Tolevamer, a novel nonantibiotic polymer, compared with vancomycin in the treatment of mild to moderately severe Clostridium difficile-associated diarrhea

Selective toxin sequestrants for the treatment of bacterial infections

Bacterial toxin-mediated diarrheal disease is a major cause of morbidity and mortality worldwide. In this work we designed an on-bead library of protease-resistant, acid-stable peptoid molecules and screened for high affinity binding of cholera toxin. From 100 000 compounds, we discovered a single sequence of residues that can bind and retain cholera toxin at high affinity when immobilized on a solid-phase particle. Furthermore, we demonstrate that these peptoid-displaying particles can sequester active cholera toxin from cell culture media sufficient to protect intestinal cells. We foresee this work as contributory to a potential adjunct therapeutic strategy against cholera infections and other toxin-mediated diseases.

Prospective derivation and validation of a clinical prediction rule for recurrent Clostridium difficile infection

BACKGROUND & AIMS

Prevention of recurrent Clostridium difficile infection (CDI) is a substantial therapeutic challenge. A previous prospective study of 63 patients with CDI identified risk factors associated with recurrence. This study aimed to develop a prediction rule for recurrent CDI using the above derivation cohort and prospectively evaluate the performance of this rule in an independent validation cohort.

METHODS

The clinical prediction rule was developed by multivariate logistic regression analysis and included the following variables: age>65 years, severe or fulminant illness (by the Horn index), and additional antibiotic use after CDI therapy. A second rule combined data on serum concentrations of immunoglobulin G (IgG) against toxin A with the clinical predictors. Both rules were then evaluated prospectively in an independent cohort of 89 patients with CDI.

RESULTS

The clinical prediction rule discriminated between patients with and without recurrent CDI, with an area under the curve of the receiver-operating-characteristic curve of 0.83 (95% confidence interval [CI]: 0.70-0.95) in the derivation cohort and 0.80 (95% CI: 0.67-0.92) in the validation cohort. The rule correctly classified 77.3% (95% CI: 62.2%-88.5%) and 71.9% (95% CI: 59.2%-82.4%) of patients in the derivation and validation cohorts, respectively. The combined rule performed well in the derivation cohort but not in the validation cohort (area under the curve of the receiver-operating-characteristic curve, 0.89 vs 0.62; diagnostic accuracy, 93.8% vs 69.2%, respectively).

CONCLUSIONS

We prospectively derived and validated a clinical prediction rule for recurrent CDI that is simple, reliable, and accurate and can be used to identify high-risk patients most likely to benefit from measures to prevent recurrence.

Tolevamer is not efficacious in the neutralization of cytotoxin in a human gut model of Clostridium difficile infection

The efficacy of tolevamer, a nonantimicrobial styrene derivative toxin-binding agent, in treating simulated Clostridium difficile infection in an in vitro human gut model was investigated. Tolevamer reduced neither the duration nor magnitude of cytotoxin activity by C. difficile, reflecting poor efficacy observed in recent phase III clinical trials.

New agents for Clostridium difficile-associated disease

BACKGROUND

Clostridia-derived diseases, in particular C. difficile-associated disease (CDAD), have been increasing in incidence, severity, and morbidity. The mainstay of treatment options has relied upon metronidazole and vancomycin, but these treatments routinely result in high relapse rates (20%) and, in the case of metronidazole, decreasing efficacy.

OBJECTIVE

Evaluate and compare the current clinical and preclinical therapies of CDAD.

METHODS

RESULTS/CONCLUSION

The new antibiotics in development and preclinical development reflect next-generation versions of older drugs or two new mechanism-of-action class drugs (OPT-80, REP3123). Based on the current preclinical and clinical data, the next-generation drugs impart only a subtle difference from the intrinsic weaknesses of their genre. In contrast, OPT-80 and REP3123 seem to be differentiated.

The management of Clostridium difficile infection

INTRODUCTION/BACKGROUND

Clostridium difficile is the commonest cause of nosocomial diarrhoea. The epidemiology and clinical phenotype of the disease has dramatically changed with the global emergence of a virulent strain of C. difficile.

SOURCE

This review was compiled using data from individual studies and review articles identified from PubMed. The retrieved articles were also examined for additional references.

AREAS OF AGREEMENT

Appropriate and timely infection control measures are required to control C. difficile infection (CDI) in the hospital environment, and either oral metronidazole or vancomycin remains the mainstay of treatment depending on the severity of infection.

AREAS OF CONTROVERSY

The optimal method for diagnosing CDI remains unclear, as does the best therapeutic strategy for the management of multiple relapses. GROWING POINTS/AREAS TIMELY FOR DEVELOPING RESEARCH: Studies of new antimicrobial agents with activity against C. difficile are required to improve the management of multiply relapsing disease. The use of novel therapeutic approaches that do not require antimicrobials requires urgent research, including the use of immunological or vaccine-based regimen, bacteriotherapy or C. difficile-specific bacteriophages.

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.

[Clostridium-difficile-associated diarrhea]

Clostridium difficile is the most frequent cause of nosocomial diarrhea and is a significant cause of morbidity among hospitalized patients. The inflammation is produced as a result of a non-specific response to toxins. In the last few years, a hypervirulent strain, NAP1/BI/027, has been reported. Symptoms usually consist of abdominal pain and diarrhea. The diagnosis should be suspected in any patient who develops diarrhea during antibiotic therapy or 6-8 weeks after treatment. Diagnosis should be confirmed by the detection of CD toxin in stool and by colonoscopy in special situations. The treatment of choice is metronidazole or vancomycin. In some patients who do not respond to this therapy or who have complications, subtotal colectomy may be required. Relapse is frequent and must be distinguished from reinfection. Prevention and control in healthcare settings requires careful attention.

A prospective study of risk factors and historical trends in metronidazole failure for Clostridium difficile infection

BACKGROUND & AIMS

Recent studies of Clostridium difficile infection (CDI) have indicated a dramatic increase in metronidazole failure. The aims of this study were to compare current and historical rates of metronidazole failure and to identify risk factors for metronidazole failure.

METHODS

Eighty-nine patients with CDI in 2004 to 2006 were followed for 60 days and were compared with a historical cohort of 63 CDI patients studied prospectively in 1998. Metronidazole failure was defined as persistent diarrhea after 10 days of therapy or a change of therapy to vancomycin. Stool samples were analyzed for the presence of the North American pulsed-field gel electrophoresis type-1 (NAP-1) strain.

RESULTS

Metronidazole failure rates were 35% in both cohorts. There was no difference in the median time to resolution of diarrhea (8 vs 5 d; P = .52) or the proportion with >10 days of diarrhea (35% vs 29%; P = .51). Risk factors for metronidazole failure included recent cephalosporin use (odds ratio [OR], 32; 95% confidence interval [CI], 5-219), CDI on admission (OR, 23; 95% CI, 3-156), and transfer from another hospital (OR, 11; 95% CI, 2-72). The frequency of NAP-1 infection in patients with and without metronidazole failure was similar (26% vs 21%; P = .67).

CONCLUSIONS

We found no difference in metronidazole failure rates in 1998 and 2004 to 2006. Patients with recent cephalosporin use, CDI on admission, and transfer from another hospital were more likely to metronidazole failure. Infection with the epidemic NAP-1 strain was not associated with metronidazole failure in endemic CDI.

Antibiotic-associated diarrhea: epidemiology, trends and treatment

A common complication of antibiotic use is the development of gastrointestinal disease. This complication ranges from mild diarrhea to pseudomembranous colitis. Outbreaks of antibiotic-associated diarrhea (AAD) may also occur in healthcare settings, usually caused by Clostridium difficile. AAD typically occurs in 5-35% of patients taking antibiotics and varies depending upon the specific type of antibiotic, the health of the host and exposure to pathogens. The pathogenesis of AAD may be mediated through the disruption of the normal microbiota resulting in pathogen overgrowth or metabolic imbalances. The key to addressing AAD is prompt diagnosis followed by effective treatment and institution of control measures. Areas of active research include the search for other etiologies and more effective treatments.

Toxin-binding treatment for Clostridium difficile: a review including reports of studies with tolevamer

Clostridium difficile represents an increasing threat to patients, mainly as a hospital-acquired infection causing antibiotic-associated colitis (AAC). The emergence of a new more virulent strain in North America and Europe has been linked to increased morbidity and mortality. For a long period of time the only available therapeutic options were oral vancomycin and metronidazole. However, both of these antibiotics have limitations either in terms of efficacy, cost, formulation, side effects or the risk of emerging antibiotic resistance among enterococci. Clostridium difficile produces two powerful toxins (A and B) that are responsible for the entire clinical spectrum associated with AAC. As this is exclusively a toxin-mediated disease, agents with the potential of binding these targets have been tested. Data on polymer-based toxin-binding agents such as cholestyramine, Synsorb 90 and tolevamer, designed to target specific bacterial toxins, will be reviewed. Bovine colostrum and specific human monoclonal antibodies aimed at neutralising toxin A, although still at an early stage of development, are also new avenues to be explored. Non-antibiotic-based therapies might become the best available option for a condition almost always caused by antibiotics.

Recent advances in Clostridium difficile-associated disease

The main purpose of this article is to review recent developments in the management of acute and recurrent Clostridium difficile-associated disease, with consideration of existing and new antibiotic and non-antibiotic agents for treatment. Details of the current developmental stage of new agents are provided and the role of surgery in the management of severe disease is discussed. Infection control measures considered comprise prudent use of antimicrobials, prevention of cross-infection and surveillance. Other topics that are covered include the recent emergence of an epidemic hypervirulent strain, pathogenesis, clinical presentation and approaches to rapid diagnosis and assessment of the colonic disease.

Tolevamer, an anionic polymer, neutralizes toxins produced by the BI/027 strains of Clostridium difficile

Clostridium difficile-associated diarrhea (CDAD) is caused by the toxins the organism produces when it overgrows in the colon as a consequence of antibiotic depletion of normal flora. Conventional antibiotic treatment of CDAD increases the likelihood of recurrent disease by again suppressing normal bacterial flora. Tolevamer, a novel toxin-binding polymer, was developed to ameliorate the disease without adversely affecting normal flora. In the current study, tolevamer was tested for its ability to neutralize clostridial toxins produced by the epidemic BI/027 strains, thereby preventing toxin-mediated tissue culture cell rounding. The titers of toxin-containing C. difficile culture supernatants were determined using confluent cell monolayers, and then the supernatants were used in assays containing dilutions of tolevamer to determine the lowest concentration of tolevamer that prevented > or =90% cytotoxicity. Tolevamer neutralized toxins in the supernatants of all C. difficile strains tested. Specific antibodies against the large clostridial toxins TcdA and TcdB also neutralized the cytopathic effect, suggesting that tolevamer is specifically neutralizing these toxins and that the binary toxin (whose genes are carried by the BI/027 strains) is not a significant source of cytopathology against tissue culture cells in vitro.

A new formulation of tolevamer, a novel nonantibiotic polymer, is safe and well-tolerated in healthy volunteers: a randomized phase I trial

AIMS

To evaluate the safety and tolerability of a new oral solution formulation of tolevamer potassium sodium, a nonantibiotic polymer that binds Clostridium difficile toxins A and B.

METHODS

This phase 1 randomized, double-blind, placebo-controlled study evaluated four doses of tolevamer potassium sodium in 40 healthy volunteers using a sequential dose escalation paradigm and doses of 6, 9, 12 and 15 g day(-1) for 9 days. Within each 10 patient cohort, eight patients received active treatment and two matching placebo. Placebo subjects were pooled to provide eight per arm. All subjects received three times daily dosing on days 2-8 as well as a loading dose (a single dose equal to the total daily dose) either on day 1 or day 9.

RESULTS

All 40 subjects completed the study per protocol. Treatment-emergent adverse events (TEAEs) were generally mild, transient, and resolved without sequelae. There were no serious AEs or deaths. There was no relationship detected between dose and the incidence of TEAEs, whether drug-related (all gastrointestinal disorders) or not. No clinically significant changes in laboratory parameters, including serum and urinary potassium concentrations, vital signs, and results of physical examination, were observed. A small but statistically significant reduction in 24 h urine potassium excretion was seen in the 15 g day(-1) dose group, and on day 10 in the 6 g day(-1) group.

CONCLUSIONS

Tolevamer oral solution administered for 9 days at total daily doses up to 15 g, with loading doses of up to 15 g, was generally safe and well-tolerated in healthy volunteers.

Treatment of Clostridium difficile infection

Recent outbreaks of Clostridium difficile infection (CDI) in North America have been due to a more virulent, possibly more resistant strain that causes more-severe disease, making prompt recognition of cases and optimal management of infection essential for a successful therapeutic outcome. Treatment algorithms are presented to help guide the management of patients with CDI. Metronidazole has been recommended as initial therapy since the late 1990s and continues to be the first choice for all but seriously ill patients and those with complicated or fulminant infections or multiple recurrences of CDI, for whom vancomycin is recommended. Other options for recurrent CDI, such as probiotics and currently available anion-exchange resins, have limited efficacy and are potentially harmful. Intravenous immunoglobulin may benefit patients with refractory, recurrent, or severe disease, but no controlled data are available. Two antimicrobials available in the United States for other indications, nitazoxanide and rifaximin, have been used successfully for CDI treatment but, like metronidazole, lack United States Food and Drug Administration approval for this indication. Experimental treatments currently in clinical development include a toxin-binding polymer, tolevamer; 2 poorly absorbed antimicrobials, OPT-80 (formerly known as Difimicin) and ramoplanin; monoclonal antibodies; and a C. difficile vaccine.

Update on the changing epidemiology of Clostridium difficile-associated disease

In the past, Clostridium difficile-associated disease (CDAD) was thought of mainly as a nosocomial disease associated with the use of broad-spectrum antibiotics, but its epidemiology seems to be changing. Since 2002, outbreaks of severe CDAD associated with increased mortality and reduced effectiveness of treatment with metronidazole have focused attention on this challenging pathogen. A fluoroquinolone-resistant strain of C. difficile (BI/NAP1/027) has been predominantly associated with these outbreaks. Changes in the epidemiology of CDAD include the emergence of new at-risk populations and the increased incidence of the disease. Infection control programs and more effective treatments offer hope that future outbreaks of CDAD can be controlled.

Bench-to-bedside review: Clostridium difficile colitis

In recent years, the incidence and severity of Clostridium difficile-associated disease (CDAD) have increased dramatically. Beginning in 2000, widespread regional outbreaks associated with a previously uncommon hypervirulent strain of C. difficile have occurred in North America and Europe. Most likely because of increased toxin production as well as other virulence factors, this epidemic strain has caused more severe and refractory disease leading to complications, including intensive care unit admission, colectomies, and death. Worldwide increasing use of fluoroquinolones and cephalosporins has likely contributed to the proliferation of this epidemic strain, which is highly resistant to both. The elderly have been disproportionately affected by CDAD, but C. difficile has also recently emerged in populations previously considered to be at low risk, including healthy outpatients and peripartum women, although it is unknown if these cases are related to the epidemic strain. Nevertheless, transmission within hospitals is the major source of C. difficile acquisition, and previous or concurrent antimicrobial use is almost universal among cases. Applying current evidence-based strategies for management and prevention is critically important, and clinicians should maintain an awareness of the changing epidemiology of CDAD and take measures to reduce the risk of disease in patients.

Clostridium difficile

CASE STUDY

George, a 55-year-old retired businessman with a diagnosis of myelofibrosis, underwent an allogeneic stem cell transplantation from his human leukocyte antigen-matched brother in June 2006. He was admitted to the hospital for a possible flare of graft-versus-host disease (GVHD) of the gut. His medications included tacrolimus, budesonide, and bechlamethasone for immunosuppression and pantoprazole. A stool sample was positive for Clostridium difficile toxin A on October 31, 2006, and he was started on oral metronidazole.

Outcomes of Clostridium difficile-associated disease treated with metronidazole or vancomycin before and after the emergence of NAP1/027

OBJECTIVE

To reassess the comparative efficacy of vancomycin versus metronidazole in the treatment of Clostridium difficile-associated disease (CDAD) after the emergence in 2003 of the hypervirulent NAP1/027 strain.

METHODS

A retrospective cohort study was conducted in a tertiary-care Canadian hospital among 1,616 patients treated initially with metronidazole (N=1,360), vancomycin (N=219), or both (N=37), between 1991 and 2006, and followed for 60 days after diagnosis. Primary outcome was severe/complicated CDAD (SC-CDAD) defined as any of: (a) death within 30 days, (b) septic shock, (c) megacolon, (d) perforation, or (e) emergency colectomy. Adjusted odds ratios (AOR) and their 95% confidence intervals (CI) were calculated, stratifying into pre-epidemic (1991-2002) and epidemic (2003-2006) periods. Secondary outcome was recurrence within 60 days.

RESULTS

Risk factors for SC-CDAD were the same in both periods: age>or=65 yr, male sex, immunosuppression, hospital acquisition, tube feeding, short duration of diarrhea, fever, elevated leukocytosis, or creatinine. Adjusting for confounders and using metronidazole therapy as baseline, vancomycin therapy was associated with a lower probability of developing SC-CDAD in 1991-2002 (AOR 0.21, 95% CI 0.05-0.99, P=0.048) but not during 2003-2006 (AOR 0.90, 95% CI 0.53-1.55, P=0.71). For both metronidazole and vancomycin, risk of recurrence increased in 2003-2004 but decreased in 2005-2006.

CONCLUSIONS

Loss of superiority of vancomycin over metronidazole coincided with the emergence of NAP1/027. Toxin hyperproduction by NAP1/027 might be such that the disease follows its natural course. Novel therapeutic approaches are needed. The higher risk of recurrence in 2003-2004 probably reflected reinfections rather than relapses.

Treatment strategies for recurrent and refractory Clostridium difficile-associated diarrhea

Clostridium difficile, the most common nosocomial infection of the GI tract, has become a bigger threat with the emergence of a hypervirulent strain. C. difficile-associated diarrhea (CDAD) is usually a consequence of antibiotic therapy or chemotherapy, but sporadic cases occur, and an increase in severe sporadic cases is of great concern. Epidemics of CDAD with high morbidity and mortality have been documented in the USA, Canada and Europe, making accurate diagnosis, effective therapy and strategies for prevention more important than ever. Treatment of refractory and recurrent CDAD remain therapeutic challenges. Improved treatments are needed; several new drugs are currently in trials.

Clinical management of Clostridium difficile-associated disease

The incidence of Clostridium difficile-associated disease (CDAD) and its serious complications (including colectomy and death) have been increasing worldwide. This phenomenon is strongly associated with the appearance of a new "hypervirulent" strain in several countries. More-effective strategies are needed for the prevention and treatment of this entity. This article will review the current approaches using antimicrobials, probiotics, immunomodulation, surgery, and miscellaneous adjuvants to prevent and treat this infection.

Clostridium difficile: emergence of hypervirulence and fluoroquinolone resistance

Clostridium difficile is a well-known cause of sporadic and healthcare-associated diarrhea. Multihospital outbreaks due to a single strain and outbreaks associated with antibiotic selective pressure, especially clindamycin, have been well documented. Severe cases and fatalities from C. difficile are uncommon. The recent global emergence of a hypervirulent strain containing binary toxin (Toxinotype III ribotype 027), with or without deletion in a regulatory gene (tcdC gene), together with high-level resistance to third generation fluoroquinolones, has been associated with increased morbidity and mortality. Although the defective regulatory gene locus is associated with increased toxin production in vitro, the in vivo significance of this mutation and of the binary toxin remains undefined. To date, treatment strategies have not evolved in response to the emergence of this hypervirulaent strain. We provide a critical, quantitative summary of the evolving clinical and molecular epidemiology of C. difficile along with implications relevant to future treatment strategies.

Advances in defining etiology and new therapeutic approaches in acute diarrhea

Defining etiology of acute diarrhea is critical to disease therapy and prevention. In this review we look at recent developments in etiologic agents of acute diarrhea and advances in therapy and prevention of the illness. Newly appreciated agents include enterotoxigenic Bacteroides fragilis, Klebsiella oxytoca and Laribacter hongkongensis. Atypical enteropathogenic E. coli (EPEC) strains lacking the gene for epithelial attachment appear to be more important as causes of diarrhea than traditional EPEC strains. Enterotoxigenic E. coli and enteroaggregative E. coli diarrhea known to be important abroad, have recently been shown to occur in the United States. Non-O157:H7 strains of Shiga toxin-producing E. coli are increasing and infrequently are being sought. There is currently a serious epidemic of nosocomial diarrhea due to a fluoroquinolone-resistant and more virulent and difficult to treat strain of C. difficile. Rotavirus vaccine development should lead to reduction of infant gastroenteritis mortality in infants living in developing regions. Noroviruses produce outbreaks of water- and food-borne disease but show broad genetic diversity. Reduced osmolarity oral rehydration treatment (ORT) and recombinant human lactoferrin/lysozyme plus rice-based ORT effectively treat acute diarrhea. Probiotics were shown to be effective in preventing antibiotic associated- and C. difficile-diarrhea. Rifaximin prevents and azithromycin effectively treats travelers' diarrhea.

Clostridium difficile: changing epidemiology and new treatment options

PURPOSE OF REVIEW

The review summarizes changes in the epidemiology and treatment of Clostridium difficile-associated disease.

RECENT FINDINGS

Recent outbreaks of Clostridrium difficile-associated diarrhoea with increased severity, high relapse rate and significant mortality, have been related to the emergence of a new, hypervirulent C. difficile strain in north America, Japan and Europe. Definitions have been proposed by the European Centre for Disease Prevention and Control to identify severe cases of Clostridrium difficile-associated diarrhoea and to differentiate community-acquired cases from nosocomial-acquired cases. The emerging strain is referred to as North American pulsed-field type 1 and polymerase chain reaction ribotype 027. The emerging strain has also been detected in calf diarrhoea and ground meat samples in Canada. Attempts to prevent outbreaks caused by type 027 should focus on controlling the overall use of antibiotics, and high-risk antibiotics such as cephalosporins, clindamycin and fluoroquinolones. Several new antibiotic and non-antibiotic alternatives have become available; there is currently no place for probiotic treatments. Patients who suffer multiple relapses of C. difficile-associated diarrhoea present a major therapeutic challenge.

SUMMARY

The early recognition of Clostridrium difficile-associated diarrhoea caused by NAP1/027 is necessary to start rapid treatment, to prevent complications, and to prevent further spread of the bacterium.

Clostridium difficile: recent epidemiologic findings and advances in therapy

Clostridium difficile-associated disease (CDAD) has become an important public health problem. The causative organism is acquired by the oral route from an environmental source or by contact with an infected person or a health care worker who serves as a vector. Disruption of the bowel microflora, generally by antibiotics, creates an environment that allows C. difficile to proliferate. Organisms produce toxins A and B, which cause intense inflammation of the colonic mucosa. The syndrome that results includes severe diarrhea, fever, abdominal pain, and leukocytosis. A new strain of C. difficile has become prevalent in the United States, Canada, and the United Kingdom. Identified by pulsed-field gel electrophoresis (PFGE), this strain is called North America PFGE type 1, abbreviated as NAP-1. Clostridium difficile NAP-1 characteristically generates large amounts of toxins A and B, as well as an additional binary toxin and is associated with enhanced morbidity and a poor response to antibiotic therapy. Mild cases of CDAD may respond to cessation of antibiotic therapy, perhaps related to antibody production by the infected person, but most infected persons require antimicrobial therapy. Vancomycin has been approved by the United States Food and Drug Administration for treatment of CDAD, but reluctance to use this antibiotic in the hospital setting has led to reliance on metronidazole as first-line therapy. Recent studies show a high rate of failure, due either to infection by NAP-1 or to the presence, in hospitals, of older and sicker adults who have been treated with many broad-spectrum antibiotics. Nitazoxanide, bacitracin, teicoplanin, and fusidic acid are additional agents that have published efficacy for this indication in humans. Rifaximin and PAR-101 are under investigation. Other therapies, including polymers that bind C. difficile toxin and monoclonal antibodies to toxins, and preventive measures such as toxoid vaccines are also under study.

Clostridium difficile—Associated Diarrhea, an Emerging Epidemic: Therapeutic Options

Clostridum difficile—associated disease (CDAD) is the leading cause of infectious diarrhea and is associated with considerable morbidity and mortality. The incidence is estimated to range from 3.4 to 8.4 cases per 1000 hospital admissions, and it has become a growing problem at many institutions. Treatment options for CDAD are limited due to a paucity of new pharmacologic agents and studies examining other potential treatments. Historically oral metronidazole and oral vancomycin have been used as first-line agents in the treating CDAD, however recent reports of treatment failure and recurrence with these agents have surfaced. These reports illustrate a need for novel pharmacologic agents and a thorough review of currently available agents that may have activity against C difficile. Available data on the treatment of CDAD were extracted and reviewed to outline the appropriate management of CDAD.

Clostridium difficile-associated disease: changing epidemiology and implications for management

Clostridium difficile-associated disease (CDAD) is increasingly being reported in many regions throughout the world. The reasons for this are unknown, are likely to be multifactorial, and are the subject of several current investigations. In addition to the upsurge in frequency of CDAD, an increased rate of relapse/recurrence, disease severity and refractoriness to traditional treatment have also been noted. Moreover, severe disease has been reported in non-traditional hosts (e.g. younger age, seemingly healthy, non-institutionalised individuals residing in the community, and some without apparent antimicrobial exposure). A previously uncommon and more virulent strain of C. difficile has been reported at the centre of multiple transcontinental outbreaks. The appearance of this more virulent strain, in association with certain environmental and antimicrobial exposure factors, may be combining to create the 'perfect storm'. It is human nature to be reactive; however, the successful control of C. difficile will require healthcare systems (including administrators, and leadership within several departments such as environmental services, infection control, infectious diseases, gastroenterology, surgery, microbiology and nursing), clinicians, long-term care and rehabilitation facilities, and patients themselves to be proactive in a collaborative effort. Guidelines for the management of CDAD were last published over a decade ago, with the next iteration due in the fall (autumn) of 2007. Several newer therapies are under investigation but it is unclear whether they will be superior to current treatment options.

Antibiotic treatment for Clostridium difficile-associated diarrhea in adults

BACKGROUND

Clostridium difficile (C. difficile) is recognized as a frequent cause of antibiotic-associated diarrhea and colitis.

OBJECTIVES

The aim of this review is to establish the efficacy of antibiotic therapy for C. difficile-associated diarrhea (CDAD), to identify the most effective antibiotic treatment for CDAD in adults and to determine the need for stopping the causative antibiotic during therapy.

SEARCH STRATEGY

MEDLINE (1966 to 2006), EMBASE (1980 to 2006), Cochrane Central Database of Controlled Trials and the Cochrane IBD Review Group Specialized Trials Register were searched using the following search terms: "pseudomembranous colitis and randomized trial"; "Clostridium difficile and randomized trial"; "antibiotic associated diarrhea and randomized trial".

SELECTION CRITERIA

Only randomized, controlled trials assessing antibiotic treatment for CDAD were included in the review. Probiotic trials are excluded. The following outcomes were sought: initial resolution of diarrhea; initial conversion of stool to C. difficile cytotoxin and/or stool culture negative; recurrence of diarrhea; recurrence of fecal C. difficile cytotoxin and/or positive stool culture; patient response to cessation of prior antibiotic therapy; sepsis; emergent surgery: fecal diversion or colectomy; and death.

DATA COLLECTION AND ANALYSIS

Data were analyzed using the MetaView statistical package in Review Manager. For dichotomous outcomes, relative risks (RR) and 95% confidence intervals (CI) were derived from each study. When appropriate, the results of included studies were combined for each outcome. For dichotomous outcomes, pooled RR and 95% CI were calculated using a fixed effect model, except where significant heterogeneity was detected, at which time the random effects model was used. Data heterogeneity was calculated using MetaView.

MAIN RESULTS

Twelve studies (total of 1157 participants) involving patients with diarrhea who recently received antibiotics for an infection other than C. difficile were included. The definition of diarrhea ranged from at least two loose stools per day with an associated symptom such as rectal temperature > 38 (o)C, to at least six loose stools in 36 hours. Eight different antibiotics were investigated: vancomycin, metronidazole, fusidic acid, nitazoxanide, teicoplanin, rifampin, rifaximin and bacitracin. In paired comparisons, no single antibiotic was clearly superior to others, though teicoplanin, an antibiotic of limited availability and great cost, showed in some outcomes significant benefit over vancomycin and fusidic acid, and a trend towards benefit compared to metronidazole. Only one placebo controlled trial was done and no conclusions can be drawn from it due to small size and classification error. Only one study investigated synergistic antibiotic combination, metronidazole and rifampin, and there was no advantage to the drug combination.

AUTHORS' CONCLUSIONS

Current evidence leads to uncertainty whether mild CDAD needs to be treated. Patients with mild CDAD may resolve their symptoms as quickly without treatment. The only placebo-controlled study shows vancomycin's superior efficacy. However, this result should be treated with caution due to the small number of patients enrolled and the poor methodological quality of the trial. The Johnson study of asymptomatic carriers also shows that placebo is better than vancomycin or metronidazole for eliminating C. difficile in stool during follow-up. If one does decide to treat, then two goals of therapy need to be kept in mind: improvement of the patient's clinical condition and prevention of spread of C. difficile infection to other patients. Given these two considerations, one should choose the antibiotic that brings both symptomatic cure and bacteriologic cure. In this regard, teicoplanin appears to be the best choice because the available evidence suggests that it is better than vancomycin for bacteriologic cure and has borderline superior effectiveness in terms of symptomatic cure. Teicoplanin is not readily available in the United States, which must be taken into account when making treatment decisions in that country.

The challenges posed by reemerging Clostridium difficile infection

There have been recent, marked increases in the incidence and severity of Clostridium difficile-associated disease (CDAD). These may be attributable to the emergence of a hypervirulent strain of C. difficile that produces increased levels of toxins A and B, as well as an extra toxin known as "binary toxin." This previously uncommon strain has become epidemic, coincident with its development of increased resistance to fluoroquinolones, the use of which is increasingly associated with CDAD outbreaks. Although not necessarily related to this epidemic strain, unusually severe CDAD has been reported in populations that had previously been thought to be at low risk, including peripartum women and healthy persons living in the community. Challenges posed by the changing epidemiology of CDAD are compounded by current limitations in diagnostic testing, treatment, and infection control. Overcoming these challenges and limitations will require a concerted effort from a variety of sources, including an ongoing partnership between infectious disease clinicians and public health professionals.

Association between IgG2 and IgG3 subclass responses to toxin A and recurrent Clostridium difficile-associated disease

BACKGROUND & AIMS

Individuals who mount a significant serum immunoglobulin (Ig)G response to toxin A are protected against recurrent Clostridium difficile-associated disease (CDAD). We investigated whether humoral immune deficiencies and/or specific IgG subclass responses are associated with recurrent CDAD.

METHODS

We compared the clinical characteristics and humoral immune responses of 13 patients with recurrent CDAD with 13 matched controls with a single CDAD episode. We measured the serum IgG titers to tetanus and diphtheria toxoids, as well as total and toxin A- and toxin B-specific serum IgG, IgA, and IgG subclass concentrations.

RESULTS

There were no differences between the single and recurrent CDAD subjects in terms of age, sex, ethnicity, or other potential confounding variables. The total duration of diarrhea in patients with recurrent CDAD was greater (median, 62 vs 17 days; P = .005). IgG titers to tetanus and diphtheria toxoids, total IgG, and IgG subclass levels were similar in both groups. The total IgA was somewhat lower in those with recurrent CDAD (204 vs 254 mg/dL; P = .05). IgA, IgG, IgG1, and IgG4 anti-toxin A and anti-toxin B levels were similar in both groups. However, IgG2 and IgG3 anti-toxin A levels were significantly lower in the recurrent group (P = .01 and .001, respectively).

CONCLUSIONS

Subjects with recurrent CDAD did not show evidence of widespread humoral immune deficiency or of IgG subclass deficiency. Their low serum IgG anti-toxin A concentrations reflected selectively reduced IgG2 and IgG3 subclass responses. Measurement of specific IgG2/3 anti-toxin A may be useful in selecting patients for treatment with agents to prevent recurrent CDAD.

Clostridium difficile colitis that fails conventional metronidazole therapy: response to nitazoxanide

OBJECTIVES

Clostridium difficile-associated disease has increased in incidence and severity. Recommended treatments include metronidazole and vancomycin. Recent investigations, however, document the failure of metronidazole to cure a substantial proportion of patients with Clostridium difficile colitis, but oral administration of vancomycin raises concerns over selection of antibiotic-resistant organisms in the hospital environment. We have recently shown that nitazoxanide is as effective as metronidazole in initial therapy for C. difficile colitis. We hypothesized that this drug might be effective in treating patients who fail therapy with metronidazole.

METHODS

In the present study, we identified 35 patients who failed treatment with metronidazole for C. difficile colitis; failure was defined as either no improvement in symptoms or signs of disease (28 patients) after >or= 14 days of treatment with metronidazole or prompt recurrence on at least two occasions after initially responding to such treatment (seven patients). These patients were ill with numerous co-morbidities. Nitazoxanide, 500 mg twice daily, was given for 10 days; results from all patients are included.

RESULTS

Twenty-six (74%) of 35 patients responded to nitazoxanide, of whom seven later had recurrent disease, yielding a cure rate of 19 of 35 (54%) from initial therapy. Three who initially failed and one who had recurrent disease were re-treated with, and responded to, nitazoxanide. Thus, the aggregate cure with nitazoxanide in this difficult-to-treat population was 23 of 35 (66%).

CONCLUSIONS

Nitazoxanide appears to provide effective therapy for patients with C. difficile colitis who fail treatment with metronidazole.

Past, present, and future therapies for Clostridium difficile-associated disease

OBJECTIVE

To describe and examine the past, present, and potential future treatment options for Clostridium difficile-associated disease (CDAD).

DATA SOURCES

A PubMed search, restricted to English-language articles concerning CDAD, was conducted (1965-October 2006) using the key words Clostridium difficile, diarrhea, vancomycin, metronidazole, immunoglobulin, and recurrence. Additional references were located through review of the bibliographies of cited articles and by visiting www.clinicaltrials.gov.

STUDY SELECTION AND DATA EXTRACTION

Articles related to the clinical manifestations, diagnosis, and treatment of CDAD, as well as articles addressing current issues related to CDAD, were included.

DATA SYNTHESIS

There have been many investigations into CDAD because of the recent increased incidence and morbidity and mortality of the disease. Various studies examining the changing epidemiology and pathogenicity of C. difficile, as well as new therapies for CDAD with agents such as tolevamer and nitazoxanide, are ongoing. In addition, researchers are investigating probiotics and vaccines to evaluate their effectiveness in preventing CDAD and/or preventing recurrences of CDAD. Studies assessing therapies for refractory CDAD are lacking, although case reports have been published citing treatment strategies using vancomycin enemas, intravenous metronidazole, colestipol and cholestyramine, fecal enemas, bowel irrigation, and immunoglobulin. Furthermore, judicious use of antimicrobials, contact precautions, and adequate environmental cleaning are being evaluated in healthcare institutions as methods for controlling and preventing the spread of C. difficile.

CONCLUSIONS

Oral metronidazole is the drug of choice for an initial CDAD episode. Oral vancomycin is an option for patients who cannot take or fail treatment with oral metronidazole. Clinical trials are necessary to define the therapy for initial CDAD that is most appropriate and produces lower recurrence rates compared with oral metronidazole or vancomycin treatment. Moreover, appropriate treatment for patients with multiple recurrences of or refractory CDAD needs to be determined. More studies are also needed assessing prevention of recurrences of CDAD.

Review article: tolevamer, a novel toxin-binding polymer: overview of preclinical pharmacology and physicochemical properties

BACKGROUND

Tolevamer is a novel toxin-binding polymer that is currently being investigated in clinical trials for the treatment of patients who have Clostridium difficile-associated diarrhoea.

AIMS

To summarize the results of in vitro and in vivo preclinical studies of tolevamer. In contrast to antibiotics, tolevamer binds C. difficile toxins to interrupt toxin-mediated intestinal inflammation and tissue damage, and does not demonstrate direct antimicrobial activity.

METHODS

Pharmacokinetics/pharmacodynamics were studied in rats and dogs; efficacy was studied in a hamster model.

RESULTS

Studies in rats and dogs indicate that tolevamer is essentially non-absorbed from the gastrointestinal tract and show that drug interactions with commonly used therapies are unlikely. Pharmacologic studies indicate that tolevamer reduces disease severity and recurrence rates in the hamster model of C. difficile-associated diarrhoea and blocks the enterotoxic effects of toxin A in rat ileum. The binding parameters calculated for the interaction of tolevamer with toxins A and B provide a reasonable physicochemical model that supports the potential clinical utility of tolevamer.

CONCLUSIONS

These preclinical results are consistent with the effectiveness and safety profile of tolevamer observed in clinical studies in patients with C. difficile-associated diarrhoea.

Antimicrobial therapy of Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) is the most common etiologically-defined cause of hospital-acquired diarrhea. Caused by the toxins of certain strains of C difficile, CDAD represents a growing concern, with epidemic outbreaks in some hospitals where very aggressive and difficult-to-treat strains have recently been found. Incidence of CDAD varies ordinarily between 1 to 10 in every 1,000 admissions. Evidence shows that CDAD increases morbidity, length of stay, and costs. This article described the clinical manifestations of CDAD, related risk factors, considerations for confirming CDAD, antimicrobial and non-antimicrobial treatment of CDAD, and issues related to relapses. The article concludes with a discussion of recent epidemic outbreaks involving CDAD.