bluuebunny/crossref_metadata_2025 huggingface dataset:
2815. Outcomes of Novel Antimicrobials Compared to Polymyxin B for treatment of infections due Carbapenem-Resistant Enterobacterales Infections
Authors: Zheng Tina , Kubin Christine J , Nelson Brian
Published: November 2023

Background

Carbapenem-resistant Gram-negative infections remain a serious threat due to their increasing incidence and high mortality rates. Since 2015, various antimicrobials with in vitro activity against carbapenem-resistant Enterobacterales (CRE) have been approved for use. There is limited evidence on the safety and efficacy of these novel antimicrobials compared to previous first-line agents, polymyxins, for treating CRE infections.

Methods

This was a retrospective cohort study that evaluated the clinical efficacy and safety of the novel antimicrobials compared to polymyxin B. Adult patients with a CRE infection treated with ceftazidime-avibactam (CZA), meropenem-vaborbactam (MVB), or polymyxin B (PMB) for at least 2 days between June 2013 to November 2022 were included. Patients receiving the novel agents (CZA+MVB) were compared to PMB. The primary outcome was 30-day mortality. Secondary outcomes included clinical and microbiological success, 90-day recurrence, development of resistance, frequency of acute kidney injury (AKI), and global success. Global success encompassed 30-day mortality, clinical and microbiological success, and 90-day recurrence.

Results

110 patients were included: 75 in the novel agents group (53 CZA, 22 MVB) and 35 in the PMB group. The median age was 59 years (IQR 45,70), simplified Pitt bacteremia score (qPITT) was 1 (IQR 1,2), and Charlson Comorbidity score was 4 (IQR 2,6). The most common organism was K. pneumoniae (62%) and the most common site of infection was respiratory (54%) followed by blood (22%). 30-day mortality did not differ between the novel agents compared to PMB (23% vs. 29%; p=0.665). Numerically higher clinical success occurred with the novel agents (72% vs. 54%; p=0.106) while microbiological success was similar (93% vs 91%; p=1.0). In the 18 patients who had follow up positive cultures, 3/9 (33%) developed resistance in the novel agents group compared to 7/9 (78%) in the PMB group. No differences were identified in 90-day recurrence and global success. Patients who received novel agents had less AKI compared to the novel agents (16% vs 54%; p< 0.001).

Conclusion

Patients receiving CZA and MVB for CRE infections did not have differences in clinical and microbiological outcomes but had less AKI compared to patients receiving PMB.

Disclosures

All Authors: No reported disclosures
2823. In Vitro Efficacy of Minocycline on Clinical Gram Negative Bacterial Isolates
Authors: Saleh Omar M Abu , Crowley Patrick , Ranganath Nischal , Challener Douglas , Streck Nicholas
Published: November 2023

Background

Urinary tract infections (UTIs) caused by multidrug-resistant Gram-negative bacilli (MDR-GNB) have become increasingly challenging to manage due to the limited number of available effective oral agents. Minocycline, a second-generation tetracycline with a broad antimicrobial spectrum and reasonable urinary concentration, has recently gained attention as a potential treatment option for MDR-GNB UTIs. In this study, we aim to review the in vitro minocycline susceptibility against a wide spectrum of urinary GNB isolates performed at our reference lab.

Methods

We conducted a retrospective review of all minocycline susceptibility testing performed on urinary GNB isolates performed at the Mayo Clinic reference lab between 2013-2022. We stratified our results for different species based on phenotypic resistance profiles as well as known species-specific resistance association.

Results

During the study timeframe, we identified 28,388 GNB isolates that underwent minocycline susceptibility testing. Among the Escherichia coli (E.Coli) isolates resistant to ceftriaxone, ciprofloxacin, or meropenem, minocycline susceptibility was noted to be 78%, 46%, 76%, respectively (Fig 1). Among the Klebsiella pneumonia (KP) isolate resistant to ceftriaxone, ciprofloxacin, or meropenem, minocycline susceptibilities were 47%, 40%, and 53% respectively (Fig 1). Among the high risk Amp-C group Citrobacter freundii, Enterobacter Cloacae and Klebsiella aerogenes, minocycline susceptibility rate was noted to be 87%, 77%, and 89%, respectively (Fig 2). Finally, among the isolate group of non-fermenters including Achromobacter spp, Acinetobacter spp & Stenotrophomonas spp, susceptibility rates were noted to be 65%, 94%, and 100%, respectively (Fig 3).

Conclusion

Minocycline showed in vitro activity against many hard to treat GNB urinary isolates, including ceftriaxone and meropenem resistant E.coli & KP isolates. High-risk Amp-C producing GN species & some of the less common GN including Stenotrophomonas, Acinetobacter, and Achromobacter.

Disclosures

All Authors: No reported disclosures
2824. 3rd Generation Cephalosporin (3rd CEP) Use and Antibiotic Selection Appropriateness for Uncomplicated Febrile Urinary Tract Infections (UTI) in Children
Authors: Dantas Marina , Eckard Allison Ross , Williams Daniel C , Morrisette Taylor , Thacker Stephen A , Pudalov Natalie , Teufel Ronald J
Published: November 2023

Background

Concerns regarding antibiotic resistance have led many pediatricians to rely on 3rd CEP, namely ceftriaxone (CRO) and cefdinir (CDR), for UTI treatment. 3rd CEP use is a major risk factor for C. difficile infections and contribute to multidrug resistance. We sought to examine local prescribing patterns for uncomplicated febrile UTI in children to guide development of a standardized treatment pathway aimed at reducing unnecessary 3rd CEP use.

Methods

We conducted chart review of children aged 2 mo.-18 yrs treated at our institution for uncomplicated febrile UTI between Oct 2021 – Oct 2022. Subjects were identified by abnormal urine culture (UCx) regardless of colony-forming units (CFU) and included if they met a priori definition. Antibiotic selections were evaluated relative to urinalysis (UA), UCx, and bacterial susceptibilities to assess appropriateness of treatment. This project was certified by our institutional review board as quality improvement.

Results

61 subjects were included (85% female; 3.8 yrs median age; 70%, 16%, 13% treated in ED only, ED/inpatient, inpatient only, respectively). CRO or CDR were most frequently given as initial in-house treatment (ED or inpatient) (Fig 1). 53% of subjects received ≥1 dose of CRO or CDR (ED, inpatient or discharge prescription). 31% of subjects (68% in ED only) were identified as misdiagnosed with UTI (e.g., bacterial growth below CFU threshold or suggestive of contaminant). Providers relied on urine test strips rather than UA/microscopy in 38% of cases misdiagnosed UTIs. Of those with confirmed UTI, E. coli was most common pathogen (81%) followed by other Gram-negative bacteria (14%); susceptibilities were reported in 97% (Fig 2). Initial antibiotic selection was deemed inappropriate in 68% (Fig 3); 39% received CRO/CDR unnecessarily. ≥5 white blood cells per high-power field was most associated with a confirmed UTI (P=0.004).

Conclusion

Inappropriate 3rd CEP use and antibiotic overuse in general were prevalent in our study. The biggest drivers were UA underutilization contributing to UTI misdiagnosis and failure to use UCx to de-escalate antibiotics. Our findings serve as a foundation from which to build a standardized treatment pathway for uncomplicated febrile UTIs that will improve antibiotic stewardship and reduce 3rd CEP use.

Disclosures

Taylor Morrisette, PharmD, MPH, AbbVie: Advisor/Consultant|Basilea: Advisor/Consultant Ronald J. Teufel, II, MD, MSCR, Enanta Pharmaceaticals: Grant/Research Support|Health Resources and Servises Administration: Grant/Research Support|Moderna: Grant/Research Support|National Institute of Health: Grant/Research Support
171. Gram-Positive Blood Culture Contamination Rates: A Comparative Assessment Between Verigene® and Conventional Method
Authors: Almaghlouth Nouf K , Motwani Reena , Guevara Roberto , Khalique Umara , Alrahamneh Hebah , Attia Mohamed , Alrahamneh Osaid A , Allokka Mohamed , Alrahamneh Zaid , Alfarargy Arwa Y , Anyiam Felix
Published: November 2023

Background

The estimated cost of treatment for septicemia among hospitalized patients is $15.4 billion. Approximately 20%-50% of all positive blood cultures were likely false positives. The rates of the reported contaminations in the literature range from 0.6%-12.5%. The false positive report of bacteremia has significantly impacted overall healthcare by increasing mortality rates, prolonging hospital stays, and expanding the cost of care. The use of Verigene® offers polymerase chain reaction (PCR) amplification in < 5 minutes. In our study, we examine the Verigene®, compared to the standard blood culture by the Vitek-2®, to assess for detecting Gram-positive blood contamination (GPBC).

Methods

Blood cultures were collected from patients with sepsis in four hospitals in El Paso, Texas (1/1/2018-5/30/2022). Samples were run through Verigene®. Simultaneously, all specimens were cultured using the conventional method and then incubated for five days. Gram stain used for positive samples. Speciation and antimicrobial susceptibility using Vitek-2®. GPBC in Vitek-2® was identified when one set of two grows microorganisms, universally known as skin flora, without clinical sepsis within 48hr. GPBC in Verigene® was identified when it recognized any skin flora without clinical sepsis within 24hr. The analysis was made using McNemar’s Chi-square test. An observation was statistically significant if the p-value was ≤0.05.

Results

A total of 816 Gram-positive results were obtained. The prevalence of GPBC based on the traditional technique was 98.65% and 64.25% based on the Verigene®. Staphylococcus epidermidis was the most detected at 52%, followed by Staphylococcus aureus at 26%. The sensitivity of the Verigene® for GPBC detection was 64.22%, and the specificity was 33.33%.Figure 1.Frequency of Gram-positive Microorganisms DetectionFigure 2.Sensitivity and Specificity of Verigene® in Identification of Contamination in Gram-positive Blood CultureTable 1.Sensitivity and Specificity of Verigene® in Identification of Contamination in Gram-positive Blood Culture

Conclusion

The use of Verigene® alone in identifying GPBC is insufficient. Despite the higher sensitivity in detecting microorganisms compared to Vitek-2®, this should be paired with clinical judgment and conventional methods. The ability to recognize GPBC by Verigene® was affected by the lack of clinical evidence to exclude sepsis in the first 24hr. This study is the first to evaluate Verigene® for identifying GPBC. Further interventions should be introduced, i.e., reporting titer by PCR on any detection.

Disclosures

All Authors: No reported disclosures
2845. Two Times versus Four Times Daily Cephalexin Dosing for the Treatment of Uncomplicated Urinary Tract Infection in Females
Authors: Yetsko Aidan , Eid Kristen , Draper Heather , Jameson Andrew , Dumkow Lisa E
Published: November 2023

Background

The current IDSA treatment guidelines recommend beta-lactam antibiotics as an alternative, rather than first-line agents, for the treatment of uncomplicated UTI (uUTI). Changing susceptibilities over the past decade, however, have resulted in the need to rely on oral cephalosporins for uUTI. Cephalexin is a commonly prescribed oral first-generation cephalosporin with excellent bioavailability and urinary penetration; however, little data exist to support optimal dosing for uUTI, with pharmacokinetic data supporting twice daily dosing, but common drug databases recommending four times daily dosing.

Methods

This retrospective, multicenter, cohort study included adult female patients treated at Trinity Health Michigan ambulatory sites who received cephalexin for symptomatic uUTI with cefazolin-susceptible urine cultures between February 1, 2020, and August 31, 2022. The primary objective was to compare uUTI treatment failure between patients treated with cephalexin 500 mg twice daily (BID Tx) versus 500 mg four times daily (QID Tx) in the outpatient setting. Treatment failure was defined as the combined endpoint of continued symptoms or necessitation of new therapy while on the initially prescribed 5-7 day course of treatment or recurrent UTI within 30 days of initial therapy. Secondary outcomes included reported adverse events within 7 days of treatment and occurrence of C. difficile within 30 days of treatment. Pregnancy, diagnosis of pyelonephritis or complicated UTI, presence of urinary catheter, history of recurrent UTI, receipt of IV antibiotics, or urine culture not susceptible to cefazolin resulted in exclusion.

Results

A total of 261 patients were included (BID Tx, n= 173; QID Tx, n= 88). There was no difference in treatment failure observed between groups (BID Tx 12.7% vs QID Tx 17%, p=0.343), including failure while on therapy (BID Tx 2.3% vs QID Tx 5.7%, p=0.438) or recurrence within 30 days (BID Tx 10.4% vs QID Tx 11.3%, p=0.438). No differences in reported adverse events (BID Tx 4.6% vs QID Tx 5.7%, p=0.103) or C. difficile within 30 days of treatment (BID Tx 0% vs QID Tx 0%, p=1.0) were observed between groups.

Conclusion

Reduced frequency, 500 mg twice daily, cephalexin is as effective as more frequent, four times daily, dosing for uUTI and may improve patient adherence.

Disclosures

All Authors: No reported disclosures
196. Does Cefepime Provide an Advantage over Ceftriaxone in the Treatment of Bloodstream Infections due to Escherichia coli, Klebsiella pneumoniae group, Klebsiella oxytoca, and Proteus spp. if CTX-M is not Detected by Rapid Molecular Testing?
Authors: Lynn Hammer Katie , Hamm Alyssa , Welch Stephanie N , Smith Jordan R , Ann Medaris Leigh , Boger Michael S , Boger Michael S , Williamson Julie E
Published: November 2023

Background

The BIOFIRE® Blood Culture Identification 2 (BCID2) Panel (bioMérieux) allows for rapid detection of pathogens and antibiotic resistance genes in bloodstream infections (BSIs), including CTX-M, an Extended Spectrum Beta-Lactamase. Atrium Health’s treatment algorithm recommends cefepime (FEP) over ceftriaxone (CRO) for BSI due to non-CTX-M Escherichia coli, Klebsiella pneumoniae group, Klebsiella oxytoca, or Proteus spp. in critically ill patients. It is unclear if use of FEP improves outcomes over CRO in this setting.

Methods

This was a multisite, retrospective cohort study of adults with BSI due to E. coli, K. pneumoniae group, K. oxytoca, and Proteus spp. without CTX-M detected by BCID2 from April 4, 2022 – February 12, 2023. The primary outcome was a composite of in-hospital mortality and length of stay (LOS) more than 14 days in patients who received FEP vs CRO. Secondary outcomes included in-hospital mortality, hospital LOS, intensive care unit (ICU) LOS, rates of mechanical ventilation, and rates of CRO and FEP resistance.

Results

Three hundred patients were enrolled: 150 in each group. Patients in the FEP group were more severely ill at baseline by ICU status and PITT bacteremia score and were less likely to have a urinary source of BSI (Table 1). The composite primary outcome of in-hospital mortality or extended LOS occurred in 54/150 (36%) in the FEP group vs 24/150 (16%) in the CRO group; (p < 0.001). In-hospital mortality, hospital LOS, rates of mechanical ventilation and CRO resistance were higher in the FEP 5/158 (3%) vs. 2/150 (1%) in the CRO group. ICU LOS, in-hospital mortality and rates of FEP resistance were similar (Figures 1 and 2). Of note, of the 7/308 isolates with CRO resistance there was no in-hospital mortality or extended LOS in the CRO group and 5/7 were Proteus spp. There was no FEP resistance.Table 1.Select Baseline Characteristics

Conclusion

Though CRO resistance was relatively low, it was most common among Proteus spp. Treatment with FEP was not associated with improved clinical or microbiological outcomes overall compared to CRO. These results highlight potential overuse of FEP in BSIs due to E.coli, K. pneumoniae group, or K. oxytoca and may have implications on the selection of empiric therapy.

Disclosures

All Authors: No reported disclosures
218. Development of a Simple Score for Diagnosis Melioidosis
Authors: Khaejawat Kanjana , Panichote Anupol , Meesing Atibordee
Published: November 2023

Background

Melioidosis is a common gram-negative bacterial infection in northeastern Thailand. Patients with melioidosis infections often experience severe conditions and high mortality rates. This study aims to develop a clinical prediction model to estimate the risk of melioidosis septicemia.

Methods

This retrospective case-control study included patients with positive hemoculture for Burkholderia pseudomallei (BP) and other gram-negative bacteria (Escherichia coli, and Klebsiella pneumoniae) admitted to Srinagarind Hospital between January 2015 and December 2020. Logistic regression analyses were used to determine the calculation of a score for diagnosing melioidosis infection.

Results

A total of 426 patients with positive hemoculture were included: 132 patients for BP and 294 patients for other gram-negative bacteria. The clinical prediction model for diagnosing melioidosis utilized seven variables: age ≥ 60 years (-2 points), male gender (3 points), duration of symptom onset to hospitalization ≥ 7 days (5 points), occupation as a farmer (3 points), presence of diabetes mellitus (2 points), presence of cancer (-5 points), and platelet count (x 109/L) (200-399.9: 1 point, ≥400: 3 points). The model demonstrated good discrimination (area under the curve: 0.89; 95% CI: 0.86-0.93) and acceptable calibration (Hosmer and Lemeshow goodness of fit test: P-value of 0.252). A cut-off point of the melioidosis score ≥ 5 points (maximum score = 16 and minimum score = -7) resulted in an accuracy of 84.3% (95%CI 80.5-87.6), a sensitivity of 78.8%, and a specificity of 86.7%.

Conclusion

The melioidosis score exhibited high performance and clinical utility in predicting melioidosis infection.

Disclosures

All Authors: No reported disclosures
248. Evaluation of Continuous versus Intermittent Infusion of Nafcillin in the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteremia
Authors: Williamson Julie E , Wood Sarah , Carlson Travis J , Jaffa Rupal K , Boger Michael S , Boger Michael S
Published: November 2023

Background

Anti-Staphylococcal penicillins (ASPCN) are first-line agents in the treatment of methicillin-susceptible Staphylococcus aureus bacteremia (MSSA-B), and continuous infusion (CI) of oxacillin was associated with higher rates of 30-day microbiological cure versus intermittent (II) in infective endocarditis. Nafcillin (NAF) is the formulary ASPCN at Atrium Health (AH) and is variably ordered as CI or II. The purpose of this study is to compare NAF infusion strategies and related outcomes in the treatment of MSSA-B.

Methods

This was a retrospective, observational, multisite study at 15 sites in the Greater Charlotte, NC Region of AH. Hospitalized adults with MSSA-B who received NAF from 1/1/2020 – 3/31/2022 were included. The primary outcome was receipt of CI vs II NAF. Secondary outcomes included time to microbiological cure (TTMIC), in-hospital 30-day all-cause mortality, hospital length of stay (LOS), and rates of adverse drug events (ADE) - acute kidney injury (serum creatinine increase at least 1.5 times baseline), transaminitis (aspartate aminotransferase / alanine transaminase ≥ 5 times the upper limit of normal), hypokalemia (potassium of ≤ 2.9 mmol/L), and allergic reaction. TTMIC, in-hospital mortality, LOS, and ADEs were also evaluated in a cohort of patients in the ICU within 48 hours of NAF start.

Results

A total of 166 patients were included: 99 (59.6%) in the CI group and 67 (40.4%) in the II group. Thirteen patients in the II group were eventually changed to CI, but their results were analyzed in the II group. TTMIC was not significantly different between the CI and II group (5 vs 4 days, respectively p = 0.56), with similar time to receipt of NAF in both groups (Figure 1). In-hospital mortality, hospital LOS, and rates of ADE also did not differ between groups (Figure 1). Forty-seven patients were included in the ICU cohort: 29 in the CI group and 18 in the II group. Trends observed in the ICU cohort were similar to those observed in the larger population (Figure 2).Table 1.Selected Baseline Characteristics

Figure 1

Figure 2

Conclusion

In a small, unmatched, observational cohort of patients with MSSA-B, outcomes were not different based on NAF administration route. This suggests that administration strategy should be determined based on patient specific factors, such as available lines and patient convenience.

Disclosures

All Authors: No reported disclosures
253. Detecting Vancomycin-Resistant Enterococcus (VRE) Gut Colonization in Medical Intensive Care Unit (MICU) Patients: Comparing Culture and Metagenomics
Authors: Bassis Christine , Sansom Sarah E , Schoeny Michael , Thotapalli Lahari , Fukuda Christine , Dangana Thelma E , Pirani Ali , Snitkin Evan , Young Vincent B , Hayden Mary K
Published: November 2023

Background

Investigation of the colonization dynamics of vancomycin resistant Enterococcus faecium (VRE) depends on reliable detection methods. In this study we investigated if metagenomic sequencing enhances our understanding of VRE gut colonization in addition to selective culture.

Methods

We performed metagenomic sequence analysis on 48 stool and rectal swab samples from 15 medical intensive care unit (MICU) patients with dynamic VRE colonization patterns by selective culture. After metagenomic sequences were quality-filtered, trimmed and human sequences were removed, the antimicrobial resistance (AMR) genes were identified using AMR++ v3.0 and the AMR database MEGARes v3.0.

Results

Microbial sequencing depth varied between samples due to low total DNA and varied percentage of human DNA (median: 68.6%; IQR: 55.9-90.5%). We obtained a median of 1.4 million microbial sequence reads/sample (IQR: 0.6 - 6.0 million). Vancomycin resistance gene cluster sequences (Van-type genes) were detected in the metagenomes of 14 samples. There was agreement between VRE-status as by selective culture and detection of Van-type gene sequence in 33/48 samples. 12 samples that were VRE positive by culture did not have Van-type genes detected in the metagenome, possibly due to lower microbial sequencing depth (median: 1 million sequences/sample; IQR: 0.6 - 4.6 million) compared to samples with Van-type genes detected (median: 10.9 million reads/sample; IQR: 1.6 - 29.7 million).

Three VRE culture-negative samples had Van-type genes detected. 2 of these contained the same Van-type genes found in other samples from the same subject, suggesting that they represent actual VRE colonization. In another patient, 2 VRE culture-positive samples collected 15 days apart had the same 11 VanA-type gene sequences, suggesting the same VRE strain was present in both samples.

Conclusion

Metagenomic detection of VRE was influenced by microbial sequencing depth, which is related to total sequencing depth and percentage of host reads. Greater sequencing depth may improve sensitivity of metagenomics to detect resistant organisms. Longitudinal analysis of antimicrobial resistance gene sequences from metagenomes has the potential to provide insight on colonization dynamics.

Disclosures

Vincent B. Young, MD, PhD, ASM: Senior Editor for mSphere Journal|Debiopharm: Consultant|mSphere: Senior Editor|Vendanta Biosciences: Consultant
254. Genomic diversity of Gram-negative Bacilli from Bloodstream Infections in Hospitalized Children
Authors: Blumenthal Jennifer , Conwill Arolyn , McGann Patrick , Sandora Thomas J , Lieberman Tami , Priebe Gregory P
Published: November 2023

Background

Gram-negative bloodstream infection (BSI) in hospitalized children is associated with significant morbidity and mortality. It is unclear whether bacterial clonality of isolates during BSI in a unique patient is associated with clinical characteristics such as immunocompromise. We hypothesized that genomic diversity of BSI isolates would be higher in immunocompromised patients due to mucosal barrier injury and therefore larger translocation bottleneck.

Methods

We prospectively enrolled patients with a central venous catheter who were hospitalized at Boston Children’s Hospital and had a positive blood culture that grew E. coli, Klebsiella spp., or Pseudomonas aeruginosa. An aliquot from the blood culture bottle was plated on agar, and at least 24 colonies were picked randomly and subjected to whole-genome sequencing (WGS). Patient-specific reference genomes were constructed using long-read sequencing of at least 1 isolate on the PacBio platform. All isolates were sequenced using Illumina (MiSeq or NextSeq). Single nucleotide variant (SNV) calls were made using the WideVariant pipeline (github). Clinical characteristics were obtained retrospectively from the electronic medical record. We defined immunocompromise as neutropenia (ANC< 500) on the day of BSI or prior solid organ or stem cell transplant. The proportion of BSI episodes with clonal blood isolates (defined as 0 SNV) was compared between immunocompromised and non-immunocompromised patients using Fisher’s exact test.

Results

We enrolled 34 patients (median age 2.33 years, IQR 0.8-3.8 years), 25 having BSI from Enterobacterales (11 E. coli, 14 Klebsiella spp.) and 9 from Pseudomonas aeruginosa. Immunocompromised patients had a significantly higher proportion of Enterobacterales BSI episodes with clonal isolates compared with non-immunocompromised patients [13/18 (72%) vs. 1/7 (14%) respectively, P=0.021). This was not seen with Pseudomonas BSI, which had clonal isolates in 3/5 (60%) vs. 2/4 (50%) respectively (P=1).

Conclusion

Contrary to our hypothesis, immunocompromised patients were more likely to have clonal Enterobacterales BSI isolates compared with non-immunocompromised patients, perhaps due to lower host pressures for bacterial population diversification in immunocompromised patients.

Disclosures

Arolyn Conwill, PhD, Day Zero Diagnostics: current employee|Day Zero Diagnostics: Stocks/Bonds
272. Dissecting Host-Commensal Interactions During Early Life to Identify Mechanisms of Protection Against Autoimmune Diabetes
Authors: Grimes Logan , Flores Julia , Lubin J B , Green Jamal , Silverman Michael
Published: November 2023

Background

Major Histocompatibility Complex (MHC) and Human Leukocyte Antigen (HLA) loci have strong genetic linkage with type 1 diabetes (T1D) in mice and humans, respectively. The diabetes-prone non-obese diabetic (NOD) strain of mice have a unique MHC-II locus with a distinct MHC-II A molecule (Ag7) and lack expression of the MHC-II E molecule. Expression of this MHC-II A molecule is associated with development of T1D, whereas transgenic restoration of the MHC-II E molecule dominantly protects against T1D. The Silverman laboratory recently demonstrated that MHC-II E molecule expression selects for a diabetes-protective intestinal microbiota in early life though a key knowledge gap remains: how do these two factors — MHC-II molecules and commensal microbiota — work together during a critical early-life period of microbiome and immune system ontogeny to prevent T1D? To address this question, the Silverman laboratory developed a gnotobiotic mouse model by designing a microbial community consisting of 9 intestinal microbes cultured from these diabetes-protected (Ea16/NOD) mice – called “PedsCom”. This gnotobiotic model allows for mechanistic, well-controlled studies of interactions between commensal microbes and the developing immune system.

Methods

We used flow cytometry to sort commensal bacteria from PedsCom-colonized NOD and Ea16/NOD mice into IgA-coated and IgA-uncoated populations. We employed species-specific multiplex qPCR to quantify relative abundance of each PedsCom microbe in these sorted populations.

Results

Two microbes, K. cowanii and L. murinus, were preferentially IgA bound in both NOD and Ea16/NOD mice. L. johnsonii, A. caccae, and S. xylosus were preferentially IgA bound only in the presence of MHC-II E molecule expression. Many of the highly IgA coated microbes (K. cowanii, L. murinus, L, johnsonii, and A. caccae) translocate to the mesenteric lymph nodes.

Conclusion: We propose that MHC-II expression facilitates specific mucosal IgA responses, that MHC-II E expression allows for additional epitope recognition amongst PedsCom members which may potentiate this effect, and that preferential IgA coating may promote contact with mucosa-associated lymphoid tissues as early steps in tolerogenic immune system ontogeny that protects against development of T1D.

Disclosures

All Authors: No reported disclosures
278. Effects of polymyxin B direct hemoperfusion by measurement of outer membrane vesicles in patients with septic shock
Authors: Min Jo Kyeong
Published: November 2023

Background

Sepsis is one of the most common reasons for admission to the intensive care unit, and its incidence continues to increase. However, the precise mechanism of sepsis has not yet been fully elucidated. Outer membrane vesicles (OMVs) present in the outer membrane of bacteria have been speculated to be one of the causes of sepsis. Direct hemoperfusion with polymyxin B-immobilized fiber (PMX-DHP) can be used as a means to remove OMVs. This study evaluated whether the use of PMX-DHP affects bacterial distribution.

Methods

A total of 30 critically ill patients with severe septic shock were enrolled from intensive care unit of Haeundae Paik hospital. Plasma and urine samples were collected before and after the use of PMX-DHP. Sequencing-based metagenome analysis of the microbiome was performed, and changes in the distribution of various bacteria before and after the use of PMX-DHP were identified.

Results

A total of 30 patients were enrolled. Figure 1 shows the changes in the distribution of bacteria in plasma before and after the use of PMX-DHP. The only strain that showed a statistically significant difference in the pre-mean and post-mean values in this distribution was Bradyrhizobium (0.0152 →0.0000, p=0.0255, Figure 2). Figure 3 shows the changes in the distribution of bacteria in urine before and after the use of PMX-DHP. No bacteria showed a statistically significant difference in distribution before and after the use of PMX-DHP in this distribution.

Figure 1

Distribution of bacteria in plasma before and after the use of PMX-DHP

Figure 2

Changes in the distribution of Bradyrhizobium in plasma

Figure 3

Distribution of bacteria in urine before and after the use of PMX-DHP

Conclusion

Bradyrhizobium was the only strain that showed a statistically significant decrease in the amount of outer membrane vesicles (OMVs) in plasma through hemoperfusion using PMX-DHP.

Disclosures

All Authors: No reported disclosures
282. Resistance to caspase-1 dependent pyroptosis of hypervirulent K. pneumoniae
Authors: ah Kim Hyun , Hyun Miri , Lee Jiyeon , Kyung Kim Jin , baek wonki
Published: November 2023

Background

Hypervirulent K. pneumoniae(Hv Kp) has emerged as a clinically significant global pathogen in the last decade. However, the host immune responses of the macrophages during hvKp infection are largely unknown. In the present study, we aimed to compare the cytotoxic effects of hvKp and classical K. pneumoniae (cKp) in murine macrophages.

Methods

Bacterial strains are obtained from clinical samples who infected by K. pneumoniae. The rmpA and iutA positive strains with mucoid phenotype were defined as hypervirulent K. pneumoniae. Raw 264.7 cell and BMDM(bone marrow derived macrophage) cell were used for experiments. Wild-type C57BL/6 female mice and Casp1-/- female mice (age, 7–9 weeks) were used. Cytotoxicity after 4 hours of infection, MTS and LDH release was measured. FACS scan after PI dyed was performed for cell cycle analysis and cytotoxicity each MOI(Multiplicity of infection) concentration. Western blot analysis of caspase-1 and caspase-1 inhibitor were used. IL-1β was tested with ELISA.

Results

We found that the activation of caspase-1 (Casp1)-dependent pyroptosis was higher in cKp-infected macrophages compared with that in hvKp-infected macrophages. In caspase-1 deficiency macrophages, pyroptosis diminished during infection. Both hvKp and cKp strains led to nucleotide-binding and oligomerization domain-like receptor protein 3 (NLRP3) inflammasome formation and lysosomal cathepsin B activation, thus resulting in pyroptosis. Compared with the cKp strain, the hvKp strain inhibited these phenomena in murine macrophages.Figure 1.HvKp and cKp strains induce pyroptotic cell death in the RAW264.7 murine macrophage cell line.Figure 2.BMDMs were differentiated from WT and Casp1-/- mice and infected with the hvKp or cKp strains.

Conclusion

In this study, compared to classical strains, it was confirmed that cells infected with hv Kp survived without apoptosis. HvKp infection resulted in different levels of pyroptosis via the activation of cathepsin B-NLRP3-caspase-1 in murine macrophage. Therefore, the manipulation of pyroptotic cell death is a potential target for host response during hvKp infection in macrophages.

Disclosures

All Authors: No reported disclosures
284. Age-related differences in B-cell response during Clostridioides difficile infection in mice
Authors: Kumar Archit , O’Brien Martin , Nguyen Nhu , Vendrov Kimberly , Bergin Ingrid L , Young Vincent B , Yung Raymond
Published: November 2023

Background

Clostridioides difficile (C. difficile) infection (CDI) is a leading cause of nosocomial infection that can range from mild diarrhea to life threatening pseudomembranous colitis and death. Aging as well as defects in the host immune response including failure to develop antibody response against C. difficile antigens increases the risk of bacterial colonization, hospitalization, mortality and developing recurrent CDI. The present study aimed to investigate the differences in the B cell response between young and aged C. difficile infected mice.

Methods

C57BL/6 mice were rendered susceptible to CDI via the administration of oral cefoperazone for 10 days and then the mice were challenged with 103 spores of C. difficile R20291 strain (Figure 1). The young (3-4 months) and aged (22-24 months) mice were euthanized at 14 days post infection (dpi). The germinal center response and IgA+ antibody-secreting cells (ASCs) were studied using multicolor flow cytometry.

Results

C. difficile infected aged mice exhibited greater weight loss at 4 dpi compared to young C. difficile infected mice. The gut germinal center response studied at 14 dpi showed mild changes in T follicular helper cells (CXCR5+PD-1+ of CD4+) and germinal center B cells (GL7+CD95+ of CD19+B200+) of young C. difficile infected mice, whereas the response was dampened in the aged C. difficile infected mice (Figure 2). Further, at 14 dpi ASCs (CD138+CD98+) were seen in the lamina propria of the cecum and colon of the C. difficile infected mice, but the frequencies of CD138+CD98+ ASCs as well as IgA+ ASCs were significantly lower in the C. difficile infected aged mice compare to young mice (Figure 3).

Conclusion

The defect in B cell response during CDI may be responsible for more severe infection and recurrent CDI among aged individual compared to young individuals. It remains to be seen if age-related changes impact antibody production and whether the antibody production during primary CDI provides long-term immunity.

Disclosures

Vincent B. Young, MD, PhD, ASM: Senior Editor for mSphere Journal|Debiopharm: Consultant|mSphere: Senior Editor|Vendanta Biosciences: Consultant
289. Evaluation of Aztreonam-Avibactam In Vitro Activity Against VIM and GES β-lactamase Producing, Carbapenem-Resistant Pseudomonas aeruginosa Collected from Contaminated Artificial Tear Products
Authors: Lin Lynn-Yao , Debabov Dmitri
Published: November 2023

Background

A rare strain of extensively drug-resistant Pseudomonas aeruginosa was identified from contaminated artificial tear products that caused outbreak across 16 US states in March 2023. The strain carries Verona integron-encoded metallo-β-lactamase (VIM) and Guiana-Extended Spectrum-β-Lactamase (GES), a combination not previously identified in the US. Aztreonam (ATM) is a monobactam that is stable against hydrolysis by MBLs, and avibactam (AVI) inhibits class A, C, and some D β-lactamases. ATM-AVI is currently in development for treatment of infections caused by drug-resistant Gram-negative pathogens, especially those co-producing MBLs and other β-lactamases. This study evaluated in vitro activity of ATM-AVI against VIM and GES producing carbapenem-resistant P. aeruginosa (VIM-GES-CRPA) isolates acquired from CDC AR Bank.

Methods

Three VIM-GES-CRPA clinical isolates acquired from CDC AR Bank were tested for susceptibility to ATM and ATM-AVI (fixed concentration of 4 mg/L AVI) by broth microdilution (BMD). The isolates were tested concurrently by disk diffusion method using ATM-AVI 30-20 µg disks manufactured by BD Biosciences (BD) and Mast Group (Mast), as well as cefiderocol and ATM disks by Hardy diagnostics (Hardy) and by ATM-AVI E-test strips by Liofilchem, Inc. β-lactam/β-lactamase inhibitors (BL/BLI) were tested by BMD. All tests were interpreted using CLSI 2023 breakpoints. Tentative ATM-AVI pharmacokinetic/pharmacodynamic (PK/PD) susceptible MIC breakpoints of ≤ 8 mg/L (BMD, E-test) or ≥ 23 mm (disk diffusion) were applied for comparison purposes.

Results

The MIC values of ATM-AVI by BMD were in the range of 4-8 mg/L and correlated with the values measured by ATM-AVI E-test (3-8 mg/L), demonstrating in vitro activity against VIM-GES-CRPA. ATM-AVI inhibition zone diameters measured by both BD and Mast discs were in the range of 27-28 mm. The isolates were shown to be resistant to ATM alone, ceftazidime/avibactam, ceftolozane/tazobactam and imipenem/relebactam, but susceptible to cefiderocol.

Conclusion

Based on proposed PK/PD breakpoints, all tested isolates of VIM-GES-CRPA were susceptible to ATM-AVI. ATM-AVI demonstrated in vitro activity against these extensively drug-resistant P. aeruginosa isolated from contaminated artificial tear products.

Disclosures

Lynn-Yao Lin, M.S. Molecular Biotechnology, Abbvie Inc: Employee of Abbvie that participated in design, study conduct, financial support, interpretation of data, review, and approval of the publication Dmitri Debabov, PhD. Molecular biology, Abbvie Inc.: Employee of Abbvie that participated in design, study conduct, financial support, interpretation of data, review, and approval of the publication
309. Optimized hematopoietic stem cell source for the ex vivo production of mature human neutrophils as a potential cell-based therapy for neutropenia
Authors: Timmer Kyle D , Floyd Daniel , Jeffries Nathan E , Yvanovich Emma , Sykes David B , Mansour Michael
Published: November 2023

Background

Neutrophils or granulocytes are the most common innate immune cell and are critical for eliminating invasive pathogens. Patients with low neutrophil counts face an increased risk of fatal opportunistic infections. Allogeneic granulocyte transfusions offer a solution to supplement endogenous neutrophil counts but are challenging due to insufficient preservation methods and donation feasibility. Here, we compare the capacity of three different hematopoietic stem cell (HSC) sources; 1) cord blood (CB), 2) live adult bone marrow (LABM), and 3) cadaveric adult bone marrow (CABM), to expand and generate an ex vivo neutrophil source.

Methods

HSCs were expanded ex vivo with or without UM729 then differentiated and evaluated for neutrophil yield and purity. Ex vivo differentiated neutrophils were characterized by flow cytometry for activated phenotype surface markers. Finally, the functional capacity of ex vivo neutrophils, including phagocytosis, ectodomain shedding, and reactive oxygen species (ROS) production, was measured in response to the fungal pathogen Candida albicans.

Results

CB-derived HSCs were found to be superior in expansion capacity compared to LABM- or CABM-derived HSCs by 3-fold at day six. The use of UM729 reduced the purity of neutrophil differentiation by 44% for both live and deceased BM marrow-derived HSCs. UM729 had no observable effect on the purity of neutrophil differentiation for CB-derived HSCs. Additionally, due to enhanced Fc gamma receptor I expression, ex vivo neutrophils from all sources were ten times more sensitive to recognizing IgG-opsonized C. albicans than primary neutrophils. Ex vivo neutrophils were capable of phagocytosis, ROS production, and ectodomain shedding to a similar capacity as primary donor neutrophils.

Conclusion

We find that cadaveric bone marrow-derived HSCs are a viable source for HSC-generated neutrophils. That said, CB-derived HSC were superior in expansion capacity. We also highlight the unique opsonin-activating features of ex vivo generated neutrophils which warrant further study in granulocyte transfusion animal models of systemic infection. These data underscore the significance of neutrophil cellular therapeutics as a novel modality for preventing infection in high-risk neutropenic patients.

Disclosures

Nathan E. Jeffries, BA, Safi Biotherapeutics: Salary Michael Mansour, MD, PhD, Thermofisher: Grant/Research Support
325. Outcomes of Outpatient Parenteral Antimicrobial Therapy in the Solid Organ Transplant Population
Authors: Dillon William P , Muthanna Shadid Al , Parsons Austin , Hardy Megan , Williams Jonathan D , McCorquodale Jennifer , Ramesh Mayur , Alangaden George J
Published: November 2023

Background

Outpatient parenteral antimicrobial therapy (OPAT) provides an effective and convenient means to complete extended courses of antimicrobial therapy for the treatment of serious infections. There is scant data addressing OPAT related outcomes such as readmission in solid organ transplant (SOT) recipients.

Methods

In this observational cohort study, we analyzed all adult SOT recipients discharged from Henry Ford Hospital – an 877 bed quaternary care center in Detroit, Michigan - on OPAT between January 2015 and December 2020. The primary endpoint was 30-day all-cause readmission. The secondary endpoints included evaluation of risk factors associated with readmission (transplant type, reason for OPAT, OPAT related complications, length of treatment, length of stay, discharge disposition, and adequacy of infectious disease follow up and laboratory monitoring) and all-cause mortality at one year.

Results

There were 201 patients discharged on OPAT. Demographics between study populations were comparable (Table 1). A total of 83 out of 201 (41.3%) patients were readmitted. There were 38 (18.9%) patients readmitted for OPAT related complications and 45 (22.4%) for non-OPAT related reasons. Intestinal and multi-visceral transplants were associated with readmission (p=0.04 and p=0.02 respectively) while renal transplants were protective against readmission (p=0.02) (Table 1). Other factors associated with readmission include development of an OPAT related complication including treatment failure (p< 0.001) (Table 2). Patients discharged without Infectious Disease follow up were less likely to be readmitted (p=0.04) (Table 3) as these patients generally had less serious infections not meriting a follow up appointment. There was no difference in mortality at one year between study populations (Table 3).

Conclusion

While the overall readmission rate of SOT discharged on OPAT is high, most readmissions were unrelated to OPAT. Patients with readmissions had higher rates of OPAT related complications and treatment failures. Further studies are warranted to optimize OPAT outcomes in the SOT population.

Disclosures

All Authors: No reported disclosures
327. Use of multiple pharmacies by people living with HIV: a qualitative analysis
Authors: Sahloff Eric G , Duggan Joan
Published: November 2023

Background

Multiple pharmacy use has been linked to decreased patient adherence, inappropriate drug use, adverse drug reactions, and increased mortality. Despite negative outcomes, multi-pharmacy use has increased and nearly half of all patients in the US now use multiple pharmacies. In this study, the attitudes towards multiple pharmacy use (MPU) versus single pharmacy use (SPU) for PLWH (people living with HIV) were assessed.

Methods

A convenience sample of patients in a single midwestern Ryan White clinic was surveyed. There were 24 questions with two additional questions for users of multiple pharmacies. Questions were related to patient demographics, current CD4 count (CD4), viral load (VL) status, amount of time to receive medications, missed doses, comorbidities, and patient preferences. A 5-point Likert Scale (LS; 1 = strongly disagree, 5 = strongly agree) was used to assess reasons for SPU versus MPU, including for MPU if antiretroviral medications were filled separately.

Results

142 patients participated (69 SPUs; 73 MPUs). Few differences between SPUs and MPUs for demographic indicators were identified (Table 1). SPUs were more likely to use private/commercial insurance versus government-sponsored insurance and use fewer non-HIV medications. There was no difference between groups in self-reported undetectable VL. There was a trend towards increased recall of self-reported CD4 and VL status for SPUs vs MPUs. SPUs indicated that proximity (LS weighted average (WA) = 3.64), getting all meds in one place (LS WA = 4.45), and the identification of adverse effects (LS WA = 4.17) and drug-drug interactions (LS WA = 4.06) as reasons for preferring to use a single pharmacy. For MPUs who indicated they used a separate pharmacy specifically for antiretroviral medications, the need to keep HIV status private (LS weighted average = 3.65) was noted as a significant reason.Table 1.Respondents DemographicsTable 1(cont). Respondent Demographics

Conclusion

SPUs chose a single pharmacy for reasons of convenience and safety. MPUs who chose to fill their antiretroviral therapy at a separate pharmacy stated concerns for stigma/privacy as a major contributing factor. Patient preferences should be strongly considered regarding SPU or MPU. Interestingly, MPUs were less likely to be aware of their clinical status.

Disclosures

All Authors: No reported disclosures