Infectious Etiology Research Articles

Panniculitis: a narrative review.

Panniculitis is associated with a variety of disease processes that can be challenging to distinguish clinically. While diagnosis often relies on histopathology, sometimes this is not sufficiently diagnostic, which requires careful consideration of clinical features. We sought to provide an overview of the most common adult noninfectious panniculitis by reviewing not only the histological distinguishing features but also the clinical characteristics of various types of panniculitis including patient history, distribution, morphology, and other clues. A narrative review of both common and rare panniculitis primarily affecting the adult patient population was performed, with focus on recent English language publications. Additionally, both traditional and emerging therapeutic options are discussed. This article focused on diseases affecting predominantly adult populations and does not detail pediatric panniculitis or infectious etiologies. Overall, histopathology remains a key component in the diagnosis of panniculitis, but clinical characteristics provide substantial aid.

Infections in Patients with Atopic Dermatitis and the Influence of Treatment.

Atopic dermatitis (AD) is a T helper 2-mediated chronic inflammatory skin disease that affects children and adults. Patients with AD are prone to recurrent infections of the skin and other organs, which can severely worsen the disease course. This review summarises the current evidence on the aetiology, pathogenesis, treatment and prevention of infections in patients with AD. PubMed was searched for English-language research articles, systematic reviews, meta-analyses and guidelines published until February 2023 using the key term "atopic dermatitis" and terms relevant to infections. Patients with AD have an increased risk of bacterial, viral and fungal infections of the skin, mainly due to impaired barrier function, altered immune response and frequent scratching. The most common pathogens are Staphylococcus aureus and herpes simplex virus, which can cause impetigo, folliculitis, abscesses, eczema herpeticum and other complications. They also appear to increase susceptibility to systemic infections, including respiratory and urinary tract infections and sepsis. Certain systemic treatments for AD, such as mycophenolate mofetil and Janus kinase inhibitors, increase the risk of viral infections. Prevention and treatment of recurrent infections in patients with AD require a multifaceted approach that includes topical and systemic antimicrobials, skin care and effective control of AD symptoms (to break the itch-scratch cycle). Preventing and limiting the development of infections are important considerations in choosing an AD treatment.

MRSA-positive sternoclavicular septic arthritis mimicking mediastinal malignancy in a patient with multiple injection history: a rare case report

Introduction and importance: Infection of the sternoclavicular joint is exceptionally rare, accounting for less than 1% of bone infections. The presence of MRSA-positive septic arthritis in the sternoclavicular joint, coupled with its resemblance to mediastinal conditions and a history of multiple injections, presents a rare and complex clinical case that demands thorough evaluation and management. Case presentation: A 60-year-old male with a complex medical history, including hypertension, diabetes mellitus, hepatitis C, and recurrent cellulitis due to multiple IV and IM injections, presented with drowsiness and a painful, erythematous swelling of the left anterior chest wall. Clinical examination revealed pallor, distended abdomen, and decreased left-sided airway entry. Diagnostic workup showed elevated creatinine, metabolic acidosis, and inflammatory markers. Imaging revealed extensive soft tissue swelling and a mediastinal mass. A core biopsy confirmed severe acute and chronic inflammation, abscess formation, and granulation tissue suggestive of an infectious etiology. CT scans further identified sternoclavicular septic arthritis, a rare diagnosis. Clinical discussion: This case report describes MRSA-positive sternoclavicular septic arthritis in a patient with a history of tramadol and multivitamin injections. Sternoclavicular joint (SCJ) infection is rare, complicating differentiation from mediastinal malignancies. Successful management required embolization, IV antibiotics, and physiotherapy. Conclusion: MRSA-positive sternoclavicular septic arthritis, mimicking mediastinal malignancy, presents diagnostic challenges. Successful management involves tailored strategies, interdisciplinary collaboration, and consideration of IV drug injections.

Causes of HIV-related CNS infection in Cameroon, Malawi, and Tanzania: epidemiological findings from the DREAMM HIV-related CNS implementation study.

CNS infections cause approximately a third of HIV-related deaths. The Driving Reduced AIDS-Associated Meningo-encephalitis Mortality DREAMM study aimed to prospectively diagnose the aetiology of HIV-related CNS infection in five public hospitals in Cameroon, Malawi, and Tanzania. DREAMM was a multicentre, hybrid type-2 implementation science project. Adults (aged ≥18 years) presenting with a first episode of suspected CNS infection, who were HIV seropositive or willing to have an HIV test, were eligible for recruitment. Following implementation of the DREAMM model of care, we measured the prevalence of cryptococcal meningitis, tuberculous meningitis, bacterial meningitis, and cerebral toxoplasmosis and did a χ2 test to assess whether prevalence differed between countries. We also reported disease-specific mortality and Toxoplasma gondii seroprevalence. Of 356 participants with suspected CNS infection analysed at baseline, 269 (76%) were diagnosed as having a CNS infection. Of these, 202 (75%) had a confirmed diagnosis. Between Cameroon, Malawi, and Tanzania, the prevalence of the four main types of CNS infection differed (cryptococcal meningitis p=0·0014, bacterial meningitis p=0·0043, CNS tuberculosis p<0·0001, and toxoplasmosis p<0·0001). Cryptococcal meningitis (148 [55%] of 269) was the leading cause overall. The next most common causes were CNS tuberculosis in Tanzania (29 [29%] of 99) and bacterial meningitis in Malawi (15 [19%] of 80). In Cameroon, cerebral toxoplasmosis (39 [43%] of 90) was the leading cause followed by cryptococcal meningitis (36 [40%] of 90). For cryptococcal meningitis, all-cause 2-week mortality was 23% (34 of 147) and all-cause 10-week mortality was 45% (66 of 146). Within the study population, the aetiology of HIV-related CNS infection varied substantially between Malawi, Cameroon, and Tanzania. Additional prospective epidemiological data are needed to inform HIV programmes. 2-week cryptococcal meningitis mortality outcomes were similar to those of clinical trials. However, new interventions are urgently needed to sustain mortality reductions following hospital discharge. European and Developing Countries Clinical Trials Partnership and French Agency for Research on AIDS and Viral Hepatitis. For the French and Portuguese translations of the abstract see Supplementary Materials section.

Retrospective, descriptive study of acute myelitis in French Guyana.

Acute myelitis is a neurological entity, often posing the problem of etiology. The two main causes are infectious or autoimmune. French Guyana is a region of the world where infectious etiologies are multiple, in particular human immunodeficiency virus infection, and autoimmune diseases appear to be emerging. The aim of our study was firstly to determine the proportion of each etiology of acute myelitis in French Guyana, and secondly to describe the clinical, paraclinical and epidemiological characteristics of autoimmune myelitis in French Guyana, with particular reference to neuromyelitis optica spectrum disorder (NMOSD). This retrospective, observational study included all patients who presented with acute myelitis between January 2015 and August 2023 at Cayenne Hospital Center. Each patient's chart was reviewed and patients were classified according to etiology. Demographic and clinical data were collected, as well as blood, lumbar puncture, and cerebral and spinal cord magnetic resonance imaging results. Of the 40 patients included, immune etiology was found in 74%, including 49% with NMOSD (37% with positive anti-aquaporin-4 antibodies) compared with three patients with infectious etiology. There was no statistically significant difference in complementary examinations between immune and infectious etiologies. The prevalence of NMOSD in French Guyana was estimated at 8/100,000 (6/100,000 for patients with positive anti-aquaporin-4 antibodies). No significant difference in the geographic distribution of patients with NMOSD in French Guyana was demonstrated. Our results show a high proportion of autoimmune etiology of acute myelitis in French Guyana, and more particularly of NMOSD. There is a high prevalence of NMOSD, the second highest in the world after the French West Indies. Given this high proportion of autoimmune myelitis, several hypotheses can be put forward, with genetic and environmental factors in the foreground. For patients with acute myelitis in French Guyana, an immune cause is the most likely. It is therefore important to think about this and look for NMOSD in particular, without ignoring an infectious etiology.

P-1677. Assessing An Institution’s Approach to Management of Gram-Negative Bacteremia in High-Risk Populations

Abstract Background Immunocompromised populations present unique antimicrobial management and stewardship challenges. These challenges can persist despite existing stewardship policies. This study examined management of gram-negative bacteremia (GN-BSI) in a diverse immunocompromised population at the National Institutes of Health Clinical Center (NIH CC). Methods Episodes of GN-BSI admitted to the NIHCC from January 1 to December 31, 2023 were identified through positive blood culture results. Charts were abstracted for baseline demographics, episode-specific data, antimicrobial prescribing, and clinical outcomes. Results Seventy-five episodes of GN-BSI were identified. Thirty-six (48%) were undergoing cellular therapy and 54 (58.7%) were neutropenic. About 50.7% identified translocation as etiology of infection. Eleven (14.7%) were ESBL-positive by BCID2 panel. Seventy-two (96%) involved infectious disease (ID) consultation. Empiric choice of gram-negative antibiotics included ceftazidime/avibactam in 9 (12%) episodes, meropenem in 38 (50.7%) episodes, piperacillin/tazobactam in 15 (20%) episodes, and an anti-pseudomonal cephalosporin in 32 (42.7%). Twenty (26.7%) received 2+ empiric anti-pseudomonal antibiotics. After 72 hours, 37 (49.3%) still received meropenem with most isolates susceptible to narrower spectrum (Table 1). Similar results were seen with final ID recommendations (Table 2). Seven (10%) had transitioned to an oral agent by the seventh day. Comparing 72-hour antibiotic (Meropenem vs anti-pseudomonal cephalosporin), ICU admission (32.4% v 25%, p=0.62) and 30-day mortality (5.4% v 6.3%, p=0.87) were similar. Median therapy duration was 14 days (IQR 14-18.5). Of the 65 episodes with indwelling central venous access (CVAD), only 16 had removal of all CVADs. Those with CVAD removal had lower 30-d mortality (0% v 11.9%, p=0.22) though not statistically significant. Conclusion In a high-risk immunocompromised population, there is a low rate of narrowing gram-negative coverage at 72 hours although options for narrowing exist. Choice of empiric antimicrobial and targeted therapy for these GN-BSI episodes are the two major areas of improvement in our population. Primary teams and ID consultants should be involved in ongoing stewardship interventions. Disclosures All Authors: No reported disclosures

P-2120. Clinical significance of 16S rRNA sequencing identification of Legionella species

Abstract Background Incorporation of 16S rRNA sequencing into clinical diagnostics has improved the ability of clinicians to diagnose fastidious bacteria and facilitates the identification of causative organisms in culture-negative infections. However, its clinical utility is unclear, with estimates of antimicrobial management changes from 16S identification ranging from only 4-15%. Legionella species are fastidious bacteria that can be difficult to identify without prior clinical suspicion, and thus can cause culture-negative infections that lead to 16S sequencing. However, Legionella are found ubiquitously in aquatic environments and its identification on 16S could represent a clinically significant infection, a nonpathogenic sample isolate, or a contaminant from sample processing or analysis. In this study, we reviewed 16S Legionella species results from our institution and determined whether they represented a clinical infection. Methods 16S results from our institution were queried for Legionella species and a retrospective analysis of the resulting 10 cases was conducted. Multiple factors from the cases were assessed including demographics, comorbidities, type of 16S specimen, and antibiotic regimen change in response to 16S results. Additionally, we identified whether the 16S results represented clinically significant infections or contaminants. Results 70% of the Legionella identifications were indicative of a clinically relevant infection. Specimens from a pulmonary source were much more likely to represent a true infection, while identifications from extrapulmonary sources were more likely to be a contaminant. The species of Legionella identified on 16S did not impact the likelihood of a true causative agent. The 16S results affected antimicrobial regiments in 60% of the cases and were often the only diagnostic test to point towards Legionella as a causative agent. Conclusion Legionella species identification on 16S can be an important diagnostic clue to the etiology of a patient's infection, but various clinical factors should be taken into account when assessing whether the result represents a true infection or contaminant. Disclosures All Authors: No reported disclosures

P-1156. Procalcitonin Assay in Predicting Etiology in Young Febrile Infants Visiting the Emergency Department in Korea

Abstract Background There have been no studies conducted in Korea on the role of procalcitonin as a predictive factor for serious bacterial infection (SBI) in young febrile infants under 90 days of age, and it is not included in insurance reimbursement criteria despite its potential clinical utility. Our aim was to assess the role of the procalcitonin assay in distinguishing the etiology of fever, including SBI and simple urinary tract infection (sUTI), in young febrile infants in Korea. The sensitivity and the specificity of procalcitonin (≥0.5 ng/mL) for SBI and sUTI A. The sensitivity and the specificity of procalcitonin for SBI B. The sensitivity of the specificity procalcitonin for sUTI Methods This retrospective study was conducted on patients under 90 days of age who visited the pediatric emergency department (ED) at Severance Children's Hospital and underwent procalcitonin assay from January 2019 to February 2024. Patients who visited the ED for reasons other than fever or were under 29 days of age were excluded. The SBIs were defined as cases of the identification of pathogens in sterile fluids such as blood and cerebrospinal fluid, while sUTIs were defined as UTIs without bacteremia. Viral infections were defined as cases where a virus was identified through testing or when symptoms or contact history clearly indicated viral infection; otherwise, they were classified as unknown. The cut-off value for procalcitonin was set at 0.5 ng/mL. Results A total of 633 patients were collected, of whom 131 were excluded, resulting in 502 individuals included in the analysis. Among them, half were aged between 29-60 days and the other half between 61-90 days, with six admissions to the intensive care unit and no fatalities. By etiology, there were 22 cases of SBI (4.4%), 161 cases of sUTI (32.1%), 147 cases of viral infection (29.3%), and 172 cases classified as unknown (34.3%). The median values of procalcitonin were 5.03 (range, 0.08-100) for SBI, 0.35 (range, 0.05-52.2) for sUTI, 0.13 (range, 0.04-53.3) for viral infection, and 0.15 (range, 0.04-100) for unknown. The sensitivity of procalcitonin (≥0.5 ng/mL) for SBI and sUTI was 81.8% and 42.2% respectively, while the specificity was 77.8% and 88.3% respectively. (see Figure) Conclusion In febrile young infants in Korea, the utility of procalcitonin as a predictor of SBI is significant, warranting consideration for its proactive integration into clinical practice. Disclosures All Authors: No reported disclosures

P-819. Epidemiology of Serratia marcescens Bloodstream Infections in a Hospital System in the Southeast U.S

Abstract Background Serratia marcescens (Sm) is an environmental gram-negative bacilli that can cause a variety of serious human infections. Sm is frequently attributed as a hospital acquired infection. However, there is not extensive documentation as to the common etiologies of Serratia bloodstream infections (BSI), frequency of antibiotic resistance, and risk factors for recurrent infection or mortality. Methods We conducted a retrospective chart review of a cohort of patients (pts) ≥ 18 years old with Serratia marcescens BSI from 5/2016 to 10/2022 at our hospital system. Sm BSI was defined as ≥ 1 blood culture positive for Sm. Multidrug resistance was defined according to Centers for Disease Control (CDC) criteria. Patients were assessed for outcomes of recurrence of bacteremia (positive blood culture with same isolate within 3 months of clearance) and 30-day mortality. Results A total of 243 patients had Sm BSI during the study period. The most frequent etiology was central line-associated BSI (38%) followed by skin and soft tissue infection (12%). The majority (96%) of isolates were not multidrug resistant. Most patients had a repeat blood culture (67%), and of these patients, 15% had recurrence of bacteremia. A total of 44 patients (18%) died within 30 days. Echocardiogram was performed in 60% of our patients, with 7 patients diagnosed as having endocarditis or device endocarditis. Current active or history of injection drug use occurred in 7.5% of patients. Conclusion Our retrospective study demonstrates a low burden of antibiotic resistance in Sm at our hospital system. Similar to prior studies, CLABSI is a frequent cause of Sm BSI, and foreign materials/devices are common in patients with Sm BSI. Our patient population has a lower rate of IVDU compared to other studies of Sm BSI, and endocarditis is not common. Further analysis is needed to evaluate treatment regimens and other risk factors for recurrent BSI and mortality. Disclosures All Authors: No reported disclosures

P-2355. Etiology and symptoms of respiratory tract infections among nursing home residents: Results from multiplex respiratory pathogen testing in the Nursing Home Public Health Response Network, February – April, 2024, United States

Abstract Background Respiratory tract infections (RTI) cause high morbidity and mortality among nursing home (NH) residents, yet their etiology and frequency remain understudied. We implemented multiplex respiratory panel (MRP) testing to describe RTI epidemiology in NH residents to inform efforts to reduce respiratory virus transmission in NH. Figure 1 Flow diagram and multiplex respiratory panel testing results of SNF residents in NH-PHRN, February–April, 2024. Methods The Nursing Home Public Health Response Network (8 academic sites and 22 affiliated NHs) is conducting RTI surveillance with MRP testing. Staff collect nasal swab (NS) specimens and clinical data from symptomatic residents with suspected RTI. Specimens are collected within 72 hours of symptom onset and tested with the Roche ePlex Respiratory Pathogen Panel 2 (17 viral and bacterial pathogens, Figure 1) in a central laboratory. We describe MRP results, symptoms, and characteristics of residents tested during February–April 2024. We compared symptoms between NH residents with and without viral detection on MRP with Chi-Squared and Fisher Exact tests. Figure 2 Multiplex respiratory pathogen testing results among 81 enrolled residents in 19 nursing homes in NH-PHRN, February – April 2024, United States. *One resident tested positive for both Human Rhinovirus/Enterovirus and Coronavirus. **Influenza A subtype was H3 for all four specimens. Results Of 106 symptomatic residents with suspected RTI, 81 (72%) were tested (Figure 1). MRP detected ≥1 virus in 36/81 (44%) specimens; SARS-CoV-2 was the most common (14%), followed by seasonal coronavirus (12%) (Figure 2). Among residents tested, cough (78%), runny nose (43%), and sore throat (31%) were the most common symptoms. Sore throat was more common among residents with viral detection (53% vs. 13%; P=0.0001) (Figure 3). Of 75 tested residents with demographic and clinical data, median age was 80 (range 53–90), 59% were female, 19% were Black, 68% were long stay ( &amp;gt;100 days), and 99% had received a COVID-19 vaccine. Among 52 tested residents with treatment and outcome data, 14 (27%) received antibacterials, 11 (21%) were hospitalized, and 3 (6%) died. Of 25/52 residents with viral detection on MRP and complete treatment and outcome data, 4 (16%) received antibacterials, 6 (24%) were hospitalized (SARS-CoV-2 = 3, seasonal coronavirus = 2, Influenza A = 1) and none died. Figure 3 Frequency and percentage of symptoms and other clinical characteristics among 81 residents who underwent multiplex respiratory pathogen specimen collection in 19 nursing homes in NH-PHRN, February – April 2024, United States. We used Chi-Square and Fisher Exact tests to compare the type and frequency of symptoms among residents who had multiplex tests with and without pathogens detected. One asymptomatic resident who had no pathogen detected was tested due to leukocytosis. *Comparison P=0.04. **Comparison P=0.01. ***Comparison P=0.0001. Conclusion MRP testing identified a virus in almost half of tested NH residents with suspected RTI at the end of the viral respiratory season. Ongoing surveillance will help describe the burden and clinical relevance of viral respiratory pathogens in NH residents and identify areas of improvement for respiratory virus infection prevention. Disclosures Yasin Abul, MD, Moderna: Grant/Research Support|Moderna, Abt, CDC: Grant/Research Support David Canaday, MD, Moderna: Grant/Research Support|Pfizer: Grant/Research Support Jon P. Furuno, PhD, Merck &amp; Co., Inc: Grant/Research Support Stefan Gravenstein, MD, MPH, CDC: Advisor/Consultant|CDC: Grant/Research Support|Genentech: Advisor/Consultant|Genentech: Grant/Research Support|Genentech: Honoraria|GlaxoSmithKline: Advisor/Consultant|GlaxoSmithKline: Grant/Research Support|GlaxoSmithKline: Honoraria|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Janssen: Honoraria|Moderna: Advisor/Consultant|Moderna: Grant/Research Support|Moderna: Honoraria|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Grant/Research Support|Sanofi: Honoraria|Seqirus: Advisor/Consultant Lona Mody, MD, MS, Nanovibronix: Grant/Research Support Morgan Katz, MD, MHS, Ageless Innovation: Advisor/Consultant

P-902. Etiology, Clinical Characteristics, Prognosis and Outcomes of Acute Central Nervous System Infections: A Prospective Study

Abstract Background Various pathogens can cause central nervous system (CNS) infections. Early recognition and treatment significantly improves outcomes. Clinical features and outcomes vary by etiology and clinical phenotype, making diagnosis challenging. We report a single-center experience emphasizing the clinical profile and prognostic factors of this entity. Methods We conducted a two-year prospective, observational study at a tertiary care center in Western India. Patients suspected to have CNS infections underwent a standardized workup that included neuroimaging and CSF polymerase chain reaction panel testing. Patients were followed throughout the admission. The outcomes recorded were duration of intensive care unit (ICU) stay, hospital stay, modified Rankin Scale (mRS) at discharge and mortality. Results We included 75 patients (53 male, 22 female). The mean age was 43±19 years. Most infections were viral (69%) – 40% encephalitis, 17% meningitis and 12% meningoencephalitis. Viral infections surged in the monsoon and post-monsoon period (Fig. 1). Tuberculous meningitis accounted for 16% cases, pyogenic meningitis for 7%, and cryptococcal meningitis for 5%. Mucor cerebritis and brain abscesses accounted for 3%. Presenting symptoms, CSF, and neuroimaging findings are listed in Fig. 2-4. Mortality was highest for cryptococcal meningitis (25%); followed by pyogenic meningitis (20%); and viral encephalitis and tuberculous meningitis (16.7% each). Increased risk of mortality was observed with: new-onset seizures (relative risk [RR] 3.58, 95% confidence intervals [CI] 1.03-12.45, p&amp;lt; 0.001); a Glasgow Coma Scale (GCS) &amp;lt; 8 (RR: 6.85, 95% CI 2.00-23.40, p=0.002); and the presence of dilated ventricles on imaging (RR: 5.25, 95% CI 1.99-13.82, p&amp;lt; 0.001). Increasing age correlated with a longer ICU stay (r=0.37, p&amp;lt; 0.001), hospital stay (r=0.33, p=0.002), and worse functional status at discharge reflected by a higher mRS (p=0.04). GCS at presentation correlated inversely with functional recovery reflected by the mRS at discharge (p&amp;lt; 0.001). CSF findings varying by etiology CSF findings varying by etiology Conclusion The etiology and prognosis of acute CNS infectious varies by region and season. A detailed history, thorough physical examination, neuroimaging and CSF analysis are vital as each provides diagnostic and prognostic information. Disclosures All Authors: No reported disclosures

434. Reduced Gut Microbiome Diversity and Compositional Characteristics are Associated with Postoperative Infection in Heart Transplant Recipients

Abstract Background The human microbiome has been linked to important clinical outcomes, including postoperative infection. Loss of diversity has been associated with drug resistant organism colonization, infection, immune defenses, epithelial barrier integrity, and death. The microbiome’s role in postoperative infection among heart transplant (HT) recipients remains poorly understood.Table 1Clinical CharacteristicsTable 1 Clinical Characteristics: Characteristics noted by number and percent or mean and Standard Deviation where appropriate. Abbreviations: ICM – Ischemic Cardiomyopathy; NICM – Non-ischemic cardiomyopathy; CKD – Chronic Kidney Disease; COPD – Chronic Obstructive Pulmonary Disease. Methods Stool microbiomes for 121 HT recipients were determined by metagenomic sequencing. Infections occurring in the first 100 days following transplant were aggregated. Infection was defined as the presence of a compatible clinical syndrome and a positive test result via culture, PCR, serology, or imaging. To determine if infection risk was related to stool microbiome composition, samples at the time of transplant were shotgun sequenced and taxonomy was determined using MetaPhLan 4. Alpha diversity was measured by inverse Simpson, beta diversity was measure by Bray-Curtis dissimilarity.Table 2:Infection Microbiology and Diagnoses Results Average age at HT was 53.6 years and 73% were male, and the cause of heart failure in 71% was nonischemic cardiomyopathy. 194 infections occurred among 72 (60%) patients (Table 2). The most common infections were pneumonia, bloodstream, surgical site, and urinary. Most infections were caused by bacteria, specifically Enterobacerales and Enterococci. (Table 2) Stool microbial Alpha diversity was lower in patients who developed infection; p=0.0026. (Figure 1) Stool microbiome composition also differed significantly between groups. Patients with postoperative infection experienced more single species expansions, most notably Enterococcus and Enterobacterales, which were common etiologies of infection. (Figure 2) Uninfected patients had more abundant obligate anaerobic taxa including Bacteroidetes, Lachnospiraceae, and Ruminococcaceae.Figure 1Alpha and Beta Diversity of Stool Microbiota: A. Stool microbiome alpha-diversity by inverse Simpson p= 0.0026 Wilcoxon. B. Stool microbiome beta-diversity by PcoA Bray-Curtis Dissimilarity p=0.026 PERMANOVA. Conclusion The stool microbiome of HT patients with postoperative infection is marked by lower alpha diversity and notable compositional differences including Enterococci and Enterobacterales expansion coupled with reduced Bacteroidetes, Lachnospiraceae, and Ruminococcaceae. Further study into the interaction between these organisms and the host are needed to better understand their role in infection. Disclosures All Authors: No reported disclosures

P-2246. Diagnostic Performance of a Rapid Host-Protein Test (MeMed BV) In Detecting Bacteremia in Children

Abstract Background The gold standard for detecting infections associated with bacteremia is blood cultures. Blood culture yield is low, contamination is frequent and results take 12-48 hours. MeMed BV® is a rapid, FDA-cleared, host-protein test to differentiate bacterial and viral infection, with sensitivity and specificity &amp;gt;90%, and negative predictive value &amp;gt;98%. Here, we assessed its performance in detecting bacteremia in children as early detection of invasive infections is paramount. Methods Multi-cohort analysis of 7 prospective diagnostic accuracy studies of febrile children with suspected infection at the Emergency Department and inpatients. Eligibility required inclusion in the original study, age 3 months to 5 years and blood culture ordered. Reference standard infection etiology was adjudicated by 3 experts based on review of comprehensive patient data including clinical outcomes. Experts were blinded to MeMed BV results. Cases with bacterial reference standard and positive blood cultures adjudicated as having non-contaminant growth were defined as bacteremia. Results 1987 patients were studied. The median age was 1.3 years (interquartile range 0.8-2.4); 54.6% were male and 46.7% were hospitalized. The most common ED discharge diagnoses were viral infection (33.6%), upper respiratory tract infection (20.0%), lower respiratory tract infection (16.1%). The prevalence of bacterial infection was 15.4%. MeMed BV diagnostic performance was evaluated against the reference standard and attained sensitivity of 89.9% (95%CI 85.6-93.0), specificity of 94.3% (95%CI 93.0-95.4), and NPV of 98.1% (95%CI 97.3-98.7) for identifying bacterial infection. 19 (1%) patients had bacteremia; among these, MeMed BV identified 14 with bacterial scores, 2 with equivocal scores, and 3 with viral scores, the latter positive for Kingella kingae (see Table for more details). Conclusion MeMed BV can aid in early detection of bacteremia in children. Disclosures Lior Kellerman, M.D, MeMed: Employee|MeMed: Stocks/Bonds (Private Company) Eran Eden, PhD, MeMed: Employee|MeMed: Stocks/Bonds (Private Company) Tanya Gottlieb, PhD, MeMed: Employee|MeMed: Stocks/Bonds (Private Company) Roy Navon, MSc, MeMed: Employee|MeMed: Stocks/Bonds (Private Company) Richard Bachur, MD, MeMed: Advisor/Consultant|UpToDate - WoltersKluwer: Advisor/Consultant|UpToDate - WoltersKluwer: Royalties - Editor

P-2087. Clinical Application of Broad-Range PCR in Pediatric Patients

Abstract Background Broad-range PCR (BRPCR) and next-generation sequencing (NGS) have the potential to be useful adjunctive tools in diagnosing the infectious etiology of a wide range of pediatric infections. We aimed to assess the clinical utility and application of BRPCR and NGS in children with suspected infections. Methods A retrospective chart review was performed on pediatric patients with clinical samples sent for BRPCR (University of Washington Molecular Microbiology Laboratory, Seattle, WA, USA) between January 2023 and December 2023. Data was extracted from the electronic medical record, and descriptive statistics were performed. Results 51 patients had 55 samples sent for BRPCR. The demographics and sample information are listed in Table 1. A total of 18 (35.3%) patients had an organism identified on culture or BRPCR that was contributory to the clinical picture. Of those, 4 (7.3%) were identified on culture but not on BRPCR, and 6 (11%) were identified on BRPCR but not on culture. 4 (7.3%) cases identified the same organism on culture and BRPCR, while 4 (7.3%) cases identified different organisms on culture and concomitant BRPCR. In 6 (11.8%) cases, antibiotics were de-escalated, and in 7 (13.7%) cases, antibiotics were discontinued. Conclusion BRPCR can be a valuable adjunct to identifying causative organisms in children with suspected infections and can help tailor antibiotic management. Our results highlight the potential impact of BRPCR results to reduce broad-spectrum antibiotic use. Further studies are needed to guide the optimal use of BRPCR and determine its clinical impact on management of pediatric infections. Disclosures All Authors: No reported disclosures

P-2235. Implementation of a Host-Protein Test (MMBV) Into Routine Care for Children Hospitalized with Symptoms of Lower Respiratory Tract Infection

Abstract Background Infectious etiology is often unclear in children hospitalized with symptoms of lower respiratory tract infection (LRTI), driving antibiotic misuse. A host-protein test (MMBV) exhibits high diagnostic accuracy for differentiating bacterial from viral etiology. Best practices for test implementation should be established. We evaluate the effectiveness of implementing MMBV into routine care without specific antimicrobial stewardship (AMS) education by assessing impact on antibiotic administration to children hospitalized with LRTI symptoms. Patient flow Eligibility required age 3 months to 5 years old and hospitalized with 1 or more of the following signs or symptoms that concern for lower respiratory tract infection (LRTI): accessory muscle use, chest pain, cough, crepitation or rales, decreased breath sound, dyspnea, prolonged expiration, wheezing. MMBV, MeMed BV. Methods Retrospective pragmatic study of MMBV implementation at a single medical center without specific AMS education. Children 3 months to 5 years old hospitalized with LRTI symptoms were included. In the non-interventional arm (2014-2017) MMBV results were not available in time to impact antibiotic decisions. In the interventional arm (2021-2022) MMBV results were rapidly available. Patients were assigned into discharge diagnosis classes: bronchiolitis, community acquired pneumonia (CAP), viral diagnosis and other diagnosis. Antibiotic administration was compared between arms per diagnosis class. The relative reduction in antibiotic administration in the interventional arm versus the non-interventional arm according to discharge diagnosis class There was a relative reduction in antibiotic administration in the interventional arm relative to the non-interventional arm from 60.0% (12/20) to 22.5% (9/40) for bronchiolitis; from 98.7% (74/75) to 97.3% (71/73) for CAP; from 15.0% (12/80) to 13.3% (6/45) for viral diagnosis; and from 60.7% (51/84) to 51.8% (43/83) for other diagnosis. P-values were calculated using Richardson’s method. CAP, community-acquired pneumonia. Results Age, sex and MMBV results were similar across arms. Viral MMBV rates were high (39%-90%) across all diagnosis classes in the non-interventional (n=259) and interventional (n=241) arms. A significant relative reduction in antibiotic administration of 62.5% (p=0.004) was attained in patients discharged with bronchiolitis without impacting length of stay (p=0.530). Non-significant reductions in antibiotic administration were observed for CAP, viral diagnosis and other diagnosis. Conclusion MMBV availability is associated with judicious antibiotic administration to children hospitalized with bronchiolitis without AMS education. Combining MMBV introduction with AMS education is required to reduce potentially unwarranted antibiotics in children hospitalized with CAP. Disclosures All Authors: No reported disclosures

Historical Control Data of Spontaneous Lesions of Laboratory New Zealand White and Dutch Belted Rabbits (Oryctolagus Cuniculus) Used in Toxicity Studies.

A retrospective study was performed to determine the incidences of spontaneous findings in control laboratory New Zealand White (NZW) and Dutch Belted (DB) rabbits. Terminal body and organ weights data were also collected. A total of 2170 NZW (526 males/1644 females), 100 DB rabbits (50 animals per sex), aged 4- to 7-month-old were obtained from 158 non-clinical studies evaluated between 2013 and 2022. The NZW rabbits had greater mean terminal body weights than DB strain. Mixed cell infiltration in the lung was the most recorded finding in both strains, followed by pulmonary inflammation/mononuclear cell infiltration. Differentiation between pulmonary "infiltration"/"inflammation" remained challenging as interpretation of guidelines for diagnostic terminology may vary amongst pathologists. Other common findings included mineralization and basophilia of the renal tubules; hepatic/renal mononuclear cell infiltration, all more common in females. Cysts were commonly recorded, with high prevalence in the oviduct, thyroid gland, ovary in NZW strain, while uterine, pituitary gland, and thyroid gland cysts were the most identified in DB rabbits. Neoplasms and infectious etiologies were absent. Most of the animals were sexually mature. To our knowledge, this is the most recent comprehensive study of spontaneous lesions and organ weights in both rabbit strains and should facilitate the differentiation of spontaneous and induced lesions in safety studies.

Case Report: 18F-FDG PET/CT for FUO Due to Whipple Disease Infection.

We present the case of a 60-year-old man admitted to the hospital presenting with high FUO (fever of unknown origin), strong headache, face erythematous-desquamative cutaneous lesions, long history of abdominal pain, and diffuse myalgia. He was also previously treated with immunosuppressants and currently managed with corticosteroids for a seronegative rheumatic disease. Given the immunocompromised state, an infective etiology was suspected. The patient was referred, as part of standard clinical practice, to perform an 18F-FDG PET/CT to identify potential causes of FUO.

The role of Acinetobacter baumanii in the etiology of nosocomial infections and possible options for rational antibiotic therapy in adults and children

In the mid‑20th century and later, the main bacterial threat in hospitals was gram-positive infections, with staphylococcus aureus (“staphylococcal plague”) playing the leading role. In the last 20 years, there has been an evolution, a change in flora, and now gram-negative infections, especially the triad (A. baumanii, K. pneumoniae, P. aeruginosa) from the ESCAPE group, determine hospital morbidity and mortality due to increasing resistance to carbapenems and cephalosporins and, accordingly, limited choice. In the review concerning the treatment options for A. baumanii in adults and children (especially infants and neonates), antibiotic therapy options are considered.

A Comprehensive Systematic Review of Etiology and Risk Factors of Surgical Site Infections

Introduction: Surgical wound infections (SWIs) remain a significant risk to patients due to their high morbidity and mortality rates. Moreover, they pose substantial economic challenges for both developing and developed countries. The global impact of these infections is staggering, with the World Health Organization (WHO) reporting that millions of patients worldwide are affected by hospital-acquired infections annually, with many succumbing to these infections. This study aims to analyze the incidence of surgical site infections (SSIs) based on the type of surgical intervention, identify the most frequent causes of these infections, and explore effective management strategies. The findings of this study will provide valuable insights into the prevention and management of SSIs, thereby enlightening the medical community and empowering them to improve patient outcomes. Material and Methods: This study, conducted with meticulous attention to detail, focuses on patients operated on in our clinic from January to October 2024. It will reflect the incidence of SSI according to the type of surgical intervention, the most frequent causes of these infections, and the way of their treatment. Results: From January 2023 to June 2024, 788 patients were hospitalized, and 408 were operated on in the Surgery Department of the Clinical Hospital of Tetovo. Three hundred fifty were male, and 438 were female. The ages of the patients included in the study ranged from 21 to 81. Most of the patients were operated on because of cholecystolithiasis, inguinal, ventral, and umbilical hernias, breast cancer, acute appendicitis, and neoplasia of the colon and ileus. From the total number of operated patients (408), the infection of operative wounds was recorded in 49, representing an incidence of 11.76 %. Conclusion: The findings of this study underscore the serious global implications of SSIs, including increased morbidity and mortality rates and the strain on healthcare budgets. Therefore, the prevention and reduction of these infections should be a priority for all countries, irrespective of their economic status.

Quorum sensing regulates virulence factors in the coral pathogen Vibrio coralliilyticus.

The bacterial pathogen Vibrio coralliilyticus causes disease in coral species worldwide. The mechanisms of V. coralliilyticus coral colonization, coral microbiome interactions, and virulence factor production are understudied. In other model Vibrio species, virulence factors like biofilm formation, toxin secretion, and protease production are controlled through a density-dependent communication system called quorum sensing (QS). Comparative genomics indicated that V. coralliilyticus genomes share high sequence identity for most of the QS signaling and regulatory components identified in other Vibrio species. Here, we identify an active QS signaling pathway in two V. coralliilyticus strains with distinct infection etiologies: type strain BAA-450 and coral isolate OCN008. In V. coralliilyticus, the inter-species AI-2 autoinducer signaling pathway in both strains controls expression of the master QS transcription factor and LuxR/HapR homolog VcpR to regulate >300 genes, including protease production, biofilm formation, and two conserved type VI secretion systems (T6SSs). Activation of T6SS1 by QS results in the secretion of effectors and enables interbacterial competition and killing of prey bacteria. We conclude that the QS system in V. coralliilyticus is functional and controls the expression of genes involved in relevant bacterial behaviors typically associated with host infection.IMPORTANCEVibrio coralliilyticus infects many marine organisms, including multiple species of corals, and is a primary causative agent of tissue loss diseases and bacterial-induced bleaching. Here, we investigated a common cell-cell communication mechanism called quorum sensing, which is known to be intimately connected to virulence in other Vibrio species. Our genetic and chemical studies of V. coralliilyticus quorum sensing uncovered an active pathway that directly regulates the following key virulence factors: proteases, biofilms, and secretion systems. These findings connect bacterial signaling in communities to the infection of corals, which may lead to novel treatments and earlier diagnoses of coral diseases in reefs.