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

Contemporary Management of Staphylococcus aureus Bacteremia-Controversies in Clinical Practice

Staphylococcus aureus bacteremia (SAB) carries a high risk for excess morbidity and mortality. Despite its prevalence, significant practice variation continues to permeate clinical management of this syndrome. Since the publication of the 2011 Infectious Diseases Society of America (IDSA) guidelines on management of methicillin-resistant Staphylococcus aureus infections, the field of SAB has evolved with the emergence of newer diagnostic strategies and therapeutic options. In this review, we seek to provide a comprehensive overview of the evaluation and management of SAB, with special focus on areas where the highest level of evidence is lacking to inform best practices.

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.

Role of echocardiography in uncomplicated Staphylococcus aureus catheter-related bloodstream infections

Uncomplicated bacteremia and catheter-related bloodstream infection (CRBSI) are frequently suggested as factors associated with low risk of infective endocarditis in Staphylococcus aureus bacteremia (SAB). Nevertheless, guidelines recommend that echocardiography in all patients with SAB. We evaluated the effects of echocardiography on patient outcomes. Patients with uncomplicated S. aureus CRBSI were retrospectively identified between January 2013 and June 2018 at a 1950-bed, tertiary-care university hospital. Treatment failure was defined as any case of relapse or all-cause death within 90 days. Of 890 SAB patients, 95 with uncomplicated S. aureus CRBSI were included. Thirty-two patients underwent echocardiography within 30 days of their first positive blood culture. Two patients who underwent echocardiography revealed right-sided infective endocarditis. One patient who did not undergo echocardiography experienced recurrent SAB (peripheral CRBSI) 85 days after his first positive blood culture. There were no SAB-related deaths. The Kaplan-Meier curves of treatment failure showed no significant differences between patients who did and did not undergo echocardiography (P = .77). In multivariable analysis, risk factors for treatment failure were liver cirrhosis (hazard ratio: 9.60; 95% confidence interval: 2.13-43.33; P = .003) and other prostheses (hazard ratio: 63.79; 95% confidence interval: 5.05-805.40; P = .001). This study did not verify the putative association between treatment failure and implementation of echocardiography in patients with uncomplicated S. aureus CRBSI. Given the low observed rates of adverse outcomes, routine echocardiography might not be obligatory and could be performed on an individual basis.

Validation of VIRSTA and Predicting Risk of Endocarditis Using a Clinical Tool (PREDICT) Scores to Determine the Priority of Echocardiography in Patients With Staphylococcus aureus Bacteremia

Background

Infective endocarditis (IE) secondary to Staphylococcus aureus bacteremia (SAB) has high morbidity and mortality. The systematic use of echocardiography in SAB is controversial. We aimed to validate VIRSTA and Predicting Risk of Endocarditis Using a Clinical Tool (PREDICT) scores for predicting the risk of IE in Colombian patients with SAB and, consequently, to determine the need for echocardiography.

Methods

Cohort of patients hospitalized with SAB in 2 high complexity institutions in Medellin, Colombia, between 2012 and 2018. The diagnosis of IE was established based on the modified Duke criteria. The VIRSTA and PREDICT scores were calculated from the clinical records, and their operational performance was calculated.

Results

The final analysis included 922 patients, 62 (6.7%) of whom were diagnosed with IE. The frequency of IE in patients with a negative VIRSTA scale was 0.44% (2/454). The frequency of IE in patients with a negative PREDICT scale on day 5 was 4.8% (30/622). The sensitivity and negative predictive value (NPV) of the VIRSTA scale was 96.7% and 99.5%, respectively. For the PREDICT scale on day 5, the sensitivity and NPV were 51.6% and 95.1%, respectively. The discrimination, given by the area under the receiver operating characteristic curve, was 0.86 for VIRSTA and 0.64 for PREDICT.

Conclusions

In patients with negative VIRSTA, screening echocardiography may be unnecessary because of the low frequency of IE. In PREDICT-negative patients, despite the low frequency of IE, it is not safe to omit echocardiography.

Forgoing transesophageal echocardiogram in selected patients with complicated Staphylococcus aureus bacteremia

Infective endocarditis (IE) has been increasingly recognized as an important complication of Staphylococcus aureus bacteremia (SAB), leading to a low threshold for echocardiography and extended treatment with anti-staphylococcal agents. However, outside of IE, many indications for prolonged anti-staphylococcal therapy courses are present. We sought to determine the frequency in which findings from a transesophageal echocardiogram (TEE) changed clinical SAB management in a large Canadian health region. Residents (> 18 years) with SAB from 2012 to 2014 who underwent transthoracic echocardiogram (TTE) and TEE were assessed. Patients potentially benefiting from an extended course of anti-staphylococcal agents were defined a priori. Patient demographics, treatment (including surgical), and clinical outcomes were extracted and evaluated. Of the 705 episodes of SAB that underwent a screening echocardiogram, 203 episodes underwent both a TTE and TEE, of which 92.1% (187/203) contained an a priori indication for extended anti-staphylococcal therapy. Regardless of TEE results, actual duration of therapy did not differ in SAB episodes that had ≥ 1 extended anti-staphylococcal therapy criteria (36.7 days, IQR 23.4-48.6 vs. 43.8 days, IQR 33.3-49.5, p = 0.17). Additionally, there were no cases in which TEE was utilized as the sole reason to shorten duration of therapy or proceed to surgery for those with SAB. Routine performance of TEE may be unnecessary in all SAB as many patients have pre-existing indications for extended anti-staphylococcal therapy independent of TEE findings. An algorithm to selectively identify cases of SAB that would benefit from TEE can reduce resource and equipment expenditure and patient risks associated with TEE.

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.

Adherence to standards of care and mortality in the management of Staphylococcus aureus bacteraemia in Peru: A prospective cohort study

BACKGROUND

Despite high mortality rates, physicians can alter the course of the Staphylococcus aureus bacteraemia (SAB) by following recommended standards of care. We aim to assess the adherence of these guidelines and their impact on mortality.

METHODS

Substudy from a prospective cohort of hospitalized patients with SAB from three hospitals from Peru. Hazard ratios were calculated using Cox proportional regression to evaluate the association between 30-day mortality and the performance of standards of care: removal of central venous catheters (CVC), follow-up blood cultures, echocardiography, correct duration, and appropriate definitive antibiotic therapy.

RESULTS

150 cases of SAB were evaluated; 61.33% were MRSA. 30-day attributable mortality was 22.39%. CVC removal was done in 42.86% of patients. Follow-up blood cultures and echocardiograms were performed in 8% and 29.33% of cases, respectively. 81.33% of cases had appropriate empirical treatment, however, only 22.41% of MSSA cases were given appropriate definitive treatment, compared to 93.47% of MRSA. The adjusted regression for all-cause mortality found a substantial decrease in hazards when removing CVC (aHR 0.28, 95% CI: 0.10 - 0.74) and instituting appropriate definitive treatment (aHR 0.27, 95% CI: 0.08 - 0.86), while adjusting for standards of care, qPitt bacteraemia score, comorbidities, and methicillin susceptibility; similar results were found in the attributable mortality model (aHR 0.24, 95% CI: 0.08 - 0.70 and aHR 0.21, 95% CI: 0.06 - 0.71, respectively).

CONCLUSIONS

Deficient adherence to standards of care was observed, especially definitive treatment for MSSA. CVC removal and the use of appropriate definitive antibiotic therapy reduced the hazard mortality of SAB.

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.