Reassessment of Clostridium difficile susceptibility to metronidazole and vancomycin

Antimicrobial susceptibility pattern of Clostridium difficile and its relation to PCR ribotypes in a Swedish university hospital

All 238 Clostridium difficile isolates were susceptible to metronidazole and vancomycin, whereas 84% and 1% were resistant to clindamycin and fusidic acid. Etest MICs for metronidazole were lower than agar dilution MICs (P < 0.01) but without difference in susceptible-intermediate-resistant categorization. No particular PCR ribotype was associated with clindamycin or fusidic acid resistance.

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.

Significant Absorption of Oral Vancomycin in a Patient with Clostridium difficile Colitis and Normal Renal Function

Orally-administered vancomycin is poorly absorbed in most patients, usually producing minimal or subtherapeutic serum concentrations. Bowel inflammation may enhance absorption of oral vancomycin, particularly in those with renal failure. A 77-year-old female with Clostridium difficile (C difficile) colitis and normal renal function was treated with high doses of oral vancomycin and achieved serum concentrations in the therapeutic range. To our knowledge, this is the first report of a patient with C difficile colitis and normal renal function to develop therapeutic serum concentrations following oral administration of vancomycin.

Molecular characterization ofClostridium difficileisolates from horses in an intensive care unit and association of disease severity with strain type

OBJECTIVE

To determine molecular characteristics, antimicrobial susceptibility, and toxigenicity of Clostridium difficile isolates from horses in an intensive care unit and evaluate associations among severity of clinical disease with specific strains of C difficile.

DESIGN

Prospective study.

ANIMALS

130 horses.

PROCEDURES

Feces were collected from horses admitted for acute gastrointestinal tract disease with loose feces and submitted for microbial culture and immunoassay for toxin production. Polymerase chain reaction assays were performed on isolates for toxins A and B genes and strain identification.

RESULTS

Isolates were grouped into 3 strains (A, B, and C) on the basis of molecular banding patterns. Toxins A and B gene sequences were detected in 93%, 95%, and 73% of isolates of strains A, B, and C, respectively. Results of fecal immunoassays for toxin A were positive in 40%, 63%, and 16% of horses with strains A, B, and C, respectively. Isolates in strain B were resistant to metronidazole. Horses infected with strain B were 10 times as likely to have been treated with metronidazole prior to the onset of diarrhea as horses infected with other strains. Duration from onset of diarrhea to discharge (among survivors) was longer, systemic inflammatory response syndromes were more pronounced, and mortality rate was higher in horses infected with strain B than those infected with strains A and C combined.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses may be infected with a number of heterogeneous isolates of C difficile. Results indicated that toxigenicity and antimicrobial susceptibility of isolates vary and that metronidazole-resistant strains may be associated with severe disease.

Diarrhea in patients with AIDS

Diarrhea in patients with AIDS is a worldwide problem that can have a devastating impact on quality of life for the patient. Chronic diarrhea, usually defined as at least 4 weeks' duration, is more common in patients with low CD4-positive T-lymphocyte counts, signaling advanced immunosuppression. Some organisms, such as Microsporidia, usually cause diarrhea only in the immunosuppressed; others, such as Cryptosporidium, Salmonella, Shigella, and Campylobacter, which are capable of causing diarrhea in the immunocompetent population, produce more severe or prolonged infections in people living with AIDS. Familiarity with the most common pathogens in the clinician's region will help with diagnosis and treatment. Because treatment options vary widely depending upon the infectious agent, thorough microbiologic evaluation is warranted. A stepped diagnostic approach of stool cultures and specialized microscopy and stains for protozoa, followed by sigmoidoscopy or colonoscopy and duodenoscopy with biopsies for histopathological examination is recommended in all patients with persistent, disabling diarrhea who have a CD4 count of less than 200/mm3, and should be considered for those with higher counts on an individual basis. Treatment, tailored to the specific pathogen, may need to be prolonged in the most severely immunocompromised patients to prevent relapse or recrudescence. For patients taking antiretroviral therapy (especially protease inhibitors) in whom no infectious agent can be found, diarrhea may be due to the medications. Nonspecific antidiarrheal agents should be tried until one that suits the patient is found. The most essential component of any therapeutic strategy for a patient with AIDS-associated diarrhea is restoration of the underlying immunologic defect using highly active antiretroviral therapy.

Antimicrobial resistance of Clostridium difficile isolates in a tertiary medical center, Israel

The antimicrobial susceptibilities of 49 Clostridium difficile isolates obtained from patients with C. difficile-associated diarrhea to metronidazole, vancomycin, rifampicin, fusidic acid, doxycycline, and linezolid were determined by the disc diffusion and Etest (Biodisk, Solna, Sweden). Random amplification of polymorphic DNA-PCR amplification assay was performed for studying clonality of isolates. Resistance to metronidazole was found in 2% (1/49 isolates; MIC > or = 256 microg/mL) of isolates and resistance to linezolid in 2% (1/49 isolates; MIC = 24 microg/mL). One isolate showed combined resistance to fusidic acid (by disc diffusion test) and rifampicin (MIC > or = 32 microg/mL). All isolates were sensitive to doxycycline and vancomycin. Molecular typing revealed an absence of clonality among the resistant isolates, whereas the sensitive isolates were monoclonal. Resistance of C. difficile to metronidazole and other antimicrobials including linezolid exists in our institution. This finding should promote exploration of this problem in Israel and clarify the impact of resistance on outcome.

Continuation of antibiotics is associated with failure of metronidazole for Clostridium difficile-associated diarrhea

BACKGROUND

Metronidazole is first-line therapy for C. difficile-associated diarrhea primarily because of its low cost relative to vancomycin. Currently, it is unknown which patients will fail metronidazole therapy. Our goal was to prospectively evaluate risk factors for metronidazole failure.

STUDY

Included patients had symptomatic C. difficile-associated diarrhea, either mild or severe. Once enrolled, detailed baseline data were gathered. All interviews were performed daily while the patient was in the hospital for up to 14 days. If discharged prior to 14 days, the patient received a follow-up phone call on day 5 and day 14. Enrolled patients were given a daily stool survey to complete.

RESULTS

We enrolled 27 patients with C. difficile-associated diarrhea. All patients (10 of 10) who had their offending antibiotic(s) discontinued had symptomatic resolution of diarrhea by day 14 of metronidazole treatment. Conversely, 59% (10 of 17) of patients who remained on antibiotics during treatment had symptomatic resolution by day 14 (P=0.02). The risk ratio for treatment failure was 2.0 (95% confidence interval, 1.29-3.10) in patients who remained on antibiotics. In our treatment group, there would be one additional metronidazole treatment success for every 2.4 patients who discontinued antibiotics.

CONCLUSION

Patients who remain on antibiotics while undergoing treatment of C. difficile-associated diarrhea have a high likelihood of treatment failure with metronidazole.

Crystal structure of receptor-binding C-terminal repeats from Clostridium difficile toxin A

Clostridium difficile is a major nosocomial pathogen that produces two large protein toxins [toxin A (TcdA) and toxin B (TcdB)] capable of disrupting intestinal epithelial cells. Both belong to the family of large clostridial cytotoxins, which are characterized by the presence of a repetitive C-terminal repetitive domain (CRD). In TcdA, the CRD is composed of 39 repeats that are responsible for binding to cell surface carbohydrates. To understand the molecular structural basis of cell binding by the toxins from C. difficile, we have determined a 1.85-A resolution crystal structure of a 127-aa fragment from the C terminus of the toxin A CRD. This structure reveals a beta-solenoid fold containing five repeats, with each repeat consisting of a beta-hairpin followed by a loop of 7-10 residues in short repeats (SRs) or 18 residues in long repeats (LRs). Adjacent pairs of beta-hairpins are related to each other by either 90 degree or 120 degree screw-axis rotational relationships, depending on the nature of the amino acids at key positions in adjacent beta-hairpins. Models of the complete CRDs of toxins A and B suggest that each CRD contains straight stretches of beta-solenoid composed of three to five SRs that are punctuated by kinks introduced by the presence of a single LR. These structural features provide a framework for understanding how large clostridial cytotoxins bind to cell surfaces and suggest approaches for developing novel treatments for C. difficile-associated diseases by blocking the binding of toxins to cell surfaces.

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.

Clinical manifestations, treatment and control of infections caused by Clostridium difficile

Clostridium difficile should be suspected in patients who present with nosocomial diarrhoea. It is more common in the elderly or in patients with a debilitating underlying condition who have received antimicrobial agents, and up to 20-25% of patients may experience a relapse. The reference method for diagnosis is the cell culture cytotoxin test which detects the presence of toxin B in a cellular culture of human fibroblasts, but recovering C. difficile in culture allows the performance of a ''second-look" cell culture assay that enhances the potential for diagnosis. Oral metronidazole (500 mg tid or 250 mg every 6 hrs) and oral vancomycin (125 mg every 6 hrs) administered for 1014 days have similar therapeutic efficacy, with response rates near 90-97%. C. difficile strains resistant to metronidazole and with intermediate resistance to vancomycin have been described. The administration of probiotics such as Saccharomyces boulardii, Lactobacillus sp. or brewer's yeast for prophylaxis of CDAD remains controversial.

A survey of metronidazole and vancomycin resistance in strains of Clostridium difficile isolated in Warsaw, Poland

The drug of choice used to treat Clostridium difficile-associated diarroea (CDAD) are metronidazole and vancomycin. Information about emergence of antimicrobial resistance among C. difficile strains to metronidazole and intermediate resistance to vancomycin in some countries are alarming. This study was performed to determine the susceptibility to metronidazole and vancomycin of 193 C. difficile strains isolated in our diagnostic laboratory between year 1998 and 2003 from patients adults and children suffering from CDAD. Among these strains, 142 produced toxin A and B (TcdA(+)TcdB(+)), 43 only B (TcdA(-)TcdB(+)) and 8 were nontoxigenic. We have not observed any differences in susceptibility to metronidazole and vancomycin between all C. difficile strains under investigation (toxinogenic and non-toxinogenic). Resistance to metronidazole and vancomycin was not observed.

In vitro activity of ramoplanin against Clostridium difficile, including strains with reduced susceptibility to vancomycin or with resistance to metronidazole

We evaluated the in vitro activity of ramoplanin, an antimicrobial compound that inhibits cell wall synthesis by acting at the level of lipid intermediate formation, against Clostridium difficile. We included strains with reduced susceptibilities to vancomycin (vancomycin-intermediate [Van(i)] strains) or with resistance to metronidazole (Mtz(r)), in order to assess the potential utility of ramoplanin for the treatment of C. difficile-associated diarrhea. We tested the activity of ramoplanin against a total of 105 nonduplicate clinical isolates of toxigenic C. difficile, including 8 Van(i) isolates and 6 Mtz(r) isolates, obtained from our laboratory. Ramoplanin was active against all strains tested at concentrations ranging from 0.03 to 0.5 microg/ml (MICs at which 50 and 90% of isolates were inhibited, 0.25 microg/ml; geometric mean MIC, 0.22 microg/ml). All isolates, independently of their levels of susceptibility to vancomycin or metronidazole, were considered susceptible to ramoplanin (MICs, < or =0.5 microg/ml).

Prevalence and characteristics of bacteria and host factors in an outbreak situation of antibiotic-associated diarrhoea

Antibiotic-associated diarrhoea (AAD) represents a clinical entity leading to prolonged hospital stays and diagnostic and therapeutic procedures, and results in additional costs. The aim of the present study was to assess the prevalence and characteristics of different bacteria in stools of patients with AAD. The reliability of diagnostic procedures under routine conditions was evaluated. Host factors were also analysed. From June 2002 to April 2003 89 cases of diarrhoea were reported at a hospital unit for internal medicine. Clostridium difficile and Clostridium perfringens toxin enzyme-immunoassays (EIAs), and culture for C. difficile, C. perfringens and Staphylococcus aureus were performed on stool samples from all patients. Toxin production was determined in isolated S. aureus strains. In vitro susceptibility of S. aureus for oxacillin and of C. difficile for vancomycin, metronidazole, linezolid, fusidic acid and tetracycline was tested. Host factors, such as age, comorbidities, antibiotic exposure and contact with other patients, were evaluated. Twenty-six stools were positive for C. difficile toxins by an EIA technique, while C. difficile was cultured from 39. C. difficile was isolated from 21 stools that were EIA negative. Additionally, from 28 stools S. aureus and/or C. perfringens could be isolated. Nine samples contained only S. aureus and/or C. perfringens. Thirty-one stools were negative in all tests. All C. difficile isolates were susceptible to vancomycin and metronidazole. Age >60 years, and diseases of the vascular system, the heart, the kidneys and the lungs were identified as risk factors for acquiring C. difficile in this setting (P values < 0.05). Stool culture for C. difficile was shown to be more sensitive than toxin EIA in this study. Risk factors for the acquisition of C. difficile in outbreak situations seem to differ from risk factors in the normal hospital setting. The role of toxin-producing S. aureus in cases of AAD needs further investigation.

Laboratory diagnosis of Clostridium difficile-associated diarrhoea: a plea for culture

A routine protocol for diagnosing Clostridium difficile-associated diarrhoea (CDAD) based on both faecal-cytotoxin detection and toxigenic culture was adopted by the microbiology laboratory of the St Luc-UCL University Hospital in Brussels in 1997. A toxigenic culture is a faecal culture followed, in the case of positivity, by a direct immunoassay on colonies to detect toxin A production. The results obtained over the past 7 years in the hospital are reviewed here. A total of 10,552 diarrhoeal stools from 7042 patients were analysed, of which 9494 were negative for all tests. A total of 1058 samples (10 %) from 794 patients were culture-positive, of which 460 (4.4 %) were positive for a faecal cytotoxin. The remaining 598 cultures were tested for toxin A on colonies; 355 of them were positive, which is 3.4 % of the total, and the remaining 243 (2.3 %) were negative. The positivity of the faecal-cytotoxin assay was statistically linked to the number of colonies observed on the culture plate. In conclusion, over a 7 year period, toxigenic culture allowed the diagnosis of 355 cases of CDAD that would have been missed by a protocol using a faecal-cytotoxin assay alone. In terms of both patient care, prevention of environmental contamination and prevention of risk of a hospital outbreak, it is proposed that these results justify the recommendation to perform both faecal-toxin assay and culture in routine medical practice.

Alternative treatments for Clostridium difficile disease: what really works?

Vancomycin and metronidazole have been used for treating Clostridium difficile-associated disease (CDAD) for the past 25 years, but approximately 20 % of patients develop recurrent disease. The increasing incidence of nosocomial outbreaks, cases of recurrent CDAD and other complications (toxic megacolon, ileus, sepsis) has fuelled the search for different types of treatments. As the understanding of the pathogenesis of this disease has matured, newer treatment strategies that take advantage of these mechanisms have been developed. This review will describe such treatments and examine the evidence for each strategy.

"Collateral damage": antibiotics and the risk of Clostridium difficile infection

Patients undergoing orthopedic surgery are at increased risk for infection, and antimicrobial use continues to be required. Antimicrobial selection, however, is an important consideration given the increasing incidence and severity of C. difficile infection described in the literature. When choosing antimicrobials for prophylaxis and treatment, evaluate patients for risk factors that may predispose them to C. difficile infection. Patients receiving multiple antibiotics or broad-spectrum antibiotics, women, patients with concurrent proton pump inhibitor use, and those with renal failure are at increased risk. Choice of antibiotics should be evaluated for their potential or likelihood to cause C. difficile infection. When a number of these risk factors are present, avoiding the use of high-risk antibiotics may be warranted.

Clostridium difficile-associated diarrhea in adults

Clostridium difficile is the most important cause of nosocomial diarrhea in adults. Illness may range from mild watery diarrhea to life-threatening colitis. An antecedent disruption of the normal colonic flora followed by exposure to a toxigenic strain of C. difficile are necessary first steps in the pathogenesis of disease. Diagnosis is based primarily on the detection of C. difficile toxin A or toxin B. First-line treatment is with oral metronidazole therapy. Treatment with oral vancomycin therapy should be reserved for patients who have contraindications or intolerance to metronidazole or who fail to respond to first-line therapy.

In vitro activity of OPT-80 against Clostridium difficile

Clostridium difficile remains the major cause of nosocomial diarrhea. Reports on impaired susceptibility of C. difficile to metronidazole and vancomycin and frequent relapses of patients after therapy necessitate the search for new substances. With this study, the activity of OPT-80, a new macrocycle, against 207 C. difficile strains and against other obligately anaerobic bacteria was tested. OPT-80 showed high in vitro activity against all C. difficile strains tested.

Bacteriotherapy using fecal flora: toying with human motions

The intestinal flora may play a key role in the pathogenesis of certain gastrointestinal (GI) diseases. Components of bowel flora such as Lactobacillus acidophilus and Bifidobacterium bifidus have long been used empirically as therapeutic agents for GI disorders. More complex combinations of probiotics for therapeutic bacteriotherapy have also recently become available, however the most elaborate mix of human-derived probiotic bacteria is, by definition, the entire fecal flora. Fecal bacteriotherapy uses the complete normal human flora as a therapeutic probiotic mixture of living organisms. This type of bacteriotherapy has a longstanding history in animal health and has been used sporadically against chronic infections of the bowel, especially as a treatment of last resort for patients with severe Clostridium difficile syndromes including recurrent diarrhea, colitis, and pseudomembranous colitis. Encouraging results have also been observed following infusions of human fecal flora in patients with inflammatory bowel disease, irritable bowel syndrome, and chronic constipation. The therapeutic use of fecal bacteriotherapy is reviewed here and possible mechanisms of action and potential applications explored. Published reports on fecal bacteriotherapy are few in number, and detail the results of small uncontrolled open studies and case reports. Nevertheless, given the promising clinical responses, formal research into fecal bacteriotherapy is now warranted.

Gastrointestinal disorders and the critically ill. Clostridium difficile infection and pseudomembranous colitis

Clostridium difficile causes a spectrum of diseases ranging from diarrhoea to pseudomembranous colitis, primarily in the hospitalized elderly, although community-acquired infection is probably under-documented. Host factors are increasingly recognized as critical determinants of disease expression. Exposure to antibiotics, particularly those adversely affecting anaerobic gut flora, appears to create a niche which is exploited by C. difficile. Several retrospective and intervention studies have indicated that third-generation cephalosporins have a high propensity to induce C. difficile diarrhoea. Conversely, some broad-spectrum antibiotics, including ureidopenicillins (e.g. piperacillin-tazobactam) and ciprofloxacin, are less likely to induce C. difficile infection. Effective control of C. difficile in the hospital requires both antibiotic control and prevention of environmental seeding and bacterial spread. Epidemic C. difficile strains are widely distributed in the hospital environment, both as a cause and result of nosocomial diarrhoea. Current treatment options are antibiotic-based, which is less than ideal. Although many biotherapeutic approaches have been tried few have shown real benefit.

Changes in sensitivity patterns to selected antibiotics in Clostridium difficile in geriatric in-patients over an 18-month period

Clostridium difficile-associated disease continues to be a major problem in hospitals and long-term care facilities throughout the developed world. Administration of certain antibiotics such as amoxycillin, oral cephalosporins and clindamycin is associated with the greatest risk of developing C. difficile disease. The two antibiotics used for treatment of C. difficile disease are vancomycin and metronidazole, to which there is currently very little resistance. Randomly selected isolates (186) from 90 patients being investigated during an 18-month epidemiological study into the disease were tested for their susceptibility to vancomycin, metronidazole, amoxycillin, clindamycin, cefoxitin and ceftriaxone by the NCCLS agar dilution method. There was a narrow range of MIC for the two treatment agents (vancomycin and metronidazole), from 0.5 to 4 microg ml(-1), with no evidence of resistance. All strains were resistant to cefoxitin (MIC 64-256 microg ml(-1)), the antibiotic used in most selective media. All strains were of similar sensitivity to amoxycillin (MIC(90)= 4 microg ml(-1)). Most strains were resistant to ceftriaxone (MIC > or = 64 microg ml(-1)) or of intermediate resistance (MIC > or = 32 microg ml(-1)), with only two sensitive strains (MIC 16 microg ml(-1)). Clindamycin resistance was common, with 67 % of strains resistant (MIC > or = 8 microg ml(-1)), 25 % with intermediate resistance (MIC > or = 4 microg ml(-1)) and only 8 % sensitive (MIC < or = 2 microg ml(-1)). Twelve isolates from six different patients had very high resistance to clindamycin (MIC > or = 128 microg ml(-1)). Multiple isolates from the same patient, taken at different times, showed changes in susceptibility patterns over time. The only major change in susceptibility over the time-period was in clindamycin resistance; some strains appeared to become more resistant while others became less resistant. No differences were seen in the MIC(50) and MIC(90) of the different S-types of C. difficile identified, although some S-types were present in very small numbers. There was no correlation between the antibiotics prescribed and susceptibility.

Clostridium difficile-associated Enteric Disease

Clostridium difficile was identified as the putative agent of antibiotic-associated pseudomembranous colitis in 1978 and is now recognized as the major identifiable cause of antibiotic-associated diarrhea. This microbe causes a spectrum of enteric disease ranging from nuisance diarrhea to life-threatening colitis. Risk factors include increasing age, exposure to antibiotics, colonization or acquisition of toxin-producing strains of C. difficile, and lack of circulating antibody to C. difficile toxin A. Detection is relatively simple by stool assay for C. difficile toxin--usually an enzyme immunoassay that will detect toxin A and B. Most nonsevere cases will respond with discontinuation of the implicated antibiotic. More severe cases require metronidazole and supportive care. The major complications include ileus, toxic megacolon, relapsing disease after antibiotic treatment, and nosocomial epidemics.