Unique blood culture for diagnosis of bloodstream infections in emergency departments: a prospective multicentre study

An emergency department intervention to improve earlier detection of community-onset bloodstream infection among hospitalized patients

BACKGROUND

Blood cultures (BCs) are essential microbiologic tests, but blood culturing diagnostic stewardship is frequently poor. We aimed to study the process-related failures and to evaluate the effect of an emergency department (ED) intervention on BCs collection practices and yield.

METHODS

We implemented an ED-quality improvement intervention including educational sessions, phlebotomists addition, promoting single-site strategy for BC-collection and preanalytical data feedback. BC-bottles collected, positive BCs, blood volumes and documentation of collection times were measured, before (December 2021-August 2022) and after (September 2022-July 2023) intervention. Results were corrected to hospitalizations admissions or days. We used interrupted-time series analyses for comparisons.

RESULTS

A total of 64,295 BC bottles were evaluated, 26,261 before and 38,034 postintervention. The median ED-BCs collected per week increased from 88 to 105 BCs (P < .0001), resulting from increased early sampling (P = .0001). Solitary BCs decreased (95%-28%), documented times increased (2.8%-25%), and average blood volume increased (3 mL to 4.5 mL) postintervention. Community-onset Bloodstream infections (BSIs) increased (39.6-52 bottles/1,000 admissions, P = .0001), while Health care-associated BSIs decreased (39-27 bottles/10,000 days, P = .0042). Contamination rates did not change.

CONCLUSIONS

An ED-focused intervention based on the education sessions and single-site strategy improved culturing stewardship and facilitated the early identification of BSI without an increase in contamination.

A clinical decision rule to rule out bloodstream infection in the emergency department: retrospective multicentric observational cohort study

BACKGROUND

We aimed to identify patients at low risk of bloodstream infection (BSI) in the ED.

METHODS

We derived and validated a prediction model to rule out BSI in the ED without the need for laboratory testing by determining variables associated with a positive blood culture (BC) and assigned points according to regression coefficients. This retrospective study included adult patients suspected of having BSI (defined by at least one BC collection) from two European ED between 1 January 2017 and 31 December 2019. The primary end point was the BSI rate in the validation cohort for patients with a negative Bacteremia Rule Out Criteria (BAROC) score. The effect of adding laboratory variables to the model was evaluated as a second step in a two-step diagnostic strategy.

RESULTS

We analysed 2580 patients with a mean age of 64 years±21, of whom 46.1% were women. The derived BAROC score comprises 12 categorical clinical variables. In the validation cohort, it safely ruled out BSI without BCs in 9% (58/648) of patients with a sensitivity of 100% (95% CI 95% to 100%), a specificity of 10% (95% CI 8% to 13%) and a negative predictive value of 100% (95% CI 94% to 100%). Adding laboratory variables (creatinine ≥177 µmol/L (2.0 mg/dL), platelet count ≤150 000/mm3 and neutrophil count ≥12 000/mm3) to the model, ruled out BSI in 10.2% (58/570) of remaining patients who had been positive on the BAROC score. The BAROC score with laboratory results had a sensitivity of 100% (95% CI 94% to 100%), specificity of 11% (95% CI 9% to 14%) and negative predictive value of 100% (95% CI 94 to 100%). In the validation cohort, there was no evidence of a difference in discrimination between the area under the receiver operating characteristic for BAROC score with versus without laboratory testing (p=0.6).

CONCLUSION

The BAROC score safely identified patients at low risk of BSI and may reduce BC collection in the ED without the need for laboratory testing.

Early detection of plasma d-lactate: Toward a new highly-specific biomarker of bacteraemia?

Background

Bloodstream infections are a leading cause of mortality. Their detection relies on blood cultures (BCs) but time to positivity is often between tens of hours and days. d-lactate is a metabolite widely produced by bacteria but very few in human. We aimed to evaluate d-lactate, d-lactate/l-lactate ratio and d-lactate/total lactate ratio in plasma as potential early biomarkers of bacteraemia on a strictly biological standpoint.

Methods

A total of 228 plasma specimens were collected from patients who had confirmed bacteraemia (n = 131) and healthy outpatients (n = 97). Specific l-lactate and d-lactate analyses were performed using enzymatic assays and analytical performances of d-lactate, d-lactate/total lactate and d-lactate/l-lactate ratios for the diagnosis of bacteraemia were assessed.

Results

A preliminary in vitro study confirmed that all strains of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus were able to produce d-lactate at significant levels. In patients, plasma d-lactate level was the most specific biomarker predicting a bacteraemia profile with a specificity and predictive positive value of 100% using a cut-off of 131 μmol.L^-1. However, sensitivity and negative predictive value were rather low, estimated at 31% and 52%, respectively. d-lactate displayed an Area Under Receiver Operating Characteristic (AUROC) curve of 0.696 with a P value < 0.0001. There was no difference of d-lactate levels between BCs bottles positive for Gram-positive or Gram-negative bacteria (p = 0.55).

Conclusion

d-lactate shows promise as a specific early biomarker of bacterial metabolism. The development of rapid automated assays could raise clinical applications for infectious diseases diagnosis including early bacteraemia prediction.

Impact of a strategy based on unique blood culture sampling on contamination rate and detection of bloodstream infections in critically ill patients

BACKGROUND

Unique blood culture (UBC) has been proposed to limit the number of venipuncture and to decrease the risk of BC contaminations (BCC) without affecting their yield. We hypothesized that a multi-faceted program based on UBC in the ICU may reduce the rate of contaminants with a similar performance for bloodstream infections (BSI) identification.

METHODS

In a before and after design, we compared the proportion of BSI and BCC. A first 3-year period with multi-sampling (MS) strategy followed by a 4-month washout period, where staff received education and training for using UBC, and a 32-month period, where UBC was routinely used, while education and feedback were maintained. During the UBC period, a large volume of blood (40 mL) was sampled through a unique venipuncture with additional BC collections discouraged for 48 h.

RESULTS

Of the 4,491 patients included (35% female patients, mean age 62 years) 17,466 BC were collected. The mean volume of blood per bottle collected increased from 2.8 ± 1.8 mL to 8.2 ± 3.9 mL between the MS and UBC periods, P < 0.01. A 59.6% reduction (95% CI 56.7-62.3; P < 0.001) of BC bottles collected per week was observed between the MS and UBC periods. The rate of BCC per patient decreased between the two periods from 11.2% to 3.8% (73.4% reduction; P < 0.001) for the MS and UBC periods, P < 0.001. Meanwhile, the rate of BSI per patient remained stable at 13.2% and 13.2% for the MS and UBC periods, P = 0.98.

CONCLUSIONS

In ICU patients, a strategy based on UBC reduces the contamination rate of cultures without affecting their yield.

A positive blood culture is associated with a lower haemoglobin increment in hospitalized patients after red blood cell transfusion

BACKGROUND AND OBJECTIVES

Abundant clinical evidence supports the safety of red blood cell (RBC) concentrates for transfusion irrespective of storage age, but still, less is known about how recipient characteristics may affect post-transfusion RBC recovery and function. Septic patients are frequently transfused. We hypothesized that the recipient environment in patients with septicaemia would blunt the increase in post-transfusion blood haemoglobin (Hb). The main objective was to compare the post-transfusion Hb increment in hospitalized patients with or without a positive blood culture.

MATERIALS AND METHODS

A retrospective cohort study using data from the Transfusion Research, Utilization, Surveillance, and Tracking database (TRUST) was performed. All adult non-trauma in-patients transfused between 2010 and 2017 with ≥1 RBC unit, and for whom both pre- and post-transfusion complete blood count and pre-transfusion blood culture data were available were included. A general linear model with binary blood culture positivity was fit for continuous Hb increment after transfusion and was adjusted for patient demographic parameters and transfusion-related covariates.

RESULTS

Among 210,263 admitted patients, 6252 were transfused: 596 had positive cultures, and 5656 had negative blood cultures. A modelled Hb deficit of 1.50 g/L in blood culture-positive patients was found. All covariates had a significant effect on Hb increment, except for the age of the transfused RBC.

CONCLUSION

Recipient blood culture positivity was associated with a statistically significant but modestly lower post-transfusion Hb increment in hospitalized patients. In isolation, the effect is unlikely to be clinically significant, but it could become so in combination with other recipient characteristics.

The characteristics of bacteremia among patients with acute febrile illness requiring hospitalization in Indonesia

Blood culturing remains the "gold standard" for bloodstream infection (BSI) diagnosis, but the method is inaccessible to many developing countries due to high costs and insufficient resources. To better understand the utility of blood cultures among patients in Indonesia, a country where blood cultures are not routinely performed, we evaluated data from a previous cohort study that included blood cultures for all participants. An acute febrile illness study was conducted from July 2013 to June 2016 at eight major hospitals in seven provincial capitals in Indonesia. All participants presented with a fever, and two-sided aerobic blood cultures were performed within 48 hours of hospital admission. Positive cultures were further assessed for antimicrobial resistance (AMR) patterns. Specimens from participants with negative culture results were screened by advanced molecular and serological methods for evidence of causal pathogens. Blood cultures were performed for 1,459 of 1,464 participants, and the 70.6% (1,030) participants that were negative by dengue NS1 antigen test were included in further analysis. Bacteremia was observed in 8.9% (92) participants, with the most frequent pathogens being Salmonella enterica serovar Typhi (41) and Paratyphi A (10), Escherichia coli (14), and Staphylococcus aureus (10). Two S. Paratyphi A cases had evidence of AMR, and several E. coli cases were multidrug resistant (42.9%, 6/14) or monoresistant (14.3%, 2/14). Culture contamination was observed in 3.6% (37) cases. Molecular and serological assays identified etiological agents in participants having negative cultures, with 23.1% to 90% of cases being missed by blood cultures. Blood cultures are a valuable diagnostic tool for hospitalized patients presenting with fever. In Indonesia, pre-screening patients for the most common viral infections, such as dengue, influenza, and chikungunya viruses, would maximize the benefit to the patient while also conserving resources. Blood cultures should also be supplemented with advanced laboratory tests when available.

Blood Culture Utilization in the Hospital Setting: a Call for Diagnostic Stewardship

There has been significant progress in detection of bloodstream pathogens in recent decades with the development of more sensitive automated blood culture detection systems and the availability of rapid molecular tests for faster organism identification and detection of resistance genes. However, most blood cultures in clinical practice do not grow organisms, suggesting that suboptimal blood culture collection practices (e.g., suboptimal blood volume) or suboptimal selection of patients to culture (i.e., blood cultures ordered for patients with low likelihood of bacteremia) may be occurring. A national blood culture utilization benchmark does not exist, nor do specific guidelines on when blood cultures are appropriate or when blood cultures are of low value and waste resources. Studies evaluating the potential harm associated with excessive blood cultures have focused on blood culture contamination, which has been associated with significant increases in health care costs and negative consequences for patients related to exposure to unnecessary antibiotics and additional testing. Optimizing blood culture performance is important to ensure bloodstream infections (BSIs) are diagnosed while minimizing adverse events from overuse. In this review, we discuss key factors that influence blood culture performance, with a focus on the preanalytical phase, including technical aspects of the blood culture collection process and blood culture indications. We highlight areas for improvement and make recommendations to improve current blood culture practices among hospitalized patients.

Epidemiology and outcome of occult bacteremia in patients discharged from emergency departments or ambulatory units: one-year study

Microbiological diagnosis of bloodstream infection (BSI) is made several hours after blood culture sampling. This delay could be critical in ambulatory clinics, emergency departments, and hospital day care units, as the patient may be discharged prior to blood culture positivity. Our aim was to evaluate the clinical outcome (including the number of readmissions) of patients diagnosed with BSI after discharge. We prospectively included all adult patients with positive blood culture for BSI that was confirmed after discharge from our center (Grenoble-Alpes University Hospital) in 2016. Patients were contacted about their blood culture results, and their clinical status was controlled via an external consultation or their family physician, with hospital readmission if necessary. Clinical outcome, accuracy of initial diagnosis, microbiological epidemiology, and antibiotic prescription were assessed. In 2016, 1433 episodes of positive blood culture were detected in our hospital, with 50 (3.5%) occurring after patient discharge. Clinically relevant bacteria were determined in 32/50 cases (64%), while other positive blood culture results were considered to be contaminants. Clinical reevaluation was performed in 45 patients (90%). The diagnosis was changed during the clinical reassessment of 24/49 patients (49%). Antibiotics were prescribed prior to discharge for 24/50 patients (48%), modified during follow-up for 15/45 (33%), and initiated for 13/45 (29%) at the reevaluation. Overall, 24/45 (53%) patients were readmitted to hospital units after reevaluation. The clinical follow-up of patients with positive blood culture after discharge led to diagnostic changes and hospital readmission in around half of patients.

Impact of satellite blood culture on early diagnosis of sepsis

Background

The aim of this study was to assess whether satellite blood culture (SBC) can improve turnaround times, antibiotic switching, and patient prognosis, relative to laboratory blood culture (LBC).  .

Methods

Patients with sepsis treated in the intensive care units (ICUs) of Henan Provincial People's Hospital from February 5, 2018 to January 19, 2019 who met the inclusion criteria were recruited to the study and divided into the SBC group and LBC group according to different blood culture methods. Patient demographics, blood culture, antibiotic adjustment, and prognosis data were collected and compared between the two groups.  .

Results

A total of 204 blood culture sets from 52 ICU patients, including 100 from the medical microbiology LBC group and 104 from the SBC group, were analyzed in this study. There was no significant difference in the positive rates between the two groups. Time from specimen collection to incubation was significantly shorter in the SBC group than that in the LBC group (1.65 h vs. 3.51 h, z=-4.09, P<0.001). The median time from specimen collection to notification of blood culture positivity was 24.83 h in the SBC group and 27.83 h in the LBC group. Median times from adjustment of antibiotics according to the first report were 26.05 h and 51.71 h in the SBC and LBC groups, respectively, while those according to the final report were 97.17 h and 111.45 h, respectively. Median ICU lengths of stay were 15.00 days and 17.00 days in the SBC and LBC groups, respectively, and median ICU lengths of stay were 18.00 days and 23.50 days, respectively. Mean hospitalization costs were 157.99 and 186.73 thousand yuan in the SBC and LBC groups, respectively.  .

Conclusion

SBC can significantly reduce blood culture turnaround times; however, there were no significant differences between the two blood culture methods in initial reporting of positive cultures, time to adjustment of antibiotic therapy, or medical costs, despite a trend toward improvement.

Single-site sampling versus multi-site sampling for blood cultures; A retrospective clinical study

Objectives The performance of blood cultures (BC) relies on optimal sampling. Sepsis guidelines do not specify which sampling protocol to use, but recommend two sets of BC bottles, each set containing one aerobic and one anaerobic bottle. For the single-site sampling (SSS) protocol, only one venipuncture is performed for all four bottles. The predominating multi-site sampling (MSS) protocol implies that BC bottles are collected from two separate venipuncture sites. The aim of this study was to compare SSS and MSS. Primary outcomes were number of BC sets collected, sample volume and diagnostic performance. Methods This was a retrospective clinical study comparing BC results in an emergency department before and after changing the sampling protocol to SSS from MSS. All BC samples were incubated in the BacT/ALERT BC system. Results The analysis included 5,248 patients before and 5,364 patients after the implementation of SSS. There was a significantly higher proportion of positive BCs sampled with SSS compared to MSS, 1,049/5,364 (19.56%) and 932/5,248 (17.76%) respectively (P=0.018). This difference was due to a higher proportion of solitary BC sets (two BC bottles) in MSS. Analyzing only patients with the recommended four BC bottles, there was no difference in positivity. SSS had a higher proportion of BC bottles with the recommended sample volumes of 8-12 ml than MSS (P<0.001). Conclusions Changing the sampling protocol to SSS from MSS resulted in higher positivity rates, higher sample volume and fewer solitary BC sets. These advantages of SSS should be considered in future sepsis guidelines.

Accuracy of procalcitonin for diagnosing peripheral blood culture contamination among patients with positive blood culture for potential contaminants

PURPOSE

Blood culture contamination is still a frequently observed event and may lead to unnecessary antibiotic prescriptions and additional hazards and costs. However, in patients hospitalized in tertiary care, true bacteremias for pathogens that are classically considered as contaminants can be observed. We assessed the diagnostic accuracy of procalcitonin for differentiating blood culture contamination from bacteremia in patients with positive blood cultures for potential contaminants.

METHODS

We carried out a retrospective, cross-sectional, observational study on consecutive patients hospitalized between January 2016 and May 2019 at the University Hospital of Nancy and who had a positive peripheral blood culture for a pathogen classically considered as a potential contaminant.

RESULTS

During the study period, 156 patients were screened, and 154 were retained in the analysis. Among the variables that were significantly associated with a diagnosis of blood culture contamination in univariate analyses, four were maintained in multivariate logistic regression analysis: a number of positive blood culture bottles ≤ 2 (OR 23.76; 95% CI 1.94-291.12; P = 0.01), procalcitonin < 0.1 ng/mL (OR 14.88; 95% CI 1.62-136.47; P = 0.02), non-infection-related admission (OR 13.00; 95% CI 2.17-77.73; P = 0.005), and a percentage of positive blood culture bottles ≤ 25% (OR 12.15; 95% CI 2.02-73.15; P = 0.006).

CONCLUSIONS

These data provide new evidence on the usefulness of plasma procalcitonin as a reliable diagnostic biomarker in the diagnostic algorithm of peripheral blood culture contamination among patients hospitalized in tertiary care.

CLINICAL TRIAL

ClinicalTrials.gov #NCT04573894.

Impact of 24/7 loading of blood culture bottles in a new automated incubator on the diagnosis of bloodstream infections

Blood culturing (BC) remains the gold standard for bloodstream diagnosis but its workflow is slow. We aimed reducing this time by implementing a new automated incubator with a 24/7 BC workflow. With this new strategy, time to incubation was shorter (1.52 h vs 6.82 h), positivity rates were higher (10.6% vs 8.9%, p<0.05), and the number of BSI diagnostics increased (16.1% vs 13.8% patients and 2.3 vs 1.9 density episode per 1000 hospital days). Our results show that implementing automatic loading of BC bottles with a 24/7 strategy not only shortened time to diagnosis but significantly increased the BSI diagnosis rate.

Seasonal variations in blood culture numbers and time to positivity and potential impact of reducing incubation periods

Patients with viral respiratory infections often present symptoms compatible with bloodstream infections. Consequently, the winter period commonly associated with epidemic respiratory illnesses shows an increase in the number of blood cultures (BC) and to occasional saturation of automated BC systems. Here, we explored the seasonal variations in BC samples and the potential impact of shortening the incubation time of BC when automated BC systems are close to saturation. A retrospective study was conducted during a 3-year period in 4 hospitals located in the Paris region, France. All aerobic and anaerobic bottles were included, except pediatric bottles and those sampled for suspicion of endocarditis. The number of BC bottles collected during the winter period was compared to the annual baseline. All bottles positive after a 4-day incubation were analyzed regarding clinical and microbiological findings. The number of BC bottles was significantly higher during the winter periods, compared to the annual baseline (up to 14%). A total of 292,349 BC bottles were analyzed with 23,363 (8.0%) positive, including 236 (1%) after a 4-day incubation. Of these 236 bottles, 76 (64.8%) were positive with a contaminant, 78 (33.1%) with a clinically significant microorganism identified for the same patient in the previous 4 days, and only 5 (2.1%) with a clinically significant microorganism not previously identified. Winter periods were associated with a significant increase in BC samples. Shortening the incubation time of BC bottles from 5 to 4 days seems a relevant option when automated BC systems are close to saturation.

Factors associated with the risk of positive blood culture in neonatal foals presented to a referral center (2000-2014)

Background

Bloodstream infections (BSI) are common in sick foals and increase foal morbidity and mortality when they occur. Recognition of risk factors for BSI could be an important means to limit their occurrence, but studies on this topic are limited.

Objectives

Historical as well as maternal and foal physical examination findings will predict risk of BSI in neonatal foals.

Animals

Foals <14 days of age admitted to a referral equine hospital for care.

Methods

Retrospective case‐control study with univariate and multivariable logistic regression analysis.

Results

Four hundred twenty‐nine (143 cases and 286 controls) foals <14 days of age were studied. Risk of a foal having a BSI was increased in foals with umbilical disease (adjusted odds ratio [OR], 11.01; P = .02), hypoglycemia (adjusted OR, 13.51; P = .03), and the combined presence of umbilical disease and low hematocrit (adjusted OR, >999.99; P = .04). Factors not found to be risk factors for development of BSI included prematurity, hypothermia, abdominal disease, diarrhea, failure of passive transfer, and maternal uterine infection.

Conclusions and Clinical Importance

Several historical and physical examination findings increase the risk of foals being blood culture positive at presentation to the hospital. This knowledge may aid early identification of blood culture status, thus aiding in treatment decisions.

Collection, transport and storage procedures for blood culture specimens in adult patients: recommendations from a board of Italian experts

Bloodstream infections (BSIs) remain a potentially life-threatening condition. The gold standard for the diagnosis of BSI is still blood cultures (BCs), and the diagnostic yield depends on clinical and technical factors that have an impact on collection and transportation. Hence, monitoring of the entire pre-analytical process from blood collection to transportation to the microbiology laboratory is critical. To optimize the clinical impact of the diagnostic and therapeutic procedures, a multidisciplinary approach and univocal protocols are mandatory. A board of specialists discussed the available evidence on the pre-analytical process and produced the present document to guide physicians and nurses on the ideal execution of BC: (1) timing and preparation for blood collection; (2) skin antisepsis; (3) blood volume; (4) sampling method and safety; (5) medium to be used; (6) time to BC transportation; and (7) quality assurance and quality management.

Single-Sampling Strategy vs. Multi-Sampling Strategy for Blood Cultures in Sepsis: A Prospective Non-inferiority Study

Background

Optimal sampling is critical for the performance of blood cultures (BCs). Most guidelines recommend collecting 40 ml of blood, divided between two venipuncture sites, i.e., multi-sampling strategy (MSS). Sampling through a single venipuncture site, i.e., single-sampling strategy (SSS) is easier; however, the diagnostic performance of SSS compared to MSS remains unknown. Thus, we aimed to study if SSS is non-inferior to MSS for detection of pathogenic microorganisms.

Methods

A prospective, paired, non-inferiority design was used. Patients with clinically suspected sepsis admitted to an Emergency Department were included. Six BC bottles were simultaneously collected, consisting of four BC bottles from the first arm and two from the other arm. SSS consisted of BC bottles 1, 2, 3, and 4, and MSS consisted of BC bottles 1, 2, 5, and 6. Samples were incubated in a BacT/ALERT BC system.

Results

The final analysis included 549 episodes. Pathogenic microorganisms were detected in 162 cases (29.5%) with MSS and 160 cases (29.1%) with SSS, yielding an absolute difference of 0.36%, with a 95% confidence interval of -1.33 to 2.06%, which did not exceed the predefined non-inferiority margin of 5%. MSS tended to produce more contaminant growth (7.3% of cases) than SSS (5.3% of cases; p = 0.072).

Conclusion

The study showed that SSS was non-inferior to MSS in detecting pathogenic microorganisms and supports the use of SSS as a routine method.

Blood culture contamination in the emergency department: An integrative review of strategies to prevent blood culture contamination

BACKGROUND

Blood culture collection remains the gold standard to diagnose bacteraemia. Current evidence suggests that the emergency department (ED) often has blood culture contamination (BCC) rates above the recommended 3%, contributing to increased hospital length of stay, unnecessary or inappropriate antimicrobial treatment, and increased economic burden. The aim of this review is to identify effective strategies to improve blood culture collection in EDs to decrease contamination rates and improve patient safety.

METHODS

An integrative literature review methodology was utilised to conduct a structured search of contemporary literature using CINAHL, Embase, Medline, Pubmed and Scopus databases. All eligible literature was screened with those included in the final review collated and appraised using a quality assessment tool.

RESULTS

Eleven reports were included in the final review, which identified bundled approaches, education and feedback, equipment and technique, and stakeholder engagement as strategies that improve BCC rates in the ED.

CONCLUSIONS

All studies reported a reduction in BCC rates regardless of the strategies implemented. A bundled approach yielded the most significant results and was identified to be practical, inexpensive, and adaptable. Further research focusing on specific aspects of a bundled approach may be beneficial to understand which strategies are most effective.

Utility of anaerobic bottles for the diagnosis of bloodstream infections

BACKGROUND

Obligate anaerobes usually account for less than 10% of bacteria recovered from blood cultures (BC). The relevance of routine use of the anaerobic bottle is under debate. The aim of this study was to evaluate the utility of anaerobic bottles for the diagnosis of bloodstream infections (BSI).

METHODS

We conducted a 6-month, retrospective, monocentric study in a tertiary hospital. All positive BC were grouped into a single episode of bacteremia when drawn within 7 consecutive days. Bacteremia were classified into contaminants and BSI. Charts of patients with BSI due to obligate anaerobes were studied.

RESULTS

A total of 19,739 blood cultures were collected, 2341 of which (11.9%) were positive. Anaerobic bottles were positive in 1528 (65.3%) of all positive BC but were positive alone (aerobic bottles negative) in 369 (15.8%). Overall 1081 episodes of bacteremia were identified, of which 209 (19.3%) had positive anaerobic bottles alone. The majority 126/209 (60.3%) were contaminants and 83 (39.7%) were BSI. BSI due to facultative anaerobes, obligate aerobes and obligate anaerobes were identified in 67 (80.7%), 3 (3.6%) and 13 (15.7%) of these 83 episodes, respectively. BSI due to obligate anaerobic bacteria were reported in 9 patients with gastro-intestinal disease, in 3 with febrile neutropenia and in 1 burned patient.

CONCLUSIONS

Anaerobic bottles contributed to the diagnosis of a significant number of episodes of bacteremia. Isolated bacteria were mostly contaminants and non-obligate anaerobic pathogens. Rare BSI due to obligate anaerobes were reported mainly in patients with gastro-intestinal disorders and during febrile neutropenia.

Strategies for increasing diagnostic yield of community-onset bacteraemia within the emergency department: A retrospective study

Bloodstream infections (BSI) are associated with high mortality. Therefore, reliable methods of detection are of paramount importance. Efficient strategies to improve diagnostic yield of bacteraemia within the emergency department (ED) are needed. We conducted a retrospective analysis of all ED encounters in a high-volume, city-centre university hospital within Germany during a five-year study period from October 2013 to September 2018. A time-series analysis was conducted for all ED encounters in which blood cultures (BCs) were collected. BC detection rates and diagnostic yield of community-onset bacteraemia were compared during the study period (which included 45 months prior to the start of a new diagnostic Antibiotic Stewardship (ABS) bundle and 15 months following its implementation). BCs were obtained from 5,191 out of 66,879 ED admissions (7.8%). Bacteraemia was detected in 1,013 encounters (19.5% of encounters where BCs were obtained). The overall yield of true bacteraemia (defined as yielding clinically relevant pathogens) was 14.4%. The new ABS-related diagnostic protocol resulted in an increased number of hospitalised patients with BCs collected in the ED (18% compared to 12.3%) and a significant increase in patients with two or more BC sets taken (59% compared to 25.4%), which resulted in an improved detection rate of true bacteraemia (2.5% versus 1.8% of hospital admissions) without any decrease in diagnostic yield. This simultaneous increase in BC rates without degradation of yield was a valuable finding that indicated success of this strategy. Thus, implementation of the new diagnostic ABS bundle within the ED, which included the presence of a skilled infectious disease (ID) team focused on obtaining BCs, appeared to be a valuable tool for the accurate and timely detection of community-onset bacteraemia.

Best Practices of Blood Cultures in Low- and Middle-Income Countries

Bloodstream infections (BSI) have a substantial impact on morbidity and mortality worldwide. Despite scarcity of data from many low- and middle-income countries (LMICs), there is increasing awareness of the importance of BSI in these countries. For example, it is estimated that the global mortality of non-typhoidal Salmonella bloodstream infection in children under 5 already exceeds that of malaria. Reliable and accurate diagnosis of these infections is therefore of utmost importance. Blood cultures are the reference method for diagnosis of BSI. LMICs face many challenges when implementing blood cultures, due to financial, logistical, and infrastructure-related constraints. This review aims to provide an overview of the state-of-the-art of sampling and processing of blood cultures, with emphasis on its use in LMICs. Laboratory processing of blood cultures is relatively straightforward and can be done without the need for expensive and complicated equipment. Automates for incubation and growth monitoring have become the standard in high-income countries (HICs), but they are still too expensive and not sufficiently robust for imminent implementation in most LMICs. Therefore, this review focuses on "manual" methods of blood culture, not involving automated equipment. In manual blood cultures, a bottle consisting of a broth medium supporting bacterial growth is incubated in a normal incubator and inspected daily for signs of growth. The collection of blood for blood culture is a crucial step in the process, as the sensitivity of blood cultures depends on the volume sampled; furthermore, contamination of the blood culture (accidental inoculation of environmental and skin bacteria) can be avoided by appropriate antisepsis. In this review, we give recommendations regarding appropriate blood culture sampling and processing in LMICs. We present feasible methods to detect and speed up growth and discuss some challenges in implementing blood cultures in LMICs, such as the biosafety aspects, supply chain and waste management.

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

BACKGROUND

Blood culture contamination (BCC) increases length of stay (LOS) and leads to unnecessary antimicrobial therapy and/or hospital-acquired conditions (HACs).

AIM

To quantify the magnitude of additional LOS, costs to hospitals and society, and harm to patients attributable to BCC.

METHODS

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.

FINDINGS

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.

CONCLUSION

Costs and clinical burdens associated with false-positive cultures are substantial and can be reduced by available interventions, including phlebotomists and use of ISDD.

How to: accreditation of blood cultures' proceedings. A clinical microbiology approach for adding value to patient care

BACKGROUND

Quality assurance and quality management are driving forces for controlling blood culture best practices but should not be disconnected from the end-point target, i.e. patient value.

AIMS

This article is intended to help microbiologists implement blood culture accreditation that is actually beneficial to patient management.

SOURCES

Experience from a nationwide taskforce for promoting quality assurance and competence in clinical microbiology laboratories, guidelines on blood culture.

CONTENT

Experience in blood culture accreditation according to International standard ISO 15189 standards is provided in this review, with a particular focus on critical points that are specific to blood culture (e.g. excluding strain identification or antimicrobial susceptibility testing). Blood culture test method verification is based on risk analysis, and evaluation of the test method's performance is based on the literature review and suppliers' data. In addition, blood culture performance relies largely on the quality of its pre-analytical phase, and the test method should be monitored based on key performance indicators such as the volume of blood cultured, the contamination rate and time to transportation. Other critical key indicators include the rate of false-positive signals, the rate of positive blood cultures, the ecology associated with positive results, and the timely communication of the results to the ward during the post-analytical phase. Finally, a critical analysis of quality controls and of the tools needed to improve blood culture monitoring in the future is provided.

IMPLICATION

Appropriate quality assurance should focus on patient value rather than technical details to provide an appropriate clinical service.

A Quality Improvement Initiative to Decrease the Rate of Solitary Blood Cultures in the Emergency Department

OBJECTIVES

Best practice guidelines recommend that at least two sets of blood cultures (BCs) be sent when blood cultures are required. However, high rates of solitary BCs are still common in the emergency department (ED). The aim of this study was to evaluate the efficacy of different quality improvement initiatives aimed at reducing the rate of solitary blood cultures being sent to the laboratory on patients ultimately discharged from our ED.

METHODS

This was a multicenter, multiphase, prospective study evaluating a comprehensive education-based intervention and a second intervention that combined a computerized forcing function (FF) along with a brief education-based intervention. The results were analyzed using segmented regression analysis, as well as statistical process control charts.

RESULTS

The baseline rate of solitary sets of BCs was 41.1%. The education intervention reduced this rate to 30.3%. The introduction of a FF with a brief educational intervention further reduced the rate to 11.6%. This represents an absolute reduction of 29.5% from baseline (relative reduction of 71.8%). According to segmental regression analyses, the education intervention alone did not produce a statistically significant change when factoring possible background time-related trends (p = 0.071). However, the FF produced a statistically significant improvement (p < 0.0005), which was maintained for 6 months.

CONCLUSION

The combination of a brief education-based intervention and a computerized FF was more effective than education alone in reducing solitary BC collection in our ED in this time series study. FFs can be a powerful tool in modifying behaviors and processes in the clinical setting.

Usefulness of daily surveillance blood cultures in allogeneic hematopoietic stem cell transplant recipients on steroids: a 1-year prospective study

BACKGROUND

Bloodstream infections (BSI) are frequent and potentially severe complications in allogeneic hematopoietic stem cell transplant (AHSCT) recipients. In patients on steroids, surveillance blood cultures (SBCs) are routinely performed to detect asymptomatic BSI but their usefulness remains controversial.

METHODS

We performed a 1-year, observational, prospective, single-center study to assess the utility of daily SBCs in AHSCT recipients on steroids and a case-control study to identify risk factors associated with positive SBCs. All blood cultures (BCs) obtained from adults hospitalized in the HSCT unit were prospectively studied throughout 1 year. Characteristics, treatments, and outcome of patients were retrieved from medical charts.

RESULTS

A total of 3594 BCs were obtained in 177 patients, including 1450 SBCs in 82 AHSCT recipients on steroids. In 33 patients, 103 SBCs (7%) were positive. Low-virulence bacteria were identified in 74% of episodes. When analyzing first episode of positive SBCs (28 patients), 6 (21%) true BSI were identified.

CONCLUSIONS

Patients with positive SBCs were receiving antibiotic treatment less frequently at the time of SBCs (P < 0.001) and had more frequently BCs obtained through central venous access (P < 0.04) when compared to patients with negative SBCs. Daily SBCs in AHSCT recipients on steroids only rarely identify BSI and clear benefit for patients could not be demonstrated.

How to Optimize the Use of Blood Cultures for the Diagnosis of Bloodstream Infections? A State-of-the Art

Bloodstream infection (BSI) is a major cause of death in developed countries and the detection of microorganisms is essential in managing patients. Despite major progress has been made to improve identification of microorganisms, blood culture (BC) remains the gold standard and the first line tool for detecting BSIs. Consensus guidelines are available to ensure optimal BSI procedures, but BC practices often deviate from the recommendations. This review provides an update on clinical and technical issues related to blood collection and to BC performance, with a special focus on the blood sample strategy to optimize the sensitivity and specificity of BCs.

Relevance of blood cultures in acute pyelonephritis in a single-center retrospective study

Pyelonephritides are frequently encountered diagnosis in Emergency Departments. Urinalyses have a central place in the management of this situation but the usefulness of blood cultures is not clear. We conducted a single-center retrospective study of 24 months to study the microbiological relevance of blood cultures in pyelonephritis. We included patients with blood cultures (BC) and urine cultures (UC) drawn at the same time, if they were not exposed to antibiotics prior to these tests. Of our 264 patients, 39 (15 %) had no bacteriological documentation. There were 83 (31 %) bacteremic patients. Seven patients had contaminated or sterile UC with positive BC. Four patients had positive UC and BC with the latter allowing identification of a pathogen absent from the UC (n = 1) or identifying the main pathogen in three cases. A total of 11 patients theoretically benefited from BC representing 4.2 % of our population. Excluding one patient who was known to be infected with multi-drug resistant bacteria, all empirical antibiotics regimens were effective against the identified pathogens. We did not reveal any significant therapeutic impact of blood cultures in the management of pyelonephritis, when BC and UC are performed before any antimicrobials treatment.