Procalcitonin levels associate with severity of Clostridium difficile infection

Guidelines for the Use of Procalcitonin for Rational Use of Antibiotics

How to cite this article: Khilnani GC, Tiwari P, Zirpe KG, Chaudhary D, Govil D, Dixit S, et al. Guidelines for the Use of Procalcitonin for Rational Use of Antibiotics. Indian J Crit Care Med 2022;26(S2):S77-S94.

Fulminant Clostridioides difficile Infection: A Review of Treatment Options for a Life-Threatening Infection

Fulminant Clostridioides difficile infection (FCDI) encompasses 3 to 5% of all CDI cases with associated mortality rates between 30 and 40%. Major treatment modalities include surgery and medical management with antibiotic and nonantibiotic therapies. However, identification of patients with CDI that will progress to FCDI is difficult and makes it challenging to direct medical management and identify those who may benefit from surgery. Furthermore, since it is difficult to study such a critically ill population, data investigating treatment options are limited. Surgical management with diverting loop ileostomy (LI) instead of a total abdominal colectomy (TAC) with end ileostomy has several appealing advantages, and studies have not consistently demonstrated a clinical benefit with this less-invasive strategy, so both LI and TAC remain acceptable surgical options. Successful medical management of FCDI is complicated by pharmacokinetic changes that occur in critically ill patients, and there is an absence of high-quality studies that included patients with FCDI. Recommendations accordingly include a combination of antibiotics administered via multiple routes to ensure adequate drug concentrations in the colon: intravenous metronidazole, high-dose oral vancomycin, and rectal vancomycin. Although fidaxomicin is now recommended as first-line therapy for non-FCDI, there are limited clinical data to support its use in FCDI. Several nonantibiotic therapies, including fecal microbiota transplantation and intravenous immunoglobulin, have shown success as adjunctive therapies, but they are unlikely to be effective alone. In this review, we aim to summarize diagnosis and treatment options for FCDI.

Serum procalcitonin levels associate with Clostridioides difficile infection in patients with inflammatory bowel disease

BACKGROUND

Clostridioides difficile infection (CDI) is a major cause of morbidity among patients with inflammatory bowel disease (IBD). Diagnostic biomarkers for early detection of CDI are needed in clinical practice. The relationship between serum procalcitonin and CDI in IBD patients has not been investigated so far. Therefore, we aimed to evaluate the usefulness of measuring serum procalcitonin level to detect CDI in patients with the flare of IBD.

METHODS

One hundred twenty patients with IBD were enrolled in this study. Bacterial identification was performed using standard microbiological and molecular methods. The serum procalcitonin levels were measured in all patients. Receiver operating characteristic (ROC) curve analysis was applied to assess the value of procalcitonin for the prediction of CDI among IBD patients.

RESULTS

The median serum procalcitonin level was significantly increased in IBD patients with CDI compared to non-CDI IBD patients (0.69 ng/mL vs 0.32 ng/mL). In univariate analysis, log₁₀ procalcitonin was associated with CDI (OR 2.81, 95% CI 1.54-4.09, P-value < 0.001). Procalcitonin 1.1 ng/mL was 85% sensitive and 88% specific for the prediction of CDI. In the multivariable model including the covariates log₁₀ procalcitonin, age, hospitalization, type of IBD, duration of the disease, and antibiotic usage, procalcitonin showed a robust association with CDI (OR 4.59, 95% CI 2.49-6.70, P-value < 0.001). An elevated procalcitonin level was associated with the presence of CDI among IBD patients.

CONCLUSIONS

Our results indicate that procalcitonin level can be a good candidate biomarker for assessing the CDI in IBD patients. Further studies are required to decipher whether procalcitonin can predict CDI therapy or its recurrence.

Systematic review on the definition and predictors of severe Clostridiodes difficile infection

Clostridiodes difficile infection (CDI) is one of the most common hospital-acquired infections with high mortality rates. Optimal management of CDI depends on early recognition of severity. However, currently, there is no acceptable standard of prediction. We reviewed severe CDI predictors in published literature and its definition according to clinical guidelines. We systematically reviewed studies describing clinical predictors for severe CDI in medical databases (Cochrane, EMBASE, Global Health Library, and MEDLINE/PubMed). They were independently evaluated by two reviewers. Six hundred thirty-three titles and abstracts were screened, and 31 studies were included. We excluded studies that were restricted to a specific patient population. There were 16 articles that examined mortality in CDI, as compared with 15 articles investigating non-mortality outcomes of CDI. The commonest risk factors identified were comorbidities, white blood cell count, serum albumin level, age, serum creatinine level and intensive care unit admission. Generally, the studies had small patient populations, were retrospective in nature, and mostly from Western centers. The commonest severe CDI criteria in clinical guidelines were raised white blood cell count, followed by low serum albumin and raised serum creatinine levels. There was no commonly agreed upon definition of severe CDI severity in the literature. Current clinical guidelines' definitions for severe CDI are heterogeneous. Hence, there is a need for prospective multi-center studies using standardized protocol for biospecimen investigation collection and shared data on outcomes of patients in order to devise a universally accepted definition for severe CDI.

Systemic Inflammatory Mediators Are Effective Biomarkers for Predicting Adverse Outcomes in Clostridioides difficile Infection

Each year in the United States, Clostridioides difficile causes nearly 500,000 gastrointestinal infections that range from mild diarrhea to severe colitis and death. The ability to identify patients at increased risk for severe disease or mortality at the time of diagnosis of C. difficile infection (CDI) would allow clinicians to effectively allocate disease modifying therapies. In this study, we developed models consisting of only a small number of serum biomarkers that are capable of predicting both 30-day all-cause mortality and adverse outcomes of patients at time of CDI diagnosis. We were able to validate these models through experimental mouse infection. This provides evidence that the biomarkers reflect the underlying pathophysiology and that our mouse model of CDI reflects the pathogenesis of human infection. Predictive models can not only assist clinicians in identifying patients at risk for severe CDI but also be utilized for targeted enrollment in clinical trials aimed at reduction of adverse outcomes from severe CDI.

Clostridioides difficile infection (CDI) can result in severe disease and death, with no accurate models that allow for early prediction of adverse outcomes. To address this need, we sought to develop serum-based biomarker models to predict CDI outcomes. We prospectively collected sera ≤48 h after diagnosis of CDI in two cohorts. Biomarkers were measured with a custom multiplex bead array assay. Patients were classified using IDSA severity criteria and the development of disease-related complications (DRCs), which were defined as ICU admission, colectomy, and/or death attributed to CDI. Unadjusted and adjusted models were built using logistic and elastic net modeling. The best model for severity included procalcitonin (PCT) and hepatocyte growth factor (HGF) with an area (AUC) under the receiver operating characteristic (ROC) curve of 0.74 (95% confidence interval, 0.67 to 0.81). The best model for 30-day mortality included interleukin-8 (IL-8), PCT, CXCL-5, IP-10, and IL-2Rα with an AUC of 0.89 (0.84 to 0.95). The best model for DRCs included IL-8, procalcitonin, HGF, and IL-2Rα with an AUC of 0.84 (0.73 to 0.94). To validate our models, we employed experimental infection of mice with C. difficile. Antibiotic-treated mice were challenged with C. difficile and a similar panel of serum biomarkers was measured. Applying each model to the mouse cohort of severe and nonsevere CDI revealed AUCs of 0.59 (0.44 to 0.74), 0.96 (0.90 to 1.0), and 0.89 (0.81 to 0.97). In both human and murine CDI, models based on serum biomarkers predicted adverse CDI outcomes. Our results support the use of serum-based biomarker panels to inform Clostridioides difficile infection treatment.

Molecular epidemiology of Clostridioides difficile and risk factors for the detection of toxin gene-positive strains

In this study, we investigated all Clostridioides difficile strains isolated from stool samples in Nagasaki University Hospital between January 2012 and December 2014. Toxin genes (tcdA, tcdB and cdtA/cdtB) were analyzed for multiplex PCR in a total of 213 strains. In the toxin gene-positive strain, PCR ribotyping was conducted using capillary gel electrophoresis-based PCR and the Webribo database. Patients' backgrounds were analyzed by departments, disorders, antimicrobials, and clinical dates. The positive rates of tcdA, tcdB, and cdtA/cdtB genes were 62.9%, 63.4%, and 2.8%, respectively. The most frequent PCR ribotype was 047 (14.1%), followed by 014/0 (11.1%) and 002/0 (8.2%). In univariate analysis, the risk factors for the detection of toxin gene-positive strains in patients were older age (p = 0.0036), over ≥ 65 years old (p = 0.0175), the patients hospitalized at Department of Digestive Surgery (P = 0.0059), higher CRP level (P = 0.0395), and lower albumin level (p = 0.0014). In the multivariate analysis, the risk factor for detection of toxin gene-positive strains was the patients hospitalized at Department of Digestive Surgery (OR; 4.62, 95% CI; 1.18-18.0, p = 0.0274). In this study, the percentage of toxin gene-positive and cdtA/cdtB gene-positive strains was almost the same as that reported in previous studies, but the ribotype was different. In addition, we revealed that the risk factor associated with the detection of toxin gene-positive strains was the patients hospitalized at Department of digestive surgery.

Role of Procalcitonin in the Management of Infected Patients in the Intensive Care Unit

The combination of molecular pathogen diagnostics and the biomarker procalcitonin (PCT) are changing the use of antimicrobials in patients admitted to critical care units with severe community-acquired pneumonia, possible septic shock, or other clinical syndromes. An elevated serum PCT level is good supportive evidence of a bacterial pneumonia, whereas a low serum PCT level virtually eliminates an etiologic role for bacteria even if the culture for a potential bacterial pathogen is positive. Serum PCT levels can be increased in any shocklike state; a low PCT level eliminates invasive bacterial infection as an etiology in more than 90% of patients.

Procalcitonin: Usefulness in Acute Care Surgery and Trauma

BACKGROUND

Procalcitonin (PCT) is a serum biomarker currently suggested by the Surviving Sepsis Campaign to aid in determination of the appropriate duration of therapy in sepsis patients. We review the use of procalcitonin in patients after trauma or acute care surgery.

METHOD

A MEDLINE search via PubMed was performed using the combination of "procalcitonin" and "humans" and "injuries, trauma," "wounds and injuries," or "wounds." Studies of burn patients, children, other biomarkers, and non-acute care surgery were excluded.

RESULTS

Procalcitonin may be useful in identifying infection in trauma and post-operative acute care surgery. However, heterogenity exists among patients, and surgery and trauma alone elevate PCT even in the absence of infection.

CONCLUSIONS

Although trends in PCT concentrations may offer insight, no standard approach can be recommended currently.

Role of Single Procalcitonin Test on Admission as a Biomarker for Predicting the Severity of Clostridium difficile Infection

Objective: To evaluate whether serum Procalcitonin (PCT) at the early stage of infection can serve as a potential biomarker for determining Clostridium difficile infection (CDI) severity.

Methods: Fifty-four patients diagnosed with CDI were enrolled in the study. Serum samples were obtained within a median time of 24–48 h of the lab result for presence of C. difficile. PCT levels were measured by chemiluminescence immunoassay. Demographic, clinical, and prognostic data concerning the patients were retrospectively collected from medical records. The illness severity score was determined according to “Score indices for C. difficile infection severity.”

Results: We found that serum PCT levels were significantly higher in patients with moderate disease, compared to patients with mild disease (p = 0.0032). Additionally, PCT was correlated with mortality (p = 0.0002), white blood cell count (p = 0.019), and community-acquired disease (p = 0.0345).

Conclusion: Early measurement of PCT may serve as a biomarker for early prediction of CDI severity, which is of great importance due to the high risk of complications and death.

Procalcitonin in heart failure: hic et nunc

Although procalcitonin (PCT) was evaluated for the first time in the setting of heart failure (HF) in 1999, its utility in HF patients is still under examination. Patients with HF have significantly higher plasma PCT concentrations than healthy subjects and PCT levels are associated with severity of HF. It has been confirmed that higher levels of PCT are associated with worse outcomes, such as increased mortality and higher rate of rehospitalization, in HF patients with no evidence of infection. Furthermore, it has been approved that PCT-guided antibiotic treatment in HF patients reduces duration of antibiotic therapy and improves outcomes. This review summarizes current evidence from the published literature of the usefulness and limitations of PCT as a biomarker in HF.

Clostridium difficile infection in solid organ transplant recipients

PURPOSE OF REVIEW

Clostridium difficile infection (CDI) is a major healthcare-associated infection that causes significant morbidity and an economic impact in the United States. In this review, we provide an overview of Clostridium difficile infection in solid organ transplant recipients with an emphasis on recent literature.

RECENT FINDINGS

C. difficile in solid organ transplant population has unique risk factors. Fecal microbiota transplantation has shown favorable results in treatment of recurrent C. difficile in this population. Preliminary data from animal studies suggests excellent efficacy with immunization against C. difficile toxins.

SUMMARY

Over the last decade, number of individuals receiving solid organ transplants has increased exponentially making peri-transplant complications a common occurrence.C. difficile is a frequent cause of morbidity in solid organ transplant recipients. Early and accurate diagnosis of C. difficile requires a stepwise approach. Differentiating between asymptomatic carriage and infection is a diagnostic challenge. Microbial diversity is inversely proportional to risk of C. difficile infection. Antimicrobial stewardship programs help to retain microbial diversity in individuals susceptible to CDI. Recurrent or relapsing C. difficile infection require fecal microbiota transplantation for definitive cure.

Host response to Clostridium difficile infection: Diagnostics and detection

Clostridium difficile infection (CDI) is a significant healthcare concern worldwide, and C. difficile is recognised as the most frequent aetiological agent of infectious healthcare-associated diarrhoea in hospitalised adult patients. The clinical manifestation of CDI varies from self-limited diarrhoea to life-threatening colitis. Such a broad disease spectrum can be explained by the impact of host factors. Currently, a complex CDI aetiology is widely accepted, acknowledging the interaction between bacteria and the host. C. difficile strains producing clostridial toxins A and B are considered toxigenic and can cause disease; those not producing the toxins are non-pathogenic. A person colonised with a toxigenic strain will not necessarily develop CDI. It is imperative to recognise patients with active disease from those only colonised with this pathogen and to implement appropriate treatment. This can be achieved by diagnostics that rely on host factors specific to CDI. This review will focus on major aspects of CDI pathogenesis and molecular mechanisms, describing host factors in disease progression and assessment of the host response in order to facilitate the development of CDI-specific diagnostics.

Older Is Not Wiser, Immunologically Speaking: Effect of Aging on Host Response to Clostridium difficile Infections

Clostridium difficile infection (CDI) is the most common cause of antibiotic-associated diarrhea and a significant burden on the health care system. Aging has been identified in the literature as a risk factor for CDI as well as adverse outcome from CDI. Although this effect of advanced age on CDI could be partially explained by clinical factors associated with aging, biologic factors are important. Innate immune system, responsible for immediate response to acute infections, plays a major role in CDI pathogenesis. Impairment in function of innate immunity with aging, demonstrated in other infection models, may lead to worse outcome with CDI. C. difficile toxin-specific antibody response protects the host against initial and recurrent infections as shown in observational studies and clinical trial. Effect of aging on antibody response to CDI has not been demonstrated, but the results from vaccine studies in other infections suggest a negative effect on humoral immunity from aging. Although intestinal microbiota from healthy people confers resistance to CDI by preventing C. difficile colonization, changes in composition of microbiota with aging may affect that resistance and increase risk for CDI. There are also age-associated changes in physiology, especially of the gastrointestinal tract, that may play a role in CDI risk and outcomes. In this review, we will first discuss the epidemiology of CDI in the elderly people, then the alteration in innate immunity, humoral response, and microbiota that increases susceptibility to CDI and severe disease and lastly, the physiological and functional changes that may modify outcomes of infection.

Correlation between fecal calprotectin levels, disease severity and the hypervirulent ribotype 027 strain in patients with Clostridium difficile infection

Background

Clostridium difficile is the most common infectious etiology of nosocomial diarrhea. Fecal calprotectin (fc) is a sensitive marker of intestinal inflammation, found to be associated with enteric bacterial infections and inflammatory bowel disease.

Methods

We evaluated fc levels using a Chemiluminescent immunoassay method, in hospitalized patients with C. difficile infection (CDI) diagnosed by molecular stool examination and assessed correlation with virulent ribotype 027 strain infection, antibiotic susceptibility by gradient Etest strip performed on C. difficile colonies and clinical and laboratory measures of disease severity. Statistical analysis was performed for correlation of fc levels with clinical and laboratory parameters, disease severity and patient outcomes.

Results

Overall 29 patients with CDI were admitted at the Poria medical center in northern Israel, during June 2014-May 2015. Resistance to metronidazole was found in 3 (10.3 %) isolates and to vancomycin in 5 (17.2 %) isolates. Regarding patient outcomes, within 30 days of CDI diagnosis, recurrence of disease occurred in 10 (34.5 %) patients and 2 patients (6.9 %) died. Seven (24.1 %) isolates were C. difficile ribotype 027. Mean fc level was 331.4 μg/g (21–932). Higher fc levels were found in patients with C. difficile ribotype 027 (p < 0.0005). Fc levels were also correlated with elevated peripheral blood white cell count (p = 0.0007). A trend for higher fc levels was found in patients with a higher clostridium severity score index (p = 0.0633). No correlation was found between fecal calprotectin levels and age, sex, functional status, community versus hospital acquired CDI, antibiotic susceptibility, fever, and creatinine levels.

Conclusions

Our study highlights the fact that fc has a potential role as a biomarker of disease severity and binary toxin producing ribotype associated disease.

Elevated fecal calprotectin associates with adverse outcomes from Clostridium difficile infection in older adults

BACKGROUND

Clostridium difficile infection (CDI) causes a mild to moderate colitis in most patients, but some, especially older adults, develop severe, adverse outcomes. Biomarkers predicting outcomes are needed to optimize treatments. This study tested whether fecal calprotectin associated with a composite primary outcome of complicated CDI (intensive care unit admission, colectomy, or death due to CDI within 30 days of diagnosis) and/or 8-week recurrence.

METHODS

Stool was collected in Cary-Blair media at the time of diagnosis from inpatients of age >60 years that tested positive for C. difficile (enzyme immunoassay [EIA] for toxin A/B or polymerase chain reaction for the tcdB gene). Fecal calprotectin was measured and normalized to solid stool weight. Analysis was performed using logistic regression. Variables were selected for the final model using likelihood ratio tests.

RESULTS

Fifty patients were included with a mean age 72.8 (± 7.5), and 13 (26%) developed the primary outcome. Clinical variables such as age, gender, and comorbid disease did not associate with complicated CDI/recurrence, nor did traditional biomarkers such as serum albumin or white blood cell count. A high normalized fecal calprotectin (>2000 μg/g) associated with the primary outcome in the final model after adjustment for gender and detectable fecal toxin(s) by EIA (OR 24.9, 95% CI 2.4-257.9, p = 0.007) with a specificity of 91.9%.

CONCLUSION

This study provides evidence that fecal calprotectin level associates with complications from CDI in older adults. Further studies are required to validate these findings in larger cohorts and incorporate them into clinical prediction algorithms.

Utility of blood procalcitonin concentration in the management of cancer patients with infections

Diagnosis of infections in cancer patients is usually problematic since differentiating between infection and fever of unknown origin is often a considerable clinical challenge. In general, increase concentration of blood procalcitonin (PCT) is associated with severe bacterial infection. PCT with an optimal cutoff level of 0.5 ng/mL seems to be the most helpful biochemical parameter in detecting severe infections, mainly bloodstream infection, in patients with hematological cancers. In all clinical situations, the elevated level of PCT should be carefully analyzed, always with a thorough physical examination and an appropriate microbiological assessment.

Serum 25-Hydroxyvitamin D Levels are not Associated with Adverse Outcomes in Clostridium Difficile Infection

Clostridium difficile infection (CDI) is a significant source of healthcare-associated morbidity and mortality. This study investigated whether serum 25-hydroxyvitamin D is associated with adverse outcomes from CDI. Patients with CDI were prospectively enrolled. Charts were reviewed and serum 25-hydroxyvitamin D was measured. The primary outcome was a composite definition of severe disease: fever (temperature >38°C), acute organ dysfunction, or serum white blood cell count >15,000 cells/µL within 24-48 hours of diagnosis; lack of response to therapy by day 5; and intensive care unit admission; colectomy; or death within 30 days. Sixty-seven patients were included in the final analysis. Mean (±SD) serum 25-hydroxyvitamin D was 26.1 (±18.54) ng/mL. Severe disease, which occurred in 26 (39%) participants, was not associated with serum 25-hydroxyvitamin D [odds ratio (OR) 1.00; 95% confidence interval (CI) 0.96-1.04]. In the adjusted model for severe disease only serum albumin (OR 0.12; 95%CI 0.02-0.64) and diagnosis by detection of stool toxin (OR 5.87; 95%CI 1.09-31.7) remained independent predictors. We conclude that serum 25-hydroxyvitamin D is not associated with the development of severe disease in patients with CDI.

Usefulness of Adjunctive Fecal Calprotectin and Serum Procalcitonin in Individuals Positive for Clostridium difficile Toxin Gene by PCR Assay

In 54/64 subjects with nosocomial diarrhea, fecal calprotectin levels correlated with the results of stool samples tested for Clostridium difficile toxin gene by PCR. Fecal calprotectin levels can be used as an adjunctive measure to PCR to support the diagnosis of C. difficile infection.

Factors Associated With Complications of Clostridium difficile Infection in a Multicenter Prospective Cohort

BACKGROUND

Clostridium difficile infection (CDI) is the most common cause of nosocomial infectious diarrhea and may result in severe complications including death. We conducted a prospective study to identify risk factors for complications of CDI (cCDI).

METHODS

Adult inpatients with confirmed CDI in 10 Canadian hospitals were enrolled and followed for 90 days. Potential risk factors were measured within 24 hours of diagnosis. Isolates were typed by polymerase chain reaction ribotyping. cCDI was defined as 1 or more of the following: colonic perforation, toxic megacolon, colectomy, admission to an intensive care unit for cCDI, or if CDI contributed to death within 30 days of enrollment. Risk factors for cCDI were investigated by logistic regression.

RESULTS

A total of 1380 patients were enrolled. cCDI was observed in 8% of patients. The ribotype was identified in 922 patients, of whom 52% were infected with R027. Age ≥ 80 years, heart rate >90/minute, respiratory rate >20/minute, white cell count <4 × 10(9)/L or ≥ 20 × 10(9)/L, albumin <25 g/L, blood urea nitrogen >7 mmol/L, and C-reactive protein ≥ 150 mg/L were independently associated with cCDI. A higher frequency of cCDI was observed among R027-infected patients (10.9% vs 7.2%), but the association was not significant in adjusted analysis.

CONCLUSIONS

CDI complications were associated with older age, abnormal blood tests, and abnormal vital signs. These factors, which are readily available to clinicians at the time of diagnosis, could be used for outcome prediction and risk stratification to select patients who may need closer monitoring or more aggressive therapy.

Systems Modeling of Interactions between Mucosal Immunity and the Gut Microbiome during Clostridium difficile Infection

Clostridium difficile infections are associated with the use of broad-spectrum antibiotics and result in an exuberant inflammatory response, leading to nosocomial diarrhea, colitis and even death. To better understand the dynamics of mucosal immunity during C. difficile infection from initiation through expansion to resolution, we built a computational model of the mucosal immune response to the bacterium. The model was calibrated using data from a mouse model of C. difficile infection. The model demonstrates a crucial role of T helper 17 (Th17) effector responses in the colonic lamina propria and luminal commensal bacteria populations in the clearance of C. difficile and colonic pathology, whereas regulatory T (Treg) cells responses are associated with the recovery phase. In addition, the production of anti-microbial peptides by inflamed epithelial cells and activated neutrophils in response to C. difficile infection inhibit the re-growth of beneficial commensal bacterial species. Computational simulations suggest that the removal of neutrophil and epithelial cell derived anti-microbial inhibitions, separately and together, on commensal bacterial regrowth promote recovery and minimize colonic inflammatory pathology. Simulation results predict a decrease in colonic inflammatory markers, such as neutrophilic influx and Th17 cells in the colonic lamina propria, and length of infection with accelerated commensal bacteria re-growth through altered anti-microbial inhibition. Computational modeling provides novel insights on the therapeutic value of repopulating the colonic microbiome and inducing regulatory mucosal immune responses during C. difficile infection. Thus, modeling mucosal immunity-gut microbiota interactions has the potential to guide the development of targeted fecal transplantation therapies in the context of precision medicine interventions.

Variation in germination of Clostridium difficile clinical isolates correlates to disease severity

Over the past two decades, Clostridium difficile infections have been increasing in both number and severity throughout the world. As with other spore forming bacteria, germination is a vital step in the life cycle of this pathogen. Studies have examined differences in sporulation and toxin production among a number of C. difficile clinical isolates; however, few have examined differences in germination and the relationship between this phenotype and disease severity. Here, over 100 C. difficile isolates from the University of Michigan Health System were examined for overall germination in response to various combinations of known germinants (taurocholate) and co-germinants (glycine and histidine). Significant variation was observed among isolates under all conditions tested. Isolates representing ribotype 014-020, which was the most frequently isolated ribotype at our hospital, exhibited increased germination in the presence of taurocholate and glycine when compared to isolates representing other ribotypes. Interestingly, isolates that caused severe disease exhibited significantly lower germination in response to minimal germination conditions (taurocholate only), indicating increased control over germination in these isolates. These data provide a broad picture of C. difficile isolate germination and indicate a role for precise control of germination in disease severity.

Evaluation of portability and cost of a fluorescent PCR ribotyping protocol for Clostridium difficile epidemiology

Clostridium difficile is the most commonly identified pathogen among health care-associated infections in the United States. There is a need for accurate and low-cost typing tools that produce comparable data across studies (i.e., portable data) to help characterize isolates during epidemiologic investigations of C. difficile outbreaks and sporadic cases of disease. The most popular C. difficile-typing technique is PCR ribotyping, and we previously developed methods using fluorescent PCR primers and amplicon sizing on a Sanger-style sequencer to generate fluorescent PCR ribotyping data. This technique has been used to characterize tens of thousands of C. difficile isolates from cases of disease. Here, we present validation of a protocol for the cost-effective generation of fluorescent PCR ribotyping data. A key component of this protocol is the ability to accurately identify PCR ribotypes against an online database (http://walklab.rcg.montana.edu) at no cost. We present results from a blinded multicenter study to address data portability across four different laboratories and three different sequencing centers. Our standardized protocol and centralized database for typing of C. difficile pathogens will increase comparability between studies so that important epidemiologic linkages between cases of disease and patterns of emergence can be rapidly identified.

The molecular basis of Clostridium difficile disease and host response

PURPOSE OF REVIEW

Clostridium difficile infection (CDI) ranges from asymptomatic colonization to severe colitis and death. The physiologic and molecular mechanisms determining disease outcome are thus far poorly understood. Here, we review recent advances in the relationship between host response to infection and disease outcome. Furthermore, we review recent studies on the relationship between intestinal microbial ecology and pathogenesis of CDI.

RECENT FINDINGS

Severe CDI is characterized by toxin-induced epithelial injury and marked intestinal inflammation. Recent studies demonstrate that systemic markers of inflammation correlate with disease outcome. Peripheral neutrophil count, C-reactive protein, and proinflammatory cytokines are elevated in patients with severe disease as compared with asymptomatic controls. Furthermore, fecal inflammatory biomarkers are better predictors of disease severity and diarrhea persistence than C. difficile abundance. A landmark study reported higher than 80% success rate of fecal microbiota transplantation for treatment of recurrent CDI. The commensal microbes responsible for C. difficile protection, and the molecular basis by which microbial ecology impacts disease outcome, are under active investigation.

SUMMARY

Under conditions of altered microbial ecology, C. difficile incites epithelial injury and marked intestinal inflammation, the primary determinant of disease outcome. Restoration of a diverse intestinal microbial population by fecal microbiota transplantation attenuates disease and prevents recurrence by mechanisms that are yet to be fully elucidated.

Chondroitin sulfate proteoglycan 4 functions as the cellular receptor for Clostridium difficile toxin B

As a gram-positive, spore-forming anaerobic bacillus, Clostridium difficile (C. difficile) is responsible for severe and fatal pseudomembranous colitis, and poses the most urgent antibiotic resistance threat worldwide. Epidemic C. difficile is the leading cause of antibiotic-associated diarrhoea globally, especially diarrhoea due to the emergence of hypervirulent strains associated with high mortality and morbidity. TcdB, one of the key virulence factors secreted by this bacterium, enters host cells through a poorly understood mechanism to elicit its pathogenic effect. Here we report the first identification of the TcdB cellular receptor, chondroitin sulfate proteoglycan 4 (CSPG4). CSPG4 was initially isolated from a whole-genome human shRNAmir library screening, and its role was confirmed by both TALEN- and CRISPR/Cas9-mediated gene knockout in human cells. CSPG4 is critical for TcdB binding to the cell surface, inducing cytoskeleton disruption and cell death. A direct interaction between the N-terminus of CSPG4 and the C-terminus of TcdB was confirmed, and the soluble peptide of the toxin-binding domain of CSPG4 could protect cells from the action of TcdB. Notably, the complete loss of CSPG4/NG2 decreased TcdB-triggered interleukin-8 induction in mice without significantly affecting animal mortality. Based on both the in vitro and in vivo studies, we propose a dual-receptor model for TcdB endocytosis. The discovery of the first TcdB receptor reveals a previously unsuspected role for CSPG4 and provides a new therapeutic target for the treatment of C. difficile infection.

Serum mannose-binding lectin concentration, but not genotype, is associated with Clostridium difficile infection recurrence: a prospective cohort study

Low mannose-binding lectin concentration, but not genotype, was associated with disease recurrence in a large prospective cohort of patients with Clostridium difficile infection.

Background. Mannose-binding lectin (MBL) plays a key role in the activation of the lectin-complement pathway of innate immunity, and its deficiency has been linked with several acute infections. However, its role in predisposing to, or modulating disease severity in, Clostridium difficile infection (CDI) has not been investigated.

Methods. We prospectively recruited 308 CDI case patients and 145 control patients with antibiotic-associated diarrhea (AAD). CDI outcome measures were disease severity, duration of symptoms, 30-day mortality, and 90-day recurrence. Serum concentrations of MBL were determined using a commercial enzyme-linked immunosorbent assay transferred to an electrochemiluminescence–based platform. MBL2 polymorphisms were typed using a combination of pyrosequencing and TaqMan genotyping assays.

Results. The frequency of the MBL2 genetic variants was similar to that reported in other white populations. MBL serum concentrations in CDI and AAD subjects were determined by MBL2 exonic variants B, C, and D and the haplotypes (LYPB, LYQC, and HYPD). There was no difference in either MBL concentrations or genotypes between cases and controls. MBL concentration, but not genotype, was a determinant of CDI recurrence (odds ratios, 3.18 [95% confidence interval {CI}, 1.40–7.24] and 2.61 [95% CI, 1.35–5.04] at the <50 ng/mL and <100 ng/mL cutoff points, respectively; P < .001). However, neither MBL concentration nor MBL2 genotype was linked with the other CDI outcomes.

Conclusions. Serum MBL concentration did not differentiate between CDI cases and AAD controls, but among CDI cases, MBL concentration, but not genotype, was associated with CDI recurrence, indicating that MBL acts as a modulator of disease, rather than a predisposing factor.

Risk factors for recurrence, complications and mortality in Clostridium difficile infection: a systematic review

BACKGROUND

Clostridium difficile infection (CDI) can lead to complications, recurrence, and death. Numerous studies have assessed risk factors for these unfavourable outcomes, but systematic reviews or meta-analyses published so far were limited in scope or in quality.

METHODS

A systematic review was completed according to PRISMA guidelines. An electronic search in five databases was performed. Studies published until October 2013 were included if risk factors for at least one CDI outcome were assessed with multivariate analyses.

RESULTS

68 studies were included: 24 assessed risk factors for recurrence, 18 for complicated CDI, 8 for treatment failure, and 30 for mortality. Most studies accounted for mortality in the definition of complicated CDI. Important variables were inconsistently reported, such as previous episodes and use of antibiotics. Substantial heterogeneity and methodological limitations were noted, mainly in the sample size, the definition of the outcomes and periods of follow-up, precluding a meta-analysis. Older age, use of antibiotics after diagnosis, use of proton pump inhibitors, and strain type were the most frequent risk factors for recurrence. Older age, leucocytosis, renal failure and co-morbidities were frequent risk factors for complicated CDI. When considered alone, mortality was associated with age, co-morbidities, hypo-albuminemia, leucocytosis, acute renal failure, and infection with ribotype 027.

CONCLUSION

Laboratory parameters currently used in European and American guidelines to define patients at risk of a complicated CDI are adequate. Strategies for the management of CDI should be tailored according to the age of the patient, biological markers of severity, and underlying co-morbidities.

Risk factors for recurrence, complications and mortality in Clostridium difficile infection: a systematic review

BACKGROUND

Clostridium difficile infection (CDI) can lead to complications, recurrence, and death. Numerous studies have assessed risk factors for these unfavourable outcomes, but systematic reviews or meta-analyses published so far were limited in scope or in quality.

METHODS

A systematic review was completed according to PRISMA guidelines. An electronic search in five databases was performed. Studies published until October 2013 were included if risk factors for at least one CDI outcome were assessed with multivariate analyses.

RESULTS

68 studies were included: 24 assessed risk factors for recurrence, 18 for complicated CDI, 8 for treatment failure, and 30 for mortality. Most studies accounted for mortality in the definition of complicated CDI. Important variables were inconsistently reported, such as previous episodes and use of antibiotics. Substantial heterogeneity and methodological limitations were noted, mainly in the sample size, the definition of the outcomes and periods of follow-up, precluding a meta-analysis. Older age, use of antibiotics after diagnosis, use of proton pump inhibitors, and strain type were the most frequent risk factors for recurrence. Older age, leucocytosis, renal failure and co-morbidities were frequent risk factors for complicated CDI. When considered alone, mortality was associated with age, co-morbidities, hypo-albuminemia, leucocytosis, acute renal failure, and infection with ribotype 027.

CONCLUSION

Laboratory parameters currently used in European and American guidelines to define patients at risk of a complicated CDI are adequate. Strategies for the management of CDI should be tailored according to the age of the patient, biological markers of severity, and underlying co-morbidities.

The systemic inflammatory response to Clostridium difficile infection

Background

The systemic inflammatory response to Clostridium difficile infection (CDI) is incompletely defined, particularly for patients with severe disease.

Methods

Analysis of 315 blood samples from 78 inpatients with CDI (cases), 100 inpatients with diarrhea without CDI (inpatient controls), and 137 asymptomatic outpatient controls without CDI was performed. Serum or plasma was obtained from subjects at the time of CDI testing or shortly thereafter. Severe cases had intensive care unit admission, colectomy, or death due to CDI within 30 days after diagnosis. Thirty different circulating inflammatory mediators were quantified using an antibody-linked bead array. Principal component analysis (PCA), multivariate analysis of variance (MANOVA), and logistic regression were used for analysis.

Results

Based on MANOVA, cases had a significantly different inflammatory profile from outpatient controls but not from inpatient controls. In logistic regression, only chemokine (C-C motif) ligand 5 (CCL5) levels were associated with cases vs. inpatient controls. Several mediators were associated with cases vs. outpatient controls, especially hepatocyte growth factor, CCL5, and epithelial growth factor (inversely associated). Eight cases were severe and associated with elevations in IL-8, IL-6, and eotaxin.

Conclusions

A broad systemic inflammatory response occurs during CDI and severe cases appear to differ from non-severe infections.

The relationship between phenotype, ribotype, and clinical disease in human Clostridium difficile isolates

Since 2000, Clostridium difficile isolates of ribotype 027 have been linked to outbreaks in North America and Europe and also an increased rate of colectomy and death among infected individuals. It has been proposed that enhanced sporulation and toxin production were associated with this apparent increase in virulence of 027 isolates. Since only a limited number of isolates have been examined, the relationship of these phenotypes to a specific ribotype, and as well as to clinical disease severity, remains controversial. 106 recent clinical isolates from the University of Michigan Health System were characterized for the ability to sporulate, produce viable spores, grow in rich media, and produce toxins in vitro. Significant variation was observed between isolates for each of these phenotypes. Isolates of ribotype 027 produced higher levels of toxin and exhibited slower growth compared to other ribotypes. Importantly, increased spore production did appear to be relevant to severe C. difficile infection, as determined by available clinical meta-data. These data provide the first significant difference between isolates from severe vs. less severe disease based on an in vitro C. difficile phenotype and suggest that clinical outcome is better predicted by bacterial attributes other than ribotype.