In vitro and in vivo activities of nitazoxanide against Clostridium difficile

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.

Thiazolides: a new class of drugs for the treatment of chronic hepatitis B and C

Nitazoxanide, the first thiazolide, was originally developed for the treatment of Cryptosporidium parvum. The antiviral activity of nitazoxanide was discovered by serendipity in patients with AIDS who were treated for cryptosporidial diarrhea and had HBV or HCV co-infection. In preliminary open-label studies of patients with chronic hepatitis B, nitazoxanide suppressed serum HBV DNA and led to loss or seroconversion of hepatitis B e antigen in the majority of patients, as well as hepatitis B surface antigen in approximately a quarter of patients. In Phase II studies of patients with chronic hepatitis C genotype 4, nitazoxanide combined with peginterferon alfa-2a, with or without ribavirin, increased the sustained virologic response rate to 79-80 versus 50% with peginterferon plus ribavirin standard of care. Randomized, controlled studies of naive and nonresponder patients with chronic hepatitis C genotype 1 and patients with chronic hepatitis B are underway, and new second generation thiazolides are being developed.

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.

Nitazoxanide: clinical studies of a broad-spectrum anti-infective agent

Nitazoxanide is a new compound with broad-spectrum activity against numerous intestinal protozoa, helminths and anaerobic bacteria. It is approved for the treatment of diseases caused by Giardia intestinalis and Cryptosporidium species. The drug is well tolerated, with few side effects and requires a short course of treatment. Further investigations regarding its use in patients with AIDS is needed. Nitazoxanide represents a significant advance in the treatment of intestinal parasitic infections worldwide.

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.

Nitazoxanide: a review of its use in the treatment of gastrointestinal infections

Nitazoxanide (Alinia, Daxon, Dexidex, Paramix, Kidonax, Colufase, Annita) has in vitro activity against a variety of microorganisms, including a broad range of protozoa and helminths. Nitazoxanide is effective in the treatment of protozoal and helminthic infections, including Cryptosporidium parvum or Giardia lamblia, in immunocompetent adults and children, and is generally well tolerated. Nitazoxanide is a first-line choice for the treatment of illness caused by C. parvum or G. lamblia infection in immunocompetent adults and children, and is an option to be considered in the treatment of illnesses caused by other protozoa and/or helminths.

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.

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.

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.

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.

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.

Nitazoxanide, a broad-spectrum thiazolide anti-infective agent for the treatment of gastrointestinal infections

Colonisation of the gastrointestinal tract by anaerobic bacteria, protozoa, trematodes, cestodes and/or nematodes and other infectious pathogens, including viruses, represents a major cause of morbidity and mortality in Africa, South America and southeast Asia, as well as other parts of the world. Nitazoxanide is a member of the thiazolide class of drugs with a documented broad spectrum of activity against parasites and anaerobic bacteria. Moreover, the drug has recently been reported to have a profound activity against hepatitis C virus infection. In addition, nitazoxanide exhibits anti-inflammatory properties, which have prompted clinical investigations for its use in Crohn's disease. Studies with nitazoxanide derivatives have determined that there must be significantly different mechanisms of action acting on intracellular versus extracellular pathogens. An impressive number of clinical studies have shown that the drug has an excellent bioavailability in the gastrointestinal tract, is fast acting and highly effective against gastrointestinal bacteria, protozoa and helminthes. A recent Phase II study has demonstrated viral response (hepatitis C) to monotherapy, with a low toxicity and an excellent safety profile over 24 weeks of treatment. Pre-clinical studies have indicated that there is a potential for application of this drug against other diseases, not primarily affecting the liver or the gastrointestinal tract.

An update on diagnosis, treatment, and prevention of Clostridium difficile-associated disease

Clostridium difficile is an important cause of nosocomial morbidity and mortality and is implicated in recent epidemics. Data support the treatment of colitis with oral metronidazole in a dose of 1.0 to 1.5 g/d, with oral vancomycin as a second-line agent, not because its efficacy is questioned but because of environmental concerns. Nitazoxanide and other drugs are currently under intense study as alternatives. Treatment of asymptomatic patients is not recommended. Current management strategies appear to be increasingly ineffective, especially for patients who experience multiple recurrences. Biotherapy and vaccination are currently being explored as treatment options for patients who have recurrent disease. Greater attention should be paid to hospital infection control policies and restriction of broad-spectrum antibiotics.

Use of nitazoxanide for gastrointestinal tract infections: Treatment of protozoan parasitic infection and beyond

The United States Food and Drug Administration has approved the parasiticidal agent nitazoxanide for treatment of diarrhea caused by Giardia lamblia/intestinalis or Cryptosporidium parvum. This novel agent has a broad spectrum of activity against many other gastrointestinal pathogens, including bacteria, roundworms, flatworms, and flukes. Nitazoxanide is used in many areas of the world, especially in Central and South America, as a broad-spectrum parasiticidal agent in adults and children. Nitazoxanide appears to be well tolerated, has a relatively low incidence of adverse effect, and displays no significant known drug-to-drug interactions. Recently, preliminary reports indicate that nitazoxanide may be an effective treatment for Clostridium difficile-associated diarrhea as well. Future work will likely solidify and further expand the role of nitazoxanide in the treatment of a wide range of intestinal pathogens.

Treatment of Clostridium difficile-associated disease: old therapies and new strategies

Clostridium difficile-associated disease (CDAD) causes substantial morbidity and mortality. The pathogenesis is multifactorial, involving altered bowel flora, production of toxins, and impaired host immunity, often in a nosocomial setting. Current guidelines recommend treatment with metronidazole; vancomycin is a second-line agent because of its potential effect on the hospital environment. We present the data that led to these recommendations and explore other therapeutic options, including antimicrobials, antibody to toxin A, probiotics, and vaccines. Treatment of CDAD has increasingly been associated with failure and recurrence. Recurrent disease may reflect relapse of infection due to the original infecting organism or infection by a new strain. Poor antibody responses to C difficile toxins have a permissive role in recurrent infection. Hospital infection control and pertinent use of antibiotics can limit the spread of CDAD. A vaccine directed against C difficile toxin may eventually offer a solution to the CDAD problem.

What's new in enteric infectious diseases at home and abroad

PURPOSE OF REVIEW

This review was designed to focus on the important research in the area of acute infectious diarrhea published within the past year. PubMed was reviewed for articles published in 2004 and 2005 relating to pathogen-specific diarrhea and for travelers' diarrhea to identify the newly published articles.

RECENT FINDINGS

New studies continue to show the importance of the diarrheagenic Escherichia coli as causes of acute and persistent diarrhea. Enteroaggregative E. coli has recently been shown to be an unrecognized cause of community-acquired diarrhea in infants in the USA. Genetic factors explain an increased susceptibility to travelers' diarrhea among international travelers. Also, poorly non-absorbed rifaximin (< 0.4%) was shown to be an effective drug when used prophylactically to prevent bacterial diarrhea during high risk travel.

SUMMARY

Studies will continue to define the etiology of diarrhea and to better understand the epidemiology and prevention of infectious diarrhea. Antibacterial resistance among enteric bacterial pathogens is a growing problem, leading to the search for newer antibacterial drugs. Diarrhea due to bacterial agents in international travelers can be prevented and treated successfully by antibacterial drugs. The nonabsorbed rifamycin drug, rifaximin, appears to be ideally suited to become the important new drug in prevention and treatment of travelers' diarrhea. Studies are underway to determine the value of the drug in preventing invasive forms of diarrhea during travel to Asia and in the prevention of the commonly occurring post-infectious irritable bowel syndrome.

Use of nitazoxanide as a new therapeutic option for persistent diarrhea: a pediatric perspective

Despite advances in the management of diarrheal disorders, diarrhea is the second most frequent illness in the world. Persistent diarrhea, common in community pediatrics, is often caused by organisms such as Giardia lamblia, Cryptosporidium parvum and, less frequently, Cyclospora, Isospora belli, and Clostridium difficile. Identifying the causative organism is often challenging, and diagnostic tests may be inaccurate and expensive and, thus, of limited benefit. Consequently, carefully chosen empiric therapy guided by a physician's clinical impressions may be a useful and cost-effective option in children with persistent diarrhea, particularly those whose signs and symptoms suggest a protozoal etiology. This article discusses the empiric use of anti-infective nitazoxanide, a thiazolide compound, in three case reports of children with persistent diarrhea, and presents an overview of the diagnostic and therapeutic issues associated with this disorder and the pharmacodynamics and pharmacokinetics of the drug.

Increasing risk of relapse after treatment of Clostridium difficile colitis in Quebec, Canada

BACKGROUND

Clinicians who treat patients with Clostridium difficile-associated diarrhea (CDAD) in Quebec, Canada, have noted an apparent increase in the proportion of patients who experience relapse.

METHODS

To determine whether there was an increase in the frequency of treatment failure and of recurrence of CDAD after treatment, we reviewed data on cases that had been diagnosed in a hospital in the province of Quebec during the period 1991-2004. The frequency of recurrences within 60 days after the initial diagnosis was measured using Kaplan-Meier analysis, and Cox regression was used for multivariate analysis.

RESULTS

Among patients who had initially been treated with metronidazole, the proportion whose regimens were switched to vancomycin or for whom vancomycin was added because of a disappointing response did not vary between 1991 and 2002 (66 [9.6%] of 688 patients overall) but more than doubled in 2003-2004 (112 [25.7%] of 435; P < .001). Among 845 patients treated with metronidazole only, the 60-day probability of recurrence increased dramatically in 2003-2004 (47.2%), compared with 1991-2002 (20.8%; P < .001). During 1991-2002, the probabilities of recurrence were 20.0%, 13.8%, and 28.9% among individuals aged 0-17, 18-64, and > or = 65 years, respectively; during 2003-2004, the probabilities were 25.0%, 27.1%, and 58.4%, respectively.

CONCLUSION

In 2003-2004, there was an increase in the proportion of patients with CDAD believed, by their attending physicians, to have experienced metronidazole treatment failure, as well as an increase in the frequency of post-metronidazole therapy recurrences, especially among elderly persons.

Nitazoxanide: a new thiazolide antiparasitic agent

Nitazoxanide is a new thiazolide antiparasitic agent that shows excellent in vitro activity against a wide variety of protozoa and helminths. It is given by the oral route with good bioavailability and is well tolerated, with primarily mild gastrointestinal side effects. At present, there are no documented drug-drug interactions. Nitazoxanide has been licensed for the treatment of Giardia intestinalis-induced diarrhea in patients >or=1 year of age and Cryptosporidum-induced diarrhea in children aged 1-11 years. At present, it is pending licensure for treatment of infection due to Cryptosporidium species in adults and for use in treating immunocompromised hosts. It represents an important addition to the antiparasitic arsenal.

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

Although vancomycin and metronidazole effectively treat Clostridium difficile-associated diarrhea and colitis (CDAD), their use is associated with a high incidence of relapsing C. difficile infection. Rifalazil is a new benzoxazinorifamycin that possesses activity against Mycobacterium tuberculosis and gram-positive bacteria. Here we compared rifalazil and vancomycin for effectiveness in preventing or treating clindamycin-induced cecitis in a hamster model of CDAD. Golden Syrian hamsters were injected subcutaneously with clindamycin phosphate (10 mg/kg), followed 24 h later by C. difficile gavage. Hamsters received by gavage for 5 days vehicle, vancomycin (50 mg/kg), or rifalazil (20 mg/kg) either simultaneously with (prophylactic protocol) or 24 h after C. difficile administration (treatment protocol). While all vehicle-administered animals became moribund within 48 h of C. difficile administration, no rifalazil- or vancomycin-treated animals in either protocol showed signs of morbidity after 7 days. Ceca of rifalazil-treated animals showed absence of epithelial cell damage, significantly reduced congestion and edema, and less, but not statistically significantly less, neutrophil infiltration compared to those of vehicle-treated animals. In contrast, vancomycin-treated animals demonstrated severe epithelial cell damage and mildly reduced congestion and edema. Moreover, hamsters relapsed and tested C. difficile toxin positive (by enzyme-linked immunosorbent assay) 10 to 15 days after discontinuation of vancomycin treatment. None of the rifalazil-treated hamsters showed signs of disease or presence of toxins in their feces 30 days after discontinuation of treatment. Our results indicate that once daily rifalazil may be superior to vancomycin for curative treatment of CDAD.

Nitazoxanide Treatment for Giardiasis and Cryptosporidiosis in Children

OBJECTIVE

To review the pharmacology, pharmacokinetics, adverse effects, drug interactions, dosing recommendations, and clinical efficacy of nitazoxanide, a new antiprotozoal/anthelmintic/antibacterial agent.

DATA SOURCES

A MEDLINE search (1966-February 2004) of both human and animal research data published in the English language was conducted.

STUDY SELECTION AND DATA EXTRACTION

All primary and review articles pertaining to the MEDLINE search were reviewed for inclusion. Emphasis was placed on randomized, double-blind, placebo-controlled trials.

DATA SYNTHESIS

Nitazoxanide is approved for the treatment of giardiasis and cryptosporidiosis (first drug approved for the latter indication) in immune-competent children <12 years of age. Most studies in immune-competent patients have reported clinical and parasitologic response rates close to 80% and 70%, respectively, for both indications. Response rates have been lower in immune-compromised patients.

CONCLUSIONS

Nitazoxanide should be available for patients unable to tolerate or adhere to first-line therapy employed for these intestinal protozoa. THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT ACPE UNIVERSAL PROGRAM NUMBER: 407-000-04-014-H01

Nitazoxanide in treatment of Helicobacter pylori: a clinical and in vitro study

Nitazoxanide (NTZ) is an antibiotic with microbiological characteristics similar to those of metronidazole but without an apparent problem of resistance. The aim of this study was the prospective evaluation of NTZ given as a single agent in the treatment of Helicobacter pylori infection. Twenty culture-positive patients with dyspepsia who had previously failed at least one course of H. pylori eradication therapy were enrolled. Subjects received 1 g of NTZ twice daily for 10 days. The safety and tolerability of the drug were assessed by physical examination, monitoring of adverse events, and clinical laboratory evaluation. Urea breath tests (UBTs) were performed 6 weeks posttreatment. H. pylori was isolated from UBT-positive patients by the string test or endoscopy with biopsy, and the MICs for these isolates were compared to those for isolates obtained pretherapy. The levels of tizoxanide, the active deacylated derivative of NTZ, were measured in blood, saliva, and tissue from two patients during treatment. The UBT results were positive for all 20 patients after completion of NTZ therapy. The MIC results demonstrated that the NTZ susceptibilities of none of the strains isolated from the patients posttherapy had changed significantly. No major adverse reactions were observed, but frequent minor side effects were observed. In conclusion, NTZ did not eradicate H. pylori when it was given as a single agent.

Prevalence of Clostridium spp. and Clostridium difficile in children with acute diarrhea in São Paulo city, Brazil

Species of Clostridium are widely distributed in the environment, inhabiting both human and animal gastrointestinal tracts. Clostridium difficile is an important pathogen associated with outbreaks of pseudomembranous colitis and other intestinal disorders, such as diarrhea. In this study, the prevalence of Clostridium spp. and C. difficile, from hospitalized children with acute diarrhea, was examined. These children were admitted to 3 different hospitals for over 12 months. Eighteen (20%) and 19 (21%) stool specimens from children with (90) and without (91) diarrhea respectively, were positive to clostridia. Only 10 C. difficile strains were detected in 5.5% of the stool samples of children with diarrhea. None healthy children (without diarrhea) harbored C. difficile. From these 10 C. difficile, 9 were considered as toxigenic and genotyped as tcdA+/tcdB+ or tcdA-/tcdB+, and 1 strain as nontoxigenic (tcdA-/tdcB-). They were detected by the citotoxicity on VERO cells and by the multiplex-polymerase chain reaction. Thirty clinical fecal extracts produced minor alterations on VERO cells. The presence of C. difficile as a probable agent of acute diarrhea is suggested in several countries, but in this study, the presence of these organisms was not significant. More studies will be necessary to evaluate the role of clostridia or C. difficile in diarrhoeal processes in children.

Long-lasting anticryptosporidial activity of nitazoxanide in an immunosuppressed rat model

Cryptosporidium parvum, Tyzzer, 1912 is identified as a common cause of diarrhoea in immunocompetent individuals. In immunocompromised, especially HIV-infected subjects, cryptosporidiosis causes severe chronic diarrhoea. In this study, nitazoxanide (NTZ) was compared for curative activity with sinefungin (SNF) and paromomycin (PRM) in immunosuppressed rats, a screening model for anticryptosporidial agents. NTZ at either 50 mg/kg/day, 100 mg/kg/day or 200 mg/kg/day resulted in seven days in a dose-dependent inhibition of oocyst shedding similar to that obtained with SNF (10 mg/kg/day) and PRM (100 mg/kg/day). Further discontinuation of SNF or PRM 100 mg/kg/day therapy resulted in early relapse of oocyst shedding which reached the pre-treatment levels in 2-4 days. In contrast, seven days after discontinuation of therapy, shedding inhibition was unchanged in NTZ-treated rats. Data prompt further assessment of the activity of NTZ on sequestered C. parvum.

In vitro parasiticidal effect of Nitazoxanide against Echinococcus multilocularis metacestodes

When humans serve as inadvertent intermediate hosts for Echinococcus multilocularis, disease (alveolar echinococcosis [AE]) may result from the expanding parasite metacestode in visceral organs, mostly in the liver. Benzimidazole carbamate derivatives such as mebendazole and albendazole are used for chemotherapeutic treatment of AE. However, these treatments are, in most cases, parasitistatic rather than parasiticidal. As treatment is discontinued, a recurrence of parasite growth has been observed in many AE patients with nonradical resections. The only curative treatment for AE is radical surgical resection of the parasite tissue and support by chemotherapy. As there is a need for new treatment options for AE, the in vitro efficacy of nitazoxanide (NTZ), a broad-spectrum drug used against intestinal parasites and bacteria, was investigated. We showed that in vitro treatment of E. multilocularis metacestodes with NTZ induced high levels of alkaline phosphatase activity in the medium. Concurrently, distinct morphological and ultrastructural alterations were detected. Most significantly, two distinct types of alterations were observed as soon as after 3 h of NTZ treatment. At first, the drug induced a peripheral output of membranous vesicles from the tegumental membrane into the laminated layer. Simultaneously, germinal layer-associated undifferentiated cells produced large vacuoles filled with lipid-like and often electron-dense membranous segments. Other alterations were observed at later time points, including vacuolization of the germinal layer, accumulation of lipid droplets, and lastly, loss of microtriches and separation of the laminated and germinal layers. The pattern of damage induced by NTZ was different from the alterations earlier observed in albendazole sulfoxide-treated vesicles. The nonviability of NTZ-treated metacestodes was confirmed through bioassay, i.e., inoculation of treated and untreated parasites into mice. These experiments demonstrate the in vitro parasiticidal effect of NTZ on E. multilocularis metacestodes.

In-vitro transfer of nitazoxanide across the intestinal epithelial barrier

Nitazoxanide is a thiazolide compound that exhibits antimicrobial properties against helminths, protozoa, anaerobic bacteria and also Helicobacter pylori. The mucosal diffusion of this new drug has not been studied. The aim of this study was to examine the transport of radiolabelled nitazoxanide across the epithelial barrier according to the mode (mucosal or serosal) of drug administration. HT29-19A intestinal epithelial cells, grown as monolayers on microporous filters, were used as an epithelial model. In a short-term (100 min) transport study, the apical to basal and the basal to apical transport of nitazoxanide across the monolayers was studied in an Ussing chamber. In a long-term (24 h) study, the transport of the drug and its intracellular accumulation were studied in filter-grown epithelial monolayers kept in culture plates. In the short-term transport study, both the apical and basal fluxes achieved a steady state after 70 min and there was no significant difference between the apical to basal (3991+/-1001 ng h(-1) cm(-2)) and the basal to apical (4246+/-856 ng h(-1) cm(-2)) nitazoxanide fluxes. In the long-term transport study, after apical or basal drug application, a gradual increase in the drug concentration in the opposite compartment was noted, which reached similar values for apical and basal fluxes (2497+/-125 and 2309+/-81 ng mL(-1), respectively) after 24 h. Moreover, a rapid, although transitory, intracellular accumulation of nitazoxanide was observed at 10 min after apical (299+/-25 ng/10(6) cells) and basal (124+/-10 ng/10(6) cells) drug application, but decreased thereafter. There is an important transepithelial transport of nitazoxanide across the digestive epithelial monolayer with a rapid intracellular accumulation of the drug. No difference between the apical to basal and basal to apical fluxes of the drug was observed, suggesting that both topical and systemic modes of action of this antibiotic are successful.

Enzymes associated with reductive activation and action of nitazoxanide, nitrofurans, and metronidazole in Helicobacter pylori

Nitazoxanide (NTZ) is a redox-active nitrothiazolyl-salicylamide prodrug that kills Helicobacter pylori and also many anaerobic bacterial, protozoan, and helminthic species. Here we describe development and use of a spectrophotometric assay, based on nitroreduction of NTZ at 412 nm, to identify H. pylori enzymes responsible for its activation and mode of action. Three enzymes that reduce NTZ were identified: two related NADPH nitroreductases, which also mediate susceptibility to metronidazole (MTZ) (RdxA and FrxA), and pyruvate oxidoreductase (POR). Recombinant His-tagged RdxA, FrxA, and POR, overexpressed in nitroreductase-deficient Escherichia coli, each rapidly reduced NTZ, whereas only FrxA and to a lesser extent POR reduced nitrofuran substrates (furazolidone, nitrofurantoin, and nitrofurazone). POR exhibited no MTZ reductase activity either in extracts of H. pylori or following overexpression in E. coli; RdxA exhibited no nitrofuran reductase activity, and FrxA exhibited no MTZ reductase activity. Analysis of mutation to rifampin resistance (Rif(r)) indicated that NTZ was not mutagenic and that nitrofurans were only weakly mutagenic. Alkaline gel DNA electrophoresis indicated that none of these prodrugs caused DNA breakage. In contrast, MTZ caused DNA damage and was strongly mutagenic. We conclude that POR, an essential enzyme, is responsible for most or all of the bactericidal effects of NTZ against H. pylori. While loss-of-function mutations in rdxA and frxA produce a Mtz(r) phenotype, they do not contribute much to the innate susceptibility of H. pylori to NTZ or nitrofurans.

In vitro activity of linezolid against Clostridium difficile

We examined the in vitro activity of linezolid against Clostridium difficile, including isolates with reduced susceptibility to metronidazole or vancomycin. The MIC at which 50% of the isolates were inhibited (MIC50) and MIC90 were 0.5 and 2 microg/ml, respectively (range, 0.03 to 4 microg/ml). MICs were always <or= 4 microg/ml, and thus, all isolates were considered susceptible.

In vitro effect of nitazoxanide against Entamoeba histolytica, Giardia intestinalis and Trichomonas vaginalis trophozoites

Nitazoxanide, a 5-nitrothiazolyl derivative, is effective in the treatment of a broad range of parasitic infections. In vitro, it is active against several protozoa, including Cryptosporidium parvum, Blastocystis hominis, and Giardia intestinalis. The objective of this study was to determine the in vitro effect of nitazoxanide on the growth and morphology of three anaerobic protozoa (Entamoeba histolytica, Giardia intestinalis, and Trichomonas vaginalis) and to compare these effects with those of metronidazole and albendazole. A subculture method was used to determine the concentrations required to inhibit growth by 50% or 90% (IC50 and IC90,). Nitazoxanide exhibited IC50, and IC90 values of 0.017 and 0.776 microg/ml respectively, against E. histolytica, 0.004 and 0.067 microg/ml against G. intestinalis, and 0.034 and 2.04 6 microg/ml against T. vaginalis. Based on the IC90 values, nitazoxanide was more toxic than metronidazole and albendazole against E. histolytica; albendazole and nitazoxanide were more toxic than metronidazole against G. intestinalis; and metronidazole was the most toxic drug against T. vaginalis. The effects of nitazoxanide on trophozoite ultrastructure of all three parasites included cell swelling and distorted cell shape, a redistribution of vacuoles, plasma membrane damage, and the formation of extensive empty areas in the cytoplasm of the protozoa.

Recent advances in the search for new anti-coccidial drugs

Coccidia provide a rich hunting ground for drug-designers, as there are significant biochemical differences between the parasites and their hosts. Recent years have brought the discovery of the plastid and its possible metabolic machinery, characterisation of acidocalcisomes, reports on the apparent absence from some coccidia of a typical mitochondrion, and the discovery of the mannitol cycle and shikimate pathway in the parasites. Moreover, modern technologies such as genomics and proteomics are bringing new insights into the biochemistry of coccidia and highlighting possible drug targets in abundance. A major issue for would-be drug discoverers is to decide upon the targets to prioritise. This review provides an update on recent findings on how coccidia differ biochemically from vertebrates. It includes discoveries within coccidian parasites themselves but also uses findings in Plasmodium to provide an overview of biochemical features that may be characteristics of many apicomplexan parasites and so potential targets for broad-spectrum drugs.

Randomized clinical study of nitazoxanide compared to metronidazole in the treatment of symptomatic giardiasis in children from Northern Peru

BACKGROUND

Enteric infection by Giardia intestinalis is a common cause of diarrhoea world-wide and a significant cause of morbidity in children.

AIM

To compare the efficacy and safety of nitazoxanide and metronidazole in the treatment of diarrhoea caused by G. intestinalis in children.

METHODS

A total of 110 children presenting with diarrhoea caused by G. intestinalis were randomized to treatment with either a 3-day course of nitazoxanide (100 mg b.d., age range 2-3 years; 200 mg b.d., age range 4-11 years) or a 5-day course of metronidazole (125 mg b.d., age range 2-5 years; 250 mg b.d., age range 6-11 years). The patients were followed-up for a determination of clinical response 7 days after the initiation of treatment, and two subsequent stool samples were collected for parasitological examination.

RESULTS

Diarrhoea had resolved in 47 children out of 55 (85%) in the nitazoxanide treatment group before the day 7 follow-up visit, compared to 44 out of 55 (80%) for metronidazole. Diarrhoea resolved within 4 days in most cases. Only mild, transient adverse events were reported.

CONCLUSIONS

A 3-day course of nitazoxanide suspension is as efficacious as a standard 5-day course of metronidazole suspension in treating giardiasis in children.