Per IDSA guidelines, uncomplicated SAB (no implanted prosthesis, negative blood cultures within two to four days, defervescence within 72 hours of initiating therapy, and lack of metastatic complication) can be treated with a two-week course of antibiotics, while complicated bacteremia (any of above criteria) should be treated within four to six weeks.3
Monitoring for Complications: Echos
Based on the IDSA guidelines, echocardiography is recommended in all patients with bacteremia, with a preference of transesophageal echocardiography (TEE) over transthoracic echocardiography (TTE).3 More recently, Kaasch et al developed simple criteria to identify patients with nosocomial SAB at low risk for infective endocarditis based on two prospective cohort studies.23 Lack of any of these criteria, which include prolonged bacteremia of more than four days’ duration, presence of a permanent intracardiac device, hemodialysis dependency, spinal infection and nonvertebral osteomyelitis, along with a negative TTE indicates that a TEE is not necessary (see Table 3). However, these patients need close follow-up to ensure that bacteremia clears and no new signs or symptoms concerning for metastatic infection develop.
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Table 3. Clinical prediction criteria associated with increased risk of infective endocarditis in patients with SAB
ID Consultation
Several studies have shown that ID consultation not only improves adherence to evidence-based management of SAB, but it also reduces mortality.24-27 In a recent prospective cohort study in a tertiary-care center, even after adjusting for pre-existing comorbidities and severity of disease, an ID consult was associated with a 56% reduction in 28-day mortality.24 The patients who were followed by an ID consult service were more likely to receive appropriate duration of antibiotics (81% vs. 29%, respectively) and undergo appropriate workup for the evaluation of metastatic infections (34% and 8%, respectively). This study concluded that routine ID consult should be considered in patients with SAB, especially those with severe illness and multiple comorbid conditions.
Back to the Case
The patient was started on empiric therapy with vancomycin and serial blood cultures were obtained. He remained hemodynamically stable but febrile, with persistently positive blood and urine cultures. Given concern for the port being the source of his infection, his chest port was removed. A high-quality TTE was performed and was unremarkable.
ID was consulted. Blood cultures subsequently grew MSSA and vancomycin was switched to cefazolin 2g every eight hours. On hospital Day 5, his fever resolved and blood cultures turned negative. There were no clinical signs or symptoms for metastatic infections. A PICC line was placed after blood cultures remained negative for 48 hours. The decision was made to treat him with four weeks of antibiotics from his last positive blood culture, with follow-up in ID clinic.
Bottom Line
SAB is a common worldwide cause of morbidity and mortality. Treatment should include removing the nidus if present, finding and administering the appropriate antimicrobial therapy, evaluating for possible complications, and consulting with ID.
Dr. Ward is an assistant professor, Dr. Kim a clinical instructor, and Dr. Stojan a clinical lecturer at the University of Michigan Health System in Ann Arbor.