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Abstract Background Outpatient parenteral antimicrobial therapy (OPAT) practice has continued to increase. We sought to understand current OPAT practices in a survey of U. S. clinicians.Figure 1Respondents rated their agreement with the following statement: “The OPAT program at my hospital receives adequate support in the following areas”Figure 2Factors present in providing safe OPAT services on a scale where 1 is “extremely challenging” and 5 is “not challenging at all” Methods A survey instrument was developed by ID physicians, pharmacists and Infectious Diseases Society of America (IDSA) Emerging Infections Network (EIN) staff, utilizing prior EIN OPAT surveys. The survey focused on respondents’ role, responsibilities, time devoted to OPAT, structure of OPAT provision, location where OPAT is received, institutional support and oversight, role of complex outpatient antimicrobial therapy (COpAT) including oral antimicrobials and long-acting injectable agents, and barriers to safe OPAT care. The confidential survey was distributed to adult EIN members from Feb to March 2025. Results Overall, 622 (38%) EIN members responded to the survey, of whom 469 with a role in managing OPAT patients were eligible to complete the survey. OPAT teams varied across programs with nearly all involving ID physicians (98%), majority involving ID/OPAT pharmacists (61%), nurses (60%), and nearly half involving administrative staff (48%) and advanced practice providers (APPs, 47%). ID consultation for OPAT enrollment was required in 60% of programs. Many programs (59%) report including COpAT. Response to outpatient lab results was largely managed by ID physicians (75%); however, multidisciplinary OPAT teams (37%), pharmacists (33%), and inpatient ID physicians (30%) were also frequently involved. Lab values were most often available via fax/email (43%) or electronic health record (EHR, 41%). Nearly 25% of programs “often/always” required proactive outreach to obtain safety labs. Overall, many programs lacked data analysis, administrative, information technology, and financial support (Figure 1). Challenges faced by OPAT programs included lack of leadership awareness of the value of OPAT (51%), difficulty managing patients with substance use disorder (50%), access to timely lab values (48%), personnel to retrieve missing lab values (46%), and struggles with the EHR (43%) (Figure 2). Conclusion Compared to EIN OPAT surveys in 2013 and 2019, programs have grown in size and composition, and expanded to COpAT. Similar problems persist regarding perceived lack of support. Disclosures Monica V. Mahoney, PharmD, BCPS, BCIDP, FCCP, FIDSA, FIDP, FMSHP, gsk: Advisor/Consultant|seqirus: Advisor/Consultant Philip M. Polgreen, MD, Eli Lily: Advisor/Consultant|Pfizer: Grant/Research Support Sara C. Keller, MD, MPH, MSPH, CorMedix: Grant/Research Support

Abstract Background Within the Coccidioides-endemic area, coccidioidomycosis (cocci) has been identified as the cause of pneumonia in 15-29% of patients with community-acquired pneumonia (CAP). Although efforts to improve testing CAP patients for cocci are underway in the outpatient settings in Arizona, we do not know whether testing is common among patients admitted to the hospital with pneumonia. We undertook the current study to assess the frequency of testing for cocci among hospitalized patients with pneumonia in our institution, and to understand whether positive serologic testing led to a reduction in antibiotic use. Methods We commissioned the creation of an electronic tool by our Information Technology colleagues to create a report to identify inpatients of Mayo Clinic Hospital with a pneumonia diagnosis (J18.0 – J18.9) and information regarding testing for Coccidioides by any serology (enzyme immunoassay, immunodiffusion or complement fixation) and patient receipt of antibiotics or antifungal treatment (name, inclusive dates). Results Between January 1, 2024 and December 31, 2024, 1162 patients were admitted to the Hospital Internal Medicine service at Mayo Clinic Hospital, Phoenix AZ with a pneumonia diagnosis. Among these, 771 (66%) were tested serologically for coccidioidomycosis, and 87/771 (11%) were found to be positive. By calendar month, the percent of patients tested ranged 59 – 73%, and percent test positivity ranged 3% (March) - 19% (December). The mean time from admission to test order was 0.5 days (range 0 – 6 days) and mean time from admission to positive result was 3.0 days (range 0.4 – 12.0 days). However, among seropositive patients, the duration of antibiotics was 4.2 days, not different when compared with patients who were either seronegative or not tested, (4.1 days, p=NS). 173 (14.9%) received antifungal treatment during hospitalization, among whom 55 (31.2%) had positive coccidioidal serology and 118 (68.2%) did not. Conclusion Coccidioidomycosis is an important cause of pneumonia within the inpatient setting. However, one third of patients were not tested, representing an opportunity to understand and overcome barriers to testing. Positive tests were not associated with a reduction of antibiotic use. Disclosures All Authors: No reported disclosures

Abstract Background Detecting Histoplasma (HP) and Blastomyces (BM) antigen (Ag) in urine (U) and serum (S) is an essential diagnostic tool for these pathogens. Labs have added bronchoalveolar lavage (BAL) and cerebrospinal fluid (CSF) as additional HP and BM Ag testing sources. We evaluated the sensitivity of Ag detection in U and S in patients with detected HP or BM Ag in BAL or CSF by enzyme immunoassay (EIA). Methods 14 patients with HP or BM Ag-positive results made up the CSF cohort. The Ag concentrations were below the limit of quantification (< LoQ, N=3), above the limit of quantification ( > LoQ, N=1), and 0.3 to 9.5 ng/mL (x̄ = 2.3 ng/mL, N=10). The BM Ag-positive in BAL group included 24 patients, with concentrations of < LoQ (N=4), >LoQ (N=5), and 0.3 to 11.3 ng/mL (x̄ = 3.5 ng/mL, N=15). HP Ag-positive in BAL comprised 36 patients, with 3 < LoQ, 10 >LoQ, and 23 ranging from 0.8 to 16.9 ng/mL (x̄ = 4.7 ng/mL). 16 patients in the BAL cohorts were Ag-positive for HP and BM, demonstrating the inability to discriminate between these dimorphic fungi through Ag testing. All patients were checked for routine clinical HP and BM EIA Ag test results on U and S. HP BAL patients were also investigated for cross-reacting galactomannan (GM; Aspergillus EIA in S or BAL) and (1→3)-β-d-glucan (BDG; Fungitell EIA in S) antigen test orders. All additional test results over 14 days before or after CSF or BAL Ag testing were excluded. Results 100% (14/14), 96% (22/23), and 83% (30/36) of HP/BM CSF, BM BAL, and HP BAL Ag-positive patients were also positive in U and/or S, when both additional sources were ordered, respectively. Of the 6 HP BAL patients without positive U or S results, 3 had GM and BDG testing performed. All 3 had high signal GM and/or BDG results in S and/or BAL. In conjunction with low HP Ag levels in BAL (1.0 to 1.53), these findings suggest cross-reactivity in the HP BAL Ag test. Classifying these 3 patients as HP BAL false-positive shows a positive agreement of 91% (30/33) between HP BAL and HP U/S. Conclusion HP and BM CSF Ag testing showed no increase in sensitivity when U and S were tested. Minimal increases in sensitivity were observed in HP and BM BAL versus U and S. However, false-positive results in BAL due to cross-reactivity with GM and BDG cannot be ruled out, suggesting limited utility of the invasive CSF and BAL sources for HP and BM EIA Ag testing. Disclosures All Authors: No reported disclosures

Abstract Background Leishmaniasis is a rare protozoan parasitic disease transmitted through the bite of infected Phlebotomus and Lutzomyia sandflies. Clinical presentation is variable due to numerous species and host immunity differences. We present our clinical experiences with CL to guide timely diagnosis and treatment in returning travelers. Methods We retrospectively analyzed a cohort of adult patients 18+ years old who were diagnosed with CL from 2005 and 2025. We describe the demographic, clinical, and diagnostic features of CL. Results Biopsy-confirmed CL was diagnosed in 20 returning travelers (Table 1) from various endemic regions, most commonly Costa Rica (Fig. 1). The median time from travel to symptom onset was 36.5 days (SD 102), with an additional 75.5 days (SD 87) prior to biopsy diagnosis. All patients were evaluated by dermatology and 70% were evaluated by infectious disease (n=14). On initial presentation, lesions were described as ulcerated (50%, n=10), nodular (30%, n=6), painful (20%, n=4), and necrotic (10%, n=2; Fig. 2). Most lesions were located on the upper extremity (55%, n=11), followed by the face (35%, n=7), lower extremity (30%, n=6), and trunk (15%, n=3). 15% of individuals (n=3) had constitutional symptoms. No patients had definitive mucosal involvement, however, 10% (n=2) endorsed lip edema. No patients had visceral involvement. Species level identification occurred in 14 cases (70%), of which the most common was L.V. panamensis (50%), L.L. mexicana (21%), L. V. guyanensis (14%), L. L. tropica (7%), and L. V. braziliensis (7%). Initial treatments included azoles, liposomal amphotericin B (AmBisome), and miltefosine (each 20%); cryotherapy and parenteral pentamidine (each 10%); with compounded topical paromomycin added in 15% of cases. 35% of individuals (n=7) failed initial treatment and required additional treatment courses due to persistent lesions (57%) or relapse following initial resolution (14%). 10% (n=2) required a third treatment course due to persistent/recurrent lesions. Conclusion While CL in travelers has a variety of clinical manifestations, travel history, knowledge of key clinical features, and lesion patterns can aid in early diagnosis and treatment. CL is associated with early treatment failure rate for uncertain reasons. Disclosures All Authors: No reported disclosures

Abstract Background Pathogenesis of Scrub typhus (ST), a tick-borne acute zoonotic disease caused by the bacterium Orientia tsutsugamushi, involves infection of vascular endothelial cells, triggering a potent cytokine host response that causes organ damage. Methods Prospective study in a tertiary care hospital in North-west India in 30 cases of Scrub typhus. Measurements of cytokines IL-17A, INF-γ, TNF-α, IL-10, IL-6, IL-4, and IL-2 were carried out at admission in all 30 patients and a control group of 10 healthy persons using BDTM Cytometric Bead Array, BD Biosciences, San Diego, California, USA. Results Mean age of the entire cohort was 36 years, and the male-female ratio was 2:1. The most common symptoms were dyspnea 87%, altered sensorium 23%, abdominal pain 20%, decreased urine output 10% and myalgia in 10%. On clinical examination, eschar was present in 40%. Investigations revealed anemia in 80% cases, leukocytosis in 46.6%, thrombocytopenia in 90%, jaundice in 53.3% and elevated serum transaminase levels in 84% cases. Of all complications, acute respiratory distress syndrome occurred in 90% patients, acute kidney injury in 37% patients, acute meningoencephalitis syndrome in 30%, and myocarditis in 23%. The mean APACHE 2 score of the entire cohort was 12 . Multi-organ dysfunction syndrome (MODS) was seen in 67% of cases, and the overall mortality rate was 20%. On Fisher's Exact Correlation analysis, presentation with meningoencephalitis, myocarditis, systemic acidosis, and a high APACHE 2 score correlated with mortality. The serum levels of cytokines were elevated in all patients compared to the healthy control group (Table 1), but did not significantly differ between survivors and non-survivors. Furthermore, the elevated levels of TNF-α (p=0.004) and IL-10 (p=0.029) strongly correlated with multi-organ dysfunction syndrome (MODS). Conclusion In Scrub Typhus, the strong correlation of serum levels of TNF-α and IL-10 with multi-organ dysfunction syndrome (MODS) suggests their involvement in disease progression. The high prevalence of acute respiratory distress syndrome and MODS, alongside a mortality rate of 20%, highlights the critical nature of scrub typhus and the necessity for early recognition of complicated disease and intervention. Disclosures All Authors: No reported disclosures

Abstract Background Good syndrome (GS) is an under-recognized adult-onset immunodeficiency characterized by the coexistence of thymoma and hypogammaglobulinemia. It is marked by recurrent infections, combined B- and T-cell immunodeficiency, and frequent autoimmune manifestations. Its rarity, unclear pathogenesis, and often delayed diagnosis contribute to its clinical complexity.Distribution of Infections by pathogen type in patients with Good Syndrome: the microbiological spectrumDemographics, clinical characteristics, thymoma classification with staging and management Methods We conducted a retrospective review of adults diagnosed with good syndrome at Mayo Clinic up until 2024. We assessed baseline characteristics, clinical features with a particular focus on infectious complications, immunological lab parameters, thymoma histopathology with staging, and management. Descriptive statistics were utilized for analysis.Immunological lab parameters and management of Good syndrome Results During the study period, Good syndrome was diagnosed in 32 patients; 78% were male, with a median age at diagnosis of 62 years (Table 1). All patients had thymoma, the majority of which were stage I (localized), and most underwent thymectomy as part of management. The median delay in GS diagnosis following thymoma diagnosis was 1,486 days (interquartile range IQR: 406.75–1,992.75). Infectious complications were observed in 30 of 32 patients (97%), most commonly sinopulmonary infections (87%) (Figure 1). Bacterial infections were documented in 29 patients (94%), viral in 14 (45%), fungal in 13 (42%), and mycobacterial in 3 (10%) (Figure 2). Immunologic data were available for 22 patients. Reduced CD4+ T-cell counts and severe B-cell lymphopenia were observed in 77%. IgM and IgG deficiencies were the most prevalent, present in 82% of cases. Most patients received monthly immunoglobulin replacement; additionally, 59% were prescribed oral antimicrobial prophylaxis due to their elevated risk of infections. All-cause mortality was 31% (n=10); among these, 3 deaths (10%) were directly attributable to complications of Good syndrome. Conclusion We observed a significant delay (Median of 4.07 years) in the diagnosis of Good syndrome following thymoma detection. Given the high risk of infectious complications and associated mortality, clinicians should maintain a high index of suspicion and consider early immunologic evaluation in adults with recurrent or opportunistic infections, particularly in the context of a known thymoma. Disclosures All Authors: No reported disclosures

Abstract Background Revaccination is required for patients who receive a hematopoietic cell transplant (HCT) to reduce vaccine preventable illness. Revaccination requires an individualized plan due to differences in immunosuppressive therapy, immune reconstitution, age, and other challenges such as graft versus host disease. A structured approach is required to ensure prompt initiation of re-vaccinations and completion of the re-vaccination schedule. This study sought to evaluate the re-vaccination process at our center as a baseline for quality improvement. Methods We conducted a retrospective chart review of pediatric patients who received an autologous or allogeneic HCT between January 2019 and March 2024 to assess time to starting re-vaccination after post-HCT medical clearance and percentage of patients up to date within each series of vaccinations per internal protocol. Results A total of 64 patients were evaluated, of whom 23 were female and 35 underwent allogeneic stem cell transplant. For analysis, 13 were excluded due to death prior to clearance for vaccination. Among those included, 42 patients were cleared for restarting vaccines, and 37 (88%) of those have received at least one vaccine, while only 25 (59%) have completed the first series of recommended vaccines. The average time from transplant to administration of the first vaccine was 431 days for autologous HCT and 459 days for allogeneic HCT. The average time from medical clearance to the first vaccine was 66 days. The mean interval between the first and second vaccine doses was 97 days. Conclusion The majority of eligible patients initiated re-vaccination after transplant, but rates for the receipt of full recommended initial series remained suboptimal, with notable delays with notable delays between transplant and the day of clearance as well as clearance and the first vaccine administered. These findings highlight significant gaps in post-transplant immunization practices and underscore the need for targeted interventions to optimize protection for this vulnerable population. Disclosures All Authors: No reported disclosures

Abstract Background Phage therapy has emerged as a generally safe approach, as demonstrated in preclinical and clinical studies. However, data on efficacy, including optimal dosing frequency, remain limited. MRSE is a leading cause of foreign body-associated osteomyelitis and a potential target for phage therapy. Here, the activity of phage K alone and in combination with vancomycin (VAN), administered once (QD) or three times (TID) daily, against biofilms formed by two orthopedic infection-associated MRSE isolates on orthopedic screws was evaluated.Fig 1.in vitro multi-dose assay of methicillin-resistant S. epidermidis biofilm-coated cortical bone screws.IDRL, Infectious Diseases Research Laboratory; DMEM, Dulbecco's Modified Eagle Medium; PBS, phosphate-buffered saline; CFU, colony-forming units. Created in https://BioRender.comFig 2.Quantities of biofilm on screws after 24 hours of treatment.*Log10 CFU/cm² of biofilm on screws before treatments. Biofilm burden of the MRSE isolates prior to treatment ranged from 5.7 to 6.3 log10 CFU/cm². A Kruskal-Wallis test was performed to evaluate the statistical significance of biofilm reduction between treatment groups. The minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm bactericidal concentration (MBBC) of vancomycin for both IDRL-9410 and IDRL-9403 were 2, 2, and >128 µg/mL, respectively. Methods MRSE IDRL-9410 and IDRL-9403 biofilms were formed on titanium cortical bone screws (D 1.5 mm, L 4 mm, surface area 0.33 cm²) in 0.2 mL of tryptic soy broth containing 10⁶ CFU/mL (Fig 1); testing was performed in triplicate on two separate days. After 24 hours, screws were rinsed with PBS and randomly assigned to: Dulbecco’s Modified Eagle Medium (DMEM); vancomycin (VAN, 20 μg/mL) in DMEM; phage K (10⁹ PFU/mL) in DMEM; or VAN and phage K in DMEM. Every 8 hours, screws from the TID groups were transferred to new plates containing fresh treatment, with QD groups left in the original material. 24 hours post-treatment, screws were quantitatively cultured. Bactericidal activity was defined as ≥ 3 log₁₀ CFU/cm² reduction compared to the DMEM group, and synergy as ≥ 2 log₁₀ CFU/cm² reduction in the combination group compared to VAN or phage alone. Results After 24 hours, bactericidal activity was observed for QD and TID VAN-phage K groups against IDRL-9410 (p < 0.05 and p < 0.01, respectively) and IDRL-9403 (both p < 0.01). Synergy was observed in the VAN-phage K QD group, with a 2.2 log₁₀ CFU/cm² reduction for IDRL-9410 compared to VAN alone (Fig 2). 3.0 and 5.3 log₁₀ CFU/cm² reductions were observed in the VAN TID groups for IDRL-9410 and IDRL-9403, respectively, compared to the DMEM group (both p < 0.01). There was no statistically significant difference in biofilm reduction between the QD and TID groups for phage K alone or VAN-phage K for either strain. Conclusion Combination treatment with phage K and VAN, administered QD or TID, showed greater biofilm reduction compared to phage K alone. Increasing phage dosing frequency did not enhance biofilm reduction under the conditions studied. Disclosures Robin Patel, MD, a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication, a patent on PET imaging of bacterial infection: a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication, a patent on PET imaging of bacterial infection|MicuRx Pharmaceuticals and bioMérieux: Grant/Research Support|PhAST, Day Zero Diagnostics, DEEPULL DIAGNOSTICS, S.L., Nostics, HealthTrackRx, bioMérieux and CARB-X: Advisor/Consultant|Up-to-Date and the Infectious Diseases Board Review Course: Honoraria

Abstract Background Stigma associated with tuberculosis (TB) and TB diagnosis is a major social factor in delay of diagnosis and non-adherence to TB treatment among Asian American and Pacific Islander (AAPI) populations. Main sources of stigma include misconceptions regarding TB transmission and lack of knowledge about symptoms or treatment.Figure 1.Respondent demographicsBreakdown of respondent demographics by age, gender, and AAPI subgroup.Figure 2.Demographic breakdown of TB awarenessTB awareness by AAPI subgroup, age, and gender. Methods A cross-sectional survey of 666 AAPI individuals analyzed TB symptom recognition, transmission misconceptions, and awareness in two AAPI community centers. Data were segmented by AAPI subgroup, metropolitan area (Seattle/Tacoma vs. Las Vegas), age, and gender.Figure 3.TB transmission beliefs.Figure 4.TB treatment, curability, and latent TB infection awareness. Results Overall, 76.6% of respondents reported TB awareness, varying by AAPI subgroup. Awareness was highest among Korean (95%) and Filipino (91%) participants, and lowest among Vietnamese (52%) and Cambodian (50%) respondents. Regionally, TB awareness was similar between Tacoma (76%) and Las Vegas (79%). Age and gender significantly impacted awareness. Respondents under 18 had the lowest TB awareness (59%), while those aged 18-34 had the highest (84%). Females reported higher TB awareness (79%) and symptom recognition (61%) than males (74% and 46%, respectively). Symptom knowledge varied. 55% were aware of TB symptoms, but only 16% were able to recognize five common TB symptoms. Misconceptions about transmission also persisted broadly. Out of the 71% of respondents who were aware that TB is transmissible, many incorrectly believed TB spread via shaking hands (35%), sharing food/drinks (50%), or touching items in public areas (37%). The 45-64 and 65+ age groups were most prone to misconceptions about transmission. While 72% of respondents were aware that TB could be treated, only 57% knew TB could be cured. 30% of respondents were aware of latent TB infection. Conclusion Significant disparities in TB awareness exist in AAPI communities. Females demonstrated greater TB awareness perhaps due to cultural differences (“caretaker role”), while TB transmission misconceptions were prevalent among older individuals. Limited knowledge on LTBI and TB treatment represent significant barriers to effective TB control. Tailored educational efforts will be required to improve TB awareness and reduce misconceptions within AAPI communities. Disclosures All Authors: No reported disclosures

Abstract Background According to consensus guidelines, area under the concentration–time curve (AUC) is recommended for vancomycin dosing rather than trough-based monitoring, but transition to AUC-based dosing requires substantial staff education and resource allocation. We sought to evaluate the level of congruency between vancomycin total daily doses (TDD) determined using a trough concentration goal of 10-15 mcg/mL compared with an online Bayesian calculator targeting an AUC of 400-600 mg·h/L.Patient DemographicsInitial Dose Results Methods We performed a retrospective, multicenter cohort study of vancomycin therapeutic drug monitoring (TDM) in non–critically ill adults hospitalized from March 1, 2017-December 31, 2021. Patients were included if they received intravenous vancomycin for ≥72 hours with a documented trough target of 10 to 15 mg/L, had ≥1 serum vancomycin trough concentration assessed at steady state, and received ≥2 doses of vancomycin after serum assessment with or without dose adjustment. Using an online vancomycin calculator with Bayesian modeling, the study team input patients’ trough-based dosing data to retrospectively estimate the initial vancomycin AUC exposure achieved and the initial and post-trough TDD recommended for an AUC target of 400 to 600 mg⸱h/L. The initial and post-trough vancomycin total daily dose (TDD) derived by the online calculator were compared with the actual doses used for each patient when a trough concentration of 10 to 15 mg/L was targeted.Comparison of Trough-Based and AUC-Based Dosing of Vancomycin AUC indicates area under the concentration–time curve; TDD, total daily dose. Dashed line indicates where the 2 methods are equal; shading indicates where the 2 methods are within 20% of each other Results In total, 89 patients were included in the study. The actual vancomycin TDD with trough monitoring (target, 10-15 mg/L) was within 20% of the recommended AUC-based TDD for 62 patients (70%) with initial dosing and for 74 (83%) after the initial trough concentration. Nephrotoxicity was rarely observed (2%) and the median duration of vancomycin was 4 days. Conclusion Given the frequency of dosing similarity between 400-600 mg·h/L AUC and 10-15 mg/L trough-based dosing, vancomycin trough-based monitoring to a goal of 10-15 mg/L is an option warranting further exploration. Disclosures All Authors: No reported disclosures