Structural Basis of Transcription Inhibition by Fidaxomicin (Lipiarmycin A3).

Fidaxomicin is an antibacterial drug in clinical use for treatment of Clostridium difficile diarrhea. The active ingredient of fidaxomicin, lipiarmycin A3 (Lpm), functions by inhibiting bacterial RNA polymerase (RNAP). Here we report a cryo-EM structure of Mycobacterium tuberculosis RNAP holoenzyme in complex with Lpm at 3.5-Å resolution. The structure shows that Lpm binds at the base of the RNAP "clamp." The structure exhibits an open conformation of the RNAP clamp, suggesting that Lpm traps an open-clamp state. Single-molecule fluorescence resonance energy transfer experiments confirm that Lpm traps an open-clamp state and define effects of Lpm on clamp dynamics. We suggest that Lpm inhibits transcription by trapping an open-clamp state, preventing simultaneous interaction with promoter -10 and -35 elements. The results account for the absence of cross-resistance between Lpm and other RNAP inhibitors, account for structure-activity relationships of Lpm derivatives, and enable structure-based design of improved Lpm derivatives.

The clinical effectiveness of Fidaxomicin compared to Vancomycin in the treatment of Clostridioides difficile infection, a single center real-world experience.

BACKGROUND: The use of fidaxomicin is recommended as first line therapy for all patients with Clostridioides difficile infection (CDI). However, real-world studies have shown conflicting evidence of superiority. METHODS: We conducted a retrospective single center study of patients diagnosed with CDI between 2011-2021. A primary composite outcome of clinical failure, 30-day relapse or CDI-related death was used. A multivariable cause specific Cox proportional hazards model was used to evaluate fidaxomicin compared to vancomycin in preventing the composite outcome. A separate model was fit on a subset of patients with C. difficile ribotypes adjusting for ribotype. RESULTS: There were 598 patients included, of whom 84 received fidaxomicin. The primary outcome occurred in 8 (9.5%) in the fidaxomicin group compared to 111 (21.6%) in the vancomycin group. The adjusted multivariable model showed fidaxomicin was associated with 63% reduction in the risk of the composite outcome compared to vancomycin (HR = 0.37, 95% CI 0.17-0.80). In the 337 patients with ribotype data after adjusting for ribotype 027, the results showing superiority of fidaxomicin were maintained (HR = 0.19, 95% CI 0.05-0.77). CONCLUSION: In the treatment of CDI, we showed that real-world use of fidaxomicin is associated with lower risk of a composite endpoint of treatment failure.

Increase of healthcare-onset Clostridioides difficile infection in adult population since SARS-CoV-2 pandemic: A retrospective cohort study in a tertiary care hospital from 2019 to 2022.

OBJECTIVES: The aim was to assess the impact of the SARS-CoV-2 pandemic on the prevalence, relative incidence (RI), incidence density (ID), ratio of rate incidence (RRI), rate of incidence density (RID), and relative risks (RR) of healthcare-onset Clostridioides difficile infection (HO-CDI) as well as its correlation with the antibiotic consumption. METHODS: Demographic and analytical data of adult patients exhibiting diarrhoea and testing positive for C. difficile were systematically collected from a tertiary care hospital in Madrid (Spain). The periods analysed included: prepandemic (P0), first pandemic-year (P1), and second pandemic-year (P2). We compared global prevalence, RI of HO-CDI per 1,000-admissions, ID of HO-CDI per 10,000-patients-days, RRI, RID, and RR. Antibiotic consumption was obtained by number of defined daily dose per 100 patient-days. RESULTS: In P0, the prevalence of HO-CDI was 7.4% (IC95%: 6.2-8.7); in P1, it increased to 8.7% (IC95%: 7.4-10.1) (p = 0.2), and in P2, it continued to increase to 9.2% (IC95%: 8-10.6) (p < 0.05). During P1, the RRI was 1.5 and RID was 1.4. However, during P2 there was an increase in RRI to 1.6 and RID to 1.6. The RR also reflected the increase in HO-CDI: at P1, the probability of developing HO-CDI was 1.5 times (IC95%: 1.2-1.9) higher than P0, while at P2, this probability increased to 1.6 times (IC95%: 1.3-2.1). There was an increase in prevalence, RI, ID, RR, RRI, and RID during the two postpandemic periods respect to the prepandemic period. During P2, this increase was greater than the P1. Meropenem showed a statistically significant difference increased consumption (p < 0.05) during the pandemic period. Oral vancomycin HO-CDI treatment showed an increase during the period of study (p > 0.05). CONCLUSIONS: Implementation of infection control measures during the SARS-CoV-2 pandemic did not appear to alleviate the burden of HO-CDI. The escalation in HO-CDI cases did not exhibit a correlation with overall antibiotic consumption, except for meropenem.

[Fulminant Clostridioides difficile infection during treatment with FLT3 inhibitor for acute myeloid leukemia].

An 80-year-old man with FLT3-TKD mutation-positive acute myeloid leukemia (AML) relapsed during consolidation therapy with venetoclax/azacitidine and was started on gilteritinib as salvage therapy. On the day after treatment initiation, febrile neutropenia was observed, but the fever resolved promptly after initiation of antimicrobial therapy. On the fifth day after completion of antimicrobial therapy, the patient experienced fever and watery diarrhea over 10 times a day, and a diagnosis of Clostridioides difficile infection (CDI) was made based on stool examination. The patient was treated with intravenous metronidazole, but renal dysfunction, hypotension, and hypoxemia developed, and a CT scan showed pleural and intraperitoneal effusion, significant intestinal wall thickening, and intestinal dilatation. Fidaxomicin was started under general monitoring in the intensive care unit and response was achieved. The patient was discharged from the intensive care unit on the 18th day after the onset of CDI. We report this case not only due to the rarity of fulminant CDI during AML treatment, but also because it is a valuable example of effective treatment of fulminant CDI with fidaxomicin.

Molecular dissection of RbpA-mediated regulation of fidaxomicin sensitivity in mycobacteria.

RNA polymerase (RNAP) binding protein A (RbpA) is essential for mycobacterial viability and regulates transcription initiation by increasing the stability of the RNAP-promoter open complex (RPo). RbpA consists of four domains: an N-terminal tail (NTT), a core domain (CD), a basic linker, and a sigma interaction domain. We have previously shown that truncation of the RbpA NTT and CD increases RPo stabilization by RbpA, implying that these domains inhibit this activity of RbpA. Previously published structural studies showed that the NTT and CD are positioned near multiple RNAP-σA holoenzyme functional domains and predict that the RbpA NTT contributes specific amino acids to the binding site of the antibiotic fidaxomicin (Fdx), which inhibits the formation of the RPo complex. Furthermore, deletion of the NTT results in decreased Mycobacterium smegmatis sensitivity to Fdx, but whether this is caused by a loss in Fdx binding is unknown. We generated a panel of rbpA mutants and found that the RbpA NTT residues predicted to directly interact with Fdx are partially responsible for RbpA-dependent Fdx activity in vitro, while multiple additional RbpA domains contribute to Fdx activity in vivo. Specifically, our results suggest that the RPo-stabilizing activity of RbpA decreases Fdx activity in vivo. In support of the association between RPo stability and Fdx activity, we find that another factor that promotes RPo stability in bacteria, CarD, also impacts to Fdx sensitivity. Our findings highlight how RbpA and other factors may influence RNAP dynamics to affect Fdx sensitivity.

Phenolic Substitution in Fidaxomicin: A Semisynthetic Approach to Antibiotic Activity Across Species.

Fidaxomicin (Fdx) is a natural product antibiotic with potent activity against Clostridioides difficile and other Gram-positive bacteria such as Mycobacterium tuberculosis. Only a few Fdx derivatives have been synthesized and examined for their biological activity in the 50 years since its discovery. Fdx has a well-studied mechanism of action, namely inhibition of the bacterial RNA polymerase. Yet, the targeted organisms harbor different target protein sequences, which poses a challenge for the rational development of new semisynthetic Fdx derivatives. We introduced substituents on the two phenolic hydroxy groups of Fdx and evaluated the resulting trends in antibiotic activity against M. tuberculosis, C. difficile, and the Gram-negative model organism Caulobacter crescentus. As suggested by the target protein structures, we identified the preferable derivatisation site for each organism. The derivative ortho-methyl Fdx also exhibited activity against the Gram-negative C. crescentus wild type, a first for fidaxomicin antibiotics. These insights will guide the synthesis of next-generation fidaxomicin antibiotics.

Fidaxomicin treatment for Clostridioides difficile infection in patients with inflammatory bowel disease.

BACKGROUND AND AIM: Although fidaxomicin is an effective first-line treatment for Clostridioides difficile infection, it has not been well studied in patients with inflammatory bowel disease. We aimed to assess the effectiveness of fidaxomicin for the treatment of C. difficile infection in patients with inflammatory bowel disease. METHODS: This was a multicenter retrospective study of adults with inflammatory bowel disease and C. difficile infection treated with fidaxomicin with at least 3 months of follow up. The primary outcomes were treatment response, defined as resolution of C. difficile infection-attributed diarrhea and/or negative C. difficile infection stool test, and time to C. difficile infection recurrence after fidaxomicin. RESULTS: Thirty-three patients (median age 42 years; 60.6% female) were included. Most patients had ulcerative colitis (26, 78.8%), were receiving treatment with a biologic or small molecule medication (19, 57.6%), and had a prior episode of C. difficile infection (26, 78.8%, median 2 episodes, range 0-15). Fidaxomicin led to resolution of C. difficile infection in 20 (60.6%) patients, with 6/20 (30.0%) developing a recurrence at a median of 55 days. Most patients who failed to respond to fidaxomicin underwent fecal microbiota transplantation (10/13, 76.9%) with resolution. CONCLUSIONS: In this cohort of patients with inflammatory bowel disease and C. difficile infection, 60.6% responded to treatment with fidaxomicin. Of those who did not respond, fecal microbiota transplantation was an effective therapy.

In vitro activity of fidaxomicin and combinations of fidaxomicin with other antibiotics against Clostridium perfringens strains isolated from dogs and cats.

BACKGROUND: Previous studies have demonstrated that fidaxomicin, a macrocyclic lactone antibiotic used to treat recurrent Clostridioides difficile-associated diarrhea, also displays potent in vitro bactericidal activity against Clostridium perfringens strains isolated from humans. However, to date, there is no data on the susceptibility to fidaxomicin of C. perfringens strains of animal origin. On the other hand, although combination therapy has become popular in human and veterinary medicine, limited data are available on the effects of antibiotic combinations on C. perfringens. We studied the in vitro response of 21 C. perfringens strains obtained from dogs and cats to fidaxomicin and combinations of fidaxomicin with six other antibiotics. RESULTS: When tested by an agar dilution method, fidaxomicin minimum inhibitory concentrations (MICs) ranged between 0.004 and 0.032 µg/ml. Moreover, the results of Etest-based combination assays revealed that the incorporation of fidaxomicin into the test medium at a concentration equivalent to half the MIC significantly increased the susceptibility of isolates to metronidazole and erythromycin in 71.4% and 61.9% of the strains, respectively, and the susceptibility to clindamycin, imipenem, levofloxacin, and vancomycin in 42.9-52.4% of the strains. In contrast, » × MIC concentrations of fidaxomicin did not have any effect on levofloxacin and vancomycin MICs and only enhanced the effects of clindamycin, erythromycin, imipenem, and metronidazole in ≤ 23.8% of the tested strains. CONCLUSIONS: The results of this study demonstrate that fidaxomicin is highly effective against C. perfringens strains of canine and feline origin. Although fidaxomicin is currently considered a critically important antimicrobial that has not yet been licensed for veterinary use, we consider that the results reported in this paper provide useful baseline data to track the possible emergence of fidaxomicin resistant strains of C. perfringens in the veterinary setting.

Medicare Prescription Plans Limit Access to Recommended Drugs for Clostridioides difficile Infection.

We analyzed June 2021 Medicare Advantage/Part D enrollment and formulary data. Oral vancomycin and fidaxomicin, frontline Clostridioides difficile treatments, were in the formulary for 100% (42314676 of 42314676) and 84.1% (35598385 of 42314676) of enrollees, respectively. However, they were broadly accessible (formulary, unrestricted, tier 1 or 2) to only 14.4% (6104348 of 42314676) and 1.1% (483004 of 42314676), respectively.

Successful Fidaxomicin Hospital Discharges of Adult Patients With Clostridioides difficile Infections Post-2021 Guidelines: Are Economic Barriers Finally Coming Down?

We reviewed Clostridioides difficile-positive patients discharged on fidaxomicin after local adoption of 2021 C. difficile infection (CDI) guidelines. From 14 June to 3 October 2021, 80% (12/15) had copayments of $0-$35 and 27% (4/15) required prior authorization. The 30-day CDI recurrence was 7%.

Impact of Oral Metronidazole, Vancomycin, and Fidaxomicin on Host Shedding and Environmental Contamination With Clostridioides difficile.

BACKGROUND: Shedding of Clostridioides difficile spores from infected individuals contaminates the hospital environment and contributes to infection transmission. We assessed whether antibiotic selection affects C. difficile shedding and contamination of the hospital environment. METHODS: In this prospective, unblinded, randomized controlled trial of hospitalized adults with C. difficile infection, patients were randomized 1:1:1 to receive fidaxomicin, oral vancomycin, or metronidazole. The primary outcome was change in environmental contamination rate during treatment. Secondary outcomes included stool shedding, total burden of contamination, and molecular relatedness of stool versus environmental C. difficile isolates. RESULTS: Of 33 patients enrolled, 31 (94%) completed the study. Fidaxomicin (-0.36 log10 colony-forming units [CFUs]/d [95% confidence interval (CI), -.52 to -.19]; P < .01) and vancomycin (-0.17 log10 CFUs/d [-.34 to -.01]; P = .05) were associated with more rapid decline in C. difficile shedding than metronidazole (-0.01 log10 CFUs/d [95% CI, -.10 to .08). Both vancomycin (6.3% [95% CI, 4.7-8.3) and fidaxomicin (13.1% [10.7-15.9]) were associated with lower rates of environmental contamination than metronidazole (21.4% [18.0-25.2]). With specific modeling of within-subject change over time, fidaxomicin (adjusted odds ratio, 0.83 [95% CI, .70-.99]; P = .04) was associated with more rapid decline in environmental contamination than vancomycin or metronidazole. Overall, 207 of 233 environmental C. difficile isolates (88.8%) matched patient stool isolates by ribotyping, without significant difference by treatment. CONCLUSIONS: Fidaxomicin, and to a lesser extent vancomycin, reduces C. difficile shedding and contamination of the hospital environment relative to metronidazole. Treatment choice may play a role in reducing healthcare-associated C. difficile transmission. CLINICAL TRIALS REGISTRATION: NCT02057198.

Influence of Binary Toxin Gene Detection and Decreased Susceptibility to Antibiotics among Clostridioides difficile Strains on Disease Severity: a Single-Center Study.

Clostridioides difficile infection (CDI) is the fifth leading cause of death from nonmalignant gastrointestinal disease in the United States. The contribution of resistance to C. difficile-active antibiotics to the outcomes of CDI is unclear. We evaluated the antimicrobial susceptibility of C. difficile isolates in a U.S. hospital and determined associations of clinical variables and binary toxin positivity with antibiotic resistance. C. difficile spores were cultured from fecal specimens of adult patients with CDI for genotyping and antimicrobial susceptibility assay (for clindamycin [CLI], fidaxomicin [FDX], metronidazole [MTZ], moxifloxacin [MXF], tigecycline [TGC], and vancomycin [VAN]). Electronic medical records were reviewed for clinical data extraction. Ninety-seven of 130 (75%) fecal samples grew toxigenic C. difficile in culture. Most of the isolates were tcdA+ tcdB+ cdtB- (80.4%), and 18.6% and 1% were tcdA+ tcdB+ cdtB+ and tcdA-tcdB+ cdtB+, respectively. Susceptibility to VAN, MTZ, FDX, TGC, MXF, and CLI was 96%, 94%, 100%, 100%, 8%, and 79%, respectively. Six isolates, all cdtB positive and belonging to the 027 ribotype, were resistant to VAN and/or MTZ. Higher MICs were found in isolates with a mutation in the VAN-related resistance gene vanR, but not vanS. In addition, cdtB+ isolates exhibited higher MICs of VAN, MTZ, TGC, CLI, and MXF compared to cdtB- strains. Patients with greater intestinal inflammation or severe disease were more likely to be infected with cdtB+ strains. Decreased susceptibility to antibiotics is not directly associated with either severe or recurrent CDI. However, antimicrobial susceptibility of C. difficile is decreased in strains positive for the binary toxin gene.

6S RNA-Dependent Susceptibility to RNA Polymerase Inhibitors.

Bacterial small RNAs (sRNAs) contribute to a variety of regulatory mechanisms that modulate a wide range of pathways, including metabolism, virulence, and antibiotic resistance. We investigated the involvement of sRNAs in rifampicin resistance in the opportunistic pathogen Staphylococcus aureus. Using a competition assay with an sRNA mutant library, we identified 6S RNA as being required for protection against low concentrations of rifampicin, an RNA polymerase (RNAP) inhibitor. This effect applied to rifabutin and fidaxomicin, two other RNAP-targeting antibiotics. 6S RNA is highly conserved in bacteria, and its absence in two other major pathogens, Salmonella enterica and Clostridioides difficile, also impaired susceptibility to RNAP inhibitors. In S. aureus, 6S RNA is produced from an autonomous gene and accumulates in stationary phase. In contrast to what was reported for Escherichia coli, S. aureus 6S RNA does not appear to play a critical role in the transition from exponential to stationary phase but affects σB-regulated expression in prolonged stationary phase. Nevertheless, its protective effect against rifampicin is independent of alternative sigma factor σB activity. Our results suggest that 6S RNA helps maintain RNAP-σA integrity in S. aureus, which could in turn help bacteria withstand low concentrations of RNAP inhibitors.

Real-world comparison of fidaxomicin versus vancomycin or metronidazole in the treatment of Clostridium difficile infection: a systematic review and meta-analysis.

PURPOSE: There is a lack of real-world evidence of the comparative effectiveness of fidaxomicin versus vancomycin or metronidazole for treating patients with Clostridium difficile (CDI) infection. No systematic evidence comparing these treatment regimens using real-world observational studies was published up to date. The goal of this study is to compare the fidaxomicin and vancomycin/metronidazole regimens in terms of treatment outcomes in CDI patients. METHODS: Systematic and comprehensive search was carried out in the following databases and search engines: EMBASE, Cochrane, MEDLINE, ScienceDirect, and Google Scholar from 1954 until January 2022. Newcastle-Ottawa (NO) scale was used to assess the risk of bias. Meta-analysis was carried out using random effects model, and pooled odds ratios (OR) with 95% confidence interval (CI) were reported. RESULTS: A total of 10 studies satisfied the inclusion criteria, most of them were with poorer quality. The pooled OR was 0.40 (95% CI: 0.09-1.68; I2 = 82.4%) for clinical cure and 2.02 (95% CI: 0.36-11.39; I2 = 88.4%) for sustained cure. We reported pooled OR of 0.69 (95% CI: 0.40-1.20; I2 = 65.7%) for the recurrence rate, 2.81 (95% CI: 1.08-7.29; I2 = 70.6%) for the treatment failure, and 0.73 (95% CI: 0.50-1.07; I2 = 0%) for all-cause mortality between patients that received fidaxomicin and vancomycin. The pooled OR was 0.71 (95% CI: 0.05-9.47; I2 = 69.6%) in terms of recurrence between patients receiving fidaxomicin and metronidazole. CONCLUSION: Fidaxomicin and vancomycin/metronidazole regimens did not have significant difference in terms of treatment outcomes, such as clinical cure, sustained cure, recurrence, and all-cause mortality. However, there was significantly higher risk of treatment failure in CDI patients taking fidaxomicin.

Oral fidaxomicin versus vancomycin for the treatment of Clostridioides difficile infection: A systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Fidaxomicin (FDX) has received considerable attention as a novel therapeutic alternative agent to vancomycin (VCM) for Clostridioides difficile infection (CDI). However, the superiority and efficacy profile of FDX are not sufficiently determined by high-quality evidence. This study aimed to clarify the superiority of FDX for CDI treatment through a systematic review and meta-analysis. METHODS: We conducted a meta-analysis of randomized controlled trials (RCTs) which evaluated the efficacy and safety of FDX and VCM in patients with CDI. Electronic databases (PubMed, Cochrane Library, Web of Science, and Clinicaltrials.gov) were searched for studies published until October 15, 2021. The primary endpoint was global cure. The secondary endpoints were clinical cure, recurrence, and adverse event. Risk ratios (RRs), risk differences (RDs), and 95% confidence intervals were calculated using Mantel-Haenszel random-effects model. The risk of bias was assessed using Cochrane Handbook for Systematic Reviews of Interventions and Assessment Criteria. RESULTS: Six RCTs were included in this meta-analysis. Compared to VCM, FDX was associated with significantly higher global cure rates (RR = 1.18, P < 0.00001; RD = 0.11, 95% CI = 0.07-0.16). In addition, clinical cure rates were comparable between FDX and VCM (P = 0.31). FDX was associated with significantly lower recurrence rates compared to VCM (RR = 0.59, P < 0.0001). In addition, adverse event rates were not significantly different between the drugs (P = 0.41). CONCLUSION: FDX achieves significantly higher global cure rates and lower recurrence rates and is comparable to VCM in clinical cure rates and adverse event rates in patients with CDI. Collectively, FDX is superior to VCM as a therapeutic agent for CDI.

Going Retro, Going Viral: Experiences and Lessons in Drug Discovery from COVID-19.

The severity of the COVID-19 pandemic and the pace of its global spread have motivated researchers to opt for repurposing existing drugs against SARS-CoV-2 rather than discover or develop novel ones. For reasons of speed, throughput, and cost-effectiveness, virtual screening campaigns, relying heavily on in silico docking, have dominated published reports. A particular focus as a drug target has been the principal active site (i.e., RNA synthesis) of RNA-dependent RNA polymerase (RdRp), despite the existence of a second, and also indispensable, active site in the same enzyme. Here we report the results of our experimental interrogation of several small-molecule inhibitors, including natural products proposed to be effective by in silico studies. Notably, we find that two antibiotics in clinical use, fidaxomicin and rifabutin, inhibit RNA synthesis by SARS-CoV-2 RdRp in vitro and inhibit viral replication in cell culture. However, our mutagenesis studies contradict the binding sites predicted computationally. We discuss the implications of these and other findings for computational studies predicting the binding of ligands to large and flexible protein complexes and therefore for drug discovery or repurposing efforts utilizing such studies. Finally, we suggest several improvements on such efforts ongoing against SARS-CoV-2 and future pathogens as they arise.

Impact of Revised Infectious Diseases Society of America and Society for Healthcare Epidemiology of America Clinical Practice Guidelines on the Treatment of Clostridium difficile Infections in the United States.

BACKGROUND: Our objective was to determine if oral vancomycin, fidaxomicin, and oral metronidazole use in the United States changed after publication of revised clinical practice guidelines for Clostridium difficile infection (CDI) in February 2018. METHODS: We obtained US antibiotic prescription data (IQVIA) from 2006-August 2019 and used guideline-recommended dosing regimens to estimate monthly numbers of 10-day treatment courses of vancomycin, fidaxomicin and metronidazole. Interrupted time-series analyses were performed, adjusted by month. We compared linear trends for monthly numbers of treatment courses in different time periods. RESULTS: Cumulative treatment courses of oral vancomycin and fidaxomicin increased by 54% (n = 226 166) and 48% (n = 18 518), respectively, in 18 months following guidelines compared with 18 months before; those of oral metronidazole decreased by 3% (n = 238 372). Monthly vancomycin and fidaxomicin use significantly increased throughout the period following revised guidelines (P < .0001 and P = .0002, respectively), whereas that of metronidazole decreased significantly (P < .0001). Monthly vancomycin use increased and metronidazole use decreased to a significantly greater extent after publication of revised guidelines than after publication of clinical trials establishing superiority of vancomycin over metronidazole (P < .0001). CONCLUSIONS: Revised practice guidelines have had a significant impact on CDI treatment in the US. Clinical trial data used for the revised guidelines were available since 2007-2014 and 2011-2012 for oral vancomycin and fidaxomicin, respectively. Guidelines or guidance documents for treating CDI and other infections should be updated in more timely fashion.

A Tapered-pulsed Fidaxomicin Regimen Following Treatment in Patients With Multiple Clostridioides difficile Infection Recurrences.

We treated 46 patients with multiple recurrent Clostridioides difficile infections (mrCDI) using a tapered-pulsed (T-P) fidaxomicin regimen, the majority of whom failed prior T-P vancomycin treatment. Sustained clinical response rates at 30 and 90 days were 74% (34/46) and 61% (28/46). T-P fidaxomicin shows promise for management of mrCDI.

Real-life experience with fidaxomicin in Clostridioides difficile infection: a multicentre cohort study on 244 episodes.

The high cost of fidaxomicin has restricted its use despite the benefit of a lower Clostridioides difficile infection (CDI) recurrence rate at 4 weeks of follow-up. This short follow-up represents the main limitation of pivotal clinical trials of fidaxomicin, and some recent studies question its benefits over vancomycin. Moreover, the main risk factors of recurrence after treatment with fidaxomicin remain unknown. We designed a multicentre retrospective cohort study among four Spanish hospitals to assess the efficacy of fidaxomicin in real life and to investigate risk factors of fidaxomicin failure at weeks 8 and 12. Two-hundred forty-four patients were included. Fidaxomicin was used in 96 patients (39.3%) for a first episode of CDI, in 95 patients (38.9%) for a second episode, and in 53 patients (21.7%) for a third or subsequent episode. Patients treated with fidaxomicin in a first episode were younger (59.9 years vs 73.5 years), but they had more severe episodes (52.1% vs. 32.4%). The recurrence rates for patients treated in the first episode were 6.5% and 9.7% at weeks 8 and 12, respectively. Recurrence rates increased for patients treated at second or ulterior episodes (16.3% and 26.4% at week 8, respectively). Age greater than or equal to 85 years and having had a previous episode of CDI were identified as recurrence risk factors at weeks 8 and 12. We conclude that the outcomes with fidaxomicin in real life are at least as good as those observed in clinical trials despite a more demanding evaluation. Be it 85 years of age or older, and the use after a first episode appears to be independent factors of CDI recurrence after treatment with fidaxomicin.

Safety and Efficacy of Fidaxomicin and Vancomycin in Children and Adolescents with Clostridioides (Clostridium) difficile Infection: A Phase 3, Multicenter, Randomized, Single-blind Clinical Trial (SUNSHINE).

BACKGROUND: Fidaxomicin, a narrow-spectrum antibiotic approved for Clostridioides (Clostridium) difficile infection (CDI) in adults, is associated with lower rates of recurrence than vancomycin; however, pediatric data are limited. This multicenter, investigator-blind, phase 3, parallel-group trial assessed the safety and efficacy of fidaxomicin in children. METHODS: Patients aged <18 years with confirmed CDI were randomized 2:1 to 10 days of treatment with fidaxomicin (suspension or tablets, twice daily) or vancomycin (suspension or tablets, 4 times daily). Safety assessments included treatment-emergent adverse events. The primary efficacy end point was confirmed clinical response (CCR), 2 days after the end of treatment (EOT). Secondary end points included global cure (GC; CCR without CDI recurrence) 30 days after EOT (end of study; EOS). Plasma and stool concentrations of fidaxomicin and its active metabolite OP-1118 were measured. RESULTS: Of 148 patients randomized, 142 were treated (30 <2 years old). The proportion of participants with treatment-emergent adverse events was similar with fidaxomicin (73.5%) and vancomycin (75.0%). Of 3 deaths in the fidaxomicin arm during the study, none were CDI or treatment related. The rate of CCR at 2 days after EOT was 77.6% (76 of 98 patients) with fidaxomicin and 70.5% (31 of 44) with vancomycin, whereas the rate of GC at EOS was significantly higher in participants receiving fidaxomicin (68.4% vs 50.0%; adjusted treatment difference, 18.8%; 95% confidence interval, 1.5%-35.3%). Systemic absorption of fidaxomicin and OP-1118 was minimal, and stool concentrations were high. CONCLUSIONS: Compared with vancomycin, fidaxomicin was well tolerated and demonstrated significantly higher rates of GC in children and adolescents with CDI. CLINICAL TRIALS REGISTRATION: NCT02218372.