bluuebunny/crossref_metadata_2025 huggingface dataset:
229. Predictive markers for bacteremia in patients receiving extracorporeal membrane oxygenation (ECMO) support
Authors: Hendrix Curtis , Radcliffe Christopher , Tantawy Hossam , Roberts Scott C
Published: November 2023

Background

Patients receiving extracorporeal membrane oxygenation (ECMO) support are critically ill, which can confound the usual metrics clinician use to diagnose bacteremia. The best methods to detect bacteremia in patients receiving ECMO support are unknown, and we sought to evaluate the accuracy of various metrics used in determining bacteremia.

Methods

A retrospective review of patients receiving ECMO support at Yale New Haven Hospital from April 2020 to September 2021 who had blood cultures obtained for any reason was performed. Reasons for blood culture and metrics associated with bacteremia, including white blood cell count (WBC), maximum daily temperature, and procalcitonin, were evaluated for each blood culture event. If patients became bacteremic, only the first positive blood cultures were included in the analysis. Receiver operator curves for each metric were performed to generate areas under the curve (AUC) for assessing diagnostic accuracy.

Results

60 patients who required ECMO support had 132 blood cultures performed, 22 (16.7%) with bacteremia and 110 (83.3%) without. In blood cultures with bacteremia compared to those without, there was no difference in WBC count (17.4 vs 17.9, p = 0.825), maximum daily temperature (37.1 vs 36.9 C, p = 0.572), or procalcitonin (2.0 vs 2.2, p = 0.776) on the day of culture. The most predictive reason for obtaining blood cultures with confirmed bacteremia was hemodynamic instability (AUC 0.668), followed by temperature dysregulation (AUC 0.623). Reasons for obtaining blood cultures minimally associated with bacteremia included adding ice to the ECMO circuit (AUC 0.527), leukocytosis (AUC 0.523), respiratory decompensation (AUC 0.500), surveillance culturing (AUC 0.432), and other reasons not specified but per clinician discretion (AUC 0.386).

Conclusion

Hemodynamic instability as the reason for obtaining blood cultures was the most predictive of bacteremia in patients on ECMO support, while leukocytosis, temperature change, and surveillance cultures were less well associated. There was no difference in WBC counts, maximum daily temperature, and procalcitonin in patients with bacteremia versus those without. Optimizing clinical criteria to determine bacteremia in patients on ECMO remains challenging and warrants further study.

Disclosures

All Authors: No reported disclosures
235. Investigation of the relationship between the number of positive blood cultures and patient prognosis
Authors: Sekiya Satoru , Hasegawa Ryo , Shibutani Koko , Lee Mihye , Mori Nobuyoshi
Published: November 2023

Background

The relationship between the number of positive blood cultures (NPBCs) and clinical outcomes has not been well-studied. The purpose of this study was to assess the impact of NPBCs (one set or two) on clinical outcomes.

Methods

We conducted a retrospective study comparing the clinical features of two sets of positive blood cultures (NPBCs=2) and one set of positive blood culture (NPBCs=1) in adult patients with bacteremia and fungemia from 2004 to 2021 at a tertiary hospital in Tokyo, Japan. We focused on four pathogens commonly encountered in clinical practice, including Staphylococcus aureus (S. aureus), Streptococci, gram-negative rods (GNR) (Enterobacterales and Pseudomonas aeruginosa), and Candida species, as the true causative pathogens in bacteremia and fungemia. The primary outcome was in-hospital mortality, and secondary outcomes were ICU admission and use of vasopressor drugs.

Results

In univariate analysis, NPBCs=2 for S. aureus was associated with vasopressor use, and NPBCs=2 for Streptococci was linked to a higher rate of ICU admission. However, these differences were not significant in multivariate analysis. Interestingly, NPBCs=2 for S. aureus had a positive impact on in-hospital mortality compared with NPBCs=1 (OR 0.574, 95%CI 0.376–0.877, p < 0.05). NPBCs for Candida species did not affect clinical outcomes. Furthermore, NPBCs=2 for GNR was associated with vasopressor use (OR 1.62, 95%CI 1.27–2.07, p < 0.05) in both univariate and multivariate analysis. We performed logistic regression analysis using the five items with the highest clinical significance: NPBCs=2, serum Cr > 1.2 mg/dL, Hb < 12 g/dL, heart rate > 90 beats/min, and platelet count < 150,000/μL. Based on the β coefficient, we assigned scores to each item and created a STAT-2 (S: Serum Cr, T: Thrombocytopenia, A: Anemia, T: Tachycardia, 2: NPBCs=2) score for the use of hypertensive drugs for GNR. The receiver operating characteristic (ROC) curve for the STAT-2 score with a cutoff of 6 points or higher had an area under the curve (AUC) of 0.763. The specificity was 90.8%, with a positive likelihood ratio of 4.13 (95% CI 3.40-5.02).

Conclusion

Our study suggests that NPBCs can predict clinical outcomes in patients with certain pathogenic infections.

Disclosures

All Authors: No reported disclosures
237. Elizabethkingia species: An Emerging Cause of Healthcare-Associated Bloodstream Infection Among Immunocompromised Hosts
Authors: Stewart Adam , Laupland Kevin , Edwards Felicity , Paterson David , Harris Patrick N A
Published: November 2023

Background

Elizabethkingia species are environmental opportunistic pathogens that are a rare but potentially severe cause of bloodstream infection (BSI). The objective of this study was to determine the incidence, risk factors, and outcomes of Elizabethkingia species BSI in a large Australian population.

Methods

Retrospective, laboratory-based surveillance was conducted among residents of Queensland, Australia (population approximately 5 million) over a twenty-year study period. All microbiological data was collected from a government-funded, centralised laboratory service. Clinical and outcome information was obtained from statewide databases.

Results

During 86 million person-years of surveillance, 112 incident Elizabethkingia species BSI occurred for an annualized age and sex-standardized incidence of 1.4 per million residents. Elizabethkingia species isolates were identified as E. meningoseptica in 104 (93%) and were not speciated in 8 (7%). Fifty-three percent were male, and the median age was 69 years (IQR, 55-80). Almost 80% were hospital onset or healthcare-associated BSI, and the median length of hospital stay being 10 days (IQR, 5-30). Comorbidity was common with a median Charlson Co-morbidity Index of 3 (IQR, 1-4), with 25% having active malignancy. Almost 80% were monomicrobial infections, with the majority having no focus identified. Ninety-day overall case-fatality rate was 23%. In vitro susceptibility to ciprofloxacin, sulfamethoxazole, piperacillin-tazobactam was 75%, 71%, 18%, respectively; all isolates were resistant to vancomycin.

Conclusion

Elizabethkingia species BSI is an important cause of opportunistic infection, particularly among vulnerable hosts. Although uncommon, it is associated with a high case-fatality rate and limited antibiotic treatment options due to intrinsic resistance mechanisms.

Disclosures

David Paterson, AMR Action Fund: Board Member|Entasis: Board Member|Merck: Board Member|Pfizer: Board Member|QPex: Board Member|Venatorx: Board Member Patrick N A Harris, PhD, DTMH, MRCP, FRACP, FRCPA, Merck: Advisor/Consultant|Opgen: Advisor/Consultant|Sandoz: Advisor/Consultant
241. Early switch from intravenous to oral antibiotics in patients with Gram-negative bacteremia – a target trial emulation
Authors: Tingsgård Sandra , Bastrup Israelsen Simone , Østergaard Christian , Benfield Thomas
Published: November 2023

Background

Gram-negative bacteremia is a global health concern, that continues to cause significant morbidity and mortality. Intravenous (IV) antibiotics are typically the first-line treatment; however, it is unclear when it is appropriate to switch to oral antibiotics in order to maintain positive outcomes. An early switch from intravenous to oral antibiotics may have several advantages, including reduced hospital stay, lower healthcare costs, and improved patient quality of life. This study investigates the effectiveness of early switch to oral antibiotics in patients with Gram-negative bacteremia using a target trial framework.

Methods

We outlined the protocol for a target trial to estimate the effect of 1) switching to oral antibiotics within four days after initial blood culture compared with 2) continuing IV antibiotic treatment throughout the treatment course on 90-day all-cause mortality. We then emulated the trial using a cohort of adult patients with Gram-negative bacteremia from 2018 through 2022 admitted to four hospitals in the Capital Region of Denmark. Patients who were immunosuppressed, transitioned to hospice care, had polymicrobial infection, were not clinically stable within four days of blood culture, or did not receive adequate empirical antibiotic treatment were excluded. Inverse probability of treatment weighting was applied to adjust for confounding. Intention-to-treat analysis was performed using pooled logistic regression to estimate absolute risk, risk difference, and risk ratio. 95% confidence intervals (CI) were computed using bootstrapping.

Results

1088 patients were eligible for inclusion in the study. Of these, 582 patients transitioned early to oral antibiotic treatment and 506 patients continued IV treatment. The absolute risk of 90-day all-cause mortality was 11.6% (95% CI 9.4;13.7) for patients switching early to oral antibiotics, and 13.4% (95% CI 11.2; 15.5) for patients continuing IV. The risk difference was -1.8% (95% CI -4.9; 1.3) and the risk ratio was 0.99 (95% CI 0.67; 1.13).

Conclusion

Our findings indicate that an early switch to oral antibiotic treatment within four days may be a safe and effective alternative to continued IV treatment in patients hospitalised with uncomplicated Gram-negative bacteremia.

Disclosures

All Authors: No reported disclosures
242. Evaluation of PBP4 promoter variation and clinical outcomes in patients with Enterococcus faecalis bacteremia
Authors: Atterstrom Rachel , Tran Truc T , Nisar Tariq , Panesso Diana , Singh Kavindra , Streling Ana , Rizvi Samie A , Simar Shelby R , Egge Stephanie , Dinh An , Contreras German , Hanson Blake M , Zervos Marcus , Abbo Lilian M , Shimose Luis , Shelburne Samuel A , Arias Cesar A , Miller William R
Published: November 2023

Background

Penicillin-binding protein 4 (PBP4) is a low affinity PBP that has been associated with decreased susceptibility to penicillins in Enterococcus faecalis (Efs). Changes in the promoter region leading to increased expression of the pbp4 gene contribute to this phenotype. There is limited data on the clinical outcome of patients infected with these strains in the U.S. We investigated the clinical outcomes of patients with Efs bacteremia stratified by PBP4 promoter type and piperacillin MIC.

Methods

Index Efs bloodstream isolates from 167 patients were selected from the VENOUS cohort (2016-2021). Whole genome sequencing was performed on all isolates and changes in the promoter region (200 bp upstream of the start codon) were identified, using Efs JH2-2 as reference. β-lactam susceptibility (ampicillin, penicillin, and piperacillin [PIP]) was performed on all isolates by broth microdilution. Clinical outcomes (in-hospital mortality, microbiologic failure, and recurrence) were collected on all patients.

Results

The median age for the cohort was 65 years (IQR: 56-72), and 63.5% were male. The median length of hospitalization was 13 days (IQR: 8-22). The duration of bacteremia was 3 days (IQR: 2-4) and 8.98% of patients had prolonged bacteremia (≥ 7 days). Among 167 isolates, 4 major primary promoter variants were identified: reference JH2-2 (n=66), ΔA88 (n=43), A175C (n=35), and insA192 (n=20). All strains were susceptible to ampicillin and penicillin. A PIP MIC ≥ 16 mg/L (non-susceptible) was found in 74.4% of strains with the ΔA88 promoter, as compared to 22.7% of reference, 17.1% of A175C, and 10% of insA192 (p < 0.001). Clinical outcomes of the 167 patients are shown in Table 1. PIP non-susceptibility was associated with immunocompromise state (49.09% vs 23.85%, p=0.001), history of hematological cancer (40% vs 16.51%, p=0.002), and recurrence (7.27% vs 0.92%, p=0.044). There was no statistical difference in mortality or microbiologic failure.

Conclusion

Isolates with ΔA88 PBP4 promoter variants were associated with PIP non-susceptibility. While in-hospital mortality and microbiologic failure were similar between all patients, those who were infected with a PIP non-susceptible strain were more likely to experience a recurrence.

Disclosures

Marcus Zervos, MD, Contrafect: Advisor/Consultant|GSK: Grant/Research Support|Johnson and Johnson: Grant/Research Support|Pfizer: Grant/Research Support Lilian M. Abbo, MD, MBA, Ferring: Advisor/Consultant|Pfizer: Advisor/Consultant|Regeneron: Grant/Research Support|Shionogi: Advisor/Consultant William R. Miller, M.D, Merck: Grant/Research Support|UpToDate: Honoraria
244. Predictors and Outcomes of Multi-Drug Resistant Gram-Negative Bacteremia in Patients with Solid Tumours
Authors: Varghese George M , Awada Bassem , Abarca Jorge , Milupi Maniyando , Al Moundhri Mansour
Published: November 2023

Background

Multi-drug resistant Gram-negative bacteraemia (MDR-GNB) is a major concern in cancer patients. However, predictors and outcomes of MDR-GNB bacteraemia in patients with solid tumours are not well defined. The objective of this study was to identify the predictors and outcomes of MDR-GNB bacteraemia in patients with solid tumours.

Methods

This retrospective cohort study was conducted on patients with solid tumours admitted to a tertiary care hospital between January 2022 and December 2022. Demographic, clinical, and microbiological data were collected from electronic medical records. Univariate and multivariate analyses were performed to identify the predictors of MDR bacteraemia. The outcomes of interest included in-hospital 30-day mortality, length of hospital stay, and recurrence of bacteraemia.

Results

Among 1074 patients with solid tumours, a total of 77 episodes of Gram-negative bacteremias occurred in 59 patients (47% male) with a mean age of 57.4 years. Of which 37(48%) had MDR-GNB bacteraemia. The most common source of bacteraemia was biliary (34.2%) followed by central line-associated (21%) and abdomen(21%). Carbapenem resistance was documented in 7(9.1%) of all Gram-negative bacteremias of which 75% were harbouring NDM with or without OXA-48 among enterobacteralis. The predictors of MDR-GNB bacteraemia were prior use of antibiotics (odds ratio [OR] 7.82, 95% [CI] 2.52,24.2) and E.coli bacteremia (OR 6.56, 95% CI 1.26,34.22). The median length of hospital stay was significantly longer in the MDR group compared to the non-MDR group (23 vs. 10.5 days; p= 0.003) and recurrence of bacteremia was significantly more common in the MDR group (35.13% vs. 5.0%; p=< 0.001). The 30-day in-hospital mortality was not significantly different (35.14% vs. 32.5%; p=0.81).

Conclusion

This study identifies prior use of antibiotics and E.coli bacteremias as predictors of MDR-GNB bacteraemia in patients with solid tumours. Patients with MDR-GNB bacteraemia had longer hospital stays, and higher recurrence rates compared to those with non-MDR-GNB bacteremias. This highlights the importance of the judicious use of antibiotics and infection control measures to prevent MDR-GNB bacteraemia in this population.

Disclosures

All Authors: No reported disclosures
252. Alveolar Macrophages Modulate Host Inflammatory Responses to Pulmonary Melioidosis
Authors: Baker Sarah M , West Timothy E
Published: November 2023

Background

Melioidosis is an emerging infection caused by the facultatively intracellular pathogen and Tier 1 select agent Burkholderia pseudomallei (Bps). Pneumonia, the most common manifestation of melioidosis, predicts poor prognosis, yet the pulmonary immune response to Bps is poorly understood. Alveolar macrophages (AMs) are innate immune cells in the lung and are distinct from monocytes and other macrophages in their response to pathogens, yet their role in host defense against melioidosis is unknown. We sought to determine if AMs modulate bacterial replication, dissemination, pulmonary inflammatory response, and health outcomes to Burkholderia using a murine model of melioidosis.

Methods

To deplete mice of AMs, we instilled 100μl clodronate-liposomes or PBS-liposomes intratracheally into C57Bl/6 mice and confirmed AM depletion by flow cytometry. Twenty-four hours after AM depletion, we infected mice by aerosolization with a sub-lethal dose of 7.8 x 103 CFU/lung of B. thailandensis (Bt), a BSL-2-compliant surrogate model of Bps infection. At 24 and 48 hours after infection we quantified pulmonary bacterial burdens, bacterial dissemination to the spleen, lung homogenate cytokines, and clinical markers of illness (health score, weight, and temperature) in mice depleted of AMs and compared these to sham-depleted mice.

Results

Mice deplete of AMs had fewer bacteria in the lungs 24 hours after infection and similar numbers of bacteria at 48 hours; there were no differences in bacterial dissemination or clinical health outcomes. Mice deplete of AMs produced less of the inflammasome-associated cytokines IL-18 and IL-1β at 24 and 48 hours and produced less of the pro-inflammatory cytokine TNF-α

and the neutrophil chemokine MIP-2 at 24 hours. When adjusting for lung bacterial CFUs, mice deplete of AMs still produced less IL-1β at 24 hours.

Conclusion

In a murine model of sub-lethal pulmonary melioidosis, AMs do not contribute to early bacterial restriction and may instead act as an intracellular Burkholderia replication niche or otherwise facilitate replication in the lung. However, AMs are likely to be a main source of IL-1β in the lung, signifying their relevance in the canonical inflammasome pathways implicated in host response melioidosis.

Disclosures

All Authors: No reported disclosures
262. Inhibiting macrophage Warburg effect blocks DNA hyper-methylation and restores immune function
Authors: Abhimanyu Abhimanyu , Ladki Malik , Sheikh Daanish , Nishiguchi Tomoki , Carrero Longlax Santiago , DiNardo Andrew
Published: November 2023

Background

Severe and chronic infections, such as sepsis and Tuberculosis (TB), lead to epigenetic-mediated immune suppression. Cancer studies have demonstrated that perturbations in TCA cycle intracellular metabolites trigger global changes in the epigenetic landscape, resulting in immune suppression that persists after microbial eradication. Therefore inhibiting the TCA cycle may mitigate epigenetic-mediated immune suppression.

Methods

We applied complementary approaches, including data mining public tuberculosis and sepsis datasets, an in vitro LPS-stimulated macrophage tolerance model, DNA methylation (Methyl EPIC), confocal microscopy, and reverse phase protein array (RPPA) to investigate mechanisms of post-infectious immune suppression. Results were validated in tuberculosis patients in a clinical trial using an mTOR inhibitor.

Results

Patients with TB and sepsis both demonstrated increased expression of genes involved in glycolysis and the tricarboxylic acid (TCA) cycle, which correlated with an increase in DNA methylation. Human monocytes stimulated with LPS in vitro developed immune tolerance that correlated with DNA hypermethylation. LPS induced the TCA enzymes isocitrate dehydrogenase, citrate synthetase, as well as DNMT3b to translocate into the nucleus. Inhibition of TCA cycle overactivation blocked LPS-induced immune suppression and DNA hyper-methylation. Phase 2 TCA metabolites succinate and itaconate mimicked LPS-induced immune suppression and DNA hyper-methylation. In vitro studies were validated in vivo with TB patients receiving mTOR inhibition (everolimus) having less DNA hyper-methylation.

Conclusion

TCA cycle activation regulates DNA methylation and immune tolerance. These in vitro and in vivo studies demonstrate that inhibiting the TCA cycle can mitigate epigenetic-mediated immune silencing, potentially identifying a means to prevent post-infectious immune suppression.

Disclosures

All Authors: No reported disclosures
267. Small colony variants causing Prosthetic joint infection depict a different gene expression profile
Authors: Fernández-Rodríguez Diana , Carlos-Escalante José Alberto , Esaú López-Jácome Luis , Adriana Colin-Castro Claudia , Hernández-Durán Melissa , García-Contreras Rodolfo , Maeda Toshinari , Delgado Gabriela , Morales-Espinosa María del Rosario , Franco-Cendejas Rafael
Published: November 2023

Background

Prosthetic joint infection (PJI) is an infectious complication after total joint arthroplasty (TJA) with a high socioeconomic impact. Staphylococcus species attain for more than half of PJI cases. Biofilm formation and the development of small colony variants (SCV) have proven to enhance chronic and/or relapsing bacterial infections. In this regard, a better understanding of these factors can help overcome PJI and other device-associated infections. Thus, we aimed to analyze the clinical and microbiological differences between common/wild type (WT) and SCV Staphylococcus epidermidis strains

Methods

We analyzed a monomicrobial cohort of PJI patients affected by S. epidermidis. The bacterial isolates of patients with more than one-year of follow-up were examined for SCV detection. Then, we determined the genetic relatedness between strains with a pulsed field gel electrophoresis (PFGE). Finally, we selected 4 representative strains (2 WT and 2 SCV strains) to perform a differential expression analysis by RNA-seq. We performed a multiple test correction by controlling the false discovery rate (FDR) at 10%.

Results

S. epidermidis SCV affected 16 (37.6%) patients with monomicrobial PJI. The DNA fingerprints showed a high similarity, according to the Dice coefficient, between SCV strains and their WT counterparts. Nevertheless, further experiments demonstrated 22 genes with a significant differential expression profile: 12 were associated to metabolic pathways (carbon, amino acids, nucleotide, purines) and biosynthesis of secondary metabolites and cofactors, 3 with transmembrane transportation, 2 with redox balance, 1 with pH balance, 1 with integral components of the membrane and cell adhesion. Function was not identified for 3 of these genes.

Differential gene expression profile among SCV isolates causing prosthetic joint infection.

Conclusion

SCV are common in device-related infections like PJI. S. epidermidis SCV and their WT counterparts showed an extremely similar genetic background: still, SCV strains have a different gene expression profile. These findings explain some phenotypic variations (growth rate, biofilm properties, antimicrobial susceptibility profiles) found in clinical SCV strains. These genes may be promising therapeutic targets for combating chronic and/or relapsing bacterial infections.

Disclosures

All Authors: No reported disclosures
268. Human Mesenchymal Stem Cells Augment Neutrophil Function to the Human Fungal Pathogen, Candida albicans
Authors: Floyd Daniel , Tan Yuan , Souza-Moreira Luciana , Mei Shirley H J , Timmer Kyle , Mansour Michael
Published: November 2023

Background

Neutrophils are critical innate immune cells that play a crucial role in protection against invading pathogens. Mesenchymal stem cells (MSC) are multipotent progenitors that can differentiate into osteoblasts, chondrocytes, and adipocytes and possess immunomodulatory effects. MSC are the focus of clinical investigation in various comorbidities, including diabetes, cancer, and invasive infections.

Methods

Human MSC were derived from bone marrow and have been characterized to meet all criteria of MSC (ISCT guideline). Cells were seeded at 100,000 cells per well in fibronectin (50ug/mL)-coated 24-well plate and incubated for 24 hours at 37°C, 5% CO2. The next day, 0.5 mL of whole blood from three healthy donors was added for another 24 hours, after which the neutrophils were isolated, viability measured, and a high throughput multiparametric neutrophil function assay was performed, compared to non-MSC exposed neutrophils (control neutrophils). Functions tested included ROS (dihydrorhodamine 123 (DHR123), phagocytosis of iRFP-expressing Candida albicans, ectodomain shedding (loss of CD62L), and degranulation (increased expression of CD66b). Multiparametric assays were measured on a BD FACS Celesta 4 laser flow cytometer and data was analyzed on FlowJo software.

Results

Neutrophils co-cultured with MSC had an average viability of 96.3% compared to control neutrophils at 92.15%. Using the multiparametric neutrophil functional assay, neutrophils exposed to MSC ex vivo had increased functional responses to the fungal pathogen Candida albicans. MSC-conditioned neutrophils exhibited a 33.2% increase in degranulation, a 13.4% increase in ROS generation, and 16.7% additional phagocytosis compared to non-MSC neutrophil (control). Compared to fresh neutrophils isolated the day of testing, MSC-conditioned neutrophils had an average increase in phagocytosis, degranulation, shedding, and ROS generation of 36.9%, 62.7%, 50.3%, and 37.8%, respectively.

Conclusion

MSC increase the functional effector activity of neutrophils in healthy controls, specifically ROS generation, phagocytosis, ectodomain shedding, and degranulation in response to C. albicans. These data raise the possibility of MSC as a novel therapeutic intervention for patients with invasive infections.

Disclosures

Michael Mansour, MD, PhD, Thermofisher: Grant/Research Support
271. Epidemiology of ESBL Klebsiella pneumoniae Clonal Group 307 in Stony Brook, NY
Authors: Glicksberg Jessica , Sajib Monirul I , Sankaran Sanjana , Lindner Marissa , Mui Jonathan , Boniche-Alfaro Camila , Fries Bettina F
Published: November 2023

Background

According to the most recent CDC threat report infections caused by ESBL and carbapenem-resistant Klebsiella pneumoniae (CRKp) remain a persistent challenge. In the US dissemination of CRKp has been largely attributed to clonal group (CG) 258 with recent evidence that CG307, a dominant Klebsiella Extended Spectrum Beta-Lactamase (ESBL-Kp) clone is also emerging as CRKp. CG307 strains uniformly express a wzi-173 type capsular polysaccharide (CPS) whereas other Klebsiella strains including those of the CG258 express a wide variety of wzi-type CPS.

A paper from Houston, TX provided evidence of divergent evolution between CG258 and CG307. CG258 evolves upfront as carbapenem resistant whereas CG307 may initially emerge as ESBL. CR-Kp that belong to the CG307 have also been identified in SBU. Our objective was to determine if among ESBL-Kp CG307 is a common clone and to characterize the demographics of the infected patient population.

Methods

Molecular typing of the wzi gene alleles of 78 sequentially collected ESBL-Kp was performed. Demographic, microbiological and clinical data were extracted from the medical record.

Results

Wzi typing indicated that 43% of ESBLKp strains express a wzi173 type CPS indicating they belong to CG307 the remainder of ESBL strains expressed variable wzi-types. Preliminary data analysis showed that wzi173 expressing ESBL strains were predominantly derived from urine. The median age of patients was 64 years old with male predominance (60.8% males). The average length of stay is 41.6 days. Among these patients, 30.4% required ICU admission. Sepsis criteria were met in 56.5% of these patients within 2 days of positive culture. The mortality rate was 21.7%.

Conclusion

Our data provides evidence that CG307 is the most dominant ESBL Kp clone in hospitalized patients at Stony Brook University. Although the majority of cultures were from urinary source, ICU admission rates and mortality rates were also elevated. These data raise concern that high prevalence of ESBL CG307 in hospitalized patients may ultimately lead to emergence of carbapenem resistant CG307 strains especially if they emerge in patients who are treated with broad spectrum antibiotics.

Disclosures

All Authors: No reported disclosures
274. Potential HIV vaccine gp41 epitope targeting antibodies identify peptides with similarity to proposed Kawasaki disease related peptide, suggesting non-specific mimotope targeting of acidic amino acid enriched regions
Authors: Hakimuddin Sojar , Baron Sarah , Hicar Mark D
Published: November 2023

Background

We have previously isolated a highly mutated (83% homologous to predicted heavy chain germline) antibody (Ab) termed C group 76-Q13-6F5 (6F5) that targets a conformational epitope on gp41. 6F5, though non-neutralizing, has the capacity to mediate Ab dependent cell cytotoxicity (ADCC). When the variable chain (predicted to be VH1-02 derived) was mutated to germline (termed C group 76 ancestor, or 76Canc), surprisingly this Ab still exhibited significant ADCC activity. Many HIV vaccine strategies are focused on raising highly mutated Abs. We propose that there would be an advantage to developing vaccines related to epitopes that permit functional targeting by Abs using germline variable gene sequences.

Methods

To explore potential protein targets for vaccination strategies to raise and develop such Abs, we interrogated a peptide array of 29,127 linear peptides using PEPperCHIP® Human Epitome Microarray. We then confirmed peptide binding by Western blot and ELISAs. We also assessed binding to CDI laboratories HuProt protein microarray, containing > 21,000 human proteins.

Results

76Canc specifically recognized a number of peptides enriched for glutamic and aspartic acid residues (top hit DEEEEYDEDEYEYDE). Meme analysis of positive peptides revealed a peptide sequence most similar to Hepatitis C virus, similar to a peptide implicated in Kawasaki disease (KD). We confirmed specific binding of four of the top peptide hits, including hepatitis C peptide recognition. We then confirmed binding of 76Canc-related Abs to a published optimized KD related peptide (KPAVIPDREALYQDIDEMEEC). Serum from KD and infectious controls was used to compete with biotinylated 76Canc-related Abs. Serum Abs targeting this epitope showed no specific correlation to having KD. Autoantigen screening of 76Canc identified a single human protein of interest that did contain acidic amino acid rich regions.Figure 1:HIV-1 gp41 antibodies recognize peptides similar to peptide implicated in Kawasaki Disease

Conclusion

This study reveals acidic motif targeting by specific anti-gp41 Abs and the derived germline Ab, but no evidence that these Abs are related to inflammation similar to KD. Cautious development of targeting such Abs by vaccination is warranted. Future structural comparison of these peptides with native proteins and binding competition studies are needed to confirm mimotope binding.

Disclosures

Mark D. Hicar, MD/PhD, Pfizer: site investigator for 2 trial
277. A Functional OMICs Evaluation of Omadacycline to Understand Anti-Clostridioides difficile Protective Effects
Authors: Jo Jinhee , Agyapong Samantha , Hu Chenlin , Wang Weiqun , Gonzales-Luna Anne J , Lancaster Chris , Garey Kevin W
Published: November 2023

Background

Omadacycline is an aminomethylcycline tetracycline with potent in vitro activity against C. difficile (CD) and a low propensity for CD infection (CDI) in clinical trials. In addition to potent in vitro activity, ideal properties of anti-CDI antibiotics include favorable effects on bile acids and short-chain fatty acids (SCFA). The aim of this study was to compare bile acid and SCFA changes in healthy volunteers given oral omadacycline versus vancomycin.

Methods

This was a phase 1 healthy volunteer study in 16 adults randomized to an oral 10-day course of either omadacycline or vancomycin. Stool samples were collected daily with metagenomics performed targeting the V4 region of the 16S ribosomal RNA gene using the Miseq platform (Illumina). Stool samples collected at baseline, during therapy, and follow-up visits were used for this functional omics evaluation. Targeted bile acids and SCFA quantification were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The final concentration of each gut metabolome was normalized by the corresponding stool sample weight.

Results

Both antibiotic groups showed a significant decrease in alpha diversity during therapy. Primary bile acids increased in vancomycin-treated subjects which was not observed in the omadacycline group although secondary bile acids diminished equally. Fecal SCFA concentrations of butyrate decreased in both groups while acetate and propionate were preserved in the omadacycline group compared to vancomycin.

Conclusion

Both omadacycline and vancomycin demonstrated changes in the gut microbiome with omadacycline showing favorable effects on bile acids and SCFA. These results provide mechanistic understandings on the anti-CDI properties of omadacycline.

Disclosures

Anne J. Gonzales-Luna, PharmD, BCIDP, Cidara Therapeutics: Grant/Research Support|Ferring Pharmaceuticals: Personal Fees|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support Kevin W. Garey, MS;PharmD, Paratek Pharmaceuticals: Grant/Research Support
281. Mathematical modeling of corticosteroid induced secondary infection and In silico Dose exploration of Dexamethasone, Hydrocortisone
Authors: Kim Dong-Hyun , Kyuong Chung Eun
Published: November 2023

Background

The use of steroids in infected patients is necessary to modulate the inflammatory response that is triggered by infection. However, there is a concern that steroid use could increase the risk of secondary infection. Here, To quantitatively and mechanistically evaluate the risk of secondary infection, we simulate different types and doses of steroids by utilizing a state-of-the-art hybrid PBPK-QSP modeling approach.

Methods

A minimal PBPK model of vancomycin and dexamethasone/hydrocortisone was developed and combined with a mathematical QSP model of bacterial infection and immune response. The models were linked to each other in R 4.2.2 using the rxode2 package. Usual dosing regimen of vancomycin and steroids were simulated, and long-term use of high-dose steroid therapy with vancomycin was also simulated. Vancomycin dosing was fixed at 1500mg IV infusion q12h for 7 days, dexamethasone 5 mg or 70 mg q12h IV infusion for 7 days, and hydrocortisone 100 mg or 500 mg q12h IV infusion for 7 days, with 1.2 times of the maintenance dose given as a loading dose. Plasma and lung PK profiles were derived using the minimal PBPK model to be combined seamlessly with the QSP model. Model-based simulations were conducted over a period of 1000 hours.

Results

Our minimal PBPK model simulated the PK profiles of vancomycin as well as dexamethasone and hydrocortisone in plasma and lung within the physiologically plausible range (Figure 1). In the case of dexamethasone 70 mg, the number of neutrophils decreased by about half compared to the case of dexamethasone 5 mg, and the number of bacteria in the lung compartment substantially increased (13.6% of the initial inoculum) after 300 hours (Figure 2). The other regimens did not show a significant increase in the number of bacteria.

Figure 1. The Plasma and PK profiles of Dexamethasone, Hydrocortisone and Vancomycin by using PBPK models. Figure 2. In silico simulation results of Bacterial infection and immune response during concomitant use of vancomycin and steroids.

Conclusion

Our modeling results suggest that the usual dose of steroid commonly used in infected patients does not increase the risk of secondary infection. However, long-term use of high-dose steroid therapy could increase the risk of secondary infection. When long-term use of high-dose steroid therapy is needed, Hydrocortisone could be a better option than dexamethasone from the perspective of infection risk

Disclosures

All Authors: No reported disclosures
283. Screening the PE/PPE secreted effectors of Mycobacterium tuberculosis to uncover novel virulence-promoting genes
Authors: Koleske Benjamin , Shen Jessica , Gupta Manish , Bishai William
Published: November 2023

Background

Mycobacterium tuberculosis (M.tb) remains the leading cause of infectious disease mortality, with over 10 million active cases and 1.5 million deaths annually at the global scale. Although M.tb infection prompts highly inflammatory granulomatous lesions in the lung, the bacterium is not eradicated by the immune cell infiltrate. Instead, M.tb uses numerous virulence factors to facilitate growth within macrophages, including secretory proteins that subvert host immune processes. In this work, we examined the substrates of ESX-5, a prolific type VII secretion system unique to slow-growing pathogenic mycobacteria, for their roles in contributing to bacterial virulence in a mouse lung infection model. These secretory substrates, the PE and PPE family proteins (named for conserved Pro-Glu and Pro-Pro-Glu domains), have evolutionarily expanded from 11 members in the harmless commensal M. smegmatis to 167 members in the M.tb H37Rv reference strain, suggesting they serve critical functions for an intracellular pathogen with an otherwise reduced genome. Certain PE/PPE genes have been implicated in a broad range of immune relevant functions, including TLR signaling, apoptosis inhibition, and NF-κB activation, though the vast majority remain understudied.

M.tb secretion during infection

(A) Following phagocytosis by a macrophage, M.tb blocks phagosome maturation and permeabilizes the phagosome to secrete effectors into the macrophage cytoplasm. (B) The ESX-5 system secretes a large (> 150) repertoire of PE/PPE proteins predicted to alter host signaling pathways.

Methods

We performed Tn-Seq in the TB mouse model using a pooled library of 81 M.tb strains with single transposon insertions in known PE/PPE genes, all of which show no in vitro growth defect, to identify mutants that demonstrate an in vivo fitness cost.

Results

Bacterial genomes were harvested from the lungs of aerosol-infected BALB/c mice at acute (1 week) and subacute (3 week) timepoints and compared to the composition of the initial pool (day 1). Deep sequencing demonstrated significant decreases in the prevalence of 20 strains over time; furthermore, the findings were highly reproducible across all animals (n=10 per timepoint), showed time-dependent kinetics, and identified several PE/PPE genes previously found to contribute to M.tb pathogenesis.

Conclusion

Our mouse Tn-Seq screen of 81 M.tb PE/PPE mutants identified 20 mutants that were attenuated for growth in mice in a pooled competition format. Thus, a high proportion of PE/PPE genes may be virulence-promoting factors.

Disclosures

All Authors: No reported disclosures
292. Phosphorodiamidate Morpholino Oligomers Targeting acpP Reduce the Biofilm Burden in Burkholderia cepacia Complex
Authors: Mendez Antonio R , Pybus Christine A , Greenberg David E
Published: November 2023

Background

The Burkholderia cepacia complex (Bcc) is composed of highly related opportunistic species that establish pulmonary infections in immunodeficient hosts, such as those with cystic fibrosis and chronic granulomatous disease. Due to their innate antibiotic-resistant phenotypes and capacity to form biofilm, Bcc infections are difficult to eradicate with traditional antibiotics. Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) offer an alternative therapeutic approach. These nucleotide analogues penetrate the outer membrane, bind specific mRNA, and inhibit translation. Due to high affinity base-pairing dynamics, these molecules can be rapidly modified and deployed to precisely inactivate innumerable bacterial gene targets. Previously, we found PPMOs targeting an acyl carrier protein (AcpP) are bactericidal against planktonic Bcc. It remains unknown whether PPMOs could modulate biofilm formation in these pathogens.

Proposed Mechanism of Action of PPMOs

Inside a bacterial cell, peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) targeting the acpP gene bind to mRNA near the Shine-Dalgarno sequence and AUG start site, sterically inhibiting translation. This inhibition disrupts the expression and essential functions of acyl carrier protein (ACP).

Methods

Minimum biofilm eradication concentration assays were used to test two AcpP PPMOs on 24 h biofilms formed on pegs. Viable cells were enumerated. This activity was further evaluated by microscopy and 7-day biofilm kinetic studies. Fluorescein-labeled AcpP PPMO added to B. cenocepacia K56-2 DsRed was imaged over time to evaluate colocalization. PPMO toxicity was assessed over 24 h in A549 cells by LDH release.

Results

Treatment (10-40 μM) with AcpP PPMOs demonstrated more than a 3-log reduction (p< 0.0001) in biofilm burden across five clinical isolates of Bcc tested and B. thailandensis E264. PPMO bactericidal activity was visualized with confocal and scanning electron microscopy. Fluorescently labeled AcpP PPMO associated with the membrane of B. cenocepacia K56-2 DsRed in a temporal fashion. Additionally, AcpP PPMOs exhibited low toxicity in human pneumocytes.

Conclusion

PPMOs are active and bactericidal in established Bcc biofilms; thus, the biofilm setting is not a deterrent against PPMO delivery. This is further supported by the observations that AcpP PPMOs and Bcc cells colocalize in biofilm, resulting in membrane destruction and biomass reduction. Together, these data provide evidence that PPMOs are active in the biofilm setting of Bcc and could be a promising therapeutic strategy for these infections.

Disclosures

David E. Greenberg, MD, University of Texas Southwestern Medical Center: Dr. Greenberg has numerous patents on PPMOs
293. Faecal microbiota transplant to ERadicate gastrointestinal carriage of Antibiotic Resistant Organism: a prospective, randomised placebo-controlled feasibility trial - The FERARO study (IRCTN reg. no. 34467677)
Authors: Merrick Blair , Prossomariti Désirée , Kertanegara Michael , Allen Elizabeth , Sergaki Chrysi , Le Guennec Adrien D , Delord Marc , Conte Maria R , Moyes David , Shankar-Hari Manu , Douiri Abdel , Goodman Anna L , Shawcross Debbie L , Goldenberg Simon D
Published: November 2023

Background

The gastrointestinal tract (GIT) is a reservoir of antibiotic resistant organisms (ARO). ARO colonisation precedes infections which are more challenging to treat than if drug susceptible, with excess morbidity and mortality. Presently, no effective GI decolonisation strategy exists. Faecal microbiota transplant (FMT) has emerged as a potential therapeutic. However, there is uncertainty about feasibility, safety and effectiveness.

Methods

Population: Patients with history of invasive infection with extended spectrum beta-lactamase (ESBL) or carbapenemase producing Enterobacterales (CPE) and evidence of persistent GIT ARO carriage (assessed by culture)

Intervention

3 doses of encapsulated lyophilised FMT each manufactured from 80g raw stool given on consecutive days

Comparator

Matched placebo capsules

Outcomes

Primary outcome - participant consent rate (as proportion of those approached screened for GIT carriage of ESBL-E/CPE). Secondary outcomes – safety and efficacy metrics including adverse event (AE) rates and GIT ARO carriage rates at 1 week, 1, 3 and 6 months. Exploratory outcomes – metagenomic and metabolomic stool analyses.

Results

Of 460 approached individuals, 124 (27%) consented. 53/124 participants (43%) fulfilled eligibility criteria. 44/53 (83%) randomised and 41/44 (93%) received investigational medicinal product (IMP): 20 FMT and 21 placebo. 39/41 (95%) completed dosing, 18/20 (90%) FMT (1 investigator and 1 participant discontinuation) and 21/21 (100%) placebo. Overall, GIT AE including reflux, bloating, change in bowel habit, were more common in FMT arm. 6 serious AE in 5 participants occurred in FMT arm, compared to 1 in placebo (all hospitalisation); none were deemed attributable to FMT. No unanticipated harms from FMT administration were realised. GIT ARO carriage rate assessed in 38/41 (93%) IMP recipients providing stool for analysis at 1-month was lower in FMT compared to placebo - FMT: 13/18 (72%) vs. placebo: 17/20 (85%), p=0.34.

FERARO trial consort diagram

ESBL/CPE detection rate

Detected by culture over time

Conclusion

Based on a priori assessment, a substantive trial would be feasible with protocol modifications. Encapsulated FMT appears safe intervention for eradication of GIT ARO carriage. Our feasibility trial informs design, and provides evidence to conduct future efficacy randomised controlled trials.

Disclosures

David Moyes, PhD, MSc, BSc, Pfizer: Grant/Research Support Simon D. Goldenberg, FRCPath, MD (Res), PGDipID, DipHIC, MSc, EnteroBiotix: Honoraria|Tillotts Pharma UK: Honoraria
294. The Impact of Mucositis on the Oral Microbiome and Clinical Outcomes in Allogenic Hematopoietic Stem Cell Transplantation
Authors: Messina Julia A , Jiang Danting , Selvan Bharathi , Hill Lauren , Bush Amy , Bokman John , Andermann Tessa , Johnson Ernya , Chao Nelson , Surana Neeraj , Sung Anthony
Published: November 2023

Background

Mucositis is a common complication of allogeneic hematopoietic stem cell transplantation (allo HCT) that can lead to debilitating pain, malnutrition, and bloodstream infections (BSI). We sought to characterize the oral microbiome of allo HCT recipients and correlate the oral microbiome with the development of mucositis and clinical outcomes.

Methods

We collected weekly oral swabs and clinical data from patients who underwent allo HCT from 2017-21. Swabs underwent 16S rRNA sequencing, amplifying the V4 region. Patients with paired pre-HCT (prior to conditioning) and day +30 samples were included in the microbiome analysis.

Results

91 patients were enrolled with 178 swabs sequenced. Mucositis occurred in 66/91 patients (73%) at a median 6 days post-HCT (Table 1). Patients with mucositis were significantly more likely to receive myeloablative conditioning, methotrexate/calcineurin inhibitor for graft-versus host disease (GVHD) prophylaxis, and total parenteral nutrition. There was not a significant difference in BSI rates at day +30 between patients with mucositis and those without (20% vs. 17%; p=0.69), but there was a trend toward more acute GVHD by day +30 in the mucositis group (27% vs. 12%; p=0.12). Additionally, patients with mucositis had lower rates of relapse (18% vs. 36%; p=0.07) and all-cause mortality at 1-year post-HCT (26% vs. 36%; p=0.33) although these comparisons were not statistically significant.

39 patients had paired 16S pre- and Day +30 data (28 with mucositis, 11 without). While there was no change in α-diversity in patients who did not develop mucositis, the development of mucositis was associated with a decrease in α-diversity (Figure 1). Although β-diversity of the pre-HCT samples was not different between the two groups, patients with mucositis had a lower pre-HCT abundance of Veillonella parvula.

Conclusion

Post-HCT mucositis led to a reduction in day +30 microbiota diversity, with Veillonella parvula potentially being a biomarker for the development of mucositis. Mucositis was not associated with more BSIs or higher 1-year mortality. Future study includes analysis of the gut microbiome in this same cohort to identify microbial targets that attenuate mucositis without impacting the therapeutic efficacy of HCT.

Disclosures

Neeraj Surana, MD, PhD, Pfizer: Stocks/Bonds Anthony Sung, MD, clasado: Grant/Research Support|dsm: Grant/Research Support|merck: Grant/Research Support