Rifalazil treats and prevents relapse of clostridium difficile-associated diarrhea in hamsters

Budesonide, an anti-inflammatory drug, exacerbate clostridioides difficile colitis in mice

BACKGROUND AND AIMS

Clostridioides difficile infection (CDI) induces intense acute inflammatory responses through toxin release. A combination of antibiotic and anti-inflammatory agents is sometimes recommended in severe, non-responsive cases, although clinical trials have been inconclusive, raising concerns about potential complications. This study aims to investigate the effect of budesonide and mesalamine in the treatment of CDI in a murine model, by evaluating the combination of fidaxomicin and these anti-inflammatory drugs.

METHOD

C57BL/6 J female mice pretreated with an antimicrobial mixture were challenged with C. difficile VPI 10463 or culture media by gavage. After the challenge, mice received placebo, fidaxomicin alone (20 mg/kg), or fidaxomicin combined with mesalamine (200, 400 mg/kg) or budesonide (0.2, 1, 10 mg/kg) for 5 days. The mice were monitored for 7 days with weight and survival. Colon and cecum tissues were harvested for histological assessment.

RESULTS

CDI of mice caused 80% mortality. Fidaxomicin completely protected against CDI in all parameters (weight, survival and pathscores). Mortality rates were up to 90%, 70% in budesonide(10 mg/kg) and mesalamine (400 mg/kg) treatment group, respectively. Budesonide (0.02,0.1 and 1 mg/kg) adjunction to fidaxomicin worsened the disease outcome according to all tested parameters. While mesalamine in combination with fidaxomicin (200, 400 mg/kg) did not lead to any deaths during CDI treatment, it did not provide additional benefits.

CONCLUSIONS

Anti-inflammatory drugs including corticosteroid therapy may worsen the incidence and severity of CDI in this mouse model. These studies may have important clinical implications for understanding the role of anti-inflammatory/ corticosteroid therapy in CDI and inflammatory bowel disease management.

A High-Carbohydrate Diet Prolongs Dysbiosis and Clostridioides difficile Carriage and Increases Delayed Mortality in a Hamster Model of Infection

Studies using mouse models of Clostridioides difficile infection (CDI) have demonstrated a variety of relationships between dietary macronutrients on antibiotic-associated CDI; however, few of these effects have been examined in more susceptible hamster models of CDI. In this study, we investigated the effect of a high-carbohydrate diet previously shown to protect mice from CDI on the progression and resolution of CDI in a hamster disease model, with 10 animals per group. Hamsters fed the high-carbohydrate diet developed distinct diet-specific microbiomes during antibiotic treatment and CDI, with lower diversity, persistent C. difficile carriage, and delayed microbiome restoration. In contrast to CDI protection in mice, most hamsters fed a high-carbohydrate diet developed fulminant CDI including several cases of late-onset CDI, that were not observed in hamsters fed a standard lab diet. We speculate that prolonged high-carbohydrate diet-specific dysbiosis in these animals allowed C. difficile to persist in the gut of the animals where they could proliferate postvancomycin treatment, leading to delayed CDI onset. This study, along with similar studies in mouse models of CDI, suggests some high-carbohydrate diets may promote antibiotic-associated dysbiosis and long-term C. difficile carriage, which may later convert to symptomatic CDI. IMPORTANCE The effects of diet on CDI are not completely known. Here, we used a high-carbohydrate diet previously shown to protect mice against CDI to assess its effect on a hamster model of CDI and paradoxically found that it promoted dysbiosis, C. difficile carriage, and higher mortality. A common thread in both mouse and hamster experimental models was that the high-carbohydrate diet promoted dysbiosis and long-term carriage of C. difficile, which may have converted to fulminant CDI only in the highly susceptible hamster model system. If diets high in carbohydrates also promote dysbiosis and C. difficile carriage in humans, then these diets might paradoxically increase chances of CDI relapse despite their protective effects against primary CDI.

Application of recombinant antibodies for treatment of Clostridioides difficile infection: Current status and future perspective

Clostridioides difficile (C. difficile), known as the major cause of antibiotic-associated diarrhea, is regarded as one of the most common healthcare-associated bacterial infections worldwide. Due to the emergence of hypervirulent strains, development of new therapeutic methods for C. difficile infection (CDI) has become crucially important. In this context, antibodies have been introduced as valuable tools in the research and clinical environments, as far as the effectiveness of antibody therapy for CDI was reported in several clinical investigations. Hence, production of high-performance antibodies for treatment of CDI would be precious. Traditional approaches of antibody generation are based on hybridoma technology. Today, application of in vitro technologies for generating recombinant antibodies, like phage display, is considered as an appropriate alternative to hybridoma technology. These techniques can circumvent the limitations of the immune system and they can be exploited for production of antibodies against different types of biomolecules in particular active toxins. Additionally, DNA encoding antibodies is directly accessible in in vitro technologies, which enables the application of antibody engineering in order to increase their sensitivity and specificity. Here, we review the application of antibodies for CDI treatment with an emphasis on recombinant fragment antibodies. Also, this review highlights the current and future prospects of the aforementioned approaches for antibody-mediated therapy of CDI.

In vivo efficacy of auranofin in a hamster model of Clostridioides difficile infection

Clostridioides difficile infections (CDIs) are an urgent public health threat worldwide and are a leading cause of morbidity and mortality in healthcare settings. The increasing incidence and severity of infections combined with the scarcity of effective anti-CDI agents has made treatment of CDI very challenging. Therefore, development of new, effective anticlostridial agents remains a high priority. The current study investigated the in vivo efficacy of auranofin in a CDI hamster model. All hamsters treated with auranofin (5 mg/kg) survived a lethal challenge with C. difficile. Furthermore, auranofin (5 mg/kg) was as effective as vancomycin, the drug of choice for treatment of CDIs, against relapsing CDI. Furthermore, auranofin (5 mg/kg) generated a 3.15-log₁₀ reduction (99.97%) in C. difficile count in the cecal contents of hamsters. These results indicate that auranofin warrants further investigation as a new agent to replenish the pipeline of anti-CDI therapeutics.

The Clinical Drug Ebselen Attenuates Inflammation and Promotes Microbiome Recovery in Mice after Antibiotic Treatment for CDI

Clostridium difficile infection (CDI) is an enteric bacterial disease that is increasing in prevalence worldwide. C. difficile capitalizes on gut inflammation and microbiome dysbiosis to establish infection, with symptoms ranging from watery diarrhea to toxic megacolon. We reported that the safe-in-human clinical drug ebselen (ClinicalTrials.gov: NCT03013400, NCT01452607, NCT00762671, and NCT02603081) has biochemical, cell-based, and in vivo efficacy against the toxins of C. difficile. Here, we show that ebselen treatment reduces recurrence rates and decreases colitis in a hamster model of relapsing CDI. Furthermore, ebselen treatment does not alter microbiome diversity and promotes recovery back to that of healthy controls after antibiotic-induced dysbiosis in healthy and C. difficile-infected mice. This increased microbiome recovery upon ebselen treatment correlates with a decrease in host-derived inflammatory markers, suggesting that the anti-inflammatory properties of ebselen, combined with its anti-toxin function, help to mitigate the major clinical challenges of CDI, including recurrence, microbial dysbiosis, and colitis.

Ebselen protects hamsters from tissue damage caused by C. difficile infection

Ebselen treatment reduces reoccurrence of C. difficile infection in hamsters

Ebselen increases recovery of microbiome diversity after antibiotic treatment

Ebselen reduces host inflammation after antibiotic treatment

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.

Effect of the Synthetic Bile Salt Analog CamSA on the Hamster Model of Clostridium difficile Infection

Clostridium difficile infection (CDI) is the leading cause of antibiotic-associated diarrhea and has gained worldwide notoriety due to emerging hypervirulent strains and the high incidence of recurrence. We previously reported protection of mice from CDI using the antigerminant bile salt analog CamSA. Here we describe the effects of CamSA in the hamster model of CDI. CamSA treatment of hamsters showed no toxicity and did not affect the richness or diversity of gut microbiota; however, minor changes in community composition were observed. Treatment of C. difficile-challenged hamsters with CamSA doubled the mean time to death, compared to control hamsters. However, CamSA alone was insufficient to prevent CDI in hamsters. CamSA in conjunction with suboptimal concentrations of vancomycin led to complete protection from CDI in 70% of animals. Protected animals remained disease-free at least 30 days postchallenge and showed no signs of colonic tissue damage. In a delayed-treatment model of hamster CDI, CamSA was unable to prevent infection signs and death. These data support a putative model in which CamSA reduces the number of germinating C. difficile spores but does not keep all of the spores from germinating. Vancomycin halts division of any vegetative cells that are able to grow from spores that escape CamSA.

Establishment of an Endogenous Clostridium difficile Rat Infection Model and Evaluation of the Effects of Clostridium butyricum MIYAIRI 588 Probiotic Strain

Clostridium difficile is well known as an agent responsible for pseudomembranous colitis and antibiotic-associated diarrhea. The hamster model utilizing an oral route for infection of C. difficile has been considered to be the standard model for analysis of C. difficile infection (CDI) but this model exhibits differences to human CDI, most notably as most hamsters die without exhibiting diarrhea. Therefore, we attempted to develop a new non-lethal and diarrheal rat CDI model caused by endogenous C. difficile using metronidazole (MNZ) and egg white. In addition, the effects of probiotic strain Clostridium butyricum MIYAIRI 588 (CBM) on CDI were examined using this model. Syrian Golden hamsters received clindamycin phosphate orally at 30 mg/kg on 5 days before challenge with either C. difficile VPI10463 (hypertoxigenic strain) or KY34 (low toxigenic clinical isolate). Mortality and the presence of diarrhea were observed twice a day for the duration of the experiment. Wistar rats received 10% egg white dissolved in drinking water for 1 week ad libitum following intramuscular administration of 200 mg/kg MNZ twice a day for 3 days. Diarrhea score was determined for each day and fecal water content, biotin concentration, and cytotoxin titer in feces were examined. More than 70% of hamsters orally infected with C. difficile died without exhibiting diarrhea regardless of toxigenicity of strain. The rats receiving egg white after MNZ administration developed diarrhea due to overgrowth of endogenous C. difficile. This CDI model is non-lethal and diarrheal, and some rats in this model were spontaneously cured. The incidence of diarrhea was significantly decreased in C. butyricum treated rats. These results indicate that the CDI model using egg white and MNZ has potentially better similarity to human CDI, and implies that treatment with C. butyricum may reduce the risk of CDI.

A Review of Experimental and Off-Label Therapies for Clostridium difficile Infection

In spite of increased awareness and the efforts taken to optimize Clostridium difficile infection (CDI) management, with the limited number of currently available antibiotics for C. difficile the halt of this increasing epidemic remains out of reach. There are, however, close to 80 alternative treatment methods with controversial anti-clostridial efficacy or in experimental phase today. Indeed, some of these therapies are expected to become acknowledged members of the recommended anti-CDI arsenal within the next few years. None of these alternative treatment methods can respond in itself to all the major challenges of CDI management, which are primary prophylaxis in the susceptible population, clinical cure of severe cases, prevention of recurrences, and forestallment of asymptomatic C. difficile carriage and in-hospital spread. Yet, the greater the variety of treatment choices on hand, the better combination strategies can be developed to reach these goals in the future. The aim of this article is to provide a comprehensive summary of these experimental and currently off-label therapeutic options.

Leaping Forward in the Treatment of Clostridium Difficile Infection: Update in 2015

In recent years, significant advances in the treatment of Clostridium difficile infection (CDI) have risen. We review the most relevant updated recommendations in the current standard of care of CDI and discuss emerging therapies, including antibiotic, alternative therapies (probiotics, toxin-binding resins, immunotherapy) and new data on fecal transplantation. Upcoming surgical options and other rescue therapies for severe refractory disease are also addressed.

Although oral metronidazole is a first-line therapy for non-severe CDI, emerging data have demonstrated its inferiority relatively to vancomycin, particularly in the setting of recurrent and/or severe infection. After a CDI recurrence for the first time, fidaxomicin has been shown to be associated with lower likelihood of CDI recurrence compared to vancomycin. Fecal transplantation is now strongly recommended for multiple recurrent CDI and may have a role in refractory disease. Oral, frozen stool capsules may simplify fecal transplantation in the future, with preliminary promising results. Diverting loop ileostomy combined with colonic lavage is a potential alternative to colectomy in severe complicated CDI. Potential alternative therapies requiring further investigation include toxin-binding resins and immunotherapy.

Gastrointestinal localization of metronidazole by a lactobacilli-inspired tetramic acid motif improves treatment outcomes in the hamster model of Clostridium difficile infection

OBJECTIVES

Metronidazole, a mainstay treatment for Clostridium difficile infection (CDI), is often ineffective for severe CDI. Whilst this is thought to arise from suboptimal levels of metronidazole in the colon due to rapid absorption, empirical validation is lacking. In contrast, reutericyclin, an antibacterial tetramic acid from Lactobacillus reuteri, concentrates in the gastrointestinal tract. In this study, we modified metronidazole with reutericyclin's tetramic acid motif to obtain non-absorbed compounds, enabling assessment of the impact of pharmacokinetics on treatment outcomes.

METHODS

A series of metronidazole-bearing tetramic acid substituents were synthesized and evaluated in terms of anti-C. difficile activities, gastric permeability, in vivo pharmacokinetics, efficacy in the hamster model of CDI and mode of action.

RESULTS

Most compounds were absorbed less than metronidazole in cell-based Caco-2 permeability assays. In hamsters, lead compounds compartmentalized in the colon rather than the bloodstream with negligible levels detected in the blood, in direct contrast with metronidazole, which was rapidly absorbed into the blood and was undetectable in caecum. Accordingly, four leads were more efficacious (P < 0.05) than metronidazole in C. difficile-infected animals. Improved efficacy was not due to an alternative mode of action, as the leads retained the mode of action of metronidazole.

CONCLUSIONS

This study provides the clearest empirical evidence that the high absorption of metronidazole lowers treatment outcomes for CDI and suggests a role for the tetramic acid motif for colon-specific drug delivery. This approach also has the potential to lower systemic toxicity and drug interactions of nitroheterocyclic drugs for treating gastrointestine-specific diseases.

Clostridium difficile drug pipeline: challenges in discovery and development of new agents

In the past decade Clostridium difficile has become a bacterial pathogen of global significance. Epidemic strains have spread throughout hospitals, while community acquired infections and other sources ensure a constant inoculation of spores into hospitals. In response to the increasing medical burden, a new C. difficile antibiotic, fidaxomicin, was approved in 2011 for the treatment of C. difficile-associated diarrhea. Rudimentary fecal transplants are also being trialed as effective treatments. Despite these advances, therapies that are more effective against C. difficile spores and less damaging to the resident gastrointestinal microbiome and that reduce recurrent disease are still desperately needed. However, bringing a new treatment for C. difficile infection to market involves particular challenges. This review covers the current drug discovery pipeline, including both small molecule and biologic therapies, and highlights the challenges associated with in vitro and in vivo models of C. difficile infection for drug screening and lead optimization.

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.

Clostridium difficile infection: molecular pathogenesis and novel therapeutics

The Gram-positive anaerobic bacterium Clostridium difficile produces toxins A and B, which can cause a spectrum of diseases from pseudomembranous colitis to C. difficile-associated diarrhea. A limited number of C. difficile strains also produce a binary toxin that exhibits ADP ribosyltransferase activity. Here, the structure and the mechanism of action of these toxins as well as their role in disease are reviewed. Nosocomial C. difficile infection is often contracted in hospital when patients treated with antibiotics suffer a disturbance in normal gut microflora. C. difficile spores can persist on dry, inanimate surface for months. Metronidazole and oral vancomycin are clinically used for treatment of C. difficile infection but clinical failure and concern about promotion of resistance are motivating the search for novel non-antibiotic therapeutics. Methods for controlling both toxins and spores, replacing gut microflora by probiotics or fecal transplant, and killing bacteria in the anaerobic gut by photodynamic therapy are discussed.

The roles of host and pathogen factors and the innate immune response in the pathogenesis of Clostridium difficile infection

Clostridium difficile (C. difficile) is the most common cause of nosocomial antibiotic-associated diarrhea and the etiologic agent of pseudomembranous colitis. The clinical manifestation of C. difficile infection (CDI) is highly variable, from asymptomatic carriage, to mild self-limiting diarrhea, to the more severe pseudomembranous colitis. Furthermore, in extreme cases, colonic inflammation and tissue damage can lead to toxic megacolon, a condition requiring surgical intervention. C. difficile expresses two key virulence factors; the exotoxins, toxin A (TcdA) and toxin B (TcdB), which are glucosyltransferases that target host-cell monomeric GTPases. In addition, some hypervirulent strains produce a third toxin, binary toxin or C. difficile transferase (CDT), which may contribute to the pathogenesis of CDI. More recently, other factors such as surface layer proteins (SLPs) and flagellin have also been linked to the inflammatory responses observed in CDI. Although the adaptive immune response can influence the severity of CDI, the innate immune responses to C. difficile and its toxins play crucial roles in CDI onset, progression, and overall prognosis. Despite this, the innate immune responses in CDI have drawn relatively little attention from clinical researchers. Targeting these responses may prove useful clinically as adjuvant therapies, especially in refractory and/or recurrent CDI. This review will focus on recent advances in our understanding of how C. difficile and its toxins modulate innate immune responses that contribute to CDI pathogenesis.

Clinical update for the diagnosis and treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) presents a rapidly evolving challenge in the battle against hospital-acquired infections. Recent advances in CDI diagnosis and management include rapid changes in diagnostic approach with the introduction of newer tests, such as detection of glutamate dehydrogenase in stool and polymerase chain reaction to detect the gene for toxin production, which will soon revolutionize the diagnostic approach to CDI. New medications and multiple medical society guidelines have introduced changing concepts in the definitions of severity of CDI and the choice of therapeutic agents, while rapid expansion of data on the efficacy of fecal microbiota transplantation heralds a revolutionary change in the management of patients suffering multiple relapses of CDI. Through a comprehensive review of current medical literature, this article aims to offer an intensive review of the current state of CDI diagnosis, discuss the strengths and limitations of available laboratory tests, compare both current and future treatments options and offer recommendations for best practice strategies.

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.

The membrane as a target for controlling hypervirulent Clostridium difficile infections

OBJECTIVES

The stationary phase of Clostridium difficile, which is primarily responsible for diarrhoeal symptoms, is refractory to antibiotic killing. We investigated whether disrupting the functions of the clostridial membrane is an approach to control C. difficile infections by promptly removing growing and non-growing cells.

METHODS

The bactericidal activities of various membrane-active agents were determined against C. difficile logarithmic-phase and stationary-phase cultures and compared with known antibiotics. Their effects on the synthesis of ATP, toxins A/B and sporulation were also determined. The effect of rodent caecal contents on anti-difficile activities was examined using two reutericyclin lead compounds, clofazimine, daptomycin and other comparator antibiotics.

RESULTS

Most membrane-active agents and partially daptomycin showed concentration-dependent killing of both logarithmic-phase and stationary-phase cultures. The exposure of cells to compounds at their MBC resulted in a rapid loss of viability with concomitant reductions in cellular ATP, toxins A/B and spore numbers. With the exception of nisin, these effects were not due to membrane pore formation. Interestingly, the activity of the proton ionophore nigericin significantly increased as the growth of C. difficile decreased, suggesting the importance of the proton gradient to the survival of non-growing cells. The activities of the lipophilic antimicrobials reutericyclins and clofazimine were reduced by caecal contents.

CONCLUSIONS

These findings indicate that C. difficile is uniquely susceptible to killing by molecules affecting its membrane function and bioenergetics, indicating that the clostridial membrane is a novel antimicrobial target for agents to alleviate the burden of C. difficile infections.

MBX-500, a hybrid antibiotic with in vitro and in vivo efficacy against toxigenic Clostridium difficile

Clostridium difficile infection (CDI) causes moderate to severe disease, resulting in diarrhea and pseudomembranous colitis. CDI is difficult to treat due to production of inflammation-inducing toxins, resistance development, and high probability of recurrence. Only two antibiotics are approved for the treatment of CDI, and the pipeline for therapeutic agents contains few new drugs. MBX-500 is a hybrid antibacterial, composed of an anilinouracil DNA polymerase inhibitor linked to a fluoroquinolone DNA gyrase/topoisomerase inhibitor, with potential as a new therapeutic for CDI treatment. Since MBX-500 inhibits three bacterial targets, it has been previously shown to be minimally susceptible to resistance development. In the present study, the in vitro and in vivo efficacies of MBX-500 were explored against the Gram-positive anaerobe, C. difficile. MBX-500 displayed potency across nearly 50 isolates, including those of the fluoroquinolone-resistant, toxin-overproducing NAP1/027 ribotype, performing as well as comparator antibiotics vancomycin and metronidazole. Furthermore, MBX-500 was a narrow-spectrum agent, displaying poor activity against many other gut anaerobes. MBX-500 was active in acute and recurrent infections in a toxigenic hamster model of CDI, exhibiting full protection against acute infections and prevention of recurrence in 70% of the animals. Hamsters treated with MBX-500 displayed significantly greater weight gain than did those treated with vancomycin. Finally, MBX-500 was efficacious in a murine model of CDI, again demonstrating a fully protective effect and permitting near-normal weight gain in the treated animals. These selective anti-CDI features support the further development of MBX 500 for the treatment of CDI.

Novel management strategies in the treatment of severe Clostridium difficile infection

CDI is increasing in incidence and severity. Clinicians must have a low threshold to consider the diagnosis and to treat patients with the clinical syndrome and risk factors before laboratory confirmation of the diagnosis. In patients who have signs of advanced disease, escalation of care with antimicrobial strategies and multidisciplinary care including surgical consultation is necessary. Furthermore, lowering the threshold for surgery compared with traditional approaches likely results in improved survival. Novel surgical approaches may obviate total abdominal colectomy and the associated immediate and long-term morbidity in this often fragile patient population, thus allowing clinicians to embrace surgical therapy earlier in the course of severe, complicated disease.

In vitro and in vivo activities of the novel Ketolide RBx 14255 against Clostridium difficile

The MIC(90) of RBx 14255, a novel ketolide, against Clostridium difficile was 4 μg/ml (MIC range, 0.125 to 8 μg/ml), and this drug was found to be more potent than comparator drugs. An in vitro time-kill kinetics study of RBx 14255 showed time-dependent bacterial killing for C. difficile. Furthermore, in the hamster model of C. difficile infection, RBx 14255 demonstrated greater efficacy than metronidazole and vancomycin, making it a promising candidate for C. difficile treatment.

Efficacy of LFF571 in a hamster model of Clostridium difficile infection

LFF571 is a novel semisynthetic thiopeptide antibiotic with potent activity against a variety of Gram-positive pathogens, including Clostridium difficile. In vivo efficacy of LFF571 was compared to vancomycin in a hamster model of C. difficile infection (CDI). Infection was induced in Golden Syrian hamsters using a toxigenic strain of C. difficile. Treatment started 24 h postinfection and consisted of saline, vancomycin, or LFF571. Cox regression was used to analyze survival data from a cohort of animals evaluated across seven serial experimental groups treated with vancomycin at 20 mg/kg, LFF571 at 5 mg/kg, or vehicle alone. Survival was right censored; animals were not observed beyond day 21. At death or end of study, cecal contents were tested for C. difficile toxins A and B. In summary, the data showed that 5 mg/kg LFF571 decreased the risk of death by 79% (P < 0.0001) and 69% (P = 0.0022) compared with saline and 20 mg/kg vancomycin, respectively. Further analysis of the pooled data indicated that the survival benefit of LFF571 treatment at 5 mg/kg compared to vancomycin at 20 mg/kg was due primarily to a decrease in the risk of recurrence after end of treatment. Animals successfully treated with LFF571 or vancomycin had no detectable C. difficile toxin. Overall, LFF571 was more efficacious at the end of the study, at a lower dose, and with fewer recurrences, than vancomycin in the hamster model of CDI. LFF571 is being assessed in humans for safety and efficacy in the treatment of C. difficile infections.

Discovery of LFF571: an investigational agent for Clostridium difficile infection

Clostridium difficile (C. difficile) is a Gram positive, anaerobic bacterium that infects the lumen of the large intestine and produces toxins. This results in a range of syndromes from mild diarrhea to severe toxic megacolon and death. Alarmingly, the prevalence and severity of C. difficile infection are increasing; thus, associated morbidity and mortality rates are rising. 4-Aminothiazolyl analogues of the antibiotic natural product GE2270 A (1) were designed, synthesized, and optimized for the treatment of C. difficile infection. The medicinal chemistry effort focused on enhancing aqueous solubility relative to that of the natural product and previous development candidates (2, 3) and improving antibacterial activity. Structure-activity relationships, cocrystallographic interactions, pharmacokinetics, and efficacy in animal models of infection were characterized. These studies identified a series of dicarboxylic acid derivatives, which enhanced solubility/efficacy profile by several orders of magnitude compared to previously studied compounds and led to the selection of LFF571 (4) as an investigational new drug for treating C. difficile infection.

Models for the study of Clostridium difficile infection

Models of Clostridium difficile infection (C. difficile) have been used extensively for Clostridium difficile (C. difficile) research. The hamster model of C. difficile infection has been most extensively employed for the study of C. difficile and this has been used in many different areas of research, including the induction of C. difficile, the testing of new treatments, population dynamics and characterization of virulence. Investigations using in vitro models for C. difficile introduced the concept of colonization resistance, evaluated the role of antibiotics in C. difficile development, explored population dynamics and have been useful in the evaluation of C. difficile treatments. Experiments using models have major advantages over clinical studies and have been indispensible in furthering C. difficile research. It is important for future study programs to carefully consider the approach to use and therefore be better placed to inform the design and interpretation of clinical studies.

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

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

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

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

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.

Future novel therapeutic agents for Clostridium difficile infection

IMPORTANCE OF THE FIELD

Clostridium difficile is the most important definable cause of healthcare acquired diarrhea. The increasing incidence and mortality associated with this enteric pathogen and the significant rate of treatment failures and recurrences with current antibiotics emphasize the need for the discovery of new and improved therapeutic and preventative agents.

WHAT THE READER WILL GAIN

We review upcoming novel therapeutic agents and the clinical evidence to support their efficacy in treating C. difficile infection. We also provide an extensive comparison of antimicrobial susceptibilities of C. difficile based on in vitro susceptibilities published in the literature.

AREAS COVERED IN THIS REVIEW

This review was conducted by a thorough examination of the public sources, including journals and scientific meeting abstracts, up to February 2009.

TAKE HOME MESSAGE

A number of new therapeutic agents are in development and being tested in clinical trials. However, high costs and concerns for resistance may limit the use of these antimicrobials for the treatment of C. difficile infection. Passive and active immunotherapy may have important future roles as therapeutic and preventative strategies for C. difficile infection.

Clostridium difficile infection: update on emerging antibiotic treatment options and antibiotic resistance

Clostridium difficile infection (CDI) is the most common cause of identifiable diarrhea in hospitalized patients. The incidence and severity of CDIs are increasing. The increased incidence and severity of the disease has sparked interest in the optimal treatment of CDI as well as the use of new therapies and drug discovery. Current treatment strategies are inadequate with decreased response rates to metronidazole, and high recurrence rates with the use of metronidazole and oral vancomycin. Although incidence rates continue to be low, in vitro resistance to antibiotics used for the treatment of CDI has been noted. Recently, important data has emerged on new anti-C. difficile antibiotics such as rifaximin, rifalazil, fidaxomicin, nitazoxanide, tigecycline and ramoplanin. The purpose of this review is to provide an update on the in vitro susceptibility and new antibiotic treatment options for CDI. This review will focus primarily on scientific studies published in the last 36 months in order to provide an up-to-date review on the topic.

The enterotoxicity of Clostridium difficile toxins

The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.

Clostridium difficile colitis

Clostridium difficile is the most common cause of infectious diarrhea in hospitalized patients. Its effects are mediated by C difficile toxins A and B. Recent outbreaks of severe colitis have been associated with a new strain of the bacterium that produces large amounts of the toxins. Although oral metronidazole and oral vancomycin can be used to treat C difficile-associated disease, intraluminal vancomycin is preferable for more severe C difficile colitis. Early surgical intervention can improve outcomes with fulminant colitis, although overall mortality remains high.

Inhibitory effect of REP3123 on toxin and spore formation in Clostridium difficile, and in vivo efficacy in a hamster gastrointestinal infection model

OBJECTIVES

REP3123 is a fully synthetic methionyl-tRNA synthetase inhibitor in pre-clinical development as a novel agent to treat Clostridium difficile infection (CDI). This novel agent was investigated for its ability to block the production of toxins and spores, and was tested for efficacy in vivo in a hamster model.

METHODS

Clostridial toxin levels were determined qualitatively using monoclonal antibodies and by cytotoxicity assays. Spores were detected by staining and by quantitative dilution plating after ethanol treatment. Efficacy of REP3123 was tested in a clindamycin-induced C. difficile hamster gastrointestinal (GI) infection model.

RESULTS

REP3123 at concentrations as low as 1 mg/L inhibited de novo toxin production in high cell density, stationary phase cultures of C. difficile. Among comparator agents currently used for CDI therapy, vancomycin required much higher levels of 20 mg/L, and metronidazole had no effect on toxin levels. REP3123 caused a >10-fold reduction of the sporulation rate in vitro. Vancomycin and, in particular, metronidazole appeared to promote the formation of spores. REP3123, at concentrations as low as 0.5 mg/kg, demonstrated efficacy in the hamster model of CDI and was superior to vancomycin in the overall survival of the animals at the end of the study (33 days).

CONCLUSIONS

REP3123 inhibited growth of C. difficile, affected the production of toxins and spores and demonstrated superior efficacy compared with vancomycin in the hamster GI infection model. This agent may be a promising candidate for CDI treatment; in particular, the inhibition of toxin production and spore formation may reduce the severity and spread of the disease, respectively.

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.

Clostridial typhlitis associated with topical antibiotic therapy in a Syrian hamster

A Syrian hamster that had been treated with topical antibiotic ointment for 10 days following injuries sustained during fighting was presented moribund. Postmortem and microscopic examinations revealed lesions consistent with clostridial typhlitis and enteritis. Anaerobic culture of caecal contents resulted in the isolation of two Clostridium species, and caecal contents contained Clostridium difficile enterotoxins. Based on these findings, a diagnosis of acute C. difficile enterotoxaemia was made. This report discusses the pathogenesis of C. difficile enterotoxaemia and the potential role of topical antibiotic ointment therapy in initiating the disease.

A mouse model of Clostridium difficile-associated disease

BACKGROUND & AIMS

Infection with Clostridium difficile causes nosocomial antibiotic-associated diarrhea and colitis. Hamsters historically have been used to investigate disease pathogenesis and treatment, but are not ideal models because of the lack of hamster-specific reagents and genetically modified animals, and because they develop fulminant disease. The aim of this study was to establish a mouse model of antibiotic-induced C. difficile-associated disease (CDAD) that more closely resembles human disease.

METHODS

C57BL/6 mice were exposed to a mixture of antibiotics (kanamycin, gentamicin, colistin, metronidazole, and vancomycin) for 3 days. Two days later, they were given injections of clindamycin and then challenged 1 day later with different doses of C. difficile.

RESULTS

Mice that were exposed to antibiotics and then challenged with C. difficile developed diarrhea and lost weight. Disease severity varied from fulminant to minimal in accordance with the challenge dose. Typical histologic features of CDAD were evident. Oral vancomycin prevented CDAD in all mice, but 68% died from colitis after treatment was discontinued. All animals that survived an initial episode of CDAD showed no evidence of diarrhea or colitis after subsequent rechallenge with C. difficile. Different strains of C. difficile tested in the model showed different levels of virulence in mice.

CONCLUSIONS

We have developed a mouse model of CDAD that closely represents the human disease. In light of the recent substantial increases in CDAD incidence and severity, this model will be valuable in testing new treatments, examining disease pathogenesis, and elucidating mechanisms of protective immunity.

Rifamycin antibiotics for treatment of Clostridium difficile-associated diarrhea

OBJECTIVE

To review the existing data on use of the rifamycin class of antibiotics as therapy for Clostridium difficile-associated diarrhea (CDAD).

DATA SOURCES

A literature search was performed using PubMed (1996-January 2008), abstracts from the International Conference on Antimicrobial Agents and Chemotherapy (September 2007), the Infectious Diseases Society of America (October 2007), Salix Pharmaceuticals Web site (January 2008), ActivBiotics Web site (January 2008), Google Scholar, and searches of selected bibliographies using the terms rifamycin, ansamycins, rifampin, rifabutin, rifampicin, rifaximin, rifalazil, Clostridium difficile, C. difficile, and CDAD.

STUDY SELECTION AND DATA EXTRACTION

In vivo and in vitro studies investigating the use of rifamycins for CDAD were selected, along with all clinical trials using rifamycins in patients with CDAD.

DATA SYNTHESIS

Nine studies totaling 890 isolates were identified that investigated the in vitro susceptibility of rifampin (6 studies), rifaximin (3 studies), and rifalazil (2 studies). Rifamycins consistently displayed potent activity against tested strains, although strains with decreased susceptibility have been identified. Six published clinical studies involving 81 patients have investigated the use of rifamycins for the treatment of CDAD. These have generally been small studies, although initial positive clinical results have been reported on the use of rifamycins for recurrent CDAD.

CONCLUSIONS

Preliminary data support the use of rifamycins for treatment of CDAD. With the increased incidence and severity of CDAD, further investigation into this drug class as a treatment regimen for CDAD is warranted.

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.

Comparative efficacies of rifaximin and vancomycin for treatment of Clostridium difficile-associated diarrhea and prevention of disease recurrence in hamsters

Clostridium difficile-associated colitis is an increasing cause of morbidity and mortality in hospitalized patients, with high relapse rates following conventional therapy. We sought to determine the efficacy of rifaximin, a novel nonabsorbed antibiotic, in the hamster model of C. difficile-associated diarrhea (CDAD). Hamsters received clindamycin subcutaneously and 24 h later were infected by gavage with one of two C. difficile strains: a reference strain (VPI 10463) and a current epidemic strain (BI17). Vancomycin (50 mg/kg of body weight) or rifaximin (100, 50, and 25 mg/kg) were then administered orally for 5 days beginning either on the same day as infection (prevention) or 24 h later (treatment). Therapeutic effects were assessed by weight gain, histology, and survival. We found that rifaximin was as effective as vancomycin in the prevention and treatment of colitis associated with the two C. difficile strains that we examined. There was no relapse after treatment with vancomycin or rifaximin in hamsters infected with the BI17 strain. Hamsters infected with the VPI 10463 strain and treated with rifaximin did not develop relapsing infection within a month of follow-up, whereas the majority of vancomycin-treated animals relapsed (0% versus 75%, respectively; P < 0.01). In conclusion, rifaximin was found to be an effective prophylactic and therapeutic agent for CDAD in hamsters and was not associated with disease recurrence. These findings, in conjunction with the pharmacokinetic and safety profiles of rifaximin, suggest that it is an attractive candidate for clinical use for CDAD.

In vitro activities of 15 antimicrobial agents against 110 toxigenic clostridium difficile clinical isolates collected from 1983 to 2004

The incidence and severity of Clostridium difficile-associated disease (CDAD) is increasing, and standard treatment is not always effective. Therefore, more-effective antimicrobial agents and treatment strategies are needed. We used the agar dilution method to determine the in vitro susceptibility of the following antimicrobials against 110 toxigenic clinical isolates of C. difficile from 1983 to 2004, primarily from the United States: doripenem, meropenem, gatifloxacin, levofloxacin, moxifloxacin, OPT-80, ramoplanin, rifalazil, rifaximin, nitazoxanide, tizoxanide, tigecycline, vancomycin, tinidazole, and metronidazole. Included among the isolates tested were six strains of the toxinotype III, NAP1/BI/027 group implicated in recent U.S., Canadian, and European outbreaks. The most active agents in vitro were rifaximin, rifalazil, tizoxanide, nitazoxanide, and OPT-80 with MICs at which 50% of the isolates are inhibited (MIC(50)) and MIC(90) values of 0.0075 and 0.015 microg/ml, 0.0075 and 0.03 microg/ml, 0.06 and 0.125 microg/ml, 0.06 and 0.125 microg/ml, 0.125 and 0.125 microg/ml, respectively. However, for three isolates the rifalazil and rifaximin MICs were very high (MIC of >256 microg/ml). Ramoplanin, vancomycin, doripenem, and meropenem were also very active in vitro with narrow MIC(50) and MIC(90) ranges. None of the isolates were resistant to metronidazole, the only agent for which there are breakpoints, with tinidazole showing nearly identical results. These in vitro susceptibility results are encouraging and support continued evaluation of selected antimicrobials in clinical trials of treatment for CDAD.

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.

Effects of huoxiangzhengqi liquid on enteric mucosal immune responses in mice with Bacillus dysenteriae and Salmonella typhimurium induced diarrhea

AIM: To explore effects of huoxiangzhengqi liquid (HXZQ) on enteric mucosal immune responses in mice with Bacillus dysenteriae and Salmonella typhimurium induced diarrhea (BSD).

METHODS: BSD was induced in Balb/c mice by oral administration with Bacillus dysenteriae and Salmonella typhimurium. HXZQ was administrated from the day of diarrhea induction at dosages of 5.21 g/kg and 0.52 g/kg, respectively. The onset of diarrhea and lasting time were recorded. Peyer’s patches and peripheral lymphocytes were prepared for flow cytometry, and levels of TNF-α in peripheral blood and enteric tissue homogenates were determined with ELISA. Student’s t test was employed for statistics.

RESULTS: Mice in BSD group started showing continuous diarrhea on the day of induction until the fourth day when they were sacrificed. Diarrhea in the mice of HXZQ high and low dose groups lasted for 36 and 54 h, respectively. There were more CD4⁺ and CD8⁺ cells in peripheral blood, fewer CD4⁺ cells in Peyer’s patches in BSD mice compared to normal mice. Fewer CD4⁺ and CD8⁺ cells was shown in the mice in HXZQ high group compared to BSD mice. In Peyer’s patch, there were more CD8⁺ cells in mice in HXZQ high and low dose groups and more CD4⁺ in mice in HXZQ high group. Higher levels of TNF-α in peripheral blood and intestinal tissue homogenates in BSD group were observed. Mice in HXZQ high group showed decreased levels of TNF-α in peripheral blood and enteric tissue homogenates.

CONCLUSION: The immune regulation of CD4⁺ and CD8⁺ cells in Peyer’s patch and suppression of TNF-α levels in enteric homogenates may partially explain the effect of HXZQ on improvement of BSD.

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.

Efficacy of novel rifamycin derivatives against rifamycin-sensitive and -resistant Staphylococcus aureus isolates in murine models of infection

Novel rifamycins (new chemical entities [NCEs]) having MICs of 0.002 to 0.03 microg/ml against Staphylococcus aureus and retaining some activity against rifampin-resistant mutants were tested for in vivo efficacy against susceptible and rifampin-resistant strains of S. aureus. Rifalazil and rifampin had a 50% effective dose (ED50) of 0.06 mg/kg of body weight when administered as a single intravenous (i.v.) dose in a murine septicemia model against a susceptible strain of S. aureus. The majority of NCEs showed efficacy at a lower i.v. dose (0.003 to 0.06 mg/kg). In addition, half of the NCEs tested for oral efficacy had ED50s in the range of 0.015 to 0.13 mg/kg, i.e., lower or equivalent to the oral ED50s of rifampin and rifalazil. NCEs were also tested in the septicemia model against a rifampin-resistant strain of S. aureus. Twenty-four of 169 NCEs were efficacious when administered as a single oral dose of 80 mg/kg. These NCEs were examined in the murine thigh infection model against a susceptible strain of S. aureus. Several NCEs dosed by intraperitoneal injection at 0.06 mg/kg caused a significant difference in bacterial titer compared with placebo-treated animals. No NCEs showed efficacy in the thigh model against a highly rifampin-resistant strain. However, several NCEs showed an effect when tested against a partially rifampin-resistant strain. The NCEs having a 25-hydroxyl moiety were more effective as a group than their 25-O-acetyl counterparts. These model systems defined candidate NCEs as components of potential combination therapies to treat systemic infections or as monotherapeutic agents for topical applications.

Development potential of rifalazil and other benzoxazinorifamycins

Rifalazil and other benzoxazinorifamycins (new chemical entities [NCEs]) are rifamycins that contain a distinct planar benzoxazine ring. Rifalazil has excellent antibacterial activity, high intracellular levels and high tissue penetration, which are attributes that favour its use in treating diseases caused by the obligate intracellular pathogens of the genus Chlamydia. Recent studies have shown that rifalazil has efficacy in the treatment of human sexually transmitted disease caused by Chlamydia trachomatis. The extraordinary potency of rifalazil and other NCEs, such as ABI-0043, extends to the related microorganism, C. pneumoniae, a respiratory pathogen that can disseminate and persist chronically in the vasculature, resulting in increased plaque formation in animal studies. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. Other opportunities include gastric ulcer disease caused by Helicobacter pylori and antibiotic-associated colitis caused by infection with Clostridium difficile in the colon. The NCEs could prove to be valuable as follow-on compounds in these indications, as rifampin replacements in antibacterial combination therapy or as stand-alone topical antibacterials (e.g., to treat acne). Neither rifalazil nor NCEs appear to induce the cytochrome P450 3A4, an attribute of rifampin that can result in adverse events due to drug-drug interactions.

Natural products to drugs: natural product derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or in registration (current 31 December 2004) have been reviewed. Natural product derived drugs launched in the United States of America, Europe and Japan since 1998 and new natural product templates discovered since 1990 are discussed.