In vitro activity of OPT-80 against Clostridium difficile

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Myxopyronin B inhibits growth of a Fidaxomicin-resistant Clostridioides difficile isolate and interferes with toxin synthesis

The anaerobic, gastrointestinal pathogen Clostridioides difficile can cause severe forms of enterocolitis which is mainly mediated by the toxins it produces. The RNA polymerase inhibitor Fidaxomicin is the current gold standard for the therapy of C. difficile infections due to several beneficial features including its ability to suppress toxin synthesis in C. difficile. In contrast to the Rifamycins, Fidaxomicin binds to the RNA polymerase switch region, which is also the binding site for Myxopyronin B. Here, serial broth dilution assays were performed to test the susceptibility of C. difficile and other anaerobes to Myxopyronin B, proving that the natural product is considerably active against C. difficile and that there is no cross-resistance between Fidaxomicin and Myxopyronin B in a Fidaxomicin-resistant C. difficile strain. Moreover, mass spectrometry analysis indicated that Myxopyronin B is able to suppress early phase toxin synthesis in C. difficile to the same degree as Fidaxomicin. Conclusively, Myxopyronin B is proposed as a new lead structure for the design of novel antibiotics for the therapy of C. difficile infections.

Antimicrobial resistance in Clostridioides (Clostridium) difficile derived from humans: a systematic review and meta-analysis

Background

Clostridioides (Clostridium) difficile is an important pathogen of healthcare- associated diarrhea, however, an increase in the occurrence of C. difficile infection (CDI) outside hospital settings has been reported. The accumulation of antimicrobial resistance in C. difficile can increase the risk of CDI development and/or its spread. The limited number of antimicrobials for the treatment of CDI is matter of some concern.

Objectives

In order to summarize the data on antimicrobial resistance to C. difficile derived from humans, a systematic review and meta-analysis were performed.

Methods

We searched five bibliographic databases: (MEDLINE [PubMed], Scopus, Embase, Cochrane Library and Web of Science) for studies that focused on antimicrobial susceptibility testing in C. difficile and were published between 1992 and 2019. The weighted pooled resistance (WPR) for each antimicrobial agent was calculated using a random- effects model.

Results

A total of 111 studies were included. The WPR for metronidazole and vancomycin was 1.0% (95% CI 0–3%) and 1% (95% CI 0–2%) for the breakpoint > 2 mg/L and 0% (95% CI 0%) for breakpoint ≥32 μg/ml. Rifampin and tigecycline had a WPRs of 37.0% (95% CI 18–58%) and 1% (95% CI 0–3%), respectively. The WPRs for the other antimicrobials were as follows: ciprofloxacin 95% (95% CI 85–100%), moxifloxacin 32% (95% CI 25–40%), clindamycin 59% (95% CI 53–65%), amoxicillin/clavulanate 0% (0–0%), piperacillin/tazobactam 0% (0–0%) and ceftriaxone 47% (95% CI 29–65%). Tetracycline had a WPR 20% (95% CI 14–27%) and meropenem showed 0% (95% CI 0–1%); resistance to fidaxomicin was reported in one isolate (0.08%).

Conclusion

Resistance to metronidazole, vancomycin, fidaxomicin, meropenem and piperacillin/tazobactam is reported rarely. From the alternative CDI drug treatments, tigecycline had a lower resistance rate than rifampin. The high-risk antimicrobials for CDI development showed a high level of resistance, the highest was seen in the second generation of fluoroquinolones and clindamycin; amoxicillin/clavulanate showed almost no resistance. Tetracycline resistance was present in one fifth of human clinical C. difficile isolates.

Fidaxomicin for the treatment of Clostridioides difficile in children

Fidaxomicin is an oral narrow-spectrum novel 18-membered macrocyclic antibiotic that was initially approved in 2011 by the US FDA for the treatment of Clostridioides difficile infections (CDI) in adults. In February 2020, the FDA approved fidaxomicin for the treatment of CDI in children age >6 months. In adults, fidaxomicin is as efficacious as vancomycin in treating CDI and reduces the risk of recurrent CDI. An investigator-blinded, randomized, multicenter, multinational clinical trial comparing the efficacy and safety of fidaxomicin with vancomycin in children was recently published confirming similar findings as previously reported in adults. Fidaxomicin is the first FDA-approved treatment for CDI in children and offers a promising option for reducing recurrent CDI in this population.

Ridinilazole for the treatment of Clostridioides difficile infection

INTRODUCTION

Ridinilazole is a novel antibiotic being developed for the treatment of Clostridioides difficile infection (CDI). Ridinilazole has completed two phase II trials and phase III trials which are denoted Ri-CoDIFy 1 and 2, are planned (ClinicalTrials.gov identifiers: NCT03595553 and NCT03595566). Areas covered: This article covers the chemistry, mechanism of action, in vitro microbiology versus C. difficile and host microbiota, pre-clinical and clinical efficacy, pharmacokinetics, pharmacodynamics and safety and tolerability of ridinilazole. Expert opinion: Ridinilazole is a novel antibiotic with ideal properties for the treatment of CDI. Given the promising results from the phase II clinical trial, ridinilazole may have the capability to lower the risk for CDI recurrence thus improving sustained clinical response rates - a current unmet medical need. Assuming a positive phase III trial, ridinilazole will enter a market with heightened awareness on the importance of prevention of CDI. This along with further research into the economic consequences and decreased patient quality of life associated with recurrent CDI, should provide clinicians with further evidence for the need for therapy that limits CDI recurrence and improves sustained clinical cure.

Bacterial Cytological Profiling as a Tool To Study Mechanisms of Action of Antibiotics That Are Active against Acinetobacter baumannii

An increasing number of multidrug-resistant Acinetobacter baumannii (MDR-AB) infections have been reported worldwide, posing a threat to public health. The establishment of methods to elucidate the mechanism of action (MOA) of A. baumannii-specific antibiotics is needed to develop novel antimicrobial therapeutics with activity against MDR-AB We previously developed bacterial cytological profiling (BCP) to understand the MOA of compounds in Escherichia coli and Bacillus subtilis Given how distantly related A. baumannii is to these species, it was unclear to what extent it could be applied. Here, we implemented BCP as an antibiotic MOA discovery platform for A. baumannii We found that the BCP platform can distinguish among six major antibiotic classes and can also subclassify antibiotics that inhibit the same cellular pathway but have different molecular targets. We used BCP to show that the compound NSC145612 inhibits the growth of A. baumannii via targeting RNA transcription. We confirmed this result by isolating and characterizing resistant mutants with mutations in the rpoB gene. Altogether, we conclude that BCP provides a useful tool for MOA studies of antibacterial compounds that are active against A. baumannii.

Fidaxomicin vs Vancomycin for the Treatment of a First Episode of Clostridium Difficile Infection: A Meta-analysis and Systematic Review

Clostridium difficile infection (CDI) continues to possess a significant disease burden in the United States (US) as well as all over the world. Given the increase in severity and recurrence rate, the decrease in cure rate, and the fact that the virulent ribotype 027 strain remains one of the most commonly identified strains in the US, the Infectious Diseases Society of America (IDSA) published a clinical practice guideline in February 2018 moving away from metronidazole as the first-line treatment for initial CDI and recommending either oral vancomycin or fidaxomicin. The aim of this study is to evaluate the clinical data available comparing the efficacy of primary treatment of CDI between those two antibiotics. We performed a PubMed, PubMed Central, and ScienceDirect database search without restriction to regions, publication types, or languages. A comprehensive literature search was performed from January 1, 1980 up to March 20, 2018. We used the following keywords in different combinations: Clostridium difficile, Clostridium difficile infection, CDI, C. diff, C. difficile, fidaxomicin, vancomycin, pseudomembranous colitis, and antibiotic-associated colitis. The search was limited to human studies. Data were independently extracted by two reviewers with disagreements resolved by a third author. We pooled an odds ratio (OR) on two primary outcomes: Clinical cure rate and rate of recurrence during the follow-up period. The computer search was also supplemented with manual searches by the authors of the retrieved review articles and primary studies. The search phrase “((Clostridium difficile) AND vancomycin) AND fidaxomicin” had the highest yield results. We identified four observational studies with a total of 2,303 patients with CDI that met our inclusion criteria. Compared with vancomycin, fidaxomicin use was associated with a significantly lower recurrence of CDI with a pooled OR of 0.47 (95% confidence interval (CI), 0.37 - 0.60, I2 = 0). On the other hand, there was no significant association of fidaxomicin use with CDI cure rate compared to vancomycin with a pooled OR of 1.22 (95% CI, 0.93 - 1.60, I2 = 0). In light of the recently updated clinical practice guidelines by the IDSA, our review suggests that fidaxomicin has a more sustained clinical response with a statistically significant lower recurrence rate. Although fidaxomicin appears to be the better drug with statistical significance, its cost-effectiveness continues to be an ongoing controversy. More randomized clinical trials are needed to shed light on this matter to assess if there is any clinical significance in fidaxomicin superiority.

Antimicrobial activity of fidaxomicin against Clostridium difficile clinical isolates in Aichi area in Japan

We evaluated the susceptibility of 100 Japanese Clostridium difficile isolates to fidaxomicin, a new macrocyclic antibiotic. The minimum inhibitory concentration (MIC) range of fidaxomicin was 0.03-0.5 μg/mL, with a MIC for inhibition of 50% (MIC₅₀) of 0.12 μg/mL, and for inhibition of 90% (MIC₉₀) of 0.25 μg/mL. We also evaluated the susceptibilities of the same 100 C. difficile isolates to vancomycin, metronidazole, moxifloxacin, clindamycin, meropenem, and ampicillin. Of all the antibiotics tested, fidaxomicin showed the most potent antimicrobial activity against this group of C. difficile isolates. MIC levels against C. difficile isolates, including those producing binary toxin, did not substantially differ from those previously reported in Europe, North America and Taiwan.

Fecal Microbiota Transplant

Clostridium difficile infection (CDI) has steadily increased in incidence since the 1990s, with an associated increase in recurrence and severity, which has in turn lead to more intensive care unit (ICU) admissions. The development of recurrent CDI, in particular, has been associated with increasing patient morbidity and mortality as well as an immense financial burden on the health care system. Recently, fecal microbiota transplantation (FMT) has received much publicity as an effective means of treatment for recurrent CDI. The goal of this review is to provide evidence-based recommendations for the diagnosis and management of CDI, with a particular focus on FMT and its utilization in the ICU.

Fidaxomicin--the new drug for Clostridium difficile infection

Clostridium difficile is one of the many aetiological agents of antibiotic associated diarrhoea and is implicated in 15-25 per cent of the cases. The organism is also involved in the exacearbation of inflammatory bowel disease and extracolonic manifestations. Due to increase in the incidence of C. difficile infection (CDI), emergence of hypervirulent strains, and increased frequency of recurrence, the clinical management of the disease has become important. The management of CDI is based on disease severity, and current antibiotic treatment options are limited to vancomycin or metronidazole in the developing countries. this review article briefly describes important aspects of CDI, and the new drug, fidaxomicin, for its treatment. Fidaxomicin is particularly active against C. difficile and acts by inhibition of RNA synthesis. Clinical trials done to compare the efficacy and safety of fidaxomicin with that of vancomycin in treating CDI concluded that fidaxomicin was non-inferior to vancomycin for treatment of CDI and that there was a significant reduction in recurrences. The bactericidal properties of fidaxomicin make it an ideal alternative for CDI treatment. However, fidaxomicin use should be considered taking into account the potential benefits of the drug, along with the medical requirements of the patient, the risks of treatment and the high cost of fidaxomicin compared to other treatment regimens.

Clostridium difficile colitis: review of the therapeutic approach

Clostridium difficile infection (CDI) is the leading cause of antibiotic-associated and nosocomial infectious diarrhea. Presenting as clostridium difficile colitis, it is a significant cause of morbidity and mortality. Metronidazole is regarded as the agent of choice for CDl therapy and also for the first recurrence in most patients with mild to moderate CDI. Vancomycin is recommended as an initial therapy for patients with severe CDI. With recent Food and Drug Administration-approval fidaxomicin is available for clinical use and is as effective as vancomycin with lower relapse rates. Rifaximin and fecal bacteriotherapy are alternative approaches in patients with severe or refractory CDI, before surgical intervention. Antibiotic research is ongoing to add potential new drugs such as teicoplanin, ramoplanin, fusidic acid, nitazoxanide, rifampin, bacitracin to our armamentarium. Role of toxin-binding agents is still questionable. Monoclonal antibody and intravenous immunoglobulin are still investigational therapies that could be promising options. The ongoing challenges in the treatment of CDI include management of recurrence and presence of resistance strains such as NAP1/BI/027, but early recognition of surgical candidates can potentially decrease mortality in CDI.

The potential for emerging therapeutic options for Clostridium difficile infection

Clostridium difficile is mainly a nosocomial pathogen and is a significant cause of antibiotic-associated diarrhea. It is also implicated in the majority of cases of pseudomembranous colitis. Recently, advancements in next generation sequencing technology (NGS) have highlighted the extent of damage to the gut microbiota caused by broad-spectrum antibiotics, often resulting in C. difficile infection (CDI). Currently the treatment of choice for CDI involves the use of metronidazole and vancomycin. However, recurrence and relapse of CDI, even after rounds of metronidazole/vancomycin administration is a problem that must be addressed. The efficacy of alternative antibiotics such as fidaxomicin, rifaximin, nitazoxanide, ramoplanin and tigecycline, as well as faecal microbiota transplantation has been assessed and some have yielded positive outcomes against C. difficile. Some bacteriocins have also shown promising effects against C. difficile in recent years. In light of this, the potential for emerging treatment options and efficacy of anti-C. difficile vaccines are discussed in this review.

Pan-European longitudinal surveillance of antibiotic resistance among prevalent Clostridium difficile ribotypes

Clostridium difficile infection remains a major healthcare burden. Until the recent introduction of fidaxomicin, antimicrobial treatments were limited to metronidazole and vancomycin. The emergence of epidemic C. difficile PCR ribotype 027 and its potential link to decreased antibiotic susceptibility highlight the lack of large-scale antimicrobial susceptibility and epidemiological data available. We report results of epidemiological and antimicrobial susceptibility investigations of C. difficile isolates collected prior to fidaxomicin introduction, establishing important baseline data. Thirty-nine sites in 22 countries submitted a total of 953 C. difficile isolates for PCR ribotyping, toxin testing, and susceptibility testing to metronidazole, vancomycin, fidaxomicin, rifampicin, moxifloxacin, clindamycin, imipenem, chloramphenicol, and tigecycline. Ninety-nine known ribotypes were identified. Ribotypes 027, 014, 001/072, and 078 were most frequently isolated in line with previous European studies. There was no evidence of resistance to fidaxomicin, and reduced susceptibility to metronidazole and vancomycin was also scarce. Rifampicin, moxifloxacin, and clindamycin resistance (13%, 40%, and 50% of total isolates, respectively) were evident in multiple ribotypes. There was a significant correlation between lack of ribotype diversity and greater antimicrobial resistance (measured by cumulative resistance score). Well-known epidemic ribotypes 027 and 001/072 were associated with multiple antimicrobial resistance, but high levels of resistance were also observed, particularly in 018 and closely related emergent ribotype 356 in Italy. This raises the possibility of antimicrobial exposure as the underlying reason for their appearance, and highlights the need for ongoing epidemiological and antimicrobial resistance surveillance.

Clinical efficacy of fidaxomicin compared with vancomycin and metronidazole in Clostridium difficile infections: a meta-analysis and indirect treatment comparison

OBJECTIVES

To evaluate the efficacy of fidaxomicin treatment, which has a limited effect on the normal gut flora, compared with vancomycin and metronidazole treatment in Clostridium difficile infections (CDIs).

METHODS

A systematic literature review was conducted in July to August 2011 and updated in July 2013. For fidaxomicin versus vancomycin, efficacy was evaluated using meta-analysis of data from two Phase III direct comparative studies (n = 1164). As there were no studies comparing fidaxomicin and metronidazole, an indirect comparison was made using data from three vancomycin versus metronidazole studies (n = 345), using the methodology of Bucher et al. (J Clin Epidemiol 1997; 50: 683-91). This provides an OR for the indirect comparison of fidaxomicin versus metronidazole when direct evidence of fidaxomicin versus vancomycin and vancomycin versus metronidazole is available.

RESULTS

Clinical cure rates were similar for fidaxomicin and vancomycin; the OR (95% CI) was 1.17 (0.82, 1.66). Recurrence [0.47 (0.34, 0.65)] was significantly lower and sustained cure rates [1.75 (1.35, 2.27)] significantly higher for fidaxomicin than vancomycin. Similar results were obtained in patient subgroups with severe CDI and with non-severe CDI. From the indirect comparison, the likelihood of recurrence [0.42 (0.18, 0.96)] and sustained cure [2.55 (1.44, 4.51)] were significantly improved for fidaxomicin versus metronidazole. Again, similar results were obtained in those with severe and non-severe CDI.

CONCLUSIONS

Fidaxomicin provides improved sustained cure rates in patients with CDI compared with vancomycin. An indirect comparison indicates that the same is also true for fidaxomicin versus metronidazole. In view of these data, fidaxomicin may be considered as first-line therapy for CDI.

Role of fidaxomicin for the treatment of Clostridium difficile infection

Clostridium difficile is a gram-negative, anaerobic, spore-forming emerging pathogen within health care systems and community-based populations that has a high associated morbidity and mortality as well as cost for the health care system. Recent studies reported high rates of recurrence thus a need for new pharmacological agents to treat C difficile infections (CDIs). Fidaxomicin is a novel macrocyclic antibiotic, originally isolated from fermentation broth of Dactylosporangium aurantiacum spp Hamdenensis, with selective spectrum, unique pharmacokinetic and pharmacodynamics profile, adverse effect profile, efficacy, and role in the treatment of and time to recurrent CDI. Fidaxomicin data have similar clinical cure, when compared to vancomycin, with lower recurrence rates and higher global cure rates in non-BI/NAP1/027 strains. Fidaxomicin also lacks activity against gram-negative bacteria; hence, its potential effect on resistance development among enteric bacteria appears to be low. It appears to have minimal need for renal or hepatic adjustments and minimal concerns for drug-drug interactions. Overall, fidaxomicin has been generally well tolerated with the most common adverse effects reported as mild gastrointestinal complaints. Fidaxomicin appears to have a role in the treatment of CDI with potential lower rates of recurrence, especially in patients with severe disease or risk factors for recurrent CDI.

New developments in chemotherapeutic options for Clostridium difficile colitis

PURPOSE OF REVIEW

Clostridium difficile infections (CDIs) are of increasing concern in healthcare due to increasing incidence as well as suboptimal response to standard therapies. This review focuses on current updates in chemotherapeutic treatment options for primary CDI as well as for relapse.

RECENT FINDINGS

Metronidazole and vancomycin remain the standard therapy for mild and severe CDI, respectively. Fidaxomicin was approved for use in CDI by the US Food and Drug Administration in 2011 and new studies have shown a decreased rate of recurrence as compared with vancomycin as well as potential promise for use as a chaser. Rifaximin may be useful in salvage therapy for recurrent CDI as well as for a chaser. Tigecycline, teicoplanin, doxycycline, linezolid, nitazoxanide, amixicile, LFF571, and CB-183 315 have in-vitro activity and are under different stages of study. Monoclonal antitoxin antibodies for prevention of relapse of CDI are currently under evaluation in a phase 3 clinical trial.

SUMMARY

A variety of promising new treatment options for Clostridium difficile are under development, although further studies are necessary to determine the efficacy of these newer treatments for cure and preventing disease relapse.

Clostridium difficile infection: management strategies for a difficult disease

Clostridium difficile was first described as a cause of diarrhea in 1978 and in the last three decades has reached an epidemic state with increasing incidence and severity in both healthcare and community settings. There also has been a rise in severe outcomes from C. difficile infection (CDI). There have been tremendous advancements in the field of CDI with the identification of newer risk factors, recognition of CDI in populations previously thought not at risk and development of better diagnostic modalities. Several treatment options are available for CDI apart from metronidazole and vancomycin, and include new drugs such as fidaxomicin and other options such as fecal microbiota transplantation. This review discusses the epidemiology, risk factors and outcomes from CDI, and focuses primarily on existing and evolving treatment modalities.

Treatment of Clostridium difficile infection: recent trial results

Clostridium difficile is a major cause of infection worldwide and is associated with increasing morbidity and mortality in vulnerable patient populations. Metronidazole and oral vancomycin are the currently recommended therapies for the treatment of C. difficile infection (CDI) but are associated with unacceptably high rates of disease recurrence. Novel therapies for the treatment of CDI and prevention of recurrent CDI are urgently needed. Important developments in the treatment of CDI are currently underway and include: novel antibacterial agents with narrower antimicrobial spectra of activity, manipulation of the gut microbiota and enhancement of the host antibody immune response.

Cost-effectiveness analysis evaluating fidaxomicin versus oral vancomycin for the treatment of Clostridium difficile infection in the United States

OBJECTIVES

Fidaxomicin is a novel treatment for Clostridium difficile infections (CDIs). This new treatment, however, is associated with a higher acquisition cost compared with alternatives. The objective of this study was to evaluate the cost-effectiveness of fidaxomicin or oral vancomycin for the treatment of CDIs.

METHODS

We performed a cost-utility analysis comparing fidaxomicin with oral vancomycin for the treatment of CDIs in the United States by creating a decision analytic model from the third-party payer perspective.

RESULTS

The incremental cost-effectiveness ratio with fidaxomicin compared with oral vancomycin was $67,576/quality-adjusted life-year. A probabilistic Monte Carlo sensitivity analysis showed that fidaxomicin had an 80.2% chance of being cost-effective at a willingness-to-pay threshold of $100,000/quality-adjusted life-year. Fidaxomicin remained cost-effective under all fluctuations of both fidaxomicin and oral vancomycin costs. The decision analytic model was sensitive to variations in clinical cure and recurrence rates. Secondary analyses revealed that fidaxomicin was cost-effective in patients receiving concominant antimicrobials, in patients with mild to moderate CDIs, and when compared with oral metronidazole in patients with mild to moderate disease. Fidaxomicin was dominated by oral vancomycin if CDI was caused by the NAP1/Bl/027 Clostridium difficile strain and was dominant in institutions that did not compound oral vancomycin.

CONCLUSION

Results of our model showed that fidaxomicin may be a more cost-effective option for the treatment of CDIs when compared with oral vancomycin under most scenarios tested.

Antimicrobial activities of fidaxomicin

Fidaxomicin is bactericidal against Clostridium difficile. The combined results of 8 in vitro studies of 1323 C. difficile isolates showed the minimum inhibitory concentration (MIC) range of fidaxomicin to be ≤0.001–1 μg/mL, with a maximum MIC for inhibition of 90% of organisms (MIC₉₀) of 0.5 μg/mL. Isolates from 2 phase III clinical trials demonstrated that fidaxomicin MICs of baseline isolates did not predict clinical cure, failure, or recurrence of C. difficile infections. No resistance to fidaxomicin developed during treatment in either study, although a single strain recovered from a cured patient had an elevated MIC of 16 µg/mL at the time of recurrence. For 135 strains, OP-1118, a major metabolite, had an MIC for inhibition of 50% of organisms of 4 μg/mL and an MIC₉₀ of 8 μg/mL. Changes in inoculum size (10²–10⁵ colony-forming units/spot) or cation concentrations of calcium or magnesium appeared to have no effect on fidaxomicin MICs. Fidaxomicin has little or no activity against gram-negative aerobes and anaerobes or yeast.

Fidaxomicin versus vancomycin for Clostridium difficile infection: meta-analysis of pivotal randomized controlled trials

Two recently completed phase 3 trials (003 and 004) showed fidaxomicin to be noninferior to vancomycin for curing Clostridium difficile infection (CDI) and superior for reducing CDI recurrences. In both studies, adults with active CDI were randomized to receive blinded fidaxomicin 200 mg twice daily or vancomycin 125 mg 4 times a day for 10 days. Post hoc exploratory intent-to-treat (ITT) time-to-event analyses were undertaken on the combined study 003 and 004 data, using fixed-effects meta-analysis and Cox regression models. ITT analysis of the combined 003/004 data for 1164 patients showed that fidaxomicin reduced persistent diarrhea, recurrence, or death by 40% (95% confidence interval [CI], 26%–51%; P < .0001) compared with vancomycin through day 40. A 37% (95% CI, 2%–60%; P = .037) reduction in persistent diarrhea or death was evident through day 12 (heterogeneity P = .50 vs 13–40 days), driven by 7 (1.2%) fidaxomicin versus 17 (2.9%) vancomycin deaths at <12 days. Low albumin level, low eosinophil count, and CDI treatment preenrollment were risk factors for persistent diarrhea or death at 12 days, and CDI in the previous 3 months was a risk factor for recurrence (all P < .01). Fidaxomicin has the potential to substantially improve outcomes from CDI.

Clostridium difficile infection: new insights into management

Clostridium difficile was first described as a cause of diarrhea in 1978 and is now among the leading 3 hospital-acquired infections in the United States, along with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. In the past 2 decades, there has been an increase in the incidence, severity, and recurrence rates of C difficile infection, all of which are associated with poor outcomes. In addition, several novel risk factors and newer treatment methods are emerging, including fidaxomicin therapy, treatment using monoclonal antibodies, and fecal microbiota transplantation, that have shown promise for the treatment of C difficile infection. This review focuses on the changing epidemiology, risk factors, and newer methods for treatment of C difficile infection.

Safety and efficacy of fidaxomicin in the treatment of Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) is the most common cause of healthcare-associated diarrhea. The current recommended treatment regimens of metronidazole and vancomycin have not changed in nearly 25 years. Fidaxomicin, an exceedingly narrow spectrum macrolide antibiotic, was recently approved for the treatment of CDAD. In phase III clinical trials, fidaxomicin was noninferior to vancomycin in achieving clinical cure of CDAD. Furthermore, fidaxomicin was associated with fewer recurrences of CDAD compared with vancomycin in clinical trials. These results, combined with the ease of administration and a good safety profile, make fidaxomicin an attractive treatment option for treating CDAD.

Clostridium difficile: novel insights on an incessantly challenging disease

PURPOSE OF REVIEW

This review comprises recent insights on epidemiology, risk factors, diagnostic approaches, pathophysiologic mechanisms, novel treatment options and prevention strategies of Clostridium difficile infection (CDI).

RECENT FINDINGS

Incidence of Clostridium difficile continues to rise and hypervirulent subtypes such as polymerase chain reaction (PCR) ribotype 027 and 078 have emerged worldwide. Children and postpartum women are increasingly recognized as being at risk for development of CDI and community-associated infection is no longer rare. PCR technology may replace complicated two-step test algorithms in the future, because it is rapid, sensitive and specific. Pathophysiological studies have provided evidence that either one of the two exotoxins A and B is important in conferring virulence - the role of binary toxin requires further investigation. Proton pump inhibitors are now established as important risk factors for acquiring, complicating CDI, and developing recurrences. Fidaxomycin, monoclonal antibodies and intestinal microbiota transplantation are promising new treatment options, especially regarding prevention of recurrent disease. Future prevention strategies involve vaccination and novel insights on reservoirs for ongoing transmission, including the food chain.

SUMMARY

Important advances in research on CDI include novel diagnostic approaches, better understanding of the underlying pathophysiological mechanisms of disease and the development of new approaches to treatment.

Fidaxomicin: a novel macrocyclic antibiotic for the treatment of Clostridium difficile infection

PURPOSE

The pharmacology, clinical efficacy, safety, dosage and administration, and place in therapy of fidaxomicin for the treatment of Clostridium difficile infection (CDI) are reviewed.

SUMMARY

Fidaxomicin, a macrocyclic antibiotic, has a narrow spectrum of activity against gram-positive anaerobes and is bactericidal against C. difficile. It has no activity against gram-negative bacteria. Fidaxomicin has minimal activity against Bacteroides species, which may be advantageous in maintaining colonization resistance and protecting the gastrointestinal tract from colonization by C. difficile. The minimum inhibitory concentration for 90% of organisms for fidaxomicin against C. difficile ranged from 0.0078 to 2 μg/mL in in vitro studies. After oral administration, fecal concentrations are detected and are directly proportional to the dose administered. Fidaxomicin resistance in vivo has not been reported. In clinical trials, fidaxomicin has been shown to be noninferior to vancomycin in the management of mild-to-moderately severe CDI. The adverse-effect profile of fidaxomicin is comparable to that of vancomycin. The recommended dosage for treatment of CDI is fidaxomicin 200 mg orally twice daily for 10 days. Fidaxomicin should be considered for patients who previously received treatment with metronidazole or vancomycin for CDI and who are diagnosed with recurrent CDI in which a non-NAP1/BI/027 strain is isolated. At institutions where strain typing is not available, fidaxomicin may be considered in patients with recurrent CDI who have not responded to treatment with the regimen used for the first episode of CDI.

CONCLUSION

Fidaxomicin is a well-tolerated agent for the treatment of CDI and has been shown to be noninferior to vancomycin in the management of mild-to-moderately severe CDI.

Fidaxomicin: a macrocyclic antibiotic for the treatment of Clostridium difficile infection

Clostridium difficile is an emerging pathogen in certain health care systems and community-based populations that is associated with high rates of morbidity and mortality, as well as increased costs for the health care system. As recurrence rates increase, new pharmacologic agents to treat C. difficile infection are needed. Fidaxomicin, a novel macrocyclic antibiotic, was recently approved by the United States Food and Drug Administration for the treatment of C. difficile-associated diarrhea. Originally isolated from fermentation broth of Dactylosporangium aurantiacum subspecies hamdenensis, the drug has a selective spectrum, distinctive pharmacokinetic and pharmaco-dynamic properties, and a favorable adverse-effect profile. Fidaxomicin has demonstrated similar clinical cure rates (i.e., resolution of diarrhea) compared with vancomycin, with lower recurrence rates and higher global cure rates (i.e., resolution of diarrhea without recurrence) in non-restriction endonuclease analysis type BI, North American Pulsed Field type 1 (NAP1), polymerase chain reaction ribotype 027 (or non-BI/NAP1/027) strains. Overall, fidaxomicin has been generally well tolerated, with the most common adverse effects reported as mild gastrointestinal complaints. Fidaxomicin appears to be a useful agent in the treatment of severe C. difficile infection, demonstrating decreased rates of recurrence.

Fidaxomicin: first-in-class macrocyclic antibiotic

The incidence of Clostridium difficile has doubled over the past 15 years, and rising mortality rates associated with this infection have followed in its wake. C. difficile infection (CDI) has supplanted methicillin-resistant Staphylococcus aureus as the major cause of nosocomial infection. An insufficient response rate to currently available CDI therapies has prompted the search for new and alternative treatment modalities for this disease. The investigational pipeline includes evaluation of new antimicrobial agents that exhibit good activity against C. difficile without altering normal gut flora, C. difficile toxin-absorbing compounds, and preformed antibodies and vaccines against C. difficile toxin. In two robust clinical trials comparing fidaxomicin to vancomycin in the treatment of CDI, treatment with fidaxomicin demonstrated a superior global cure (cure without recurrence) rate compared with the current gold standard, vancomycin. Fidaxomicin, the first of a new class of macrocyclic antimicrobial agents, represents an advance in the management of CDI.

Clostridium difficile infection: an update on epidemiology, risk factors, and therapeutic options

PURPOSE OF REVIEW

The incidence and severity of Clostridium difficile infection (CDI) around the world has increased over the past 20 years due to the emergence of hypervirulent strains, increased use and misuse of antibiotics, and the increase of susceptible at-risk populations. Treatments currently available for CDI are inadequate to impede the increasing spread and virulence of the infection, avoid recurrence in chronic patients or prevent infection in at-risk populations.

RECENT FINDINGS

New and promising evidence has been presented during the past year, focusing on two major points: preservation of gut microflora and optimization of immune response to CDI and toxins.

SUMMARY

The review aims to summarize the most recent evidence available on the epidemiology, risk factors and treatment of CDI. New antibiotics with selected action on C. difficile and limited effect on microflora (fidaxomicin) and donor fecal transplantation seem to have a relevant efficacy in treating CDI and reducing its recurrence. The use of selected monoclonal antibodies directed against C. difficile toxins in addition to standard therapy is a new, promising approach for the treatment of recurrent cases. Vaccination could be an additional weapon against CDI. New robust data are needed before recommendations can be made to abandon current treatment based on vancomycin and metronidazole and move toward new frontiers.

Fidaxomicin: a novel macrocyclic antibiotic approved for treatment of Clostridium difficile infection

Fidaxomicin, a nonabsorbed macrocyclic compound, is the first antimicrobial agent approved by the FDA for the treatment of Clostridium difficile infection (CDI) in adults over the last 25 years. It is bactericidal, and its mechanism of action relates to inhibition of a RNA polymerase at a site distinct from where rifamycins interact. Fidaxomicin, 200 milligrams by mouth twice daily, is not inferior to vancomycin, 125 milligrams by mouth 4 times daily, for treatment of CDI as determined by clinical response after 10 days of treatment and is superior to vancomycin for sustained response without recurrence 25 days after treatment completion. These results are a significant advance in the treatment of CDI and herald the development of narrow-spectrum anti-C. difficile agents that relatively spare the indigenous fecal microbiota. Continued vigilance for the development of resistance and unanticipated side affects will be important as the drug is introduced into clinical practice.

Effect of new antimicrobial agents on the ecological balance of human microflora

The human normal microflora is relatively stable at each ecological habitat under normal circumstances and acts as a barrier against colonization by potentially pathogenic microorganisms and against overgrowth of already present opportunistic microorganisms. Administration of antimicrobial agents causes disturbances in the ecological balance between the host and the normal microflora. The risk of emergence and spread of resistant strains between patients and dissemination of resistant determinants between microorganisms is reduced if colonization resistance is not disturbed by antimicrobial agents. In this article, the potential ecological effects of administration of new antimicrobial agents on the intestinal and oropharyngeal microflora are summarized. The review is based on clinical studies published during the past 10 years.

Fidaxomicin

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800–322–4349. The November 2011 monograph topics are on indacaterol, brentuximub vedotin, icatibant injection, aflibercept, and centruroides (Scorpion) immune F(ab′)2. The DUE/MUE is on indacaterol.

New target for inhibition of bacterial RNA polymerase: 'switch region'

A new drug target - the 'switch region' - has been identified within bacterial RNA polymerase (RNAP), the enzyme that mediates bacterial RNA synthesis. The new target serves as the binding site for compounds that inhibit bacterial RNA synthesis and kill bacteria. Since the new target is present in most bacterial species, compounds that bind to the new target are active against a broad spectrum of bacterial species. Since the new target is different from targets of other antibacterial agents, compounds that bind to the new target are not cross-resistant with other antibacterial agents. Four antibiotics that function through the new target have been identified: myxopyronin, corallopyronin, ripostatin, and lipiarmycin. This review summarizes the switch region, switch-region inhibitors, and implications for antibacterial drug discovery.

Comparative susceptibilities to fidaxomicin (OPT-80) of isolates collected at baseline, recurrence, and failure from patients in two phase III trials of fidaxomicin against Clostridium difficile infection

A 10-day course of oral fidaxomicin (200 mg twice a day [b.i.d.]), a potent new macrocyclic drug, was compared to vancomycin (125 mg four times a day [q.i.d.]) in 1,164 adults (1,105 in the modified intent-to-treat [mITT] population) with Clostridium difficile infection in two phase III randomized, double-blind trials at sites in North America and 7 European countries. Of 1,105 mITT patients, 792 (71.7%), including 719/999 (72.0%) in the per-protocol (PP) population, provided a C. difficile strain at baseline, of whom 356 received fidaxomicin with 330 cures (92.7%) and 363 received vancomycin with 329 cures (90.6%). The susceptibilities (MIC(90)) of baseline isolates did not predict clinical cure, failure, or recurrence for fidaxomicin (MIC(90), 0.25 μg/ml for both; range, ≤ 0.007 to 1 μg/ml), but there was a one-dilution difference in the MIC(90) (but not the MIC(50)) for vancomycin (MIC(90), 2 μg/ml [range, 0.25 to 8 μg/ml] for cure and 4.0 μg/ml [range, 0.5 to 4 μg/ml] for failures). A total of 65 (7.9%) "rifaximin-resistant" (MIC > 256 μg/ml) strains were isolated in both treatment groups on enrollment, which increased to 25% for failures at the end of therapy. No resistance to either fidaxomicin or vancomycin developed during treatment in either of the phase III studies, although a single strain isolated from a cured patient had an elevated fidaxomicin MIC of 16 μg/ml at the time of recurrence. All isolates were susceptible to ≤ 4 μg/ml of metronidazole. When analyzed by restriction endonuclease analysis (REA) type, 247/719 (34.4%) isolates were BI group isolates, and the MICs were generally higher for all four drugs tested (MIC(90)s: fidaxomicin, 0.5; vancomycin, 2.0; metronidazole, 2.0; and rifaximin, >256 μg/ml) than for the other REA types. There was no correlation between the MIC of a baseline clinical isolate and clinical outcome. MIC(90)s were generally low for fidaxomicin and vancomycin, but BI isolates had higher MICs than other REA group isolates.

The insect peptide coprisin prevents Clostridium difficile-mediated acute inflammation and mucosal damage through selective antimicrobial activity

Clostridium difficile-associated diarrhea and pseudomembranous colitis are typically treated with vancomycin or metronidazole, but recent increases in relapse incidence and the emergence of drug-resistant strains of C. difficile indicate the need for new antibiotics. We previously isolated coprisin, an antibacterial peptide from Copris tripartitus, a Korean dung beetle, and identified a nine-amino-acid peptide in the α-helical region of it (LLCIALRKK) that had antimicrobial activity (J.-S. Hwang et al., Int. J. Pept., 2009, doi:10.1155/2009/136284). Here, we examined whether treatment with a coprisin analogue (a disulfide dimer of the nine peptides) prevented inflammation and mucosal damage in a mouse model of acute gut inflammation established by administration of antibiotics followed by C. difficile infection. In this model, coprisin treatment significantly ameliorated body weight decreases, improved the survival rate, and decreased mucosal damage and proinflammatory cytokine production. In contrast, the coprisin analogue had no apparent antibiotic activity against commensal bacteria, including Lactobacillus and Bifidobacterium, which are known to inhibit the colonization of C. difficile. The exposure of C. difficile to the coprisin analogue caused a marked increase in nuclear propidium iodide (PI) staining, indicating membrane damage; the staining levels were similar to those seen with bacteria treated with a positive control for membrane disruption (EDTA). In contrast, coprisin analogue treatment did not trigger increases in the nuclear PI staining of Bifidobacterium thermophilum. This observation suggests that the antibiotic activity of the coprisin analogue may occur through specific membrane disruption of C. difficile. Thus, these results indicate that the coprisin analogue may prove useful as a therapeutic agent for C. difficile infection-associated inflammatory diarrhea and pseudomembranous colitis.

New advances in the treatment of Clostridium difficile infection (CDI)

Clostridium difficile infections (CDI) have increased in frequency throughout the world. In addition to an increase in frequency, recent CDI epidemics have been linked to a hypervirulent C. difficile strain resulting in greater severity of disease. Although most mild to moderate cases of CDI continue to respond to metronidazole or vancomycin, refractory and recurrent cases of CDI may require alternative therapies. This review provides a brief overview of CDI and summarizes studies involving alternative antibiotics, toxin binders, probiotics, and immunological therapies that can be considered for treatment of acute and recurrent CDI in severe and refractory situations.

Postantibiotic effect of fidaxomicin and its major metabolite, OP-1118, against Clostridium difficile

Fidaxomicin (FDX), a narrow-spectrum antibiotic recently shown to be superior to vancomycin in providing sustained clinical response to Clostridium difficile infection, was investigated along with its major metabolite, OP-1118, with regard to their postantibiotic effects (PAE). FDX was found to have a prolonged PAE (10 h versus ATCC strains and 5.5 h versus a clinical isolate), and OP-1118's PAE was longer than that of the standard comparator, vancomycin (3 versus 0 to 1.5 h, respectively).

Fidaxomicin for the Treatment of Clostridium Difficile Infection in the Pediatric Population - Not Quite So Soon Yet

Fidaxomicin is a new narrow spectrum macrocyclic antibiotic. It inhibits bacterial RNA polymerase and eradicates C difficile with minimal effect on normal intestinal flora. The US FDA granted orphan drug designation for all formulations of fidaxomicin for the treatment of C difficile infections in pediatric patients on January 10, 2011. Fidaxomicin has bactericidal activity against C difficile with a prolonged post-antibiotic effect. Even though this medication has an orphan designation for pediatrics, all the available pharmacokinetic and pharmacodynamic data were in subjects ≥ 18 years old. The MIC₉₀ for fidaxomicin against C. difficile varies from 0.0078 to 0.25 mcg/ml. Fidaxomicin is poorly absorbed. The highest peak plasma concentration in patients treated with fidaxomicin was 0.191 mcg/ml. Fecal levels of fidaxomicin after oral administration are extremely high. The average fecal concentrations in C difficile patients were 255.6 mcg/g, 441.7 mcg/g, and 1443.3 mcg/g in the 100, 200, and 400 mg/day groups, respectively. At a dose of 400 mg/day the average fecal concentration was 5700 times higher than the highest MIC₉₀ of fidaxomicin against C difficile. In a phase III clinical trial fidaxomicin 200 mg twice daily was compared with vancomycin 125 mg four times per day orally for 10 days. Only two patients were 18 years old, and no patients younger than 18 years old participated in the study. The rates of clinical cure with fidaxomicin were noninferior to those with vancomycin. Patients who were infected with non-North American Pulsed Field type 1 strains had fewer recurrences in the fidaxomicin group than patients in the vancomycin group. Side effects were similar between both therapies. Most patients experienced mild gastro-intestinal symptoms. Fidaxomicin is a good therapeutic alternative to vancomycin and metronidazole, especially in patients with recurrence of C difficile infection. Patients rarely experience systemic side effects which improves compliance. The dose of fidaxomicin is expected to be 200 mg given orally twice a day for patients 16 years and older. At this point, Optimer Pharmaceuticals Inc has conducted clinical trials in adults only. Additional clinical trials in pediatric patients are needed before therapeutic recommendations can be made in this population.

Killing kinetics of fidaxomicin and its major metabolite, OP-1118, against Clostridium difficile

The kinetics of bacterial killing for fidaxomicin and its major metabolite, OP-1118, were investigated against Clostridium difficile strains, including two clinical strains belonging to the restriction endonuclease analysis group BI (ORG 1687 and 1698), the ATCC 43255 strain and two laboratory-derived mutant strains with decreased susceptibility to fidaxomicin (ORG 919 and 1620). Both fidaxomicin and OP-1118 demonstrated time-dependent killing of C. difficile strains. Fidaxomicin (at 4× MIC) reduced bacterial counts of the ATCC 43255 strain, clinical strain ORG 1687 and the two laboratory-generated mutant strains by ≥3 logs within 48 h of exposure. The other BI strain, ORG 1698, was tested at 2× MIC fidaxomicin with bacterial counts decreasing 1 log in 48 h. Exposure to OP-1118 (at 4× MIC) also resulted in a ≥3 log drop in c.f.u. counts for the ATCC 43255 strain, the clinical BI strain ORG 1687 and the mutant strain ORG 919. Higher concentrations of OP-1118 (32× MIC) were required for a 3 log reduction in c.f.u. counts for the other BI strain, ORG 1698. In summary, the results indicate that both fidaxomicin and its major metabolite, OP-1118, are bactericidal against C. difficile strains, including the hypervirulent restriction endonuclease analysis group BI strains, at concentrations that are many fold below the detected faecal concentrations of these compounds after oral administration of fidaxomicin.

Fidaxomicin versus vancomycin for Clostridium difficile infection

BACKGROUND

Clostridium difficile infection is a serious diarrheal illness associated with substantial morbidity and mortality. Patients generally have a response to oral vancomycin or metronidazole; however, the rate of recurrence is high. This phase 3 clinical trial compared the efficacy and safety of fidaxomicin with those of vancomycin in treating C. difficile infection.

METHODS

Adults with acute symptoms of C. difficile infection and a positive result on a stool toxin test were eligible for study entry. We randomly assigned patients to receive fidaxomicin (200 mg twice daily) or vancomycin (125 mg four times daily) orally for 10 days. The primary end point was clinical cure (resolution of symptoms and no need for further therapy for C. difficile infection as of the second day after the end of the course of therapy). The secondary end points were recurrence of C. difficile infection (diarrhea and a positive result on a stool toxin test within 4 weeks after treatment) and global cure (i.e., cure with no recurrence).

RESULTS

A total of 629 patients were enrolled, of whom 548 (87.1%) could be evaluated for the per-protocol analysis. The rates of clinical cure with fidaxomicin were noninferior to those with vancomycin in both the modified intention-to-treat analysis (88.2% with fidaxomicin and 85.8% with vancomycin) and the per-protocol analysis (92.1% and 89.8%, respectively). Significantly fewer patients in the fidaxomicin group than in the vancomycin group had a recurrence of the infection, in both the modified intention-to-treat analysis (15.4% vs. 25.3%, P=0.005) and the per-protocol analysis (13.3% vs. 24.0%, P=0.004). The lower rate of recurrence was seen in patients with non–North American Pulsed Field type 1 strains. The adverse-event profile was similar for the two therapies.

CONCLUSIONS

The rates of clinical cure after treatment with fidaxomicin were noninferior to those after treatment with vancomycin. Fidaxomicin was associated with a significantly lower rate of recurrence of C. difficile infection associated with non–North American Pulsed Field type 1 strains. (Funded by Optimer Pharmaceuticals; ClinicalTrials.gov number, NCT00314951.)