Attributable Healthcare Resource Utilization and Costs for Patients With Primary and Recurrent Clostridium difficile Infection in the United States

Healthcare resource utilization and direct medical costs associated with index and recurrent Clostridioides difficile infection: a real-world data analysis

Aims: This study aimed to evaluate all-cause economic outcomes, healthcare resource utilization (HRU), and costs in patients with Clostridioides difficile infection (CDI) and recurrent CDI (rCDI) using commercial claims from a large database representing various healthcare settings.Materials and methods: A retrospective analysis of commercial claims data from the IQVIA PharMetrics Plus database was conducted for patients aged 18-64 years with CDI episodes requiring inpatient stay with CDI diagnosis code or an outpatient medical claim for CDI plus a CDI treatment. Index CDI episodes occurred between 1 January 2010 and 30 June 2017, including only those where patients were observable 6 months before and 12 months after the index episode. Each CDI episode was followed by a 14-d claim-free period. rCDI was defined as another CDI episode within an 8-week window following the claim-free period. HRU, all-cause direct medical costs and time to rCDI were calculated over 12 months and stratified by number of rCDI episodes.Results: A total of 46,571 patients with index CDI were included. Mean time from one CDI episode to the next was approximately 1 month. In the 12-month follow-up period, those with no recurrence had 1.4 inpatient visits per person and those with 3 or more recurrences had 5.8. Most patients with 3 or more recurrences had 2 or more hospital admissions. The mean annual, total all-cause direct medical costs per patient were $71,980 for those with no recurrence and $207,733 for those with 3 or more recurrences.Limitations: The study included individuals 18-64 years only. A stringent definition of rCDI was used, which may have underestimated the incidence of rCDI.Conclusions: CDI and rCDI are associated with substantial healthcare resource utilization and direct medical costs. Timing of recurrences can be predictable, providing a window of opportunity for interventions. Prevention of multiple rCDI appears essential to reduce healthcare costs.

The economic burden of Clostridioides difficile infection in patients with hematological malignancies in the United States: A case-control study

OBJECTIVE

The primary study aim was to describe all direct healthcare costs associated with Clostridioides difficile infection (CDI), both in and out of the hospital, in patients with hematologic malignancies in the United States.

DESIGN

A retrospective analysis was conducted utilizing data from US databases of Truven Health Analytics.

PATIENTS

We analyzed health insurance claims between January 2014 and December 2017 of patients diagnosed with hematological cancer: acute myeloid leukemia (AML), acute lymphoblastic leukemia, Hodgkin's lymphoma, and non-Hodgkin's lymphoma (NHL).

METHODS

Patients with CDI after cancer diagnosis (CDI+, cases) were matched with patients without CDI reported (CDI-, controls). Matched cases and controls were compared to identify the CDI-associated costs in the 90 days following the onset of CDI.

RESULTS

We matched 622 CDI+ patients with 11,111 CDI- patients. NHL (41.7%) and AML (30.9%) were the predominant underlying diseases in the CDI+ groups. During study period, the average time in-hospital of CDI+ patients was 23.1 days longer than for CDI- patients (P < 2×10-16). Overall, CDI onset increased costs of care by an average of US$57,159 per patient (P = 6×10-12), mainly driven by hospital costs.

CONCLUSIONS

This study confirms the significant economic burden associated with CDI in the United States, especially in patients with hematological malignancies. These findings highlight the need for prevention of CDI in this specific patient population.

Perception of quality of life in people experiencing or having experienced a Clostridioides difficile infection: a US population survey

BACKGROUND

Although the incidence, severity and mortality of Clostridioides (Clostridium) difficile infection (CDI) have been increasing, patients' quality of life changes resulting from CDI have not been studied thoroughly. This study aimed at exploring the consequences of CDI on quality of life through patients' perspective.

METHODS

An observational, cross-sectional study involving 350 participants with a self-reported CDI diagnosis was conducted through an online self-administered survey. Participants were grouped into those who had active disease ("Current CDI") and those who had a history of CDI ("Past CDI").

RESULTS

One hundred fifteen participants (33%) reported Current CDI and 235 (67%) reported Past CDI. A large majority of participants admitted that their daily activities were impacted by the infection (93.9% and 64.7% of Current and Past CDI respondents respectively, p < 0.05). Physical and psychological consequences of CDI were experienced by 63.5% and 66.1% of participants with active CDI. Despite the infection being cleared, these consequences were still frequently experienced in Past CDI cohort with similar rates (reported by 73.2% of respondents for both, physical consequences p = 0.08; psychological consequences p = 0.21). After the infection, 56.6% of respondents noted that post-CDI symptoms remained; 40.9% believed they would never get rid of them.

CONCLUSIONS

While the societal burden of CDI is well described in the literature, our study is one of the first aimed at understanding the major burden of CDI on quality of life. Our results highlight the long-lasting nature of CDI and further reinforce the need for enhanced therapeutics in the prevention and treatment of this devastating infection.

Effectiveness and cost-effectiveness of a Clostridium difficile vaccine candidate in a hospital setting

Toxoid vaccines against Clostridium difficile infections (CDI) appear promising in reducing the risk of developing toxin-mediated symptoms. We sought to evaluate the effectiveness and cost-effectiveness of a vaccine candidate in a hospital setting. We developed an agent-based simulation model of nosocomial CDI in a 300-bed hospital. Targeting high-risk patients for vaccination, we estimated the reduction of symptomatic CDI. Using the net reduction of CDI-associated isolation days, we evaluated the vaccine's cost-effectiveness from a healthcare provider perspective over a 2-year period with an average monthly incidence of 5 cases per 10,000 patient-days pre-vaccination. Assuming a vaccine efficacy in the range 60-90%, vaccinating 40% of high-risk patients pre-admission reduced symptomatic CDI by 16.6% (95% CI: 15.2, 17.9). When the vaccine coverage increased to 80%, the reduction of symptomatic CDI was 34.6% (95% CI: 33.7, 35.9). For a willingness to pay (WTP) of CDN$1000 (corresponding to the average costs of case isolation per day), vaccine was cost-effective for vaccination costs per individual (VCPI) up to CDN$111 in the scenario of 40% vaccine coverage. With the same WTP, vaccine was cost-effective for VCPI up to CDN$121 when the vaccine coverage increased to 80%. A significant portion (~80%) of hospital colonization is caused by environmental transmission of C. difficile, which markedly reduced the effectiveness of vaccine below its assumed efficacy. However, due to the number of CDI-associated isolation days averted, vaccination of high-risk patients can be cost-effective depending on the WTP and the VCPI.

Validation of the SHEA/IDSA severity criteria to predict poor outcomes among inpatients and outpatients with Clostridioides difficile infection

OBJECTIVE

To determine whether the Society for Healthcare Epidemiology of America (SHEA) and the Infectious Diseases Society of America (IDSA) Clostridioides difficile infection (CDI) severity criteria adequately predicts poor outcomes.

DESIGN

Retrospective validation study.

SETTING AND PARTICIPANTS

Patients with CDI in the Veterans’ Affairs Health System from January 1, 2006, to December 31, 2016.

METHODS

For the 2010 criteria, patients with leukocytosis or a serum creatinine (SCr) value ≥1.5 times the baseline were classified as severe. For the 2018 criteria, patients with leukocytosis or a SCr value ≥1.5 mg/dL were classified as severe. Poor outcomes were defined as hospital or intensive care admission within 7 days of diagnosis, colectomy within 14 days, or 30-day all-cause mortality; they were modeled as a function of the 2010 and 2018 criteria separately using logistic regression.

RESULTS

We analyzed data from 86,112 episodes of CDI. Severity was unclassifiable in a large proportion of episodes diagnosed in subacute care (2010, 58.8%; 2018, 49.2%). Sensitivity ranged from 0.48 for subacute care using 2010 criteria to 0.73 for acute care using 2018 criteria. Areas under the curve were poor and similar (0.60 for subacute care and 0.57 for acute care) for both versions, but negative predictive values were >0.80.

CONCLUSIONS

Model performances across care settings and criteria versions were generally poor but had reasonably high negative predictive value. Many patients in the subacute-care setting, an increasing fraction of CDI cases, could not be classified. More work is needed to develop criteria to identify patients at risk of poor outcomes.

Risk for Clostridiodes difficile Infection among Older Adults with Cancer

To assess whether risk for Clostridiodes difficile infection (CDI) is higher among older adults with cancer, we conducted a retrospective cohort study with a nested case-control analysis using population-based Surveillance, Epidemiology, and End Results-Medicare linked data for 2011. Among 93,566 Medicare beneficiaries, incident CDI and odds for acquiring CDI were higher among patients with than without cancer. Specifically, risk was significantly higher for those who had liquid tumors and higher for those who had recently diagnosed solid tumors and distant metastasis. These findings were independent of prior healthcare-associated exposure. This population-based assessment can be used to identify targets for prevention of CDI.

Expert opinion on fecal microbiota transplantation for the treatment of Clostridioides difficile infection and beyond

Introduction: Fecal microbiota transplantation (FMT) is a procedure involving transfer of stool from a healthy donor into the intestinal tract of a diseased recipient to restore intestinal microbial composition and functionality. FMT's tremendous success in recurrent and refractory Clostridioides difficile infection (CDI) catalyzed gut microbiota research and opened the door to microbiome-based therapy for various gastrointestinal and other disorders.Areas covered: We used PubMed search engine to identify significant publications in the field of CDI and FMT. Here we present an overview of the current literature on FMT's use for recurrent, non-severe, severe, and fulminant CDI and on promising future application.Expert opinion: FMT as the best tool for treatment of antibiotic-refractory CDI has gained immense popularity over the last decade. The future of gut microbiota-based therapy should include oral formulations that contain well-described ingredients in effective doses, clear mechanism of action, and excellent safety profile.

Incidence and economic burden of Clostridioides difficile infection in Ontario: a retrospective population-based study

BACKGROUND

Understanding the impact of prevention programs on Clostridioides difficile infection rates is important, and decisions on future program changes, including how to use vaccines currently in development, requires a detailed understanding of the epidemiologic features of C. difficile infection. We analyzed Ontario health administrative data to determine incidence rates and medical costs of C. difficile infection, based on whether acquisition and onset occurred in acute care hospitals (ACHs), long-term care facilities or the community.

METHODS

We performed a retrospective analysis using individual-level data from Ontario health databases from Apr. 1, 2005, to Mar. 31, 2015, identifying rates of C. difficile infection requiring hospital admission per 100 000 person-years in adults aged 18 years or more for categories of acquisition and onset. We estimated health care system costs of infection 180 and 365 days after admission by matching patients with C. difficile infection with control patients with similar characteristics.

RESULTS

Over the study period, 33 909 people in Ontario were admitted to hospital with C. difficile infection; 17 272 cases (50.9%) were associated with ACHs. The number of cases per 100 000 person-years ranged from 27.7 in 2009/10 to 37.0 in 2012/13. Annually, the highest incidence of infection was for ACH-associated/ACH-onset. Community-associated infection became more prevalent over time, rising from 19.4% of cases in 2005/06 to 29.2% in 2014/15. Infection costs were mostly due to hospital admission within 180 days after hospital discharge. Infection associated with ACHs had the highest total costs and the largest cost attributable to C. difficile infection (median $38 953 for infected patients v. $13 542 for control patients). Median costs attributable to C. difficile infection were $1051 for that associated with long-term care facilities, $13 249 for community-associated infection and $11 917 for ACH-associated/community-onset infection.

INTERPRETATION

Community-associated C. difficile infection had similar health care cost implications as hospital-associated infection. With rates of community-associated C. difficile infection on the rise, family physicians should be supported to prevent this infection in their patients.

Clostridium difficile intervention timelines for diagnosis, isolation, and treatment

BACKGROUND

Developing timelines of nosocomial Clostridium difficile infection (CDI) is critical to improving control and preventive measures. The objective of this study was to provide data-driven estimates of CDI timelines of diagnosis, isolation, and treatment in a hospital setting.

METHODS

We obtained data for all CDI inpatients with symptoms onset occurring between January 1, 2013, and December 30, 2017, from St Joseph's Healthcare in Hamilton, Canada. We analyzed full empirical distributions of timelines associated with the diagnosis, isolation, and treatment of CDI.

RESULTS

A total of 683 inpatients with CDI symptoms were recorded, of which 243 cases were identified as health care-associated infection (HAI). The mean time intervals between the onset of CDI symptoms after admission and the release of laboratory results were 1.2 days and 1.9 days for the HAI and community-associated infection (CAI) patient groups, respectively. The mean time intervals from symptoms onset to the start of isolation were 1.5 days and 2.6 days for the corresponding patient groups. The initiation of treatment within 2 days of symptoms onset reduced the duration of first isolation (P value < .0001); however, the type of initial antibiotic used for CDI treatment was not associated with the duration of isolation.

CONCLUSIONS

Estimated timelines did not differ (P values > .6) between HAI and CAI patient groups with symptoms onset after admission. These estimates are useful for evaluating the effectiveness of CDI interventions.

Recent developments in the management of recurrent Clostridioides difficile infection

Clostridioides (formerly Clostridium) difficile is responsible for a substantial burden of nosocomial infection. Recurrent C. difficile infection (rCDI) remains a concern due to its high morbidity, mortality, and cost. Despite the updated 2017 IDSA C. difficile treatment guidelines, there remains a lack of well-studied preventive control measures and treatment modalities for rCDI. There are ongoing efforts to develop novel therapies, such as new antibiotics with a lesser impact on gut microbiota and more targeted therapies, such as bacteriotherapy. This mini review highlights key rCDI management updates, preventive measures and ongoing research on novel treatment strategies including bacteriotherapy.

Healthcare resource use and attributable cost of Clostridium difficile infection: a micro-costing analysis comparing first and recurrent episodes

Objectives

Accurate and sufficiently detailed data on the economic burden of Clostridium difficile infection (CDI) are lacking. We performed a micro-costing study to determine the health resource utilization of patients with a first episode of CDI (fCDI) and those with a recurrent episode of CDI (rCDI).

Patients and methods

Forty-five adult and paediatric inpatients with rCDI were matched by age, sex and date of diagnosis with control patients with fCDI. Total length of hospital stay, length of stay in the ICU and several cost parameters differentiated into fixed and variable components were measured and compared across both groups.

Results

The mean total length of stay for rCDI patients was 33 days (95% CI 19-46) compared with 17 days (95% CI 12-21) for fCDI patients; P = 0.0259. ICU length of stay was also longer for rCDI patients than for fCDI patients (mean 2.5 versus 0.7 days). Mean total variable costs for fCDI and rCDI were £2382 (95% CI 1750-3014) and £4683 (95% CI 3051-6311), respectively; P = 0.009. Mean fixed costs for fCDI and rCDI were £10 328 (95% CI 7555-13 101) and £26 438 (95% CI 16 135-36 742), respectively; P = 0.003. Mean total costs for fCDI and rCDI were £12 710 (95% CI 9652-15 769) and £31 121 (95% CI 19 792-42 447), respectively; P < 0.002.

Conclusions

The healthcare resource use and financial burden attributable to CDI is significant. Most excess cost is driven by additional length of hospital stay. These costs may have been underestimated in previous studies that have not accounted for several difficult-to-measure parameters or have used averaged tariff-based estimates.

A Laboratory Medicine Best Practices Systematic Review and Meta-analysis of Nucleic Acid Amplification Tests (NAATs) and Algorithms Including NAATs for the Diagnosis of Clostridioides (Clostridium) difficile in Adults

The evidence base for the optimal laboratory diagnosis of Clostridioides (Clostridium) difficile in adults is currently unresolved due to the uncertain performance characteristics and various combinations of tests. This systematic review evaluates the diagnostic accuracy of laboratory testing algorithms that include nucleic acid amplification tests (NAATs) to detect the presence of C. difficile The systematic review and meta-analysis included eligible studies (those that had PICO [population, intervention, comparison, outcome] elements) that assessed the diagnostic accuracy of NAAT alone or following glutamate dehydrogenase (GDH) enzyme immunoassays (EIAs) or GDH EIAs plus C. difficile toxin EIAs (toxin). The diagnostic yield of NAAT for repeat testing after an initial negative result was also assessed. Two hundred thirty-eight studies met inclusion criteria. Seventy-two of these studies had sufficient data for meta-analysis. The strength of evidence ranged from high to insufficient. The uses of NAAT only, GDH-positive EIA followed by NAAT, and GDH-positive/toxin-negative EIA followed by NAAT are all recommended as American Society for Microbiology (ASM) best practices for the detection of the C. difficile toxin gene or organism. Meta-analysis of published evidence supports the use of testing algorithms that use NAAT alone or in combination with GDH or GDH plus toxin EIA to detect the presence of C. difficile in adults. There is insufficient evidence to recommend against repeat testing of the sample using NAAT after an initial negative result due to a lack of evidence of harm (i.e., financial, length of stay, or delay of treatment) as specified by the Laboratory Medicine Best Practices (LMBP) systematic review method in making such an assessment. Findings from this systematic review provide clarity to diagnostic testing strategies and highlight gaps, such as low numbers of GDH/toxin/PCR studies, in existing evidence on diagnostic performance, which can be used to guide future clinical research studies.

Extended-pulsed fidaxomicin versus vancomycin in patients 60 years and older with Clostridium difficile infection: cost-effectiveness analysis in Spain

The cost of treating Clostridium difficile infection (CDI) in Spain is substantial. Findings from the randomised, controlled, open-label, phase 3b/4 EXTEND study showed that an extended-pulsed fidaxomicin (EPFX) regimen was associated with improved sustained clinical cure and reduced recurrence of CDI versus vancomycin in patients aged 60 years and older. We assessed the cost-effectiveness of EPFX versus vancomycin for the treatment of CDI in patients aged 60 years and older from the perspective of the National Health System (NHS) in Spain. We used a Markov model with six health states and 1-year time horizon. Health resources, their unit costs and utilities were based on published sources. Key efficacy data and transition probabilities were obtained from the EXTEND study and published sources. A panel of Spanish clinical experts validated all model assumptions. In the analysis, 0.638 and 0.594 quality-adjusted life years (QALYs) per patient were obtained with EPFX and vancomycin, respectively, with a gain of 0.044 QALYs with EPFX. The cost per patient treated with EPFX and vancomycin was estimated to be €10,046 and €10,693, respectively, with a saving of €647 per patient treated with EPFX. For willingness-to-pay thresholds of €20,000, €25,000 and €30,000 per QALY gained, the probability that EPFX was the most cost-effective treatment was 99.3%, 99.5% and 99.9%, respectively. According to our economic model and the assumptions based on the Spanish NHS, EPFX is cost-effective compared with vancomycin for the first-line treatment of CDI in patients aged 60 years and older.

Predictors and burden of hospital readmission with recurrent Clostridioides difficile infection: a French nation-wide inception cohort study

To investigate the predictors and burden of hospital readmission with recurrent Clostridioides difficile infection (rCDI) in a large European healthcare system with a low prevalence of hyper-virulent C. difficile clones. We conducted an inception cohort study based on an exhaustive health insurance database and including all survivors of a first hospital stay with CDI over a one-year period (2015) in France. Readmissions with rCDI were defined as a novel hospital stay with CDI within 12 weeks following discharge of the index hospitalization. Risk factors for readmission with rCDI were investigated through multivariate logistic regression analyses. Among the 14,739 survivors of the index hospital stay (females, 57.3%; median age, 74 [58-84] years), 2135 (14.5%) required at least one readmission with rCDI. Independent predictors of readmission were age ≥ 65 years (adjusted odds ratio (aOR), 1.34, 95% confidence interval (CI), 1.21-1.49, P < 0.0001), immunosuppression (aOR, 1.27, 95% CI, 1.15-1.41, P < 0.0001), chronic renal failure (aOR, 1.29, 95% CI, 1.14-1.46, P < 0.0001), and a previous history of CDI (aOR, 2.05, 95% CI, 1.55-2.71, P < 0.0001). The cumulative number of risk factors was independently associated with the hazard of readmission. Mean acute care costs attributable to rCDI were 5619 ± 3594 Euros for readmissions with rCDI as primary diagnosis (mean length of stay, 11.3 ± 10.2 days) and 4851 ± 445 Euros for those with rCDI as secondary diagnosis (mean length of stay, 16.8 ± 18.2 days), for an estimated annual nation-wide cost of 14,946,632 Euros. Hospital readmissions with rCDI are common after an index episode and drive major healthcare expenditures with substantial bed occupancy, strengthening the need for efficient secondary prevention strategies in high-risk patients.

Bezlotoxumab for the prevention of Clostridium difficile infection: a review of current evidence and safety profile

Clostridium difficile infection (CDI) is a leading nosocomial disease estimated to cause nearly half a million cases in the United States annually. Recurrent CDI (rCDI) affects ~25% of patients after completion of standard of care therapy and is associated with substantial health care costs and a negative impact on patient's overall markers of quality of life. Bezlotoxumab is the first of its kind monoclonal antibody directed against C. difficile toxin B and indicated for prevention of rCDI in at-risk patients. For the present review, we assessed English-language studies evaluating the clinical efficacy, safety, and pharmacokinetics of bezlotoxumab in humans. Relevant studies were obtained through PubMed, Embase, Cochrane database library, Web of Science, and clinicaltrials.gov. Overall, bezlotoxumab demonstrated a 40% relative reduction rate (absolute rate reduction of ~10%) and a number needed to treat of 10 patients with a favorable safety profile. Special populations, including the elderly, immunocompromised, and patients with end-stage renal disease were evaluated in post hoc analyses with a similarly favorable reduction in rCDI. This review presents and interprets the most recent safety data and the clinical application of bezlotoxumab, highlighting specific high-risk patient populations.

Bezlotoxumab Is Associated With a Reduction in Cumulative Inpatient-Days: Analysis of the Hospitalization Data From the MODIFY I and II Clinical Trials

Background

Patients with recurrent Clostridium difficile infection (rCDI) are more likely to have a hospital readmission and spend increased time in inpatient settings compared with patients with primary CDI. MODIFY I and II demonstrated that bezlotoxumab significantly reduced rCDI vs placebo. A post hoc within-trial analysis assessed whether bezlotoxumab was associated with a reduction in cumulative inpatient-days.

Methods

Data were pooled from the MODIFY trials to estimate the cumulative hospitalized days summed over the 84-day follow-up period. We adjusted inpatient use data from pooled MODIFY I and II for survival and censoring to estimate 84-day cumulative inpatient-days, overall and for subgroups. Treatment effects were obtained using recycled predictions based on trial protocol and rCDI risk, and 95% confidence intervals were obtained using 1000 bootstrap replicates.

Results

Mean cumulative inpatient-days were greater in the placebo arm (14.1 days) vs the bezlotoxumab arm (12.1 days) in the overall population. The mean difference between treatment groups was 2.1 days (95% confidence interval, –0.4 to –3.7). This was consistent in participants with risk factors for rCDI: age ≥65 years, compromised immunity, severe CDI, prior CDI, and ribotype 027/078/244 infection. As the number of risk factors increased, bezlotoxumab resulted in greater reductions in the number of inpatient-days compared with placebo (difference: –1.2 days, –2.3 days, –2.5 days, and –3.0 days for 0, 1, 2, and ≥3 risk factors, respectively).

Conclusions

Bezlotoxumab was associated with a reduction in cumulative inpatient-days, suggesting that treatment with bezlotoxumab may substantially reduce rCDI-associated health care resource use.

Trial registrations. MODIFY I (MK-3415A-001, NCT01241552) and II (MK-3415A-002, NCT01513239)

Novel Chimeric Protein Vaccines Against Clostridium difficile Infection

Clostridium difficile infection (CDI) is the leading cause of world-wide nosocomial acquired diarrhea in adults. Active vaccination is generally accepted as a logical and cost-effective approach to prevent CDI. In this paper, we have generated two novel chimeric proteins; one designated Tcd169, comprised of the glucosyltransferase domain (GT), the cysteine proteinase domain (CPD), and receptor binding domain (RBD) of TcdB, and the RBD of TcdA; the other designated Tcd169FI, which contains Salmonella typhimurium flagellin (sFliC) and Tcd169. Both proteins were expressed in and purified from Bacillus megaterium. Point mutations were made in the GT (W102A, D288N) and CPD (C698) of TcdB to ensure that Tcd169 and Tcd169FI were atoxic. Immunization with Tcd169 or Tcd169Fl induced protective immunity against TcdA/TcdB challenge through intraperitoneal injection, also provided mice full protection against infection with a hyper-virulent C. difficile strain (BI/NAP1/027). In addition, inclusion of sFlic in the fusion protein (Tcd169Fl) enhanced its protective immunity against toxin challenge, reduced C. difficile numbers in feces from Tcd169Fl-immunized mice infected C. difficile. Our data show that Tcd169 and Tcd169FI fusion proteins may represent alternative vaccine candidates against CDI.

Presence of multiple Clostridium difficile strains at primary infection is associated with development of recurrent disease

Recurrence of Clostridium difficile infection (CDI) places a major burden on the healthcare system. Previous studies have suggested that specific C. difficile strains, or ribotypes, are associated with severe disease and/or recurrence. However, in some patients a new strain is detected in subsequent infections, complicating longitudinal studies focused on strain differences that may contribute to disease outcome. We examined ribotype composition over time in patients who did or did not develop recurrence to examine infection with multiple C. difficile ribotypes (mixed infection), during the course of infection. Using a retrospective patient cohort, we isolated and ribotyped a median of 36 C. difficile colonies from 61 patients (105 total samples) at initial infection, recurrence (a second case of CDI within 15-56 days of initial infection), and reinfection (a second case of CDI after 56 days of initial infection). We observed mixed infection in 78.6% of samples at initial infection in patients who went on to develop recurrence compared to 18.1% of patients who did not, and mixed infection remained associated with subsequent recurrence after adjusting for gender and prior antibiotic exposure (OR 3.5, 95% CI 1.3-9.4, P = .015). In patients who were sampled longitudinally (44 consecutive events in 32 patients), the dominant ribotype changed in 31.8% of consecutive samples and the newly dominant ribotype was not detected in prior samples from that patient. Our results suggest that mixed C. difficile infection is more prevalent than previously demonstrated and potentially a marker of susceptibility to recurrence.