Minimizing the workup of blood culture contaminants: implementation and evaluation of a laboratory-based algorithm

Laboratory approaches to determining blood culture contamination rates: an ASM Laboratory Practices Subcommittee report

Blood culture contamination (BCC) is the presence of specific commensal and environmental organisms cultivated from a single blood culture set out of a blood culture series and that do not represent true bacteremia. BCC can impact quality of care and lead to negative outcomes, unnecessary antibiotic exposure, prolonged hospital stays, and substantial costs. As part of the laboratory's quality management plan, microbiology laboratory personnel are tasked with monitoring BCC rates, preparing BCC rate reports, and providing feedback to the appropriate committees within their healthcare system. The BCC rate is calculated by the laboratory using pre-set criteria. However, pre-set criteria are not universally defined and depend on the individual institution's patient population and practices. This mini-review provides practical recommendations on elaborating BCC rate reports, the parameters to define for the pre-set criteria, how to collect and interpret the data, and additional analysis to include in a BCC report.

[Study of the growth temperature of ocular surface microorganisms in norm and in infectious keratitis]

Standard bacteriological examinations, which involve culturing microorganisms at 37 °C, are commonly used in clinical practice for diagnosing infectious diseases. However, the growth temperature of microorganisms on the ocular surface (OS) during infectious keratitis (IK) may not coincide with the laboratory standard, which is due to the characteristic features of heat exchange in the eye.

PURPOSE

This exploratory study examines the distribution and properties of OS microorganisms isolated under different temperature cultivation conditions in patients with IK and healthy volunteers without ophthalmic pathology.

MATERIAL AND METHODS

Fifteen participants were divided into two groups. Group 1 (n=10) consisted of patients with signs of unilateral infectious keratitis, while group 2 (n=5) served as the control group. A novel microbiological method was employed to isolate pure cultures of microorganisms. This method involved cultivating microorganisms at two temperature regimes (37 °C and 24 °C) and subsequently identifying them using biochemical, immunological, and physicochemical techniques, including mass spectrometry. Scanning electron microscopy (SEM) with lanthanide staining used as the reference method. The temperature status of the ocular surface was assessed using non-contact infrared thermography.

RESULTS

The study demonstrated the presence of psychrotolerant microorganisms on the ocular surface, which exhibited growth at a relatively low temperature of 24 °C. These psychrotolerant microorganisms were found to be isolated from the ocular surface displaying signs of temperature dysregulation. Among such microorganisms are Acinetobacter lwoffii, Achromobacter xylosoxidans, Bacillus licheniformis, Enterococcus faecalis, Klebsiella oxytoca, Klebsiella pneumoniae, Micrococcus luteus, Pseudomonas luteola, Streptococcus spp.

CONCLUSION

When identifying the causative agent of infectious keratitis, it is crucial to consider the divergence of growth temperature of ocular surface microorganisms. The presence of psychrotolerant microorganisms on the ocular surface, which can effectively grow at room temperature, should be taken into account, especially in cases of temperature dysregulation.

Development and validation of a standardized blood culture contamination definition and metric dashboard for a large health care system

OBJECTIVES

Blood culture contamination is a major problem in health care, with significant impacts on both patient safety and cost. Initiatives to reduce blood culture contamination require a reliable, consistent metric to track the success of interventions. The objective of our project was to establish a standardized definition of blood culture contamination suitable for use in a Veterans Health Administration (VHA) national data query, then to validate this definition and query. A secondary objective was to construct a national VHA data dashboard to display the data from this query that could be used in VHA quality improvement projects aimed at reducing blood culture contamination.

METHODS

A VHA microbiology expert work group was formed to generate a standardized definition and oversee the validation studies. The standardized definition was used to generate data for calendar year 2021 using a Structured Query Language data query. Twelve VHA hospital microbiology laboratories compared the data from the query against their own locally derived contamination data and recorded those data in a data collection worksheet that all sites used. Data were collated and presented to the work group.

RESULTS

More than 50,000 blood culture accessions were in the validation data set, with more than 1,200 contamination events. The overall blood culture contamination rate for the 12 facilities participating was 2.56% with local definitions and data and 2.43% with the standardized definitions and data query. The main differences noted between the 2 data sets were deemed to be issues in local definitions. The query and definition were then converted into a national data dashboard that all VHA facilities can now access.

CONCLUSIONS

A standardized definition for blood culture contamination and a national data query were validated for enterprise-wide VHA use. To our knowledge, this represents the first reported standardized, validated, and automated approach for calculating and tracking blood culture contamination. This tool will be key in quality initiatives aimed at reducing contamination events in VHA.

Performance of presepsin and procalcitonin predicting culture-proven bacterial infection and 28-day mortality: A cross sectional study

Presepsin is a highly specific biomarker for diagnosing bacterial infections, but its clinical usefulness is not well validated. A retrospective cross-sectional study was conducted. Among the patients suspected bacterial infection or fulfilled the criteria of systemic inflammatory response syndrome (SIRS) and patients who underwent blood culture, presepsin, procalcitonin (PCT), and C-reactive protein (CRP) at the same time were included. Receiver operating characteristic (ROC) curve analysis and logistic regression were used to compare performance of three biomarkers. A total of 757 patients were enrolled, including 256 patients (33.8%) with culture-proven bacterial infection and 109 patients (14.4%) with bacteremia. The 28-day mortality rate was 8.6%. ROC curve analysis revealed that the area under the curve (AUC) of PCT was higher than that of presepsin for both culture-proven bacterial infection (0.665 and 0.596, respectively; p = 0.003) and bacteremia (0.791 and 0.685; p < 0.001). In contrast, AUC of PCT for 28-day mortality was slower than presepsin (0.593 and 0.720; p = 0.002). In multivariable logistic regression analysis, PCT showed the highest ORs for culture-proven bacterial infection (OR 2.23, 95% CI 1.55–3.19; p < 0.001) and for bacteremia (OR 5.18, 95% CI 3.13–8.56; p < 0.001), while presepsin showed the highest OR for 28-day mortality (OR 3.31, 95% CI 1.67–6.54; p < 0.001). CRP did not show better performance than PCT or presepsin in any of the analyses. PCT showed the best performance predicting culture-proven bacterial infection and bacteremia, while presepsin would rather be useful as a prognostic marker.

Clinico-bacterial and prognostic factors in patients with suspected blood stream infection and elevated serum procalcitonin levels

This study determined prognostic factors by comparing clinico-bacterial factors based on significant elevated serum procalcitonin levels in patients with suspected bloodstream infection (BSI). We retrospectively analyzed the medical records of 1,052 patients (age ≥16 years) with fever (temperature ≥38°C) and serum procalcitonin levels of ≥2.0 ng/mL, and blood culture results. The optimal cutoff value of the significant elevation of procalcitonin was determined using the minimum P-value approach. Clinico-bacterial factors were analyzed per the procalcitonin levels, and significant independent factors for short-term survival were investigated in 445 patients with BSI. Patients with suspected BSI were aged, on average, 72.3 ± 15.1 years, and the incidence of positive blood culture was 42.3%; and the 14-day survival was 83.4%. Procalcitonin ≥100 ng/mL was the most significant predictor for survival. Multivariate analysis in patients with suspected BSI showed that estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m² and procalcitonin ≥100 ng/mL were significant independent unfavorable prognostic factors. Microorganisms were similar between patients with procalcitonin level 2-99 ng/mL (n=359) and those with ≥100 ng/mL (n=86). Multivariate analysis in patients with BSI showed that eGFR <30 mL/min/1.73 m², procalcitonin ≥100 ng/mL, and primary infectious foci were significant independent prognostic factors. Patients with foci in the gastrointestinal tract and respiratory system had unfavorable 14-day survival. In conclusions, eGFR <30 mL/min/1.73 m² and procalcitonin ≥100 ng/mL were significant independent unfavorable prognostic factors for suspected BSI. Primary infectious foci (gastrointestinal tract and respiratory system) were associated with unfavorable short-term survival in patients with positive blood culture.

Comparing blood culture contamination rates by different sampling methods in a paediatric emergency department

AIM

Blood culture contamination (BCC) can cause unnecessary hospitalisations and inappropriate use of antibiotics. The aim of this study was to find risk factors associated with BCCs in children and to compare contamination rates between open and closed blood culture collection systems.

METHODS

Data were prospectively collected regarding blood cultures obtained in the paediatric emergency department from February 26, 2020, to September 30, 2020, based on the method of drawing blood reported by the obtaining physician. A comparison between contaminated and non-contaminated blood cultures was performed. We also compared the composition of the contaminations in the study period to the same period in 2019.

RESULTS

A total of 512 blood cultures were included, 33 (6.4%) of which were contaminated. The only parameter that was associated with an increased rate of contamination by 2.34 fold (95% CI 1.1-4.99, P = 0.028) was obtaining blood through an 'open' system, using a syringe connected to a needle in order to draw blood from an open ended needle. The proportion of contaminations originating from oral flora decreased in the study period by 44.7% as compared to the same period in the previous year (13% vs. 23.5%, P = 0.056).

CONCLUSIONS

'Open system' method, which is commonly used in paediatric emergency departments for blood culture obtainment, was associated with an increase in BCC. Adherence to blood cultures obtainment guidelines, even at the price of two different blood tests, is important in order to reduce BCC rates in children.

Blood Culture Contamination: A Single General Hospital Experience of 2-Year Retrospective Study

In the event of blood culture contamination (BCC), blood culture (BC) needs to be repeated. This may delay appropriate treatment, prolong hospitalization and, consequently, increase its costs. The aim of the study was to assess the frequency of BCC and associated factors in a general hospital in Poland based on reports of BC in samples submitted for laboratory testing in 2019−2020. BCC is recognized when bacteria (especially those belonging to natural human microbiota) are isolated from a single sample and no clinical signs indicated infection. True positive BC is confirmed by the growth of bacteria in more than one set of blood samples with the corresponding clinical signs present. The structure of BC sets, microorganisms, and laboratory costs of BCC were analyzed. Out of 2274 total BC cases, 11.5% were true positive BC and 9.5% were BCC. Of all the BCC identified in the entire hospital, 72% was from Internal Medicine (IM) and Intensive Care Unit (ICU) combined. When single sets for BC were used in IM in 2020, the use increased to 85% compared with 2019 (p < 0.05). The predominant isolates were coagulase-negative staphylococci (84%). The estimated extra laboratory costs of BCC exceeded EUR 268,000. The BCC was a more serious problem than expected, including non-recommended using of single BC sets. Compliance with the BC collection procedure should be increased in order to reduce BCC and thus extra hospital costs.

Initial Specimen Diversion Device® Reduces Blood Culture Contamination and Vancomycin Use in Academic Medical Center

BACKGROUND

In suspected bloodstream infections, accurate blood culture results are critical to timely diagnoses and appropriate antibiotic administration.

AIM

An Initial Specimen Diversion Device®, Steripath®, (Magnolia Medical Technologies, Seattle, WA) was evaluated for efficacy in reducing blood culture contamination at Brooke Army Medical Center (6.8% six-month contamination rate prior to intervention) in a six-month quality improvement project.

METHODS

Blood cultures in the emergency department were collected using either Steripath® or the standard method. 20 mL of blood was cultured into an aerobic and anaerobic medium and incubated for five days using an automated microbial detection system immediately after collection. Positive bottles were Gram stained and plated. Rapid molecular PCR identification was performed on all first positive bottles within a blood culture set for each admission or ED visit. Speciation was deduced during antimicrobial sensitivity testing using the Vitek-2 instrument.

FINDINGS

Seven (7/1016, 0.69%) contamination events occurred when using Steripath® vs. 53 (53/800, 6.6%) contamination events when using the standard method. Steripath® use was associated with a 90% lower incidence of blood culture contamination vs. the standard method. Post-study, Steripath® use was implemented as standard practice hospital-wide, and a retrospective data analysis attributed a 31.4% decrease in vancomycin days of therapy to Steripath® adoption.

CONCLUSION

Using Steripath® significantly decreased blood culture contamination events for bacterial bloodstream infections compared to the standard method. Subsequent adoption of Steripath® reduced overall vancomycin usage. With widescale implementation Steripath® could bolster antibiotic stewardship, mitigating antibiotic resistance caused by unnecessary antibacterial treatments.

Bacterial Etiology of Bloodstream Infections and Antimicrobial Resistance Patterns from a Tertiary Care Hospital in Malé, Maldives

Background

Bloodstream infections pose a significant health problem worldwide and is a major cause of morbidity and mortality in many countries. It is important to have country-specific data for major pathogens causing bloodstream infections, in light of emerging resistance patterns of common bacterial isolates. Due to the scarcity of reports in this area, the aim of this study was to identify bacterial pathogens causing bloodstream infections among the study population.

Methods

A retrospective analysis of blood culture samples received at the Department of Laboratory Medicine, Indira Gandhi Memorial Hospital, Malé, Maldives, was performed for reports between January 2016 and December 2017.

Results

Out of the 471 culture-positive samples, 278 (59%) were males and 193 (41%) were females. Amongst the culture-positive samples, 338 (71.8%) Gram-positive organisms were isolated and 133 (28.2%) Gram-negative organisms were isolated. Coagulase-negative Staphylococcus (CoNS) was the most frequently isolated blood-borne bacterial pathogen in this study, accounting for 53.6% and 50.9% of the isolates in 2016 and 2017, respectively. Other frequently isolated pathogens included Staphylococcus aureus (15.9% and 10.3%), Klebsiella spp. (10.5% and 16.4%), and Escherichia coli (7.1% and 10.8%). Coagulase-negative Staphylococcus (CoNS) revealed high percentage of resistance among the tested antimicrobials, ampicillin, cephalexin, cefotaxime, and gentamicin. Over the two years, a significant difference between the percentage resistance among paediatric and adult patients was observed for coagulase-negative Staphylococcus (CoNS) isolate resistance to ampicillin (p ≤ 0.001), cephalexin (p ≤ 0.001), cefotaxime (p ≤ 0.001), gentamicin (p=0.008), and cotrimoxazole (SXT) (p ≤ 0.001). When comparing the significant antimicrobial resistance trends, it can be seen that Enterobacteriaceae isolates also demonstrated high resistance to ampicillin and gentamicin as well as second- and third-generation cephalosporins.

Conclusions

This study highlights the major bacterial pathogens involved in bloodstream infections in the healthcare setting of Malé, Maldives, and antibiotic resistance patterns. The results indicate that further characterization of bacteremia and its resistance patterns is needed to combat bloodstream infections.

Using Clinical History Factors to Identify Bacterial Infections in Young Febrile Infants

OBJECTIVE

To develop a novel predictive model using primarily clinical history factors and compare performance to the widely used Rochester Low Risk (RLR) model.

STUDY DESIGN

In this cross-sectional study, we identified infants brought to one pediatric emergency department from January 2014 to December 2016. We included infants age 0-90 days, with temperature ≥38°C, and documented gestational age and illness duration. The primary outcome was bacterial infection. We used 10 predictors to develop regression and ensemble machine learning models, which we trained and tested using 10-fold cross-validation. We compared areas under the curve (AUCs), sensitivities, and specificities of the RLR, regression, and ensemble models.

RESULTS

Of 877 infants, 67 had a bacterial infection (7.6%). The AUCs of the RLR, regression, and ensemble models were 0.776 (95% CI 0.746, 0.807), 0.945 (0.913, 0.977), and 0.956 (0.935, 0.975), respectively. Using a bacterial infection risk threshold of .01, the sensitivity and specificity of the regression model was 94.6% (87.4%, 100%) and 74.5% (62.4%, 85.4%), compared with 95.5% (87.5%, 99.1%) and 59.6% (56.2%, 63.0%) using the RLR model.

CONCLUSIONS

Compared with the RLR model, sensitivities of the novel predictive models were similar whereas AUCs and specificities were significantly greater. If externally validated, these models, by producing an individualized bacterial infection risk estimate, may offer a targeted approach to young febrile infants that is noninvasive and inexpensive.

Quality indicators for blood culture: 1 year of monitoring with BacT/Alert Virtuo at a French hospital

Introduction. Blood culture (BC) remains the gold standard for the diagnosis of bloodstream infection. Clinical microbiology laboratories must ensure the quality of their BC process from receipt to definitive results.Aim. In this study, we followed the evolution of different quality indicators for BCs over the first year of implementation of the BacT/Alert Virtuo system in a French hospital.Methodology. In our laboratory, we instituted regular monitoring of several quality indicators to track (i) delays in sample registration, (ii) delays in loading BC bottles in our incubating system (BacT/Alert Virtuo) after registration, (iii) the volume of blood in bottles and (iv) the contamination rates.Results. For 53 892 BC bottles loaded in the BacT/Alert Virtuo from 23 January to 31 December 2019, the delays in sample registration, loading and unloading were respectively 3.5 h±0.016, 44 min±0.209 and 5.8 h±0.0727. Intriguingly, the automated process performed by the BacT/Alert Virtuo system to check the blood volume in bottles was only performed for 60 % of the loaded bottles. Among these, 30 % contained the recommended volume of blood (between 7 and 13 ml). Finally, the contamination rate was found to be 27.2 % for samples at our institution.Conclusions. The delays in sample registration, loading and unloading were found to be acceptable, even though they could be improved by ensuring a continuous service during the night duty period. Furthermore, the percentage of volumes measured is insufficient and must be improved and the majority of bottles do not contain the recommended blood volume.

Blood culture quality assurance: what Australasian laboratories are measuring and opportunities for improvement

Blood cultures are among the most important specimen types received and processed by the microbiology laboratory. Several publications list which variables should be measured to ensure quality. We undertook a qualitative structured questionnaire of Australian and New Zealand clinical microbiology laboratories to document current blood culture practices and to determine whether expected quality standards are being met. Questions included a wide range of pre-analytical, analytical, and post-analytical aspects of blood cultures from adults. The responses from 71 laboratories were analysed. Compliance was high for use of a biological safety cabinet (90%), incubating for 5 days (86%), and commenting on likely contaminants (85%). While Gram stains were reported within 2 hours during normal hours (93%), reporting was slower after hours (59%), p<0.001. The volume of blood collected for a clinical episode was poorly monitored with only 11% (n=8) of laboratories regularly auditing the number of blood culture sets and 3% (n=2) monitoring adequacy of fill. Most laboratories received blood cultures from off-site with just 34% (n=21) meeting guidance for loading bottles onto the analyser within 4 hours. More laboratories met standards for loading bottles onto the analyser during working hours than after hours: 87% vs 56%, p<0.001. Most laboratories did not monitor the contamination rate, 56% (n=40), and only 27% (n=19) knew their rate was below the guidance threshold of less than -3%. Considerable opportunities exist to improve quality assurance of blood culture practice in Australia and New Zealand, especially for the most critical aspect affecting culture sensitivity, the volume of blood collected.

Collaborative Antimicrobial Stewardship in the Emergency Department

Given the large number of patients seen in the emergency department (ED) and concerns with antibiotic overprescribing, the ED is an important setting to target for antimicrobial stewardship (AS) initiatives. The ED is positioned between ambulatory and inpatient settings, making AS collaboration with clinicians and other health care providers in the hospital, long-term care facilities, and ambulatory settings critical to success. This article details ED-focused AS strategies on empiric antimicrobial selection, prompt administration, preventing ED return and readmissions, suggested collaborations between ED AS leadership and other key partners, and potential future strategies for expansion.

[Optimization of microbial diagnostics by introduction of a blood culture standard operating procedure in the emergency department]

INTRODUCTION

The emergency department (ED) is the main port of entry for patients with infectious diseases, the place where a number of diagnostic procedures are performed and treatment is often initiated. The aim of this retrospective study was to estimate the influence of the establishment and introduction of a blood culture standard operating procedure (BC-SOP) and of the subsequent training of microbial diagnostics in an ED.

METHODS

In a before and after study over a study period of 3 months each (November 2017-January 2018 and November 2018-January 2019), the number of blood cultures taken, the rate of blood cultures per 1000 patients, the number of positive blood cultures and the frequency of typical skin pathogens were evaluated. In the interim time between the two study periods, a BC-SOP was developed in collaboration with the hospital's antibiotic stewardship team and subsequently introduced with staff training in the ED. The study was approved by the local ethics committee of the medical faculty of the Heinrich Heine University (2019-392-RetroDEuA).

RESULTS

In total 92% of the nursing personnel and 93% of the medical personnel received training. The total number of blood cultures increased from 1757 to 2872 (64% increase) and the rate of blood cultures per 1000 patients from 287 to 481 (68% increase). The number of positive blood cultures decreased from 18.6% to 13.7% (p < 0.05). Typical skin pathogens were found in 34.4% and 26.4% of the cases, respectively (p < 0.05).

CONCLUSION

The development, introduction and training of a BC-SOP in the ED can make a relevant contribution to the microbial diagnostics and increase the quantity as well as the quality.

Association of Systemic Inflammatory Response Syndrome with Bacteremia in Patients with Sepsis

The aim of this study was to evaluate the usability of systemic inflammatory response syndrome (SIRS) and commonly used biochemical parameters as predictors for positive blood culture in patients with sepsis. The study included 313 patients aged ≥18 years with severe sepsis and septic shock consecutively admitted in the Intensive Care Unit (ICU) of the University Clinic for Infectious Diseases in Skopje, Republic of North Macedonia. The study took place from January 1, 2011 to December 31, 2017. We recorded demographic variables, common laboratory tests, SIRS parameters, site of infection, comorbidities and Sequential Organ Failure Assessment (SOFA) score. Blood cultures were positive in 65 (20.8%) patients with sepsis. Gram-positive bacteria were isolated from 35 (53.8%) patients. From the evaluated variables in this study, only the presence of four SIRS parameters was associated with bacteremia, finding that will help to predict bacteremia and initiate early appropriate therapy in septic patients.

Practical Guidance for Clinical Microbiology Laboratories: A Comprehensive Update on the Problem of Blood Culture Contamination and a Discussion of Methods for Addressing the Problem

In this review, we present a comprehensive discussion of matters related to the problem of blood culture contamination. Issues addressed include the scope and magnitude of the problem, the bacteria most often recognized as contaminants, the impact of blood culture contamination on clinical microbiology laboratory function, the economic and clinical ramifications of contamination, and, perhaps most importantly, a systematic discussion of solutions to the problem. We conclude by providing a series of unanswered questions that pertain to this important issue.

Clinical Significance of Isolates Known to Be Blood Culture Contaminants in Pediatric Patients

Background and objectives: The objective of this study was to investigate the clinical significance of isolates from blood stream infection known to be blood culture contaminants in pediatric patients. Materials and Methods: Microbiological reports and medical records of all blood culture tests issued from 2002 to 2012 (n = 76,331) were retrospectively reviewed. Evaluation for potential contaminants were done by reviewing medical records of patients with the following isolates: coagulase-negative Staphylococcus, viridans group Streptococcus, Bacillus, Corynebacterium, Micrococcus, Aerococcus, and Proprionibacterium species. Repeated cultures with same isolates were considered as a single case. Cases were evaluated for their status as a pathogen. Results: Coagulase-negative Staphylococcus had clinical significance in 23.8% of all cases. Its rate of being a true pathogen was particularly high in patients with malignancy (43.7%). Viridans group Streptococcus showed clinical significance in 46.2% of all cases. Its rate of being a true pathogen was similar regardless of the underlying morbidity of the patient. The rate of being a true pathogens for remaining isolates was 27.7% for Bacillus and 19.0% for Corynebacterium species. Conclusions: Coagulase-negative Staphylococcus and viridans group Streptococcus isolates showed high probability of being true pathogens in the pediatric population, especially in patients with underlying malignancy.

Concordance between blood and cerebrospinal fluid cultures in meningitis

OBJECTIVE

To examine the association between cerebrospinal fluid (CSF) cultures and blood cultures in patients with suspected bacterial or fungal meningitis.

METHODS

A 5-year retrospective chart review, conducted from April 2012 to January 2017 of consecutive patient encounters with bacterial or fungal organism growth in CSF culture, when a blood culture was also obtained. Patients were excluded if they received antibiotics prior to either lumbar puncture (LP) or blood culture acquisition, or if CSF cultures were positive for common bacterial skin contaminants. Descriptive statistics were used to characterize the dataset.

RESULTS

21 patient encounters met study inclusion criteria. 13 (61.9%; 95% CI 40.2-80.5%) had blood culture growth of the same organism as the CSF culture. 1 patient had a different organism in the blood culture compared to the CSF culture. 6 patients (33.3%, 95% CI 14.8%-56.9%) with positive CSF cultures had negative blood cultures.

CONCLUSIONS

Our results suggest an insufficient degree of agreement between CSF and blood culture results. PCR may be a prudent approach in patients requiring immediate antibiotics and delayed LP.

Approach to Positive Blood Cultures in the Hospitalized Patient: A Review

The use of blood cultures as a diagnostic tool has increased over the years along with improvements in techniques and results. The diagnostic dilemma arises when blood cultures are positive and there is possibility of contamination. Hence obtaining blood cultures in the appropriate setting and the interpretation of blood cultures by the hospitalist is imperative to the management of the hospitalized patient.

Population-based study of early-onset neonatal sepsis in Canada

OBJECTIVE

To determine the incidence, types of organisms and resistance patterns involved in early-onset neonatal sepsis in Canada.

STUDY DESIGN

Early-onset neonatal sepsis cases were identified through the Canadian Paediatric Surveillance Program. Neonates were excluded if they were asymptomatic or if intracranial procedures preceded a positive cerebrospinal fluid culture.

RESULTS

One hundred and twenty-seven cases were identified (0.17 cases per 1000 live births). Group B Streptococcus accounted for 41.7%, Escherichia coli for 35.4%. Antibiotic resistance was present in 33.9% of all cases. 55.6% of E coli cases were resistant, most commonly to ampicillin. Infecting organism species were associated with gestational age, being very low birth weight, time at sepsis presentation, maternal antibiotic prophylaxis and rupture of membranes lasting over 18 hours. Group B Streptococcus was most common in term and E coli in preterm neonates. Twenty-two per cent of E coli cases presented after 48 hours, compared to 6% of Group B Streptococcus cases.

CONCLUSION

We identify a lower rate of early-onset neonatal sepsis than historically suggested, with differing dominant organisms based on gestational ages and other factors, as well as high rates of resistance especially among E coli cases.

The species distribution, antimicrobial resistance and risk factors for poor outcome of coagulase-negative staphylococci bacteraemia in China

Objective

Coagulase-negative staphylococci (CoNS) are one of the major opportunistic pathogens and the incidence of CoNS bacteraemia is increasing. However, most of the CoNS-positive blood cultures are contaminants rather than true CoNS bacteraemia. In order to minimize contamination, we defined true CoNS bacteraemia as the patient that has two or more identical CoNS-positive blood cultures drawn within 48 h in this study and the objective of this study was to analyse the species distribution and antibiotic resistance and to identify risk factors for 30-day mortality of the true CoNS-bacteraemia.

Method

By reviewing the electronic medical database, this study retrospectively analysed patients diagnosed as CoNS bacteraemia by blood cultures in a comprehensive tertiary care hospital in China from January 1, 2014, to December 31, 2017.

Result

A total of 1241 patients with 1562 episodes of CoNS-positive blood cultures were recorded in the database but only 157 patients were finally diagnosed as true CoNS bacteraemia after contaminants were excluded. All these 157 patients (12.7%, 157/1241) had bacteraemia-related clinical symptoms. Among the 157 patients, the most common species were Staphylococcus hominis (40.8%), Staphylococcus epidermidis (36.3%) and Staphylococcus capitis (11.5%). The antimicrobial susceptibility tests showed that all CoNS had a high rate of resistance to penicillin (94.9%), oxacillin (93.6%) and erythromycin (92.4%). Resistance to gentamicin (22.3%) and rifampicin (10.8%) was low, and none of the bacteria were resistant to vancomycin or linezolid. The 30-day mortality of patients with CoNS bacteraemia was up to 12.7% (20/157), and the multivariate logistics regression analysis showed that chronic renal failure (OR 5.9, 95% CI 1.6–21.5, p = 0.007) and chronic liver failure (OR 4.0, 95% CI 1.2–13.1, p = 0.024) were both the significant independent risk factors for the 30-day mortality of CoNS bacteraemia.

Conclusion

Staphylococcus hominis and Staphylococcus epidermidis were the most common species in CoNS bacteraemia. All CoNS had high multi-drug resistance, but gentamicin and rifampicin had a relatively lower resistance and could be considered as alternative antibiotics for anti-CoNS bacteraemia in addition to vancomycin and linezolid. Additionally, patients with chronic renal failure or chronic liver failure have a higher 30-day mortality after the onset of CoNS bacteraemia.

Estimated Clinical and Economic Impact through Use of a Novel Blood Collection Device To Reduce Blood Culture Contamination in the Emergency Department: a Cost-Benefit Analysis

Blood culture contamination results in increased hospital costs and exposure to antimicrobials. We evaluated the potential clinical and economic benefits of an initial specimen diversion device (ISDD) when routinely utilized for blood culture collection in the emergency department (ED) of a quaternary care medical center. A decision analysis model was created to identify the cost benefit of the use of the ISDD device in the ED. Probabilistic costs were determined from the published literature and the direct observation of pharmacy/microbiology staff. The primary outcome was the expected per-patient cost savings (microbiology, pharmacy, and indirect hospital costs) with the routine use of an ISDD from a hospital perspective. The indirect costs included those related to an increased hospital length of stay, additional procedures, adverse drug reactions, and hospital-acquired infections. Models were created to represent hospitals that routinely or do not routinely use rapid diagnostic tests (RDT) on positive blood cultures. The routine implementation of ISDD for blood culture collection in the ED was cost beneficial compared to conventional blood culture collection methods. When implemented in a hospital utilizing RDT with a baseline contamination rate of 6%, ISDD use was associated with a cost savings of $272 (3%) per blood culture in terms of overall hospital costs and $28 (5.4%) in direct-only costs. The main drivers of cost were baseline contamination rates and the duration of antibiotics given to patients with negative blood cultures. These findings support the routine use of ISDD during blood culture collection in the ED as a cost-beneficial strategy to reduce the clinical and economic impact of blood culture contamination in terms of microbiology, pharmacy, and wider indirect hospital impacts.

Effect of Algorithm-Based Therapy vs Usual Care on Clinical Success and Serious Adverse Events in Patients with Staphylococcal Bacteremia: A Randomized Clinical Trial

IMPORTANCE

The appropriate duration of antibiotics for staphylococcal bacteremia is unknown.

OBJECTIVE

To test whether an algorithm that defines treatment duration for staphylococcal bacteremia vs standard of care provides noninferior efficacy without increasing severe adverse events.

DESIGN, SETTING, AND PARTICIPANTS

A randomized trial involving adults with staphylococcal bacteremia was conducted at 16 academic medical centers in the United States (n = 15) and Spain (n = 1) from April 2011 to March 2017. Patients were followed up for 42 days beyond end of therapy for those with Staphylococcus aureus and 28 days for those with coagulase-negative staphylococcal bacteremia. Eligible patients were 18 years or older and had 1 or more blood cultures positive for S aureus or coagulase-negative staphylococci. Patients were excluded if they had known or suspected complicated infection at the time of randomization.

INTERVENTIONS

Patients were randomized to algorithm-based therapy (n = 255) or usual practice (n = 254). Diagnostic evaluation, antibiotic selection, and duration of therapy were predefined for the algorithm group, whereas clinicians caring for patients in the usual practice group had unrestricted choice of antibiotics, duration, and other aspects of clinical care.

MAIN OUTCOMES AND MEASURES

Coprimary outcomes were (1) clinical success, as determined by a blinded adjudication committee and tested for noninferiority within a 15% margin; and (2) serious adverse event rates in the intention-to-treat population, tested for superiority. The prespecified secondary outcome measure, tested for superiority, was antibiotic days among per-protocol patients with simple or uncomplicated bacteremia.

RESULTS

Among the 509 patients randomized (mean age, 56.6 [SD, 16.8] years; 226 [44.4%] women), 480 (94.3%) completed the trial. Clinical success was documented in 209 of 255 patients assigned to algorithm-based therapy and 207 of 254 randomized to usual practice (82.0% vs 81.5%; difference, 0.5% [1-sided 97.5% CI, -6.2% to ∞]). Serious adverse events were reported in 32.5% of algorithm-based therapy patients and 28.3% of usual practice patients (difference, 4.2% [95% CI, -3.8% to 12.2%]). Among per-protocol patients with simple or uncomplicated bacteremia, mean duration of therapy was 4.4 days for algorithm-based therapy vs 6.2 days for usual practice (difference, -1.8 days [95% CI, -3.1 to -0.6]).

CONCLUSIONS AND RELEVANCE

Among patients with staphylococcal bacteremia, the use of an algorithm to guide testing and treatment compared with usual care resulted in a noninferior rate of clinical success. Rates of serious adverse events were not significantly different, but interpretation is limited by wide confidence intervals. Further research is needed to assess the utility of the algorithm.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01191840.

[Assessment of an educational intervention regarding blood cultures as process indicators in an emergency department in Argentina]

OBJECTIVE

The aim of this study was to describe 2 process indicators related to taking blood cultures (BC) in an Adult Emergency Department of a tertiary university hospital in Buenos Aires,and to describe the changes after a series of educational activities for health professionals was implemented during May 2016 as regards the appropriate indication of BC and the proper collection technique.

MATERIALS AND METHODS

A retrospective cohort study was designed to assess its effectiveness, which consecutively included all patients admitted during 2015-2016. The BC request rate was used as a process indicator, and the percentage of contaminated BCs and the true positives rate were used as quality indicators. Both were measured monthly and prospectively during the period of study.

RESULTS

The annual adjusted rate of BC requests was 4.9% (95% CI 4.8-5) in 2015 and 2.9% (95% CI 2.8-2.9) in 2016. The rate of false positive (contaminated) BCs was 4.5% in 2015 and 4.3% after the educational intervention. The true positive BCs were 8.3% in 2015 and 12% post-intervention.

CONCLUSIONS

These findings prove how important and effective the educational interventions are.

Clinical Evaluation of the iCubate iC-GPC Assay for Detection of Gram-Positive Bacteria and Resistance Markers from Positive Blood Cultures

The iC-GPC Assay (iCubate, Huntsville, AL) is a qualitative multiplex test for the detection of five of the most common Gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, and Enterococcus faecium) responsible for bacterial bloodstream infections, performed directly from positive blood cultures. The assay also detects the presence of the mecA, vanA, and vanB resistance determinants.

The iC-GPC Assay (iCubate, Huntsville, AL) is a qualitative multiplex test for the detection of five of the most common Gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, and Enterococcus faecium) responsible for bacterial bloodstream infections, performed directly from positive blood cultures. The assay also detects the presence of the mecA, vanA, and vanB resistance determinants. This study comparatively evaluated the performance of the iC-GPC Assay against the Verigene Gram-positive blood culture (BC-GP) assay (Luminex Corp., Austin, TX) for 1,134 patient blood culture specimens positive for Gram-positive cocci. The iC-GPC Assay had an overall percent agreement with the BC-GP assay of 95.5%. Discordant specimens were further analyzed by PCR and a bidirectional sequencing method. The results indicate that the iC-GPC Assay together with the iCubate system is an accurate and reliable tool for the detection of the five most common Gram-positive bacteria and their resistance markers responsible for bloodstream infections.

Effect of a training programme on blood culture contamination rate in critical care

Blood culture contamination can occur from extraction to processing; its rate should not exceed 3%.

OBJECTIVE

To evaluate the impact of a training programme on the rate of contaminated blood cultures after the implementation of sample extraction recommendations based on the best evidence.

METHOD

Prospective before-after study in a polyvalent intensive care unit with 18 beds. Two phases were established (January-June 2012, October 2012-October 2015) with a training period between them. Main recommendations: sterile technique, surgical mask, double skin disinfection (70° alcohol and 2% alcoholic chlorhexidine), 70° alcohol disinfection of culture flasks and injection of samples without changing needles. Including all blood cultures of patients with extraction request.

VARIABLES

demographic, severity, pathology, reason for admission, stay and results of blood cultures (negative, positive and contaminated). Basic descriptive statistics: mean (standard deviation), median (interquartile range) and percentage (95% confidence interval). Calculated contamination rates per 100 blood cultures extracted. Bivariate analysis between periods.

RESULTS

Four hundred and eight patients were included. Eight hundred and forty-one blood cultures were taken, 33 of which were contaminated. In the demographic variables, severity, diagnosis and stay of patients with contaminated samples, no differences were observed from those with uncontaminated samples. Pre-training vs post-training contamination rates: 14 vs 5.6 per 100 blood cultures extracted (P=.00003).

CONCLUSION

An evidence-based training programme reduced the contamination of samples. It is necessary to continue working on the planning of activities and care to improve the detection of pollutants and prevent contamination of samples.

Retrospective evaluation of the clinical characteristics associated with Corynebacterium species bacteremia

Objectives

Corynebacterium spp. are becoming recognized as pathogens that potentially cause various infections. We aimed to evaluate the clinical characteristics associated with Corynebacterium spp. bacteremia.

Patients and methods

We retrospectively reviewed the medical records of all adult patients who had positive blood cultures for Corynebacterium spp. in a single university hospital between January 2014 and December 2016. Patients were divided into a bacteremia group and a contamination group based on microbiological test results and clinical characteristics. Patients’ characteristics, antimicrobial susceptibility of isolated species, antimicrobials administered, and patient outcomes were evaluated.

Results

Corynebacterium spp. were isolated from blood samples of 63 patients; Corynebacterium striatum was the predominant isolate. Twenty-eight patients were determined to have bacteremia. Younger age (p = 0.023), shorter time to positivity (p = 0.006), longer hospital stay (p = 0.009), and presence of an indwelling vascular catheter (p = 0.002) were observed more often in the bacteremia group compared to the contamination group. The source of infection in most patients with bacteremia was an intravenous catheter. All tested strains were susceptible to vancomycin. Four of the 27 patients with bacteremia died, despite administration of appropriate antimicrobial therapy.

Conclusions

We found that younger age, shorter time to positivity, and presence of an indwelling catheter were related to bacteremia caused by Corynebacterium spp. Appropriate antimicrobials should be administered once Corynebacterium spp. are isolated from the blood and bacteremia is suspected.

Review article: Sepsis in the emergency department - Part 2: Investigations and monitoring

Sepsis is characterised by organ dysfunction resulting from infection, with no reliable single objective test and current diagnosis based on clinical features and results of investigations. In the ED, investigations may be conducted to diagnose infection as the cause of the presenting illness, identify the source, distinguish sepsis from uncomplicated infection (i.e. without organ dysfunction) and/ or risk stratification. Appropriate sample collection for microbiological testing remains key for subsequent confirmation of diagnosis and rationalisation of antimicrobials. Routine laboratory investigations such as creatinine, bilirubin, platelet count and lactate are now critical elements in the diagnosis of sepsis and septic shock. With no biomarker sufficiently validated to rule out bacterial infection in the ED, there remains substantial interest in biomarkers representing various pathogenic pathways. New technologies for screening multiple genes and proteins are identifying unique network 'signatures' of clinical interest. Other future directions include rapid detection of bacterial DNA in blood, genes for antibiotic resistance and EMR-based computational biomarkers that collate multiple information sources. Reliable, cost-effective tests, validated in the ED to promptly and accurately identify sepsis, and to guide initial antibiotic choices, are important goals of current research efforts.

Diagnostic and prognostic performances of serum procalcitonin in patients with bloodstream infections: A parallel, case-control study comprising adults and elderly

Objective:

To examine the diagnostic and prognostic performances of serum procalcitonin (PCT) in adult and elderly patients with bloodstream infections (BSIs).

Method:

A total of 176 patients with culture-proven BSIs and 200 healthy counterparts were studied prospectively. Participants were studied in two adult (age≤65 years, n=92) and elderly (age>65 years, n=84) groups. Admission serum PCT level was measured using a standard enzyme-linked immunosorbent assay (ELISA) technique.

Results:

The mean serum PCT level (in ng/mL) was significantly higher in cases than in controls (0.18 vs. 0.07, p=0.01 in adults; 0.20 vs. 0.07, p=0.002 in elderly). At cut-off values of 0.09 ng/mL in adults and 0.08 ng/mL in the elderly, the corresponding sensitivity and specificity were 82.6 and 82.0% in adults, and 69.1 and 70.0% in elderly, respectively. At a cut-off value of 0.2 ng/mL, the sensitivity and specificity of serum PCT in predicting 28-day mortality were 81 and 81.7% in adults, and 75 and 80.4% in elderly, respectively.

Conclusion:

Although admission serum PCT is a sensitive and specific biomarker for the diagnosis of BSIs in patients younger than 65 years old, its short-term prognostic value is comparable between adults and the elderly.

Utility of Blood Culture Among Children Hospitalized With Community-Acquired Pneumonia

BACKGROUND AND OBJECTIVES

National guidelines recommend blood cultures for children hospitalized with presumed bacterial community-acquired pneumonia (CAP) that is moderate or severe. We sought to determine the prevalence of bacteremia and characterize the microbiology and penicillin-susceptibility patterns of positive blood culture results among children hospitalized with CAP.

METHODS

We conducted a cross-sectional study of children hospitalized with CAP in 6 children's hospitals from 2007 to 2011. We included children 3 months to 18 years of age with discharge diagnosis codes for CAP using a previously validated algorithm. We excluded children with complex chronic conditions. We reviewed microbiologic data and classified positive blood culture detections as pathogens or contaminants. Antibiotic-susceptibility patterns were assessed for all pathogens.

RESULTS

A total of 7509 children hospitalized with CAP were included over the 5-year study period. Overall, 34% of the children hospitalized with CAP had a blood culture performed; 65 (2.5% of patients with blood cultures; 95% confidence interval [CI]: 2.0%-3.2%) grew a pathogen. Streptococcus pneumoniae accounted for 78% of all detected pathogens. Among detected pathogens, 50 (82%) were susceptible to penicillin. Eleven children demonstrated growth of an organism nonsusceptible to penicillin, representing 0.43% (95% CI: 0.23%-0.77%) of children with blood cultures obtained and 0.15% (95% CI: 0.08%-0.26%) of all children hospitalized with CAP.

CONCLUSIONS

Among children without comorbidities hospitalized with CAP in a non-ICU setting, the rate of bacteremia was low, and isolated pathogens were usually susceptible to penicillin. Blood cultures may not be needed for most children hospitalized with CAP.

Pathogen or contaminant? Distinguishing true infection from synovial fluid culture contamination in patients with suspected septic arthritis

BACKGROUND

Isolation of bacteria from synovial fluid (SF) is the gold standard for diagnosis of septic arthritis (SA). Contamination results in misdiagnosis and mismanagement. This study identifies clinical characteristics, microbiology, and outcomes of patients with contaminated SF and compares them with patients with true SA.

METHODS

We conducted a retrospective study including all patients aged 18 and older admitted to a single, tertiary-care hospital between 1998 and 2015 with suspected SA and positive SF cultures. Contamination cases were determined by infectious disease specialists involved in the patients' care and a clinical course inconsistent with SA.

RESULTS

398 patients with true SA and 22 with contaminated SF were identified. The SA group was younger (60.9 vs. 75.6 years; p < 0.01), had higher peripheral polymorphonuclear lymphocytes (78.0 vs. 69.4%; p < 0.01) and SF white blood cell count (91.7 vs. 25.6K/mL; p = 0.02), and longer mean length of stay (10.9 vs. 6.7 days; p = 0.02). The average time to positive culture was longer in the contaminated group (3.62 vs. 1.4 days; p < 0.01). The SA group was less likely to receive a new rheumatologic diagnosis within 1 year (3.0 vs. 36.4%; p < 0.01).

CONCLUSION

This is the first study of its kind looking at clinical features and outcomes of patients with contaminated SF. These patients present with less severe disease, have better outcomes, and receive new rheumatologic diagnoses in more than a third of cases within 1 year. We recommend a conservative approach for patients with suspected contaminated SF, mild symptoms, and no bacterial growth within the first 48 h.

Diagnostic value of serum procalcitonin, lactate, and high-sensitivity C-reactive protein for predicting bacteremia in adult patients in the emergency department

BACKGROUND

Few studies compared the diagnostic value of procalcitonin with a combination of other tests including lactate and high-sensitivity C-reactive protein in the prediction of pathogenic bacteremia in emergency department adult patients.

METHODS

We performed a retrospective study assessing the differences in performances of procalcitonin at a cutoff of 0.5 ng/mL, lactate at a cutoff of 19.8 mg/dL, high-sensitivity C-reactive protein at a cutoff of 0.8 mg/dL and their combinations for predicting bacteremia in emergency department adult patients. Sensitivity, specificity, overall accuracy, positive-test and negative-test likelihood, and diagnostic odds ratio with 95% confidence interval for each test combination were calculated for comparison. The receiver operating characteristic curve for every single test were compared using DeLong's method. We also performed a sensitivity analysis in two expanded patient cohorts to assess the discriminative ability of procalcitonin or test combination.

RESULTS

A total of 886 patients formed the initial patient cohort. The area under the receiver operating characteristic curve for discriminating positive blood culture was: procalcitonin = 0.72 (95% CI [0.69-0.75]) with a derived optimal cutoff at 3.9 ng/mL; lactate 0.69 (0.66-0.72) with an optimal cutoff at 17.9 mg/dL; high-sensitivity C-reactive protein 0.56 (0.53-0.59) with an optimal cutoff of 13 mg/dL; with pairwise comparisons showing statistically significant better performance of either procalcitonin or lactate outperforming high-sensitivity C-reactive protein. To predict positive blood cultures, the diagnostic odds ratio for procalcitonin was 3.64 (95% CI [2.46-5.51]), lactate 2.93 (2.09-4.14), and high-sensitivity C-reactive protein 0.91 (0.55-1.55; P = 0.79). About combined tests, the diagnostic odds ratio for procalcitonin and lactate increases were 3.98 (95% CI [2.81-5.63]) for positive blood culture prediction. Elevated procalcitonin level rendered a six-fold increased risk of positive gram-negative bacteremia with a diagnostic odds ratio of 6.44 (95% CI [3.65-12.15]), which showed no further improvement in any test combinations. In the sensitivity analysis, as a single test to predict unspecified, gram-negative and gram-positive bacteremia, procalcitonin performed even better in an expanded cohort of 2,234 adult patients in terms of the diagnostic odds ratio.

DISCUSSIONS

For adult emergency patients, procalcitonin has an acceptable discriminative ability for bacterial blood culture and a better discriminative ability for gram-negative bacteremia when compared with lactate and high-sensitivity C-reactive protein. High-sensitivity C-reactive protein at a cutoff of 0.8 mg/dL performed poorly for the prediction of positive bacterial culture.

Significance of coagulase negative Staphylococcus from blood cultures: persisting problems and partial progress in resource constrained settings

BACKGROUND AND OBJECTIVES

Coagulase negative Staphylococcus (CoNS) is frequently isolated from blood cultures but their significance is difficult to interpret. CoNS bacteria which are often previously dismissed as culture contaminants are attracting greater importance as true pathogens in the past decades. Clinical evaluation of these isolates suggests that although there is a relative increase of CoNS associated bloodstream infections in recent years, the microorganisms still remain the most common contaminants in blood cultures. The objective of this study was to determine the significance of CoNS isolated from blood cultures.

MATERIALS AND METHODS

A retrospective study was conducted to evaluate the rate of contamination in blood cultures in a tertiary care hospital. The paired specimens of blood were cultured using conventional culture methods and the isolates of coagulase negative staphylococci were identified by standard methodology. Clinical data, laboratory indices, microbiological parameters and patient characteristics were analyzed.

RESULTS

Of 3503 blood samples, CoNS were isolated from blood culture of 307 patients (8.76%). The isolates were reported as true pathogens of bloodstream infections in only 74 out of 307 cases (24.1%). In the vast majority, 212 of 307 (69.0%), they were mere blood culture contaminants and reported as insignificant/contaminant.

CONCLUSION

Determining whether a growth in the blood culture is a pathogen or a contaminant is a critical issue and multiple parameters have to be considered before arriving at a conclusion. Ideally, the molecular approach is for the most part a consistent method in determining the significant isolates of CoNS. However, in countries with inadequate resources, species identification and antibiogram tests are recommended when determining significance of these isolates.

Best Clinical Practice: Blood Culture Utility in the Emergency Department

BACKGROUND

Bacteremia affects 200,000 patients per year, with the potential for significant morbidity and mortality. Blood cultures are considered the most sensitive method for detecting bacteremia and are commonly obtained in patients with fever, chills, leukocytosis, focal infections, and sepsis.

OBJECTIVE

We sought to provide emergency physicians with a review of the literature concerning blood cultures in the emergency department.

DISCUSSION

The utility of blood cultures has been a focus of controversy, prompting research evaluating effects on patient management. Bacteremia is associated with increased mortality, and blood cultures are often obtained for suspected infection. False-positive blood cultures are associated with harm, including increased duration of stay and cost. This review suggests that blood cultures are not recommended for patients with cellulitis, simple pyelonephritis, and community-acquired pneumonia, because the chance of a false-positive culture is greater than the prevalence of true positive cultures. Blood cultures are recommended for patients with sepsis, meningitis, complicated pyelonephritis, endocarditis, and health care-associated pneumonia. Clinical prediction rules that predict true positive cultures may prove useful. The clinical picture should take precedence. If cultures are obtained, two bottles of ≥7 mL should be obtained from separate peripheral sites.

CONCLUSIONS

Blood cultures are commonly obtained but demonstrate low yield in cellulitis, simple pyelonephritis, and community-acquired pneumonia. The Shapiro decision rule for predicting true bacteremia does show promise, but clinical gestalt should take precedence. To maximize utility, blood cultures should be obtained before antibiotic therapy begins. At least two blood cultures should be obtained from separate peripheral sites.

Selected Topics in Anaerobic Bacteriology

Alteration in the host microbiome at skin and mucosal surfaces plays a role in the function of the immune system, and may predispose immunocompromised patients to infection. Because obligate anaerobes are the predominant type of bacteria present in humans at skin and mucosal surfaces, immunocompromised patients are at increased risk for serious invasive infection due to anaerobes. Laboratory approaches to the diagnosis of anaerobe infections that occur due to pyogenic, polymicrobial, or toxin-producing organisms are described. The clinical interpretation and limitations of anaerobe recovery from specimens, anaerobe-identification procedures, and antibiotic-susceptibility testing are outlined. Bacteriotherapy following analysis of disruption of the host microbiome has been effective for treatment of refractory or recurrent Clostridium difficile infection, and may become feasible for other conditions in the future.

Impact of a Rapid Blood Culture Assay for Gram-Positive Identification and Detection of Resistance Markers in a Pediatric Hospital

CONTEXT

Molecular diagnostics allow for rapid identification and detection of resistance markers of bloodstream infection, with a potential for accelerated antimicrobial optimization and improved patient outcomes. Although the impact of rapid diagnosis has been reported, studies in pediatric patients are scarce.

OBJECTIVE

To determine the impact of a molecular blood-culture assay that identifies a broad-spectrum of pathogens and resistance markers in pediatric patients with gram-positive bloodstream infections.

DESIGN

Data on the time to antimicrobial optimization, the length of hospitalization, and the hospital cost following implementation of a rapid assay were prospectively collected and compared with corresponding preimplementation data.

RESULTS

There were 440 episodes from 383 patients included, 221 preimplementation episodes and 219 postimplementation episodes. Overall time to antimicrobial optimization was shortened by 12.5 hours (P = .006), 11.9 hours (P = .005) for bloodstream infections of Staphylococcus aureus specifically. Duration of antibiotics for those with probable blood-culture contamination with coagulase-negative staphylococci was reduced by 36.9 hours (P < .001). Median length of stay for patients admitted to general pediatric units was 1.5 days shorter (P = .04), and median hospital cost was $3757 (P = .03) less after implementation. For S aureus bloodstream infections, median length of stay and hospital cost were decreased by 5.6 days (P = .01) and $13,341 (P = .03), respectively.

CONCLUSIONS

Implementation of molecular assay for the detection of gram-positive pathogens and resistance markers significantly reduced time to identification and resistance detection, resulting in accelerated optimization of therapy, shorter length of stay, and decreased health care cost.

Bacteraemia during Transurethral Resection of the Prostate: What Are the Risk Factors and Is It More Common than We Think?

The aim of this work was to investigate the microbial causes, incidence, duration, risk factors and clinical implications of bacteraemia occurring during transurethral resection of the prostate (TURP) surgery to better inform prophylaxis strategies. An ethically approved, prospective, cohort study of patients undergoing TURP was conducted. Clinical information and follow-up details were collected using standardized data collection sheets. Blood was obtained for culture at 6 different time points peri-procedure. Standard of care antibiotic prophylaxis was given prior to surgery. Bacteriuria was assessed in a pre-procedure urine sample. Histopathology from all prostate chips was assessed for inflammation and malignancy. 73 patients were consented and 276 blood samples obtained. No patients developed symptomatic bacteraemia during the procedure, 17 patients developed asymptomatic bacteraemia (23.2%). Enterococcus faecalis and Pseudomonas aeruginosa were the most common organisms cultured. 10 minutes after the start of the TURP, the odds ratio (OR) of developing bacteraemia was 5.38 (CI 0.97-29.87 p = 0.05), and 20 minutes after the start of the procedure, the OR was 6.46 (CI 1.12-37.24, p = 0.03), compared to before the procedure. We also found an association between the development of intra-operative bacteraemia and recent antibiotic use (OR 4.34, CI 1.14-16.62, p = 0.032), the presence of a urinary catheter (OR 4.92, CI 1.13-21.51, p = 0.034) and a malignant histology (OR 4.90, CI 1.30-18.46, p = 0.019). There was no statistical relationship between pre-operative urine culture results and blood culture results. This study shows that asymptomatic bacteraemia is commonly caused by TURP and occurs in spite of antibiotic prophylaxis. Our findings challenge the commonly held view that urine is the primary source of bacteraemia in TURP-associated sepsis and raise the possibility of occult prostatic infection as a cause of bacteraemia. More work will be needed to determine the significance of transient bacteraemia in relation to more serious complications like infective endocarditis and malignancy.

Determining the Clinical Significance of Coagulase-Negative Staphylococci Isolated From Blood Cultures

Background and Objective:

Coagulase-negative staphylococci are both an important cause of nosocomial bloodstream infections and the most common contaminants of blood cultures. Judging the clinical significance of coagulase-negative staphylococci is vital but often difficult and can have a profound impact on an institution's bloodstream infection rates. Our objective was to develop an algorithm to assist in determining the clinical significance of coagulase-negative staphylococci.

Design:

A single experienced reviewer examined the medical records of 960 consecutive patients with positive blood cultures in a tertiary-care referral teaching hospital. Four hundred five of the cultures contained coagulase-negative staphylococci. A determination of clinical significance was made and the performances of various published algorithms that contained readily available clinical and laboratory data were compared.

Results:

Eighty-nine (22%) of the episodes were considered significant, whereas 316 were contaminants. Patients with bacteremia were significantly more likely to be neutropenic and exhibit signs of sepsis syndrome. The algorithm with the best combined sensitivity (62%) and specificity (91%) for determining the clinical significance of coagulase-negative staphylococci was defined as at least two blood cultures positive for coagulase-negative staphylococci within 5 days, or one positive blood culture plus clinical evidence of infection, which includes abnormal white blood cell count and temperature or blood pressure.

Conclusion:

Use of this algorithm could potentially reduce misclassification of nosocomial bloodstream infections and inappropriate use of vancomycin for positive blood cultures likely to represent contamination (Infect Control Hosp Epidemiol2005;26:559-566).

A change of culture: reducing blood culture contamination rates in an Emergency Department

Blood cultures are an important investigation to help tailor effective management for patients with severe sepsis. Frequent contaminated samples increase laboratory workload and can delay or cause incorrect changes to patient management. This can prolong patient hospitalisation, increase the risk of harm and increase cost to health boards. Current guidelines advocate a contamination rate of 2-3%. From January 2013 to November 2014 inclusive, the contamination rate was 4.74% in our Emergency Department, responsible for initial management and investigation of over 40 cases of sepsis per month. A Quality Improvement team was created to try to reduce contamination rates to the recommended target. An initial baseline survey of local staff showed good understanding of when to obtain a blood culture but there was variability in the methods and equipment used. A project was then conducted which focused on rationalising and standardising equipment and technique for blood culture sampling along with staff education to support this change. A simple department target of 30 days free from a contaminated blood culture was created which, if achieved, would ensure a contamination rate of less than 3%. This was supported by ongoing surveillance of contamination rates and investigation of contaminated sample cases. We were able to then identify high risk patients and factors which increased the chance of blood culture contamination. This allowed us to formulate solutions to help reduce the risks of contamination. Department achievements and learning points to help prevent further contamination were fed back positively to all staff. This project operated for 12-months and successfully reduced local contamination rates to 2.0%.

Multidisciplinary team review of best practices for collection and handling of blood cultures to determine effective interventions for increasing the yield of true-positive bacteremias, reducing contamination, and eliminating false-positive central line-associated bloodstream infections

BACKGROUND

A literature search was conducted using keywords for articles published in English from January 1990 to March 2015. Using criteria related to blood culture collection and handling, the search yielded 101 articles. References used also included Microbiology Laboratory standards, guidelines, and textbook information.

RESULTS

The literature identified diverse and complex issues surrounding blood culture practices, including the impact of false-positive results, laboratory definition of contamination, effect on central line-associated bloodstream infection (CLABSI) reporting, indications for collecting blood cultures, drawing from venipuncture sites versus intravascular catheters, selection of antiseptics, use of needleless connectors, inoculation of blood culture bottles, and optimizing program management in emergency departments, education, and implementation of bundled practice initiatives.

CONCLUSION

Hospitals should optimize best practice in the collection, handling, and management of blood culture specimens, an often overlooked but essential component in providing optimal care of patients in all settings and populations, reducing financial burdens, and increasing the accuracy of reportable CLABSI. Although universal concepts exist in blood culture practices, some issues require further research to determine benefit. Institutions undertaking a review of their blood culture programs are encouraged to use a checklist that addresses elements that encompass the research contained in this review.

Staphylococcus epidermidis as a cause of bacteremia

Staphylococcus epidermidis is a biofilm-producing commensal organism found ubiquitously on human skin and mucous membranes, as well as on animals and in the environment. Biofilm formation enables this organism to evade the host immune system. Colonization of percutaneous devices or implanted medical devices allows bacteria access to the bloodstream. Isolation of this organism from blood cultures may represent either contamination during the blood collection procedure or true bacteremia. S. epidermidis bloodstream infections may be indolent compared with other bacteria. Isolation of S. epidermidis from a blood culture may present a management quandary for clinicians. Over-treatment may lead to patient harm and increases in healthcare costs. There are numerous reports indicating the difficulty of predicting clinical infection in patients with positive blood cultures with this organism. No reliable phenotypic or genotypic algorithms currently exist to predict the pathogenicity of a S. epidermidis bloodstream infection. This review will discuss the latest advances in identification methods, global population structure, pathogenicity, biofilm formation, antimicrobial resistance and clinical significance of the detection of S. epidermidis in blood cultures. Previous studies that have attempted to discriminate between invasive and contaminating strains of S. epidermidis in blood cultures will be analyzed.

Cost-Effectiveness of 30- Compared to 20-Milliliter Blood Cultures: a Retrospective Study

The importance of blood culture (BC) volume for detection of bloodstream infections (BSIs) is documented. Recently, improved diagnostic sensitivity was demonstrated for 30- versus 20-ml BCs in adults (Cockerill FR, Wilson JW, Vetter EA, Goodman KM, Torgerson CA, Harmsen WS, Schleck CD, IIstrup DM, Washington JA, Wilson WR. Clin Infect Dis 38:1724-1730, 2004, http://dx.doi.org/10.1128/JCM.01314-11). Hospitals receive higher reimbursement for patients with documented septicemia. We determined the cost-effectiveness of 30-ml versus 20-ml BCs using results from our institution and previously published data. Positive BC results from 292 bacteremic episodes were reviewed. The costs of the reagents, equipment, phlebotomist, and technologist time were determined. The medical records department provided Medicare reimbursement (MR) data for patients with selected ICD-9 codes. These data provided an estimate of the annualized increase in MR versus costs associated with conversion to 30-ml BCs. MR for 464 annual primary BSIs was $24,808/episode. An expected 7.2% increase in BSIs detected using 30-ml BCs would add 34 additional cases annually and increase MR by $843,472. Comparative MR data for cases where septicemia complicated another diagnosis were available for 4 International Classification of Diseases, Ninth Revision (ICD-9) codes: laparoscopic cholecystectomy, biliary tract disorders, pneumonia, and cellulitis. The mean incremental MR was $9,667 per episode, which projected to a $483,350 revenue increase annually. The annual cost associated with conversion to 30-ml BCs was estimated to be $157,798. Thus, the potential net increase in hospital revenue would be $1,169,031 for 30-ml versus 20-ml BCs. Our results suggest that conversion to 30-ml BCs may not only improve patient care by detecting more BSIs but also increase hospital revenue substantially.