Partial Oral Antimicrobials to Treat Infective Endocarditis in People Who Inject Drugs

This is a randomized open-label study. Participants will be randomized 1:1 in blocks of 5 to either continued intravenous antimicrobial therapy or oral antimicrobial therapy after a minimum of 10 days of IV therapy. The antimicrobial choice will be based on antimicrobial susceptibility. All oral regimens for gram-positive organisms will include 2 different agents. Gram-negative pathogens will be treated with oral quinolones if susceptibility results are compatible. Decisions regarding ongoing inpatient or outpatient therapy will be made at the discretion of the attending physician. Outpatient follow up will be once weekly for 6 weeks and then at 3 months. At each follow-up visit, participants will undergo a general physical exam, and their adherence to therapy and general wellbeing will be assessed as well. Blood samples will be sent for a complete blood count, creatinine, C-reactive protein by the investigators to ensure continued improvement in response to therapy. Within 72 hours of stopping therapy, a transthoracic echocardiogram will be performed to determine response to therapy and to establish a new baseline to which subsequent echocardiograms if medically indicated would be compared to assess for relapse or development of a new IE. All lab tests are done at our affiliated hospitals. Investigators plan first on performing a feasibility study. In the feasibility study, investigators recruit a total of 50 patients and randomize 25 in each arm. Baseline characteristics, of clinical interest with a potential impact on prognosis, and patients' outcomes will be compared using the Chi-square test for categorical variables and the t-test and the Mann-Whitney test for continuous variables, when appropriate. To examine the association between oral antimicrobial therapy and 90-day mortality, investigators plan to perform a multivariable logistic regression analysis with oral therapy being the independent variable. The model will also include variables of clinical interest: diabetes, renal impairment, immune-compromising condition, age \> 50, and evidence of embolization.