Diagnosis of Clostridium difficile-associated intestinal disease

Toxigenic Clostridium difficile is the major cause of antimicrobial agent-associated pseudomembranous colitis and is the etiological agent of approximately 30% of cases of nonspecific colitis and diarrhea (without colitis) induced by antimicrobial agents. In addition, C. difficile has been implicated in certain intestinal diseases not related to prior antimicrobial administration. C. difficile has been reported to be one of the most common enteropathogens isolated from stool specimens submitted to hospital laboratories. Thus, diagnosis of C. difficile-associated intestinal disease should now be routinely performed in diagnostic clinical laboratories. The diagnosis of C. difficile-associated intestinal disease relies on the demonstration of either the organism or the toxin(s) in stool specimens or antibody response in serum to the toxin(s). Several selective medium are available for the recovery of C. difficile from stool specimens. The toxin(s) of C. difficile can be demonstrated using a variety of techniques, including biological assays as well as immunological assays. This article will review the techniques currently available to aid in the diagnosis of C. difficile-associated intestinal disease.     

Third generation cephalosporins as a risk factor for Clostridium difficile-associated disease: a four-year survey in a general hospital

The main clinical features of patients who developed pseudomembranous colitis (PMC) or Clostridium difficile-associated diarrhoea (CDAD) during their stay at the S. Anna General Hospital, Como, over the period February 1984 to May 1988, are reported. Forty patients developed either CDAD (ten cases) or PMC (30 cases). Twenty-seven (65.7%) had undergone surgery and 32 (80.0%) had received prolonged antibiotic treatment. Three patients (7.5%) were given three doses only of ceftriaxone. Five patients (12.5%) had not received any antibiotic treatment; but three were nursed in a bed next to a patient with PMC-CDAD. The number of cases diagnosed were correlated retrospectively with the cumulative consumption of different groups of antibiotics on wards in which PMC or CDAD occurred. A significant difference (P less than 0.01) between third generation cephalosporins (16 cases) and ureidopenicillins (one case), was found. Twenty-five patients were treated with oral vancomycin. Two died of the underlying disease and 23 were cured. The disease recurred clinically in three, and follow-up cultures were positive in another asymptomatic case. Fifteen patients (all PMC cases) were treated with oral teicoplanin. All were clinically cured and remained asymptomatic and all but one were also cleared of C. difficile. No adverse reactions were observed in patients given either drug. Third generation cephalosporins, even when administered as short-term perioperative prophylaxis, but not ureidopenicillins, are significantly associated with C. difficile-related diseases. Teicoplanin proved to be very effective and safe in the treatment of PMC, and should be further evaluated there.     

Clostridium difficile-associated diarrhea and chronic renal insufficiency

BACKGROUND: Clostridium difficile-associated diarrhea (CDAD) is a common cause of mortality and morbidity in hospitalized patients. Some case reports have implicated renal failure as a risk factor for CDAD. The aim of this study was to assess whether chronic renal insufficiency is a risk factor for CDAD and whether it increases mortality and morbidity. METHOD: We reviewed charts of 385 patients with diarrhea for CDAD, chronic renal insufficiency, mortality, and recurrence of CDAD. RESULTS: Seventy-seven patients had infection due to C difficile. There was no difference in the chronic renal insufficiency, mortality, and other comorbid conditions between patients who had C difficile infection and those who did not. The patients with CDAD and chronic renal insufficiency had significantly higher mortality and recurrence of CDAD than patients without chronic renal insufficiency. CONCLUSIONS: Chronic renal insufficiency is not a risk factor for CDAD, but its presence with CDAD increases mortality and recurrence of CDAD.     

Clostridium difficile-associated disease: new challenges from an established pathogen

Clostridium difficile-associated disease (CDAD) can range from uncomplicated diarrhea to sepsis and even death. CDAD rates and severity are increasing, possibly due to a new strain. Transmission of C difficile occurs primarily in health care facilities via the fecal-oral route following transient contamination of the hands of health care workers and patients; contamination of the patient care environment also plays an important role.     

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.     

Treatment of Clostridium difficile-associated diarrhea

OBJECTIVE: To review the literature related to the treatment and infection control of Clostridium difficile-associated diarrhea (CDAD). DATA SOURCES: A MEDLINE search (1966-August 2001) of the English literature was conducted. DATA SYNTHESIS: C. difficile is a leading cause of antibiotic-related diarrhea. The clinical spectrum extends from simple diarrhea to fulminant colitis. Cessation of antibiotic therapy alone is sufficient for mild cases; however, the majority of cases require oral metronidazole as the drug of choice. Vancomycin orally is reserved for patients who have failed to respond to metronidazole, are pregnant, or are severely ill. There is an important role for infection control interventions. CONCLUSIONS: CDAD is a common infection. Appropriate antibiotic treatment and infection control policies can prevent the spread and reduce the morbidity associated with this disease.     

Pseudomembranous colitis in spinal cord injury

Pseudomembranous colitis is a well-known disease associated with antibiotic administration and caused by the Clostridium difficile toxin. Clinical presentation is usually marked by watery diarrhea, crampy abdominal pain, and fever. Since early appropriate therapy can reduce morbidity and mortality, it is important for health care professionals to be aware of this disease. Patients with spinal cord injury have a relatively high incidence of respiratory and urinary tract infections that are treated with antibiotics. Therefore, these patients theoretically have a higher risk of contracting pseudomembranous colitis. This article presents a case report of a spinal cord injured patient with this disease who has several of the common difficulties encountered in the diagnosis and treatment, such as indeterminate assays and relapses. The clinical presentation, diagnosis, and treatment of pseudomembranous colitis are described.     

Clostridium difficile-associated diarrhoea in hospitalised patients

OBJECTIVE: The aim of the present study was to evaluate the incidence, risk factors and cost implications of Clostridium difficile-associated diarrhoea (CDAD) in hospitalized adult patients. METHODS: Eighty-seven hospitalized adult patients, positively identified as having CDAD, were reviewed retrospectively to determine the risk factors and cost implications of CDAD. RESULTS: The clinical manifestations, in addition to diarrhoea, included elevated temperature (= 37.8 degrees C; 42.5%), abdominal pain (63. 2%) and leucocytosis (=12 x 109 cells/l; 52.9%). Eight patients underwent endoscopy, and pseudomembranous colitis was confirmed in all of these patients. Nine patients died during their hospital stay. Cefotaxime and cefuroxime were the agents most commonly associated with CDAD. There was a significant difference (P < 0.001) between the sex distribution of CDAD patients and adult hospital patients (69% of CDAD patients were female vs. 52% of general adult hospital population). Significantly (P < 0.001) more patients with CDAD were admitted from the nursing home (NH) setting. The mean age of patients with CDAD admitted from NHs (n = 19) was older than those cases admitted from the community (n = 68) by 14 years (P < 0.001). The length of hospital stay was significantly (P < 0.001) longer for patients with CDAD (16.9 vs. 3.89 days). No differences (P = 0.306) were found in the response times for CDAD patients treated with either oral metronidazole (n = 39) or oral vancomycin (n = 48). The mean response time was, however, significantly longer in the CDAD patients admitted from NHs (4.2 days) compared with those admitted from the community (2.5 days), although the former patients were older and had significantly more comorbidity (P < 0.001). The mean cost per one treated-case of CDAD (bed, laboratory requests and treatment therapy) was calculated as pound2860. CONCLUSION: Patients admitted from NHs are at increased risk of development of CDAD; receiving cefotaxime or cefuroxime axetil (oral form), being elderly and being female are risk factors for the development of CDAD. Treatment of CDAD with oral metronidazole or oral vancomycin gives rise to similar response times and efficacy.     

Evaluation of a commercial latex agglutination assay for screening for Clostridium difficile-associated disease.

OBJECTIVE: To determine if the Clostridium difficile latex agglutination assay is an effective screening procedure for the diagnosis of C. difficile-associated disease (CDAD). DESIGN: Convenience sample. SETTING: The Washington Hospital, a 364-bed, secondary, acute-care center in Washington, Pennsylvania. PARTICIPANTS: A total of 321 women and 195 men aged 21 days to 100 years. INTERVENTIONS: Diarrheal stool specimens from patients on antibiotic therapy were randomly tested for the presence of C. difficile-associated antigen by CULTURETTE brand latex agglutination assay (Beckton Dickinson Microbiology Systems, Cockeyesville, MD 21030). Latex-positive samples were confirmed or negated by cytotoxin assay using the Toxi-titer microtiter plate system (Baxter Healthcare Corp., Bartels Diagnostic Division, Issaquah, WA 98027). MAIN OUTCOME MEASURES: Comparative statistical analysis of the raw data to develop the sensitivity and specificity of the latex screening assay. RESULTS: Stool specimens of 403 patients (78.1%) were negative for C. difficile-associated antigen. Of the latex-positive specimens, 70 (69.3%) were also cytotoxin-positive. Of the indeterminate latex specimens, four (33.3%) were cytotoxin-positive. A total of 70 specimens (13.6%) were positive by both methods and 74 patients (14.3%) were diagnosed with CDAD. Based on this data, the latex agglutination screening assay had a sensitivity of 77.1% and a specificity of 93.4%. CONCLUSION: Latex agglutination for C. difficile-associated antigen is a moderately sensitive screening test for a presumptive diagnosis of CDAD. However, it is not the best screening test for CDAD compared with the new enzyme-linked immunosorbent assay (ELISA) techniques for toxins A and B.     

Prospective study of oral teicoplanin versus oral vancomycin for therapy of pseudomembranous colitis and Clostridium difficile-associated diarrhea.

A prospective, randomized study comparing oral teicoplanin with oral vancomycin in the treatment of pseudomembranous colitis (PMC) and Clostridium difficile-associated diarrhea (CDAD) was performed. Teicoplanin was administered at a dosage of 100 mg twice a day for 10 days, and vancomycin was administered at a dosage of 500 mg four times a day for 10 days. CDAD was diagnosed by demonstrating both C. difficile and cytotoxin in the feces of symptomatic patients (more than three loose stools per day). The diagnosis of PMC was also based on colonoscopy. Cytotoxin assay and cultures were checked in all patients 7 to 10 days after discontinuation of therapy and 25 to 30 days thereafter. Of the 51 patients enrolled, 46 were judged to be assessable. Among these, 26 received teicoplanin and 20 received vancomycin. At enrollment, both groups were comparable in terms of age, sex, occurrence of PMC or CDAD, and previous antibiotic treatment. Eighteen of the 20 patients in the vancomycin group and 10 of the 26 patients in the teicoplanin group had previously undergone surgery (P = 0.0004). Treatment resulted in the clinical cure of 20 (100%) vancomycin and 25 (96.2%) teicoplanin patients (P = 0.56). After discontinuation of therapy, clinical symptoms recurred in four (20%) vancomycin patients and two (7.7%) teicoplanin patients (P = 0.21). Posttherapy asymptomatic C. difficile carriage (positive follow-up cultures without any clinical symptoms) occurred in five (25%) vancomycin patients and two (7.7%) teicoplanin patients (P = 0.11).Overall, 9 of 20 (45%) vancomycin patients and 5 of 26 (19.2%) teicoplanin patients (P=0.059) appeared not to be cleared of C. difficile after treatment. No adverse effects related to vancomycin or teicoplanin therapy were observed.     

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.     

How to identify the cause of antibiotic-associated diarrhea

Most cases of antibiotic-associated diarrhea are due to Clostridium difficile or are of enigmatic etiology. The antibiotics most often implicated are clindamycin, ampicillin or amoxicillin, and the cephalosporins. Clinical signs of antibiotic-associated diarrhea may be limited to watery stools; however, evidence of colitis (fever, cramps, leukocytosis, fecal leukocytes) suggests C. difficile infection. The tissue culture assay for C. difficile toxin remains the gold standard for diagnosis, but the enzyme immunoassay is a practical and reasonably accurate alternative. Anatomic changes, such as pseudomembranes, can be confirmed with endoscopy, but such evaluation is not required for diagnosis of C. difficile-associated pseudomembranous colitis.     

Identification, optimal management, and infection control measures for Clostridium difficile-associated disease in long-term care

Residents of long-term care facilities are at an increased risk of exposure to Clostridium difficile and become more susceptible to infection after receiving antimicrobial therapy. An increasing number and more severe cases of C. difficile-associated disease (CDAD) have been reported over the last few years and have been linked to the emergence of a new, more virulent strain of C. difficile. These serious cases of disease have also been associated with a more atypical clinical presentation and have prompted the need for an improved means of early recognition and identification performed by the nursing staff. This article reviews the pathogenesis and risk factors for CDAD, changing epidemiology of CDAD, and characteristics of the newly identified strain. Also reviewed are the role of nursing in the identification of patients with CDAD; optimal management of CDAD; infection control strategies; and education of health care professionals, residents, and visitors in the long-term care setting.     

An outbreak case of Clostridium difficile-associated diarrhea among elderly inpatients of an intensive care unit of a tertiary hospital in Rio de Janeiro, Brazil

The aim of this study was to investigate Clostridium difficile-associated diarrhea (CDAD) in an intensive care unit (ICU) of a tertiary hospital in Rio de Janeiro, Brazil, and to characterize epidemiologically C. difficile strains obtained from an outbreak of CDAD. Within almost a 4-year surveillance period, CDAD incidence was determined for the first time in Brazil, and a 3-fold increase was observed in the average rate of CDAD, featuring an outbreak. About 80% of the patients were over 65 years. The main antibiotic that could be probably associated to CDAD was piperacillin/tazobactam. Four toxigenic strains were isolated, 3 from stools and 1 from environmental samples. They were all resistant to clindamycin and fluoroquinolones. Fingerprinting analysis revealed their distribution between 2 different polymerase chain reaction ribotypes, with one of them being exclusively found in Brazil. It was possible to detect cross-infection and environmental contamination in the ICU. Our results highlight the importance of a continuous CDAD surveillance in the hospitals, especially when a risk group is exposed.     

Application of isothermal helicase-dependent amplification with a disposable detection device in a simple sensitive stool test for toxigenic Clostridium difficile

Enzyme immunoassays (EIAs) are commonly used for the diagnosis of cases of Clostridium difficile-associated diarrhea (CDAD). However, these EIAs have high false-negative rates, even in patients with severe clinical disease. We have developed an IsoAmp CDAD test using a simple and user-friendly procedure to identify toxigenic C. difficile in feces. After DNA extraction from fecal samples, both the conserved sequence of the 5'-end fragment of the C. difficile tcdA toxin gene and competitive amplification internal control sequence were amplified using helicase-dependent amplification. Amplification products were detected using a novel amplicon-containment detection device. The analytical sensitivity of the assay was 20 copies of C. difficile genomic DNA per reaction. Evaluation of the clinical sensitivity and specificity of the IsoAmp CDAD test versus an EIA method using a PCR method as the reference standard revealed 100% sensitivity and 100% specificity for the IsoAmp CDAD test compared with 90.9% sensitivity and 100% specificity for the EIA method. Because the IsoAmp CDAD test requires no expensive equipments for nucleic acid amplification or detection and can be performed on a random access basis, the test provides a practical alternative to immunoassays for the diagnosis of CDAD with improved sensitivity.     

A double-blind randomized controlled trial of fusidic acid and metronidazole for treatment of an initial episode of Clostridium difficile-associated diarrhoea

OBJECTIVES: Few treatment options are currently available to treat patients suffering from an initial episode of Clostridium difficile-associated diarrhoea (CDAD). PATIENTS AND METHODS: A prospective, randomized controlled, double-blind trial was conducted to compare the efficacy of fusidic acid and metronidazole for treatment of patients experiencing a first episode of CDAD. The primary outcomes were clinical cure and clearance of C. difficile toxin determined on days 8-13, and secondary outcomes were clinical recurrence and reappearance of C. difficile toxin evaluated on days 35-40. RESULTS: Of the patients in the fusidic acid group, 83% were clinically cured in comparison to 93% in the metronidazole group (P=0.116) at the first follow-up visit. Clearance of C. difficile toxin did not differ between the two groups at that time. Clinical recurrence and reappearance of C. difficile toxin were noted in 27% and in 13% of the patients receiving fusidic acid, respectively and in 29% and 10% of those given metronidazole at the second follow-up on days 35-40. CONCLUSION: Since three of the four primary and secondary outcomes were almost identical for the two groups, the results indicate that fusidic acid is as effective as metronidazole in curing an initial episode of CDAD and can therefore be considered as an adequate alternative for treatment of this disease.     

Mutations in fusA associated with posttherapy fusidic acid resistance in Clostridium difficile

In silico, we identified fusA (2,067 bp) in Clostridium difficile 630. Sequencing of fusA in posttherapy fusidic acid-resistant C. difficile isolates from 12 patients with C. difficile-associated diarrhea (CDAD) identified fusA mutations, one or two nonsynonymous substitutions, or in one case a deletion of one codon associated with resistance. Five of these mutations have previously been described in fusA of fusidic acid-resistant Staphylococcus aureus, but seven were novel fusA mutations. Fusidic acid monotherapy for CDAD seemed to rapidly select conserved resistant mutants.     

Performance of TechLab C. DIFF QUIK CHEK and TechLab C. DIFFICILE TOX A/B II for the detection of Clostridium difficile in stool samples

Two membrane-bound enzyme immunoassays by TechLab, Blacksburg, VA, were evaluated and compared with the Triage Micro C. difficile Panel (Biosite Diagnostics, San Diego, CA), with culture, and with cytotoxic assay. The TechLab panels were C. DIFF QUIK CHEK (QC-GDH) and C. DIFFICILE TOX A/B II (QC-toxinA/B), which detect glutamate dehydrogenase (GDH) and Clostridium difficile toxins A and B, respectively. The Triage Panel detects GDH (TR-GDH) and toxin A (TR-toxinA). METHODS: Stool samples were inoculated onto CCFA plates (Q-Labs, Quebec, Canada) after alcohol shock, and suspected colonies were identified by the MicroScreen C. difficile latex slide agglutination test (Microgen Bioproducts, Surrey, UK). TR-GDH, TR-toxinA, QC-GDH, and QC-toxinA/B tests were performed according to the manufacturers' instructions on all the samples. Samples positive for GDH or culture but negative for TR-toxinA and QC-toxinA/B were further tested by cytotoxin assay (CTA). CTA was also performed on samples that caused blackening of the Triage Micro C. difficile Panel. RESULTS: A total of 313 of 401 stool samples were negative for GDH and toxins (78%). Eighty-eight samples were positive either for GDH or culture or both. Thirteen of these could not be evaluated for C. difficile-associated diarrhea (CDAD) because CTA test was not performed. Toxin/s was detected at least by one method in 46 (11.8%) of 388 samples that were positive for culture or GDH and were considered diagnostic of CDAD. The QC-GDH was more sensitive than culture and TR-GDH for the detection of C. difficile. However, in 18GDH-positive samples positive for either of the Triage or TechLab immunoassays, the culture remained negative. Ten (2%) results of the Triage immunoassays could not be evaluated because of discoloration of the panels. QC-GDH (93.5%) was more sensitive for detecting the presence of toxin-producing C. difficile than TR-GDH (79.5%). TR-toxinA was more specific for detecting the presence of toxin-producing C. difficile than QC-toxinA/B (100% and 96.9%, respectively). CONCLUSIONS: The GDH tests had a faster turnaround time than the traditional culture methods. QC-GDH was most sensitive for the detection C. difficile-positive stools and was easy to use.     

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.     

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

OBJECTIVES: Clostridium difficile-associated disease has increased in incidence and severity. Recommended treatments include metronidazole and vancomycin. Recent investigations, however, document the failure of metronidazole to cure a substantial proportion of patients with Clostridium difficile colitis, but oral administration of vancomycin raises concerns over selection of antibiotic-resistant organisms in the hospital environment. We have recently shown that nitazoxanide is as effective as metronidazole in initial therapy for C. difficile colitis. We hypothesized that this drug might be effective in treating patients who fail therapy with metronidazole. METHODS: In the present study, we identified 35 patients who failed treatment with metronidazole for C. difficile colitis; failure was defined as either no improvement in symptoms or signs of disease (28 patients) after >or= 14 days of treatment with metronidazole or prompt recurrence on at least two occasions after initially responding to such treatment (seven patients). These patients were ill with numerous co-morbidities. Nitazoxanide, 500 mg twice daily, was given for 10 days; results from all patients are included. RESULTS: Twenty-six (74%) of 35 patients responded to nitazoxanide, of whom seven later had recurrent disease, yielding a cure rate of 19 of 35 (54%) from initial therapy. Three who initially failed and one who had recurrent disease were re-treated with, and responded to, nitazoxanide. Thus, the aggregate cure with nitazoxanide in this difficult-to-treat population was 23 of 35 (66%). CONCLUSIONS: Nitazoxanide appears to provide effective therapy for patients with C. difficile colitis who fail treatment with metronidazole.