Antibacterial activity of ibezapolstat against antimicrobial-resistant clinical strains of Clostridioides difficile

Antimicrobial resistance is emerging in clinical strains of Clostridioides difficile. Ibezapolstat (IBZ) is a DNA polymerase IIIC inhibitor that has completed phase II clinical trials. IBZ has potent in vitro activity against wild-type, susceptible strains but its effect on C. difficile strains with reduced susceptibility to metronidazole (MTZ), vancomycin (VAN), or fidaxomicin (FDX) has not been tested. The primary objective of this study was to test the antibacterial properties of IBZ against multidrug-resistant C. difficile strains. The in vitro activity, bactericidal, and time-kill activity of IBZ versus comparators were evaluated against 100 clinical strains of which 59 had reduced susceptibility to other C. difficile antibiotics. Morphologic changes against a multidrug resistance strain were visualized by light and scanning electron microscopy. The overall IBZ MIC50/90 values (µg/mL) for evaluated C. difficile strains were 4/8, compared with 2/4 for VAN, 0.5/1 for FDX, and 0.25/4 for MTZ. IBZ MIC50/90 values did not differ based on non-susceptibility to antibiotic class or number of classes to which strains were non-susceptible. IBZ bactericidal activity was similar to the minimum inhibitory concentration (MIC) and maintained in wild-type and non-susceptible strains. Time-kill assays against two laboratory wild-type and two clinical non-susceptible strains demonstrated sustained IBZ activity despite reduced killing by comparator antibiotics for IBZ and VAN non-susceptible strains. Microscopy visualized increased cell lengthening and cellular damage in multidrug-resistant strains exposed to IBZ sub-MIC concentrations. This study demonstrated the potent antibacterial activity of IBZ against a large collection of C. difficile strains including multidrug-resistant strains. This study highlights the therapeutic potential of IBZ against multidrug-resistant strains of C. difficile.

Reduced Vancomycin Susceptibility in Clostridioides difficile is Associated with Lower Rates of Initial Cure and Sustained Clinical Response

BACKGROUND

Epidemiologic studies have shown decreasing vancomycin susceptibility among clinical Clostridioides difficile isolates, but the impact on patient outcomes is unknown. We hypothesized that reduced vancomycin susceptibility would be associated with decreased rates of sustained clinical response (SCR).

METHODS

This multicenter cohort study included adults with C. difficile infection (CDI) treated with oral vancomycin between 2016-2021. C. difficile isolates underwent agar dilution vancomycin susceptibility testing, ribotyping, and Sanger sequencing of the vancomycin resistance vanR gene. Reduced susceptibility was defined as vancomycin minimum inhibitory concentration (MIC) >2 μg/mL. The primary outcome was 30-day SCR; secondary outcomes were 14-day initial cure, 30-day recurrence, and 30-day mortality. Exploratory analysis assessed the association between the VanR Thr115Ala polymorphism, susceptibility, and outcomes.

RESULTS

A high proportion (34%, 102/300) of C. difficile isolates exhibited reduced vancomycin susceptibility (range: 0.5-16 μg/mL, MIC50/90 = 2/4 μg/mL). Ribotype (RT) 027 accounted for the highest proportion (77.4%, 41/53) of isolates with reduced vancomycin susceptibility. Overall, 83% (249) of patients achieved 30-day SCR. Reduced vancomycin susceptibility was associated with lower rates of 30-day SCR (76%, 78/102) than vancomycin susceptible strains (86%, 171/198; P=0.031). A significantly lower rate of 14-day initial cure was also observed among individuals infected with strains with reduced vancomycin susceptibility (89% vs. 96%; P=0.04). Reduced susceptibility remained an independent predictor of 30-day SCR in multivariable modeling (odds ratio, 0.52, 95% confidence interval 0.28-0.97; P=0.04).

CONCLUSIONS

Reduced vancomycin susceptibility in C. difficile was associated with decreased odds of 30-day SCR and lower 14-day initial cure rates in the studied patient cohort.

Significant Publications on Infectious Diseases Pharmacotherapy in 2021

Purpose: To summarize the most noteworthy infectious diseases (ID) pharmacotherapy articles published in peer-reviewed literature in 2021. Summary: Members of the Houston Infectious Diseases Network (HIDN) nominated articles that were deemed to have significant contributions to ID pharmacotherapy in 2021. These nominations included articles pertaining to both general ID, including coronavirus disease 2019 (COVID-19), and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) pharmacotherapy. A total of 35 articles were nominated by HIDN: 30 articles pertaining to general ID pharmacotherapy and 5 articles with HIV/AIDS focus. To select the most influential articles of 2021, a survey was created and distributed to members of the Society of Infectious Diseases Pharmacists (SIDP). Of the 239 SIDP members who responded to the survey, there were 192 recorded votes for the top 10 general ID pharmacotherapy articles and 47 recorded votes for the top HIV/AIDS article, respectively. The top publications are summarized. Conclusion: Antimicrobial stewardship and the optimal management of infectious disease states continues to be a priority in the midst of the ongoing coronavirus disease 2019 (COVID-19) global pandemic. In light of the sheer volume of ID-related articles published in the past year, this review aims to aid clinicians in remaining up-to-date on key practice-changing ID pharmacotherapy publications from 2021.

Fecal Pharmacokinetics and Gut Microbiome Effects of Oral Omadacycline Versus Vancomycin in Healthy Volunteers

BACKGROUND

Clostridioides difficile infection (CDI) is a common healthcare-associated infection with limited treatment options. Omadacycline, an aminomethylcycline tetracycline, has potent in vitro activity against C difficile and a low propensity to cause CDI in clinical trials. We aimed to assess fecal pharmacokinetics and gut microbiome effects of oral omadacycline compared to oral vancomycin in healthy adults.

METHODS

This was a phase 1, nonblinded, randomized clinical trial conducted in healthy volunteers aged 18-40 years. Subjects received a 10-day course of omadacycline or vancomycin. Stool samples were collected at baseline, daily during therapy, and at follow-up visits. Omadacycline and vancomycin stool concentrations were assessed, and microbiome changes were compared.

RESULTS

Sixteen healthy volunteers with a mean age of 26 (standard deviation [SD], 5) years were enrolled; 62.5% were male, and participants' mean body mass index was 23.5 (SD, 4.0) kg/m2. Omadacycline was well tolerated with no safety signal differences between the 2 antibiotics. A rapid initial increase in fecal concentrations of omadacycline was observed compared to vancomycin, with maximum concentrations achieved within 48 hours. A significant difference in alpha diversity was observed following therapy in both the omadacycline and vancomycin groups (P < .05). Bacterial abundance and beta diversity analysis showed differing microbiome changes in subjects who received omadacycline versus vancomycin.

CONCLUSIONS

Subjects given omadacycline had high fecal concentrations with a distinct microbiome profile compared to vancomycin.

CLINICAL TRIALS REGISTRATION

NCT06030219.

Review Article: Safety of Live Biotherapeutic Products Used for the Prevention of Clostridioides difficile Infection Recurrence

Live biotherapeutic products (LBPs) represent a new class of therapeutics indicated to prevent the recurrence of Clostridioides difficile infection (CDI) in adults. However, microbiota-based therapies have been used in CDI management before the Food and Drug Administration (FDA) designated this new drug class. The regulation of these microbiome-based therapies has varied, and several safety concerns have arisen over time. Requirements established by the FDA regarding the development of LBPs minimizes many of these prior concerns, and phase III trials have proven the safety and efficacy of 2 stool donor-derived LBPs: fecal microbiota, live-jslm (Rebyota™; formerly RBX2660) and fecal microbiota spores, live-brpk (Vowst™; formerly SER-109). Mild gastrointestinal side effects are common, but no severe drug-related adverse events have been reported with their use to date. A third LBP entering phase III clinical trials, VE303, follows a novel approach by sourcing bacterial strains from clonal cell banks and has demonstrated a similarly favorable safety profile.

The Significance of Bayesian Pharmacokinetics in Dosing for Critically Ill Patients: A Primer for Clinicians Using Vancomycin as an Example

Antibiotic use is becoming increasingly challenging with the emergence of multidrug-resistant organisms. Pharmacokinetic (PK) alterations result from complex pathophysiologic changes in some patient populations, particularly those with critical illness. Therefore, antibiotic dose individualization in such populations is warranted. Recently, there have been advances in dose optimization strategies to improve the utilization of existing antibiotics. Bayesian-based dosing is one of the novel approaches that could help clinicians achieve target concentrations in a greater percentage of their patients earlier during therapy. This review summarizes the advantages and disadvantages of current approaches to antibiotic dosing, with a focus on critically ill patients, and discusses the use of Bayesian methods to optimize vancomycin dosing. The Bayesian method of antibiotic dosing was developed to provide more precise predictions of drug concentrations and target achievement early in therapy. It has benefits such as the incorporation of personalized PK/PD parameters, improved predictive abilities, and improved patient outcomes. Recent vancomycin dosing guidelines emphasize the importance of using the Bayesian method. The Bayesian method is able to achieve appropriate antibiotic dosing prior to the patient reaching the steady state, allowing the patient to receive the right drug at the right dose earlier in therapy.

Baseline stool toxin concentration is associated with risk of recurrence in children with Clostridioides difficile infection

BACKGROUND

In adults with Clostridioides difficile infection (CDI), higher stool concentrations of toxins A and B are associated with severe baseline disease, CDI-attributable severe outcomes, and recurrence. We evaluated whether toxin concentration predicts these presentations in children with CDI.

METHODS

We conducted a prospective cohort study of inpatients aged 2-17 years with CDI who received treatment. Patients were followed for 40 days after diagnosis for severe outcomes (intensive care unit admission, colectomy, or death, categorized as CDI primarily attributable, CDI contributed, or CDI not contributing) and recurrence. Baseline stool toxin A and B concentrations were measured using ultrasensitive single-molecule array assay, and 12 plasma cytokines were measured when blood was available.

RESULTS

We enrolled 187 pediatric patients (median age, 9.6 years). Patients with severe baseline disease by IDSA-SHEA criteria (n = 34) had nonsignificantly higher median stool toxin A+B concentration than those without severe disease (n = 122; 3,217.2 vs 473.3 pg/mL; P = .08). Median toxin A+B concentration was nonsignificantly higher in children with a primarily attributed severe outcome (n = 4) versus no severe outcome (n = 148; 19,472.6 vs 429.1 pg/mL; P = .301). Recurrence occurred in 17 (9.4%) of 180 patients. Baseline toxin A+B concentration was significantly higher in patients with versus without recurrence: 4,398.8 versus 280.8 pg/mL (P = .024). Plasma granulocyte colony-stimulating factor concentration was significantly higher in CDI patients versus non-CDI diarrhea controls: 165.5 versus 28.5 pg/mL (P < .001).

CONCLUSIONS

Higher baseline stool toxin concentrations are present in children with CDI recurrence. Toxin quantification should be included in CDI treatment trials to evaluate its use in severity assessment and outcome prediction.

Decoding a cryptic mechanism of metronidazole resistance among globally disseminated fluoroquinolone-resistant Clostridioides difficile

Severe outbreaks and deaths have been linked to the emergence and global spread of fluoroquinolone-resistant Clostridioides difficile over the past two decades. At the same time, metronidazole, a nitro-containing antibiotic, has shown decreasing clinical efficacy in treating C. difficile infection (CDI). Most metronidazole-resistant C. difficile exhibit an unusual resistance phenotype that can only be detected in susceptibility tests using molecularly intact heme. Here, we describe the mechanism underlying this trait. We find that most metronidazole-resistant C. difficile strains carry a T-to-G mutation (which we term PnimB^G) in the promoter of gene nimB, resulting in constitutive transcription. Silencing or deleting nimB eliminates metronidazole resistance. NimB is related to Nim proteins that are known to confer resistance to nitroimidazoles. We show that NimB is a heme-dependent flavin enzyme that degrades nitroimidazoles to amines lacking antimicrobial activity. Furthermore, occurrence of the PnimB^G mutation is associated with a Thr82Ile substitution in DNA gyrase that confers fluoroquinolone resistance in epidemic strains. Our findings suggest that the pandemic of fluoroquinolone-resistant C. difficile occurring over the past few decades has also been characterized by widespread resistance to metronidazole.

Redefining Clostridioides difficile infection antibiotic response and clinical outcomes

With the approval and development of narrow-spectrum antibiotics for the treatment of Clostridioides difficile infection (CDI), the primary endpoint for treatment success of CDI antibiotic treatment trials has shifted from treatment response at end of therapy to sustained response 30 days after completed therapy. The current definition of a successful response to treatment (three or fewer unformed bowel movements [UBMs] per day for 1-2 days) has not been validated, does not reflect CDI management, and could impair assessments for successful treatment at 30 days. We propose new definitions to optimise trial design to assess sustained response. Primarily, we suggest that the initial response at the end of treatment be defined as (1) three or fewer UBMs per day, (2) a reduction in UBMs of more than 50% per day, (3) a decrease in stool volume of more than 75% for those with ostomy, or (4) attainment of bowel movements of Bristol Stool Form Scale types 1-4, on average, by day 2 after completion of primary CDI therapy (ie, assessed on day 11 and day 12 of a 10-day treatment course) and following an investigator determination that CDI treatment can be ceased.

Micafungin Pharmacodynamics Predict Clinical Outcomes in Hospitalized Patients with Candidemia caused by certain Candida species

BACKGROUND

Echinocandins are guideline-preferred therapies for invasive candidiasis (IC). Fixed dosing of echinocandins is commonly used despite variations in body mass index and echinocandin susceptibility. The purpose of this study was to evaluate clinical outcomes of micafungin based on population-predicted pharmacokinetic/pharmacodynamic (PK/PD) factors and susceptibility.

METHODS

Candida isolate results were screened from bloodstream or intraabdominal cultures of hospitalized patients admitted to a quaternary-care teaching hospital. Patients with a first episode of IC who received micafungin for at least 48 hours were included. Patients with mixed cultures or Candida species with no minimum inhibitory concentration (MIC) differences were excluded. Breakpoints for micafungin MIC and area under the curve (AUC)/MIC ratio were calculated using classification and regression tree (CART) analysis and related to clinical outcomes. Primary efficacy outcome was candida-contributable mortality, defined as mortality within 28 days of positive culture with concomitant micafungin treatment failure; secondary outcome was micafungin treatment failure within 28 days, RESULTS: Seventy-two patients were included of whom 15 (21%) had Candida-contributable mortality and 34 (47%) experienced micafungin treatment failure. C. albicans and C. tropicalis did not have differing MICs and these patients were excluded from the study. Mortality using a CART-derived MIC breakpoint of >1.0 mg/L was 38% compared to 9% in patients infected with lower MIC strains (p=0.003). Patients with a CART-derived AUC/MIC value >138.5 had a mortality rate of 9% compared to 41% for patients with AUC/MIC values below the breakpoint (p=0.0013). Results were similar for treatment failure rates, and both were confirmed using multivariable models.

CONCLUSIONS

CART-derived micafungin MIC and AUC/MIC breakpoints predicted patient mortality and treatment failure for certain Candida species. These results support the need for further PK/PD studies to optimize echinocandin dosing and improve patient outcomes.

Preservation of the Innate Immune Response to Clostridioides difficile Infection in Hospitalized Immunocompromised Patients

Background

Clostridioides difficile infection (CDI) immune response is influenced by the innate and adaptive (humoral) immune systems. Our prior research found attenuated humoral responses to C difficile in immunocompromised hosts (ICHs) with CDI. We sought to evaluate whether the innate immune response to CDI was influenced by ICH status.

Methods

We conducted a prospective study of hospitalized adults with CDI (acute diarrhea, positive C difficile stool nucleic acid amplification testing [NAAT], and decision to treat), with and without immunosuppression and measured a panel of cytokines (granulocyte colony-stimulating factor [G-CSF], interleukin [IL]-10, IL-15, IL-1β, IL-4, IL-6, IL-8, and tumor necrosis factor-α) in blood and stool at CDI diagnosis. Results were compared with measurements from a cohort of asymptomatic carrier patients (ASCs) (NAAT positive, without diarrhea) with and without immunocompromise.

Results

One hundred twenty-three subjects (42 ICHs, 50 non-ICHs, 31 ASCs) were included. Median values for blood and stool cytokines were similar in ICH versus non-ICH CDI subjects. In blood, G-CSF, IL-10, IL-15, IL-6, and IL-8 were higher in both groups of CDI subjects versus the ASC cohort (P < .05). In stool, IL-1β and IL-8 were higher in both groups of CDI subjects versus the ASC cohort (P < .05). Median stool concentrations of IL-1β demonstrated significant differences between the groups (ICHs, 10.97 pg/mL; non-ICHs, 9.71 pg/mL; and ASCs, 0.56 pg/mL) (P < .0001).

Conclusions

In this small exploratory analysis, ICH status did not significantly impact blood and fecal patterns of cytokines in humans at the diagnosis of CDI, suggesting that the innate immune response to C difficile may be conserved in immunocompromised patients.

Clinical characteristics, microbiology and outcomes of a cohort of patients treated with ceftolozane/tazobactam in acute care inpatient facilities, Houston, Texas, USA

Background

Ceftolozane/tazobactam is a β-lactam/β-lactamase inhibitor combination with activity against a variety of Gram-negative bacteria, including MDR Pseudomonas aeruginosa. This agent is approved for hospital-acquired and ventilator-associated bacterial pneumonia. However, most real-world outcome data come from small observational cohorts. Thus, we sought to evaluate the utilization of ceftolozane/tazobactam at multiple tertiary hospitals in Houston, TX, USA.

Methods

We conducted a multicentre retrospective study of patients receiving at least 48 h of ceftolozane/tazobactam therapy from January 2016 through to September 2019 at two hospital systems in Houston. Demographic, clinical and microbiological data were collected, including the infecting bacterial isolate, when available. The primary outcome was composite clinical success at hospital discharge. Secondary outcomes included in-hospital mortality and clinical disposition at 14 and 30 days post ceftolozane/tazobactam initiation. Multivariable logistic regression analysis was used to identify predictors of the primary outcome and mortality. Recovered isolates were tested for susceptibility to ceftolozane/tazobactam and underwent WGS.

Results

A total of 263 patients were enrolled, and composite clinical success was achieved in 185 patients (70.3%). Severity of illness was the most consistent predictor of clinical success. Combination therapy with ceftolozane/tazobactam and another Gram-negative-active agent was associated with reduced odds of clinical success (OR 0.32, 95% CI 0.16-0.63). Resistance to ceftolozane/tazobactam was noted in 15.4% of isolates available for WGS; mutations in ampC and ftsI were common but did not cluster with a particular ST.

Conclusions

Clinical success rate among this patient cohort treated with ceftolozane/tazobactam was similar compared with previous experiences. Ceftolozane/tazobactam remains an alternative agent for treatment of susceptible isolates of P. aeruginosa.

Assessment of Quality of Life Among Patients With Recurrent Clostridioides difficile Infection Treated with Investigational Oral Microbiome Therapeutic SER-109: Secondary Analysis of a Randomized Clinical Trial

IMPORTANCE

Recurrent Clostridioides difficile infection (CDI) is a debilitating disease leading to poor health-related quality of life (HRQOL), loss of productivity, anxiety, and depression. The potential association of treatment with HRQOL has not been well evaluated.

OBJECTIVES

To explore the association of SER-109 compared with placebo on HRQOL in patients with recurrent CDI up to week 8.

DESIGN, SETTING, AND PARTICIPANTS

This study was a secondary analysis of a randomized, double-blind, placebo-controlled trial that took place at 56 sites in the US and Canada from July 2017 to April 2020 and included 182 patients randomized to SER-109 or placebo groups.

INTERVENTIONS

SER-109 or placebo (4 capsules once daily for 3 days) following antibiotics for CDI.

MAIN OUTCOMES AND MEASURES

Exploratory analysis of HRQOL using the disease specific Clostridioides difficile Quality of Life Survey (Cdiff32) assessed at baseline, week 1, and week 8.

RESULTS

In this study, 182 patients (109 [59.9%] female; mean age, 65.5 [16.5] years) were randomized to SER-109 (89 [48.9%]) or placebo (93 [51.1%]) groups and were included in the primary and exploratory analyses. Baseline Cdiff32 scores were similar between patients in the SER-109 and placebo groups (52.0 [18.3] vs 52.8 [18.7], respectively). The proportion of patients with overall improvement from baseline in the Cdiff32 total score was higher in the SER-109 arm than placebo at week 1 (49.4% vs 26.9%; P = .012) and week 8 (66.3% vs 48.4%; P = .001).Greater improvements in total and physical domain and subdomain scores were observed in patients in the SER-109 group compared with placebo as early as week 1, with continued improvements observed at week 8. Among patients in the placebo group, improvements in HRQOL were primarily observed in patients with nonrecurrent CDI while patients in the SER-109 group reported improvements in HRQOL, regardless of clinical outcome.

CONCLUSIONS AND RELEVANCE

In this secondary analysis of a phase 3 clinical trial, SER-109, an investigational microbiome therapeutic was associated with rapid and steady improvement in HRQOL compared with placebo through 8 weeks, an important patient-reported outcome.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03183128.

Gut microbiota changes associated with Clostridioides difficile infection and its various treatment strategies

Human gut microbiota are critical to both the development of and recovery from Clostridioides difficile infection (CDI). Antibiotics are the mainstay of CDI treatment, yet inherently cause further imbalances in the gut microbiota, termed dysbiosis, complicating recovery. A variety of microbiota-based therapeutic approaches are in use or in development to limit disease- and treatment-associated dysbiosis and improve rates of sustained cure. These include the recently FDA-approved fecal microbiota, live-jslm (formerly RBX2660) and fecal microbiota spores, live-brpk (formerly SER-109), which represent a new class of live biotherapeutic products (LBPs), traditional fecal microbiota transplantation (FMT), and ultra-narrow-spectrum antibiotics. Here, we aim to review the microbiome changes associated with CDI as well as a variety of microbiota-based treatment approaches.

221. Assessment and Proposed Revision of Clinical Trial Clostridioides difficile Infection Clinical Response and Outcomes Definitions

Background

Clostridioides difficile infection (CDI) research is limited by a lack of standardized definitions for clinical response and disease outcomes, which impacts clinical drug development and results comparison between studies. We aimed to assess outcome definitions in CDI therapeutic trials to propose new versions that are clinically relevant, discrete and objective.

Methods

A multidisciplinary group of CDI experts met monthly to review response endpoints from published clinical trials of antibiotic therapy for CDI. Previously published phase III or IV trials were assessed for outcome definitions. Discussions were held to reach a consensus on new clinical trial endpoints for adults and children to improve the accuracy and clinical relevance of measures of treatment success.

Results

Significant heterogeneity was noted amongst the primary endpoints in phase III and IV CDI antibiotic treatment trials. Initial clinical cure (ICC), strictly defined as < 3 unformed bowel movements/24 hour, and sustained clinical cure (SCC) were primary outcome measures for recent clinical trials. The strict ICC definition incompletely measures treatment success as assessed in clinical practice and, since ICC is necessary to achieve SCC, may lead to type II error for SCC. A set of proposed alternative outcome definitions was developed using the terms initial response (IR) and sustained response (SR) (Figure 1). IR allows for investigator assessment of overall improvement in CDI response more analogous to clinical practice and will lead to more patients eligible to meet SR. Achievement of SR requires both IR and no need for retreatment of CDI by day 30 after antibiotic completion and is the more relevant endpoint for CDI therapeutic development. The use of a less restrictive IR definition will more accurately capture early responses to treatment and importantly increase the validity of SR. The shortening of follow-up period by 30 days is also anticipated to reduce costs and efforts associated with conducting trials.

Timeline of CDI outcome assessments for clinical trials

Conclusion

The set of definitions proposed here will more accurately capture clinical success and standardize the approach to outcome assessment in trials of CDI therapeutics.

Disclosures

Carolyn D. Alonso, MD, Cidara Therapeutics: Advisor/Consultant|Merck: Advisor/Consultant Oliver A. Cornely, Prof. Dr., Abbott: Honoraria|Abbvie: Advisor/Consultant|Actelion: Board Member|Al-Jazeera Pharmaceuticals: Honoraria|Allecra Therapeutics: Board Member|Amplyx: Advisor/Consultant|Amplyx: Grant/Research Support|Astellas: Honoraria|Basilea: Advisor/Consultant|Basilea: Grant/Research Support|Biocon: Advisor/Consultant|Biosys: Advisor/Consultant|BMBF: Grant/Research Support|Cidara: Advisor/Consultant|Cidara: Board Member|Cidara: Expert Testimony|Cidara: Grant/Research Support|CoRe Consulting: Stocks/Bonds|Da Volterra: Advisor/Consultant|DLR: Grant/Research Support|DZIF: Grant/Research Support|Entasis: Board Member|EU Directorate-General for Resarch and Innovation: Grant/Research Support|F2G: Grant/Research Support|German Patent and Trade Mark Office: German patent (DE 10 2021 113 007.7)|Gilead: Advisor/Consultant|Gilead: Grant/Research Support|Grupo Biotoscana/United Medical/Knight: Honoraria|Hikma: Honoraria|IQVIA: Board Member|Janssen: Board Member|Matinas: Advisor/Consultant|Matinas: Grant/Research Support|MedPace: Advisor/Consultant|MedPace: Grant/Research Support|MedScape: Honoraria|MedUpdate: Honoraria|Menarini: Advisor/Consultant|Merck/MSD: Grant/Research Support|Merck/MSD: Honoraria|Molecular Partners: Advisor/Consultant|MSG-ERC: Advisor/Consultant|Mundipharma: Grant/Research Support|Mylan: Honoraria|Noxxon: Advisor/Consultant|Octapharma: Advisor/Consultant|Octapharma: Grant/Research Support|Paratek: Board Member|Pardes: Advisor/Consultant|Pfizer: Grant/Research Support|Pfizer: Honoraria|Projektträger Jülich: Grant/Research Support|PSI: Advisor/Consultant|PSI: Board Member|Pulmocide: Board Member|Scynexis: Advisor/Consultant|Scynexis: Grant/Research Support|Seres: Advisor/Consultant|Shionogi: Board Member|Wiley (Blackwell): Editor-in-Chief, Mycoses Kevin W. Garey, PharmD, MS, Acurx Pharmaceuticals: Grant/Research Support|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support|Summit Pharmaceuticals: Grant/Research Support Dale N. Gerding, MD, Destiny Pharma plc.: Advisor/Consultant Stuart Johnson, M.D., Ferring Pharmaceuticals: Membership on Ferring Publication Steering Committee|Ferring Pharmaceuticals: Employee|Summit Plc: Advisor/Consultant Stacy A. Kahn, MD, Lilly: Stocks/Bonds Ciaran P. Kelly, n/a, Artugen: Advisor/Consultant|Facile Therapeutics: Advisor/Consultant|Ferring Pharma: Advisor/Consultant|Finch: Advisor/Consultant|Finch: Advisor/Consultant|First Light Biosciences: Advisor/Consultant|First Light Biosciences: Ownership Interest|Milky Way Biosciences: Advisor/Consultant|Milky Way Biosciences: Grant/Research Support|Pfizer: Advisor/Consultant|Seres Therapeutics: Advisor/Consultant|Summit Therapeutics: Advisor/Consultant Larry K. Kociolek, MD, MSCI, Merck: Grant/Research Support Thomas J. Louie, MD, Artugen: Advisor/Consultant|Artugen: Grant/Research Support|Crestone: Advisor/Consultant|Crestone: Grant/Research Support|Finch Therapeutics: Advisor/Consultant|Finch Therapeutics: Grant/Research Support|Rebiotix: Advisor/Consultant|Rebiotix: Grant/Research Support|Seres Therapeutics: Advisor/Consultant|Seres Therapeutics: Grant/Research Support|summit plc: Advisor/Consultant|summit plc: Grant/Research Support|Vedanta Biosciences: Advisor/Consultant|Vedanta Biosciences: Grant/Research Support Maria Vehreschild, Prof. Dr., 3M: speaker fee|Astellas: Advisor/Consultant|Astellas: speaker fee|biologische heilmittel heel gmbh: Grant/Research Support|BioNtech: Grant/Research Support|EUMEDICA: Advisor/Consultant|Farmak International Holding: Advisor/Consultant|Ferring: Advisor/Consultant|Ferring: Speaker fee|Gilead Sciences: Advisor/Consultant|Immunic AG: Advisor/Consultant|MaaT: Advisor/Consultant|Merck: Advisor/Consultant|Merck: speaker fee|MSD: Advisor/Consultant|MSD: Grant/Research Support|MSD: speaker fees|Pfizer: speaker fee|Roche Molecular Systems: Grant/Research Support|Roche Molecular Systems: speaker fees|SocraRTec R&D GmbH: Advisor/Consultant|Takeda California: Grant/Research Support Professor Mark H. Wilcox, MD, FRCPath, GSK: Advisor/Consultant|GSK: Board Member|GSK: Grant/Research Support|Pfizer: Advisor/Consultant|Phico Therapeutics: Board Member|Seres: Advisor/Consultant|Seres: Board Member|Seres: Grant/Research Support|Summit: Advisor/Consultant|Summit: Grant/Research Support Erik R. Dubberke, MD, MSPH, Abbott: Advisor/Consultant|Ferring: Advisor/Consultant|Ferring: Grant/Research Support|Merck: Advisor/Consultant|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Seres: Advisor/Consultant|Summit: Advisor/Consultant|Synthetic Biologics: Grant/Research Support.

489. Bile Acid Concentrations in Healthy Volunteers Receiving Oral Omadacycline or Vancomycin

Background

Microbiome disruption associated with Clostridioides difficile infection (CDI) includes reduced metabolism of primary to secondary bile acids leading to increased likelihood of C. difficile germination and CDI recurrence. Omadacycline has potent in vitro activity against C. difficile but its effect on the microbiome is unknown. The purpose of this study was to assess changes in bile acid concentrations in healthy volunteers given omadacycline compared to vancomycin, the most common antibiotic used to treat CDI.

Methods

As part of an ongoing healthy volunteer study of adults between 18 and 40 years, subjects received a 10-day course of oral omadacycline or vancomycin. Stool samples were collected and bile acids were extracted and quantified via targeted liquid chromatography-mass spectrometry (LC-MS). For this analysis, samples collected at the end of antibiotic therapy (day 9-10) were analyzed for primary and secondary bile acids. Results were compared and visualized using R (ggplot2).

Results

Between October 2020 and December 2021, 16 healthy volunteers aged 26 ± 5 years (male: 69%; Caucasian: 31%; mean body mass index: 23.6 ± 3.8 kg/m2) were enrolled. Concentrations of primary bile acids (cholic acid and chenodeoxycholic acid) were higher in patients receiving oral vancomycin than those receiving omadacycline (Table 1). Secondary bile acids were higher in the omadacycline arm compared to vancomycin. Secondary:primary bile ratio was higher for omadacycline (0.43) than vancomycin (0.03).

Conclusion

Omadacycline preserved bile acid homeostasis in the gut to a higher extent that vancomycin, suggesting reduced microbiome dysbiosis. With potent in vitro C. difficile activity, availability as an oral and IV formulations, and favorable microbiome properties, further development of omadacycline for the treatment of CDI is warranted.

Disclosures

Kevin W. Garey, PharmD, MS, Acurx Pharmaceuticals: Grant/Research Support|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support|Summit Pharmaceuticals: Grant/Research Support.

401. Rigor and Reproducibility of Clostridioides difficile susceptibility testing

Background

The growth and susceptibility testing of anaerobic bacteria presents many unique challenges. The Clinical Laboratory Standards Institute (CLSI) recommends performing minimum inhibitory concentration (MIC) testing for C. difficile through agar dilution (AD) assay, which carries logistical and time burdens compared to broth microdilution (BMD) methods. In this project we aim to assess the intra-and inter-laboratory reproducibility of MIC testing for C. difficile.

Methods

A total of 30 C. difficile isolates underwent MIC testing using AD and BMD techniques. To test intra-lab reproducibility, proficiency testing to develop a reproducible MIC testing process using 18 isolates was implemented across two multi-disciplinary labs, which was then validated in a prospective cohort of 116 isolates. MICs obtained by each method and lab were compared and essential agreement (EA) and major and minor error rates were calculated. To combat the labor and time-intensive demands of AD testing, automation with Integra Assist Plus was tested. Times for plate set up using a technician versus the Integra Assist Plus were measured twice and the average times were compared.

Results

AD and BMD yielded discordant resistant/susceptible results in 16.7% (5/30) of isolates tested. During proficiency testing, intra-lab comparison of AD MICs yielded 88.9% (16/18) EA and no disagreements occurred with more than 1 dilution difference. EA improved in the larger cohort to 93.9% (109/116), of which minor and major disagreements occurred in 17% (21/116) and 25% (29/116), respectively. A total of 10’4” minutes were saved using automation (12’44” mean) versus a technician (24’40” mean).

Conclusion

Here we present the process undertaken to ensure the rigor and reproducibility of C. difficile susceptibility testing. We developed a procedure that yields accurate results from two different labs, minimizes cost, and lowers the overall time required. Our future research will include validation with a larger sample and more academic partners.

Disclosures

Kevin W. Garey, PharmD, MS, Acurx: Grant/Research Support|cidara: Advisor/Consultant|cidara: Grant/Research Support|Paratek: Grant/Research Support|Seres Health: Grant/Research Support|Summit: Grant/Research Support.

620. Pharmacokinetic-Pharmacodynamic Analysis of Oral Vancomycin and Gut Microbiome Changes in Healthy Volunteers: an Exploratory Study

Background

Oral vancomycin causes profound changes to the gut microbiome due to high intra-colonic vancomycin concentrations. However, pharmacokinetics of oral vancomycin causing pharmacodynamic changes have not been explored, especially during the early dosing period. The purpose of this study was to investigate fecal vancomycin concentrations in healthy individuals in relation to gut microbiome diversity changes.

Methods

Healthy subjects 18-45 years with no antibiotic use for at least 28 days were given oral vancomycin 125 mg was given every 6 hours for 10 days. Stool samples were collected at baseline and during antibiotic therapy. Vancomycin concentrations were obtained through high-performance liquid chromatography (HPLC) assay. For this early pharmacokinetics analysis, stool samples from day 0 (baseline) to day 4 were included. Shotgun metagenomics sequencing was used for microbiome analysis. Descriptive analysis was performed to identify gut-microbiome phyla changes in correlation with detectable oral vancomycin fecal concentrations.

Results

A total of 6 healthy volunteers aged 32±5 years (Male: 100%; Caucasian: 50%; mean BMI: 26.8±4.5 kg/m²) were included. In the early dosing period (day 0-4), the mean fecal vancomycin concentrations increased daily with the highest concentration of 1,586 μg/g of stool occurring on day 4. Three of 9 subjects (50%) had undetectable oral vancomycin levels one days 1 and 2 of dosing. Within 24-48 hour of detectable vancomycin levels, subject-specific changes of gut microbiome phylum-level proportions were observable. Overall, an increase in Actinobacteria and Proteobacteria phyla and decrease in Firmicute phylum was observed within 24 hours that vancomycin was detected in the feces.

Conclusion

High concentrations of vancomycin are achieved in the stool by day four of dosing for all subjects; however, low concentrations are observed early in the dosing period for some subjects. Proportional, subject specific differences in gut microbiome phyla were observed within 24 hours of detectable vancomycin levels in the feces.

Disclosures

Kevin W. Garey, PharmD, MS, Acurx Pharmaceuticals: Grant/Research Support|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support|Summit Pharmaceuticals: Grant/Research Support.

380. A molecular epidemiological exploration of reduced vancomycin susceptibility in Clostridioides difficile

Background

Use of vancomycin to treat Clostridioides difficile infection (CDI) has increased following recent IDSA/SHEA treatment guideline updates, applying a selection pressure for resistance development. We previously demonstrated acquired mutations in VanSR two-component system led to constitutive vanG expression and improved in vitro C. difficile survival in physiologic vancomycin concentrations. We aim to describe the molecular epidemiology of reduced vancomycin susceptibility in clinical isolates during a period of high vancomycin use.

Methods

A cohort study was performed including adult patients hospitalized with CDI in two health systems (14 hospitals) in the Houston Area between 2017-2021. (Stool transport) C. difficile were ribotyped by fluorescent PCR and susceptibility tested by agar dilution in accordance with CLSI standards. Reduced vancomycin susceptibility was defined by minimum inhibitory concentrations (MICs) >2 mg/L. Sanger sequencing was conducted on a subgroup of isolates to identify VanSR mutations. Analysis using Chi square was performed using IBM SPSS Statistics (v 28.0.1.0).

Results

A total of 36% (165/465) of isolates exhibited reduced vancomycin susceptibility (MIC₅₀ = 2 mg/L, MIC₉₀ = 4 mg/L, range 0.5-16 mg/L), of which 348 were ribotyped. A significantly higher proportion of ribotype (RT) 027 isolates demonstrated reduced vancomycin susceptibility (83%) compared to other common ribotypes (30%); p< 0.001). No differences based on collection year (p=0.3) or healthcare system (p=0.08) were observed. Overall, 11% (7/56) of isolates exhibiting mutations in VanS (n=1), VanR (n=5), or both (n=1). VanSR mutations were present in 47% (7/15) of those with MICs >2mg/L vs 0% (0/41) of those with MICs ≤2 mg/L (p< 0.001).

Conclusion

A high proportion of clinical C. difficile isolates exhibited elevated MICs to vancomycin, which was most common in RT027 isolates. Mutations in the vanG regulator, VanSR, correlated with elevated MICs in a subgroup of isolates. Future research is needed to expand upon molecular mechanisms and clinical implications of reduced vancomycin susceptibility.

Disclosures

Kevin W. Garey, PharmD, MS, Acurx Pharmaceuticals: Grant/Research Support|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support|Summit Pharmaceuticals: Grant/Research Support.

883. Stool Toxin Concentrations Are Higher in Children with Baseline Severe Disease, Severe Outcomes, and Recurrence

Background

In adults with C. difficile infection (CDI), higher baseline stool concentrations of toxins A and B are associated with severe baseline disease, CDI-attributable severe outcomes, and recurrence. We evaluated whether stool toxin concentration predicts these presentations in children with CDI.

Methods

We performed a prospective cohort study from 2016-2019. Participants were inpatients ≤17 years old at two pediatric hospitals with diarrhea and positive C. difficile testing who received therapy. Patients were followed for 40 days after baseline stool sample for severe outcomes (intensive care unit admission, colectomy, or death, categorized as CDI primarily attributable, CDI contributed, or CDI not contributing) and recurrence (resolution followed by new diarrhea and re-initiation of therapy). Baseline stool toxin A & B concentrations were measured using ultrasensitive single molecule array assay (cutoff for positive result = 20 pg/mL). Median baseline toxin concentrations were compared between groups using Wilcoxon tests.

Results

We enrolled 206 patients [median age 8.9 years (IQR, 4.7–13.2)]. Children with severe baseline disease by IDSA-SHEA criteria (n = 39) had higher median stool toxin A+B concentration than those without severe disease (n = 131) (2,912.6 vs. 500.5 pg/mL, P=0.05). Of the cohort, 40 (19%) had a severe outcome (4 primarily attributed to CDI, 19 with contribution from CDI, and 17 unrelated to CDI). Median toxin A+B concentration was non-significantly higher in children with a primarily-attributed severe outcome versus those without severe outcome (19,473 vs. 429.1 pg/mL, P=0.317) (Figure 1). Of 197 children with eligible data, recurrence occurred in 18 (9.1%); baseline toxin A+B concentration was significantly higher in patients with versus without recurrence (3,946.7 vs. 283.3 pg/mL, P=0.026) (Figure 2).

Conclusion

Higher stool toxin concentrations are present in children with baseline severe CDI, a CDI-attributable severe outcome, or recurrence compared with children without these presentations. Quantification of stool toxin concentration may be helpful in identifying severe CDI and predicting CDI outcomes, which could help guide decisions about clinical management.

Disclosures

Larry K. Kociolek, MD, MSCI, Merck: Grant/Research Support Timothy J. Savage, MD, MPH, MSc, UCB: Contract to Brigham and Women's Hospital Alice Banz, PhD, biomerieux: Simoa assays were performed by bioMerieux, and A.B. is an employee of bioMerieux Kevin W. Garey, PharmD, MS, Acurx: Grant/Research Support|cidara: Advisor/Consultant|cidara: Grant/Research Support|Paratek: Grant/Research Support|Seres Health: Grant/Research Support|Summit: Grant/Research Support Ciaran P. Kelly, n/a, Artugen: Advisor/Consultant|Facile Therapeutics: Advisor/Consultant|Ferring Pharma: Advisor/Consultant|Finch: Advisor/Consultant|Finch: Advisor/Consultant|First Light Biosciences: Advisor/Consultant|First Light Biosciences: Ownership Interest|Milky Way Biosciences: Advisor/Consultant|Milky Way Biosciences: Grant/Research Support|Pfizer: Advisor/Consultant|Seres Therapeutics: Advisor/Consultant|Summit Therapeutics: Advisor/Consultant.

Higher In Vivo Fecal Concentrations of Clostridioides difficile Toxins A and B in Patients With North American Pulsed-Field Gel Electrophoresis Type 1/Ribotype 027 Strain Infection

Ultrasensitive, quantitative Clostridioides difficile stool toxin measurement demonstrated significantly higher concentrations of toxins A and B in patients infected with the North American pulsed-field gel electrophoresis type 1/ribotype 027 (NAP-1/027) strain compared with other strains, providing in vivo confirmation of the in vitro association between NAP-1/027 and elevated toxin production.

Development of the invasive candidiasis discharge [I Can discharge] model: a mixed methods analysis

Patients with invasive candidiasis (IC) have complex medical and infectious disease problems that often require continued care after discharge. This study aimed to assess echinocandin use at hospital discharge and develop a transition of care (TOC) model to facilitate discharge for patients with IC. This was a mixed method study design that used epidemiologic assessment to better understand echinocandin use at hospital discharge TOC. Using grounded theory methodology focused on patients given echinocandins during their last day of hospitalization, a TOC model for patients with IC, the invasive candidiasis [I Can] discharge model was developed to better understand discharge barriers. A total of 33% (1405/4211) echinocandin courses were continued until the last day of hospitalization. Of 536 patients chosen for in-depth review, 220 (41%) were discharged home, 109 (20%) were transferred, and 207 (39%) died prior to discharge. Almost half (46%, 151/329) of patients discharged alive received outpatient echinocandin therapy. Independent predictors for outpatient echinocandin use were osteomyelitis (OR, 4.1; 95% CI, 1.1-15.7; p = 0.04), other deep-seated infection (OR, 4.4; 95% CI, 1.7-12.0; p = 0.003), and non-home discharge location (OR, 3.9, 95% CI, 2.0-7.7; p < 0.001). The I Can discharge model was developed encompassing four distinct themes which was used to identify potential barriers to discharge. Significant echinocadin use occurs at hospital discharge TOC. The I Can discharge model may help clinical, policy, and research decision-making processes to facilitate smoother and earlier hospital discharges.

Stool Toxin Concentration Does Not Distinguish Clostridioides difficile Infection from Colonization in Children Less Than 3 Years of Age

In a prospective cohort study, stools from children <3 years with and without diarrhea who were Clostridioides difficile nucleic acid amplification test-positive underwent ultrasensitive and quantitative toxin measurement. Among 37 cases and 46 controls, toxin concentration distributions overlapped substantially. Toxin concentration alone does not distinguish C. difficile infection from colonization in young children.

Recurrent Clostridioides difficile infection worsens anxiety-related patient-reported quality of life

Background

Clostridioides difficile infection (CDI) is associated with high recurrence rates impacting health-related quality of life (HrQOL). However, patient-reported data are lacking particularly in the outpatient setting. We assessed changes in HrQOL over time in patients treated with bezlotoxumab at US infusion centers and determined clinical factors associated with HrQOL changes.

Methods

The HrQOL survey was conducted in adult patients with CDI, who received bezlotoxumab in 25 US outpatient infusion centers. The survey was adapted from the Cdiff32 instrument to assess anxiety-related changes to HrQOL and completed on the day of infusion (baseline) and at 90 days post bezlotoxumab (follow-up). Demographics, disease history, CDI risk factors, and recurrence of CDI (rCDI) at 90-day follow-up were collected. Changes in HrQOL scores were calculated and outcomes assessed using a multivariable linear regression model with P < 0.05 defined as statistically significant.

Results

A total of 144 patients (mean age: 68 ± 15 years, 63% female, median Charlson index: 4, 15.9% rCDI) were included. The overall mean baseline and follow-up HrQOL scores were 26.4 ± 11.5 and 56.4 ± 25.0, respectively. At follow-up, this score was significantly higher for patients who had primary CDI (34.5 ± 21.7) compared to those with multiple rCDI (24.7 ± 21.0; P = 0.039). The mean HrQOL change at follow-up was significantly higher for patients without rCDI (34.1 ± 28.8 increase) compared to patients with rCDI (6.7 ± 19.5 increase; P < 0.001), indicating improvement in anxiety.

Conclusions

Using the Cdiff32 instrument, we demonstrated that HrQOL worsened significantly in patients with further rCDI. These findings support the use of Cdiff32 in assessing CDI-related humanistic outcomes.

Fulminant Clostridioides difficile Infection: A Review of Treatment Options for a Life-Threatening Infection

Fulminant Clostridioides difficile infection (FCDI) encompasses 3 to 5% of all CDI cases with associated mortality rates between 30 and 40%. Major treatment modalities include surgery and medical management with antibiotic and nonantibiotic therapies. However, identification of patients with CDI that will progress to FCDI is difficult and makes it challenging to direct medical management and identify those who may benefit from surgery. Furthermore, since it is difficult to study such a critically ill population, data investigating treatment options are limited. Surgical management with diverting loop ileostomy (LI) instead of a total abdominal colectomy (TAC) with end ileostomy has several appealing advantages, and studies have not consistently demonstrated a clinical benefit with this less-invasive strategy, so both LI and TAC remain acceptable surgical options. Successful medical management of FCDI is complicated by pharmacokinetic changes that occur in critically ill patients, and there is an absence of high-quality studies that included patients with FCDI. Recommendations accordingly include a combination of antibiotics administered via multiple routes to ensure adequate drug concentrations in the colon: intravenous metronidazole, high-dose oral vancomycin, and rectal vancomycin. Although fidaxomicin is now recommended as first-line therapy for non-FCDI, there are limited clinical data to support its use in FCDI. Several nonantibiotic therapies, including fecal microbiota transplantation and intravenous immunoglobulin, have shown success as adjunctive therapies, but they are unlikely to be effective alone. In this review, we aim to summarize diagnosis and treatment options for FCDI.

Efficacy, Safety, Pharmacokinetics, and Microbiome Changes of Ibezapolstat in Adults with Clostridioides difficile Infection: A Phase 2a Multicenter Clinical Trial

Background

This study was the first human validation of the gram-positive bacterial DNA polymerase IIIC target in patients with Clostridioides difficile infection. The primary objectives were to assess clinical cure rates and adverse events (AEs). Secondary objectives were to evaluate plasma/fecal pharmacokinetics, microbiologic eradication, microbiome and bile acid effects, and sustained clinical cure (SCC) with ibezapolstat.

Methods

This single-arm, open-label, phase 2a study enrolled adults with C. difficile infection at 4 US centers. Patients received ibezapolstat 450 mg orally every 12 hours for 10 days and followed for an additional 28 days to assess study objectives.

Results

Ten patients with a mean (standard deviation [SD]) age of 49 [15] years were enrolled. Seven AEs were reported classified as mild-moderate. Plasma levels of ibezapolstat ranged from 233 to 578 ng/mL while mean (SD) fecal levels were 416 (494) µg/g stool by treatment day 3 and >1000 µg/g stool by days 8–10. A rapid increase in alpha diversity in the fecal microbiome was noted after starting ibezapolstat therapy, which was maintained after completion of therapy. A proportional decrease in Bacteroidetes phylum was observed (mean change [SD], −10.0% [4.8%]; P = .04) with a concomitantly increased proportion of Firmicutes phylum (+14.7% [5.4%]; P = .009). Compared with baseline, total primary bile acids decreased by a mean (SD) of 40.1 (9.6) ng/mg stool during therapy (P < .001) and 40.5 (14.1) ng/mg stool after completion of therapy (P = .007). Rates of both initial clinical cure and SCC at 28 days were 100% (10 of 10 patients).

Conclusions

In this phase 2a study, 10 of 10 patients achieved SCC, demonstrated favorable pharmacokinetics, minimal AEs, and beneficial microbiome and bile acids results. These results support continued clinical development.

157. A Multicenter, Mixed-Method Evaluation of Delayed Hospital Discharge in Patients with Invasive Candidiasis Receiving Echinocandins

Background

Patients with systemic candidiasis often receive prolonged echinocandin therapy in the inpatient or outpatient setting. Rezafungin is a novel echinocandin currently in clinical trials characterized by once-weekly dosing interval. In order to understand the potential benefit of rezafungin to facilitate earlier hospital discharge, the purpose of this project was to better understand barriers to discharge in patients with proven or suspected invasive candidiasis.

Methods

Electronic health records from two large health systems (20+ hospitals) were reviewed to identify patients given an echinocandin. Patients given an echinocandin until hospital discharge were evaluated for outpatient use as well as barriers that prevented earlier discharge. Identified barriers were developed into a quantitative framework and a qualitative interview guide. Using a constant comparative method, the framework for hospital discharge barriers was constructed using a series of open-ended questions and axial coding to identify discharge barrier themes. Results were integrated to produce a mixed-method model.

Results

A total of 1,665 echinocandin courses were evaluated. Five hundred and thirty-four patients (32%) received echinocandin therapy until at least the day of hospital discharge of which 328 of 534 (61%) patients were either discharged to home or transferred to another facility. Significant predictors for outpatient echinocandin use were osteomyelitis (OR 4.07, 95% CI: 1.06-15.66; p=0.041) and other deep-seated infection (OR 4.44; 95% CI: 1.65-11.96; p=0.003). Stewardship analysis identified the majority of patients (54%) had the possibility for at least one day earlier discharge (potential earlier discharge:1.65±1.16 days). The quantitative model identified major barriers to be transition of care-, other medical care-, and infectious diseases-related. The qualitative model largely agreed with the quantitative model with additional psychosocial and health care access variables identified.

Conclusion

Using a mixed method approach, barriers to hospital discharge and potential use of new antifungal therapies were identified. These data could be used to assist transitions of care in patients with invasive candidiasis.

Disclosures

Truc T. Tran, PharmD, Merck (Grant/Research Support) Kevin W. Garey, Pharm.D., M.S., FASHP, Summit Therapeutics (Research Grant or Support)

701. An Open-label Phase 2a Study of Ibezapolstat, a Unique Gram-positive Selective Spectrum (GPSS) Antibiotic, for Patients with Clostridioides difficile Infection

Background

Ibezapolstat, a DNA polymerase IIIC inhibitor, currently in Phase 2 clinical development for treatment of C. difficile infection (CDI). Its unique mechanism of action targets low G+C content Gram-positive bacteria primarily Firmicutes including C. difficile. Phase I healthy volunteer results demonstrated a favorable microbiome profile suggestive of an anti-recurrence effect. The purpose of this study was to report clinical outcomes, pharmacokinetics, and microbiome changes from this Phase 2a clinical study and to continue to test for anti-recurrence microbiome properties.

Methods

Ibezapolstat 450 mg was given twice daily for 10 days to patients with mild-moderate CDI defined as diarrhea plus a positive C. difficile toxin test. Test of cure was evaluated at day 12 and sustained clinical cure at day 38. Stool samples were evaluated for C. difficile cultures and microbiome changes.

Results

Ten subjects (female: 50%) aged 50 ±15 years were enrolled. All ten subjects experienced a clinical cure by the test of cure visit at day 12 and all 10 subjects experienced a sustained clinical cure at the day 38 visit. Ibezapolstat was well tolerated with 1 adverse event (nausea) probably related to drug. Ibezapolstat systemic exposure was minimal with no plasma level reaching 1 ug/mL any time during therapy. Ibezapolstat colonic concentrations averaged 400 ug/g stool at day 3 and greater than 1,000 ug/g by day 10 of dosing. Six of the seven available baseline stool samples grew toxigenic C. difficile of various ribotypes including RT078-226 and RT014-020 (Ibezapolstat MIC range: 0.25-1 ug/mL). Follow-up cultures were no growth starting from day 3 stool cultures. Microbiome changes included overgrowth of Actinobacteria and/or Firmicute phylum species while on therapy.

Conclusion

Favorable clinical efficacy and safety results were observed in ibezapolstat patients with CDI including 100% clinical cure and sustained clinical cure. These results begin to validate our approach to ibezapolstat development in that the favorable microbiome effects seen in healthy Phase 1 volunteers may be predictive of beneficial patient outcomes, including low rates of recurrence. These results support the continued clinical development of ibezapolstat.

Disclosures

Kevin W. Garey, Pharm.D., M.S., FASHP, Summit Therapeutics (Research Grant or Support) Michael Silverman, MD, Acurx Pharmaceuticals (Consultant)

18. Global Surveillance of Clostridioides difficile Demonstrates High Prevalence in Non-Healthcare Settings

Background

Clostridioides difficile is a Gram-positive, spore-forming, toxin-producing organism that is the leading cause of healthcare-associated infections. However, past studies have isolated C. difficile spores from the community, suggesting an environmental reservoir that may play a role in transmission. This study aimed to examine the prevalence and strain types of C. difficile isolated from the United States (US) and internationally.

Methods

From 2014 to 2017, environmental swabs were collected from public areas, healthcare settings, and shoe soles. Samples were considered positive for C. difficile following growth on CCFA plates and confirmatory PCR testing for toxin genes and fluorescent PCR ribotyping (RT). The rate of C. difficile positivity and associated RT distribution were compared between settings, including shoe soles which were investigated for their potential role in environmental transmission.

Results

A total of 11,986 unique isolates were obtained primarily from the US (n=11,002; 92%) in addition to 11 other countries including Taiwan (n=200) and India (n=187). Samples were categorized as being from outdoor environments (n=2,992), private residences (n=2,772), shoe soles (n=1,420), public buildings (n=1,104) or acute care settings (n=3,698). Worldwide C. difficile sample positivity was 26% and was similar between US and non-US sampling sites. In the US, private residences (26.2%) and outdoor environments (24.1%) had the highest positivity rate compared to public buildings (17.2%). In a Texas sub-analysis (n=8,571), positivity rates were highest from outdoor samples (27%) and were similar between private residences (24%) and healthcare buildings (24%). The most prevalent RTs overall were F014-020 (16.4%), F106 (14.9%), and FP310 (11%). Shoe soles had the highest positivity rate (45%) with similar RT distribution between shoe soles and environmental samples.

Conclusion

Using a worldwide sample, 26% of environmental samples tested positive for toxigenic C. difficile strains from healthcare and non-healthcare sites. Community stewardship efforts will be needed to reduce the risk of CDI in vulnerable patients. Shoe sole sampling may be an ideal surveillance tool to test for emerging epidemic strains.

Disclosures

Kevin W. Garey, Pharm.D., M.S., FASHP, Summit Therapeutics (Research Grant or Support)

Integrating gut microbiome and host immune markers to understand the pathogenesis of Clostridioides difficile infection

Clostridioides difficile (C.difficile) infection is the most common cause of healthcare-associated infection and an important cause of morbidity and mortality among hospitalized patients. A comprehensive understanding of C.difficile infection (CDI) pathogenesis is crucial for disease diagnosis, treatment, and prevention. Here, we characterized gut microbial compositions and a broad panel of innate and adaptive immunological markers in 243 well-characterized human subjects (including 187 subjects with both microbiota and immune marker data), who were divided into four phenotype groups: CDI, Asymptomatic Carriage, Non-CDI Diarrhea, and Control. We found that the interactions between gut microbiota and host immune markers are very sensitive to the status of C.difficile colonization and infection. We demonstrated that incorporating both gut microbiome and host immune marker data into classification models can better distinguish CDI from other groups than can either type of data alone. Our classification models display robust diagnostic performance to differentiate CDI from Asymptomatic carriage (AUC~0.916), Non-CDI Diarrhea (AUC~0.917), or Non-CDI that combines all other three groups (AUC~0.929). Finally, we performed symbolic classification using selected features to derive simple mathematic formulas that explicitly quantify the interactions between the gut microbiome and host immune markers. These findings support the potential roles of gut microbiota and host immune markers in the pathogenesis of CDI. Our study provides new insights for a microbiome-immune marker-derived signature to diagnose CDI and design therapeutic strategies for CDI.

Antibiotic Therapies for Clostridioides difficile Infection in Children

While rates of Clostridioides difficile infection (CDI) are increasing among children in the United States, studies assessing CDI treatment in children are severely lacking. Thus, treatment guidelines have historically relied on evidence from limited observational data in children and randomized controlled trials (RCTs) conducted in adults to form recommendations. Currently, the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) recommend metronidazole and/or vancomycin for pediatric CDI depending on disease severity. Recently however, the first and only RCT of CDI treatment in children demonstrated fidaxomicin to be non-inferior to vancomycin, proving its safety and efficacy in this population. Additionally, observational data published since the IDSA/SHEA guidelines were released suggest metronidazole has lower rates of clinical improvement when compared to vancomycin in hospitalized children with non-severe CDI. Given these recent publications, fidaxomicin and vancomycin, instead of metronidazole, appear to be more appropriate, evidence-based options for the treatment of CDI in children.

Corticosteroids Do Not Increase the Likelihood of Primary Clostridioides difficile Infection in the Setting of Broad-Spectrum Antibiotic Use

Background

The pathogenesis of Clostridioides difficile infection (CDI) involves a significant host immune response. Generally, corticosteroids act by suppressing the host inflammatory response, and their anti-inflammatory effects are used to treat gastrointestinal disorders. Although previous investigations have demonstrated mixed results regarding the effect of corticosteroids on CDI, we hypothesized that the anti-inflammatory effect of corticosteroids would decrease the risk of CDI in hospitalized patients.

Methods

This was a case–control study of hospitalized adults. The case population included patients diagnosed with primary CDI who received at least 1 dose of a high-risk antibiotic (cefepime, meropenem, or piperacillin-tazobactam) in the 90 days before CDI diagnosis. The control population included patients who received at least 1 dose of the same high-risk antibiotic but did not develop CDI in the 90 days following their first dose of antibiotic. The primary study outcome was the development of CDI based on receipt of corticosteroids.

Results

The final study cohort consisted of 104 cases and 153 controls. Those who received corticosteroids had a lower odds of CDI after adjusting for age, proton pump inhibitor use, and antibiotic days of therapy (odds ratio, 0.54; 95% CI, 0.30–0.97; P = .04). We did not observe an association between corticosteroid dose or duration and CDI.

Conclusions

We demonstrated a 46% relative reduction in the odds of developing CDI in patients who received corticosteroids in the past 90 days. We believe that our results provide the best clinical evidence to further support mechanistic studies underlying this phenomenon.

Ultrasensitive and quantitative toxin measurement correlates with baseline severity, severe outcomes, and recurrence among hospitalized patients with Clostridioides difficile infection

BACKGROUND

Stool toxin concentrations may impact Clostridioides difficile infection (CDI) severity and outcomes. We correlated fecal C. difficile toxin concentrations, measured by an ultrasensitive and quantitative assay, with CDI baseline severity, attributable outcomes, and recurrence.

METHODS

We enrolled 615 hospitalized adults (≥ 18y) with CDI (acute diarrhea, positive stool NAAT, and decision to treat). Baseline stool toxin A and B concentrations were measured by Single Molecule Array. Subjects were classified by baseline CDI severity (four scoring methods) and outcomes within 40 days (death, ICU stay, colectomy, and recurrence).

RESULTS

Among 615 patients (median 68.0 years), in all scoring systems, subjects with severe baseline disease had higher stool toxin A+B concentrations than those without (P<0.01). Nineteen subjects (3.1%) had a severe outcome primarily-attributed to CDI (group 1). This group had higher median toxin A+B [14,303 pg/mL (IQR 416.0, 141,967)] than subjects in whom CDI only contributed to the outcome [group 2, 163.2 pg/mL(0.0, 8423.3)], subjects with severe outcome unrelated to CDI [group 3, 158.6 pg/mL (0.0, 1795.2)], or no severe outcome [group 4, 209.5 pg/mL (0.0, 8566.3)](P=0.003). Group 1 was more likely to have detectable toxin (94.7%) than groups 2-4 (60.5-66.1%)(P=0.02). Individuals with recurrence had higher toxin A+B [2266.8 pg/mL(188.8, 29411)] than those without [154.0 pg/mL(0.0, 5864.3)](P<0.001) and higher rates of detectable toxin (85.7% versus 64.0%, P=0.004).

CONCLUSIONS

In CDI patients, ultrasensitive stool toxin detection and concentration correlated with severe baseline disease, severe CDI-attributable outcomes, and recurrence, confirming the contribution of toxin quantity to disease presentation and clinical course.

Clinical Practice Guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 Focused Update Guidelines on Management of Clostridioides difficile Infection in Adults

This clinical practice guideline is a focused update on management of Clostridioides difficile infection (CDI) in adults specifically addressing the use of fidaxomicin and bezlotoxumab for the treatment of CDI. This guideline was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). This guideline is intended for use by healthcare professionals who care for adults with CDI, including specialists in infectious diseases, gastroenterologists, hospitalists, pharmacists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the management CDI are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the management of CDI in adults. The panel followed a systematic process which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development, and Evaluation). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Comparative clinical outcomes evaluation of hospitalized patients infected with Clostridioides difficile ribotype 106 vs. other toxigenic strains

BACKGROUND

Although Clostridioides difficile surveillance often identifies emerging strains, clinical outcome evaluations are rarely performed. Ribotype (RT) 106 is a commonly isolated C. difficile strain worldwide; however, studies investigating RT 106 clinical outcomes are limited. The purpose of this study was to investigate clinical outcomes of RT 106 infections compared with two other endemic strains of varying virulence.

METHODS

This multicenter study evaluated adults hospitalized with C. difficile infection (CDI). C. difficile samples underwent PCR ribotyping and patients infected with RT 106 were compared to patients infected with a known hypervirulent strain (RT 027) and a strain associated with less virulence (RT 014-020). Electronic medical records were reviewed by blinded investigators to assess the primary outcome of poor clinical outcome (composite of initial clinical failure, discharge to a higher level of care, 90-day CDI recurrence, and CDI-contributable mortality).

RESULTS

A total of 396 patients with CDI were identified (RT 106, 32.3%; RT 027, 29.3%; RT 014-020, 38.3%). Patients infected with RT 014-020 less often experienced a poor clinical outcome (40%) compared with RT 106 (56%) and RT 027 (65%) infection (P < 0.0001). After controlling for covariates and using RT 014-020 as a comparator, patients infected with RT 106 (OR, 2.25; 95% CI, 1.36-3.73) or RT 027 (OR, 2.56; 95% CI, 1.52-4.31) had higher odds of poor clinical outcome. Using RT 027 as the comparator, only RT 014-020 was associated with lower odds of poor clinical outcome (OR, 0.42; 95% CI, 0.27-0.65).

CONCLUSION

This study demonstrated that the emergent C. difficile RT 106 was associated with increased rates of poor clinical outcomes compared to RT 014-020 and comparable poor clinical outcomes to RT 027. These findings can help to better understand the clinical significance of this and future emerging ribotypes.

Significant Publications on Infectious Diseases Pharmacotherapy in 2020

Purpose. To summarize the most highly esteemed, peer-reviewed, infectious diseases (ID) pharmacotherapy articles published in 2020. Summary. Members of the Houston Infectious Diseases Network (HIDN) nominated articles that were deemed to have noteworthy contributions to ID pharmacotherapy in 2020, including those on coronavirus disease 2019 (COVID-19) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). To select the most significant articles of 2020, a survey was created and distributed to members of the Society of Infectious Diseases Pharmacists (SIDP) to vote on their top 10 articles of general ID and COVID-19 pharmacotherapy and one noteworthy HIV/AIDS publication. A total of 40 articles were nominated by HIDN: 35 articles pertaining to general ID/COVID-19 pharmacotherapy and 5 articles with HIV/AIDS involvement. Of the 247 SIDP members who responded to the survey, 205 and 42 members voted for general ID/COVID-19 pharmacotherapy articles and HIV/AIDS related articles, respectively. The top publications are summarized. Conclusion. In a taxing year of a global pandemic, the abundant and rapid distribution of ID literature has made it challenging for clinicians to stay informed of significant publications across the ID spectrum. This review summarizes significant ID-related publications in 2020 with the goal of aiding clinicians in staying up to date on the most relevant publications in ID pharmacotherapy.

Reduced Susceptibility to Metronidazole Is Associated With Initial Clinical Failure in Clostridioides difficile Infection

Background

Clinical studies have demonstrated inferior cure rates when metronidazole (MTZ) is used to treat Clostridioides difficile infection (CDI). We hypothesized that a newly identified, heme-inducible form of reduced MTZ susceptibility in C. difficile leads to higher odds of initial clinical failure in patients with CDI treated with MTZ.

Methods

This multicenter cohort study included adults diagnosed with CDI between 2017 and 2018. C. difficile isolated from stool samples underwent agar dilution MTZ susceptibility testing with incorporation of fresh heme. Blinded investigators reviewed medical records for initial clinical failure and other relevant clinical variables. Classification and regression tree (CART) analysis was used to identify the MTZ minimum inhibitory concentration (MIC) breakpoint that was predictive of initial clinical failure. Results were confirmed using univariate and multivariable logistic regression analyses to account for potential confounders.

Results

Of the 356 patients included, 72% received MTZ-based therapy and 27% experienced initial clinical failure. CART analysis identified an MTZ MIC ≥1 µg/mL above which patients had a higher rate of initial clinical failure. MTZ MICs ranged from 0.25 to 8 µg/mL (MIC_50/90 = 0.25/2 µg/mL), and approximately 18% of isolates had MTZ MICs ≥1 µg/mL. In multivariable analysis, an MTZ MIC ≥1 µg/mL was an independent predictor of initial clinical failure in patients receiving an MTZ-based treatment regimen (odds ratio, 2.27 [95% confidence interval, 1.18–4.34]).

Conclusions

Using a reproducible method to determine C. difficile MICs to MTZ, a breakpoint of ≥1 µg/mL identified patients at higher risk of initial clinical failure.

Clinical Practice Guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 Focused Update Guidelines on Management of Clostridioides difficile Infection in Adults

This clinical practice guideline is a focused update on management of Clostridioides difficile infection (CDI) in adults specifically addressing the use of fidaxomicin and bezlotoxumab for the treatment of CDI. This guideline was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). This guideline is intended for use by healthcare professionals who care for adults with CDI, including specialists in infectious diseases, gastroenterologists, hospitalists, pharmacists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the management CDI are based upon evidence derived from topic-specific systematic literature reviews.Summarized below are the recommendations for the management of CDI in adults. The panel followed a systematic process which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Humoral Immune Response to Clostridioides difficile Toxins A and B in Hospitalized Immunocompromised Patients With C difficile Infection

Background

The humoral immune response to Clostridioides difficile toxins in C difficile infection (CDI) is incompletely characterized in immunocompromised hosts (ICHs).

Methods

We conducted a prospective study of hospitalized adults with CDI, with and without immunosuppression (hematologic malignancy, active solid tumor, solid organ or stem cell transplant, inflammatory bowel disease, autoimmune disease, congenital or acquired immunodeficiency, asplenia, chronic receipt of high-dose steroids, or receipt of immunosuppressing medications within 12 months). Serum and stool antibody concentrations of immunoglobulin (Ig)M, IgG, and IgA to C difficile toxins A and B at treatment days 0, 3, and 10–14 were compared.

Results

Ninety-eight subjects (47 ICH; 51 non-ICH) were enrolled. Baseline serum antitoxin A and B antibody levels were similar. At day 3, ICHs demonstrated lower serum levels of antitoxin A IgG, antitoxin A IgA, and antitoxin B IgA (all P < .05). At day 10–14, lower antitoxin A IgG concentrations were observed in ICHs (ICH, 21 enzyme-linked immunosorbent assay [ELISA] units; interquartile range [IQR], 16.4–44.6) compared with non-ICH subjects (49.0 ELISA units; IQR, 21.5–103; P = .045). In stool, we observed lower concentrations of antitoxin B IgA antibodies at baseline and at day 3 for ICH subjects, with a notable difference in concentrations of antitoxin B IgA at day 3 (ICH, 6.7 ELISA units [IQR, 1.9–13.9] compared with non-ICH, 18.1 ELISA units [IQR, 4.9–31.7]; P = .003).

Conclusions

The ICHs with CDI demonstrated lower levels of C difficile antitoxin antibodies in serum and stool during early CDI therapy compared with non-ICHs. These data provide insight into the humoral response to CDI in ICHs.

Systems biology evaluation of refractory Clostridioides difficile infection including multiple failures of fecal microbiota transplantation

BACKGROUND

Fecal microbiota transplantation (FMT) aims to cure Clostridioides difficile infection (CDI) through reestablishing a healthy microbiome and restoring colonization resistance. Although often effective after one infusion, patients with continued microbiome disruptions may require multiple FMTs. In this N-of-1 study, we use a systems biology approach to evaluate CDI in a patient receiving chronic suppressive antibiotics with four failed FMTs over two years.

METHODS

Seven stool samples were obtained between 2016-18 while the patient underwent five FMTs. Stool samples were cultured for C. difficile and underwent microbial characterization and functional gene analysis using shotgun metagenomics. C. difficile isolates were characterized through ribotyping, whole genome sequencing, metabolic pathway analysis, and minimum inhibitory concentration (MIC) determinations.

RESULTS

Growing ten strains from each sample, the index and first four recurrent cultures were single strain ribotype F078-126, the fifth was a mixed culture of ribotypes F002 and F054, and the final culture was ribotype F002. One single nucleotide polymorphism (SNP) variant was identified in the RNA polymerase (RNAP) β-subunit RpoB in the final isolated F078-126 strain when compared to previous F078-126 isolates. This SNV was associated with metabolic shifts but phenotypic differences in fidaxomicin MIC were not observed. Microbiome differences were observed over time during vancomycin therapy and after failed FMTs.

CONCLUSION

This study highlights the importance of antimicrobial stewardship in patients receiving FMT. Continued antibiotics play a destructive role on a transplanted microbiome and applies selection pressure for resistance to the few antibiotics available to treat CDI.

Toxin A-Predominant Pathogenic Clostridioides difficile: A Novel Clinical Phenotype

BACKGROUND

Most Clostridioides difficile toxinogenic strains produce both toxins A and B (A+B+), but toxin A-negative, toxin B-positive (A-B+) variants also cause disease. We report the identification of a series of pathogenic clinical C. difficile isolates that produce high amounts of toxin A with low or nondetectable toxin B.

METHODS

An ultrasensitive, quantitative immunoassay was used to measure toxins A and B in stool samples from 187 C. difficile infection (CDI) patients and 44 carriers. Isolates were cultured and assessed for in vitro toxin production and in vivo phenotypes (mouse CDI model).

RESULTS

There were 7 CDI patients and 6 carriers who had stools with detectable toxin A (TcdA, range 23-17 422 pg/mL; 5.6% of samples overall) but toxin B (TcdB) below the clinical detection limit (<20 pg/mL; median TcdA:B ratio 17.93). Concentrations of toxin A far exceeded B in in vitro cultures of all 12 recovered isolates (median TcdA:B ratio 26). Of 8 toxin A>>B isolates tested in mice, 4 caused diarrhea, and 3 of those 4 caused lethal disease. Ribotyping demonstrated strain diversity. TcdA-predominant samples were also identified at 2 other centers, with similar frequencies (7.5% and 6.8%).

CONCLUSIONS

We report the discovery of clinical pathogenic C. difficile strains that produce high levels of toxin A but minimal or no toxin B. This pattern of toxin production is not rare (>5% of isolates) and is consistently observed in vitro and in vivo in humans and mice. Our study highlights the significance of toxin A in human CDI pathogenesis and has important implications for CDI diagnosis, treatment, and vaccine development.

Recent developments in antimicrobial therapy for gastrointestinal infections

PURPOSE OF REVIEW

This focused, narrative review summarizes human clinical trial data for direct-acting antimicrobials in development for the treatment of gastrointestinal infections that were published in the past 18 months (1 January 2019 to 30 June 2020).

RECENT FINDINGS

Antimicrobial agents for Clostridioides difficile infection (n = 6), cryptosporidiosis (n = 1), cytomegalovirus infection (n = 3) and Helicobacter pylori infection (n = 1) have completed and/or are undergoing human clinical trials.

SUMMARY

Although this review highlights significant advances in four disease states, many common gastrointestinal pathogens have no antimicrobials in human clinical trials, emphasizing the need for continued prioritization in this field of study.

802. Proton Pump Inhibitors Increase Clostridioides difficile Disease Severity Controlling for Infecting Strains

Background

Proton pump inhibitors (PPI) display pleotropic properties that increase the risk of poor outcomes in patients with C. difficile infection (CDI). However, clinical data on PPI and CDI outcomes is controversial perhaps due to lack of knowledge of infecting strain. The purpose of this study was to assess CDI outcomes in hospitalized patients infected with known C. difficile ribotypes based on use of PPI.

Methods

This was a multicenter study (20 hospitals) of hospitalized patients infected with one of three C. difficile ribotypes (RT027, RT106, and RT014-020). Electronic medical records were reviewed by investigators blinded to RT that collected data on PPI use along with other clinical data. A composite endpoint of disease severity, mortality and 90-day CDI recurrence was assessed based on receipt of PPI and ribotype using multivariate logistic regression.

Results

A total of 380 patients with CDI aged 66±17 years (Female: 59.5%; White: 70.5%) infected with RT 106 (115/380; 30.3%), RT027 (116/380; 30.5%), and RT014-020 (149/380; 39.2%) were included. One hundred and ninety-nine patients (52.4%) were given a PPI at the time of CDI diagnosis and 129 patients (66.1%) experienced either severe disease or CDI recurrence. Disease severity differed significantly between ribotypes (p< 0.05) and increased in patients given PPI (p=0.08). CDI recurrence also differed significantly among ribotypes (p< 0.05) and increased in patients given PPI. Using the composite endpoint, receipt of PPIs significantly increased the likelihood of poor outcomes (OR:1.78; 95% CI: 1.17-2.73; p=0.007) after controlling for infecting ribotype.

Conclusion

In this multicenter study, receipt of PPIs increased the likelihood of poor outcomes in CDI patients after controlling for infecting ribotype.

Disclosures

Kevin W. Garey, PharmD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator)

784. A Novel Method to Assess Virulence of Clostridioides difficile: Focus on C. difficile Ribotype 106

Background

Clostridioides difficile ribotype (RT) 106 has emerged as one of the most commonly isolated strains in the USA and worldwide. However, studies investigating clinical outcomes associated with this strain are lacking. The purpose of this study was to compare disease severity, clinical cure, and recurrence rates associated with CDI caused by RT106 vs two other comparator strains.

Methods

This multicenter study (20 hospitals) assessed hospitalized patients infected with C. difficile RT106 compared to patients infected with a known hypervirulent strain (RT027) and a strain associated with less virulence (RT014-020). Electronic medical records were reviewed by investigators blinded to RT. Disease severity was calculated using the 2017 IDSA/SHEA guidelines, initial clinical cure was defined as resolution of symptoms by day 6 of treatment, and recurrence assessed 90-days after the initial positive toxin test. All isolates were ribotyped using PCR fluorescent ribotyping.

Results

A total of 380 patients with CDI aged 66 ± 17 years (Female: 59.5%; White: 70.5%) infected with RT 106 (115/380; 30.3%), RT027 (116/380; 30.5%), and RT014-020 (149/380; 39.2%) were included. Approximately half of the patients had severe CDI (47.6%). Disease severity was highest for RT027 (59.3%) followed by RT014-020 (45%), and RT106 (41.2%). Clinical cure rates were lowest for RT027 (74.8%) followed by RT106 (77.8%), and RT014-020 (85.5%). 90-day recurrence rates were highest for RT027 (20.7%) followed by RT106 (13.3%), and RT014-020 (8.7%). Compared to RT014-020, virulence increased with RT106 (OR:1.10; 95% CI: 0.67-1.8) and RT027 (OR: 2.0: 95% CI: 1.2-3.5) was noted.

Conclusion

Our novel analysis method established RT106 as a moderately virulent C. difficile strain vs. comparator ribotypes. This study presents a novel method for comparing clinical outcomes for emerging ribotypes.

Disclosures

Kevin W. Garey, PharmD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator)

645. Absence of Toxemia in Clostridioides difficile infection: Results from Ultrasensitive Toxin Assay of Serum

Background

Clostridioides difficile infection (CDI) is the major cause of hospital-acquired bacterial infectious diarrheacaused by Toxin A (TcdA) and Toxin B (Tcd B), secreted from pathogenic strains of C.difficle bacteria. This infection can vary greatly in symptom severity and presentation. In fulminant CDI, these toxins lead to systemic complications such as toxemia, however, identification of toxemia in CDI patients is extremely rare. We hypothesized that this rarity of detection may be due to low concentrations of circulating toxins in the blood, below the limit of detection of commercially available assays.

Methods

The previously developed Single Molecule Array (Simoa) assay, capable of detecting TcdA and TcdB in stool, was modified for the detection of toxins in serum and applied to a panel of serum samples from patients with confirmed CDI.

Results

Our cohort included 169 patients with a median age of 68 years (IQR 54-78), most with severe CDI and many with severe clinical outcomes attributed to CDI (Table 1). We found no detectable TcdA or TcdB in the serum of our patient cohort despite a wide range of toxin concentrations in paired stool (Figure 1). The detection of toxin may be limited by the interference of anti-toxin anti-bodies circulating in serum. When serum samples were spiked with TcdA and/or TcdBvarying amounts of IgA, IgG or IgM anti-toxin, high serum anti-toxin antibody concentrations were associated with loss of Simoa signal, suggesting substantial inhibition of toxin measurements.

Table 1. Demographics, Baseline Laboratory Values, and Clinical Outcomes for the cohort

Figure 1. Comparison of TcdA and TcdB concentrations, as measured by Simoa, in serum and stool. Clinical cutoffs are shown: stool, 20 pg/ml for TcdA and for TcdB; serum 15.0 pg/ml for TcdA and is 26.7 pg/ml for TcdB. Signals below these cut-offs are below backgrounds and so negative.

Conclusion

In contrast to earlier published findings which reported on the presence of detectable toxin in the serum of a small number of patients with CDI, our work did not support this observation. Although Simoa is highly sensitive for detection of picogram quantities of TcdA or TcdB it was unable to detect either toxin in serum during CDI. This result does not support the hypothesis that toxemia develops even in severe C. difficile infection.

Disclosures

Alice Banz, Ph.D, BioMerieux (Employee) Kevin W. Garey, PharmD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator) Carolyn D. Alonso, MD, FIDSA, Alnylam Pharmaceuticals (Employee)Merck (Research Grant or Support) Ciarán Kelly, MD, Artugen (Consultant)Facile Therapeutics (Consultant)Finch (Consultant)First Light Biosciences (Consultant)Matrivax (Consultant)Merck (Consultant)Vedanta (Consultant)

1197. Inhibitory Effect of Ursodeoxycholic Acid on Clostridioides difficile Growth

Background

Ursodeoxycholic acid (UDCA), a secondary bile acid, inhibits germination and growth of Clostridioides difficile in vitro, but the results from in vivo experiments have been conflicting. We evaluated the effects of UDCA on C. difficile in vitro and in a wax moth, Galleria mellonella model.

Methods

The in vitro growth and germination effects of UDCA on C. difficile were assessed with increased concentration of UDCA (0.001, 0.01, 0.05, and 0.1%). To assess treatment effects of UDCA, C. difficile spores (approximately 1x10^6-8 colony forming units (CFU)) were force fed to G. mellonella larvae treated with UDCA (50 mg/kg/day) 24 hours prior to C. difficile inoculation. Forty G. mellonella larvae were used for each experiment, which was repeated with two distinct strains (R20291 and CD196). Larvae were housed at 37°C and monitored for the next five days for mortality.

Results

In vitro experiment demonstrated inhibition of C. difficile growth at 0.1% concentration (P &lt; 0.001 vs control). Larvae treated with UDCA had a numerically higher survival rate (60% / 24/40) compared to controls (40% / 16/40) but the results were not statistically significant (p=0.14). Identical rates of survival were observed in the control arms for both strains (40%) and similar in the treatment arms (R20291: 70%; CD 196: 50%).

Conclusion

Overall, UDCA shows inhibitory effect of growth and germination of C. difficile in vitro. However, in our G. mellonella model, a single dose of UDCA given prior to infection did not prevent CDI. Further dose dependent, and multiday studies investigating the role of UDCA in CDI is needed to better understand this in vitro / in vivo paradox.

Disclosures

Kevin W. Garey, PharMD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator)

795. Impact of Revised Infectious Diseases Society of America and Society for Healthcare Epidemiology of America Guideline on the Classification of Clostridioides difficile Infection Severity

Background

The Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA) revised their Clostridioides difficile infection (CDI) severity classification criteria in 2017 to include a serum creatinine (SCr) value above a threshold (≥ 1.5 mg/dL) rather than a relative increase from baseline (≥ 1.5 times the premorbid level). To date, these criteria have not been validated and may overestimate the number of severe CDI cases in patients with underlying renal insufficiency.

Methods

This multicenter, retrospective cohort study included all patients ≥ 18 years of age with CDI diagnosed in two large health systems in the Houston, Texas area between 2016 and 2018. Patients were assessed for presence of acute kidney injury (AKI) and chronic kidney disease (CKD), defined per the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines, and IDSA/SHEA CDI severity classification criteria per the 2010 and 2017 CDI guidelines. The primary outcome was all-cause inpatient mortality.

Results

The study cohort consisted of 770 CDI episodes from 12 hospitals. A large proportion of episodes occurred in patients with preexisting CKD (36.5%) and concomitant AKI (29.6%). Eighty-two episodes (10.6%) showed discordant results when applying the 2017 revised severity classification criteria due to the identification of patients with preexisting CKD. However, the 2017 severity classification criteria were better correlated with all-cause mortality (OR, 5.40; 95% CI, 1.84-15.86; P = 0.002) than were the 2010 severity classification criteria (OR, 3.12; 95% CI, 1.35-7.19; P = 0.008) as the 2017 SCr criterion was an independent predictor of mortality (OR, 3.66; 95% CI, 1.66-8.05; P = 0.001) while the 2010 SCr criterion was not (OR, 1.47; 95% CI, 0.71-3.08; P = 0.30).

Conclusion

Our findings support the inclusion of the 2017 IDSA/SHEA CDI severity classification criteria in future CDI guideline updates.

Disclosures

Kevin W. Garey, PharmD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator)

43. A Pharmacoepidemiologic Evaluation of Echinocandin Use

Background

Invasive candidiasis (IC) is a common healthcare-associated infection. Rates of IC caused by drug-resistant Candida spp., designated by the CDC as a serious threat, are increasing, and Candida auris alone was recently added as an urgent threat. Echinocandins are guideline-preferred for the treatment of invasive candidiasis due to in vitro potency, a favorable toxicity profile, and convenient dosing. The purpose of this study was to perform a pharmacoepidemiologic analysis on patterns of echinocandin use at a large, quaternary care medical center.

Methods

Data reporting echinocandin use, pharmacy data, and clinical microbiologic data obtained from 2017–19 were pooled. Monthly days of therapy (DOT) per 1,000 patient days were calculated during the study period along with number of unique orders. Investigators evaluated the proportion of echinocandin-treated patients with or without positive Candida cultures; the relationship between echinocandin use and hospital admission and discharge dates was also evaluated.

Results

Echinocandin monthly DOT/1,000 patient days present averaged 26 (± 5) DOT and did not change appreciably during the study period. Of the patients with microbiologic evidence of Candida, 842 (51%) received echinocandin courses. Length of echinocandin therapy was significantly longer for patients with positive Candida cultures (5.5 ± 5.9 days) compared to those without positive cultures (3.9 ± 5.0 days; p< 0.001). Of 1,659 echinocandin courses evaluated, 549 courses (33%) were initiated within 2 days of hospital admission and the average time from hospital admission to echinocandin start was 9 (± 13) days. A total of 505 (24%) echinocandin courses were continued until the day of discharge.

Conclusion

The rate of echinocandin use did not change appreciably during the study period. A significant proportion of echinocandin courses were either started upon hospital admission or were continued until the day of discharge. Further studies to evaluate antifungal stewardship opportunities for the echinocandin pharmacologic class are warranted.

Disclosures

Nicholas D. Beyda, PharmD, BCPS, Astellas (Advisor or Review Panel member)Cidara (Grant/Research Support, Scientific Research Study Investigator) Kevin W. Garey, PharMD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator)