity (based on semiquantitative assessment) were reported. A total of 110 PC samples and 22 NC samples were tested. One hundred percent of specimens at the 4 highest dilutions were positive for Cutibacterium. At the lowest dilution, 91% of samples showed positive findings. Cutibacterium grew in 14% of NC samples. Cutibacterium grew in PC samples at an average of 4.0±1.3 days, and all of these samples showed growth within 7 days. The time to positivity was significantly shorter (P<.001) and the strength of positivity was significantly higher (P<.001) in true-positive cultures compared with false-positive cultures. This multi-institutional study suggests that different institutions may report highly consistent rates of culture positivity for revision shoulder arthroplasty samples with higher bacterial loads. In contrast, with lower bacterial loads, the results are somewhat less consistent. Clinicians should consider using a shorter time to positivity and a higher strength of positivity as adjuncts in determining whether a tissue culture sample is a true positive.

Diagnostic stewardship for blood cultures in the emergency department: A multicenter validation and prospective evaluation of a machine learning prediction tool.

SummaryBackgroundOveruse of blood cultures (BCs) in emergency departments (EDs) leads to low yields and high numbers of contaminated cultures, accompanied by increased diagnostics, antibiotic usage, prolonged hospitalization, and mortality. We aimed to simplify and validate a recently developed machine learning model to help safely withhold BC testing in low-risk patients.MethodsWe extracted data from the electronic health records (EHR) for 44.123 unique ED visits with BC sampling in the Amsterdam UMC (locations VUMC and AMC; the Netherlands), Zaans Medical Center (ZMC; the Netherlands), and Beth Israel Deaconess Medical Center (BIDMC; United States) in periods between 2011 and 2021. We trained a machine learning model on the VUMC data to predict blood culture outcomes and validated it in the AMC, ZMC, and BIDMC with subsequent real-time prospective evaluation in the VUMC.FindingsThe model had an Area Under the Receiver Operating Characteristics curve (AUROC) of 0.81 (95%-CI = 0.78–0.83) in the VUMC test set. The most important predictors were temperature, creatinine, and C-reactive protein. The AUROCs in the validation cohorts were 0.80 (AMC; 0.78–0.82), 0.76 (ZMC; 0.74–0.78), and 0.75 (BIDMC; 0.74–0.76). During real-time prospective evaluation in the EHR of the VUMC, it reached an AUROC of 0.76 (0.71–0.81) among 590 patients with BC draws in the ED. The prospective evaluation showed that the model can be used to safely withhold blood culture analyses in at least 30% of patients in the ED.InterpretationWe developed a machine learning model to predict blood culture outcomes in the ED, which retained its performance during external validation and real-time prospective evaluation. Our model can identify patients at low risk of having a positive blood culture. Using the model in practice can significantly reduce the number of blood culture analyses and thus avoid the hidden costs of false-positive culture results.FundingThis research project was funded by the Amsterdam Public Health – Quality of Care program and the Dutch “Doen of Laten” project (project number: 839205002).

Assessment of Factors Influencing the Positivity of Blood Culture by BacT/ALERT®3D Microbial Detection System: A Cross-sectional Observational Study

Introduction: Bloodstream Infections (BSI) are defined as the presence of living microorganisms in the blood. It is a systemic condition that can result in life-threatening sepsis, thus leading to high morbidity and mortality. Blood cultures have become critically important. Positive blood culture results can help a clinician’s early diagnosis and start empirical antimicrobial at the correct time. Today many laboratories use modern, automated, continuous-monitoring blood culture systems for the detection of bacterial growth for blood culture. At our hospital, blood culture is done by using automated detection in BacT/Alert instrument (Biomerieux, France). Aim: To determine the effect of a number of blood cultures and volume of blood on positivity rates, contamination rate in blood cultures, and rate of false-positive blood cultures. Materials and Methods: Present study was a cross-sectional observational study conducted from 1st May 2019 to 31st July 2019. Blood culture requests of all patients were included in the study. All blood culture bottles were processed as per standard laboratory protocols. The effect of a number of blood cultures and amount of blood volume on positivity rate, contamination rate, and false-positive blood cultures were studied in detail. The patient’s details and microbiological result parameters were extracted from Laboratory Information System (LIS). All the data was analysed in Microsoft Excel 2010. Results: A total of 761 blood culture bottles were received at the Microbiology laboratory from 604 patients. Maximum (30%) blood cultures were received from 0-10 years of age group. A total of 31% (236/761) of blood cultures were positive. The true pathogen positivity rate was 41.1% and the contamination rate was 58.9%. Single (74.4%) blood culture requests were more than two (25.3%) or three (0.3%) blood cultures. True pathogens were isolated in 9% (41/449) of single blood cultures and in 18% (56/306) of two blood cultures. Overall, 42% of blood cultures had adequate volume and 58% of blood cultures had inadequate volume. However, the true pathogen positivity rate was 14% (61/444) from bottles with inadequate volume and 11% (36/317) from bottles with adequate volume. Out of 236 positive blood cultures, 139 (59%) were identified as contaminants. A total of 5/761 (0.7%) blood cultures were identified as false positive blood cultures. Conclusion: Based on the study findings, a step should be taken to discourage single blood culture and to encourage multiple blood cultures for the diagnosis and better patient care. Although, volume of blood is important, inadequate volume did not affect true pathogen positivity rate in present study. Contamination rate of blood cultures is a major concern and regular training of the concerned staff regarding strict asepsis should be implemented.

Patient-specific risk factors contributing to blood culture contamination.

Contaminated blood cultures result in extended hospital stays and unnecessary antibiotic therapy. Patient-specific factors associated with blood culture contamination remain largely unexplored. Identifying patients at higher risk of blood culture contamination could alert healthcare providers to take extra precautionary measures to limit contamination in these patients, and thereby prevent associated adverse outcomes. We sought to identify patient-related factors that contribute to blood culture contamination in hospitalized patients. We conducted a secondary data analysis of a retrospective cohort study at an academic medical center. Study participants included 19,255 adult patients who had blood culture(s) performed during a hospital admission between June 2014 and December 2016. Data were analyzed to evaluate risk factors for blood culture contamination using logistic regression. Among adult patients, we identified 464 contaminated episodes and 11,010 negative blood-culture episodes. Chronic obstructive pulmonary disease (adjusted odds ratio [AOR], 1.67; 95% confidence interval [CI], 1.20-2.34) and stay in an intensive care unit (ICU) during an admission (AOR, 1.41; 95% CI, 1.14-1.74) were associated with blood culture contamination. Other risk factors included race, body mass index, and admission from the emergency department. Subgroup analyses of patients admitted from the emergency department showed similar results. We identified patient-specific factors that increase the odds of false-positive blood cultures. By introducing mitigation strategies to limit contamination in patients with these risk factors, it may be possible to reduce the adverse clinical impact of blood culture contamination.

Blood Culture Contamination in a Community Hospital- less than 2% is achievable

Abstract Introduction/Objective Blood cultures are commonly obtained to evaluate the presence of bacteria or fungal infection in a patient’s bloodstream. The presence of living microorganisms circulating in the bloodstream is of substantial prognostic and diagnostic importance. A positive blood culture indicates a reason for the patient’s illness and provides the etiological agent for antimicrobial therapy. Collection of blood culture is an exact process that requires time, the proper order of draw, and following of correct protocol. The busy Emergency department that requires multiple demands for nurse’s time, turnover of staff, rushing from one task to another can result in the improper collection and false-positive blood cultures. The national benchmark is set at 3% by the American Society of Clinical Microbiology (ASM) and The Clinical and Laboratory Standard Institute (CLSI). False-positive blood culture results in increased length of stay and unnecessary antimicrobial therapy, resulting in an increased cost burden to the hospital of about $5000 per patient. Methods/Case Report At our 150-bed community hospital, 26 beds Emergency Department, we have come a long way in reduction of our blood culture contamination rates from upwards of 4% to less than 2%, far lower than the national benchmark. Results (if a Case Study enter NA) NA Conclusion There are multiple devices available from various manufacturers claiming to reduce blood culture contamination. These devices do reduce blood culture (BC) contamination but at an added cost of the device. The rate of BC can be reduced and less than 3% is achievable by materials available in the laboratory. We have achieved this by providing training to every new staff by demonstration and direct observation, providing everything required for collection in a kit, using proper technique, the inclusion of diversion method that involves the aseptic collection of a clear tube before collecting blood cultures, and following up monthly on any false positive blood cultures.

PREDICTORS AND OUTCOMES OF BACTERIAL AND FUNGAL SUPERINFECTIONS IN CRITICALLY ILL PATIENTS WITH COVID-19

TOPIC: Chest Infections TYPE: Original Investigations PURPOSE: Secondary infections are well-described complications in patients with viral pneumonia and are associated with increased mortality and morbidity (1). A recent meta-analysis reported that secondary infections in critically ill Coronavirus Disease 19 (COVID-19) patients in intensive care unit (ICU) are around 14% (2). Most of the studies are limited by false-positive cultures in non-sterile body fluids (2). Our study aims to assess the burden of secondary infections by focusing on the positive rate of sterile body fluid cultures in ICU patients, to examine associated risk factors and to assess their impact on outcome. METHODS: Retrospective analysis of all adult patients with COVID-related acute respiratory distress syndrome (ARDS) admitted to the ICUs of a quaternary care hospital between 03/01/2020 and 05/31/2020. Patients who had positive sterile body fluid (blood, peritoneal, pleural or cerebrospinal fluid) cultures for bacteria or fungi, were compared with those without positive cultures. RESULTS: Of the 210 patients admitted to our ICU with COVID-19 related ARDS, 55 patients (26%) had positive sterile body fluid cultures, of which 37 grew bacteria, 7 fungi and 11 both. Patients with positive cultures were similar in terms of baseline demographics, comorbidities and severity of illness at ICU admission to those patients without positive cultures. Peak inflammatory markers were significantly higher in the positive culture group. In the positive culture group, the rates of receipt of steroids (78% vs. 61%, p=0.02) and convalescent plasma (64% vs. 45%, p=0.03) were significantly higher. The prevalence of acute kidney injury (AKI) requiring dialysis was significantly greater in the positive culture group (55% vs. 28%, p<0.001). There was no difference in terms of mortality between the two groups. However, mechanical ventilation (MV) free days at day 28 were significantly lower in the positive culture group (Mean ± S.D: 2.7 ± 5.7 vs. 6 ± 9.9, p=0.004). CONCLUSIONS: Our study shows that the incidence of superinfections in COVID-19 patients admitted to ICUs is higher than previously reported. The higher incidence is comparable to the rate of superinfections in the H1N1 influenza pandemic of 2009 (2). However, the high rates of steroid and plasma administration in our positive culture group may also have contributed to the high incidence of secondary infections. Our results have also shown that these infections may prolong ventilatory support as well as increase the likelihood of developing AKI requiring dialysis. Therefore, intensivists need to be vigilant about not missing superinfections in patients with COVID-19 which can negatively impact patient outcomes. CLINICAL IMPLICATIONS: This study will help to identify the risk factors associated with higher incidence of secondary infections in patients with COVID-19, and will assist physicians to identify and treat them early in the course of disease. 1. I. Martin-Loeches, A. Sanchez-Corral, E. Diaz, R.M. Granada, et al., H1N1 SEMICYUC Working Group Community-acquired respiratory coinfection in critically ill patients with pandemic 2009 influenza A(H1N1) virus. Chest, 139 (2011), pp. 555-562. 2. Lansbury L, Lim B, Baskaran V, Lim WS. Co-infections in people with COVID-19: a systematic review and meta-analysis. J Infect. 2020;81(2):266-275. DISCLOSURES: No relevant relationships by ALEENA ARSHAD, source=Web Response No relevant relationships by Dipak Chandy, source=Web Response No relevant relationships by Oleg Epelbaum, source=Web Response No relevant relationships by Daniel Greenberg, source=Web Response No relevant relationships by Muhammad Rizwan, source=Web Response No relevant relationships by Hamid Yaqoob, source=Web Response

Reduction of False-positive Blood Culture Rates Using a Passive Blood Diversion Device in an Urban Academic Pediatric Emergency Department

Background Blood cultures contaminated with common commensals during collection contribute to antibiotics overuse, return visits to the Emergency Department (ED), and increased overall medical costs. There are published quality improvement projects aimed at implementing best practices to reduce false positive blood culture (FPBC) rates in adults, but literature is lacking in pediatrics, and few studies include the use of passive diversion devices designed to remove an aliquot of blood likely to contain skin flora. FPBC rates in our pediatric ED range from 0.45% to 5.63%. Our FPBC institutional goal is Methods In an urban, academic, freestanding pediatric hospital, the ED has 35,000 patient encounters and obtains 2800 blood cultures annually. In each study period, passive blood diversion devices were bundled with collection supplies. Education with best practices for technique, use of the device, and instructions to record device non-use were provided. Positive blood culture results were reviewed by the Infection Preventionist to determine true infection versus FPBC. Results In the first study period, 341 blood cultures were drawnwith an overall FPBC rate of 1.5%. The rate of FPBC when the device not used was 10.5% (4 of 38). In the second study period, 905 blood cultures were drawn with an overall FPBC rate of 0.22%. The rate of FPBC when the device not used was 6.06% (2 of 33). Zero FPBCs occurred with device use in each study period (0 of 303) and (0 of 874). Conclusions This significant reduction (by Fisher's exact test p = 0.0001) suggests that employing a passive blood diversion device in addition to targeted education may decrease FPBCs; antibiotics overuse, costs, and return visits in the pediatric ED setting.

G-control Charts for Contamination Rates of Blood Cultures in a University Hospital

Objective: To determine blood culture contamination rates, and display with a g-chart.Materials and Methods: The medical records of patients, from whom blood cultures were obtained in a university hospital, during January and December 2019 were retrieved and reviewed for contamination. The Center for Disease Control and Prevention (CDC) criteria were used to classify the blood culture results. The contamination rates were illustrated with a g-chart.Results: We identified 331 false-positive blood cultures, among 32,961 cultured specimens; yielding a contamination rate of 1.0% (95%CI = 0.9% – 1.1%). The highest contamination events occurred in the Emergency department (49.2%), Pediatric ICU (5.2%) and Neonatal ICU (4.8%), respectively. The most common commensal bacterial genus were Staphylococcus coagulase negative (67.1%), Bacillus spp. (10.2%) and Corynebacterium spp. (7.6%), correspondingly. The g-charts could identify 14 abnormal variations, in 41 locations.Conclusion: The contamination rates found were within ranges of other reports. G-charts are simple to construct, easy to interpret and sensitive for detection of real time epidemics.

Prevalence and Predictors of Bacterial Contamination in Excisional Lymph Node Biopsies: Implications for Diagnosis and Management.

Routine tissue handling exposes lymph node specimens to microbial contamination that can confound microbiological culture results and interfere with diagnosis. The scope and impact of this problem remain poorly understood. We combined over 13 years of lymph node pathology, culture data, and patient records to define the prevalence, predisposing factors, microbiology, and clinical management of false-positive lymph node cultures at a large academic medical center. Nearly one third (31.9%) of 216 cultured lymph nodes yielded bacterial growth. Approximately 90% of positive bacterial cultures grew 1 of 2 common skin-resident taxa-coagulase-negative Staphylococcus and Cutibacterium acnes-with well-documented predispositions for contamination in other clinical settings. Lymph nodes excised from axillary, cervical, and inguinal regions yielded higher positive culture rates than nodes excised from the mediastinum, suggesting proximity to the skin surface may increase contamination risk. Accordingly, cultures from thoracoscopic pulmonary resections displayed contamination rates over 5-fold lower than those from percutaneously accessed lymph nodes. Lymph nodal tissue allocated for culture in the operating room yielded unexpectedly high contamination rates, significantly higher than cultures sent from the frozen section processing area. A significant minority of contamination events were noted in the clinical record and prompted antibiotic therapy on multiple occasions. Collectively, our results illuminate the risk factors contributing to bacterial contamination and argue that routine lymph node bacterial cultures provide minimal clinical benefit for adult patients. This widespread bacterial contamination also warrants cautious implementation of increasingly sensitive molecular microbiology tools for excised tissues.

Cross-Contamination versus Outbreak: Pre-XDR Mycobacterial Strains Confirmed by Whole-Genome Sequencing.

Whole-genome sequencing (WGS) is promising for the quality control of laboratory facilities for Mycobacterium tuberculosis (MTB) strains. We describe the clinical and laboratory characteristics of false positive versus true positive MTB cultures based on WGS, which were experienced in a real clinical setting. Strain harvest and DNA extraction from seven isolates from pre-extensive drug-resistant (pre-XDR) TB patients transferred to the Korea University Ansan Hospital were performed, and epidemiologic links and clinical information, including the phenotypic drug susceptibility test (pDST), were investigated. WGS was performed using Ion GeneStudio with an ION530tm chip (average sequencing depth, ~100-fold). In the phylogenetic tree, identical and different strains were distributed separately. Five of the seven isolates were identical; the remaining two isolates differed from the others. The images of the referred pre-XDR-TB patients with false positive MTB that were analyzed were of regions close to old TB scars. Further, the results of WGS gene mutation analysis for ethambutol, streptomycin, and fluoroquinolone resistance in all six patients were not concordant with the pDST results. WGS and clinical information were useful in differentiating laboratory cross-contamination from true positive TB, thereby avoiding the unnecessary treatment of false positive patients and delay in treating true positive TB patients, with reliable genotypic drug resistance results.

Rapid quantitative screening of cyanobacteria for production of anatoxins using direct analysis in real time high-resolution mass spectrometry.

Anatoxins (ATXs) are a potent class of cyanobacterial neurotoxins that are increasingly problematic in drinking water reservoirs and recreational water bodies worldwide. Because of their high polarity and low molecular weight, analysis of ATXs is challenging and they can be considered underreported compared with other classes of cyanobacterial toxins. Improved screening methods are therefore needed to effectively assess their occurrence and concentrations in the environment. A rapid screening method was developed for ATXs in cyanobacteria using direct analysis in real time combined with high-resolution mass spectrometry (DART-HRMS), requiring less than 2 min per sample for triplicate analysis. The developed method was evaluated for its quantitative capabilities, applied to the screening of 30 cyanobacterial culture samples for the presence of anatoxin-a, homoanatoxin-a and dihydroanatoxin-a, and compared with a more typical liquid chromatography (LC)/HRMS method. Excellent linearity was observed in the analysis of a matrix-matched calibration curve using DART-HRMS, with ionization suppression of about 50% and relative standard deviations between replicate analyses of approximately 30%. Limits of detection for both anatoxin-a and homoanatoxin-a were estimated as 1 ng/mL. Excellent agreement was observed between DART-HRMS and LC/HRMS with all ATX-producing cultures correctly identified and only one false positive culture by DART-HRMS. DART-HRMS shows excellent promise for the rapid, quantitative screening of ATXs in cyanobacteria and could be expanded in the future to include the analysis of field samples and drinking water, as well as additional ATX analogues.