Criteria for Identifying Patients With Staphylococcus aureus Bacteremia Who Are at Low Risk of Endocarditis: A Systematic Review

Performance of Risk Scores in Predicting Infective Endocarditis in Patients with Staphylococcus aureus Bacteraemia in a Prospective Asian Cohort

Background: Several risk scores have been derived to predict the risk of infective endocarditis (IE) amongst patients with Staphylococcus aureus bacteraemia (SAB), which helps to guide clinical management. Methods: We prospectively studied 634 patients admitted with SAB. The cohort was stratified into those with or without IE, and the PREDICT Day 1, Day 5 and VIRSTA scores were tabulated. Area under the receiver operating characteristic (AUC) curves were constructed to compare the performance of each score. Results: Of the 634 patients examined, 36 (5.7%) had IE. These patients were younger (51.6 ± 20.1 vs. 59.2 ± 18.0 years, p = 0.015), tended to have community acquisition of bacteraemia (41.7% vs. 17.9%, p < 0.001), and had persistent bacteraemia beyond 72 h (19.4% vs. 6.0%, p = 0.002). The VIRSTA score had the best performance in predicting IE (AUC 0.76, 95%CI 0.66-0.86) compared with PREDICT Day 1 and Day 5. A VIRSTA score of <3 had the best negative predictive value (97.5%), compared with PREDICT Day 1 (<4) and Day 5 (<2) (94.3% and 96.6%, respectively). Conclusions: Overall, the risk scores performed well in our Asian cohort. If applied, 23.5% of the cohort with a VIRSTA ≥ 3 would require TEE, and a score of <3 had an excellent negative predictive value.

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.

Unreliability of Clinical Prediction Rules to Exclude without Echocardiography Infective Endocarditis in Staphylococcus aureus Bacteremia

BACKGROUND

It is unclear whether the use of clinical prediction rules is sufficient to rule out infective endocarditis (IE) in patients with Staphylococcus aureus bacteremia (SAB) without an echocardiogram evaluation, either transthoracic (TTE) and/or transesophageal (TEE). Our primary purpose was to test the usefulness of PREDICT, POSITIVE, and VIRSTA scores to rule out IE without echocardiography. Our secondary purpose was to evaluate whether not performing an echocardiogram evaluation is associated with higher mortality.

METHODS

We conducted a unicentric retrospective cohort including all patients with a first SAB episode from January 2015 to December 2020. IE was defined according to modified Duke criteria. We predefined threshold cutoff points to consider that IE was ruled out by means of the mentioned scores. To assess 30-day mortality, we used a multivariable regression model considering performing an echocardiogram as covariate.

RESULTS

Out of 404 patients, IE was diagnosed in 50 (12.4%). Prevalence of IE within patients with negative PREDICT, POSITIVE, and VIRSTA scores was: 3.6% (95% CI 0.1-6.9%), 4.9% (95% CI 2.2-7.7%), and 2.2% (95% CI 0.2-4.3%), respectively. Patients with negative VIRSTA and negative TTE had an IE prevalence of 0.9% (95% CI 0-2.8%). Performing an echocardiogram was independently associated with lower 30-day mortality (OR 0.24 95% CI 0.10-0.54, p = 0.001).

CONCLUSION

PREDICT and POSITIVE scores were not sufficient to rule out IE without TEE. In patients with negative VIRSTA score, it was doubtful if IE could be discarded with a negative TTE. Not performing an echocardiogram was associated with worse outcomes, which might be related to presence of occult IE. Further studies are needed to assess the usefulness of clinical prediction rules in avoiding echocardiographic evaluation in SAB patients.

Oral step-down therapy in patients with uncomplicated Staphylococcus aureus primary bacteremia and catheter-related bloodstream infections

Patients with uncomplicated Staphylococcus aureus primary bacteremia and catheter-related bloodstream infection (CRBSI) should be treated for at least 14 days. However, evidence for oral step-down therapy is lacking in these patients. A retrospective cohort was identified from 2013 to 2018 in a 1,950-bed tertiary hospital. An oral antimicrobial therapy (OAT) group was defined as patients treated with oral antibiotics following less than 10 days of intravenous antimicrobial therapy (IAT). Treatment failure was defined as any case of recurrence or death within 90 days. A total of 103 patients were included in the analysis, including 32 patients treated with OAT. Rates of treatment failure were 3.2% and 12.7% in the OAT and IAT groups (P = 0.113). The length of hospital stay was shorter in the OAT group. OAT was not an independent risk factor for treatment failure. OAT may reduce the duration of hospitalization without adverse effects in these patients.

Staphylococcus Aureus Infective Endocarditis: JACC Patient Pathways

A 19-year-old female patient presented with Staphylococcus aureus infective endocarditis, with suspected subdural brain hemorrhage, disseminated intravascular coagulopathy, and septic renal as well as spleen infarcts. The patient had extensive vegetations on the mitral and tricuspid valves and underwent urgent mitral and tricuspid repair. This paper discusses the clinical case and current evidence regarding the management and treatment of Staphylococcus aureus endocarditis.

Staphylococcus Aureus Infective Endocarditis: JACC Patient Pathways

A 19-year-old female patient presented with Staphylococcus aureus infective endocarditis, with suspected subdural brain hemorrhage, disseminated intravascular coagulopathy, and septic renal as well as spleen infarcts. The patient had extensive vegetations on the mitral and tricuspid valves and underwent urgent mitral and tricuspid repair. This paper discusses the clinical case and current evidence regarding the management and treatment of Staphylococcus aureus endocarditis.

Efficacy of Early Oral Switch with β-Lactams for Low-Risk Staphylococcus aureus Bacteremia

The aim of this study was to assess the safety of early oral switch (EOS) prior to 14 days for low-risk Staphylococcus aureus bacteremia (LR-SAB), which is the primary treatment strategy used at our institution. The usual recommended therapy is 14 days of intravenous (i.v.) antibiotics. All patients with SAB at our hospital were identified between 1 January 2014 and 31 December 2018. Those meeting low-risk criteria (health care-associated, no evidence of deep infection or demonstrated involvement of prosthetic material, and no further positive blood cultures after 72 h) were included in the study. The primary outcome was occurrence of a SAB-related complication within 90 days. There were 469 SAB episodes during the study period, 100 (21%) of whom met inclusion criteria. EOS was performed in 84 patients. In this group, line infection was the source in 79%, methicillin-susceptible S. aureus caused 95% of SABs and 74% of patients received i.v. flucloxacillin. The median durations of i.v. and oral antibiotics in the EOS group were 5 days (interquartile range [IQR], 4 to 6) and 10 days (IQR, 9 to 14), respectively. A total of 71% of patients received flucloxacillin as their EOS agent. Overall, 86% of oral step-down therapy was with beta-lactams. One patient (1%) undergoing EOS had SAB relapse within 90 days. No deaths attributable to SAB occurred within 90 days. In this low-MRSA-prevalence LR-SAB cohort, EOS was associated with a low incidence of SAB-related complications. This was achieved with oral beta-lactam therapy in most patients. Larger prospective studies are needed to confirm these findings.

A Scenario-Based Survey of Expert Echocardiography Recommendations for Patients With Staphylococcus aureus Bacteremia at Varying Risk for Endocarditis

IMPORTANCE

Echocardiography to detect infective endocarditis is regarded as a key quality indicator in the care of patients with Staphylococcus aureus bacteremia, but its application varies markedly between reported series. Understanding the reasons for this variation in practice is important to improve the use of this investigation.

OBJECTIVE

To identify expert clinicians' preferred echocardiography strategy for a variety of S aureus bacteremia scenarios in a hypothetical setting free from extrinsic constraints.

DESIGN, SETTING, AND PARTICIPANTS

Anonymous web-based survey study comprising 50 text-based scenarios describing patients with S aureus bacteremia and various combinations of risk factors for endocarditis. Other variables included patient age and the presence of an extracardiac focus of infection warranting prolonged treatment. The survey was emailed to participants between September 2018 and March 2019. Each respondent was asked to recommend 1 of 6 echocardiography strategies for up to 8 randomly selected scenarios. Respondents were primarily infectious diseases physicians, and more than half reported an annual caseload of more than 20 cases of S aureus bacteremia.

MAIN OUTCOMES AND MEASURES

The proportion of respondents selecting each of the 6 echocardiography strategies was calculated alongside Wilson score confidence intervals. Modified Fleiss κ statistics were used to described interrespondent variability. Generalized estimating equations were used to assess the associations between respondent- and scenario-level variables and the recommendation of an echocardiography strategy with a low negative likelihood ratio for infective endocarditis (ie, a highly exclusionary strategy).

RESULTS

A total of 656 respondents from 24 countries provided 4837 echocardiography recommendations across the 50 scenarios. Echocardiography recommendations were associated with scenarios' burden of endocarditis risk (multivariate odds ratio per point of the VIRSTA score, 1.4; 95% CI, 1.4-1.5; P < .001). Poor interrespondent agreement was seen across all scenarios (modified Fleiss κ, 0.06; 95% CI, 0.05-0.07) but was most notable for scenarios with a lower risk of endocarditis (modified Fleiss κ, 0.04; 95% CI, 0.03-0.05). The presence of an extracardiac focus of infection was also associated with the choice of echocardiography strategy (odds ratio for highly exclusionary strategy, 0.51; 95% CI, 0.45-0.58). Respondent location in continental Europe was associated with recommendations in favor of a highly exclusionary strategy (odds ratio, 1.8; 95% CI, 1.3-2.5) compared with location in Australia or New Zealand.

CONCLUSIONS AND RELEVANCE

In this study, expert clinicians demonstrated active stratification by risk of endocarditis when making echocardiography recommendations for hypothetical patients with S aureus bacteremia. Substantial disagreement existed as to whether patients at lower risk of endocarditis should undergo transesophageal echocardiography-based echocardiography 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.

Benefit of Echocardiography in Patients With Staphylococcus aureus Bacteremia at Low Risk of Endocarditis

Background

The risk of endocarditis among patients with Staphylococcus aureus bacteremia is not uniform, and a number of different scores have been developed to identify patients whose risk is less than 5%. The optimal echocardiography strategy for these patients is uncertain.

Methods

We used decision analysis and Monte Carlo simulation using input parameters taken from the existing literature. The model examined patients with S aureus bacteremia whose risk of endocarditis is less than 5%, generally those with nosocomial or healthcare-acquired bacteremia, no intracardiac prosthetic devices, and a brief duration of bacteremia. We examined 6 echocardiography strategies, including the use of transesophageal echocardiography, transthoracic echocardiography, both modalities, and neither. The outcome of the model was 90-day survival.

Results

The optimal echocardiography strategy varied with the risk of endocarditis and the procedural mortality associated with transesophageal echocardiography. No echocardiography strategy offered an absolute benefit in 90-day survival of more than 0.5% compared with the strategy of not performing echocardiography and treating with short-course therapy. Strategies using transesophageal echocardiography were never preferred if the mortality of this procedure was greater than 0.5%.

Conclusions

In patients identified to be at low risk of endocarditis, the choice of echocardiography strategy appears to exert a very small influence on 90-day survival. This finding may render test-treatment trials unfeasible and should prompt clinicians to focus on other, more important, management considerations in these patients.

What risk of endocarditis is low enough to justify the omission of transoesophageal echocardiography in Staphylococcus aureus bacteraemia? A narrative review

BACKGROUND

Recent criteria which can identify patients with Staphylococcus aureus bacteraemia (SAB) who are at very low risk of endocarditis raise the question of whether transoesophageal echocardiography (TOE) is appropriate for these patients.

AIMS

To estimate the probability of occult endocarditis complicating SAB below which a TOE-guided treatment strategy no longer offers the best 180-day survival, and to examine the key uncertainties affecting this result.

SOURCES

Estimates of the parameters required to calculate the Pauker-Kassirer testing threshold were identified from studies published prior to 1 June 2017 using a composite search strategy that involved a systematic search for relevant controlled trials and guidelines, followed by a non-systematic iterative search of the observational literature.

CONTENT

Estimates of the necessary parameters were generally consistent across the literature with the exception of the procedural mortality of TOE. In our base-case scenario (TOE mortality 0.1%), the testing threshold for TOE in apparently uncomplicated SAB was a 1.1% probability of occult endocarditis. Sensitivity analyses revealed that the procedural mortality of TOE was a key uncertainty affecting estimates of the testing threshold.

IMPLICATIONS

None of the available clinical tools can place patients with SAB below this probability of endocarditis with 95% confidence. Future work in this area should concentrate on improving the precision of these tools and on exploring the value of alternative echocardiography strategies. In addition, a better understanding of the harms of TOE is required to ensure that recommendations regarding the role of this investigation in the management of patients with SAB are appropriate.