Antibiotic-associated pseudomembranous colitis: an epidemiologic investigation of a cluster of cases

Defining the black box: a narrative review of factors associated with adverse outcomes from severe Clostridioides difficile infection

In the United States, Clostridioides difficile infection (CDI) is the leading cause of healthcare-associated infection, affecting nearly half a million people and resulting in more than 20,000 in-hospital deaths every year. It is therefore imperative to better characterize the intricate interplay between C. difficile microbial factors, host immunologic signatures, and clinical features that are associated with adverse outcomes of severe CDI. In this narrative review, we discuss the implications of C. difficile genetics and virulence factors in the molecular epidemiology of CDI, and the utility of early biomarkers in predicting the clinical trajectory of patients at risk of developing severe CDI. Furthermore, we identify associations between host immune factors and CDI outcomes in both animal models and human studies. Next, we highlight clinical factors including renal dysfunction, aging, blood biomarkers, level of care, and chronic illnesses that can affect severe CDI diagnosis and outcome. Finally, we present our perspectives on two specific treatments pertinent to patient outcomes: metronidazole administration and surgery. Together, this review explores the various venues of CDI research and highlights the importance of integrating microbial, host, and clinical data to help clinicians make optimal treatment decisions based on accurate prediction of disease progression.

Clostridium difficile -Associated Disease in Long-Term Care Facilities

Clostridium difficile is a major cause of gastrointestinal infections. In 1978, Bartlett and colleagues identified C difficile and its toxin as the cause of the antibiotic-associated pseudomembranous colitis (PMC). Within a few years, there was the development of a diagnostic assay, a description of a clinical and pathological spectrum of the disease, a definition of risk factors and characterization of the two toxins that account for the pathological event. Additional information regarding the microbiology, pathogenesis, clinical manifestations, diagnosis and treatment has rapidly developed. These features are beyond the scope of this report, and the reader is referred to several recent reviews.

Risk Factors for Clostridium difficile Toxin-Associated Diarrhea

The hospital-wide attack rate for Clostridium difficile-associated diarrhea at our tertiary-care university hospital was 0.02 per 100 patient discharges (0.02%) in 1982, but 0.41% and 1.47% in 1986 and 1987, respectively, with a peak incidence of 2.25% in the fourth quarter of 1987. Hospital antibiotic usage patterns showed concurrent increased use of third-generation cephalosporins, and intravenous vancomycin and metronidazole. Thirty-seven cases selected for study were older than 37 control patients, more likely to have an underlying malignancy and less likely hospitalized on the obstetrics/gynecology service. Their mean duration of hospitalization prior to diagnosis was 21 days, versus a mean total length of stay of eight days for controls. All cases received antibiotics, compared to 24 of the controls. Cases were given more antibiotics for longer periods, and more often received clindamycin, third-generation cephalosporins, aminoglycosides and vancomycin. Gender, race, duration of hospitalization, prior surgery and antiulcer therapy were not significant by logistic regression analysis. Epidemiologic variables with significantly different adjusted odds ratios (95% confidence intervals) were age greater than 65 years (14.1, 1.4-141), intensive care unit residence (39.2, 2.2-713), gastrointestinal procedure (23.2, 2.1-255) and more than ten antibiotic days (summation of days of each antibiotic administered) (16.1, 2.2-117). Control measures included encouraging earlier isolation and treatment of suspected cases and formulary restriction of clindamycin, with use of metronidazole for therapy of anaerobic infections. By the second half of 1988, the attack rate had dropped progressively to 0.74%.

Acid suppression therapy does not predispose to Clostridium difficile infection: the case of the potential bias

Objective

An adverse effect of acid-suppression medications on the occurrence of Clostridium difficile infection (CDI) has been a common finding of many, but not all studies. We hypothesized that association between acid-suppression medications and CDI is due to the residual confounding in comparison between patients with infection to those without, predominantly from non-tested and less sick subjects. We aimed to evaluate the effect of acid suppression therapy on incidence of CDI by comparing patients with CDI to two control groups: not tested patients and patients suspected of having CDI, but with a negative test.

Methods

We conducted a case-control study of adult patients hospitalized in internal medicine department of tertiary teaching hospital between 2005–2010 for at least three days. Controls from each of two groups (negative for CDI and non-tested) were individually matched (1∶1) to cases by primary diagnosis, Charlson comorbidity index, year of hospitalization and gender. Primary outcomes were diagnoses of International Classification of Diseases (ICD-9)–coded CDI occurring 72 hours or more after admission.

Results

Patients with CDI were similar to controls with a negative test, while controls without CDI testing had lower clinical severity. In multivariable analysis, treatment by acid suppression medications was associated with CDI compared to those who were not tested (OR = 1.88, p-value = 0.032). Conversely, use of acid suppression medications in those who tested negative for the infection was not associated with CDI risk as compared to the cases (OR = 0.66; p = 0.059).

Conclusions

These findings suggest that the reported epidemiologic associations between use of acid suppression medications and CDI risk may be spurious. The control group choice has an important impact on the results. Clinical differences between the patients with CDI and those not tested and not suspected of having the infection may explain the different conclusions regarding the acid suppression effect on CDI risk.

Drug risk factors associated with a sustained outbreak of Clostridium difficile diarrhea in a teaching hospital

A case-control study was undertaken to identify and quantify antimicrobial and nonantimicrobial drug risk factors associated with a sustained outbreak of Clostridium difficile diarrhea on two medical (teaching and nonteaching) units and an oncology unit. In total, 80 cases associated with an endemic clone of toxigenic C difficile were compared with controls. Eighty controls were selected from a group of 290 controls randomly chosen from the outbreak period. The controls were matched to cases according to age, admitting diagnosis and unit of admission. Seventy (88%) patients in the case group received at least one antibiotic before diarrhea, compared with 37 (46%) patients in the control group. Major risk factors implicated in the development of C difficile diarrhea in hospitalized patients were the following antimicrobial agents: ceftazidime (adjusted odds ratio [aor]=26.01, 95% ci 5.67 to 119.19, P=0.0001); cefuroxime (aor=5.17, ci 1.86 to 14.36, P=0.005); ciprofloxacin (aor=3.81, ci 1.05 to 13.79, P=0.04); and clindamycin (aor=15.16, ci 2.93 to 78.44, P=0.004). This is the first time that the use of ciprofloxacin has been linked to the development of C difficile diarrhea. Use of gastrointestinal drugs (ranitidine, famotidine, cimetidine, omeprazole and sucralfate) was also an added risk (aor=3.20, ci 1.39 to 7.34, P=0.01); however, antineoplastic therapy was not significant (P<0.53). Recognition of the specific high risk drugs may spur more restricted use of these agents, which may help in controlling C difficile diarrhea in hospitalized patients.

Clostridium difficile-associated diarrhea in a tertiary care medical center

This retrospective, case-control study aimed to identify variables associated with the incidence of Clostridium difficile-associated diarrhea (CDAD) in acute care facilities and to specifically identify the relationship of fluoroquinolones and acid suppressive agents in the development of CDAD. Seventy-one symptomatic patients positive for C. difficile toxin A or B hospitalized for at least 72 hours were compared with 142 control patients hospitalized for at least 72 hours who were not positive for C. difficile toxin A or B. Two controls were matched to one case patient for age within 5 years, unit of admission, and date of admission. The mean ages for cases and controls were 63.5 and 62.7 years, respectively. After adjusting for two confounding variables-hospital stay within 3 months and Charlson Comorbidity Index-conditional multiple logistic regression identified six risk factors for development of CDAD: gastrointestinal procedures within 60 days (odds ratio [OR] 9.1, P < 0.013), levofloxacin exposure (OR 8.2, P < 0.033), moxifloxacin exposure (OR 4.1, P < 0.026), imipenem exposure (OR 14.9, P < 0.014), laxative use (OR 20.2, P < 0.0001), and immunosuppressive use (OR 20.7, P < 0.034). The risk of CDAD after exposure to levofloxacin or moxifloxacin was not significantly different. Acid suppressive therapy was not a risk factor for CDAD development.

Clostridium difficile infection rates and spectrum of disease among peripartum women at one hospital from 2003 to 2007 with molecular typing analysis of recovered Clostridium difficile isolates

BACKGROUND

Peripartum women are at risk for Clostridium difficile infection (CDI), but the risk magnitude and clinical disease spectrum are unknown. We determined the incidence and clinical features of CDI in peripartum women in the Loyola University Medical Center system and describe typing of C difficile isolates by restriction endonuclease analysis (REA).

METHODS

A retrospective chart review of peripartum CDI from 2003 to 2007 was performed after identifying patients from the clinical laboratory log of positive C difficile toxin assays. Available stool samples were cultured and isolates typed using REA.

RESULTS

We found 12 CDI cases over 5 years for an incidence of 0.7 cases/1,000 obstetrics ward admissions. Prior antibiotic use was documented in 11 (92%) cases, and 8 (67%) were health care facility associated. The rate of CDI following cesarean section was 2.2 per 1,000 live births compared with 0.2 per 1,000 following vaginal delivery (relative risk, 11.6; 95% confidence interval: 1.39-96.23). Typing revealed 4 different REA strain groups; 6 of the 7 REA types were toxin variants.

CONCLUSION

CDI in peripartum women is similar to CDI in other groups except for age. CDI was caused by multiple REA types. Cesarean section may be a particular risk for CDI that develops in the postpartum period.

Case-control analysis of clostridium difficile-associated diarrhea on a gynecologic oncology service

Objective: The incidence, morbidity, and risk factors associated with Clostridium difficile-associated diarrhea (CDAD) were studied in a group of gynecologic oncology patients.

Methods: A case-control analysis of gynecologic oncology patients with CDAD was carried out from August 1986 through January 1989 in a university medical center.

Results: One hundred twenty-three stool samples were tested for C. difficile using the CDT latex agglutination test (Marion Diagnostics, Kansas City, MO). Thirty episodes of CDAD developed in 23 patients. From August 1986 through July 1988, the incidence was stable at 1.5 episodes/100 admissions. From August 1988 through January 1989, the incidence increased to 9.9 episodes/100 admissions (P = 0.005). Compared with patients with nonspecific antibiotic-associated diarrhea, the study patients were hospitalized longer prior to the development of symptoms (mean 15.2 vs. 9.2 days, P = 0.006) and were admitted more frequently with diarrhea (37% vs. 11%, P = 0.015). The rates of surgery, chemotherapy, and radiation therapy were similar. Fever (57% vs. 14%, P < 0.001), abdominal pain (40% vs. 6%, P < 0.001), bloody stools (27% vs. 3%, P = 0.006), and leukocytosis (64% vs. 26%, P = 0.011) were more common among the study cases. The duration, indication, and number of antibiotics administered were similar, though once started, the mean time to symptoms was longer in the study cases (13.7 vs. 6.1 days, P = 0.004). Seven relapses, 1 death, and 1 unplanned colostomy occurred among women with CDAD.

Conclusions: C. difficile is a serious cause of nosocomial morbidity in gynecologic oncology patients. Diarrhea developing after antibiotic exposure is more likely to be associated with C. difficile in patients whose symptoms develop several days after completing antibiotics and in patients with a history of CDAD.

Patterns of antibiotic use and risk of hospital admission because of Clostridium difficile infection

BACKGROUND

Previous observations have indicated that infection with Clostridium difficile occurs almost exclusively after exposure to antibiotics, but more recent observations have suggested that prior antibiotic exposure may be less frequent among cases of community-acquired disease.

METHODS

We used 2 linked health databases to perform a matched, nested case-control study of elderly patients admitted to hospital with community-acquired C. difficile infection. For each of 836 cases among people 65 years of age or older, we selected 10 controls. We determined the proportion of cases that occurred without prior antibiotic exposure and estimated the risk related to exposure to different antibiotics and the duration of increased risk.

RESULTS

Of the 836 cases, 442 (52.9%) had no exposure to antibiotics in the 45-day period before the index date, and 382 (45.7%) had no exposure in the 90-day period before the index date. Antibiotic exposure was associated with a rate ratio (RR) of 10.6 (95% confidence interval [CI] 8.9-12.8). Clindamycin (RR 31.8, 95% CI 17.6-57.6), cephalosporins (RR 14.9, 95% CI 10.9-20.3) and gatifloxacin (RR 16.7, 95% CI 8.3-33.6) were associated with the highest risk. The RR for C. difficile infection associated with antibiotic exposure declined from 15.4 (95% CI 12.2-19.3) by about 20 days after exposure to 3.2 (95% CI 2.0-5.0) after 45 days. Use of a proton pump inhibitor was associated with increased risk (RR 1.6, 95% CI 1.3-2.0), as were concurrent diagnoses of inflammatory bowel disease (RR 4.1, 95% CI 2.6-6.6), irritable bowel syndrome (RR 3.4, 95% CI 2.3-5.0) and renal failure (RR 1.7, 95% CI 1.2-2.2).

INTERPRETATION

Community-acquired C. difficile infection occurred in a substantial proportion of individuals with no recent exposure to antibiotics. Among patients who had been exposed to antibiotics, the risk declined markedly by 45 days after discontinuation of use.

Patterns of antibiotic use and risk of hospital admission because of Clostridium difficile infection

BACKGROUND

Previous observations have indicated that infection with Clostridium difficile occurs almost exclusively after exposure to antibiotics, but more recent observations have suggested that prior antibiotic exposure may be less frequent among cases of community-acquired disease.

METHODS

We used 2 linked health databases to perform a matched, nested case-control study of elderly patients admitted to hospital with community-acquired C. difficile infection. For each of 836 cases among people 65 years of age or older, we selected 10 controls. We determined the proportion of cases that occurred without prior antibiotic exposure and estimated the risk related to exposure to different antibiotics and the duration of increased risk.

RESULTS

Of the 836 cases, 442 (52.9%) had no exposure to antibiotics in the 45-day period before the index date, and 382 (45.7%) had no exposure in the 90-day period before the index date. Antibiotic exposure was associated with a rate ratio (RR) of 10.6 (95% confidence interval [CI] 8.9-12.8). Clindamycin (RR 31.8, 95% CI 17.6-57.6), cephalosporins (RR 14.9, 95% CI 10.9-20.3) and gatifloxacin (RR 16.7, 95% CI 8.3-33.6) were associated with the highest risk. The RR for C. difficile infection associated with antibiotic exposure declined from 15.4 (95% CI 12.2-19.3) by about 20 days after exposure to 3.2 (95% CI 2.0-5.0) after 45 days. Use of a proton pump inhibitor was associated with increased risk (RR 1.6, 95% CI 1.3-2.0), as were concurrent diagnoses of inflammatory bowel disease (RR 4.1, 95% CI 2.6-6.6), irritable bowel syndrome (RR 3.4, 95% CI 2.3-5.0) and renal failure (RR 1.7, 95% CI 1.2-2.2).

INTERPRETATION

Community-acquired C. difficile infection occurred in a substantial proportion of individuals with no recent exposure to antibiotics. Among patients who had been exposed to antibiotics, the risk declined markedly by 45 days after discontinuation of use.

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.

Clostridium difficile-associated disease in Oregon: increasing incidence and hospital-level risk factors

BACKGROUND

The incidence of Clostridium difficile-associated disease (CDAD) appears to be increasing. Population-based estimates of disease have been limited, and analyses of hospital-level risk factors for CDAD are lacking. We sought to determine the incidence and trends of CDAD in Oregon and to identify hospital-level factors associated with increases in disease.

METHODS

We analyzed hospital discharge data to calculate the incidence and to describe trends of CDAD in Oregon from 1995 through 2002. We administered questionnaires to hospital laboratory directors, infection control practitioners, and pharmacists to determine the status of laboratory, infection control, and pharmacy policies over time.

RESULTS

The overall incidence of CDAD in Oregon was 3.5 case patients per 10,000 residents in 2002. Incidence increased from 1.4 to 3.3 cases per 1,000 hospital discharges from 1995 to 2002. Rates of disease increased most in hospitals with licensed bed capacity of more than 250 beds and more than 5 intensive care unit beds. Few laboratories, infection control practitioners, and pharmacists were able to identify changes in specific policies over the study period.

CONCLUSIONS

This is the first study to determine a statewide population-based incidence of CDAD. Incidence of CDAD in Oregon has more than doubled over the past decade; larger hospitals experienced the greatest increase in disease rates. We did not identify hospital-level policies that could explain the increase. A study of patients with CDAD at the hospitals with the largest increases is underway to further identify risk factors.

Characterization of Clostridium difficile isolates from foals with diarrhea: 28 cases (1993-1997)

OBJECTIVE

To determine molecular characteristics of Clostridium difficile isolates from foals with diarrhea and identify clinical abnormalities in affected foals.

DESIGN

Retrospective study.

ANIMALS

28 foals with C difficile-associated diarrhea.

PROCEDURE

Toxigenicity, molecular fingerprinting, and antibiotic susceptibility patterns were determined. Information on signalment, clinical findings, results of clinicopathologic testing, whether antimicrobials had been administered prior to development of diarrhea, and outcome was obtained from the medical records.

RESULTS

Twenty-three (82%) foals survived. Toxin A and B gene sequences were detected in isolates from 24 of 27 foals, whereas the toxin B gene alone was detected in the isolate from 1 foal. Results of an ELISA for toxin A were positive for fecal samples from only 8 of 20 (40%) foals. Ten of 23 (43%) isolates were resistant to metronidazole. Molecular fingerprinting revealed marked heterogeneity among isolates, except for the metronidazole-resistant isolates. Sixteen foals had tachypnea. Hematologic abnormalities were indicative of inflammation. Common serum biochemical abnormalities included metabolic acidosis, hyponatremia, hypocalcemia, azotemia, hypoproteinemia, hyperglycemia, and high enzyme activities. Passive transfer of maternal antibodies was adequate in all 12 foals evaluated.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that a large percentage of C difficile isolates from foals with diarrhea will have the toxin A and B gene sequences. Because of the possibility that isolates will be resistant to metronidazole, susceptibility testing is warranted. Clostridium difficile isolates from foals may have a substantial amount of molecular heterogeneity. Clinical and hematologic findings in affected foals are similar to those for foals with diarrhea caused by other pathogens.

Medical diagnoses and procedures associated with clostridium difficile colitis

OBJECTIVES

The aim of this study was to examine the associations of Clostridium difficile colitis with other comorbid conditions and procedural interventions among hospitalized patients.

METHODS

The Patient Treatment File of the Department of Veterans Affairs contains the computerized records of all inpatients treated in 172 Veterans Affairs hospitals distributed throughout the United States. The computerized medical records of 15,091 cases with C. difficile colitis and 61,931 controls without the diagnosis were extracted from the annual files between 1993 and 1998. In a multivariable logistic regression, the occurrence of C. difficile colitis served as outcome variable, whereas the occurrences of other diagnoses or procedures served as predictor variables.

RESULTS

The total numbers of diagnoses in the case and control group were 136,840 and 465,972, respectively. The numbers of procedures were 75,479 and 129,612, respectively. C. difficile colitis was significantly associated with HIV infection, candidiasis, malignant neoplasm and chemotherapy, malnutrition, pneumonia, aspiration pneumonitis, intestinal obstruction, diverticulitis, renal failure, urinary tract infection, decubitus, and osteomyelitis. Interventional procedures involving the respiratory tract, bone marrow biopsy, arterial and venous catheterization, urinary catheterization, dialysis, gastrostomy tube, and physical therapy were also frequently associated with the development of C. difficile colitis.

CONCLUSIONS

These associations reflect the influence of causal relationships (such as the use of antibiotics and chemotherapy), an increased risk of exposure to C. difficile among immobilized bedridden patients with chronic disease states, or a general system failure in patients with end-stage disease. Knowledge of such associations could help to alert physicians to an increased risk of C. difficile colitis among particular groups of susceptible patients.

Environmental control to reduce transmission of Clostridium difficile

Restrictive antibiotic policies and infection control measures have been shown to reduce the incidence of Clostridium difficile-associated diarrhea (CDAD) among hospitalized patients. To date, the role of environmental disinfectants in reducing nosocomial CDAD rates has not been well studied. In a before-and-after intervention study, patients in 3 units were evaluated to determine if unbuffered 1:10 hypochlorite solution is effective as an environmental disinfectant in reducing the incidence of CDAD. Among 4252 patients, the incidence rate of CDAD for bone marrow transplant patients decreased significantly, from 8.6 to 3.3 cases per 1000 patient-days (hazard ratio, 0.37; 95% confidence interval, 0.19-0.74), after the environmental disinfectant was switched from quaternary ammonium to 1:10 hypochlorite solution in the rooms of patients with CDAD. Reverting later to quaternary ammonium solution increased the CDAD rate to 8.1 cases per 1000 patient-days. No reduction in CDAD rates was seen among neurosurgical intensive care unit and general medicine patients, for whom baseline rates were 3.0 and 1.3 cases per 1000 patient-days, respectively. Unbuffered 1:10 hypochlorite solution is effective in decreasing patients' risk of developing CDAD in areas where CDAD is highly endemic. Presumed mechanisms include reducing the environmental burden and the potential for C. difficile transmission among susceptible patients.

Local and systemic neutralizing antibody responses induced by intranasal immunization with the nontoxic binding domain of toxin A from Clostridium difficile

Fourteen of the 38 C-terminal repeats from Clostridium difficile toxin A (14CDTA) were cloned and expressed either with an N-terminal polyhistidine tag (14CDTA-HIS) or fused to the nontoxic binding domain from tetanus toxin (14CDTA-TETC). The recombinant proteins were successfully purified by bovine thyroglobulin affinity chromatography. Both C. difficile toxin A fusion proteins bound to known toxin A ligands present on the surface of rabbit erythrocytes. Intranasal immunization of BALB/c mice with three separate 10-microg doses of 14CDTA-HIS or -TETC generated significant levels of anti-toxin A serum antibodies compared to control animals. The coadministration of the mucosal adjuvant heat labile toxin (LT) from Escherichia coli (1 microg) significantly increased the anti-toxin A response in the serum and at the mucosal surface. Importantly, the local and systemic antibodies generated neutralized toxin A cytotoxicity. Impressive systemic and mucosal anti-toxin A responses were also seen following coadministration of 14CDTA-TETC with LTR72, an LT derivative with reduced toxicity which shows potential as a mucosal adjuvant for humans.

Immunogenicity of a Salmonella typhimurium aroA aroD vaccine expressing a nontoxic domain of Clostridium difficile toxin A

The C-terminal repeat domain of Clostridium difficile toxin A harbors toxin-neutralizing epitopes and is considered to be a candidate component of a vaccine against C. difficile-associated disease (CDAD). Fourteen of the 38 C-terminal toxin A repeats (14CDTA) were cloned into pTECH-1 in frame with the immunogenic fragment C of tetanus toxin (TETC) to generate plasmid p56TETC. Expression of the TETC-14CDTA fusion protein was driven from the anaerobically inducible nirB promoter within attenuated Salmonella typhimurium BRD509 (aroA aroD). The TETC-14CDTA fusion protein was purified and shown to bind to known toxin A receptors found on the surface of rabbit erythrocytes. Intranasal (i.n.) and intragastric (i.g.) immunization with 10(7) and 10(10) CFU, respectively, of BRD509(p56TETC) generated significant (P < 0.05) anti-toxin A serum responses after a single dose. Antibody titers were elevated following a boosting dose with either live vaccine or a subcutaneous injection of 0.5 microgram of purified 14CDTA protein. Importantly, serum from mice immunized with BRD509(p56TETC) neutralized toxin A cytotoxicity. Both i.n. and i.g. immunizations also generated toxin A-specific immunoglobulin A on the pulmonary and intestinal mucosa, respectively. Intranasal vaccination induced consistently higher serum and mucosal anti-toxin A antibody responses. Significant anti-tetanus toxoid serum and mucosal antibodies were also generated by both immunization routes. The availability of live attenuated Salmonella typhi for human use may allow the development of a multivalent mucosal vaccine against CDAD, tetanus, and typhoid.

Risk factors for Clostridium difficile infection

A systematic review of the literature to identify risk factors associated with Clostridium difficile infection was conducted. Two main outcomes were considered: C. difficile diarrhoea and C. difficile carriage. A qualitative assessment, based on a set of defined and consistently applied criteria, appeared to be the best approach for risk factors other than antibiotic use, as an approach based on meta-analysis would have utilized only the information provided by a minority of the studies. Risk factors for which there was evidence suggestive or consistent with an association with C. difficile diarrhoea were: increasing age (excluding infancy), severity of underlying diseases, non-surgical gastrointestinal procedures, presence of a nasogastric tube, anti-ulcer medications, stay on ITU, duration of hospital stay, duration of antibiotic course, administration of multiple antibiotics. For malignant haematological disorders there was evidence of an association only with C. difficile carriage, but there were no suitable studies to explore a possible association of this risk factor with symptomatic infection. Antibiotic use lent itself to quantitative assessment with meta-analysis using logistic regression. Exposure to an antibiotic was shown to be statistically significantly associated with both C. difficile diarrhoea and C. difficile carriage. The meta-analysis approach enabled the ranking of individual antibiotics in relation to the risk of C. difficile infection, though the 95% confidence intervals were often wide and overlapping. Antibiotics associated with a lower risk of C. difficile diarrhoea should be considered, especially when attempting to control a C. difficile outbreak or when prescribing for a patient with other C. difficile risk factors. This systematic review of the literature enabled the identification of features it would be desirable to consider in future epidemiological studies.

Determination and validation of a predictive model for Clostridium difficile diarrhea in hospitalized oncology patients

BACKGROUND

Clostridium difficile colitis in the cancer patient receiving chemotherapy is a frequent cause of morbidity which may prolong hospitalization. Techniques for identifying infection often delay the initiation of therapy.

PATIENTS AND METHODS

In this retrospective case-control analysis, we identified predictors for C. difficile-associated diarrhea in 29 patients hospitalized from 1988 to 1993 on a hematologic malignancy/bone marrow transplant unit (hospital A). We then validated our model with 58 C. difficile cases and 74 controls admitted to an oncology unit from a different institution (hospital B).

RESULTS

We found that low intensity of chemotherapy (P < 0.001), lack of parenteral vancomycin use (P = 0.03) and hospitalization within the past two months (P = 0.05) were independently predictive of C. difficile colitis by multivariate analysis. These variables were weighted for predictive capability using a receiver operator characteristic score; low intensity chemotherapy was assigned two points, lack of parenteral vancomycin received one point and prior hospitalization one point (P < 0.001 by chi 2 for trend). The receiver operating characteristic (ROC) curve areas were 0.78 for patients at hospital A and 0.70 at hospital B indicating moderate drop off in discrimination. Compared to hospital A patients, hospital B patients hospitalized between 1989 and 1994 were more often women (P = 0.04), received less systemic vancomycin (P = 0.01), were less frequently neutropenic (P < 0.05), and received less intense chemotherapy regimens (P < 0.05). Despite these differences in demographics in patients between these institutions, our predictive model was validated in hospital B patients (P = 0.02 by chi 2 for trend).

CONCLUSIONS

The results of this study may help clinicians predict the risk of C. difficile disease in the hospitalized immunocompromised oncology patient and may help guide empiric therapy while awaiting results of stool toxin assays.

The impact of Clostridium difficile on a surgical service: a prospective study of 374 patients

OBJECTIVE

To evaluate the epidemiology of Clostridium difficile colitis (CDC) in a subset of patients admitted specifically to a surgical service.

SUMMARY BACKGROUND DATA

CDC is an increasingly prevalent nosocomial infection that can prolong hospitalization and adversely affect patient outcome. Although this disease has been investigated extensively in patients admitted to medical services, the incidence and risk factors for the development of this disease in patients admitted to a surgical service have not been studied.

METHODS

Over a 5-month period, 374 patients admitted to the general, vascular, thoracic, and urologic surgery services were monitored for the development of symptomatic CDC (defined as >3 bowel movements per 24 hours and a positive cytotoxin assay or culture).

RESULTS

Twenty-one patients developed CDC (incidence, 5.6%). Factors that independently predisposed to infection included admission from a skilled care facility, use of the antibiotic cefoxitin, and an operative procedure for bowel obstruction. Other factors associated with CDC included colectomy, treatment with any antibiotic, nasogastric tube suction, advanced age, and prior antibiotic treatment. Abdominal pain and fever were also more common in patients with CDC. Morbidity included prolonged hospitalization in all patients and urgent colectomy in one.

CONCLUSIONS

CDC frequently affects surgical patients, producing morbidity ranging from mild diarrhea to life-threatening illness. A variety of factors, many of which are associated with intestinal stasis, predispose to the development of CDC.

Clostridium difficile-associated diarrhea: epidemiology, risk factors, and infection control

OBJECTIVES

To evaluate the effectiveness of specific infection control measures on the incidence of Clostridium difficile-associated diarrhea (CDAD) and to identify risk factors for its development.

SETTING

370-bed, tertiary-care teaching hospital with approximately 12,000 to 15,000 admissions per year.

METHODS

Several infection control measures were implemented in 1991 and 1992, and the attack rates of CDAD were calculated quarterly. Antibiotic use for 1988 through 1993 was analyzed. A case-control study was conducted from January 1992 to December 1992 to identify risk factors for acquisition of CDAD.

RESULTS

From 1989 to 1992, the attack rate of CDAD increased from 0.49% to 2.25%. An increase in antibiotic use preceded the rise in the incidence of CDAD in 1991. Despite implementation of various infection control measures, the attack rate decreased to 1.32% in 1993, but did not return to baseline. Ninety-two cases and 78 controls (patients with diarrhea but with negative toxin assay) were studied. By univariate analysis, history of prior respiratory tract infections (odds ratio [OR], 3.6; 95% confidence interval [CI95], 1.2-10.4), the number of antibiotics, and the duration of exposure to second-generation cephalosporins (OR, 3.55; CI95, 1.47-9.41) and to ciprofloxacin (OR, 7.27; CI95, 1.13-166.0) were related significantly to the development of CDAD. By stepwise logistic regression analysis, only exposure to antibiotics and prior respiratory tract infections (P = .0001 and .0203, respectively) were found to be significant.

CONCLUSION

Antibiotic pressure might have contributed to failure of infection control measures to reduce the incidence of CDAD to baseline.

Pseudomembranous panenteritis and septicaemia in a patient with ulcerative colitis

Pseudomembranous colitis may occur in the immunocompromised chronic colitic patient without a prior history of antibiotic use. The entire gastrointestinal tract can be involved and the presentation can be that of a severe systemic infection that warrants prompt recognition and aggressive management.

Use of pulsed-field gel electrophoresis for investigation of an outbreak of Clostridium difficile infection among geriatric patients

A six-month outbreak of Clostridium difficile infection among elderly residents of a middle-term-care facility was investigated. Pulsed-field gel electrophoresis was used to genotype 22 outbreak strains and 30 epidemiologically unrelated strains. A prospective case-control study was conducted to identify risk factors for epidemic Clostridium difficile-associated diarrhea. All epidemiologically unrelated Clostridium difficile strains of the same serogroup could be differentiated by their DNA patterns with two restriction enzymes (SmaI and KspI). Among clustered strains, two epidemic serogroups (C and K) were identified. Two different DNA patterns were identified among serogroup C strains and three among serogroup K strains. Multivariate analysis showed that the risk of Clostridium difficile infection increased with antimicrobial chemotherapy (beta-lactam agents and pristinamycin) and the presence of a feeding tube. This study confirms the high discriminative power of restriction fragment length polymorphism analysis by pulsed-field gel electrophoresis to describe Clostridium difficile epidemiology. The typing results confirm that infection was principally exogenous in this outbreak. Furthermore, they indicate the need to improve all measures limiting transmission of infection.

Clindamycin and metronidazole

Metronidazole is a bactericidal antibiotic with strong activity against most anaerobes and certain parasites. The drug has excellent bioavailability and good penetration in most tissues, including the cerebrospinal fluid and brain abscess contents. It is usually well tolerated with few side effects. With a few exceptions, the percentage of anaerobes, including B. fragilis group, that are resistant to metronidazole remains low. Metronidazole has been used extensively in clinical practice for years, and its uses have expanded. Its exact role in the management of Crohn's disease and entities related to H. pylori is evolving.

Clostridium difficile: clinical disease and diagnosis

Clostridium difficile is an opportunistic pathogen that causes a spectrum of disease ranging from antibiotic-associated diarrhea to pseudomembranous colitis. Although the disease was first described in 1893, the etiologic agent was not isolated and identified until 1978. Since clinical and pathological features of C. difficile-associated disease are not easily distinguished from those of other gastrointestinal diseases, including ulcerative colitis, chronic inflammatory bowel disease, and Crohn's disease, diagnostic methods have relied on either isolation and identification of the microorganism or direct detection of bacterial antigens or toxins in stool specimens. The current review focuses on the sensitivity, specificity, and practical use of several diagnostic tests, including methods for culture of the etiologic agent, cellular cytotoxicity assays, latex agglutination tests, enzyme immunoassay systems, counterimmunoelectrophoresis, fluorescent-antibody assays, and polymerase chain reactions.

Postoperative clostridium difficile gastroenteritis

Clostridium difficile gastroenteritis can be the cause of an enigmatic postoperative syndrome of high temperature and marked leukocytosis, out of proportion to the initially mild constitutional symptoms. Patients may suffer delayed onset of diarrhea, which will test positive for the C. difficile enterotoxin by latex agglutination. We report 5 cases of C. difficile gastroenteritis that occurred within a 2-year period. We believe that the combination of preoperative bowel preparation, and intraoperative and postoperative systemic antibiotics is the primary operant factor. All patients responded rapidly when oral antibiotics specific for C. difficile were instituted. The sequelae of C. difficile colitis can include toxic megacolon with perforation and peritonitis, increasing the importance of early recognition and appropriate treatment.

Epidemiological aspects of infections caused by Bacteroides fragilis and Clostridium difficile

Bacteroides fragilis and Clostridium difficile are two of the most common anaerobes associated with human disease. Studies on the epidemiology of Bacteroides fragilis are limited and are based predominantly on serogrouping, which suggests intraspecies differences. Further studies using newer techniques for typing are required to elucidate the epidemiological characteristics of this important pathogen. By contrast, numerous phenotypic, immunological and molecular methods have been developed for typing and fingerprinting of Clostridium difficile and applied in epidemiological studies to show conclusively that Clostridium difficile is nosocomially acquired and that there is transmission and cross-infection between hospital patients.

Management of bowel dysfunction in children with spinal cord disease or injury by means of the enema continence catheter

Because bowel dysfunction in children with spinal cord impairment is a common and disabling problem that does not have adequate treatment, we evaluated the enema continence catheter developed in Toronto, Canada. Thirty-one children and their families were taught to administer a 20 ml/kg saline enema through this device. The children's bowel functions were evaluated 18 and 20 months after the start of the program. Six of the children dropped out of the study in the first 2 weeks and nine dropped out after between 18 and 30 months. For those remaining in the study, the proportion of continent stools rose from 28% to 94% (p less than 0.01); constipated stools dropped from 55% to 15% (p less than 0.01). Satisfaction with the bowel program increased, and five children were able to switch from diapers to lined underwear. No adverse effects were reported, and the amount of time required for toileting did not increase. Although compliance with the regimen was difficult for some families and its use carries potential risks, we believe that it can provide significant improvement in the bowel care of selected persons with spinal cord impairment.

Acute abdomen as the first presentation of pseudomembranous colitis

Acute abdomen was the presenting manifestation of pseudomembranous colitis in six men who had previously been treated with antibiotics and presented with abdominal distention, pain, fever, and leukocytosis with absent or mild diarrhea. Plain abdominal radiographs revealed megacolon in two, combined small and large bowel dilation in three, with one of them showing volvuluslike pattern, and isolated small bowel ileus in one. Emergency colonoscopy was performed successfully in all patients and revealed pseudomembranes in five and nonspecific colitis in one. All patients had positive latex test results for Clostridium difficile, and two tested positive for cytotoxicity. All patients were treated with IV metronidazole, resulting in resolution of symptoms and abdominal findings. In addition, two patients underwent colonoscopic decompression with improvement. Endoscopically, complete resolution of the pseudomembranes occurred at 4 weeks in all cases. No patient had a recurrence. It is concluded that (a) pseudomembranous colitis may present as abdominal distention mimicking small bowel ileus. Ogilvie's syndrome, volvulus, or ischemia; (b) in such cases, emergency colonoscopy is safe and useful for diagnosis and therapeutic decompression and may obviate the need for surgery; and (c) treatment with IV metronidazole is effective. Colitis due to C. difficile should be considered in the differential diagnosis of acute abdomen in patients previously treated with antibiotics.

Risk factors for the development of Clostridium difficile-associated diarrhea during a hospital outbreak

OBJECTIVE

To evaluate the risk factors associated with a nosocomial outbreak of Clostridium difficile-associated diarrhea.

DESIGN

Case-control study with two control groups.

SETTING

University-affiliated urban hospital.

PATIENTS

A convenience sample of 26 patients was chosen out of a total of 78 hospitalized patients with C difficile-associated diarrhea, defined as the presence of diarrhea and a positive C difficile cytotoxin assay or stool culture. Twenty-six controls were matched for age, gender, ward, and date of admission; 18 additional controls were matched to surgical patients for date and ward of admission, as well as for the type of surgical procedure performed.

RESULTS

Significant risk factors for the development of C difficile-associated diarrhea were gastrointestinal surgery (exposure odds ratio [EOR] = 7.9, p = .004, 95% confidence interval [CI] = 1.9, 35), use of neomycin (EOR = 15.6, p = .012, 95% CI = 1.7, 92), clindamycin (EOR = 15.6, p = .005, 95% CI = 1.7, 92), metronidazole (EOR = 5.7, p = .02, 95% CI = 1.4, 25), and excess antibiotic use (mean number of antibiotics = 4.2 versus 1.4, p less than .00005). The presence of systemic disease and the use of antacids or immunosuppressive drugs were similar in cases and controls. In surgical patients, no specific antibiotic could be linked to C difficile-associated diarrhea because of uniform perioperative antibiotic use. There was a significant difference in the number of antibiotics administered to cases and controls (mean = 3.1 versus 1.9, p less than .005).

CONCLUSIONS

The results suggest that control of nosocomial C difficile-associated diarrhea may be attained by minimizing the administration of antibiotics, avoidance of high-risk antibiotics, and having a high index of suspicion of C difficile-associated diarrhea in patients who develop diarrhea after gastrointestinal surgery. Perioperative administration of metronidazole, when given with other antibiotics, failed to protect against the development of C difficile-associated diarrhea.

Clostridium difficile-associated disease in long-term care facilities

Clostridium difficile is a major cause of gastrointestinal infections. In 1978, Bartlett and colleagues identified C difficile and its toxin as the cause of the antibiotic-associated pseudomembranous colitis (PMC). Within a few years, there was the development of a diagnostic assay, a description of a clinical and pathological spectrum of the disease, a definition of risk factors and characterization of the two toxins that account for the pathological event. Additional information regarding the microbiology, pathogenesis, clinical manifestations, diagnosis and treatment has rapidly developed. These features are beyond the scope of this report, and the reader is referred to several recent reviews.

Nosocomial Clostridium difficile colonisation and disease

To assess the risk of acquiring Clostridium difficile diarrhoea or colitis in patients colonised with C difficile, rectal swabs taken weekly for 9 weeks from patients with long-term (at least 7 days) hospital stays on three wards were cultured for C difficile. 60 (21%) of 282 patients were culture-positive for C difficile during their hospital stay, of whom 51 were symptom-free faecal excretors. C difficile diarrhoea developed in the other 9 patients; 2 were culture-positive for C difficile and had diarrhoea at the time of first culture, and 7 had diarrhoea or pseudomembranous colitis after 1-6 previously negative weekly rectal cultures. All patients with diarrhoea were on one ward, but symptom-free, excretors were found on all wards. HindIII chromosomal restriction endonuclease analysis (REA) of the C difficile isolates revealed 18 distinct types. All isolates from the patients with diarrhoea were one of two nearly identical REA types, B or B2. 26 of the 29 total B/B2 isolates were from patients on the same ward, which points to a nosocomial outbreak. The symptom-free excretors were not at increased risk of subsequent clinical illness.

Quantitative study of antibiotic-induced susceptibility to Clostridium difficile enterocecitis in hamsters

Commonly used antibiotics were compared for their ability to induce Clostridium difficile enterocecitis and death in hamsters. Susceptibility to infection with C. difficile was measured by calculating 50% lethal doses (in CFU) for hamsters for various intervals after antibiotic treatment. Infection occurred after very small doses of C. difficile were given to hamsters treated with clindamycin, ampicillin, flucloxacillin, and cefuroxime; there was little difference between the antibiotics in the degree of susceptibility that they induced. A large difference in the duration of susceptibility was observed, however, with susceptibility being temporary following ampicillin, flucloxacillin, and cefuroxime administration but long-lived following clindamycin administration. A larger dose of ampicillin, multiple doses of ampicillin, and a combination of antibiotics had comparatively small effects on the duration of susceptibility. C. difficile growth and toxin production in in vitro suspensions of cecal contents were found to correlate closely with in vivo hamster infectivity. A persisting loss of colonization resistance following antibiotic treatment may be a type of postantibiotic effect. Although these results cannot be applied directly to humans, they suggest lines of further investigation into how antibiotics may differ in producing risks of C. difficile infection and pseudomembranous colitis in patients.

Risk factors for Clostridium difficile toxin-associated diarrhea

The hospital-wide attack rate for Clostridium difficile-associated diarrhea at our tertiary-care university hospital was 0.02 per 100 patient discharges (0.02%) in 1982, but 0.41% and 1.47% in 1986 and 1987, respectively, with a peak incidence of 2.25% in the fourth quarter of 1987. Hospital antibiotic usage patterns showed concurrent increased use of third-generation cephalosporins, and intravenous vancomycin and metronidazole. Thirty-seven cases selected for study were older than 37 control patients, more likely to have an underlying malignancy and less likely hospitalized on the obstetrics/gynecology service. Their mean duration of hospitalization prior to diagnosis was 21 days, versus a mean total length of stay of eight days for controls. All cases received antibiotics, compared to 24 of the controls. Cases were given more antibiotics for longer periods, and more often received clindamycin, third-generation cephalosporins, aminoglycosides and vancomycin. Gender, race, duration of hospitalization, prior surgery and antiulcer therapy were not significant by logistic regression analysis. Epidemiologic variables with significantly different adjusted odds ratios (95% confidence intervals) were age greater than 65 years (14.1, 1.4-141), intensive care unit residence (39.2, 2.2-713), gastrointestinal procedure (23.2, 2.1-255) and more than ten antibiotic days (summation of days of each antibiotic administered) (16.1, 2.2-117). Control measures included encouraging earlier isolation and treatment of suspected cases and formulary restriction of clindamycin, with use of metronidazole for therapy of anaerobic infections. By the second half of 1988, the attack rate had dropped progressively to 0.74%.

Nosocomial acquisition of Clostridium difficile infection

We studied the acquisition and transmission of Clostridium difficile infection prospectively on a general medical ward by serially culturing rectal-swab specimens from 428 patients admitted over an 11-month period. Immunoblot typing was used to differentiate individual strains of C. difficile. Seven percent of the patients (29) had positive cultures at admission. Eighty-three (21 percent) of the 399 patients with negative cultures acquired C. difficile during their hospitalizations. Of these patients, 52 (63 percent) remained asymptomatic and 31 (37 percent) had diarrhea; none had colitis. Patient-to-patient transmission of C. difficile was evidenced by time-space clustering of incident cases with identical immunoblot types and by significantly more frequent and earlier acquisition of C. difficile among patients exposed to roommates with positive cultures. Of the hospital personnel caring for patients with positive cultures, 59 percent (20) had positive cultures for C. difficile from their hands. The hospital rooms occupied by symptomatic patients (49 percent) as well as those occupied by asymptomatic patients (29 percent) were frequently contaminated. Eighty-two percent of the infected cohort still had positive cultures at hospital discharge, and such patients were significantly more likely to be discharged to a long-term care facility. We conclude that nosocomial C. difficile infection, which was associated with diarrhea in about one third of cases, is frequently transmitted among hospitalized patients and that the organism is often present on the hands of hospital personnel caring for such patients. Effective preventive measures are needed to reduce nosocomial acquisition of C. difficile.

Molecular cloning and genetic analysis of a chloramphenicol acetyltransferase determinant from Clostridium difficile

A gene bank from a clinical isolate of Clostridium difficile expressing high chloramphenicol acetyltransferase activity was constructed by cloning Sau3A-cleaved clostridial DNA fragments into the plasmid vector pUC13. Among 1,020 clones tested, 11 were resistant to chloramphenicol; 1 of these, with an insert size of 1.9 kilobases (pPPM9), was studied further. The clone pPPM9 was mapped using a variety of restriction enzymes, and a 0.27-kilobase EcoRV-TaqI restriction fragment was shown to be within the chloramphenicol resistance (Cmr) gene by using transposon (Tn1000) mutagenesis. The 0.27-kilobase fragment and the 1.9-kilobase insert were radiolabeled and used as DNA probes in hybridization studies. Southern blot analysis with the gene probes against chromosomal DNA from Cmr strains of C. difficile obtained from five distinct geographical locations revealed that at least two copies of the same chloramphenicol acetyltransferase gene were present for each strain. Hybridization of the gene probes against Cmr strains of Staphylococcus epidermidis, Staphylococcus aureus, Klebsiella edwardsii, Escherichia coli, and to four other clostridial species revealed no homology even under conditions of low stringency.

Pancreatic abscess caused by Clostridium difficile

The first known case of pancreatic abscess caused by Clostridium difficile in a patient with no history of diarrhea or previous antibiotic therapy is presented. After surgical intervention and antibiotic therapy with metronidazole (500 mg every 8 h) and cefotaxime (1 g every 8 h) the patient recovered completely.

Gastrointestinal carriage rate of Clostridium difficile in elderly, chronic care hospital patients

The carriage rate of Clostridium difficile in patients at a chronic care hospital was determined by two point prevalence surveys at 6-monthly intervals. In the first survey C. difficile or its toxin was present in stool samples from five symptomless patients on three of the four wards studied. All of these colonized patients had been in hospital for at least 2 months, but there was no relationship between carriage of the organism and antibiotic use. When the survey was repeated 6 months later, no symptomless carriers were found but one symptomatic patient had C. difficile and its toxin present in the stool. The results suggest that C. difficile should always be considered as a possible cause of diarrhoea in long-stay hospitalized patients.

Clostridium difficile as a nosocomial pathogen

Patients admitted to a 19-bed floor with intermediate nursing care were studied for the onset of Clostridium difficile-associated diarrhoea during a six-month period (181 calendar days) in 1986-87. All admitted patients were reviewed weekly and followed after discharge from the study unit to other inpatient services. Multiple items in the environment of five patients' rooms were sampled bacteriologically for the presence of C. difficile weekly during the study period. Three of the rooms were selected for study because of a higher prevalence of C. difficile associated diarrhoea in the prior three years and two were selected because no cases had been discovered previously in these rooms ('control rooms'). Nine of 521 patients admitted to this unit developed C. difficile diarrhoea (1.73 cases/100 patients admitted) versus 0.30/100 patients admitted to all other sites in our hospital (24 of 7970 other patients). This represented respectively 3.91 cases per 1000 patient days on this floor versus 0.37 patients/1000 patient days throughout the hospital. Seven of the C. difficile diarrhoea cases were associated with stay in the C. difficile associated rooms, versus two cases in the two 'control rooms'. C. difficile was isolated from the toilet seats, bedpan hopper, night stands or food trays. Of some 1955 cultures taken, only 1.9% overall were positive for C. difficile.

Clostridium difficile: its disease and toxins

Clostridium difficile is the etiologic agent of pseudomembranous colitis, a severe, sometimes fatal disease that occurs in adults undergoing antimicrobial therapy. The disease, ironically, has been most effectively treated with antibiotics, although some of the newer methods of treatment such as the replacement of the bowel flora may prove more beneficial for patients who continue to relapse with pseudomembranous colitis. The organism produces two potent exotoxins designated toxin A and toxin B. Toxin A is an enterotoxin believed to be responsible for the diarrhea and mucosal tissue damage which occur during the disease. Toxin B is an extremely potent cytotoxin, but its role in the disease has not been as well studied. There appears to be a cascade of events which result in the expression of the activity of these toxins, and these events, ranging from the recognition of a trisaccharide receptor by toxin A to the synergistic action of the toxins and their possible dissemination in the body, are discussed in this review. The advantages and disadvantages of the various assays, including tissue culture assay, enzyme immunoassay, and latex agglutination, currently used in the clinical diagnosis of the disease also are discussed.

Restriction endonuclease DNA analysis of Clostridium difficile

HindIII restriction enzyme digests of genomic DNA from nine distinct strains of Clostridium difficile were undertaken, and the results were related to those of a previously established typing method based on [35S]methionine-labeled protein profiles. Each of the typed strains identified by its protein profile could also be distinguished by its unique DNA digestion pattern. Analysis of strains isolated from 10 patients during a hospital outbreak of antibiotic-associated colitis revealed identical DNA profiles, confirming a single strain as the source of cross-infection. Characterization of isolates from worldwide sources revealed similar digestion patterns within the same strain type. Restriction endonuclease DNA analysis provides a sensitive and useful technique for studying the epidemiology of C. difficile.