Time to positivity in Staphylococcus aureus bacteremia: possible correlation with the source and outcome of infection

Estimating bacterial load in S. aureus and E. coli bacteremia using bacterial growth graph from the continuous monitoring blood culture system

BACKGROUND

We examined whether the time to positivity (TTP) and growth and detection plot graph (GDPG) created by the automated blood culture system can be used to determine the bacterial load in bacteremic patients and its potential association correlation with disease severity.

METHODS

Known bacterial inocula were injected into the blood culture bottles. The GDPGs for the specific inocula were downloaded and plotted. A cohort of 30 consecutive clinical cultures positive for S. aureus and E. coli was identified. Bacterial load was determined by comparing the GDPG with the "standard" curves. Variables associated with disease severity were compared across 3 bacterial load categories (< 100, 100-1000, > 1000 CFU/mL).

RESULTS

S. aureus growth was sensitive to the blood volume obtained whereas E. coli growth was less so. A 12-hour delay in sample transfer to the microbiology laboratory resulted in a decrease in TTP by 2-3 h. Mean TTP was 15 and 10 h for S. aureus and E. coli, respectively, which correlates with > 1000 CFU/mL and 500-1000 CFU/ml. For S. aureus, patients with a bacterial load > 100 CFU/mL had a higher mortality rate, (OR for death = 9.7, 95% CI 1.6-59, p = 0.01). Bacterial load > 1000 CFU/mL had an odds ratio of 6.4 (95% CI1.2-35, p = 0.03) to predict an endovascular source. For E. coli bacteremia, we did not find any correlations with disease severity.

CONCLUSION

GDPG retrieved from the automated blood culture system can be used to estimate bacterial load. S.aureus bacterial load, but not E.coli, was associated with clinical outcome.

Distinct Clinical Endpoints of Staphylococcus aureus Bacteraemia Complicate Assessment of Outcome

BACKGROUND

We aimed to test the hypothesis that development of metastatic infection represents a distinct clinical endpoint from death due to Staphylococcus aureus bacteremia (SAB).

METHODS

We conducted a retrospective observational study of adults with SAB between 20 December 2019 and 23 August st2022 (n = 464). Simple logistic regression, odds ratios, and z-scores were used to compare host, clinical, and microbiologic features.

RESULTS

Co-occurrence of attributable mortality and metastatic infection was infrequent. Charlson Comorbidity Index and age were strongly associated with attributable mortality, but not metastatic infection. We compared patients with fatal SAB (without clinically-apparent metastatic complications, 14.4% of cohort), metastatic SAB (without attributable mortality, 22.2%), neither complication (56.7%), and overlapping fatal/metastatic SAB (6.7%). Compared to SAB without complications, fatal SAB was specifically associated with older age and multi-morbidity. Metastatic SAB was specifically associated with community acquisition, persistent fever, persistent bacteremia, and recurrence. Endocarditis was over-represented in the fatal/metastatic SAB overlap group, which shared patient characteristics with fatal SAB. In contrast to other (predominantly musculoskeletal) metastatic complications, endocarditis was associated with increased mortality, with death occurring in older multi-morbid patients later after SAB onset.

CONCLUSIONS

Patients with SAB experience distinct clinical endpoints: (i) early death, associated with multi-morbidity and age; (ii) metastatic (predominantly musculoskeletal) SAB; (iii) endocarditis, associated with late death occurring in older people with multi-morbidity, and (iv) bacteraemia without complications. These distinctions could be important for selecting appropriate outcomes in clinical trials: different interventions might be required to reduce mortality versus improve clinical response in patients with metastatic SAB.

A Machine Learning-Based Risk Score for Prediction of Infective Endocarditis Among Patients With Staphylococcus aureus Bacteremia-The SABIER Score

BACKGROUND

Early risk assessment is needed to stratify Staphylococcus aureus infective endocarditis (SA-IE) risk among patients with S. aureus bacteremia (SAB) to guide clinical management. The objective of the current study was to develop a novel risk score that is independent of subjective clinical judgment and can be used early, at the time of blood culture positivity.

METHODS

We conducted a retrospective big data analysis from territory-wide electronic data and included hospitalized patients with SAB between 2009 and 2019. We applied a random forest risk scoring model to select variables from an array of parameters, according to the statistical importance in predicting SA-IE outcome. The data were divided into derivation and validation cohorts. The areas under the curve of the receiver operating characteristic (AUCROCs) were determined.

RESULTS

We identified 15 741 SAB patients, among them 658 (4.18%) had SA-IE. The AUCROC was 0.74 (95%CI 0.70-0.76), with a negative predictive value of 0.980 (95%CI 0.977-0.983). The four most discriminatory features were age, history of infective endocarditis, valvular heart disease, and community onset.

CONCLUSIONS

We developed a novel risk score with performance comparable with existing scores, which can be used at the time of SAB and prior to subjective clinical judgment.

Make Modern Microbiology Matter More in the 2023 European Society of Cardiology Guidelines for the Management of Infective Endocarditis

The European Society of Cardiology (ESC) 2023 guidelines for the management of infective endocarditis (IE) stress that a multidisciplinary approach is needed to manage patients with IE. In our view, the guidelines do not include the relevant perspectives from modern microbiology. The diagnostic criteria for IE were changed in the ESC 2023 guidelines, and many IE-causing pathogens are either not clearly defined. Moreover, an improved understanding of the relationship between bacterial species and the risk for IE has not been implemented. The guidelines give detailed and, in our view, incorrect instructions about diagnostic testing in blood culture-negative IE without presenting proper evidence. Other important diagnostic aspects, such as the value of repeated blood cultures and incubation time for blood cultures, are not discussed. We believe that a multidisciplinary collaboration that include microbiologists would have improved these guidelines, and we hope for a future harmonization of diagnostic criteria for IE.

Risk factors of bloodstream infection in erythroderma from atopic dermatitis, psoriasis, and drug reactions: a retrospective observational cohort study

Background

Atopic dermatitis (AD), psoriasis, and drug reactions associated with erythroderma are frequently complicated by infections. However, bloodstream infection (BSI) have received less research attention.

Objectives

This study aimed to investigate the clinical characteristics and risk factors associated with BSI in patients with erythroderma.

Methods

A retrospective analysis was conducted on 141 erythroderma cases. Eleven cases were identified as having BSI. Clinical records of both BSI and non-BSI groups were reviewed and compared.

Results

BSI was diagnosed in 7.80% (11/141) of erythroderma cases, with a breakdown of 7.14% in AD, 2.00% in psoriasis, and 17.14% in drug reactions. Notably, all positive skin cultures (7/7) showed bacterial isolates concordant with blood cultures. Univariate logistic regression analysis revealed several significant associations with BSI, including temperature (≤36.0 or ≥38.5 °C; odds ratio (OR) = 28.06; p < 0.001), chilling (OR = 22.10; p < 0.001), kidney disease (OR = 14.64; p < 0.001), etiology of drug reactions (OR = 4.18; p = 0.03), albumin (ALB) (OR = 0.86; p < 0.01), C-reaction protein (CRP) (OR = 1.01; p = 0.02), interleukin 6 (IL-6) (OR = 1.02; p = 0.02), and procalcitonin (PCT) (OR = 1.07; p = 0.03). Receiver operating characteristic (ROC) curves demonstrated significant associations with ALB (p < 0.001; the area under curve (AUC) = 0.80), PCT (p = 0.009; AUC = 0.74), and CRP (p = 0.02; AUC = 0.71).

Conclusions

Increased awareness of BSI risk is essential in erythroderma management. Patients with specific risk factors, such as abnormal body temperature (≤36.0 or ≥38.5 °C), chilling sensations, kidney disease, a history of drug reactions, elevated CRP (≥32 mg/L), elevated PCT (≥1.00 ng/ml), and low albumin (≤31.0 g/L), require close monitoring for BSI development.

The role of time to positive blood cultures in enhancing the predictive capability of DENOVA score for diagnosing infective endocarditis in patients with Enterococcus faecalis bacteremia

DENOVA-score is useful to stratify the risk of infective endocarditis (IE) in Enterococcus faecalis bacteremia. Recently, time to positive (TTP) of blood cultures has also been related with a higher risk of IE. The objective was to evaluate DENOVA- score with TTP to improve its specificity. We performed a retrospective, case-control study in adult patients with E. faecalis bacteremia. Thirty-nine patients with definite E. faecalis IE and 82 with E. faecalis bacteremia were included. The addition of a TTP ≤ 8 h to DENOVA-score did not improve the diagnostic accuracy of this score.

Risk Factors for Persistent Staphylococcus aureus Bacteremia in Children

BACKGROUND

Staphylococcus aureus is a leading cause of pediatric bacteremia. Persistent S. aureus bacteremia (SAB) is associated with increased morbidity and mortality in adults and children. Risk factors for S. aureus bacteremia have been well established, but there is a limited understanding of the factors that contribute to the development of persistent SAB in children.

METHODS

This is a single-center retrospective secondary analysis of a prospective observational study of pediatric patients hospitalized with S. aureus infection over a 3.5-year period at a large, quaternary, children's hospital.

RESULTS

Two hundred fifty-nine children with confirmed S. aureus infection were enrolled in the study. Sixty-five of these were found to have bacteremia, with 28 (43%) developing persistent bacteremia. Patients with persistent SAB were culture-positive for a median of 3.5 days compared with 1 day for those without (P ≤ 0.001). Children with persistent SAB were more likely to have an identified osteoarticular source of infection (93%, n = 26 vs. 62%, n = 23; P = 0.008) and had a shorter median duration to culture positivity than those without persistent SAB (16 hours vs. 20 hours; P ≤ 0.001). In addition, children with persistent SAB had higher median values of presenting erythrocyte sedimentation rate, peak erythrocyte sedimentation rate, presenting C-reactive protein and peak C-reactive protein. Not surprisingly, hospital length of stay was longer in children with persistent SAB compared with those without.

CONCLUSIONS

These findings suggest that a shorter time to culture positivity, osteoarticular infection, and higher presenting and peak values for select inflammatory markers are potential risk factors for persistent SAB in children.

Sequential Time to Positivity as a Prognostic Indicator in Staphylococcus aureus Bacteremia

Background

We aimed to determine the factors associated with sequential blood culture time to positivity (STTP) and validate the previously defined time to positivity (TTP) ratio threshold of 1.5 in predicting adverse disease outcomes and mortality of Staphylococcus aureus bacteremia (SAB).

Methods

We conducted an observational study of adult patients with SAB. The TTP ratio was calculated by dividing the TTP of the second blood culture by that of the first.

Results

Of 186 patients, 69 (37%) were female, with a mean age of 63.6 years. Median TTP was 12 hours (interquartile range [IQR], 10-15 hours) from the initial and 21 hours (17-29) from sequential blood cultures. Methicillin-resistant S aureus (MRSA)-infected patients had significantly shorter STTPs (P < .001) and lower TTP ratios (P < .001) compared to patients with methicillin-susceptible S aureus (MSSA). A significant correlation between initial and STTP was observed in patients with MRSA (r = 0.42, P = .002) but not in those with MSSA. A higher rate of native valve endocarditis (NVE) significantly correlated with a TTP ratio of ≤1.5 (odds ratio, 2.65 [95% confidence interval, 1.3-5.6]; P = .01). The subgroup having an initial TTP <12 hours combined with a TTP ratio ≤1.5 showed the highest prevalence of NVE.

Conclusions

The STTP varies based on methicillin susceptibility of S aureus isolate. This study suggests a potential clinical utility of the STTP to identify patients at a higher risk of NVE. However, prospective studies are required to validate these findings.

Relationship between blood culture time to positivity, mortality rate, and severity of bacteremia

OBJECTIVES

We investigated the association between patient severity or mortality and time to positivity in bacteremia caused by various pathogens.

PATIENTS AND METHODS

This single-center retrospective study included patients with positive blood culture results.

RESULTS

Longer time to positivity was associated with 30-day mortality for Staphylococcus aureus (221 cases, time to positivity: 17.4 h in the 30-day mortality group vs. 14.1 h in the survival group). Age, chronic kidney disease, cerebrovascular disease, hypertensive drug use, consciousness disorder, and minimal systolic blood pressure were significant predictors of 30-day mortality. For S. aureus, mortality within 30 days was significantly higher when time to positivity was > 24 h (p = 0.04). The time to positivity of Streptococcus pneumoniae, α, β-hemolytic Streptococcus, Enterococcus sp., Enterobacteriaceae, glucose-nonfermenting Gram-negative rods, Candida sp., and anaerobe was not significantly associated with 30-day mortality.

CONCLUSIONS

Among various pathogens, time to positivity > 24 h was associated with 30-day mortality for S. aureus.

Bacteraemia with gram-positive bacteria-when and how do I need to look for endocarditis?

BACKGROUND

Patients with bacteraemia caused by gram-positive bacteria are at risk for infective endocarditis (IE). Because IE needs long antibiotic treatment and sometimes heart valve surgery, it is very important to identify patients with IE.

OBJECTIVES

In this narrative review we present and discuss how to determine which investigations to detect IE that are needed in individual patients with gram-positive bacteraemia.

SOURCES

Published original studies and previous reviews in English, within the relevant field are used.

CONTENT

First, the different qualities of the bacteraemia in relation to IE risk are discussed. The risk for IE in bacteraemia is related to the species of the bacterium but also to monomicrobial bacteraemia and the number of positive cultures. Second, patient-related factors for IE risk in bacteraemia are presented. Next, the risk stratification systems to determine the risk for IE in gram-positive bacteraemia caused by Staphylococcus aureus, viridans streptococci, and Enterococcus faecalis are presented and their use is discussed. In the last part of the review, an account for the different modalities of IE-investigations is given. The main focus is on echocardiography, which is the cornerstone of IE-investigations. Furthermore, 18F-fluorodesoxyglucose positron emission tomography/computed tomography and cardiac computed tomography are presented and their use is also discussed. A brief account for investigations used to identify embolic phenomena in IE is also given. Finally, we present a flowchart suggesting which investigations to perform in relation to IE in patients with gram-positive bacteraemia.

IMPLICATIONS

For the individual patient as well as the healthcare system, it is important both to diagnose IE and to decide when to stop looking for IE. This review might be helpful in finding that balance.

Quantification of bacterial DNA in blood using droplet digital PCR: a pilot study

We used droplet digital PCR (ddPCR) assays to detect/quantify DNA from Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus spp. in blood samples. Bacterial DNA from clinical strains (4 < n < 12) was extracted, quantified and diluted (10-0.0001 ng/µL) and ddPCR assays were performed in triplicate. These ddPCR assays showed low replication variability, low detection limit (1-0.1 pg/µL), and genus/species specificity. ddPCR assays were also used to quantify bacterial DNA obtained from spiked blood (1 × 104-1 CFU/mL) of each bacterial genus/species. Comparison between ddPCR assays and bacterial culture was performed by Pearson correlation. There was an almost perfect correlation (r ≥ 0.997, P ≤ 0.001) between the number of CFU/mL from bacterial culture and the number of gene copies/mL detected by ddPCR. The time from sample preparation to results was determined to be 3.5 to 4 hours. The results demonstrated the quantification capacity and specificity of the ddPCR assays to detect/quantify 4 of the most important bloodstream infection (BSI) bacterial pathogens directly from blood. SIGNIFICANCE AND IMPACT: This pilot study results support the potential of ddPCR for the diagnosis and/or severity stratification of BSI. Applied to patients' blood samples it can improve diagnosis and diminish sample-to-results time, improving patient care.

Factors for mortality in patients with persistent Staphylococcus aureus bacteremia: The importance of treatment response rather than bacteremia duration

BACKGROUND

The criteria for antibiotic failure in persistent Staphylococcus aureus bacteremia (SAB) are unclear, but treatment response and bacteremia duration are commonly used indicators of antibiotic failure. We evaluated the effects of treatment response and bacteremia duration on mortality in persistent SAB.

METHODS

We retrospectively identified patients with persistent SAB in four university-affiliated hospitals between 2017 and 2021. Bacteremia duration was calculated from the first day of active antibiotic therapy, and persistent SAB was defined as bacteremia lasting for 2 or more days. Defervescence and Pitt bacteremia score (PBS) were used to evaluate treatment response at treatment day 4. The primary outcome was 30-day in-hospital mortality. Time-dependent multivariable Cox regression analysis and subgroup analysis according to methicillin resistance were performed.

RESULTS

A total of 221 patients was included in the study, and the 30-day in-hospital mortality was 28.5%. There was no significant difference in bacteremia duration between survived and deceased patients. Independent factors for mortality included age, Charlson comorbidity index, initial PBS, pneumonia, and removal of the eradicable focus. PBS at treatment day 4 ≥ 3 was the strongest risk factor (adjusted hazard ratio [HR] = 4.260), but defervescence was not. Bacteremia duration was not an independent factor except for 13 days or more of methicillin-resistant SAB (adjusted HR = 1.064).

CONCLUSIONS

In patients with persistent SAB, PBS at treatment day 4 was associated with 30-day in-hospital mortality rather than defervescence and bacteremia duration. The results of this study could help determine early intensified treatment strategies in persistent SAB patients.

Time to positivity of blood cultures in bloodstream infections with Streptococcus dysgalactiae and association with outcome

PURPOSE

Invasive infections with Streptococcus dysgalactiae predominantly occur in persons of older age with substantial morbidity and mortality. Time to positivity from blood cultures (TTP) has been shown to be a prognostic indicator in bloodstream infections caused by other beta-haemolytic streptococci. This study aimed to determine any possible association between TTP and outcome in invasive infections due to S. dysgalactiae.

MATERIALS AND METHODS

Episodes of S. dysgalactiae bacteraemia, that occurred during 2015-2018 in the Region of Skåne, Sweden, were identified through the laboratory database and retrospectively studied. Any association with TTP and the primary outcome, death within 30 days and the development of sepsis or disease deterioration within 48 hours from blood culturing as secondary outcomes were investigated.

RESULTS

Among the 287 episodes of S. dysgalactiae bacteraemia, 30-day mortality rate was 10% (n = 30). Median TTP was 9.3 h (interquartile range 8.0-10.3 h). Median TTP was statistically significantly shorter in patients who died within 30 days compared to surviving patients (7.7 vs 9.3 h, p = .001, Mann-Whitney U test). Short TTP(≤ 7.9 h) was still associated with 30-day mortality when adjusting for age, (OR 4.4, 95% CI 1.6-12.2, p = .004). Associations between secondary outcomes and levels of TTP were not observed.

CONCLUSION

TTP may be an important prognostic indicator for 30-day mortality in patients with bloodstream infections due to S. dysgalactiae.

Inappropriate empirical antibiotic therapy was an independent risk factor of pediatric persistent S. aureus bloodstream infection

Persistent S. aureus bloodstream infection (PSBSI) increased the incidence of metastatic infection and mortality. We aimed to clarify its risk factors and correlation with metastatic infection and septic shock in children. This retrospective and observational study enrolled children with S. aureus bloodstream infection who admitted to Children's Hospital of Chongqing Medical University between January 2016 and December 2021. The logistic regression model was used for multivariable analyses to determine independent factors associated with PSBSI and clarify the effect of persistent S. aureus bloodstream infection and other factors on metastatic infection and septic shock. One hundred and twenty-seven children were included in this study retrospectively. There were thirty-two cases in the persistent S. aureus bloodstream infection group and ninety-five children in the non-persistent infection group. Multivariate logistic regression analysis indicated that inappropriate empirical antibiotic therapy (OR, 7.26; 95%CI, 2.48-21.30; P<0.01) was an independent risk factor of persistent S. aureus bloodstream infection. Persistent S. aureus bloodstream infection (OR, 6.40; 95%CI, 2.08-19.70; P<0.01) and community-acquired S. aureus bloodstream infection (OR, 4.75; 95%CI, 1.34-16.89; P=0.02) were independent predictors of metastatic infection. Pittsburgh bacteremia scores ≥ 2 (OR, 28.81; 95%CI, 5.26-157.99; P<0.01), hypoalbuminemia (OR, 13.34; 95%CI, 2.43-73.28; P<0.01) and persistent S. aureus bloodstream infection (OR, 5.48; 95%CI, 1.13-26.54; P=0.04) were independent risk factors of septic shock.

CONCLUSION

Inappropriate empirical antibiotic therapy was an independent risk factor of pediatric persistent S. aureus bloodstream infection. Pediatric persistent S. aureus bloodstream infection was associated with metastatic infection and septic shock.

WHAT IS KNOWN

• Pathogenic features such as Methicillin-resistant S. aureus and sources of infection such as central venous catheter related infection were risk factors of PSBSI in adults. • PSBSI increased the incidence of metastatic infection and mortality in adults.

WHAT IS NEW

• Inappropriate empirical antibiotic therapy was an independent risk factor of pediatric persistent S. aureus bloodstream infection. • Pediatric persistent S. aureus bloodstream infection was associated with metastatic infection and septic shock.

Redefining Staphylococcus aureus bacteremia: A structured approach guiding diagnostic and therapeutic management

The current duration of therapy in patients with Staphylococcus aureus bacteremia (SAB) is based on differentiating complicated from uncomplicated disease. While this approach allows clinicians and investigators to group SAB patients into broadly similar clinical categories, it fails to account for the intrinsic heterogeneity of SAB. This is due in part to the fact that risk factors for metastatic infection and confirmed metastatic infection are considered as equivalent in most scoring systems. In this viewpoint, we propose a two-step system of categorizing patients with SAB. Initially, patients with SAB would be categorized as 'high risk' or 'low risk' for metastatic infection based upon an initial set of diagnostic procedures. In the second step, patients identified as 'high-risk' would undergo additional diagnostic evaluation. The results of this stepwise diagnostic evaluation would define a 'final clinical diagnosis' to inform an individualized final treatment plan.

Development of a Multiplex Polymerase Chain Reaction-Based DNA Lateral Flow Assay as a Point-of-Care Diagnostic for Fast and Simultaneous Detection of MRSA and Vancomycin Resistance in Bacteremia

To reduce high mortality and morbidity rates, timely and proper treatment of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection is required. A multiplex polymerase reaction (mPCR)-based DNA lateral flow assay (MBDLFA) was developed as a point-of-care diagnostic for simultaneous identification of S. aureus, methicillin resistance, and vancomycin resistance directly from blood or blood cultures. A mPCR was developed to detect nuc, mecA, and vanA/B; its sensitivity, specificity, and limit of detection (LOD) were determined. The developed reaction was further modified for use in MBDLFA and its sensitivity for detection of target genes from artificially inoculated blood samples was checked. The optimized mPCR successfully detected nuc, mecA, and vanA/B from genomic DNA of bacterial colonies with LODs of 107, 107, and 105 CFU/mL, respectively. The reaction was sensitive and specific. The optimized mPCR was used in MBDLFA that detected nuc, mecA, and vanA/B with LODs of 107, 108, and 104 CFU/mL, respectively, directly from artificially inoculated blood. The developed MBDLFA can be used as a rapid, cheap point-of-care diagnostic for detecting S. aureus, MRSA, and vancomycin resistance directly from blood and blood cultures in ~2 h with the naked eye. This will reduce morbidity, mortality, and treatment cost in S. aureus bacteremia.

Bacterial DNA load in Staphylococcus aureus bacteremia is significantly higher in intravascular infections

OBJECTIVES

Determination of pathogen-specific bacterial DNA load (BDL) in blood has been shown to be directly correlated with severity of infection in patients with bacteremia. In the diagnostic work-up of patients with Staphylococcus aureus bacteremia (SAB), determination of the primary focus is imperative, because of implications for treatment duration, and ultimately prognosis. Here we investigate whether measurement of BDL in patients with SAB can distinguish between intravascular and extravascular foci of infection.

METHODS

In a consecutive cohort of 43 patients with positive blood cultures with Staphylococcus aureus, we performed a quantitative PCR on whole blood to detect the bacterial DNA load. Infections were classified into 3 categories: i) soft tissue infections and phlebitis, ii) deep-seated infections and iii) endocarditis and other intravascular infections. Bacterial DNA loads and inflammatory parameters in the three categories were analyzed and compared.

RESULTS

Median BDL in patients with endocarditis and other intravascular infections was 1015 cfu/ml, significantly higher than BDL in the other two categories (28 and 31 cfu/ml respectively). In contrast, CRP and leukocytes were not significantly different between the three patient categories. BDL could be detected in all patients with intravascular causes and levels were generally 10-30 times higher than in the other infection categories. Median BDL in non-survivors was 85 cfu/ml, which was higher than in survivors with a median BDL of 29 cfu/ml, although not significant.

CONCLUSIONS

In Staphylococcus aureus bacteremia pathogen-specific BDL is distinctly higher in patients with intravascular infections compared to extravascular origins. As measurement of BDL by PCR can easily be implemented in routine diagnostics, it can improve the diagnostic work-up of SAB by rapidly identifying the subset of patients who need higher dosages of antibiotics and additional measures to improve outcome.

Clinical prediction scores and the utility of time to blood culture positivity in stratifying the risk of infective endocarditis in Staphylococcus aureus bacteraemia

Background

Infective endocarditis (IE) complicates up to a quarter of Staphylococcus aureus bacteraemia (SAB) cases. Risk scores predict IE complicating SAB but have undergone limited external validation, especially in community-acquired infections and those who use IV drugs. Addition of the time to positive culture (TTP) may provide incremental risk prognostication.

Objectives

To externally validate risk scores for predicting IE in SAB and assess the incremental value of TTP.

Methods

The modified Duke score was calculated for adults hospitalized with SAB at a major tertiary institution. All patients underwent echocardiography. Sensitivity and specificity of the risk scores for predicting IE were calculated, and the incremental value of TTP was assessed.

Results

One hundred and six cases were analysed and 18 (17%) met definite IE criteria. The optimal TTP to predict IE was 11.5 h (sensitivity 88.9%; specificity 71.6%). The sensitivity of VIRSTA and PREDICT (Predicting risk of endocarditis using a clinical tool) were similar (94.4% for both) and higher than POSITIVE (Prediction Of Staphylococcus aureus Infective endocarditis Time to positivity, IV drug use, Vascular phenomena, pre-Existing heart condition; 77.8%). The receiver-operator characteristic AUCs were VIRSTA 0.83, PREDICT 0.75, POSITIVE 0.89 and TTP 0.85. Adding TTP to VIRSTA (i.e. VIRSTA+) resulted in the highest AUC (0.90), sensitivity (100%) and negative predictive value (100%), albeit with a low specificity (33%).

Conclusions

The VIRSTA and POSITIVE scores were the strongest predictors for IE complicating SAB. The addition of TTP to VIRSTA (VIRSTA+) significantly improved discriminatory value and may be safely used to rationalize echocardiography strategies.

Digital PCR applications for the diagnosis and management of infection in critical care medicine

Infection (either community acquired or nosocomial) is a major cause of morbidity and mortality in critical care medicine. Sepsis is present in up to 30% of all ICU patients. A large fraction of sepsis cases is driven by severe community acquired pneumonia (sCAP), which incidence has dramatically increased during COVID-19 pandemics. A frequent complication of ICU patients is ventilator associated pneumonia (VAP), which affects 10–25% of all ventilated patients, and bloodstream infections (BSIs), affecting about 10% of patients. Management of these severe infections poses several challenges, including early diagnosis, severity stratification, prognosis assessment or treatment guidance. Digital PCR (dPCR) is a next-generation PCR method that offers a number of technical advantages to face these challenges: it is less affected than real time PCR by the presence of PCR inhibitors leading to higher sensitivity. In addition, dPCR offers high reproducibility, and provides absolute quantification without the need for a standard curve. In this article we reviewed the existing evidence on the applications of dPCR to the management of infection in critical care medicine. We included thirty-two articles involving critically ill patients. Twenty-three articles focused on the amplification of microbial genes: (1) four articles approached bacterial identification in blood or plasma; (2) one article used dPCR for fungal identification in blood; (3) another article focused on bacterial and fungal identification in other clinical samples; (4) three articles used dPCR for viral identification; (5) twelve articles quantified microbial burden by dPCR to assess severity, prognosis and treatment guidance; (6) two articles used dPCR to determine microbial ecology in ICU patients. The remaining nine articles used dPCR to profile host responses to infection, two of them for severity stratification in sepsis, four focused to improve diagnosis of this disease, one for detecting sCAP, one for detecting VAP, and finally one aimed to predict progression of COVID-19. This review evidences the potential of dPCR as a useful tool that could contribute to improve the detection and clinical management of infection in critical care medicine.

The Impact of Implementing the Virtuo Blood Culture System on the Characteristics and Management of Patients with Staphylococcus aureus Bacteremia

Persistent Staphylococcus aureus bacteremia (SAB) has been associated with increased mortality. Enhanced microbial detection with new blood culture technology may improve detection of S. aureus in patients with SAB. We performed a 24-month retrospective study of hospitalized adults with SAB and an infectious diseases consult comparing two time periods pre- (January to December 2018) and postimplementation (January to December 2019) in which the VersaTREK and BacT/Alert Virtuo blood culture systems were used, respectively. Measurements included SAB duration, time to positivity, source of bacteremia, antimicrobial therapy, and mortality. A total of 416 episodes of SAB occurred during the study period: 176 (42%) pre- and 240 (58%) postimplementation. Patients in both periods had similar clinical characteristics; however, patients in the postimplementation period were more likely to have intermediate (3 to 6 days; 23% versus 40%; P < 0.001) and prolonged SAB duration (>7 days; 4% versus 14%; P < 0.001). Combination antistaphylococcal therapy was more frequent postimplementation (6.3% pre- versus 15.8% postimplementation; P = 0.003), and the median time to source control was shorter (4 versus 2 days; P = 0.02). Median time to positivity for the index blood culture was shorter postimplementation (17.8 h pre- versus 13.3 h postimplementation; P < 0.001). There was no difference in 90-day all-cause readmissions (51% versus 44%; P = 0.11) or mortality (32% versus 32%; P = 0.95). An increased frequency of prolonged SAB with increased use of combination antistaphylococcal therapy was noted with implementation of a new blood culture system, likely secondary to the blood culture media; however, no differences on adverse outcomes were noted.

A longitudinal population-based study of predictors of mortality from bloodstream infections in Calgary, Alberta, Canada

Aim: To study the predictors of mortality from nine major pathogens causing approximately 70% of cases over a 7-year period. Materials & methods: A population-based surveillance cohort of all adult and pediatric patients in the Calgary Zone with an initial episode of bloodstream infections (BSI). Results: The 1-year mortality was 29.2% among 9524 patients (5164 males [54%]). Incidence rates for BSI increased annually to 119.7/100,000 persons by 2016. Distinct survival curves were found for each specific pathogen. Age, comorbidity burden and infecting organism were significantly associated with increased hazard of death. No relationship occurred between the time to positivity for blood cultures and overall mortality. Conclusion: BSI has a high mortality, but overall survival depends on underlying host health and the type of pathogen acquired.

Blood culture time to positivity in non-β-hemolytic streptococcal bacteremia as a predictor of infective endocarditis-a retrospective cohort study

Non-β-hemolytic streptococci (NBHS) cause infective endocarditis (IE) and a short blood culture time to positivity (TTP) is associated with risk of IE in bacteremia with other pathogens. In this retrospective population-based cohort study, we investigate if TTP is associated to IE or mortality. Of 263 episodes with NBHS bacteremia, 28 represented IE and the median TTP did not differ significantly between episodes with IE (15 h) and non-IE (15 h) (p=0.51). TTP was similar among those who survived and those who died within 30 days. However, TTP significantly differed when comparing the different streptococcal groups (p<0.001).

Infección metastásica por Staphylococcus aureus en neonatos: a propósito de un caso

Metastatic infection as an infrequent complication of Staphylococcus aureus bacteremia in neonates is challenging due to the limited literature. To report the clinical case of a premature neonate who developed a metastatic infection as a complication of S. aureus bacteremia. We present the case of a premature neonate admitted to the Neonatal Intensive Care Unit, diagnosed with bacterial sepsis, neonatal respiratory distress syndrome, and involvement by premature rupture of the membrane. A patch catheter was inserted, and he was successfully treated for E. coli bacteremia. He was re-admitted for late sepsis due to infection with multi-sensitive S. aureus in a patch catheter. An abscess appears on the front of the chest due to S. aureus, confirming metastatic infection. The abscess was drained with a favorable resolution of the clinical picture. In neonates submitted to invasive procedures, it is essential to monitor the clinical evolution and early identification of metastatic infection after Staphylococcus aureus bacteremia and provide early treatment to avoid sequelae.

Prediction rules for ruling out endocarditis in patients with Staphylococcus aureus bacteremia

Background

Staphylococcus aureus bacteremia (SAB) is in 10% to 20% of cases complicated by infective endocarditis. Clinical prediction scores may select patients with SAB at highest risk for endocarditis, improving the diagnostic process of endocarditis. We compared the accuracy of the Prediction Of Staphylococcus aureus Infective endocarditiseTime to positivity, Iv drug use, Vascular phenomena, preExisting heart condition (POSITIVE), Predicting Risk of Endocarditis Using a Clinical Tool (PREDICT), and VIRSTA scores for classifying the likelihood of endocarditis in patients with SAB.

Methods

Between August 2017 and September 2019, we enrolled consecutive adult patients with SAB in a prospective cohort study in 7 hospitals in the Netherlands. Using the modified Duke Criteria for definite endocarditis as reference standard, sensitivity, specificity, negative predictive (NPV), and positive predictive values were determined for the POSITIVE, PREDICT, and VIRSTA scores. An NPV of at least 98% was considered safe for excluding endocarditis.

Results

Of 477 SAB patients enrolled, 33% had community-acquired SAB, 8% had a prosthetic valve, and 11% a cardiac implantable electronic device. Echocardiography was performed in 87% of patients, and 42% received transesophageal echocardiography (TEE). Eighty-seven (18.2%) had definite endocarditis. Sensitivity was 77.6% (65.8%–86.9%), 85.1% (75.8%–91.8%), and 98.9% (95.7%–100%) for the POSITIVE (n = 362), PREDICT, and VIRSTA scores, respectively. NPVs were 92.5% (87.9%–95.8%), 94.5% (90.7%–97.0%), and 99.3% (94.9%–100%). For the POSITIVE, PREDICT, and VIRSTA scores, 44.5%, 50.7%, and 70.9% of patients with SAB, respectively, were classified as at high risk for endocarditis.

Conclusions

Only the VIRSTA score had an NPV of at least 98%, but at the expense of a high number of patients classified as high risk and thus requiring TEE.

Clinical Trials Registration

Netherlands Trial Register code 6669.

Time to positivity as a prognostic factor in bloodstream infections with Enterococcus spp

Time to positivity (TTP) is the delay of time from incubation to blood culture positivity. Short TTP can predict mortality and source of infection. The aim of this study was to investigate the value of TTP of patients with bloodstream infections with enterococci (E-BSI).In a single centre retrospective cohort study in Germany, the data of 244 patients with monomicrobial E-BSI were analyzed with hospital mortality as the primary outcome of interest from January 1 2014 to December 31 2016. Mortality rate of patients with bloodstream infections (BSI) with E. faecalis was 16.7%, Vancomycin sensitive E. faecium (VSEfm) 26.7% and Vancomycin resistant E. faecium (VREfm) 38.2%. Cut-offs showed a significantly higher mortality rate when compared to longer TTP (E. faecalis: P=0.047; VSEfm: P=0.02), but were not risk factors in survival analysis (E.faecalis: HR (hazard ratio): 2.73; P=0.17; VSEfm: HR: 1.63; P=0.15; VREfm: HR: 1.24; P=0.63). TTP≤10.5 hours with E. faecalis BSI was a discriminator for cardiovascular source of infection (AUC: 0.75). A short TTP could predict mortality rates and source of infection but was not an independent parameter for risk of death in survival analysis.

Determinants and outcomes of bloodstream infection in adults associated with one versus two sets of positive index blood cultures

OBJECTIVES

To investigate whether positivity in one or both index sets of blood cultures influences clinical determinants and mortality when diagnosing bloodstream infections (BSI).

METHODS

Retrospective population-based surveillance of all mono-microbial BSI was conducted among residents of the western interior of British Columbia. Clinical details were obtained by chart review and all-cause case-fatality was established at 30 days. Index cultures were defined as the first two sets of cultures initially drawn to diagnose incident BSI.

RESULTS

A total of 2500 incident BSI were identified of which 945 (37.8%) and 1555 (62.2%) were based on one and two positive index cultures, respectively. There was an overall difference in the distribution of pathogens, with both Staphylococcus aureus and Streptococcus pneumoniae more likely to have two positive index cultures. Different foci of infection were associated with one versus two positive index cultures. Overall, 409 patients died within 30 days of index BSI for an all-cause case-fatality of 16.4%; with no difference between two positive (250/1555; 16.1%) and one positive (159/945; 16.8%; p 0.3) index blood culture. The number of positive index blood cultures was not associated with 30-day case-fatality after adjustment for confounding variables using logistic regression analysis.

CONCLUSIONS

Although approximately one-third of BSI are diagnosed on the basis of a single positive blood culture and are associated with different clinical determinants, whether one or both index blood cultures are positive is not associated with lethal outcome.

Short time to blood culture positivity in Enterococcus faecalis infective endocarditis

Time to blood culture positivity (TTP) is an indirect measure of bacterial concentration in blood. A short TTP has been linked to the presence of infective endocarditis (IE) and to poor prognosis in Staphylococcus aureus bacteremia. We analyze factors influencing TTP in bacteremia with Enterococcus faecalis. This retrospective observational study of medical records included adults diagnosed with monomicrobial E. faecalis bacteremia between 2015 and 2018 in the Skåne region (Sweden). For each episode, the shortest TTP was recorded. Median TTP was compared between patients grouped based on age, sex, comorbidity, site of acquisition, and focus of infection. Using a dichotomized TTP (shorter or longer than 12 h), a multivariable logistic regression for factors associated to TTP was performed. The association between TTP and IE or mortality was evaluated. Three hundred sixty-seven episodes with monomicrobial E. faecalis bacteremia with the corresponding TTP were identified. Median TTP for the entire cohort was 11.6 (IQR 9.9–14.1) h and a significantly shorter TTP was noted for episodes which represented IE (n = 55, 9.4 (IQR 6.4–10.6) h). Only IE remained associated with a short TTP (≤ 12 h) in binary logistic regression analysis. Factors associated with IE were investigated and TTP was associated with IE also when adjusted for age, gender, comorbidity, and nosocomial acquisition. There was no association between TTP and mortality. A low TTP is associated with IE in E. faecalis bacteremia and could be used as a help in determining the need for echocardiography in patients with this condition.

Time to blood culture positivity in Staphylococcus aureus bacteraemia to determine risk of infective endocarditis

OBJECTIVES

Patients with Staphylococcus aureus bacteraemia (SAB) at risk for infective endocarditis (IE) need to be identified because they should undergo echocardiography. We validated previous scoring systems for IE risk determination and evaluated whether time to blood culture positivity (TTP) could improve scoring systems.

METHODS

This retrospective population-based study included adults with SAB in 2016 in a derivation cohort and those from 2017 in a validation cohort. TTP was compared between patients with and without IE. A new score including TTP was constructed using a least absolute shrinkage selection operator. The new POSITIVE score was compared to the previously described PREDICT and VIRSTA scores.

RESULTS

A total of 465 episodes with SAB were included in the derivation cohort, of which 38 (8.2%) represented IE. Median (interquartile range) TTP was significantly shorter in episodes with IE, at 8.7 (7.7-10.6) hours compared to those without, at 13.3 (10.5-16.5) hours. When using a cutoff at 13 hours, TTP had a sensitivity of 100% (95% confidence interval (CI), 91-100) and specificity of 52% (95% CI, 47-57) for IE. The POSITIVE score included TTP, intravenous drug use, embolizations and presence of preexisting heart conditions. It had a sensitivity of 93% (95% CI, 76-99) and a specificity of 70% (95% CI, 66-74) in the validation cohort. The performance of POSITIVE was superior to PREDICT, and the specificity was higher than that of VIRSTA.

CONCLUSIONS

TTP, either by itself or as part of the POSITIVE score, can be used to identify patients with SAB at low risk for IE. Further validation is needed because TTP is sensitive to several external factors.

Time to positivity of Klebsiella pneumoniae in blood culture as prognostic indicator for pediatric bloodstream infections

The aim of this study is to explore the prognostic values and optimal cutoff point of time to positivity (TTP) of blood culture in children with Klebsiella pneumoniae (K. pneumoniae) bloodstream infection. Ninety-four children with K. pneumoniae bloodstream infection hospitalized in Children's Hospital of Chongqing Medical University from April 2014 to January 2019 were enrolled retrospectively. TTP and risk factors were determined and analyzed by receiver operating characteristic (ROC) analysis and logistic regression analysis. The standard cutoff point of TTP was 13 h. Patients in early TTP (≤ 13 h) group had significantly higher in-hospital mortality (37.93% vs 6.15%, P = 0.000), higher incidence of septic shock (44.83% vs 6.15%, P = 0.000), higher proportion of PRISM III scores ≥ 10 (48.28% vs 20.00%, P = 0.005), and higher proportion of hypoalbuminemia on admission (44.83% vs 18.46%, P = 0.008). Multivariate analysis indicated PRISM III scores ≥ 10, early TTP, and hypoalbuminemia on admission were independent risk factors of in-hospital mortality (OR 8.36, 95% CI 1.80-38.92, P = 0.007; OR 5.85, 95% CI 1.33-25.61, P = 0.019; OR 5.73, 95% CI 1.30-25.22, P = 0.021, respectively) and septic shock (OR 14.04, 95% CI 2.63-75.38, P = 0.002; OR 11.26, 95% CI 2.10-60.22, P = 0.005; OR 10.27, 95% CI 2.01-52.35, P = 0.005, respectively).Conclusion: Early TTP (TTP ≤ 13 h), PRISM III scores ≥ 10, and hypoalbuminemia on admission appeared to be associated with worse outcomes for K. pneumoniae bloodstream infection children. What is Known: • Klebsiella pneumoniae bloodstream infection is an important cause of infectious disease morbidity and mortality worldwide in children. • Short duration of time to positivity indicated poor clinical outcomes. What is New: • Time to positivity ≤ 13 h, along with PRISM III scores ≥ 10 and hypoalbuminemia on admission, indicated higher in-hospital mortality and incidence of septic shock in Klebsiella pneumoniae bloodstream infection children. • The cut-off point of TTP in this pediatric study was much longer than that reported in adult patients.

A novel flow cytometry assay based on bacteriophage-derived proteins for Staphylococcus detection in blood

Bloodstream infections (BSIs) are considered a major cause of death worldwide. Staphylococcus spp. are one of the most BSIs prevalent bacteria, classified as high priority due to the increasing multidrug resistant strains. Thus, a fast, specific and sensitive method for detection of these pathogens is of extreme importance. In this study, we have designed a novel assay for detection of Staphylococcus in blood culture samples, which combines the advantages of a phage endolysin cell wall binding domain (CBD) as a specific probe with the accuracy and high-throughput of flow cytometry techniques. In order to select the biorecognition molecule, three different truncations of the C-terminus of Staphylococcus phage endolysin E-LM12, namely the amidase (AMI), SH3 and amidase+SH3 (AMI_SH3) were cloned fused with a green fluorescent protein. From these, a higher binding efficiency to Staphylococcus cells was observed for AMI_SH3, indicating that the amidase domain possibly contributes to a more efficient binding of the SH3 domain. The novel phage endolysin-based flow cytometry assay provided highly reliable and specific detection of 1-5 CFU of Staphylococcus in 10 mL of spiked blood, after 16 hours of enrichment culture. Overall, the method developed herein presents advantages over the standard BSIs diagnostic methods, potentially contributing to an early and effective treatment of BSIs.

16S rDNA droplet digital PCR for monitoring bacterial DNAemia in bloodstream infections

Repeated quantitative measurement of bacterial DNA on whole blood has been shown to be a promising method for monitoring bloodstream infection (BSI) with selected bacterial species. To enable broad use of this method, we developed a quantitative droplet digital PCR (ddPCR) method for 16S rDNA. It was validated with species-specific ddPCRs for Staphylococcus aureus (nuc), Streptococcus pneumoniae (lytA), and Escherichia coli (uidA) on spiked whole blood samples and on repeated whole blood samples (days 0, 1–2, 3–4, 6–8, and 13–15) from 83 patients with BSI with these pathogens. In these patients, 16S rDNA and species-specific DNA were detected in 60% and 61%, respectively, at least at one time-point. The highest positivity rates were seen in S. aureus BSI, where 92% of the patients were 16S rDNA-positive and 85% nuc-positive. Quantitative 16S rDNA and species-specific DNA showed strong correlations in spiked samples (r = 0.98; p < 0.0001) and clinical samples (r = 0.84; p < 0.0001). Positivity for 16S rDNA was rapidly cleared in patients with S. pneumoniae and E. coli BSI, but more slowly and sometimes persisted, in those with S. aureus BSI. The initial 16S rDNA load was higher in BSI patients with sepsis (Sepsis-3 definition) than without sepsis (median 2.38 vs. 0 lg10 copies/mL; p = 0.031) and in non-survivors than in survivors (median 2.83 vs. 0 lg10 copies/mL; p = 0.006). 16S rDNA ddPCR appears to be a promising method for bacterial DNA monitoring during BSI. The clinical value of such monitoring should be further studied.

Burden of bacterial bloodstream infection-a brief update on epidemiology and significance of multidrug-resistant pathogens

BACKGROUND

Bloodstream infections comprise a wide variety of pathogens and clinical syndromes with considerable overlap with similar syndromes of non-bacteraemic infections and diverse risk factors, therapeutic implications and outcomes. Yet, this heterogeneous 'entity' has the advantage to be pathogen-defined compared with the broad and even more heterogeneous entity 'sepsis', and so has become helpful for clinicians and epidemiologists for research and surveillance purposes. The increasing availability of population-based and large multicentre well-defined cohort studies should allow us to assess with much confidence and in detail its burden, the significance of antimicrobial resistance, and areas of uncertainty regarding further epidemiological evolution and optimized treatment regimens.

AIM

To review key aspects of bloodstream infection epidemiology and burden, and summarize recent news and questions concerning critical developments.

SOURCES

Peer-reviewed articles based on the search terms 'bloodstream infection' and 'bacteremia' combined with the terms 'epidemiology' and 'burden'. The emphasis was on new information from studies in adult patients and on the added burden due to pathogen resistance to first- and second-line antimicrobial agents.

CONTENT

Topics covered include recent developments in the epidemiology of bloodstream infection due to key pathogens and published information about the relevance of resistance for patient outcomes.

IMPLICATIONS

Despite the availability of population-based studies and an increasing number of large well-defined multicentre cohort studies, more surveillance and systematic data on bloodstream infection epidemiology at regional level and in resource-limited settings may be needed to better design new methods for prevention and define the need for and further develop optimized therapeutic strategies.

Metastatic infection during Staphylococcus aureus bacteremia

Staphylococcus aureus causes various infections, including skin and soft tissue infections and pneumonia via both, community-associated and nosocomial infection. These infectious diseases can lead to bacteremia, and may subsequently result in metastatic infections in several cases. Metastatic infections are critical complications in patients with S. aureus bacteremia, since the optimal duration of the antimicrobial treatment differs in patients with and without metastatic infection. Notably, two weeks of antimicrobial treatment is recommended in case of uncomplicated S. aureus bacteremia, whereas in patients with S. aureus bacteremia-associated endocarditis or vertebral osteomyelitis, six weeks of antimicrobial administration is vital. In addition, misdiagnosis or insufficient treatment in metastatic infection is associated with poor prognosis, functional disability, and relapse. Although echocardiography is recommended to examine endocarditis in the patients with S. aureus bacteremia, it remains unclear which patients should undergo additional examinations, such as CT and MRI, to detect the presence of other metastatic infections. Clinical studies have revealed that permanent foreign body and persistent bacteremia are predictive factors for metastatic infections, and experimental studies have demonstrated that the virulence factors of S. aureus, such as fnbA and clfA, are associated with endocarditis; however, these factors are not proven to increase the risk of metastatic infections. In this review, we assessed the incidence, predictive factors, diagnosis, and treatment for metastatic infections during S. aureus bacteremia.

Excluding Clinically Significant Bacteremia by 24 Hours in Otherwise Well Febrile Children Younger Than 16 Years: A Study of More Than 50,000 Blood Cultures

BACKGROUND

In febrile children given empiric parenteral antibiotics, guidelines advise provisional reporting of negative blood cultures and antibiotic review after 36 hours incubation for neonates and 48 hours for older children. Following improvements in culture processing and childhood vaccination, we revisited this important clinical topic, assessing time to exclude clinically significant bacteremia in well-appearing febrile children with no comorbidities or features of sepsis.

METHODS

We analyzed the results of all 53,276 pediatric blood cultures taken during an 8-year period at a UK hospital.

RESULTS

1308 (2.5%) cultures were positive, of which 333 (25.5%) grew pathogens typically associated with clinically significant bacteremia. The remaining 975 (74.5%) grew organisms associated with contaminated culture, or with opportunistic infection only in children with relevant risk factors. Time to positivity (TTP) from incubation was significantly shorter for the 333 definite pathogens than the 975 contaminating/opportunistic organisms, with 92% of definite pathogens identified by 24 hours incubation. Only 3 of all definite pathogens were identified after 24 hours in children otherwise eligible for discharge at 24 hours. There was no significant difference in TTP for definite pathogens between neonates and older children. Median time from specimen collection to incubation was 3 hours.

CONCLUSIONS

Clinically significant bacteremia can be excluded by 24 hours incubation in well-appearing febrile children with no comorbidities or features of sepsis. This is the largest dataset of its kind, and the second to compare neonates and older children. Our findings may inform future guidelines, facilitating earlier antibiotic review and discharge.

Time to positivity of blood culture is a risk factor for clinical outcomes in Staphylococcus aureus bacteremia children: a retrospective study

BACKGROUND

Staphylococcus aureus (S. aureus) is a common cause of bacteremia, which leads to significant morbidity and mortality. We investigated the relationship between time to positivity (TTP) and clinical outcomes in children with S.aureus bacteremia in the China.

METHODS

A retrospective study of Staphylococcus aureus bacteremia inpatient was performed in Children's Hospital of Chongqing Medical University in China between 29 January 2014 and 29 August 2017. TTP and clinical parameters were determined and analyzed. The receiver operating characteristic (ROC) curves were plotted for optimal cut-off selection, multivariate logistic regression tests were performed to evaluate the association between TTP and clinical outcomes.

RESULTS

Overall, 84 cases were enrolled. We stated that in-hospital mortality is significantly higher in the early TTP (≤17 h) than in the late TTP (> 17 h) group (57.14% vs 7.14%, P = 0.000). Septic shock occurred in 57.14% of patients with early TTP and in 18.57% of patients with late TTP (P = 0.002). Detailed multivariate and statistical analysis revealed that early TTP, need for vasoactive agent were independent risk factors of in-hospital mortality; early TTP, need for vasoactive agent and APACHE II score ≥ 15 were independent risk factors of septic shock incidence in S. aureus bacteremia children.

CONCLUSIONS

Overall, TTP of ≤17 h appeared to correlate with the worse outcomes for S. aureus bacteremia children. These results have important implications in the assessments and management of pediatric S. aureus bacteremia in a clinical setting.

TRIAL REGISTRATION

Retrospectively registered.

Prognostic Power of Pathogen Cell-Free DNA in Staphylococcus aureus Bacteremia

BACKGROUND

Staphylococcus aureus is a leading global cause of bacteremia that can cause invasive tissue infections with high morbidity and mortality despite appropriate antibiotic therapy. Clinicians lack sufficient tools to rapidly identify patients with a poor prognosis to guide diagnostic workup and treatment decisions. Host cell-free DNA provides prognostic value across a spectrum of critical illnesses, including S. aureus bacteremia and sepsis. Metrics of high bacterial load are associated with disease severity in S. aureus bacteremia, and the objective of this study was to evaluate whether incorporating quantitation of cell-free bacterial DNA would provide additive prognostic value when combined with biomarkers of the inflammatory response.

METHODS

S. aureus cell-free DNA was measured by quantitative polymerase chain reaction (PCR) in baseline serum samples from an observational cohort of 111 patients with complicated S. aureus bacteremia and correlated with host inflammatory markers and clinical outcomes.

RESULTS

High levels of S. aureus cell-free DNA at the time of positive index blood culture were prognostic for all-cause and attributable mortality and persistent bacteremia and were associated with infective endocarditis. However, they did not provide additive value to biomarkers of the host response to infection in multivariate analysis.

CONCLUSIONS

Measurements of bacterial load by PCR are a clinically feasible candidate biomarker for stratifying patients at higher risk for complications and poor outcomes. Their diagnostic and prognostic value for identifying foci of infection and influencing treatment remain to be evaluated in additional cohorts.

High nuc DNA load in whole blood is associated with sepsis, mortality and immune dysregulation in Staphylococcus aureus bacteraemia

BACKGROUND

Staphylococcus aureus bacteraemia is a disease with varying presentation, ranging from uncomplicated to life-threatening infections. In S. aureus bacteraemia, a high load of bacterial DNA in blood has been linked to mortality. We hypothesized that a high DNA load would also be linked to the presence of sepsis, and to high C-reactive protein (CRP) and lymphopaenia, indicating inflammation and immunosuppression.

METHODS

Twenty-seven patients with culture-proven S. aureus bacteraemia, 13 (48%) with sepsis and six (22%) non-survivors, were enrolled in a prospective study. Blood samples were collected on days 0, 1-2, 3-4, 6-8, 13-15 and 26-30, and subjected to droplet digital PCR targeting the nuc gene to determine the nuc DNA load.

RESULTS

nuc DNA was detected on days 0-2 in 22 patients (81%), and on days 6-8 in three patients (all non-survivors). The nuc DNA load on days 1-2 was significantly elevated in patients with sepsis (median 2.69 versus 1.32 log10 copies/mL; p = .014) and in non-survivors (median 2.5 versus 1.0 log10 copies/mL; p = .033). Patients with a high nuc DNA load (>3.0 log10 copies/mL) on days 1-2 had significantly elevated CRP levels at all timepoints, and significantly decreased lymphocyte counts on days 0, 1-2, 13-15 and 26-30.

CONCLUSIONS

Our results indicate that a high initial load of S. aureus DNA in blood is associated with sepsis, mortality and persistent immune dysregulation in S. aureus bacteraemia patients. Further studies are needed to define the role of bacterial DNA load monitoring in the management of S. aureus bacteraemia.

Expression of HLA-DRA and CD74 mRNA in whole blood during the course of complicated and uncomplicated Staphylococcus aureus bacteremia

To improve management of Staphylococcus aureus bacteremia (SAB), better understanding of host-pathogen interactions is needed. In vitro studies have shown that S. aureus bacteria induce dose-dependent immunosuppression that is evidenced by reduced expression of major histocompatibility complex (MHC) class II on antigen presenting cells. Thus, the aim of this study was to determine whether expression of the MHC class II-related genes HLA-DRA and CD74 is more greatly reduced in complicated SAB, with its probable higher loads of S. aureus, than in uncomplicated SAB. Adult patients with SAB were prospectively included and blood samples taken on the day of confirmation of SAB (Day 1) and on Days 2, 3, 5 and 7. HLA-DRA and CD74 mRNA expression was determined by quantitative reverse transcription PCR. Sepsis was defined according to the Sepsis-3 classification and SAB was categorized as complicated in patients with deep-seated infection and/or hematogenous seeding. Twenty patients with SAB were enrolled and samples obtained on all assessment days. HLA-DRA and CD74 expression did not differ significantly between patients with SAB and sepsis (n = 13) and those without sepsis (n = 7) on any assessment day. However, patients with complicated SAB (n = 14) had significantly weaker HLA-DRA expression on all five assessment days than patients with uncomplicated SAB (n = 6). Additionally, they tended to have weaker CD74 expressions. Neutrophil, monocyte and leukocyte counts did not differ significantly between complicated and uncomplicated SAB. In conclusion, patients with complicated SAB show weaker HLA-DRA expression than those with uncomplicated SAB during the first week of bacteremia.

Clinical predictors and clinical prediction rules to estimate initial patient risk for infective endocarditis in Staphylococcus aureus bacteraemia: a systematic review and meta-analysis

OBJECTIVES

We conducted a meta-analysis to summarize diagnostic properties of risk factors and clinical prediction rules for diagnosing infective endocarditis (IE) in Staphylococcus aureus bacteraemia (SAB).

METHODS

We searched MEDLINE, Embase, and the Cochrane Database from inception to 6 January 2016 to identify studies evaluating risk factors and clinical prediction rules for IE in SAB patients. Pooled estimates of diagnostic properties for main risk factors were calculated using a bivariate random effects model.

RESULTS

Of 962 articles identified, 30 studies were included. These involved 16 538 SAB patients including 1572 IE cases. Risk factors with positive likelihood ratio (PLR) greater than 5 included embolic events (PLR 12.7, 95% CI 9.2-17.7), pacemakers (PLR 9.7, 95% CI 3.7-21.2), history of previous IE (PLR 8.2, 95% CI 3.1-22.0), prosthetic valves (PLR 5.7, 95% CI 3.2-9.5), and intravenous drug use (PLR 5.2, 95% CI 3.8-6.9). The only clinical factor with negative likelihood ratio (NLR) less than 0.5 was documented clearance of bacteraemia within 72 hours (NLR range 0.32-0.35). Of the nine published clinical prediction rules for ruling out IE, five had an NLR below 0.1.

CONCLUSIONS

SAB patients with high-risk features (embolic events, pacemakers, prosthetic valves, previous IE, or intravenous drug use) should undergo a trans-esophageal echocardiography (TEE) for IE. Clinical prediction rules show promise in safely ruling out endocarditis, but require validation in future studies.

Impact of Pharmacy Practice Model Expansion on Pharmacokinetic Services: Optimization of Vancomycin Dosing and Improved Patient Safety

Background: The impact of pharmacy interventions on optimizing vancomycin therapy has been described, however interventions vary among studies and the most optimal pharmacy practice model (PPM) for pharmacokinetic (PK) services has not been established. Objective: The purpose of this study is to demonstrate the value of 24 hours a day, 7 days a week (24/7) PK services. Methods: New PK services were implemented in 2 phases with institutional PPM expansion. Phase 1 included universal monitoring by pharmacists with recommendations made to prescribers during business hours. Phase 2 expanded clinical pharmacists' coverage to 24/7 and provided an optional 24/7 pharmacist-managed PK consult service. We compared vancomycin therapeutic trough attainment, dosing, and clinical and safety outcomes between phases 1 and 2 in adult inpatients receiving therapeutic intravenous vancomycin. Results. One hundred and fifty patients were included in each phase. Phase 2 had a greater proportion of vancomycin courses with therapeutic initial trough concentrations (27.5% vs 46.1%; p = 0.002), higher initial trough concentrations (10.9 mcg/mL vs 16.4 mcg/mL; p < 0.001), and optimized initial vancomycin dosing (13.5 mg/kg vs 16.2 mg/kg; p < 0.001). Phase 2 also saw significant reduction in the incidence of vancomycin-associated nephrotoxicity (21.1% vs 11.7%; p = 0.038). Dose optimization and improvement in initial target trough attainment were most notable among intensive care unit (ICU) patients. Conclusions. Our study demonstrated that 24/7 PK services implemented with institutional PPM expansion optimized vancomycin target trough attainment and improved patient safety.

Time to positivity of blood cultures in patients with bloodstream infections: A useful prognostic tool

OBJECTIVE

The time to positivity (TTP) of blood cultures in patients with bloodstream infections (BSIs) has been considered to be a possible prognostic tool for some bacterial species. However, notable differences have been found between sampling designs and statistical methods in published studies to date, which makes it difficult to compare results or to derive reliable conclusions. Our objective was to evaluate the clinical and microbiological implications of TTP among patients with BSI caused by the most common pathogens.

METHODS

A total of 361 episodes of BSI were reported for 332 patients. The survival of the entire cohort was measured from the time of blood culture sampling. In order to compare our results with those of previous studies, TTP was divided in three different groups based on log rank (short TTP <12h; medium TTP ≥12h to ≤27h, and long TTP >27h). Cox proportional hazard models were used to calculate crude and adjusted hazard ratios (HR).

RESULTS

The Cox proportional hazard model revealed that TTP is an independent predictor of mortality (HR=1.00, p=0.031) in patients with BSIs. A higher mortality was found in the group of patients with the shortest TTP (<12h) (HR=2.100, p=0.047), as well as those with longest TTP (>27h) (HR=3.277, p=0.031).

CONCLUSIONS

It seems that TTP may provide a useful prognostic tool associated with a higher risk of mortality, not only in patients with shorter TTP, but also in those with longer TTP.