NAP1 strain type predicts outcomes from Clostridium difficile infection

Complications of Hospital-Onset Healthcare Facility-Associated Clostridium difficile Infections Among Veterans

Complications within 30 days of a clinically confirmed hospital-onset Clostridium difficile infection diagnosis from July 1, 2012, through June 30, 2015, in 127 acute care Veterans Health Administration facilities were evaluated. Pooled rates for attributable intensive care unit admissions, colectomies, and deaths were 2.7%, 0.5%, and 0.4%, respectively. Infect Control Hosp Epidemiol 2016;37:717-719.

Current Trends in the Epidemiology and Outcomes of Clostridium difficile Infection

Clostridium difficile is the most frequently identified cause of nosocomial diarrhea and has been associated with epidemics of diarrhea in hospitals and long-term care facilities. The continued increase in C. difficile infection (CDI) suggests that it has surpassed other pathogens in causing healthcare-associated infections. The Centers for Disease Control and Prevention recently identified CDI as an "urgent threat" in its recent report on antibiotic resistance threats in the United States, highlighting the need for urgent and aggressive action to prevent this infection. The impact of antibiotics as a risk factor for new-onset CDI is well established; however, recognizing classes of antibiotics with the highest risks and reducing unnecessary antibiotic use are important strategies for prevention of CDI and subsequent recurrence. In addition, the recognition of the community as an important setting for onset of CDI presents a challenge and is an area for future research.

Clostridium difficile infection (CDI) severity and outcome among patients infected with the NAP1/BI/027 strain in a non-epidemic setting

OBJECTIVE

Determine whether the NAP1 strain identified by polymerase chain reaction (PCR)-based stool assay is correlated with CDI severity and clinical outcomes.

METHODS

Medical records of adult patients with positive stool Xpert® Clostridium difficile PCR assay for an initial episode of CDI between January 2012 and January 2013 at a tertiary care hospital in Chicago were reviewed. Two patients diagnosed with CDI caused by a non-NAP1 strain (positive Xpert® C. difficile assay but negative Xpert® C. difficile Epi assay) were included for each patient diagnosed with CDI caused by a NAP1 strain (positive Epi assay). Patient charts were reviewed for markers of severity, risk factors, treatment regimens, and outcomes.

RESULTS

Of 494 stool specimens, 90 (18%) that were positive for C. difficile by PCR were positive for NAP1 strain. In total, 37 patients with CDI due to NAP1 were matched with 74 patients with CDI due to non-NAP1 strains. Multivariable model revealed individuals ≥65 years old were 3 times more likely to have NAP1 strain than individuals <65 (P=.02). Residents of a nursing home prior to hospitalization were 10 times more likely to have NAP1 strain than patients residing in their homes (P=.001). More NAP1 cases had a change in treatment from metronidazole to oral vancomycin plus intravenous metronidazole (P=.01). The severity of CDI, incidence of mortality and recurrent CDI were similar between groups.

CONCLUSIONS

In a nonepidemic setting, NAP1 strains were more common in older patients and individuals admitted from nursing homes. Identification of NAP1 by PCR of stool specimens was associated in a change of therapy but did not predict worse outcomes. Reporting strain results may not be clinically useful in routine settings.

Clostridium difficile outbreak caused by NAP1/BI/027 strain and non-027 strains in a Mexican hospital

Background

Clostridium difficile infections caused by the NAP1/B1/027 strain are more severe, difficult to treat, and frequently associated with relapses.

Methods

A case–control study was designed to examine a C. difficile infection (CDI) outbreak over a 12-month period in a Mexican hospital. The diagnosis of toxigenic CDI was confirmed by real-time polymerase chain reaction, PCR (Cepheid Xpert C. difficile/Epi).

Results

During the study period, 288 adult patients were evaluated and 79 (27.4%) patients had confirmed CDI (PCR positive). C. difficile strain NAP1/B1/027 was identified in 31 (39%) of the patients with confirmed CDI (240 controls were included). Significant risk factors for CDI included any underlying disease (p < 0.001), prior hospitalization (p < 0.001), and antibiotic (p < 0.050) or steroid (p < 0.001) use. Laboratory abnormalities included leukocytosis (p < 0.001) and low serum albumin levels (p < 0.002). Attributable mortality was 5%. Relapses occurred in 10% of patients. Risk factors for C. difficile NAP1/B1/027 strain infections included prior use of quinolones (p < 0.03).

Risk factors for CDI caused by non-027 strains included chronic cardiac disease (p < 0.05), chronic renal disease (p < 0.009), and elevated serum creatinine levels (p < 0.003). Deaths and relapses were most frequent in the 027 group (10% and 19%, respectively).

Conclusions

C. difficile NAP1/BI/027 strain and non-027 strains are established pathogens in our hospital. Accordingly, surveillance of C. difficile infections is now part of our nosocomial prevention program.

Risk Factors for Recurrent Clostridium difficile Infections and Strategies to Decrease Readmissions in a Community Hospital

BACKGROUND

Currently there are no universally accepted approaches for the prevention of recurrent Clostridium difficile infections (CDI) following the initial infection. Several studies have identified common risk factors for the emergence of recurrent CDI. Identifying patients at high risk for recurrent CDI through the assessment of risk factors at initial diagnosis could enable health care providers to optimize available treatment options. A vancomycin hydrochloride-tapered regimen may be an effective treatment option for the prevention of recurrent CDI following the initial infection.

METHODS

In this single-center, prospective study, we examined the efficacy of orally administered vancomycin-tapered regimens for the prevention of recurrent CDI in high-risk patients. High-risk patients were identified using patient risk factors found in a retrospective chart review. The primary objective was to decrease hospital readmissions for recurrent CDI. The secondary objective was to improve the discharge coordination-of-care process by providing a pharmacy benefits evaluation, which ensured vancomycin affordability and assistance in prescription attainment, and discharge counseling.

RESULTS

Of the 83 patients enrolled in the study, 5 experienced recurrent CDI (6%). Memorial Health Care System's (Chattanooga, Tennessee) historical recurrent CDI rate was 8.2%. Thirty-one of the 83 patients received a vancomycin-tapered regimen following their initial infection (37%). A pharmacy benefits evaluation was performed on 35 of the 57 patients who were discharged home on vancomycin (61%).

CONCLUSIONS

Vancomycin-tapered regimens may provide a cost-effective method for the prevention of recurrent CDI following an initial infection in patients at high risk for recurrence.

Clinical Utility of Laboratory Detection of Clostridium difficile Strain BI/NAP1/027

Clostridium difficile strain BI/NAP1/027 is associated with increased C. difficile infection (CDI) rates and severity, and the efficacy of some CDI therapies may be strain dependent. Although cultured C. difficile isolates can be reliably subtyped by various methods, the long turnaround times, high cost, and limited availability of strain typing preclude their routine use. Nucleic acid amplification tests identify BI/NAP1/027 rapidly from stool, but the emergence of closely related strains compromises test specificity. Although detection of epidemiologically significant pathogens is generally useful for infection control programs, specific data supporting use of rapid detection of BI/NAP1/027 as an infection control tool are still awaited.

The morbidity, mortality, and costs associated with Clostridium difficile infection

Clostridium difficile infection (CDI) is the most common cause of infectious health care-associated diarrhea and is a major burden to patients and the health care system. The incidence and severity of CDI remain at historically high levels. This article reviews the morbidity, mortality, and costs associated with CDI.

Immune-based treatment and prevention of Clostridium difficile infection

Clostridium difficile (C. difficile) causes over 500,000 infections per year in the US, with an estimated 15,000 deaths and an estimated cost of $1-3 billion. Moreover, a continual rise in the incidence of severe C. difficile infection (CDI) has been observed worldwide. Currently, standard treatment for CDI is the administration of antibiotics. While effective, these treatments do not prevent and may contribute to a disease recurrence rate of 15-35%. Prevention of recurrence is one of the most challenging aspects in the field. A better knowledge of the molecular mechanisms of the disease, the host immune response and identification of key virulence factors of C. difficilenow permits the development of immune-based therapies. Antibodies specific for C. difficile toxins have been shown to effectively treat CDI and prevent disease relapse in animal models and in humans. Vaccination has been recognized as the most cost-effective treatment/prevention for CDI. This review will summarize CDI transmission, epidemiology, major virulent factors and highlights the rational and the development of immune-based approaches against this remerging threat.

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.

In the Endemic Setting, Clostridium difficile Ribotype 027 Is Virulent But Not Hypervirulent

BACKGROUND

Conflicting reports have been published on the association between Clostridium difficile ribotypes and severe disease outcomes in patients with C. difficile infection (CDI); several so-called hypervirulent ribotypes have been described. We performed a multicenter study to assess severe disease presentation and severe outcomes among CDI patients infected with different ribotypes.

METHODS

Stool samples that tested positive for C. difficile toxin were collected and cultured from patients who presented to any of 7 different hospitals in Houston, Texas (2011-2013). C. difficile was characterized using a fluorescent PCR ribotyping method. Medical records were reviewed to determine clinical characteristics and ribotype association with severe CDI presentation (ie, leukocytosis and/or hypoalbuminemia) and severe CDI outcomes (ie, ICU admission, ileus, toxic megacolon, colectomy, and/or in-hospital death).

RESULTS

Our study included 715 patients aged 61±18 years (female: 63%; median Charlson comorbidity index: 2.5±2.4; hospital-onset CDI: 45%; severe CDI: 36.7%; severe CDI outcomes: 12.3%). The most common ribotypes were 027, 014-020, FP311, 002, 078-126, and 001. Ribotype 027 was a significant independent predictor of severe disease (adjusted odds ratio [aOR], 2.24; 95% confidence interval [CI], 1.53-3.29; P<.001) and severe CDI outcomes (aOR, 1.71; 95% CI, 1.02-2.85; P=.041) compared with all other ribotypes in aggregate. However, in an analysis using all common ribotypes as individual variables, ribotype 027 was not associated with severe CDI outcomes more often than other ribotypes.

CONCLUSION

Ribotype 027 showed virulence equal to that of other ribotypes identified in this endemic setting. Clinical severity markers of CDI may be more predictive of severe CDI outcomes than a particular ribotype.

Risk for Clostridium difficile infection after radical cystectomy for bladder cancer: Analysis of a contemporary series

INTRODUCTION

This study seeks to evaluate the incidence and associated risk factors of Clostridium difficile infection (CDI) in patients undergoing radical cystectomy (RC) for bladder cancer.

METHODS

We retrospectively reviewed a single institution׳s bladder cancer database including all patients who underwent RC between 2010 and 2013. CDI was diagnosed by detection of Clostridium difficile toxin B gene using polymerase chain reaction-based stool assay in patients with clinically significant diarrhea within 90 days of the index operation. A multivariable logistic regression model was used to identify demographics and perioperative factors associated with developing CDI.

RESULTS

Of the 552 patients who underwent RC, postoperative CDI occurred in 49 patients (8.8%) with a median time to diagnosis after RC of 7 days (interquartile range: 5-19). Of the 122 readmissions for postoperative complications, 10% (n = 12) were related to CDI; 2 patients died of sepsis directly related to severe CDI. On multivariate logistic regression, the use of chronic antacid therapy (odds ratio = 1.9, 95% CI: 1.02-3.68, P = 0.04) and antibiotic exposure greater than 7 days (odds ratio = 2.2, 95% CI: 1.11-4.44, P = 0.02) were independently associated with developing CDI. The use of preoperative antibiotics for positive findings on urine culture within 30 days before surgery was not statistically significantly associated with development of CDI (P = 0.06).

CONCLUSIONS

The development of CDI occurs in 8.8% of patients undergoing RC. Our study demonstrates that use of chronic antacid therapy and long duration of antimicrobial exposure are associated with development of CDI. Efforts focusing on minimizing antibiotic exposure in patients undergoing RC are needed, and perioperative antimicrobial prophylaxis guidelines should be followed.

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.

Incorrect diagnosis of Clostridium difficile infection in a university hospital in Japan

Physicians often fail to suspect Clostridium difficile infection (CDI) and many microbiology laboratories use suboptimal diagnostic techniques. To estimate the extent of and reasons for incorrect diagnosis of CDI in Japan, we investigated toxigenic C. difficile isolated from all stool culture samples and clinical course. Over a 12-month period in 2010, all stool culture samples (n = 975) submitted from inpatients in a university hospital in Japan were cultured for C. difficile and routine microbiological testing was conducted. In total, 177 C. difficile isolates were recovered, and 127 isolates were toxigenic. Among the toxin-A-positive/toxin-B-positive isolates, 12 were also positive for the binary toxin gene. However, clinically important ribotypes, such as 027 and 078, were not identified. A total of 58 (45.7%) cases with toxigenic C. difficile had unformed stool, and the incidence CDI was 1.6 cases per 10,000 patient-days. Of these 58 cases, 40 were not diagnosed in routine testing due to a lack of clinical suspicion (24.1%, 14/58) or a negative C. difficile toxin assay result (44.8%, 26/58). A stool toxin assay was performed in 54 patients (78.2%, 54/69) who did not have unformed stool. The present study demonstrated that a significant number of CDI cases in Japan might be overlooked or misdiagnosed in clinical practice due to a lack of clinical suspicion and limitations of microbiological testing for CDI in Japan. Providing education to promote awareness of CDI among physicians is important to improve the accuracy of diagnosis in Japan.

Emerging technologies for the clinical microbiology laboratory

In this review we examine the literature related to emerging technologies that will help to reshape the clinical microbiology laboratory. These topics include nucleic acid amplification tests such as isothermal and point-of-care molecular diagnostics, multiplexed panels for syndromic diagnosis, digital PCR, next-generation sequencing, and automation of molecular tests. We also review matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) and electrospray ionization (ESI) mass spectrometry methods and their role in identification of microorganisms. Lastly, we review the shift to liquid-based microbiology and the integration of partial and full laboratory automation that are beginning to impact the clinical microbiology laboratory.

Risk Factors for Acquisition and Loss of Clostridium difficile Colonization in Hospitalized Patients

Asymptomatic colonization may contribute to Clostridium difficile transmission. Few data identify which patients are at risk for colonization. We performed a prospective cohort study of C. difficile colonization and risk factors for C. difficile acquisition and loss in hospitalized patients. Patients admitted to medical or surgical wards at a tertiary care hospital were enrolled; interviews and chart review were performed to determine patient demographics, C. difficile infection (CDI) history, medications, and health care exposures. Stool samples/rectal swabs were collected at enrollment and discharge; stool samples from clinical laboratory tests were also included. Samples were cultured for C. difficile, and the isolates were tested for toxins A and B and ribotyped. Chi-square tests and univariate logistic regression were used for the analyses. Two hundred thirty-five patients were enrolled. Of the patients, 21% were colonized with C. difficile (toxigenic and nontoxigenic) at admission and 24% at discharge. Ribotype 027 accounted for 6% of the strains at admission and 12% at discharge. Of the patients colonized at admission, 78% were also colonized at discharge. Cephalosporin use was associated with C. difficile acquisition (47% of patients who acquired C. difficile versus 25% of patients who did not; P = 0.03). β-lactam-β-lactamase inhibitor combinations were associated with a loss of C. difficile colonization (36% of patients who lost C. difficile colonization versus 8% of patients colonized at both admission and discharge; P = 0.04), as was metronidazole (27% versus 3%; P = 0.03). Antibiotic use affects the epidemiology of asymptomatic C. difficile colonization, including acquisition and loss, and it requires additional study.

Causes, Burden, and Prevention of Clostridium difficile Infection

Clostridium difficile infection (CDI) is a potentially deadly cause of diarrhea that is virtually always connected to healthcare system exposures, both inpatient and outpatient. Once a disease mainly of hospitals, 75% of CDI cases are now diagnosed outside of hospitals. However, the diagnosis location may not reflect where C. difficile spores were acquired or antibiotic exposure occurred. Changing epidemiology and increasing awareness about the role of every segment of the healthcare system in mediating this disease makes it clear that reducing its burden will also require active participation from all US healthcare professionals.

Regional and seasonal variation in Clostridium difficile infections among hospitalized patients in the United States, 2001-2010

BACKGROUND

This study identified national regional and seasonal variations in Clostridium difficile infection (CDI) incidence and mortality among hospitalized patients in the United States over a 10-year period.

METHODS

This was a retrospective cohort study of the U.S. National Hospital Discharge Survey from 2001-2010. Eligible cases had an ICD-9-CM discharge diagnosis code for CDI (008.45). Data weights were used to derive national estimates. CDI incidence and mortality were presented descriptively. Regions were as defined by the U.S. Census Bureau. Seasons included the following: winter (December-February), spring (March-May), summer (June-August), and fall (September-November).

RESULTS

These data represent 2.3 million CDI discharges. Overall, CDI incidence was highest in the Northeast (8.0 CDIs/1,000 discharges) and spring (6.2 CDIs/1,000 discharges). CDI incidence was lowest in the West (4.8 CDIs/1,000 discharges) and fall (5.6 CDIs/1,000 discharges). Peak CDI incidence among children occurred in the West (1.7 CDI/1,000 discharges) and winter (1.5 CDI/1,000 discharges). Mortality among all CDI patients was highest in the Midwest (7.3%) and during the winter (7.9%).

CONCLUSION

The region and season with the highest CDI incidence rates among patients hospitalized in U.S. hospitals were the Northeast and spring, respectively. The highest CDI mortality rates were seen in the Midwest and winter. Children exhibited different regional and seasonal CDI variations compared with adults and older adults.

Emergence of an outbreak-associated Clostridium difficile variant with increased virulence

The prevalence of Clostridium difficile infections has increased due to the emergence of epidemic variants from diverse genetic lineages. Here we describe the emergence of a novel variant during an outbreak in a Costa Rican hospital that was associated with severe clinical presentations. This C. difficile variant elicited higher white blood cell counts and caused disease in younger patients than did other strains isolated during the outbreak. Furthermore, it had a recurrence rate, a 30-day attributable disease rate, and disease severity as great as those of the epidemic strain NAP1. Pulsed-field gel electrophoresis genotyping indicated that the outbreak strains belong to a previously undescribed variant, designated NAPCR1. Whole-genome sequencing and ribotyping indicated that the NAPCR1 variant belongs to C. difficile ribotype 012 and sequence type 54, as does the reference strain 630. NAPCR1 strains are resistant to fluoroquinolones due to a mutation in gyrA, and they possess an 18-bp deletion in tcdC that is characteristic of the epidemic, evolutionarily distinct, C. difficile NAP1 variant. NAPCR1 genomes contain 10% more predicted genes than strain 630, most of which are of hypothetical function and are present on phages and other mobile genetic elements. The increased virulence of NAPCR1 was confirmed by mortality rates in the hamster model and strong inflammatory responses induced by bacteria-free supernatants in the murine ligated loop model. However, NAPCR1 strains do not synthesize toxin A and toxin B at levels comparable to those in NAP1 strains. Our results suggest that the pathogenic potential of this emerging C. difficile variant is due to the acquisition of hypothetical functions associated with laterally acquired DNA.

Fecal microbiota transplantation (FMT) for Clostridium difficile infection: focus on immunocompromised patients

Clostridium difficile infection (CDI) is an emerging problem worldwide associated with significant morbidity, mortality, recurrence rates and healthcare costs. Immunosuppressed patients, including HIV-seropositive individuals, solid organ transplant recipients, patients with malignancies, hematopoietic stem cell transplant recipients, and patients with inflammatory bowel disease are increasingly recognized as being at higher risk of developing CDI where it may be associated with significant complications, recurrence, and mortality. Fecal microbiota transplantation (FMT) has proven to be an effective and safe procedure for the treatment of recurrent or refractory CDI in immunocompetent patients by restoring the gut microbiota and resistance to further recurrences. During the last two years the first data on FMT in immunocompromised patients began to appear in the medical literature. Herein we summarize the use of FMT for the treatment of CDI with a focus on immunocompromised patients.

Clostridium difficile ribotype 027: relationship to age, detectability of toxins A or B in stool with rapid testing, severe infection, and mortality

BACKGROUND

Clostridium difficile infection (CDI) can cause severe disease and death, especially in older adults. A better understanding of risk factors for adverse outcomes is needed. This study tests the hypotheses that infection with specific ribotypes and presence of stool toxins independently associate with severity and constructs predictive models of adverse outcomes.

METHODS

Cases of non-recurrent CDI were prospectively included after positive stool tests for toxins A and/or B by enzyme immunoassay (EIA) or tcdB by polymerase chain reaction. Outcomes included severe CDI (intensive care unit admission, colectomy, or death attributable to CDI within 30 days of diagnosis) and 30-day all-cause mortality. Adjusted models were developed to test hypotheses and predict outcomes.

RESULTS

In total, 1144 cases were included. The toxin EIA was positive in 37.2% and 35.6% of patients were of age >65 years. One of the 137 unique ribotypes was ribotype 027 (16.2%). Detectable stool toxin did not associate with outcomes. Adjusting for covariates, including age, Ribotype 027 was a significant predictor of severe CDI (90 cases; odds ratio [OR], 1.73; 95% confidence interval [CI], 1.03-2.89; P = .037) and mortality (89 cases; OR, 2.02; 95% CI, 1.19-3.43; P = .009). Concurrent antibiotic use associated with both outcomes. Both multivariable predictive models had excellent performance (area under the curve >0.8).

CONCLUSIONS

Detection of stool toxin A and/or B by EIA does not predict severe CDI or mortality. Infection with ribotype 027 independently predicts severe CDI and mortality. Use of concurrent antibiotics is a potentially modifiable risk factor for severe CDI.

A modified R-type bacteriocin specifically targeting Clostridium difficile prevents colonization of mice without affecting gut microbiota diversity

Clostridium difficile is a leading cause of nosocomial infections worldwide and has become an urgent public health threat requiring immediate attention. Epidemic lineages of the BI/NAP1/027 strain type have emerged and spread through health care systems across the globe over the past decade. Limiting person-to-person transmission and eradicating C. difficile, especially the BI/NAP1/027 strain type, from health care facilities are difficult due to the abundant shedding of spores that are impervious to most interventions. Effective prophylaxis for C. difficile infection (CDI) is lacking. We have genetically modified a contractile R-type bacteriocin (“diffocin”) from C. difficile strain CD4 to kill BI/NAP1/027-type strains for this purpose. The natural receptor binding protein (RBP) responsible for diffocin targeting was replaced with a newly discovered RBP identified within a prophage of a BI/NAP1/027-type target strain by genome mining. The resulting modified diffocins (a.k.a. Avidocin-CDs), Av-CD291.1 and Av-CD291.2, were stable and killed all 16 tested BI/NAP1/027-type strains. Av-CD291.2 administered in drinking water survived passage through the mouse gastrointestinal (GI) tract, did not detectably alter the mouse gut microbiota or disrupt natural colonization resistance to C. difficile or the vancomycin-resistant Enterococcus faecium (VREF), and prevented antibiotic-induced colonization of mice inoculated with BI/NAP1/027-type spores. Given the high incidence and virulence of the pathogen, preventing colonization by BI/NAP1/027-type strains and limiting their transmission could significantly reduce the occurrence of the most severe CDIs. This modified diffocin represents a prototype of an Avidocin-CD platform capable of producing targetable, precision anti-C. difficile agents that can prevent and potentially treat CDIs without disrupting protective indigenous microbiota.

Treatment and prevention strategies for bacterial diseases rely heavily on traditional antibiotics, which impose strong selection for resistance and disrupt protective microbiota. One consequence has been an upsurge of opportunistic pathogens, such as Clostridium difficile, that exploit antibiotic-induced disruptions in gut microbiota to proliferate and cause life-threatening diseases. We have developed alternative agents that utilize contractile bactericidal protein complexes (R-type bacteriocins) to kill specific C. difficile pathogens. Efficacy in a preclinical animal study indicates these molecules warrant further development as potential prophylactic agents to prevent C. difficile infections in humans. Since these agents do not detectably alter the indigenous gut microbiota or colonization resistance in mice, we believe they will be safe to administer as a prophylactic to block transmission in high-risk environments without rendering patients susceptible to enteric infection after cessation of treatment.

The epidemiology of Clostridium difficile infection inside and outside health care institutions

This article describes the global changes in Clostridium difficile epidemiology since the late twentieth century and into the twenty-first century when the new epidemic strain BI/NAP1/027 emerged. The article provides an overview of how understanding of C difficile epidemiology has rapidly evolved since its initial association with colitis in 1974. It also discusses how C difficile has spread across the globe, the role of asymptomatic carriers in disease transmission, the increased recognition of C difficile outside health care settings, the changes in epidemiology of C difficile infection in children, and the risk factors for disease.

Burden of Clostridium difficile infection in the United States

BACKGROUND

The magnitude and scope of Clostridium difficile infection in the United States continue to evolve.

METHODS

In 2011, we performed active population- and laboratory-based surveillance across 10 geographic areas in the United States to identify cases of C. difficile infection (stool specimens positive for C. difficile on either toxin or molecular assay in residents ≥ 1 year of age). Cases were classified as community-associated or health care-associated. In a sample of cases of C. difficile infection, specimens were cultured and isolates underwent molecular typing. We used regression models to calculate estimates of national incidence and total number of infections, first recurrences, and deaths within 30 days after the diagnosis of C. difficile infection.

RESULTS

A total of 15,461 cases of C. difficile infection were identified in the 10 geographic areas; 65.8% were health care-associated, but only 24.2% had onset during hospitalization. After adjustment for predictors of disease incidence, the estimated number of incident C. difficile infections in the United States was 453,000 (95% confidence interval [CI], 397,100 to 508,500). The incidence was estimated to be higher among females (rate ratio, 1.26; 95% CI, 1.25 to 1.27), whites (rate ratio, 1.72; 95% CI, 1.56 to 2.0), and persons 65 years of age or older (rate ratio, 8.65; 95% CI, 8.16 to 9.31). The estimated number of first recurrences of C. difficile infection was 83,000 (95% CI, 57,000 to 108,900), and the estimated number of deaths was 29,300 (95% CI, 16,500 to 42,100). The North American pulsed-field gel electrophoresis type 1 (NAP1) strain was more prevalent among health care-associated infections than among community-associated infections (30.7% vs. 18.8%, P<0.001).

CONCLUSIONS

C. difficile was responsible for almost half a million infections and was associated with approximately 29,000 deaths in 2011. (Funded by the Centers for Disease Control and Prevention.).

The contribution of strains and hosts to outcomes in Clostridium difficile infection

Acquisition of Clostridium difficile spores can be followed by a spectrum of clinical outcomes ranging from asymptomatic transit through the bowel to severe colitis and death. This clinical variability is a product of bacterial virulence and host susceptibility to the pathogen. It is important to identify patients at high risk of poor outcome so that increased monitoring and optimal treatment strategies can be instigated. This article discusses the evidence linking strain type to clinical outcome, including the importance of toxin and nontoxin virulence factors. It reviews host factors and their relationship with C difficile infection susceptibility, recurrence, and mortality.

Clostridium difficile infection: an Australian clinical perspective

The scale of the problem now posed by Clostridium difficile infection (CDI) is becoming frighteningly clear. Since 2001, a dramatic increase in the incidence and severity of CDI has occurred, particularly, in North America, the United Kingdom and Europe, associated with the emergence of a fluoroquinolone-resistant clone known as restriction endonuclease type BI, pulsed field type NAP1 or PCR ribotype 027 (RT027) Clostridium difficile (CD)1–3. CD is now the most commonly identified nosocomial pathogen in the USA4–6 and in 2011 there were approximately 450 000 incident cases of CDI in the USA and 29 300 deaths at day 30 post diagnosis6. Using an estimated attributable mortality rate of 50%, approximately 15 000 deaths due to CDI occurred in the USA in 2011.

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.

Preclinical studies of amixicile, a systemic therapeutic developed for treatment of Clostridium difficile infections that also shows efficacy against Helicobacter pylori

Amixicile shows efficacy in the treatment of Clostridium difficile infections (CDI) in a mouse model, with no recurrence of CDI. Since amixicile selectively inhibits the action of a B vitamin (thiamine pyrophosphate) cofactor of pyruvate:ferredoxin oxidoreductase (PFOR), it may both escape mutation-based drug resistance and spare beneficial probiotic gut bacteria that do not express this enzyme. Amixicile is a water-soluble derivative of nitazoxanide (NTZ), an antiparasitic therapeutic that also shows efficacy against CDI in humans. In comparative studies, amixicile showed no toxicity to hepatocytes at 200 μM (NTZ was toxic above 10 μM); was not metabolized by human, dog, or rat liver microsomes; showed equivalence or superiority to NTZ in cytochrome P450 assays; and did not activate efflux pumps (breast cancer resistance protein, P glycoprotein). A maximum dose (300 mg/kg) of amixicile given by the oral or intraperitoneal route was well tolerated by mice and rats. Plasma exposure (rats) based on the area under the plasma concentration-time curve was 79.3 h · μg/ml (30 mg/kg dose) to 328 h · μg/ml (100 mg/kg dose), the maximum concentration of the drug in serum was 20 μg/ml, the time to the maximum concentration of the drug in serum was 0.5 to 1 h, and the half-life was 5.6 h. Amixicile did not concentrate in mouse feces or adversely affect gut populations of Bacteroides species, Firmicutes, segmented filamentous bacteria, or Lactobacillus species. Systemic bioavailability was demonstrated through eradication of Helicobacter pylori in a mouse infection model. In summary, the efficacy of amixicile in treating CDI and other infections, together with low toxicity, an absence of mutation-based drug resistance, and excellent drug metabolism and pharmacokinetic metrics, suggests a potential for broad application in the treatment of infections caused by PFOR-expressing microbial pathogens in addition to CDI.

Clostridium difficile

Clostridium difficile has re-emerged as a major hospital-acquired infection since 2001. Despite development of polymerase chain reaction-based testing, no single clinical diagnostic test has emerged with sufficient sensitivity, specificity, and turnaround time to be entirely reliable for disease diagnosis. The importance of C difficile acquired outside the hospital environment remains an unknown factor and awaits further epidemiologic investigation. This article discusses the changing epidemiology, clinical presentation, and pathogenesis of C difficile infection and highlights the ongoing challenges of laboratory diagnosis, treatment, and disease relapse.