P-813. Lactobacillus Bacteremia and Endovascular Infections: A Retrospective Case Series of 333 Patients
Authors: Radcliffe Christopher , Anahtar Melis N , Hohmann Elizabeth , Turbett Sarah , Dugdale Caitlin , Paras Molly 
Published: January 2025

Abstract

Background
Despite being normal flora, and sometimes considered a contaminant, there are reports of Lactobacillus endovascular infections. However, large case series are lacking. We evaluated patient characteristics, antimicrobial susceptibility testing (AST), and all-cause mortality among patients with Lactobacillus bacteremia and/or endovascular infections managed in the Mass General Brigham (MGB) healthcare system.Table 1.Patient Characteristics for Lactobacillus Bacteremia and Endovascular Infections* Immunocompromised based on one or more of the following diagnoses:a. Human immunodeficiency virus with CD4 &lt;200b. Active lymphoma or leukemia (including indolent chronic lymphocytic leukemia)c. Metastatic cancerd. Cytotoxic chemotherapy within the prior 3 monthse. Radiation therapy within prior 3 monthsf. Congenital immunodeficiencyg. Aplastic anemiah. Solid organ transplant recipients on immunosuppressive therapyi. Hematopoietic stem cell transplant recipients, unless &gt;2 years post-transplant and no longer on any immunosuppressive therapyj. Immunocompromised based on &gt;1 of the following medications: glucocorticoid therapy equivalent to prednisone &gt;20 mg/d for &gt;2 weeks, or if such therapy has been discontinued within the past month; alkylating agents within the past 3 months; antimetabolites (methotrexate &gt;0.4 mg/kg/week, azathioprine &gt;3 mg/kg/day, 6-mercaptopurine &gt;1.5 mg/kg/day) within the past 3 months; cyclosporine, tacrolimus, sirolimus, everolimus, or mycophenolate mofetil within the past 3 months; biologic immunosuppressants and immunomodulators within the past 3 months (6 months for lymphocyte-depleting agents)

Methods
The MGB Research Patient Data Registry and Massachusetts General Hospital microbiology database were queried to identify adults with blood, central line, or endovascular device culture(s) positive for Lactobacillus obtained at in-network hospitals between 1/1/00 and 9/1/22. Patient demographics, comorbidities, antibiotic regimens, 90- and 365-day all-cause mortality, and AST data for Lactobacillus isolates were extracted from charts when available. When echocardiography was available, potential endocarditis was classified according to the 2000 Duke criteria. Summary statistics were performed.Table 2.Treatment Strategies and Outcomes for Lactobacillus Bacteremia and Endovascular Infections*Number of cases reported to have completed intended therapy does not include cases for which no anti-Lactobacillus therapy was administered

Results
We identified 333 patients with Lactobacillus bacteremia and/or endovascular infections. The mean age was 56 years, 42% (140/333) were female, and 36% (120/333) were immunocompromised (Table 1). Possible or definite endocarditis was identified in 19% (64/333), and 36% (121/333) had ≥1 additional organism(s) isolated in culture(s) growing Lactobacillus. The most common intended treatment duration was 1-2 weeks (91/209; 44%). Overall, 59/333 (18%) patients did not receive antibiotics active against Lactobacillus (Table 2). For patients with data available, all-cause mortality was 27% (85/316) at 90 days and 43% (130/301) at 365 days. For isolates with AST data, susceptibility to penicillin, ampicillin, and linezolid was reported for 96% (82/85), 99% (76/77), and 100% (66/66), respectively. Most isolates were resistant to meropenem (40/49; 82%) (Table 3).Table 3.Antimicrobial Susceptibility Data for Unique Lactobacillus Isolates
n reflects number of unique Lactobacillus isolates that were tested against each antimicrobial

Conclusion
Among 333 patients with Lactobacillus bacteremia and/or endovascular infections, 1-year all-cause mortality was high. When Lactobacillus is isolated in blood cultures, clinicians should consider its relevance to the clinical scenario before labeling the organism as a contaminant.

Disclosures
Melis N. Anahtar, MD, PhD, Day Zero Diagnostics: Advisor/Consultant|Day Zero Diagnostics: Ownership Interest Elizabeth Hohmann, MD, Astra Zeneca: Grant/Research Support|Laguna Biotherapeutics: Grant/Research Support|MicrobiomeX/Tend: Grant/Research Support Sarah Turbett, MD, UpToDate: Author