False-positive Cultures Research Articles

Next-Generation Sequencing for Pathogen Identification in Infected Foot Ulcers

Category:OtherIntroduction/Purpose:Foot infections are often polymicrobial with diverse microbiomes. Accurate identification of the main pathogen in diabetic foot ulcer (DFU) remain challenging due to contamination or negative cultures often leading to ineffective post-surgical antibiotic treatment. Application of molecular diagnostics, such as next generation sequencing (NGS) has been explored as an alternative to standard culture in orthopaedic infections. NGS is highly sensitive and detects an entire bacterial genome along with pharmacologic resistant genes in a given sample. We sought to investigate the potential use of NGS for accurate diagnosis and quantification of various species in infected DFU. We hypothesize that NGS will provide a more accurate means of diagnosing and profiling microorganisms in infected DFU compared to the standard culture method.Methods:We investigated 30 infected DFU patients who underwent surgical treatment by a single academic orthopaedic surgeon from October 2018 to September 2019. The average age of the patient was 60.4 (range 33-82) years-old. Surgical procedures performed were irrigation and debridement (12), toe or ray amputation (13), calcanectomies (4), and below-knee amputation (1). Infected bone specimens were obtained intraoperatively and processed for standard culture and NGS. Quantitative PCR was performed to determine the bacterial burden present in the sample. DNA was amplified by PCR from a highly conserved region of the rRNA gene in the bacteria (16S rRNA). Once a high level of DNA was generated and determined, it was compared against NIH GenBank database. Concordance between the standard culture and NGS was assessed.Results:In 28 of 29 patients, pathogens were identified by both NGS and culture, with complete consistency of organisms in 13 cases (concordance rate: 43.3%). NGS provided relative quantitative measures and the presence of antibiotic resistant genes for each pathogen. In NGS, Anaerococcus species (79.3%) was the most common organism, followed by Streptococcus species (44.8%), Prevotella species (44.8%), Finegoldia magna (44.8%). In culture, S. aureus (58.6%) was the most common, followed by Streptococcus species (34.5%), coagulase-negative Staphylococci (24.1%), Corynebacterium species (20.7%). On average, NGS revealed 5.1 (1-11) number of pathogens, whereas standard culture revealed 2.6 (1-6) pathogens in a given sample. NGS identified 2 cases with false positive standard culture and detected antibiotic resistant organisms in 15 specimens.Conclusion:NGS is an emerging method of microbial identification in orthopedic infection. It is particularly helpful in profiling diverse microbes in polymicrobial infected DFU. It can identify major pathogens and may correct false positive or false negative culture. NGS may allow a faster invitation of postoperative targeted antibiotic therapy.

Passive Engineering Controls Result in Sustained 66% Reduction in Blood Culture Contamination

Background: Blood culture testing is an important diagnostic tool in identifying the presence of microbes in the bloodstream. Tests are frequently contaminated, leading to false-positive results. Blood culture contamination can result in unnecessary antibiotic treatment, extended hospital length of stay, and patient exposure to hospital-acquired conditions. Methods: St. Mary’s Regional Medical Center (SMRMC) in Russellville, Arkansas, struggled with blood-culture contamination rates, with an average of 6.8% from 2014 to 2018. Ongoing staff education yielded a reduction to an average of 5%. In an effort to reduce the contamination rates, our facility elected to try a novel specimen diversion device. Laboratory and emergency department (ED) staff were educated on the diversion device prior to the initiation of the trial period. Compliance with the diversion device averaged 70%–75% during the trial period. Monitoring of contaminations was added to our daily safety huddle to provide a quick turnaround time for false-positive education to specific clinical staff. Results: The results were significant, with a decrease in contamination rates from 4.93% to 1.66%—a 66% reduction. Improved blood culture testing has several advantages: best practice for patient care is first and foremost, along with other financial benefits for the facility. Several articles have estimated the cost of a contaminated culture to be $3,000–$10,000 per event; SMRMC has adopting an estimated cost of $4,000. The number of cultures at our hospital averages ~4,400 per year, and these results suggest a savings of >$500,000 per year (as contaminations on an annual basis fell from 217 to 73). With this intervention, 144 patients were spared from receiving unnecessary antibiotics as a result of a false-positive blood culture testing. Conclusions: We conducted a brief analysis to determine whether there was any obvious change in length of stay for patients with a false-positive blood culture compared to those with true negative results. In analyzing data for 3 different months, patients with contaminated cultures spent an average of 3.97 additional days in the facility. In conclusion, the implementation of this specimen diversion device significantly lowered our contamination rates, was integrated into practice, and has provided clinical and financial benefits.Funding: NoneDisclosures: None

Impact of Performing Cultures of Peritoneal Fluid Correctly on the Reduction of False-Positive and False-Negative Culture Rates in Patients on Peritoneal Dialysis (PD) Presenting with Peritonitis

Impact of Performing Cultures of Peritoneal Fluid Correctly on the Reduction of False-Positive and False-Negative Culture Rates in Patients on Peritoneal Dialysis (PD) Presenting with Peritonitis

Secondary bacterial culture of platelets to mitigate transfusion-associated sepsis: A 3-year analysis at a large academic institution.

In 2019, the United States Food and Drug Administration published its final recommendations to mitigate bacterial contamination of platelets. We sought to evaluate our secondary bacterial culture (SBC) strategy in light of those recommendations. A retrospective analysis was conducted of SBC data (October 2016-2019) at our institution. SBC was performed upon receipt (Day 3 after collection); 5 mL of platelet product was inoculated aseptically into an aerobic bottle and incubated at 35°C for 3 days. For 8 months, a 10-mL inoculum was trialed. No quarantine was applied. All positive cultures underwent Gram staining and repeat culture of the platelet product (if available). A probable true positive was defined as concordant positive culture between the initial and repeat culture. The incidence of probable true- and false-positive cultures were reported descriptively and differences evaluated by sampling volume. Over 3 years, 55 896 platelet products underwent SBC, yielding 30 initial positive results (approx. 1/1863 platelets); 25 (83.3%) signaled within 24 hours of SBC. The rates of probable true positive, false positive, and indeterminate for 5 mL were 0.027% (1/3771), 0.002% (1/45 251) and 0.018% (1/5656), respectively. The respective rates for 10 mL were 0.018% (1/5323), 0.07% (1/1521), and 0%. Seven of eight (87.5%) false-positive SBCs occurred with a 10-mL inoculum. No septic transfusion reactions were reported. SBC continues to interdict bacterially contaminated units of platelets. Our findings suggest higher rates of false positivity using large-volume inocula.

Think Different: Overcoming Challenges to Adopt an Electronic Blood Culture Order That Supports Central Line-Associated Bloodstream Infection (CLABSI) Reduction

<h3>Background</h3> Central venous catheters (CVC) are a frequent cause of healthcare-associated bloodstream infections. During root-cause analysis of CLABSI, our team observed positive blood cultures obtained from CVC devices when the peripheral culture result was negative. CVCs are often colonized, increasing the likelihood of a false-positive culture. Our health system is comprised of 9 hospitals and over 4000 practicing physicians supported by one unified electronic medical record (EMR) platform. The current blood culture order did not limit options for site selection, allowing variability and inconsistent performance affecting patient outcomes. <h3>Methods</h3> We reviewed events from June 2018 through October 2019 to determine how many CLABSI were identified based on specimens collected from CVC vs peripherally. We itemized available EMR order selections and identified multidisciplinary stakeholders and frontline providers to influence peers on proposed EMR changes. Infection Prevention proposed modifying the blood culture order to guide the provider to select peripheral source. <h3>Results</h3> 36% of CLABSI were identified from a CVC source with a negative peripheral culture. The current order allowed free selection of options for specimen source in the EMR. It took over 12 months to approve and implement a re-designed blood culture order across a large hospital system. When a provider selects a CVC source for blood culture collection, additional questions are required to complete the order. These include: unable to obtain from peripheral source OR peripheral source positive and suspecting central line infection. <h3>Conclusions</h3> Unanticipated adverse events can be caused by poorly designed systems that allow users multiple choices without consciously considering relevant information. Limited, forced functions guide clinicians to select CVC blood culture only when clinically indicated for diagnosis of catheter-related bloodstream infection. System change is successful when a multidisciplinary team led by a physician champion can manage organizational culture to support patient outcomes.

Pathogenic genetic variations of C. acnes are associated with clinically relevant orthopedic shoulder infections.

Many surgeons continue to face the clinical dilemma of interpreting a positive aspiration or unexpected positive Cutibacterium acnes (C. acnes) culture. There are factors that complicate the interpretation of positive cultures including variations in both frequency of false positive cultures and virulence properties. As indices of virulence, hemolytic strains, from previously confirmed clinically infected shoulders, were compared with non-hemolytic isolates determined to be contaminants, by RNA-sequencing (RNA-Seq). Six C. acnes isolates from patients who underwent revision total shoulder arthroplasty (TSA) were identified based on previously described infection criteria. Three C. acnes isolates from each group underwent RNA-Seq. Differential gene expression analysis, principal component analysis (PCA), and heatmap analysis were used to determine the gene variation and patterning between the definite infection and probable contaminant isolates. Differential gene expression analysis identified genes that were differentially expressed between the isolates classified as definite infection and isolates classified as probable contaminants. PCA using a 500 gene subset of identified genes was able to find combinations of these genes that separated out the definite infection and probable contaminants isolates. The heatmap demonstrated similar gene expression in the three Definite Infections isolates, and significantly different expression when compared with the probable contaminant isolates. Clinical significance: C. acnes revision TSA isolates classified as definite infection and probable contaminant demonstrated a similar gene expression pattern to each respective group and different gene expression pattern when compared between groups. These findings indicate distinct differences in C. acnes strains associated with clinically relevant orthopedic TSA infections.

The incidence and incubation period of false-positive culture results in shoulder surgery

Postoperative shoulder infection is a significant complication requiring timely identification and treatment. Indolent infections such as those involving Cutibacterium acnes (formerly Propionibacterium acnes) provide a diagnostic dilemma as they present differently, without the acute symptoms associated with most postoperative bone and joint infections. Furthermore, Cacnes is thought to be a common contaminant isolated from intraoperative cultures. With no consensus algorithm, long-held cultures play a major role in guiding management decisions in potential postoperative shoulder infection. Our study sought to determine the incidence of positive culture results in both open and arthroscopic procedures in noninfected patients, as well as to clarify whether an increase in the incubation time frame leads to an increased rate of culture growth. One hundred patients were prospectively enrolled into either the open or arthroscopic procedure group. Patients with abnormal inflammatory laboratory findings, a history of shoulder surgery, or corticosteroid injection within 6 months of surgery were excluded from the study. Three cultures were obtained for each patient: superficial tissue culture, tissue culture, and "sterile" control swab. Cultures were held for 28 days and checked at regular intervals. All patients were followed up clinically for 6 months to ensure no signs of postoperative infection occurred. Ultimately, 95 patients were included in the final analysis. The false-positive rate was 17.0% in those who underwent open shoulder surgery and 10.4% in those who underwent arthroscopic shoulder surgery. The incidence of positive Cacnes culture results was 6.4% in the open group, whereas Cacnes was not isolated in the arthroscopic group. All positive bacterial culture results were reported within 7 days of collection. One culture result was positive for moldat 26 days. A relatively high false-positive culture rate occurred in both open and arthroscopic shoulder surgery. Cacnes was the most commonly identified bacterium in cultures in the open surgery group. Knowledge of one's institutional false-positive culture rate could be important in avoiding potentially inappropriate treatment. Additionally, we found that holding cultures longer than 14 days did not lead to an increased rate of false-positive culture results.

False-Positive Blood Cultures: The Need for Follow-up

AbstractThe diagnosis of blood-borne infections in immunocompromised patients is a major challenge for the clinical microbiology laboratory. Isolation of bloodborne pathogens in these patients has profound clinical implications, yet is fraught with technical problems, including the presence of unusual and difficult to isolate pathogens. Coupled with this is the problem of false-positive blood culture signals from automated blood culture systems which further delays the definitive diagnosis. Here, we present a case of an 8-year-old boy with Ph +ve acute lymphoblastic leukaemia who has repeated ‘false positive’ blood cultures and later grew an uncommon organism.

Cutibacterium acnes is Isolated from Air Swabs: Time to Doubt the Value of Traditional Cultures in Shoulder Surgery?

Given high rates of positive Cutibacterium acnes (C. acnes) cultures in cases of both primary and revision shoulder surgery, the ramifications of positive C. acnes cultures remain uncertain. Next generation sequencing (NGS) is a molecular tool that sequences the whole bacterial genome and is capable of identifying pathogens and the relative percent abundance in which they appear within a sample. The purpose of this study was to report the false positive culture rate in negative control specimens and to determine whether NGS has potential value in reducing the rate of false positive results. Between April 2017 and May 2017 swabs were taken during primary shoulder arthroplasty. After surgical time out, using sterile gloves, a sterile swab was opened and exposed to the air for 5 seconds, returned to its contained, and sealed. One swab was sent to our institution's microbiology laboratory for aerobic and anaerobic culture and held for 13 days. The other sample was sent for NGS (MicroGen Dx, Lubbock, TX), where samples were amplified for pyrosequencing using a forward and reverse fusion primer and matched against a DNA library for species identification. For 40 consecutive cases, swabs were sent for culture and NGS. C. acnes was identified by culture in 6/40 (15%) swabs and coagulase negative staphylococcus (CNS) was identified in 3/40 (7.5%). Both cases with positive NGS sequencing reported polymicrobial results with one sample (2.5%), including a relative abundance of 3% C. acnes. At 90 days after surgery, there were no cases of clinical infection in any of the 40 cases. We demonstrate that the two most commonly cultured organisms (C. acnes and CNS) during revision shoulder arthroplasty are also the two most commonly cultured organisms from negative control specimens. Contamination can come from air in the operating room or laboratory contamination.

Using Machine Learning to Predict Bacteremia in Febrile Children Presented to the Emergency Department.

Blood culture is frequently used to detect bacteremia in febrile children. However, a high rate of negative or false-positive blood culture results is common at the pediatric emergency department (PED). The aim of this study was to use machine learning to build a model that could predict bacteremia in febrile children. We conducted a retrospective case-control study of febrile children who presented to the PED from 2008 to 2015. We adopted machine learning methods and cost-sensitive learning to establish a predictive model of bacteremia. We enrolled 16,967 febrile children with blood culture tests during the eight-year study period. Only 146 febrile children had true bacteremia, and more than 99% of febrile children had a contaminant or negative blood culture result. The maximum area under the curve of logistic regression and support vector machines to predict bacteremia were 0.768 and 0.832, respectively. Using the predictive model, we can categorize febrile children by risk value into five classes. Class 5 had the highest probability of having bacteremia, while class 1 had no risk. Obtaining blood cultures in febrile children at the PED rarely identifies a causative pathogen. Prediction models can help physicians determine whether patients have bacteremia and may reduce unnecessary expenses.

False-Positive Mycobacterium tuberculosis Detection: Ways to Prevent Cross-Contamination.

The gold standard method for diagnosis of tuberculosis is the isolation of Mycobacterium tuberculosis through culture, but there is a probability of cross-contamination in simultaneous cultures of samples causing false-positives. This can result in delayed treatment of the underlying disease and drug side effects. In this paper, we reviewed studies on false-positive cultures of M. tuberculosis. Rate of occurrence, effective factors, and extent of false-positives were analyzed. Ways to identify and reduce the false-positives and management of them are critical for all laboratories. In most cases, false-positive is occurring in cases with only one positive culture but negative direct smear. The three most crucial factors in this regard are inappropriate technician function, contamination of reagents, and aerosol production. Thus, to reduce false-positives, good laboratory practice, as well as use of whole-genome sequencing or genotyping of all positive culture samples with a robust, extra pure method and rapid response, are essential for minimizing the rate of false-positives. Indeed, molecular approaches and epidemiological surveillance can provide a valuable tool besides culture to identify possible false positives.

Concealed Penis after Circumcision: Is It Beneficial in Lowering Uropathogenic Colonization in Penile Skin and Preventing Recurrence of Febrile Urinary Tract Infections?

To discuss whether concealed penis after circumcision lowers perimeatal urethral and glanular sulcus uropathogenic bacterial colonization in healthy boys with no urinary tract problems and prevents attacks of febrile urinary tract infections in non-healthy boys with defined urinary tract abnormalities. Materials and Methods: This case-control study was conducted in Ibn-i Sina Hospital and retrospectively collected data of 471 boys were analyzed. All patients were scanned for any urinary tract abnormality and those with any defined abnormalities were classified as non-healthy group. (123 patients) Non-healthy patients were divided into two subgroups as concealed (n:31) and non-concealed (n:92) penis after circumcision. Healthy patients with no urinary problems were divided into three groups as circumcised without concealed penis (n:144), with concealed penis after circumcision (n:104) and uncircumcised control group (n:100). Bacterial cultures were obtained from both periurethral meatal and glanular sulcus areas by adhering strictly to the rules of obtaining bacterial culture to avoid false-positive or negative culture results. Also only uropathogenic bacterias were evaluated, irrelevant results were excluded. Results: Mean age was similar in healthy population. Comparison of three groups showed that there was a significant difference in both cultures.(P = .026 for periurethral meatal region, P = .039 for glanular sulcus region) In post hoc analysis, non-concealed group had a lower rate of culture positivity in both areas compared to other groups. Mean age was also similar in non-healthy population. Mean follow-up period was 18.2 months. Patients with concealed penis after circumcision had a significantly higher number of febrile UTI attacks (20 attacks in 8 patients vs 7 attacks in 5 patients) compared to non-concealed group. (P = .019) All febrile UTI attacks except one in this group occurred below the age of 12 months. A total of 10 patients in both healthy and non-healthy groups had postoperative hemorrhage after circumcision and only 1 patient had a wound infection. Conclusion: Concealed penis after circumcision does not lower perimeatal urethral and glanular sulcus uropathogenic bacterial colonization in healthy patients and does not protect unhealthy patients from febrile urinary tract infection attacks. If circumcision is planned, concealed penis should be avoided and also parents should be informed about the possible risks due to concealed penis before the procedure, particularly in patients with urinary tract abnormalities.

2014. Assessment of Cost, Morbidity, and Mortality Associated with Blood Culture Contamination

BackgroundBlood cultures are the primary diagnostic tool for bloodstream infections, but accuracy of results is dependent on collection technique. Decreasing blood culture contaminations is a priority for antimicrobial stewardship programs as false positives can expose patients to adverse effects of unnecessary antibiotics. In this study, we present an analysis comparing clinical outcomes and cost associated with false-positive and true negative blood cultures at our institution.MethodsWe conducted a single-center, retrospective, case–control study in patients admitted following blood culture collection in the emergency department from 2014 to 2018. Demographic and clinical characteristics were evaluated in patients with false-positive blood cultures (cases) and negative blood cultures (controls). Contaminants were identified per American Society of Microbiology recommendations. Clinical outcomes were compared between cases and controls, and adjusted analyses were performed with logistic regression, linear regression, and generalized linear models controlling for age, race, body mass index, and sepsis. Statistical analysis was performed using SAS 9.4.ResultsA total of 1,102 cases and 11,266 controls were included in analysis. All clinical outcome measures were significantly higher in patients with contaminated blood cultures (see table). Select clinical outcomes remained significant when controlling for potential confounders.ConclusionTo the best of our knowledge, this is the largest study evaluating the clinical and financial impact of blood culture contamination with inclusion of >1,000 cases during a 5-year period. Our study shows that blood culture contamination is associated with increased length of stay, unnecessary exposure to antibiotics and procedures, development of antibiotic-associated adverse events, and higher hospital charges as reported in smaller studies. However, this study is the first to the best of our knowledge reporting increased mortality associated with blood culture contamination. Implementation of innovative strategies to reduce contamination should be pursued. Antimicrobial stewardship programs should prioritize identification of contaminants and rapid de-escalation of inappropriate antibiotics in these patients to improve patient care. Disclosures All authors: No reported disclosures.

Impact of Blood Culture Contamination on Patients and Health Care Systems: A Review of QI Strategies Within the ED

Emergency departments are a primary site for evaluation of pediatric patients presenting with fever. Part of this evaluation may include the collection of blood cultures to rule out infection from a bacterial pathogen. Many of these samples, however, yield results that are not representative of a true bacterial infection, causing undue burden on patients and their families and adding considerable costs for the health care system. Reducing the rate of false-positive blood cultures may be achieved through quality improvement methodology. Strategies for the reduction of blood culture contamination, including process improvement and targeted education, are discussed in this review.

Model to evaluate the impact of hospital-based interventions targeting false-positive blood cultures on economic and clinical outcomes

Blood culture contamination (BCC) increases length of stay (LOS) and leads to unnecessary antimicrobial therapy and/or hospital-acquired conditions (HACs). To quantify the magnitude of additional LOS, costs to hospitals and society, and harm to patients attributable to BCC. A retrospective matched survival analysis was performed involving hospitalized patients with septicaemia-compatible symptoms. BCC costs, HACs and potential savings were calculated based on the primary LOS data, a modified Delphi process and published sources. The cost analysis compared standard care with interventions for reducing BCC, and estimated annual economic and clinical consequences for a typical hospital and for the USA as a whole. Patients with BCC experienced a mean increase in LOS of 2.35 days (P=0.0076). Avoiding BCC would decrease costs by $6463 [$4818 from inpatient care (53% of which was from reduced LOS) and 26% from reduced antibiotic use]. Annually, in a typical 250- to 400-bed hospital, employing phlebotomists would save $1.3 million and prevent 24 HACs (including two cases of Clostridium difficile infection); based on clinical efficacy evidence, use of the studied initial specimen diversion device (ISDD) would save $1.9 million and prevent 34 HACs (including three cases of C.difficile infection). In the USA, the respective strategies would prevent 69,300 and 102,900 HACs (including 6000 and 8900 cases of C.difficile infection) and save $5 and $7.5 billion. Costs and clinical burdens associated with false-positive cultures are substantial and can be reduced by available interventions, including phlebotomists and use of ISDD.

Strong increase of true and false positive mycobacterial cultures sent to the National Reference Centre in Belgium, 2007 to 2016.

IntroductionIn 2007, a new federal legislation in Belgium prohibited non-biosafety level 3 laboratories to process culture tubes suspected of containing mycobacteria.AimTo present mycobacterial surveillance/diagnosis data from the Belgian National Reference Centre for mycobacteria (NRC) from 2007 to 2016.MethodsThis retrospective observational study investigated the numbers of analyses at the NRC and false positive cultures (interpreted as containing mycobacteria at referring clinical laboratories, but with no mycobacterial DNA detected by PCR in the NRC). We reviewed mycobacterial species identified and assessed trends over time of proportions of nontuberculous mycobacteria (NTM) vs Mycobacterium tuberculosis complex (MTBc), and false positive cultures vs NTM.ResultsFrom 2007 to 2016, analyses requests to the NRC doubled from 12.6 to 25.3 per 100,000 inhabitants. A small but significant increase occurred in NTM vs MTBc proportions, from 57.9% (587/1,014) to 60.3% (867/1,437) (p < 0.001). Although NTM infection notification is not mandatory in Belgium, we annually received up to 8.6 NTM per 100,000 inhabitants. M. avium predominated (ca 20% of NTM cultures), but M. intracellulare culture numbers rose significantly, from 13.0% (74/587) of NTM cultures in 2007 to 21.0% (178/867) in 2016 (RR: 1.05; 95% CI: 1.03–1.07). The number of false positive cultures also increased, reaching 43.3% (1,097/2,534) of all samples in 2016.ConclusionWe recommend inclusion of NTM in sentinel programmes. The large increase of false positive cultures is hypothesised to result from processing issues prior to arrival at the NRC, highlighting the importance of sample decontamination/transport and equipment calibration in peripheral laboratories.

False-positive blood culture results in patients with hematologic malignancies

Blood cultures are the most valuable tool when bacteremia is clinically suspected. Technical advances have led to the development of automated blood culture systems to detect bacterial infections. Usually positive signals in automated blood culture systems result from the proliferation of microorganisms. Cases are classified as false-positive when the automated blood culture system produces a positive signal but no microorganisms are detected on Gram-stained smears and no microorganism growth is observed in blood subcultures. False-positive blood culture results are very rare in patients with hematologic malignancies. Recently, we encountered four patients who had false-positive blood culture results. Two of the patients were diagnosed with acute leukemia, involving hyperleukocytosis and an excess of blasts. The other two patients were diagnosed with acute leukemia and diffuse large B cell lymphoma with leukocytopenia. Although hypercapnia or acidosis, apart from hyperleukocytosis, might also cause false-positive results, our cases clearly did not have these conditions. We should be aware of the possibility that false-positive blood culture results can occur in patients with leukocytopenia, as well as hyperleukocytosis. To understand the mechanisms responsible for the observed false-positive results, additional studies are needed after the accumulation of similar cases.

2006. Implementation of the T2 Biosystems T2Bacteria Panel in a Level-One Trauma Center, Safety Net Hospital

BackgroundRapid detection and identification of sepsis causing pathogens are critical for optimizing antimicrobial therapy to improve patient survival and reduce healthcare costs. The T2Bacteria Panel RUO is a molecular diagnostic allowing detection of Gram-negative Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Gram-positive Staphylococcus aureus and Enterococcus faecium within a few hours. The purpose of our study was to determine the feasibility and efficacy of the T2Bacterial Panel RUO in an Emergency Medicine (ED) and Surgical Intensive Care Unit (SICU) setting.MethodsAn IRB-approved, prospective, observational study was implemented at a Safety-Net, Level One Trauma Center in Denver, Colorado. Patients were enrolled who received an order for a blood culture from the ED or SICU. Patients who had blood drawn for cultures had a concurrent draw for testing with a T2Bacteria Panel RUO.ResultsSixty-six patients are included in the present interim analysis. Mean patient age was 51 years old (19–84), 36% were female, 86% Caucasian (34% Hispanic/Latino), and 74% of patients were enrolled upon presentation to the ED, 13% from the SICU, and 15% from the wards. 90% of blood sampling (culture and T2Bacteria) was done from peripheral stick while 7% were from the initial stick of a peripheral IV and 2% obtained from an indwelling catheter. 85% of blood cultures were negative. Of the 56 patients with negative blood culture, 53 had concordant negative T2Bacteria results, providing a specificity of 94.6%. 10 patients had positive blood cultures (15%) for T2Bacteria Panel RUO targets. Interestingly, only five of these (50%) had concordant positive T2Bacteria testing. Examining the discordant samples, all (5) blood culture positive, T2Bacteria negative were found to have clinically false-positive blood cultures. T2Bacteria positive samples were distributed as follows: two E.coli, one S. aureus, one K. pneumoniae, and one P. aeruginosa. No detections were made for E. faecium or A. baumannii.ConclusionIn this interim analysis, T2Bacteria Panel RUO provides feasible rapid diagnostics for ED and surgical ICU settings with a high specificity and much shorter time to result when compared with gold standard blood cultures.Disclosures C. Robinson, T2 Biosystems: Research Coordinator for funded study from T2 Biosystems, Research support. R. Jackson, T2 Biosystems: Research Assistant for funded study from T2 Biosystems, Research support. M. Cohen, T2 Biosystems: PI on study being funded by T2 Biosystems, not paying for any part of salary, Research support.

157. Reducing Blood Culture Contamination Rates Through the Use of a Red Top Tube Discard

BackgroundSepticemia is a major cause of death in the United States and accounts for up to $16.7 billion in annual health care expenses. Blood culture is the gold standard for laboratory diagnosis of bacteremia and resultant septicemia; however, false-positive blood cultures hinder the accurate determination of true bacteremia with often serious implications. The goal of this study was to determine the efficacy of collecting a 1 mL discard in a red tube prior to blood culture collection and to assess its effectiveness in reducing contamination rates in Hartford Hospital Emergency Department (HHED).MethodsDuring the months of June to December 2017 blood cultures were collected by the phlebotomy team using ChloraPrep (chlorhexidine) as the sole disinfecting agent. Blood cultures consisted of BD BACTEC plus Aerobic/F and BD BACTEC Lytic/10 Anaerobic drawn at the same time and monitored on BD BACTEC FX instrument for 5 days. Prior to collecting blood cultures 1 mL of blood was collected in a red top tube and discarded. Monthly and overall contamination rates were then compared with 2016 in which a red top discard tube was not used.ResultsDuring June to December 2016, there were a total of 9,576 blood cultures collected with a total of 178 contaminants and an overall contamination rate of 1.9%. During June to December 2017, there were a total of 9,133 blood cultures collected with a total of 73 contaminants and an overall contamination rate of 0.8%. During both years, our contamination rates were well below the CLSI recommendation; however, a significant reduction in blood culture contamination was observed after the use of a Red Top discard tube (0.8% vs. 1.9%) (Figures 1–3). ConclusionThe cost of a standard blood draw with Red Top tubes is minimal (few cents) while a single collection using an initial specimen diversion device (ISDD) can range from $15 to $18. During the course of this study, the use of a standard Red Top discard cost approximately $456 (2017); if an ISDD was used instead, this would have generated $136,995 in healthcare cost. At our institution, we were able to keep our contamination rates below 1% after the implementation of a standard Red Top discard tube. This suggests that the use of a Red Top discard prior to blood culture collection is an effective means for reducing and maintaining a low blood contamination rate.Disclosures All authors: No reported disclosures.

QuantiFERON-TB-GOLD In-Tube in Patients with Sarcoidosis

Sarcoidosis and tuberculosis (TB) are the diseases that share many similarities. Mycobacterium tuberculosis (MTB) culture results are the gold standard for the diagnosis of TB, but false positive results are not rare. The aim was to evaluate the utility of QFT in detecting latent TB infection in a group of sarcoidosis patients with negative history of TB and negative culture/BACTEC results, and checking sarcoidosis activity influence on the QFT results. Additionally, we assessed if QFT negative result may strengthen the suspicion that positive culture/BACTEC results are false positive. 37 culture-negative and 6 culture-positive sarcoidosis patients were enrolled. On the basis of clinical and radiological data TB was considered unlikely (false-positive results). A control group consisted of age-matched subjects with excluded TB (n = 37). QuantiFERON-TB GOLD In-Tube (QIAGEN, USA) was used according to the manual. Test validity was checked basing on the results obtained from a low-risk (n = 21) and active TB group (n = 23). The frequency of positive results tended to be higher in MTB(-) sarcoidosis (24.3% vs. 13.5% for the control group, p = 0.37), but was similar to the general population. None of culture-positive sarcoidosis patients was QFT-positive. The positive results were equally distributed among patients with active and inactive sarcoidosis. QFT has been found to be the useful test for the detection of latent TB infection in sarcoidosis patients. In addition, we confirm that sarcoidosis activity does not negatively influence the result of QFT. Moreover, QFT would be proposed as a cost-saving diagnostic test providing additional diagnostic information when false positive MTB culture result in the sarcoidosis patient is highly suspected. However, in each case clinical, radiological and epidemiological data should be considered before taking the therapeutic decision.