Physician Management of Staphylococcus aureus Bacteremia

Staphylococcus aureus is the leading cause of community and health care-associated bacteremia, with an annual incidence of 38.2 to 45.7 per 100,000 person-years in the United States. Staphylococcus aureus bacteremia (SAB) has a 30-day mortality rate of 20% and health care costs per case can range from $37,868 to $67,439. Given the high prevalence and treatment costs of SAB, treatment becomes increasingly a topic of concern.

The involvement of infectious disease physicians in the treatment of patients with SAB has long been associated with significant improvements in patient outcomes and ensuring medical management follows best practice. In a new study, investigators set out to assess prescribing practices for the management of SAB and how diagnostic evaluation and medical management of adult patients varied.

The investigators utilized the Emerging Infections Network (EIN) to survey and assess how physicians treat SAB patients.

EIN is a network of infectious disease physicians within the Infectious Disease Society of America (IDSA) and is funded by the US Centers for Disease Control and Prevention. Surveying EIN physicians, investigators asked 11 questions regarding the physicians’ opinions and patterns for treating patients with SAB.

A total of 723 EIN physicians responded and participated in the survey (56% of the EIN network). Demographic information indicated that respondents were more likely than non-respondents to have 25 years or more experience. An overwhelming majority of respondents stated that repeated blood cultures and an echocardiogram were a part of their management, and those with less than 15 years of experience were more likely to always do a transthoracic echocardiogram (TTE). Interestingly, those physicians practicing in the Midwest, Northeast, or Southern regions were more likely to perform a transesophageal echocardiogram (TEE) than those in the West or Canada/Puerto Rico. Additionally, 19% of the respondents also stated that they would order a TEE on those patients with a negative TTE.

For patients with left-sided methicillin-sensitive Staphylococcus aureus (MSSA) endocarditis, 32% of the physicians opted to treat with cefazolin, 29% chose nafcillin, and 32% considered both options to be equivalent. Moreover, those with less than 5 years of experience were more likely to use cefazolin while those with more than 15 years of experience were more likely to use nafcillin.

The majority of physicians who chose cefazolin cited a combination of equal efficacy, less toxicity, dosing convenience, and cost as reasons for their preference.

Regarding duration of treatment, the majority of respondents stated that for patients with SAB, IV antibiotics were usually needed for 14 days.

For patients with MRSA (methicillin-resistant Staphylococcus aureus) and a skin and soft tissue source, rapid clearance of blood cultures, negative TTE, and no evidence of metastatic infection, the majority of surveyed physicians would prescribe IV vancomycin for 14 days, while 13% would transition to oral antibiotics to complete the 14-day course. Only 4% of physicians indicated they would treat for 5-7 days with either oral or IV antibiotics.

If 1 of a patient’s 2 blood cultures grew MSSA and they had no obvious sign or symptom of infection, a normal white blood cell count, negative repeat blood cultures, a negative TTE, and no evidence of metastatic infection, most physicians would treat with IV antibiotics for 14 days and 8% would treat for 4-6 weeks. Only 10% of physicians indicated they would consider the cultures a contaminant and would then stop antibiotics. For patients with septic thrombophlebitis, 71% of providers recommended anticoagulation after the catheter had been removed, while the duration of antimicrobial therapy varied between 2, 4, and 6 weeks.

Overall, for patients with SAB, the majority of respondent infectious disease physicians opted to repeat blood cultures, order an echocardiography, and treat with IV therapy for at least 14 days. However, IDSA treatment guidelines for MRSA recommend echocardiography in all patients with SAB, and a TEE is also preferred. This is particularly interesting as only 19% of respondents indicated that they would always perform a TEE.

The investigators noted a lack of consensus regarding treatment of MSSA endocarditis. They suggested that this is likely due to an increasing presence of literature suggesting clinical outcomes and fewer adverse events related to the medications.

Clinical response did influence over half of respondents as to whether they would continue vancomycin in a patient with MRSA bacteremia.

Small nuances like this were found throughout the study and give insight into the variances among infectious disease physicians and how they manage SAB in patients.

Ultimately, these findings suggest that further efforts should be made to provide more guidance on best practice and how to standardize medical management of SAB.