Clostridium difficile PCR ribotype 027: assessing the risks of further worldwide spread

Treatment of Clostridium difficile infection: recent trial results

Clostridium difficile is a major cause of infection worldwide and is associated with increasing morbidity and mortality in vulnerable patient populations. Metronidazole and oral vancomycin are the currently recommended therapies for the treatment of C. difficile infection (CDI) but are associated with unacceptably high rates of disease recurrence. Novel therapies for the treatment of CDI and prevention of recurrent CDI are urgently needed. Important developments in the treatment of CDI are currently underway and include: novel antibacterial agents with narrower antimicrobial spectra of activity, manipulation of the gut microbiota and enhancement of the host antibody immune response.

Bed occupancy rates and hospital-acquired Clostridium difficile infection: a cohort study

BACKGROUND

An emergent strain (ribotype 027) of Clostridium difficile infection (CDI) has been implicated in epidemics worldwide. Organizational factors such as bed occupancy have been associated with an increased incidence of CDI; however, the data are sparse, and the association has not been widely demonstrated. We investigated the association of bed occupancy and CDI within a large hospital organization in the United Kingdom.

OBJECTIVE

To establish whether bed occupancy rates are a significant risk factor for CDI in the general ward setting.

METHODS

A retrospective cohort study was carried out on data from 2006 to 2008. Univariate and multivariate Cox regression modeling was used to examine the strength and significance of the associations. Variables included patient characteristics, antibiotic policy exposure, case mix, and bed occupancy rates.

RESULTS

A total of 1,589 cases of hospital-acquired CDI were diagnosed (1.7% of admissions), with an overall infection rate of 2.16 per 1,000 patient-days. Median bed occupancy was 93.3% (interquartile range, 83.3%-100%) Univariate and multivariate analyses showed positive and statistically significant associations. In the adjusted model, patients on wards with occupancy rates of 80%-89.9% had rates of CDI that were 56% higher (hazard ratio, 1.56 [95% confidence interval, 1.18-2.04]; P < .001) compared with baseline (0%-69.9% occupancy). CDI rates were 55% higher for patients on wards with maximal bed occupancy (100%).

CONCLUSIONS

There is strong evidence of an association between high bed occupancy and CDI. Without effective interventions at high levels of bed occupancy, the economic benefits sought from reducing bed numbers may be negated by the increased risk of CDI.

Clostridium difficile exposure as an insidious source of infection in healthcare settings: an epidemiological model

BACKGROUND

Clostridium difficile is the leading cause of infectious diarrhea in hospitalized patients. Its epidemiology has shifted in recent years from almost exclusively infecting elderly patients in whom the gut microbiota has been disturbed by antimicrobials, to now also infecting individuals of all age groups with no recent antimicrobial use.

METHODS

A stochastic mathematical model was constructed to simulate the modern epidemiology of C. difficile in a healthcare setting, and, to compare the efficacies of interventions.

RESULTS

Both the rate of colonization and the incidence of symptomatic disease in hospital inpatients were insensitive to antimicrobial stewardship and to the prescription of probiotics to expedite healthy gut microbiota recovery, suggesting these to be ineffective interventions to limit transmission. Comparatively, improving hygiene and sanitation and reducing average length of stay more effectively reduced infection rates. Although the majority of new colonization events are a result of within-hospital ward exposure, simulations demonstrate the importance of imported cases with new admissions.

CONCLUSIONS

By analyzing a wide range of screening sensitivities, we identify a previously ignored source of pathogen importation: although capturing all asymptomatic as well as symptomatic introductions, individuals who are exposed but not yet colonized will be missed by even a perfectly sensitive screen on admission. Empirical studies to measure the duration of this latent period of infection will be critical to assessing C. difficile control strategies. Moreover, identifying the extent to which the exposed category of individual contributes to pathogen importation should be explicitly considered for all infections relevant to healthcare settings.

Nontoxigenic Clostridium difficile protects hamsters against challenge with historic and epidemic strains of toxigenic BI/NAP1/027 C. difficile

Nontoxigenic Clostridium difficile (NTCD) has been shown to prevent fatal C. difficile infection in the hamster model when hamsters are challenged with standard toxigenic C. difficile strains. The purpose of this study was to determine if NTCD can prevent C. difficile infection in the hamster model when hamsters are challenged with restriction endonuclease analysis group BI C. difficile strains. Groups of 10 hamsters were given oral clindamycin, followed on day 2 by 10(6) CFU of spores of NTCD strain M3 or T7, and were challenged on day 5 with 100 CFU of spores of BI1 or BI6. To conserve animals, results for control hamsters challenged with BI1 or BI6 from the present study and controls from previous identical experiments were combined for statistical comparisons. NTCD strains M3 and T7 achieved 100% colonization and were 100% protective against challenge with BI1 (P ≤ 0.001). M3 colonized 9/10 hamsters and protected against BI6 challenge in the colonized hamsters (P = 0.0003). T7 colonized 10/10 hamsters, but following BI6 challenge, cocolonization occurred in 5 hamsters, 4 of which died, for protection of 6/10 animals (P = 0.02). NTCD colonization provides protection against challenge with toxigenic BI group strains. M3 is more effective than T7 in preventing C. difficile infection caused by the BI6 epidemic strain. Prevention of C. difficile infection caused by the epidemic BI6 strain may be more challenging than that of infections caused by historic BI1 and non-BI C. difficile strains.

Bacteriotherapy for the treatment of intestinal dysbiosis caused by Clostridium difficile infection

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Antibiotics damage the intestinal microbiota and disrupt colonization resistance predisposing us to recurrent C. difficile infection (CDI).

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Faecal microbiota transplantation (FMT) is a promising treatment for recurrent C. difficile infection.

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Mixtures of beneficial bacteria known as bacteriotherapy should be developed for treatment of CDI and other diseases linked to dysbiosis in the intestinal microbiota.

Faecal microbiota transplantation (FMT) has been used for more than five decades to treat a variety of intestinal diseases associated with pathological imbalances within the resident microbiota, termed dysbiosis. FMT has been particularly effective for treating patients with recurrent Clostridium difficile infection who are left with few clinical options other than continued antibiotic therapy. Our increasing knowledge of the structure and function of the human intestinal microbiota and C. difficile pathogenesis has led to the understanding that FMT promotes intestinal ecological restoration and highlights the microbiota as a viable therapeutic target. However, the use of undefined faecal samples creates a barrier for widespread clinical use because of safety and aesthetic issues. An emerging concept of bacteriotherapy, the therapeutic use of a defined mixture of harmless, health-associated bacteria, holds promise for the treatment of patients with severe C. difficile infection, and possibly represents a paradigm shift for the treatment of diseases linked to intestinal dysbiosis.

Epidemiology of Clostridium difficile infection in Asia

While Clostridium difficile infection (CDI) has come to prominence as major epidemics have occurred in North America and Europe over the recent decade, awareness and surveillance of CDI in Asia have remained poor. Limited studies performed throughout Asia indicate that CDI is also a significant nosocomial pathogen in this region, but the true prevalence of CDI remains unknown. A lack of regulated antibiotic use in many Asian countries suggests that the prevalence of CDI may be comparatively high. Molecular studies indicate that ribotypes 027 and 078, which have caused significant outbreaks in other regions of the world, are rare in Asia. However, variant toxin A-negative/toxin B-positive strains of ribotype 017 have caused epidemics across several Asian countries. Ribotype smz/018 has caused widespread disease across Japan over the last decade and more recently emerged in Korea. This review summarises current knowledge on CDI in Asian countries.

Challenges for standardization of Clostridium difficile typing methods

Typing of Clostridium difficile facilitates understanding of the epidemiology of the infection. Some evaluations have shown that certain strain types (for example, ribotype 027) are more virulent than others and are associated with worse clinical outcomes. Although restriction endonuclease analysis (REA) and pulsed-field gel electrophoresis have been widely used in the past, PCR ribotyping is the current method of choice for typing of C. difficile. However, global standardization of ribotyping results is urgently needed. Whole-genome sequencing of C. difficile has the potential to provide even greater epidemiologic information than ribotyping.

Emergence of Clostridium difficile infection in tuberculosis patients due to a highly rifampicin-resistant PCR ribotype 046 clone in Poland

Clostridium difficile infection (CDI) is a major cause of nosocomial diarrhea. CDI is known to develop after antibiotic administration, but anti-tuberculosis agents have rarely been implicated. We documented an outbreak caused by a highly rifampicin-resistant C. difficile strain of polymerase chain reaction (PCR) ribotype 046 in patients with active tuberculosis.

Clostridium difficile in foods and animals: history and measures to reduce exposure

Many articles have summarized the changing epidemiology of Clostridium difficile infections (CDI) in humans, but the emerging presence of C. difficile in foods and animals and possible measures to reduce human exposure to this important pathogen have been infrequently addressed. CDIs have traditionally been assumed to be restricted to health-care settings. However, recent molecular studies indicate that this is no longer the case; animals and foods might be involved in the changing epidemiology of CDIs in humans; and genome sequencing is disproving person-to-person transmission in hospitals. Although zoonotic and foodborne transmission have not been confirmed, it is evident that susceptible people can be inadvertently exposed to C. difficile from foods, animals, or their environment. Strains of epidemic clones present in humans are common in companion and food animals, raw meats, poultry products, vegetables, and ready-to-eat foods, including salads. In order to develop science-based prevention strategies, it is critical to understand how C. difficile reaches foods and humans. This review contextualizes the current understanding of CDIs in humans, animals, and foods. Based on available information, we propose a list of educational measures that could reduce the exposure of susceptible people to C. difficile. Enhanced educational efforts and behavior change targeting medical and non-medical personnel are needed.

Emergence and global spread of epidemic healthcare-associated Clostridium difficile

Epidemic Clostridium difficile (027/BI/NAP1) rapidly emerged in the past decade as the leading cause of antibiotic-associated diarrhea worldwide. However, the key moments in the evolutionary history leading to its emergence and subsequent patterns of global spread remain unknown. Here we define the global population structure of C. difficile 027/BI/NAP1 based on whole-genome sequencing and phylogenetic analysis. We demonstrate that two distinct epidemic lineages, FQR1 and FQR2, not one as previously thought, emerged in North America within a relatively short period after acquiring the same fluoroquinolone resistance mutation and a highly-related conjugative transposon. The two epidemic lineages displayed distinct patterns of global spread, and the FQR2 lineage spread more widely leading to healthcare outbreaks in the UK, continental Europe and Australia. Our analysis identifies key genetic changes linked to the rapid trans-continental dissemination of epidemic C. difficile 027/BI/NAP1 and highlights the routes by which it spreads through the global healthcare system.

Targeted restoration of the intestinal microbiota with a simple, defined bacteriotherapy resolves relapsing Clostridium difficile disease in mice

Relapsing C. difficile disease in humans is linked to a pathological imbalance within the intestinal microbiota, termed dysbiosis, which remains poorly understood. We show that mice infected with epidemic C. difficile (genotype 027/BI) develop highly contagious, chronic intestinal disease and persistent dysbiosis characterized by a distinct, simplified microbiota containing opportunistic pathogens and altered metabolite production. Chronic C. difficile 027/BI infection was refractory to vancomycin treatment leading to relapsing disease. In contrast, treatment of C. difficile 027/BI infected mice with feces from healthy mice rapidly restored a diverse, healthy microbiota and resolved C. difficile disease and contagiousness. We used this model to identify a simple mixture of six phylogenetically diverse intestinal bacteria, including novel species, which can re-establish a health-associated microbiota and clear C. difficile 027/BI infection from mice. Thus, targeting a dysbiotic microbiota with a defined mixture of phylogenetically diverse bacteria can trigger major shifts in the microbial community structure that displaces C. difficile and, as a result, resolves disease and contagiousness. Further, we demonstrate a rational approach to harness the therapeutic potential of health-associated microbial communities to treat C. difficile disease and potentially other forms of intestinal dysbiosis.

Pathological imbalances within the intestinal microbiota, termed dysbiosis, are often associated with chronic Clostridium difficile infections in humans. We show that infection of mice with the healthcare pathogen C. difficile leads to persistent intestinal dysbiosis that is associated with chronic disease and a highly contagious state. Using this model we rationally designed a simple mixture of phylogenetically diverse intestinal bacteria that can disrupt intestinal dysbiosis and as a result resolve disease and contagiousness. Our results validate the microbiota as a viable therapeutic target and open the way to rationally design bacteriotherapy to treat chronic C. difficile infections and potentially other forms of persistent dysbiosis.

Clostridium difficile: a European perspective

Clostridium difficile infection is the leading cause of diarrhoea in the industrialised world. First identified in 1935, our knowledge about the clonal population structure, toxins and PCR ribotypes is still increasing. New PCR ribotypes and sequence types are frequently added. In the last decade hypervirulent strains have emerged and been associated with increased severity of disease, high recurrence and significant mortality. Although previously a primarily hospital- or health-care acquired infection, since the 1990's C. difficile infections that are community-acquired have been increasingly reported. Risk factors include hospitalisation, advancing age and prior antibiotic use. The ubiquitous presence of C. difficile in the environment and asymptomatic intestinal colonisation may be important reservoirs for infection and the changing epidemiology of C. difficile infection. Although surveillance in Europe is now a requirement of the European Commission, reporting is not standardised or mandatory. Here we review the current literature, guidelines on diagnosis and treatment and conclude by highlighting a number of areas where further research would increase our understanding.

Efficacy and safety of fidaxomicin compared with oral vancomycin for the treatment of adults with Clostridium difficile-associated diarrhea: data from the OPT-80-003 and OPT-80-004 studies

Clostridium difficile is emerging as one of the most important and devastating pathogens affecting hospitalized populations around the world. The incidence of C. difficile infection is increasing and disease severity is worsening. Thus, an effective alternative to metronidazole and oral vancomycin is urgently needed. Two Phase III trials, OPT-80-003 and OPT-80-004, showed that oral fidaxomicin for 10 days was noninferior compared with treatment with oral vancomycin among adult patients with toxin-positive C. difficile-associated diarrhea (CDAD). Furthermore, fidaxomicin was associated with a lower rate of recurrence of CDAD within 4 weeks of completion of therapy. The safety and tolerability of fidaxomicin was consistent with earlier studies and established that fidaxomicin is an efficacious and well-tolerated treatment option for CDAD. Despite these potential advantages, the cost-effectiveness of this expensive agent remains poorly understood.

Clostridium difficile: novel insights on an incessantly challenging disease

PURPOSE OF REVIEW

This review comprises recent insights on epidemiology, risk factors, diagnostic approaches, pathophysiologic mechanisms, novel treatment options and prevention strategies of Clostridium difficile infection (CDI).

RECENT FINDINGS

Incidence of Clostridium difficile continues to rise and hypervirulent subtypes such as polymerase chain reaction (PCR) ribotype 027 and 078 have emerged worldwide. Children and postpartum women are increasingly recognized as being at risk for development of CDI and community-associated infection is no longer rare. PCR technology may replace complicated two-step test algorithms in the future, because it is rapid, sensitive and specific. Pathophysiological studies have provided evidence that either one of the two exotoxins A and B is important in conferring virulence - the role of binary toxin requires further investigation. Proton pump inhibitors are now established as important risk factors for acquiring, complicating CDI, and developing recurrences. Fidaxomycin, monoclonal antibodies and intestinal microbiota transplantation are promising new treatment options, especially regarding prevention of recurrent disease. Future prevention strategies involve vaccination and novel insights on reservoirs for ongoing transmission, including the food chain.

SUMMARY

Important advances in research on CDI include novel diagnostic approaches, better understanding of the underlying pathophysiological mechanisms of disease and the development of new approaches to treatment.

Using machine-learned bayesian belief networks to predict perioperative risk of clostridium difficile infection following colon surgery

BACKGROUND

Clostridium difficile (C-Diff) infection following colorectal resection is an increasing source of morbidity and mortality.

OBJECTIVE

We sought to determine if machine-learned Bayesian belief networks (ml-BBNs) could preoperatively provide clinicians with postoperative estimates of C-Diff risk.

METHODS

We performed a retrospective modeling of the Nationwide Inpatient Sample (NIS) national registry dataset with independent set validation. The NIS registries for 2005 and 2006 were used for initial model training, and the data from 2007 were used for testing and validation. International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes were used to identify subjects undergoing colon resection and postoperative C-Diff development. The ml-BBNs were trained using a stepwise process. Receiver operating characteristic (ROC) curve analysis was conducted and area under the curve (AUC), positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

From over 24 million admissions, 170,363 undergoing colon resection met the inclusion criteria. Overall, 1.7% developed postoperative C-Diff. Using the ml-BBN to estimate C-Diff risk, model AUC is 0.75. Using only known a priori features, AUC is 0.74. The model has two configurations: a high sensitivity and a high specificity configuration. Sensitivity, specificity, PPV, and NPV are 81.0%, 50.1%, 2.6%, and 99.4% for high sensitivity and 55.4%, 81.3%, 3.5%, and 99.1% for high specificity. C-Diff has 4 first-degree associates that influence the probability of C-Diff development: weight loss, tumor metastases, inflammation/infections, and disease severity.

CONCLUSIONS

Machine-learned BBNs can produce robust estimates of postoperative C-Diff infection, allowing clinicians to identify high-risk patients and potentially implement measures to reduce its incidence or morbidity.

Evidence of in vivo prophage induction during Clostridium difficile infection

Prophages contribute to the evolution and virulence of most bacterial pathogens, but their role in Clostridium difficile is unclear. Here we describe the isolation of four Myoviridae phages, ΦMMP01, ΦMMP02, ΦMMP03, and ΦMMP04, that were recovered as free viral particles in the filter-sterilized stool supernatants of patients suffering from C. difficile infection (CDI). Furthermore, identical prophages were found in the chromosomes of C. difficile isolated from the corresponding fecal samples. We therefore provide, for the first time, evidence of in vivo prophage induction during CDI. We completely sequenced the genomes of ΦMMP02 and ΦMMP04, and bioinformatics analyses did not reveal the presence of virulence factors but underlined the unique character of ΦMMP04. We also studied the mobility of ΦMMP02 and ΦMMP04 prophages in vitro. Both prophages were spontaneously induced, with 4 to 5 log PFU/ml detected in the culture supernatants of the corresponding lysogens. When lysogens were grown in the presence of subinhibitory concentrations of ciprofloxacin, moxifloxacin, levofloxacin, or mitomycin C, the phage titers further increased, reaching 8 to 9 log PFU/ml in the case of ΦMMP04. In summary, our study highlights the extensive genetic diversity and mobility of C. difficile prophages. Moreover, antibiotics known to represent risk factors for CDI, such as quinolones, can stimulate prophage mobility in vitro and probably in vivo as well, which underscores their potential impact on phage-mediated horizontal gene transfer events and the evolution of C. difficile.

Detecting and treating Clostridium difficile infections in patients with inflammatory bowel disease

The prevalence of CDI in patients with IBD has increased over the last decade. The excess morbidity and mortality associated with CDI appears to be greater in patients with IBD than in those without preexisting bowel disease. The risk factors for CDI in IBD and non-IBD populations appear similar; unique IBD-related risk factors are use of maintenance immunosuppression and extent and severity of prior colitis. Nevertheless, a significant proportion of CDI-IBD patients may have the disease without traditional risk factors (ie, antibiotic use, recent hospitalization). The absence of such risk factors must not preclude considering CDI in the differential diagnosis of IBD patients presenting with a disease flare. Vancomycin and metronidazole appear to have similar efficacy with vancomycin being the preferred agent for severe disease. Early surgical consultation is key for improving outcomes of patients with severe disease. Several gaps in research exist; prospective multicenter cohorts of CDI-IBD are essential to improve our understanding of the impact of CDI on IBD patients and define appropriate therapeutic regimens to improve patient outcomes.

Clinical and microbiologic characteristics of tcdA-negative variant Clostridium difficile infections

Background

The tcdA-negative variant (A^-B⁺) of Clostridium difficile is prevalent in East Asian countries. However, the risk factors and clinical characteristics of A^-B⁺C. difficile infections (CDI) are not clearly documented. The objective of this study was to investigate these characteristics.

Methods

From September 2008 through January 2010, the clinical characteristics, medication history and treatment outcomes of CDI patients were recorded prospectively. Toxin characterization and antibiotic susceptibility tests were performed on stool isolates of C. difficile.

Results

During the study period, we identified 22 cases of CDI caused by tcdA-negative tcdB-positive (A^-B⁺) strains and 105 cases caused by tcdA-positive tcdB-positive (A⁺B⁺) strains. There was no significant difference in disease severity or clinical characteristics between the two groups. Previous use of clindamycin and young age were identified as significant risk factors for the acquisition of A^-B⁺ CDI (OR = 4.738, 95% CI 1.48–15.157, p = 0.009 and OR = 0.966, 95% CI 0.935–0.998, p = 0.038, respectively) in logistic regression.

Rates of resistance to clindamycin were 100% and 69.6% in the A^-B⁺ and A⁺B⁺ isolates, respectively (p = 0.006), and the ermB gene was identified in 17 of 21 A^-B⁺ isolates (81%). Resistance to moxifloxacin was also more frequent in the A^-B⁺ than in the A⁺B⁺ isolates (95.2% vs. 63.7%, p = 0.004).

Conclusions

The clinical course of A^-B⁺ CDI is not different from that of A⁺B⁺ CDI. Clindamycin use is a significant risk factor for the acquisition of tcdA-negative variant strains.

Underestimation of Clostridium difficile infection among clinicians: an international survey

The objective of this investigation was to document clinicians' awareness regarding the incidence and severity of Clostridium difficile-associated diarrhea (CDAD). An international electronic survey was conducted among corresponding authors of articles indexed by PubMed and published during the last 10 years in 'Core Clinical Journals'. A total of 1,163 clinicians answered (response rate 59%); most of the responses were submitted from North America (54.6%), Europe (32.2%), and Asia/Pacific (11.6%). Only 2.2% of the participants answered correctly all four questions, while 14.1% answered all questions incorrectly. Regarding each question, 10.8% of the participants correctly estimated current CDAD treatment failure or recurrence rates to be around 40%, 33.4% correctly estimated the ratio of antibiotic-associated colitis attributed to C. difficile to be around 60%, 72.7% correctly responded that almost all antibiotics are associated with CDAD, and 41.7% correctly responded that any patient is at risk for CDAD. Almost half (44.4%) of the respondents considered CDAD to be underestimated. Participants from North America scored higher than those from Europe or Asia/Pacific (p < 0.001). Participants considering CDAD to be overestimated (3.4%) had the lowest mean score of correct answers. Among a clinically diverse international sample of physicians with academic expertise, there was an inadequate level of awareness of the magnitude and clinical importance of CDAD.

Activity of a novel cyclic lipopeptide, CB-183,315, against resistant Clostridium difficile and other Gram-positive aerobic and anaerobic intestinal pathogens

We evaluated the activity of CB-183,315 against Clostridium difficile, including strains that are resistant to fluoroquinolones and metronidazole and with elevated MICs to vancomycin as well as other Gram-positive intestinal pathogens. The MICs of CB-183,315 against all C. difficile isolates were ≤ 1 μg/ml. CB-183,315 had greater activity than vancomycin and metronidazole against C. difficile isolates and was more active than the comparators against vancomycin-resistant enterococcus (VRE). CB-183,315 also had excellent activity against methicillin-resistant Staphylococcus aureus (MRSA), other Clostridium spp., and Peptostreptococcus spp.

Biology of Clostridium difficile: implications for epidemiology and diagnosis

Clostridium difficile is an anaerobic, spore-forming, gram-positive rod that causes a spectrum of antibiotic-associated colitis through the elaboration of two large clostridial toxins and other virulence factors. Since its discovery in 1978 as the agent responsible for pseudomembranous colitis, the organism has continued to evolve into an adaptable, aggressive, hypervirulent strain. Advances in molecular methods and improved animal models have facilitated an understanding of how this organism survives in the environment, adapts to the gastrointestinal tract of animals and humans, and accomplishes its unique pathogenesis. The advances in microbiology have been accompanied by some important clinical observations including increased rates of C. difficile infection, increased virulence, and multiple outbreaks. The major new risk is fluoroquinolone use; there is also an association with proton pump inhibitors and increased recognition of cases in outpatients, pediatric patients, and patients without recent antibiotic use. The combination of more aggressive strains with mobile genomes in a setting of an expanded pool of individuals at risk has refocused attention on and challenged assumptions regarding diagnostic gold standards. Future research is likely to build upon the advancements in phylogenetics to create novel strategies for diagnosis, treatment, and prevention.

Progress toward developing a carbohydrate-conjugate vaccine against Clostridium difficile ribotype 027: synthesis of the cell-surface polysaccharide PS-I repeating unit

Clostridium difficile strain ribotype 027 is a hypervirulent pathogen that is responsible for recent, severe outbreaks of serious nosocomial infections. As a foundation for the development of a preventative carbohydrate-based vaccine, we have synthesized a pentasaccharide cell wall repeating unit from PS-I unique to this strain, by the linear assembly of four monosaccharide building blocks.

Clostridium difficile infection: an update on epidemiology, risk factors, and therapeutic options

PURPOSE OF REVIEW

The incidence and severity of Clostridium difficile infection (CDI) around the world has increased over the past 20 years due to the emergence of hypervirulent strains, increased use and misuse of antibiotics, and the increase of susceptible at-risk populations. Treatments currently available for CDI are inadequate to impede the increasing spread and virulence of the infection, avoid recurrence in chronic patients or prevent infection in at-risk populations.

RECENT FINDINGS

New and promising evidence has been presented during the past year, focusing on two major points: preservation of gut microflora and optimization of immune response to CDI and toxins.

SUMMARY

The review aims to summarize the most recent evidence available on the epidemiology, risk factors and treatment of CDI. New antibiotics with selected action on C. difficile and limited effect on microflora (fidaxomicin) and donor fecal transplantation seem to have a relevant efficacy in treating CDI and reducing its recurrence. The use of selected monoclonal antibodies directed against C. difficile toxins in addition to standard therapy is a new, promising approach for the treatment of recurrent cases. Vaccination could be an additional weapon against CDI. New robust data are needed before recommendations can be made to abandon current treatment based on vancomycin and metronidazole and move toward new frontiers.

Hypervirulent Clostridium difficile PCR-ribotypes exhibit resistance to widely used disinfectants

The increased prevalence of Clostridium difficile infection (CDI) has coincided with enhanced transmissibility and severity of disease, which is often linked to two distinct clonal lineages designated PCR-ribotype 027 and 017 responsible for CDI outbreaks in the USA, Europe and Asia. We assessed sporulation and susceptibility of three PCR-ribotypes; 012, 017 and 027 to four classes of disinfectants; chlorine releasing agents (CRAs), peroxygens, quaternary ammonium compounds (QAC) and biguanides. The 017 PCR-ribotype, showed the highest sporulation frequency under these test conditions. The oxidizing biocides and CRAs were the most efficacious in decontamination of C. difficile vegetative cells and spores, the efficacy of the CRAs were concentration dependent irrespective of PCR-ribotype. However, there were differences observed in the susceptibility of the PCR-ribotypes, independent of the concentrations tested for Virkon®, Newgenn®, Proceine 40® and Hibiscrub®. Whereas, for Steri7® and Biocleanse® the difference observed between the disinfectants were dependent on both PCR-ribotype and concentration. The oxidizing agent Perasafe® was consistently efficacious across all three PCR ribotypes at varying concentrations; with a consistent five Log10 reduction in spore titre. The PCR-ribotype and concentration dependent differences in the efficacy of the disinfectants in this study indicate that disinfectant choice is a factor for llimiting the survival and transmission of C. difficile spores in healthcare settings.

Lack of association between clinical outcome of Clostridium difficile infections, strain type, and virulence-associated phenotypes

Clostridium difficile strain NAP1/027 (North American pulsed-field gel electrophoresis [PFGE] type 1 and PCR ribotype 027 [R027]) has been associated with recent outbreaks in North America and Europe. It has been associated with more severe disease symptoms, higher mortality rates, and greater risk of relapse. This strain is thought to produce more toxins and sporulate to higher levels. However, recent studies suggest that this may not always be the case. The objective of our study was to assess, in a nonoutbreak situation, whether specific strains, such as NAP1/027, were associated with more severe disease symptoms, higher toxin production, and/or greater sporulation in vitro. We isolated and characterized C. difficile strains from 21 patients with mild to moderate, severe, or complicated symptoms of C. difficile infection (CDI). The isolates were characterized by different molecular typing methods, including PCR ribotyping, tandem repeat sequence typing (TRST), and sequencing of the tcdC gene. Fourteen isolates were of PCR ribotype 027 with deletions in tcdC, but no association with severity or clinical outcome was found. We show by immunodot blot detection of toxins with monoclonal antibodies that all R027 isolates produced more TcdA and TcdB than other strains. On the other hand, they consistently produced fewer spores than non-R027 isolates. Taken together, our data suggest that NAP1/027 isolates are not always associated with more severe disease, even though they may produce larger amounts of toxins. Our study also suggests that current assertions regarding the NAP1/027 may not apply to all isolates and that other factors may come into play.

A possible oligosaccharide-conjugate vaccine candidate for Clostridium difficile is antigenic and immunogenic

Nosocomial infections with the Gram-positive pathogen Clostridium difficile pose a major risk for hospitalized patients and result in significant costs to health care systems. Here, we present the chemical synthesis of a PS-II hapten of a cell wall polysaccharide of hypervirulent ribotype 027 of C. difficile. Mice were immunized with a conjugate consisting of the synthetic hexasaccharide and the diphtheria toxoid variant CRM(197). The immunogenicity of the glycan repeating unit was demonstrated by the presence of specific IgG antibodies in the serum of immunized mice. Murine monoclonal antibodies interact with the synthetic hexasaccharide, as determined by microarray analysis. Finally, we found that specific IgA antibodies in the stool of hospital patients infected with C. difficile recognize the synthetic PS-II hexasaccharide hapten.

Clinical Clostridium difficile: clonality and pathogenicity locus diversity

Clostridium difficile infection (CDI) is an important cause of mortality and morbidity in healthcare settings. The major virulence determinants are large clostridial toxins, toxin A (tcdA) and toxin B (tcdB), encoded within the pathogenicity locus (PaLoc). Isolates vary in pathogenicity from hypervirulent PCR-ribotypes 027 and 078 with high mortality, to benign non-toxigenic strains carried asymptomatically. The relative pathogenicity of most toxigenic genotypes is still unclear, but may be influenced by PaLoc genetic variant. This is the largest study of C. difficile molecular epidemiology performed to date, in which a representative collection of recent isolates (n = 1290) from patients with CDI in Oxfordshire, UK, was genotyped by multilocus sequence typing. The population structure was described using NeighborNet and ClonalFrame. Sequence variation within toxin B (tcdB) and its negative regulator (tcdC), was mapped onto the population structure. The 69 Sequence Types (ST) showed evidence for homologous recombination with an effect on genetic diversification four times lower than mutation. Five previously recognised genetic groups or clades persisted, designated 1 to 5, each having a strikingly congruent association with tcdB and tcdC variants. Hypervirulent ST-11 (078) was the only member of clade 5, which was divergent from the other four clades within the MLST loci. However, it was closely related to the other clades within the tcdB and tcdC loci. ST-11 (078) may represent a divergent formerly non-toxigenic strain that acquired the PaLoc (at least) by genetic recombination. This study focused on human clinical isolates collected from a single geographic location, to achieve a uniquely high density of sampling. It sets a baseline of MLST data for future comparative studies investigating genotype virulence potential (using clinical severity data for these isolates), possible reservoirs of human CDI, and the evolutionary origins of hypervirulent strains.

Clostridium difficile isolates with increased sporulation: emergence of PCR ribotype 002 in Hong Kong

We identified a predominant clone of Clostridium difficile PCR ribotype 002, which was associated with an increased sporulation frequency. In 2009, 3,528 stool samples from 2,440 patients were tested for toxigenic C. difficile in a healthcare region in Hong Kong. A total of 345 toxigenic strains from 307 (13.3%) patients were found. Ribotype 002 was the predominant ribotype, which constituted 35 samples from 29 (9.4%) patients. The mean sporulation frequency of ribotype 002 was 20.2%, which was significantly higher than that of the 56 randomly selected ribotypes other than 002 as concurrent controls (3.7%, p < 0.001). Patients carrying toxigenic ribotype 002 were more frequently admitted from an elderly home (p = 0.01) and received more β-lactam antibiotics in the preceding 3 months compared with the controls (p = 0.04) . The identification of toxigenic ribotype 002 in 2009 was temporally related to a significant increase in both the incidence of toxigenic C. difficile from 0.53 to 0.95 per 1,000 admissions (p < 0.001) and the rate of positive detection from 4.17% to 6.28% (p < 0.001) between period 1 (2004–2008) and period 2 (2009). This finding should alert both the physician and the infection control team to the establishment of and possible outbreaks by ribotype 002 in our hospitals, as in the case of ribotype 027.

Clostridium difficile--a moving target

Clostridium difficile has been recognized as a pathogen in humans for over 40 years, but in the past decade the incidence has increased and, more importantly, the clinical presentation and consequences have become more serious, with increased morbidity and mortality. The emergence of a new, more pathogenic strain, BI/NAP1/027, has driven these shifts. Treatment of this disease has been with two antibiotics, metronidazole and vancomycin, but increasing recurrence, not uncommon with C. difficile infections, has prompted research into several alternative therapies. These include a new class of antibiotic (fidaxomicin), a monoclonal antibody, a vaccine, and most recently a biotherapeutic (which, in this case, is a nontoxin-producing strain of C. difficile). The future management of C. difficile infection will probably require a combination of these approaches once we have the data from ongoing studies.

Antimicrobial susceptibilities and molecular epidemiology of clinical isolates of Clostridium difficile in taiwan

The antimicrobial susceptibility and virulence factors of Clostridium difficile clinical isolates in Taiwan have not previously been reported. One hundred and thirteen isolates were collected from two major teaching hospitals in Taiwan from 2001 to 2009. Molecular typing was performed by an automated repetitive extragenic palindromic sequence-based PCR (rep-PCR) method (DiversiLab; Bacterial Barcodes, Inc., Athens, GA) and PCR ribotyping. Detection of tcdA, tcdB, cdtA, and cdtB genes was performed using a multiplex PCR assay, and gyrA and gyrB genes of moxifloxacin-nonsusceptible isolates were sequenced. All isolates were susceptible to vancomycin and metronidazole. Ninety-five (84%) isolates were susceptible to moxifloxacin, and the MIC(90) for nemonoxacin was 4 μg/ml. Tigecycline showed favorable antibacterial activity (MIC(90) of 0.06 μg/ml). Thirteen rep-PCR types were identified as a predominant rep-PCR type (type A; non-North American pulsed-field gel electrophoresis type 1 [NAP1], -NAP7, or -NAP8) accounting for 52.2% (59 isolates). Nine of 18 moxifloxacin-nonsusceptible isolates belonged to the rep-PCR type A. The rep-PCR type A and C isolates were distinct from NAP1 (ribotype 027) and NAP8 (ribotype 078) as determined by PCR ribotyping. Seventy-four (65%) isolates harbored tcdA and tcdB, and 15 (13%) harbored cdtAB encoding binary toxin. Eleven isolates had a gene deletion in tcdC, including a 39-bp deletion (9 isolates) and an 18-bp deletion (2). In conclusion, dissemination of a predominant C. difficile clone in southern and northern Taiwan was noted. However, no NAP1 (ribotype 027) isolate could be discovered in this study.

Clostridium difficile infection: epidemiology, risk factors and management

The epidemiology of Clostridium difficile infection (CDI) has changed over the past decade. There has been a dramatic worldwide increase in its incidence, and new CDI populations are emerging, such as those with community-acquired infection and no previous exposure to antibiotics, children, pregnant women and patients with IBD. Diagnosis of CDI requires identification of C. difficile toxin A or B in diarrheal stool. The accuracy of current diagnostic tests remains inadequate and the optimal diagnostic testing algorithm has not been defined. The first-line agents for CDI treatment are metronidazole and vancomycin, with the latter being the preferred agent in patients with severe disease as it has significantly superior efficacy. The incidence of metronidazole treatment failures has increased, emphasizing the need to find alternative treatment options. Disease recurrence continues to occur in 20-40% of patients and its treatment remains challenging. In patients with CDI who develop fulminant colitis, early surgical consultation is essential. Intravenous immunoglobulin and tigecycline have been used in patients with severe refractory disease but delaying surgery may be associated with worse outcomes. Infection control measures are key to prevent horizontal transmission of infection. Ongoing research into effective treatment protocols and prevention is essential.

Update on Clostridium difficile infection

PURPOSE OF REVIEW

This review summarizes the most recent epidemiological data and advances in research into the pathogenesis, diagnosis and treatment of Clostridium difficile infection (CDI).

RECENT FINDINGS

The epidemiology of CDI has changed with the emergence of hypervirulent strains. CDI rates have increased in the community, in children and in patients with inflammatory bowel disease. Although the North American pulsed-field gel electrophoresis type 1, restriction endonuclease analysis group BI, PCR ribotype 027 (NAP1/BI/027) strain remains prevalent in North America, surveillance suggests that it is decreasing in Europe. A similar strain, PCR ribotype 078, is emerging which is associated with community-associated CDI and has been isolated in animals and food products. The Society for Healthcare Epidemiology of America and the Infectious Diseases Society of America have published new guidelines on the epidemiology, diagnosis, treatment, infection control and environmental management of C. difficile. Several novel therapies for CDI are at different stages of development. There have been promising trial results with fidaxomicin, a novel antibiotic for the treatment of CDI and monoclonal antibodies against toxins A and B, which have been shown to significantly reduce CDI recurrence rates.

SUMMARY

Major advances have been made in our understanding of the spread and pathogenesis of C. difficile and new treatment options are becoming available.