Rifamycin antibiotics for treatment of Clostridium difficile-associated diarrhea

Antibiotic Resistances of Clostridioides difficile

The rapid evolution of antibiotic resistance in Clostridioides difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are a matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances, and most of the epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways or biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

Characterization of Food Chain Clostridioides difficile Isolates in Terms of Ribotype and Antimicrobial Resistance

The aim of this study was to characterize C. difficile isolates from the farm, abattoir, and retail outlets in Ireland in terms of ribotype and antibiotic resistance (vancomycin, erythromycin, metronidazole, moxifloxacin, clindamycin, and rifampicin) using PCR and E-test methods, respectively. The most common ribotype in all stages of the food chain (including retail foods) was 078 and a variant (RT078/4). Less commonly reported (014/0, 002/1, 049, and 205) and novel (RT530, 547, and 683) ribotypes were also detected, but at lower frequencies. Approximately 72% (26/36 tested) of the isolates tested were resistant to at least one antibiotic, with the majority of these (65%; 17/26) displaying a multi-drug (three to five antibiotics) resistant phenotype. It was concluded that ribotype 078, a hypervirulent strain commonly associated with C. difficile infection (CDI) in Ireland, was the most frequent ribotype along the food chain, resistance to clinically important antibiotics was common in C. difficile food chain isolates, and there was no relationship between ribotype and antibiotic resistance profile.

Evaluation of disk diffusion method for testing the rifampicin, erythromycin, and tetracycline susceptibility of Clostridioides (prev. Clostridium) difficile

INTRODUCTION

Antimicrobial resistance (AMR) is one of the greatest threats to animal and public health. Clostridioides (prev. Clostridium) difficile is a major burden to healthcare and a relevant AMR gene reservoir. Despite the known importance of AMR in C. difficile epidemiology and treatment, antimicrobial susceptibility testing for this pathogen is still based on the determination of the minimal inhibitory concentration (MIC) by the agar dilution method, which is technically demanding and labor-intensive. In this study, the disk diffusion method was used to evaluate the susceptibility of C. difficile to erythromycin, rifampicin, and tetracycline.

MATERIAL AND METHODS

A total of 155 isolates isolated between 2011 and 2022 from humans and animals in Brazil were simultaneously tested using the disk diffusion method and the epsilometer test (Etest) for these three antimicrobials on Brucella blood agar supplemented with vitamin K and hemin.

RESULTS

The results suggest that disk diffusion can be an interesting routine tool to identify erythromycin- and rifampicin-resistant C. difficile isolates (≥20 mm cut-off) and wild type (WT) strains (≥28 mm). However, the disk diffusion protocol tested in this study does not seem suitable for tetracycline because of the common misclassification of resistant strains.

Rifaximin Therapy for Patients With Metronidazole-Unresponsive Clostridium difficile Infection

Background

Clostridium difficile infection (CDI) is a leading cause of hospital-acquired diarrhea. Rifaximin is an antibiotic that offers marginal resistance to C. difficile bacteria. This study was conducted to evaluate the efficacy of rifaximin in metronidazole non-responsive CDI patients.

Methods

A cross-sectional study was performed from August 2019 to May 2020 at the Lahore General Hospital, Lahore, Pakistan. A total of 200 cases were included. Patients who developed diarrhea after receiving antibiotics for seven days and a positive C. difficile toxin stool test as detected by the enzyme immunoassay (BioCheck, Inc., CA) were diagnosed with CDI. Only patients who were unresponsive to metronidazole therapy were enrolled in our analysis. Two groups were formed. The intervention group was administered 200 mg tablets of rifaximin three times a day for 10 days. For patients in the control group, no new treatment was started. The efficacy of rifaximin was defined in terms of the resolution of diarrhea after two weeks of therapy and a negative stool test. All data were recorded in a predefined pro forma.

Results

The mean age of 45.41 ± 8.54 years was found in the intervention group. The majority of the patients were aged 35-50 years. The majority of the patients had watery diarrhea, abdominal cramping, and loss of appetite on presentation. Rifaximin was found to be significantly effective in the resolution of symptoms of CDI, which was previously unresponsive to metronidazole (p<0.00001). it was found that the duration of diarrhea of more than three weeks was significantly associated with failure of therapy (p=0.03).

Conclusion

We concluded that rifaximin therapy is effective for patients of CDI non-responsive to metronidazole in more than 65% of the cases. Even though several new developments are made to address the concerned subject, such as microbiota transplantation, antibiotics, and immunotherapy, rifaximin can be considered for patients with metronidazole non-responsive CDI.

Molecular epidemiology and clinical risk factors for rifaximin-non-susceptible Clostridioides difficile infection in South Korea: a prospective, multicentre, observational study

OBJECTIVES

This study was designed to investigate the molecular epidemiology of Clostridioides difficile isolates in South Korea and to evaluate risk factors for rifaximin-non-susceptible C. difficile infection (CDI).

METHODS

A total of 413 patients with CDI from two sentinel hospitals in South Korea were enrolled in this study. Putative clinical risk factors for CDI were identified using digital medical records of the patients. Pathogen profiles, including antimicrobial susceptibility, toxin production and ribotype, were evaluated for each of the causative C. difficile isolates.

RESULTS

Of the 413 C. difficile isolates, 81 (19.6%) were shown to be rifaximin-non-susceptible, with the most common ribotypes being 018 (56.8%; 46/81), 017 (16.0%; 13/81) and 027 (6.2%; 5/81). Rifaximin-non-susceptible C. difficile isolates exhibited higher non-susceptibility rates to most of the other drugs tested in this study compared with rifaximin-susceptible isolates. Previous history of pulmonary tuberculosis and prior rifaximin treatment were shown to be associated with the occurrence of rifaximin-non-susceptible CDI compared with susceptible CDI.

CONCLUSION

Non-susceptibility rates to rifaximin for the C. difficile isolates identified in this study were reasonably high with most of the resistant strains belonging to either ribotype 018 or 017. Widespread dissemination of these clones may be the result of antimicrobial selection pressure introduced by the widespread use of rifaximin. These results suggest that a sustainable surveillance programme for CDI and C. difficile resistance is needed in order to better control CDIs and to improve therapeutic efficacy.

Long-term clinical safety of clindamycin and rifampicin combination for the treatment of hidradenitis suppurativa. A Critically Appraised Topic

CLINICAL QUESTION/SCENARIO

Can therapy with clindamycin and rifampicin be safely continued long term beyond the recommended 10-week course?

BACKGROUND

Clindamycin and rifampicin are used in combination to treat hidradenitis suppurativa (HS). There is no data on the efficacy and safety of clindamycin/rifampicin combination therapy for HS beyond 10 weeks.

METHODS

We identified the following major concerns that still lack a proper evidenced-based analysis: for rifampicin, drug-induced liver injury, interstitial nephritis, drug interaction and hepatic p450 3A4 enzyme induction; for clindamycin, the concern was community-acquired Clostridium difficile infection (CA-CDI); and experience with long-term treatment. Data sources were used as appropriate to answer the question. Systematic searches were used to assess the risk of CA-CDI and experience with long-term treatment with clindamycin.

RESULTS/IDENTIFIED EVIDENCE

The risk for rifampicin-induced liver injury is highest in the first 6 weeks of treatment, whereas interstitial nephritis is primarily observed during intermittent treatment. Enzyme induction due to rifampicin is usually complete after about 2 weeks of treatment and reduces clindamycin blood levels by about 90%. Three meta-analyses identified antibiotic use as a risk factor for CA-CDI. Two of them assigned the highest risk to clindamycin. None of them stratified by length of treatment. There is extensive experience with rifampicin, primarily for the treatment of tuberculosis. Long-term experience with clindamycin is limited.

DISCUSSION AND RECOMMENDATION FOR CLINICAL CARE

The analysed risks associated with a combination of clindamycin and rifampicin for hidradenitis suppurative cluster within the first 10 weeks. Treatment can be continued beyond 10 weeks, if clinically necessary.

Clostridium difficile infection in oncology patients: epidemiology, pathophysiology, risk factors, diagnosis, and treatment

Clostridium difficile infection (CDI) is one of the most common healthcare-associated infections in the United States. Its incidence has been increasing in the recent years despite preventative measures. CDI increases annual expenses by 1.5 billion dollars. Cancer patients are at higher risk to acquire CDI, as explained by their frequent exposure to risk factors. CDI in cancer patients is associated with higher mortality rates and prolonged hospitalization. Furthermore, CDI affects the course of the disease by delaying treatments such as chemotherapy. Chemotherapeutics drugs are considered independent risk factors for CDI. This review discusses Clostridium difficile infection in cancer patients, including those who are receiving chemotherapy. Herein, we summarize recent data regarding the epidemiology, risk factors, including chemotherapy regimens, pathogenesis, diagnostic techniques and treatment options, including newer agents. Method: A literature search was performed using the PubMed and Google Scholar databases. The MeSH terms utilized in different combinations were 'clostridium difficile', 'neoplasia/cancer/oncology', 'chemotherapy', 'diagnosis', and 'treatment', in addition to looking up each treatment option individually to generate a comprehensive search. The articles were initially screened by title alone, followed by screening through abstracts. Full texts of pertinent articles (including letters to editors, case reports, case series, cohort studies, and clinical trials) were included in this review.

Novel Antimicrobials for the Treatment of Clostridium difficile Infection

The current picture of Clostridium difficile infection (CDI) is alarming with a mortality rate ranging between 3% and 15% and a CDI recurrence rate ranging from 12% to 40%. Despite the great efforts made over the past 10 years to face the CDI burden, there are still gray areas in our knowledge on CDI management. The traditional anti-CDI antimicrobials are not always adequate in addressing the current needs in CDI management. The aim of our review is to give an update on novel antimicrobials for the treatment of CDI, considering the currently available evidences on their efficacy, safety, molecular mechanism of action, and their probability to be successfully introduced into the clinical practice in the near future. We identified, through a PubMed search, 16 novel antimicrobial molecules under study for CDI treatment: cadazolid, surotomycin, ridinilazole, LFF571, ramoplanin, CRS3123, fusidic acid, nitazoxanide, rifampin, rifaximin, tigecycline, auranofin, NVB302, thuricin CD, lacticin 3147, and acyldepsipeptide antimicrobials. In comparison with the traditional anti-CDI antimicrobial treatment, some of the novel antimicrobials reviewed in this study offer several advantages, i.e., the favorable pharmacokinetic and pharmacodynamic profile, the narrow-spectrum activity against CD that implicates a low impact on the gut microbiota composition, the inhibitory activity on CD sporulation and toxins production. Among these novel antimicrobials, the most active compounds in reducing spore production are cadazolid, ridinilazole, CRS3123, ramoplanin and, potentially, the acyldepsipeptide antimicrobials. These antimicrobials may potentially reduce CD environment spread and persistence, thus reducing CDI healthcare-associated acquisition. However, some of them, i.e., surotomycin, fusidic acid, etc., will not be available due to lack of superiority versus standard of treatment. The most CD narrow-spectrum novel antimicrobials that allow to preserve microbiota integrity are cadazolid, ridinilazole, auranofin, and thuricin CD. In conclusion, the novel antimicrobial molecules under development for CDI have promising key features and advancements in comparison to the traditional anti-CDI antimicrobials. In the near future, some of these new molecules might be effective alternatives to fight CDI.

Clostridium difficile Infections: A Global Overview of Drug Sensitivity and Resistance Mechanisms

Clostridium difficile (C. difficile) is the most prevalent causative pathogen of healthcare-associated diarrhea. Notably, over the past 10 years, the number of Clostridium difficile outbreaks has increased with the rate of morbidity and mortality. The occurrence and spread of C. difficile strains that are resistant to multiple antimicrobial drugs complicate prevention as well as potential treatment options. Most C. difficile isolates are still susceptible to metronidazole and vancomycin. Incidences of C. difficile resistance to other antimicrobial drugs have also been reported. Most of the antibiotics correlated with C. difficile infection (CDI), such as ampicillin, amoxicillin, cephalosporins, clindamycin, and fluoroquinolones, continue to be associated with the highest risk for CDI. Still, the detailed mechanism of resistance to metronidazole or vancomycin is not clear. Alternation in the target sites of the antibiotics is the main mechanism of erythromycin, fluoroquinolone, and rifamycin resistance in C. difficile. In this review, different antimicrobial agents are discussed and C. difficile resistance patterns and their mechanism of survival are summarized.

Surveillance of antibiotic resistance among common Clostridium difficile ribotypes in Hong Kong

Incidence of Clostridium difficile infection (CDI) is rapidly increasing and it poses a major health burden globally. However, data regarding the epidemiology of CDI in Asia are limited. We aimed to characterize the antimicrobial susceptibility patterns of common ribotypes of toxigenic C. difficile in Hong Kong. Fifty-three PCR ribotypes were identified among 284 toxigenic C. difficile clinical isolates. The five most prevalent ribotypes were 002 (13%), 017 (12%), 014 (10%), 012 (9.2%), and 020 (9.5%). All tested C. difficile strains remained susceptible to metronidazole, vancomycin, meropenem and piperacillin/tazobactam, but highly resistant to cephalosporins. Of the fluoroquinolones, highest resistance to ciprofloxacin was observed (99%), followed by levofloxacin (43%) and moxifloxacin (23%). The two newly emerged PCR ribotypes, 017 and 002, demonstrated high levels of co-resistance towards clindamycin, tetracycline, erythromycin and moxifloxacin. PCR ribotypes 017 and 002 with multi-drug resistance are rapidly emerging and continuous surveillance is important to monitor the epidemiology of C. difficile to prevent outbreaks of CDI.

Metronidazole or Rifaximin for Treatment of Clostridium difficile in Pediatric Patients with Inflammatory Bowel Disease: A Randomized Clinical Trial

BACKGROUND

Interestingly, Clostridium difficile infection (CDI) worsens the course of inflammatory bowel disease (IBD); however, there is a paucity of data regarding the treatment of CDI in this group of patients.

METHODS

This was a prospective, single-blind trial. Children with flare of IBD and CDI were randomly assigned to receive metronidazole or rifaximin orally for 14 days. CDI was diagnosed based on a positive well-type enzyme immunoassay (EIA) toxins A/B stool test for C. difficile toxins A and/or B. The cure rate was defined as the percentage of patients with a negative EIA stool test for C. difficile toxins A/B measured 4 weeks after the end of treatment. Recurrence was defined as a repeat CDI within 2 to 8 weeks.

RESULTS

In total, we included 31 patients with IBD including 12 patients with Crohn's disease and 19 with ulcerative colitis. Of them, 17 received metronidazole and 14 received rifaximin. There were no statistically significant differences between the 2 study groups including age, type of treatment, and disease activity. There was no statistically significant difference in the cure rate between patients treated with metronidazole and rifaximin (70.6% versus 78.6%, respectively, P = 0.5). We found no difference in recurrence rate between the 2 study treatment types (17% versus 0%, respectively, P = 0.3). We did not find an association between immunosuppressive therapy and CDI cure rate or CDI recurrence rate.

CONCLUSIONS

Metronidazole and rifaximin were similarly effective treatments for CDI in pediatric patients with IBD.

Rifaximin and diverticular disease: Position paper of the Italian Society of Gastroenterology (SIGE)

Management of diverticular disease has significantly improved in the last decade. Antibiotic treatment is used for symptom relief and prevention of complications. In Italy, the non-absorbable antibiotic rifaximin is one of the most frequently used drugs, and it is perceived as the reference drug to treat symptomatic diverticular disease. Its non-systemic absorption and high faecal concentrations have oriented rifaximin use to the gastrointestinal tract, where rifaximin exerts eubiotic effects representing an additional value to its antibiotic activity. This position paper was commissioned by the Italian Society of Gastroenterology governing board for a panel of experts (RC, GB, BA) to highlight the indications for treatment of diverticular disease. There is a lack of rationale for drug use for the primary prevention of diverticulitis in patients with diverticulosis; thus, rifaximin use should be avoided. The cyclic use of rifaximin, in association with high-fibre intake, is safe and useful for the treatment of symptomatic uncomplicated diverticular disease, even if the cost-efficacy of long-term treatment remains to be determined. The use of rifaximin in the prevention of diverticulitis recurrence is promising, but the low therapeutic advantage needs to be verified. No evidence is available on the efficacy of rifaximin treatment on acute uncomplicated diverticulitis.

Australasian Society of Infectious Diseases updated guidelines for the management of Clostridium difficile infection in adults and children in Australia and New Zealand

The incidence of Clostridium difficile infection (CDI) continues to rise, whilst treatment remains problematic due to recurrent, refractory and potentially severe nature of disease. The treatment of C. difficile is a challenge for community and hospital-based clinicians. With the advent of an expanding therapeutic arsenal against C. difficile since the last published Australasian guidelines, an update on CDI treatment recommendations for Australasian clinicians was required. On behalf of the Australasian Society of Infectious Diseases, we present the updated guidelines for the management of CDI in adults and children.

Disruption of the Gut Microbiome: Clostridium difficile Infection and the Threat of Antibiotic Resistance

Clostridium difficile is well recognized as the leading cause of antibiotic-associated diarrhea, having a significant impact in both health-care and community settings. Central to predisposition to C. difficile infection is disruption of the gut microbiome by antibiotics. Being a Gram-positive anaerobe, C. difficile is intrinsically resistant to a number of antibiotics. Mobile elements encoding antibiotic resistance determinants have also been characterized in this pathogen. While resistance to antibiotics currently used to treat C. difficile infection has not yet been detected, it may be only a matter of time before this occurs, as has been seen with other bacterial pathogens. This review will discuss C. difficile disease pathogenesis, the impact of antibiotic use on inducing disease susceptibility, and the role of antibiotic resistance and mobile elements in C. difficile epidemiology.

Antimicrobial Resistance and Reduced Susceptibility in Clostridium difficile: Potential Consequences for Induction, Treatment, and Recurrence of C. difficile Infection

Clostridium difficile infection (CDI) remains a substantial burden on healthcare systems and is likely to remain so given our reliance on antimicrobial therapies to treat bacterial infections, especially in an aging population in whom multiple co-morbidities are common. Antimicrobial agents are a key component in the aetiology of CDI, both in the establishment of the infection and also in its treatment. The purpose of this review is to summarise the role of antimicrobial agents in primary and recurrent CDI; assessing why certain antimicrobial classes may predispose to the induction of CDI according to a balance between antimicrobial activity against the gut microflora and C. difficile. Considering these aspects of CDI is important in both the prevention of the infection and in the development of new antimicrobial treatments.

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.

Progress in the discovery of treatments for C. difficile infection: A clinical and medicinal chemistry review

Clostridium difficile is an anaerobic, Gram-positive pathogen that causes C. difficile infection, which results in significant morbidity and mortality. The incidence of C. difficile infection in developed countries has become increasingly high due to the emergence of newer epidemic strains, a growing elderly population, extensive use of broad spectrum antibiotics, and limited therapies for this diarrheal disease. Because treatment options currently available for C. difficile infection have some drawbacks, including cost, promotion of resistance, and selectivity problems, new agents are urgently needed to address these challenges. This review article focuses on two parts: the first part summarizes current clinical treatment strategies and agents under clinical development for C. difficile infection; the second part reviews newly reported anti-difficile agents that have been evaluated or reevaluated in the last five years and are in the early stages of drug discovery and development. Antibiotics are divided into natural product inspired and synthetic small molecule compounds that may have the potential to be more efficacious than currently approved treatments. This includes potency, selectivity, reduced cytotoxicity, and novel modes of action to prevent resistance.

Emergence of Clostridium difficile infection in tuberculosis patients due to a highly rifampicin-resistant PCR ribotype 046 clone in Poland

Clostridium difficile infection (CDI) is a major cause of nosocomial diarrhea. CDI is known to develop after antibiotic administration, but anti-tuberculosis agents have rarely been implicated. We documented an outbreak caused by a highly rifampicin-resistant C. difficile strain of polymerase chain reaction (PCR) ribotype 046 in patients with active tuberculosis.

Lack of Clostridium difficile infection in patients treated with rifaximin for hepatic encephalopathy: a retrospective analysis

GOALS

The purpose of this study was to assess the incidence of Clostridium difficile infection in patients who received rifaximin for the treatment of hepatic encephalopathy (HE).

METHODS

Medical charts of patients who received rifaximin for the treatment of HE were reviewed. The number of patients who developed diarrhea during treatment with rifaximin and results of latex agglutination assays to detect C. difficile in stool samples were analyzed.

RESULTS

A total of 211 patients received rifaximin for HE. Of these, 152 were treated in a university practice and 59 were treated in community practices. The mean dose of rifaximin was 1055 mg/d (range, 600 to 1600 mg/d) for a mean duration of 250 days (range, 180 to 385 d). Eighteen patients developed diarrhea during rifaximin treatment. None of these patients tested positive for C. difficile.

CONCLUSIONS

This study demonstrates that treatment of HE with the safe, nonsystemic, gut-selective antibiotic rifaximin was not associated with the development of C. difficile infection.

Rifaximin in the treatment of recurrent Clostridium difficile infection

BACKGROUND

Clostridium difficile can cause severe antibiotic-associated colitis. Conventional treatments with metronidazole and vancomycin improve symptoms, but after discontinuation of treatment, C. difficile infection (CDI) recurs in a number of patients. Rifaximin is a rifamycin-based non-systemic antibiotic that has effect against C. difficile.

AIM

To assess the effectiveness of rifaximin in recurrent C. difficile infection.

METHODS

We retrospectively evaluated the records of 32 patients who were treated with rifaximin for recurrent C. difficile infection. The symptoms were evaluated 12 weeks after the start of treatment and patient records were followed up until 1 year after treatment.

RESULTS

The mean age of the patients was 55 years (median 64, range: 19-84 years). Before the initiation of rifaximin therapy, the patients had undergone, on the average, 4.4 (range: 2-12) antimicrobial courses for C. difficile infection. C. difficile strain typing was performed in 27 patients. Eight (30%) patients had a strain with a DNA profile compatible with the BI/NAP1/027 ribotype. Antibiotic susceptibilities were determined of isolates from 22 patients. Most isolates (68%) had very low MIC-values for rifampin (<0.002 μg/mL) and the highest MIC value was 3.0 μg/mL. Isolates with a DNA profile compatible with the BI/NAP1/027 ribotype had, on the average, higher MICs of rifampin. After 12 weeks 17 (53%) patients had no relapse. The MIC value of rifampin seemed to predict the response to rifaximin treatment.

CONCLUSIONS

Rifaximin is a safe treatment for C. difficile infection. It has a reasonable effect in C. difficile infection and it can be considered as an optional treatment for recurrent C. difficile infection.

What would we do without metronidazole?

Metronidazole is a treatment of choice for several types of infections, but coexisting conditions or concomitant medications may preclude its use. Although tinidazole, a newer nitroimidazole, may be an option in cases where drug interactions make the use of metronidazole inadvisable, similar absolute contraindications exist. In situations where nitroimidazole use is contraindicated or inadvisable, clinicians may have difficulty deciding on efficacious treatment options. For the treatment of trichomoniasis, alternatives include furazolidone, clotrimazole, nonoxynol-9 or paromomycin. Alternatives for bacterial vaginosis include clindamycin topically or systemically. For giardiasis, alternative options include paromomycin, nitazoxanide or the antihelminthic benzimidazoles. Alternatives for Clostridium difficile are varied, including oral vancomycin, nitazoxanide and rifaximin. Although options are limited, alternative therapies for treatment of patients with absolute contraindications to the nitroimidazole antibiotics are available.

Rifaximin in Combination with Metronidazole and Oral Vancomycin for the Treatment of an Initial Episode of Clostridium difficile–Associated Diarrhea: Case Report and Literature Review

Purpose

Example of successful use of rifaximin in the treatment of an apparent Clostridium difficile infection refractory to vancomycin and metronidazole with literature review.

Case Summary

A 69-year-old Caucasian female developed C. difficile infectious diarrhea, confirmed by enzyme immunoassay (EIA) test. Following diagnosis, the patient was initiated on a treatment regimen of intravenous (IV) metronidazole and oral vancomycin. The patient sought additional medical treatment 3 days after initiating this treatment regimen. She presented with continued symptoms of diarrhea, bloating, anorexia, weakness, and leukocytosis nonresponsive to metronidazole and vancomycin. After a total of 7 days of treatment with metronidazole and vancomycin, the patient remained symptomatic with loose stools occurring approximately every 2 hours. Oral rifaximin 400 mg 3 times a day was added to the regimen, after which the patient's symptoms improved rapidly.

Conclusion

A patient with presumed C. difficile–associated diarrhea refractory to metronidazole and vancomycin was successfully treated after the addition of oral rifaximin 400 mg 3 times a day. Based on current literature and this case, rifaximin should not replace metronidazole or vancomycin as primary therapy for presumed or diagnosed C. difficile but should be retained as a useful alternative, especially in light of limited alternatives.

Treatment of Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) is a serious subtype of antibiotic-associated diarrhea. In recent years, the incidence and severity of CDAD have significantly increased worldwide. Clostridium difficile is a Gram-positive enteric pathogen and can produce toxin A and toxin B, which induce cytopathic changes and lead to a series of clinical manifestations of infection. Although the use of broad spectrum antibiotics is the most common cause for the development of CDAD, age, chronic disease, long-term hospitalization and other factors are also possible risk factors. Patients with confirmed or highly suspected CDAD should immediately discontinue antibiotics and switch to other drugs which do not tend to cause CDAD. Treatment with metronidazole or vancomycin is recommended. Recent studies show that teicoplanin, probiotics, monoclonal antibody and Chinese medicine are also effective for this disease. In this paper, we discuss the prevention and treatment of CDAD.

Divergent rifamycin susceptibilities of Clostridium difficile strains in Canada and Italy and predictive accuracy of rifampin Etest for rifamycin resistance

We tested the activities of rifampin (RIF) and rifaximin (RFX) against 180 Clostridium difficile clinical isolates selected from Canadian and Italian culture collections. MICs were determined by CLSI agar dilution for both drugs and by Etest for RIF. Sixteen of 85 Italian isolates (18.8%) showed high-level resistance to both rifamycins (MICs, >16 μg/ml), compared to 2 of 95 (2.1%) Canadian isolates. Two new rpoB mutations were identified in rifamycin-resistant isolates. RIF susceptibility by Etest correlated completely with susceptibility to both rifamycins determined by agar dilution.

Biologic properties and clinical uses of rifaximin

INTRODUCTION

Rifaximin is increasingly being used to treat acute and chronic gastrointestinal infections and disorders. The drug exerts its beneficial effect through a variety of gut-selective mechanisms involving the host intestinal microbiota.

AREAS COVERED

Abstracts of all publications listed in PubMed on the topic of rifaximin are reviewed to determine their potential value in the understanding of mechanisms of rifaximin activity. The author's extensive file on the drug is also used in the review.

EXPERT OPINION

Rifaximin inhibits a broad spectrum of bacteria in the bile-rich small bowel and susceptible bacteria in the aqueous colon, and alters microbial virulence and epithelial cell function. The different mechanisms of action of rifaximin potentially explain the use of the drug in widely varied diseases and syndromes.

Multidrug resistance in European Clostridium difficile clinical isolates

OBJECTIVES

Multidrug resistance and antibiotic resistance mechanisms were investigated in 316 Clostridium difficile clinical isolates collected during the first European surveillance on C. difficile in 2005.

METHODS

MICs of eight different antibiotics were determined using Etest. Reserpine- and carbonyl cyanide m-chlorophenylhydrazone-sensitive efflux was tested using the agar dilution method. Molecular analysis of the resistance mechanisms was performed using PCR assays, PCR mapping and sequencing.

RESULTS

One hundred and forty-eight C. difficile strains were resistant to at least one antibiotic and 82 (55%) were multidrug resistant. In particular, 48% of these isolates were resistant to erythromycin, clindamycin, moxifloxacin and rifampicin. New genetic elements or determinants conferring resistance to erythromycin/clindamycin or tetracycline were identified. Even if most multiresistant strains carried an erm(B) gene, quite a few were erm(B) negative. In-depth analysis of the underlying mechanism in these isolates was carried out, including analysis of 23S rDNA and the ribosomal proteins L4 and L22. Interestingly, resistance to rifampicin was observed in multidrug-resistant strains in association with resistance to fluoroquinolones. Mutations in the rpo(B) and gyrA genes were identified as the cause of resistance to these antibiotics, respectively.

CONCLUSIONS

Characterization of multidrug-resistant C. difficile clinical isolates shows that antibiotic resistance is changing, involving new determinants and mechanisms and providing this pathogen with potential advantages over the co-resident gut flora. The present paper provides, for the first time, a comprehensive picture of the different characteristics of multidrug-resistant C. difficile strains in Europe in 2005 and represents an important source of data for future comparative European studies.

Treatment of refractory and recurrent Clostridium difficile infection

The incidence of Clostridium difficile infection (CDI) has increased since 2000, with greater numbers of severe cases reported, in part due to the emergence of a hypervirulent strain. Initial therapy with metronidazole is still recommended for mild to moderate CDI, but vancomycin is recommended for first-line therapy of severe CDI. Colectomy could be life-saving for some patients with severe disease that does not respond to maximal medical therapy. Recurrent CDI is a challenge to treat; no single effective therapy currently exists. Treatments include antibiotics, adjunct probiotics, fecal microbiota transplant and immune approaches. This Review discusses the various therapeutic approaches used for the treatment of refractory and recurrent CDI.

In vitro activity and single-step mutational analysis of rifamycin SV tested against enteropathogens associated with traveler's diarrhea and Clostridium difficile

Rifamycin SV is a broad-spectrum, poorly absorbed antimicrobial agent that, when coupled with MMX technology, is being targeted for the oral treatment of traveler's diarrhea (TD) and Clostridium difficile-associated disease (CDAD). Rifamycin SV was tested for activity against 911 TD-associated enteropathogens and 30 C. difficile isolates collected from several global surveillance studies. Rifamycin SV demonstrated similar antimicrobial activity levels against the Enterobacteriaceae, with MIC₅₀ values ranging from 32 to 128 μg/ml for all but one strain (an enterotoxigenic Escherichia coli at >512 μg/ml). For non-Enterobacteriaceae strains, MIC₅₀ values ranged from 2 to 8 μg/ml, with the exception of Campylobacter spp., for which all strains had MIC values of >512 μg/ml. Rifamycin SV also demonstrated excellent activity (MIC₅₀ of ≤ 0.03 μg/ml) against most C. difficile strains (including one hypervirulent NAP1 strain), and this activity was even superior to the potency observed for vancomycin, metronidazole, and rifaximin. In mutational passaging studies, rifamycin SV induced stable resistance and showed a mutation frequency in E. coli similar to that of rifampin. This study presents the potency of rifamycin SV for enteropathogens commonly recovered from patients with TD and CDAD. Additional in vitro and in vivo studies appear necessary to determine the utility of rifamycin SV as an oral agent for the prevention and treatment of TD and CDAD.

The ecology and pathobiology of Clostridium difficile infections: an interdisciplinary challenge

Clostridium difficile is a well recognized pathogen of humans and animals. Although C. difficile was first identified over 70 years ago, much remains unknown in regards to the primary source of human acquisition and its pathobiology. These deficits in our knowledge have been intensified by dramatic increases in both the frequency and severity of disease in humans over the last decade. The changes in C. difficile epidemiology might be due to the emergence of a hypervirulent stain of C. difficile, ageing of the population, altered risk of developing infection with newer medications, and/or increased exposure to C. difficile outside of hospitals. In recent years, there have been numerous reports documenting C. difficile contamination of various foods, and reports of similarities between strains that infect animals and strains that infect humans as well. The purposes of this review are to highlight the many challenges to diagnosing, treating, and preventing C. difficile infection in humans, and to stress that collaboration between human and veterinary researchers is needed to control this pathogen.

Rifaximin therapy for metronidazole-unresponsive Clostridium difficile infection: a prospective pilot trial

BACKGROUND

Clostridium difficile infection (CDI) is a recent epidemic in the United States, particularly in the hospital setting. Oral metronidazole is standard therapy for C. difficile infection, but resistance to metronidazole is becoming a clinical challenge.

METHODS

We evaluated the efficacy of the nonsystemic oral antibiotic rifaximin for the treatment of metronidazole-resistant C. difficile infection. Twenty-five patients with C. difficile infection were enrolled in the study. All had mild-to-moderate C. difficile infection (5-10 bowel movements a day without sepsis) unresponsive to metronidazole (i.e. stools positive for toxins A and B after oral metronidazole 500 mg three times daily [t.i.d.] for 5 days). After discontinuation of metronidazole, rifaximin 400 mg t.i.d. for 14 days was prescribed. Patients were followed for 56 days and stool was tested for C. difficile using polymerase chain reaction (PCR) to assess the effect of treatment. A negative PCR test result was interpreted as a favorable response to rifaximin.

RESULTS

Sixteen of 22 patients (73%) were eligible for study inclusion and completed rifaximin therapy experienced eradication of infection (stool negative for C. difficile) immediately after rifaximin therapy and 56 days post-treatment. Three patients (12%) discontinued therapy because of abdominal distention. Rifaximin was generally well tolerated.

CONCLUSIONS

In conclusion, rifaximin may be considered for treatment of mild-to-moderate C. difficile infection that is resistant to metronidazole. Larger randomized trials are needed to confirm these positive findings.

New antimicrobial agents for patients with Clostridium difficile infections

Current drug treatment of Clostridium difficile infection (CDI) focuses on metronidazole and vancomycin. Early studies showed equivalence, but more recent reports indicate that oral vancomycin is preferred for serious CDI. Recent work has demonstrated a need for new drugs due to challenges with the NAP-1 strain, which appears to cause more refractory disease that is more likely to relapse. These two distinctive facets of treatment are the most challenging. This review discusses new agents in development: antibiotics, probiotics, immune response products, and agents to bind C. difficile toxins. None are likely to be more effective than oral vancomycin for acute infection. However, several may be as effective, without causing relapse or promoting unnecessary antibiotic use for multiple conditions. The greatest promise is with agents used to interrupt relapses. In this category the leading new agents appear to be antibiotics (rifaximin, nitazoxanide, difimicin, ramoplanin), toxin-binding agents (tolevamer), probiotics (Saccharomyces -boulardii and Lactobacillus ramosus), and immune agents (toxoid vaccine and hyperimmune globulin). The drugs that appear most promising based on recent trials are rifaximin, tolevamer, and difimicin, which appear promising for reducing relapses.

Toxin-specific antibodies for the treatment of Clostridium difficile: current status and future perspectives

Therapeutic agents targeting bacterial virulence factors are gaining interest as non-antibiotic alternatives for the treatment of infectious diseases. Clostridium difficile is a Gram-positive pathogen that produces two primary virulence factors, enterotoxins A and B (TcdA and TcdB), which are responsible for Clostridium difficile-associated disease (CDAD) and are targets for CDAD therapy. Antibodies specific for TcdA and TcdB have been shown to effectively treat CDAD and prevent disease relapse in animal models and in humans. This review summarizes the various toxin-specific antibody formats and strategies under development, and discusses future directions for CDAD immunotherapy, including the use of engineered antibody fragments with robust biophysical properties for systemic and oral delivery.

Current use for old antibacterial agents: polymyxins, rifamycins, and aminoglycosides

This article reviews three classes of antibacterial agents that are uncommonly used in bacterial infections and therefore can be thought of as special-use agents. The polymyxins are reserved for gram-negative bacilli that are resistant to virtually all other classes of drugs. Rifampin is used therapeutically, occasionally as a companion drug in treatment of refractory gram-positive coccal infections, especially those involving foreign bodies. Rifaximin is a new rifamycin that is a strict enteric antibiotic approved for treatment of traveler's diarrhea and is showing promise as a possible agent for refractory Clostridium difficile infections. The aminoglycosides are used mainly as companion drugs for the treatment of resistant gram-negative bacillary infections and for gram-positive coccal endocarditis.

The use of new and better antibiotics for bacterial infections in patients with leukemia

Bacterial infection is the most common complication of chemotherapy-induced neutropenia particularly in patients with hematologic malignancies. Bacterial infections predominate during the initial phases of neutropenic episodes. The spectrum of bacterial infection continues to evolve globally and locally at the institutional level, as do patterns of antimicrobial susceptibility/resistance. These trends are often associated with local treatment practices (eg, use of antimicrobial prophylaxis, open versus restricted formularies, clinical pathways and/or guidelines) and have a significant effect on the nature of empiric antimicrobial therapy. Increasing rates of resistance among gram-positive and gram-negative bacteria are posing new therapeutic challenges. These challenges can to some extent be overcome by new drug development. Many novel agents for the treatment of resistant gram-positive infections have been developed and are being evaluated in clinical trials. Newer agents for the treatment of Clostridium difficile associated diarrhea are also in the pipeline. Far fewer options to treat multi-drug resistant gram-negative infections exist, and new drug development is lagging behind. Consequently, the judicious use of currently available agents is essential. This is best achieved by the development of multidisciplinary antibiotic stewardship teams that gather baseline data, make recommendations for appropriate antimicrobial usage, and provide monitoring and feedback services to clinical care providers. Along with strict adherence to infection control policies, antimicrobial stewardship provides the best strategies for the management of infectious complications in patients with hematologic malignancies and other high-risk settings.

Rifaximin: a unique gastrointestinal-selective antibiotic for enteric diseases

PURPOSE OF REVIEW

Rifaximin is gaining attention for its potential activity in a multitude of gastrointestinal diseases. We review the unique pharmaceutical properties of this antibiotic and the published evidence in the literature regarding the use of rifaximin for different gastrointestinal disorders.

RECENT FINDINGS

Rifaximin is a gastrointestinal-selective antibiotic with a broad spectrum of antimicrobial activity, an excellent safety profile, minimal drug interactions, and negligible impact on the intestinal microbiome. Rifaximin is currently approved in the United States for the treatment of travelers' diarrhea caused by noninvasive diarrheagenic Escherichia coli and is approved in more than 30 other countries for a variety of gastrointestinal disorders. Considerable research with this medication has been conducted for the treatment and prevention of travelers' diarrhea, the treatment of portal systemic encephalopathy, Clostridium difficile infection, small bowel intestinal overgrowth, irritable bowel syndrome, inflammatory bowel disease, pouchitis, and colonic diverticular disease.

SUMMARY

Rifaximin is effective for the treatment of travelers' diarrhea and can be considered as the treatment of choice for uncomplicated travelers' diarrhea. When invasive travelers' diarrhea pathogens are suspected, an alternative antibiotic should be administered. Rifaximin appears promising as a chemoprophylaxis for travelers' diarrhea and as a treatment of portal systemic encephalopathy. This antibiotic may be effective for other gastrointestinal diseases, but more well designed clinical studies are needed to confirm its efficacy for these off-label indications. Future studies will determine whether the development of significant bacterial resistance will limit rifaximin use.

Antimicrobial resistance in Clostridium difficile

Clostridium difficile is the leading cause of hospital-acquired diarrhoea and the number of outbreaks has risen markedly since 2003. The emergence and spread of resistance in C. difficile is complicating treatment and prevention. Most isolates are still susceptible to vancomycin and metronidazole (MTZ), however transient and heteroresistance to MTZ have been reported. The prevalence of resistance to other antimicrobial agents is highly variable in different populations and in different countries, ranging from 0% to 100%. Isolates of common polymerase chain reaction (PCR) ribotypes are more resistant than uncommon ribotypes. Most of the resistance mechanisms that have been identified in C. difficile are similar to those in other Gram-positive bacteria, including mutation, selection and acquisition of the genetic information that encodes resistance. Better antibiotic stewardship and infection control are needed to prevent further spread of resistance in C. difficile.

Clostridium difficile infection in the intensive care unit

Clostridium difficile infection (CDI) is becoming more common worldwide. The morbidity and mortality associated with C difficile is also increasing at an alarming rate. Critically ill patients are at particularly high risk for CDI because of the prevalence of multiple risk factors in this patient population. Treatment of C difficile continues to be a difficult problem in patients with severe or recurrent disease. This article seeks to provide a broad understanding of CDI in the intensive care unit, with special emphasis on risk factor identification, treatment options, and disease prevention.

Treatment of Clostridium difficile-associated disease

Clostridium difficile infection is an increasing burden to the health care system, totaling more than $1 billion/year in the United States. Treatment of patients with C difficile infection with metronidazole or vancomycin reduces morbidity and mortality, although the number of patients that do not respond to metronidazole is increasing. Despite initial response rates of greater than 90%, 15%-30% of patients have a relapse in symptoms after successful initial therapy, usually in the first few weeks after treatment is discontinued. Failure to develop specific antibody response has recently been identified as a critical factor in recurrence. The review discusses the different management strategies for initial and recurrent symptomatic C difficile infections.

Renewed interest in a difficult disease: Clostridium difficile infections--epidemiology and current treatment strategies

PURPOSE OF REVIEW

Renewed interest in Clostridium difficile infections (CDI) is stimulating research into the pathogenesis and virulence factors for this pathogen. This review summarizes recent progress in the field, particularly in relation to the changing epidemiologic trends and new investigational treatments.

RECENT FINDINGS

Elucidation of the role of different toxins of C. difficile (tcdA, tcdB and binary toxin) is deepening our understanding of CDI. Stain typing of C. difficile isolates is documenting the spread of an emergent strain (BI/NAP1/027) associated with large outbreaks of severe disease. Typing of isolates around the world shows global spread of this strain. Reliance upon metronidazole is questioned due to a lower response rate and newer investigational therapies are reported.

SUMMARY

After being considered a manageable pathogen for decades, C. difficile recently caused large outbreaks of severe disease. Refocused research is determining patients who are at risk for CDI, what methods are more effective in diagnosing CDI and what new treatments may be effective. This article reviews the recent findings in the literature regarding this difficult and challenging pathogen.