Transesophageal Echocardiograms in Patients with Catheter-derived Staphylococcus aureus Bacteremia

Abstract

In the evaluation of a bacteremic patient, the clinician should determine the origin and possible destinations of the invading pathogen. As a result of medical progress, intravenous catheters have become a distressingly common portal of entry. Fortunately, most bacteria do not regularly seed endovascular structures, with the notable exception of Staphylococcus aureus, which has a predilection to settle on both normal and damaged tissues. Consequently, every patient developing a bloodstream infection with S. aureus is at risk for endocarditis and other metastatic infections, although the likelihood varies with the source and circumstances.In line with current recommendations, transesophageal echocardiography (TEE) is performed routinely where available, in patients with catheter-associated S. aureus bacteremia to help determine the length of antibiotic therapy.1Mermel L.A. Allon M. Bouza E. et al.Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 update by the Infectious Diseases Society of America.Clin Infect Dis. 2009; 49: 1-45Crossref PubMed Scopus (2271) Google Scholar However, too often our unflinching fascination with cutting-edge technologies has led to unconditional (rather than carefully qualified) endorsements for sophisticated diagnostic testing in already well-managed conditions.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar Past experience and clinical acumen are cast aside impulsively in the rush. Now coming almost full circle, recent analyses have persuasively challenged the reflexive use of TEE in all patients with catheter-associated S. aureus bacteremia.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google ScholarProponents of TEE in this context contend that clinical assessment alone is inadequate to differentiate patients with endocarditis from those with uncomplicated bacteremia, even in the absence of predisposing conditions.1Mermel L.A. Allon M. Bouza E. et al.Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 update by the Infectious Diseases Society of America.Clin Infect Dis. 2009; 49: 1-45Crossref PubMed Scopus (2271) Google Scholar, 5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar, 6Rasmussen R.V. Høst U. Arpi M. et al.Prevalence of infective endocarditis in patients with Staphylococcus aureus bacteraemia: the value of screening with echocardiography.Eur J Echocardiogr. 2011; 12: 414-420Crossref PubMed Scopus (109) Google Scholar This observation conflicts with much of the pre-TEE literature and substantial anecdotal experience before echocardiography.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Nonetheless, compelling data from TEE indicate that we had been missing subclinical cases of endocarditis.5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar How do we resolve this unnerving paradox?Endocarditis can be a potentially life-threatening (albeit infrequent) consequence of line-related S. aureus bacteremia. Long-term treatment had become the standard of care for established valvular infection long before modern imaging modalities were ever anticipated. However, in the absence of cellulitis or thrombophlebitis at the former catheter insertion site or evidence of active infection elsewhere, treatment of line-related bacteremia for more than a few days after line removal is intended to preemptively eradicate possible occult foci of staphylococcal infection. TEE apparently has uncovered heretofore undetectable valvular seeding that may otherwise have never become manifest if appropriate interventions were initiated soon after the onset of catheter-derived bacteremia.Before TEE, carefully selected patients with line-related S. aureus bacteremia (including some who would have had positive TEEs if available) were treated successfully with prompt removal of the inciting focus, followed by 10-14 days of antibiotics.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Candidates for short-course therapy included patients without valvular disease in whom the catheter was quickly pulled, the bacteremia persisted <48 hours thereafter, the clinical response was rapid and complete, no hardware remained, and signs of metastatic infection never supervened during therapy.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google ScholarTEE has operationally redefined endocarditis.5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar Do prior algorithms mandating ≥4 weeks of antibiotics de facto apply to early cases formerly undiagnosable in real time? Incipient S. aureus endocarditis identifiable exclusively by TEE might be eradicated with shorter courses,2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar analogously to β-lactam monotherapy for tricuspid endocarditis without apparent left-sided involvement.9Ribera E. Gomez-Jimenez J. Cortes E. et al.Effectiveness of cloxacillin with and without gentamicin in short-term therapy for right-sided Staphylococcus aureus endocarditis A randomized, controlled trial.Ann Intern Med. 1996; 125: 969-974Crossref PubMed Scopus (161) Google ScholarAlthough subclinical endocarditis must have complicated seemingly uncomplicated S. aureus bacteremia in the pre-TEE era, 2 weeks of antibiotics were reliably curative.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Low-risk patients fully and unequivocally responding to catheter removal plus/minus a few days of antibiotics should still be curable with a 2-week course, irrespective of whether TEE can visualize a silent vegetation.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, 9Ribera E. Gomez-Jimenez J. Cortes E. et al.Effectiveness of cloxacillin with and without gentamicin in short-term therapy for right-sided Staphylococcus aureus endocarditis A randomized, controlled trial.Ann Intern Med. 1996; 125: 969-974Crossref PubMed Scopus (161) Google Scholar, 10Bendig E.A. Singh J. Butler T.J. Arrieta A.C. The impact of the central venous catheter on the diagnosis of infectious endocarditis using Duke criteria in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 636-639Crossref PubMed Scopus (15) Google Scholar, 11Pigrau C. Rodríguez D. Planes A.M. et al.Management of catheter-related Staphylococcus aureus bacteremia: when may sonographic study be unnecessary?.Eur J Clin Microbiol Infect Dis. 2003; 22: 713-719Crossref PubMed Scopus (41) Google Scholar, 12Ross A.C. Toltzis P. O'Riordan M.A. et al.Frequency and risk factors for deep focus of infection in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 396-399Crossref PubMed Scopus (16) Google Scholar The incremental risk:benefit ratio of several additional weeks of intravenous antibiotic administration has not been established for these patients. In addition to the occasional complication from an invasive procedure, indiscriminate TEE might paradoxically be injurious when therapy is unnecessarily prolonged. Appropriate shortening of antibiotic courses can reduce iatrogenic complications, ironically decreasing the risk of recurrent line-related septicemia.Thus, TEE may be postponed indefinitely in stable low-risk patients with S. aureus bacteremia who quickly become asymptomatic upon catheter removal and never exhibit any signs of metastatic infection for complementary reasons. Firstly, the low pretest probability of endocarditis in this subgroup makes costly procedures unlikely to yield true positive findings.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google Scholar, 11Pigrau C. Rodríguez D. Planes A.M. et al.Management of catheter-related Staphylococcus aureus bacteremia: when may sonographic study be unnecessary?.Eur J Clin Microbiol Infect Dis. 2003; 22: 713-719Crossref PubMed Scopus (41) Google Scholar, 12Ross A.C. Toltzis P. O'Riordan M.A. et al.Frequency and risk factors for deep focus of infection in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 396-399Crossref PubMed Scopus (16) Google Scholar Secondly, even when the TEE is positive in isolation, duration of therapy need not automatically be extended.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar However, the patient must be interviewed and examined daily for subtle or transient signs of endocarditis or other metastatic infection, and the final decision to administer only 2 weeks of antibiotics not made until the 14th day of therapy. If the patient's status changes, a TEE can always be performed at that time and the course of treatment adjusted accordingly. In the evaluation of a bacteremic patient, the clinician should determine the origin and possible destinations of the invading pathogen. As a result of medical progress, intravenous catheters have become a distressingly common portal of entry. Fortunately, most bacteria do not regularly seed endovascular structures, with the notable exception of Staphylococcus aureus, which has a predilection to settle on both normal and damaged tissues. Consequently, every patient developing a bloodstream infection with S. aureus is at risk for endocarditis and other metastatic infections, although the likelihood varies with the source and circumstances. In line with current recommendations, transesophageal echocardiography (TEE) is performed routinely where available, in patients with catheter-associated S. aureus bacteremia to help determine the length of antibiotic therapy.1Mermel L.A. Allon M. Bouza E. et al.Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 update by the Infectious Diseases Society of America.Clin Infect Dis. 2009; 49: 1-45Crossref PubMed Scopus (2271) Google Scholar However, too often our unflinching fascination with cutting-edge technologies has led to unconditional (rather than carefully qualified) endorsements for sophisticated diagnostic testing in already well-managed conditions.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar Past experience and clinical acumen are cast aside impulsively in the rush. Now coming almost full circle, recent analyses have persuasively challenged the reflexive use of TEE in all patients with catheter-associated S. aureus bacteremia.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google Scholar Proponents of TEE in this context contend that clinical assessment alone is inadequate to differentiate patients with endocarditis from those with uncomplicated bacteremia, even in the absence of predisposing conditions.1Mermel L.A. Allon M. Bouza E. et al.Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 update by the Infectious Diseases Society of America.Clin Infect Dis. 2009; 49: 1-45Crossref PubMed Scopus (2271) Google Scholar, 5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar, 6Rasmussen R.V. Høst U. Arpi M. et al.Prevalence of infective endocarditis in patients with Staphylococcus aureus bacteraemia: the value of screening with echocardiography.Eur J Echocardiogr. 2011; 12: 414-420Crossref PubMed Scopus (109) Google Scholar This observation conflicts with much of the pre-TEE literature and substantial anecdotal experience before echocardiography.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Nonetheless, compelling data from TEE indicate that we had been missing subclinical cases of endocarditis.5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar How do we resolve this unnerving paradox? Endocarditis can be a potentially life-threatening (albeit infrequent) consequence of line-related S. aureus bacteremia. Long-term treatment had become the standard of care for established valvular infection long before modern imaging modalities were ever anticipated. However, in the absence of cellulitis or thrombophlebitis at the former catheter insertion site or evidence of active infection elsewhere, treatment of line-related bacteremia for more than a few days after line removal is intended to preemptively eradicate possible occult foci of staphylococcal infection. TEE apparently has uncovered heretofore undetectable valvular seeding that may otherwise have never become manifest if appropriate interventions were initiated soon after the onset of catheter-derived bacteremia. Before TEE, carefully selected patients with line-related S. aureus bacteremia (including some who would have had positive TEEs if available) were treated successfully with prompt removal of the inciting focus, followed by 10-14 days of antibiotics.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Candidates for short-course therapy included patients without valvular disease in whom the catheter was quickly pulled, the bacteremia persisted <48 hours thereafter, the clinical response was rapid and complete, no hardware remained, and signs of metastatic infection never supervened during therapy.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar TEE has operationally redefined endocarditis.5Fowler V.G. Li J. Corey G.R. et al.Role of echocardiography in evaluation of patients with Staphylococcus aureus bacteremia: experience in 103 patients.J Am Coll Cardiol. 1997; 30: 1072-1078Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar Do prior algorithms mandating ≥4 weeks of antibiotics de facto apply to early cases formerly undiagnosable in real time? Incipient S. aureus endocarditis identifiable exclusively by TEE might be eradicated with shorter courses,2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar analogously to β-lactam monotherapy for tricuspid endocarditis without apparent left-sided involvement.9Ribera E. Gomez-Jimenez J. Cortes E. et al.Effectiveness of cloxacillin with and without gentamicin in short-term therapy for right-sided Staphylococcus aureus endocarditis A randomized, controlled trial.Ann Intern Med. 1996; 125: 969-974Crossref PubMed Scopus (161) Google Scholar Although subclinical endocarditis must have complicated seemingly uncomplicated S. aureus bacteremia in the pre-TEE era, 2 weeks of antibiotics were reliably curative.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar Low-risk patients fully and unequivocally responding to catheter removal plus/minus a few days of antibiotics should still be curable with a 2-week course, irrespective of whether TEE can visualize a silent vegetation.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, 9Ribera E. Gomez-Jimenez J. Cortes E. et al.Effectiveness of cloxacillin with and without gentamicin in short-term therapy for right-sided Staphylococcus aureus endocarditis A randomized, controlled trial.Ann Intern Med. 1996; 125: 969-974Crossref PubMed Scopus (161) Google Scholar, 10Bendig E.A. Singh J. Butler T.J. Arrieta A.C. The impact of the central venous catheter on the diagnosis of infectious endocarditis using Duke criteria in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 636-639Crossref PubMed Scopus (15) Google Scholar, 11Pigrau C. Rodríguez D. Planes A.M. et al.Management of catheter-related Staphylococcus aureus bacteremia: when may sonographic study be unnecessary?.Eur J Clin Microbiol Infect Dis. 2003; 22: 713-719Crossref PubMed Scopus (41) Google Scholar, 12Ross A.C. Toltzis P. O'Riordan M.A. et al.Frequency and risk factors for deep focus of infection in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 396-399Crossref PubMed Scopus (16) Google Scholar The incremental risk:benefit ratio of several additional weeks of intravenous antibiotic administration has not been established for these patients. In addition to the occasional complication from an invasive procedure, indiscriminate TEE might paradoxically be injurious when therapy is unnecessarily prolonged. Appropriate shortening of antibiotic courses can reduce iatrogenic complications, ironically decreasing the risk of recurrent line-related septicemia. Thus, TEE may be postponed indefinitely in stable low-risk patients with S. aureus bacteremia who quickly become asymptomatic upon catheter removal and never exhibit any signs of metastatic infection for complementary reasons. Firstly, the low pretest probability of endocarditis in this subgroup makes costly procedures unlikely to yield true positive findings.3Kaasch A.J. Fowler V.G. Rieg S. et al.Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia.Clin Infect Dis. 2011; 53: 1-9Crossref PubMed Scopus (100) Google Scholar, 4Soriano A. Mensa J. Is transesopheageal echocardiography dispensable in hospital-acquired Staphylococcus aureus bacteremia?.Clin Infect Dis. 2011; 53: 10-12Crossref PubMed Scopus (5) Google Scholar, 11Pigrau C. Rodríguez D. Planes A.M. et al.Management of catheter-related Staphylococcus aureus bacteremia: when may sonographic study be unnecessary?.Eur J Clin Microbiol Infect Dis. 2003; 22: 713-719Crossref PubMed Scopus (41) Google Scholar, 12Ross A.C. Toltzis P. O'Riordan M.A. et al.Frequency and risk factors for deep focus of infection in children with Staphylococcus aureus bacteremia.Pediatr Infect Dis J. 2008; 27: 396-399Crossref PubMed Scopus (16) Google Scholar Secondly, even when the TEE is positive in isolation, duration of therapy need not automatically be extended.2DiNubile M.J. Skepticism: a lost clinical art.Clin Infect Dis. 2000; 31: 513-518Crossref PubMed Scopus (7) Google Scholar, 7Raad I.I. Sabbagh M.F. Optimal duration of therapy of catheter-related Staphylococcus aureus bacteremia: a study of 55 cases and review.Clin Infect Dis. 1992; 14: 75-82Crossref PubMed Scopus (208) Google Scholar, 8Walker T.M. Bowler I.C. Bejon P. Risk factors for recurrence after Staphylococcus aureus bacteraemia A retrospective matched case-control study.J Infect. 2009; 58: 411-416Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar However, the patient must be interviewed and examined daily for subtle or transient signs of endocarditis or other metastatic infection, and the final decision to administer only 2 weeks of antibiotics not made until the 14th day of therapy. If the patient's status changes, a TEE can always be performed at that time and the course of treatment adjusted accordingly.