Molecular and microbiological characterization of Clostridium difficile isolates from single, relapse, and reinfection cases

Antibiotic Resistances of Clostridioides difficile

The rapid evolution of antibiotic resistance in Clostridioides difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are a matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances, and most of the epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways or biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

Clostridioides difficile Sporulation

Some members of the Firmicutes phylum, including many members of the human gut microbiota, are able to differentiate a dormant and highly resistant cell type, the endospore (hereinafter spore for simplicity). Spore-formers can colonize virtually any habitat and, because of their resistance to a wide variety of physical and chemical insults, spores can remain viable in the environment for long periods of time. In the anaerobic enteric pathogen Clostridioides difficile the aetiologic agent is the oxygen-resistant spore, while the toxins produced by actively growing cells are the main cause of the disease symptoms. Here, we review the regulatory circuits that govern entry into sporulation. We also cover the role of spores in the infectious cycle of C. difficile in relation to spore structure and function and the main control points along spore morphogenesis.

Clostridioides difficile Infection: A Clinical Review of Pathogenesis, Clinical Considerations, and Treatment Strategies

BACKGROUND

Clostridioides difficile infection (CDI) is a common nosocomial infection. Risk factors for developing CDI include prior hospitalization, being older than 65 years old, antibiotic use, and chronic disease. It is linked with diarrhea and colitis and can vary in severity. It is a major cause of increased morbidity and mortality among hospitalized patients. However, community-acquired CDI is also increasing. Proper diagnosis and determination of severity are crucial for the treatment of CDI. Depending on how severe the CDI is, the patient may endorse different symptoms and physical exam findings. The severity of CDI will determine how aggressively it is treated. Management and treatment: Laboratory studies can be helpful in the diagnosis of CDI. In this regard, common labs include complete blood count, stool assays, and, in certain cases, radiography and endoscopy. Mild-to-moderate colitis is treated with antibiotics, but severe colitis requires a different approach, which may include surgery. Several alternative therapies for CDI exist and have shown promising results. This review will touch upon these therapies, which include fecal transplants, intravenous immunoglobulin, and the use of cholestyramine and tigecycline.

CONCLUSION

Prevention of CDI can be achieved by proper hygiene, vaccinations, and detecting the infection early. Proper hygiene is indeed noted to be one of the best ways to prevent CDI in the hospital setting. Overprescribing antibiotics is also another huge reason why CDI occurs. Proper prescription of antibiotics can also help reduce the chances of acquiring CDI.

Update on Commonly Used Molecular Typing Methods for Clostridioides difficile

This review aims to provide a comprehensive overview of the significant Clostridioides difficile molecular typing techniques currently employed in research and medical communities. The main objectives of this review are to describe the key molecular typing methods utilized in C. difficile studies and to highlight the epidemiological characteristics of the most prevalent strains on a global scale. Geographically distinct regions exhibit distinct strain types of C. difficile, with notable concordance observed among various typing methodologies. The advantages that next-generation sequencing (NGS) offers has changed epidemiology research, enabling high-resolution genomic analyses of this pathogen. NGS platforms offer an unprecedented opportunity to explore the genetic intricacies and evolutionary trajectories of C. difficile strains. It is relevant to acknowledge that novel routes of transmission are continually being unveiled and warrant further investigation, particularly in the context of zoonotic implications and environmental contamination.

Comparison of clinical severity, genotype and toxin gene expression of binary toxin-producing Clostridioides difficile clinical isolates in Japan

The emerging Clostridioides difficile strain BI/NAP1/027 has been reported to be associated with more severe clinical symptoms and higher mortality rates, thought in part due to production of a novel binary toxin alongside conventional A and B toxins. However, recent studies suggest that this may not always be the case. Therefore, the purpose of this report was to investigate the correlation between clinical severity and microbiological characteristics of CDT-producing C. difficile isolates in Japan. Eight Japanese isolates of CDT producing C. difficile were investigated using genotyping, cytotoxic activity assays and toxin gene expression. Correlation with clinical severity was performed retrospectively using the patient record. Three of eight patients were assessed as having severe C. difficile infection (CDI). PCR ribotyping resolved six ribotypes including ribotype 027. No specific genes were identified determining severe compared with non-severe cases. Positive correlation of expression levels of tcdA, tcdB and cdtB were observed although these expression levels were not correlated with cytotoxicity. CDI severity index neither correlated with toxin gene expression level nor cytotoxicity. These data indicate that the possession of the CDT gene and toxin gene expression levels may not relate to C. difficile cytotoxicity or clinical severity.

Soluble Non-Starch Polysaccharides From Plantain (Musa x paradisiaca L.) Diminish Epithelial Impact of Clostridioides difficile

Clostridioides difficile infection (CDI) is a leading cause of antibiotic-associated diarrhoea. Adhesion of this Gram-positive pathogen to the intestinal epithelium is a crucial step in CDI, with recurrence and relapse of disease dependent on epithelial interaction of its endospores. Close proximity, or adhesion of, hypervirulent strains to the intestinal mucosa are also likely to be necessary for the release of C. difficile toxins, which when internalized, result in intestinal epithelial cell rounding, damage, inflammation, loss of barrier function and diarrhoea. Interrupting these C. difficile-epithelium interactions could therefore represent a promising therapeutic strategy to prevent and treat CDI. Intake of dietary fibre is widely recognised as being beneficial for intestinal health, and we have previously shown that soluble non-starch polysaccharides (NSP) from plantain banana (Musa spp.), can block epithelial adhesion and invasion of a number of gut pathogens, such as E. coli and Salmonellae. Here, we assessed the action of plantain NSP, and a range of alternative soluble plant fibres, for inhibitory action on epithelial interactions of C. difficile clinical isolates, purified endospore preparations and toxins. We found that plantain NSP possessed ability to disrupt epithelial adhesion of C. difficile vegetative cells and spores, with inhibitory activity against C. difficile found within the acidic (pectin-rich) polysaccharide component, through interaction with the intestinal epithelium. Similar activity was found with NSP purified from broccoli and leek, although seen to be less potent than NSP from plantain. Whilst plantain NSP could not block the interaction and intracellular action of purified C. difficile toxins, it significantly diminished the epithelial impact of C. difficile, reducing both bacteria and toxin induced inflammation, activation of caspase 3/7 and cytotoxicity in human intestinal cell-line and murine intestinal organoid cultures. Dietary supplementation with soluble NSP from plantain may therefore confer a protective effect in CDI patients by preventing adhesion of C. difficile to the mucosa, i.e. a “contrabiotic” effect, and diminishing its epithelial impact. This suggests that plantain soluble dietary fibre may be a therapeutically effective nutritional product for use in the prevention or treatment of CDI and antibiotic-associated diarrhoea.

Diagnostic deficiencies of C. difficile infection among patients in a tertiary hospital in Saudi Arabia: A laboratory-based case series

Clostridioides difficile infection (CDI) has become a threatening public health problem in the developed world. In the kingdom of Saudi Arabia, prevalence of CDI is still unknown due to limited surveillance protocols and diagnostic resources. We used a two-step procedure to study and confirm C. difficile cases. We also studied toxin profiles of these isolates. Stool samples were collected from symptomatic patients and clinically suspected of CDI for almost 12 months. Isolates were confirmed by culture method followed by 16S rRNA sequencing. Multiplex PCR was performed for the identification of toxin A, toxin B and binary toxin genes and compared to Gene Expert results. Out of the 47 collected samples, 27 were successfully grown on culture media. 18 samples were confirmed as C. difficile by both culture and 16S rRNA sequencing. Interestingly, the rest of the isolates (9 species) belonged to different genera. Our results showed 95% of samples were positive for both toxin A and B (tcdA, tcdB) and all samples exhibited the toxin gene regulator tcdC. All samples were confirmed negative for the binary toxin gene ctdB and 11% of the isolates were positive for ctdA gene. Interestingly, one isolate harbored the binary toxin gene (cdtA ⁺) and tested negative for both toxins A and B. We believe that combining the standard culture method with molecular techniques can make the detection of C. difficile more accurate.

Clostridioides difficile Spore Formation and Germination: New Insights and Opportunities for Intervention

Spore formation and germination are essential for the bacterial pathogen Clostridioides difficile to transmit infection. Despite the importance of these developmental processes to the infection cycle of C. difficile, the molecular mechanisms underlying how this obligate anaerobe forms infectious spores and how these spores germinate to initiate infection were largely unknown until recently. Work in the last decade has revealed that C. difficile uses a distinct mechanism for sensing and transducing germinant signals relative to previously characterized spore formers. The C. difficile spore assembly pathway also exhibits notable differences relative to Bacillus spp., where spore formation has been more extensively studied. For both these processes, factors that are conserved only in C. difficile or the related Peptostreptococcaceae family are employed, and even highly conserved spore proteins can have differential functions or requirements in C. difficile compared to other spore formers. This review summarizes our current understanding of the mechanisms controlling C. difficile spore formation and germination and describes strategies for inhibiting these processes to prevent C. difficile infection and disease recurrence.

What's a Biofilm?-How the Choice of the Biofilm Model Impacts the Protein Inventory of Clostridioides difficile

The anaerobic pathogen Clostridioides difficile is perfectly equipped to survive and persist inside the mammalian intestine. When facing unfavorable conditions C. difficile is able to form highly resistant endospores. Likewise, biofilms are currently discussed as form of persistence. Here a comprehensive proteomics approach was applied to investigate the molecular processes of C. difficile strain 630Δerm underlying biofilm formation. The comparison of the proteome from two different forms of biofilm-like growth, namely aggregate biofilms and colonies on agar plates, revealed major differences in the formation of cell surface proteins, as well as enzymes of its energy and stress metabolism. For instance, while the obtained data suggest that aggregate biofilm cells express both flagella, type IV pili and enzymes required for biosynthesis of cell-surface polysaccharides, the S-layer protein SlpA and most cell wall proteins (CWPs) encoded adjacent to SlpA were detected in significantly lower amounts in aggregate biofilm cells than in colony biofilms. Moreover, the obtained data suggested that aggregate biofilm cells are rather actively growing cells while colony biofilm cells most likely severely suffer from a lack of reductive equivalents what requires induction of the Wood-Ljungdahl pathway and C. difficile’s V-type ATPase to maintain cell homeostasis. In agreement with this, aggregate biofilm cells, in contrast to colony biofilm cells, neither induced toxin nor spore production. Finally, the data revealed that the sigma factor SigL/RpoN and its dependent regulators are noticeably induced in aggregate biofilms suggesting an important role of SigL/RpoN in aggregate biofilm formation.

Antimicrobial resistance in Clostridioides (Clostridium) difficile derived from humans: a systematic review and meta-analysis

Background

Clostridioides (Clostridium) difficile is an important pathogen of healthcare- associated diarrhea, however, an increase in the occurrence of C. difficile infection (CDI) outside hospital settings has been reported. The accumulation of antimicrobial resistance in C. difficile can increase the risk of CDI development and/or its spread. The limited number of antimicrobials for the treatment of CDI is matter of some concern.

Objectives

In order to summarize the data on antimicrobial resistance to C. difficile derived from humans, a systematic review and meta-analysis were performed.

Methods

We searched five bibliographic databases: (MEDLINE [PubMed], Scopus, Embase, Cochrane Library and Web of Science) for studies that focused on antimicrobial susceptibility testing in C. difficile and were published between 1992 and 2019. The weighted pooled resistance (WPR) for each antimicrobial agent was calculated using a random- effects model.

Results

A total of 111 studies were included. The WPR for metronidazole and vancomycin was 1.0% (95% CI 0–3%) and 1% (95% CI 0–2%) for the breakpoint > 2 mg/L and 0% (95% CI 0%) for breakpoint ≥32 μg/ml. Rifampin and tigecycline had a WPRs of 37.0% (95% CI 18–58%) and 1% (95% CI 0–3%), respectively. The WPRs for the other antimicrobials were as follows: ciprofloxacin 95% (95% CI 85–100%), moxifloxacin 32% (95% CI 25–40%), clindamycin 59% (95% CI 53–65%), amoxicillin/clavulanate 0% (0–0%), piperacillin/tazobactam 0% (0–0%) and ceftriaxone 47% (95% CI 29–65%). Tetracycline had a WPR 20% (95% CI 14–27%) and meropenem showed 0% (95% CI 0–1%); resistance to fidaxomicin was reported in one isolate (0.08%).

Conclusion

Resistance to metronidazole, vancomycin, fidaxomicin, meropenem and piperacillin/tazobactam is reported rarely. From the alternative CDI drug treatments, tigecycline had a lower resistance rate than rifampin. The high-risk antimicrobials for CDI development showed a high level of resistance, the highest was seen in the second generation of fluoroquinolones and clindamycin; amoxicillin/clavulanate showed almost no resistance. Tetracycline resistance was present in one fifth of human clinical C. difficile isolates.

Molecular epidemiology of predominant and emerging Clostridioides difficile ribotypes

There has been an increase in the incidence and severity of Clostridioides difficile infection (CDI) worldwide, and strategies to control, monitor, and diminish the associated morbidity and mortality have been developed. Several typing methods have been used for typing of isolates and studying the epidemiology of CDI; serotyping was the first typing method, but then was replaced by pulsed-field gel electrophoresis (PFGE). PCR ribotyping is now the gold standard method; however, multi locus sequence typing (MLST) schemes have been developed. New sequencing technologies have allowed comparing whole bacterial genomes to address genetic relatedness with a high level of resolution and discriminatory power to distinguish between closely related strains. Here, we review the most frequent C. difficile ribotypes reported worldwide, with a focus on their epidemiology and genetic characteristics.

Biological characteristics associated with virulence in Clostridioides difficile ribotype 002 in Hong Kong

Clostridioides difficile infection (CDI) is a common cause of nosocomial diarrhea and can sometimes lead to pseudo-membranous colitis and toxic megacolon. We previously reported that the PCR ribotype 002 was a common C. difficile ribotype in Hong Kong that was associated with increased mortality. In this study, we assessed in vitro bacteriological characteristics and in vivo virulence of ribotype 002 compared to other common ribotypes, including ribotypes 012, 014 and 046. We observed significantly higher toxin A (p < 0.05) and toxin B (p < 0.05) production, sporulation (p < 0.001) and germination rates (p < 0.0001) in ribotype 002 than other common ribotypes. In a murine model of C. difficile infection, ribotype 002 caused significantly more weight loss (p < 0.001) and histological damage (p < 0.001) than other common ribotypes. These findings may have contributed to the higher prevalence and mortality observed, and provided mechanistic insights that can help public surveillance and develop novel therapeutics to combat against this infection.

Clostridioides difficile Spores: Bile Acid Sensors and Trojan Horses of Transmission

The Gram-positive, spore-forming bacterium, Clostridioides difficile is the leading cause of healthcare-associated infections in the United States, although it also causes a significant number of community-acquired infections. C. difficile infections, which range in severity from mild diarrhea to toxic megacolon, cost more to treat than matched infections, with an annual treatment cost of approximately $6 billion for almost half-a-million infections. These high-treatment costs are due to the high rates of C. difficile disease recurrence (>20%) and necessity for special disinfection measures. These complications arise in part because C. difficile makes metabolically dormant spores, which are the major infectious particle of this obligate anaerobe. These seemingly inanimate life forms are inert to antibiotics, resistant to commonly used disinfectants, readily disseminated, and capable of surviving in the environment for a long period of time. However, upon sensing specific bile salts in the vertebrate gut, C. difficile spores transform back into the vegetative cells that are responsible for causing disease. This review discusses how spores are ideal vectors for disease transmission and how antibiotics modulate this process. We also describe the resistance properties of spores and how they create challenges eradicating spores, as well as promote their spread. Lastly, environmental reservoirs of C. difficile spores and strategies for destroying them particularly in health care environments will be discussed.

Antimicrobial Resistance in Clostridium and Brachyspira spp. and Other Anaerobes

This article describes the antimicrobial resistance to date of the most frequently encountered anaerobic bacterial pathogens of animals. The different sections show that antimicrobial resistance can vary depending on the antimicrobial, the anaerobe, and the resistance mechanism. The variability in antimicrobial resistance patterns is also associated with other factors such as geographic region and local antimicrobial usage. On occasion, the same resistance gene was observed in many anaerobes, whereas some were limited to certain anaerobes. This article focuses on antimicrobial resistance data of veterinary origin.

Prevalence and characterization of Clostridioides difficile isolates from retail food products (vegetables and meats) in Japan

The present study aimed to elucidate the prevalence of Clostridioides difficile in Japanese retail food products. For this purpose, retail food samples (242 fresh vegetables and 266 retail meat samples: 89 chicken meat; 28 chicken liver; 200 pork meat; 24 pig liver; 127 beef meat) were collected from 14 supermarkets between 2015 and 2019. C. difficile was isolated from eight (3.3%) fresh vegetable, six (6.7%) chicken meat, one (3.6%) chicken liver, one (0.5%) pork meat, and two (1.6%) beef meat samples; it was not isolated from pig liver. Of these isolates, 35% were toxigenic. All isolates were typable by PCR ribotyping and were resolved into 12 PCR ribotypes. Among these isolates, ribotype 014, which is distributed worldwide including in Japanese clinical cases, was detected among vegetable isolates. Therefore, although the C. difficile contamination rate in Japanese retail foods was low, these sources can be contaminated and could transmit these bacteria to humans.

Prediction of poor outcome in Clostridioides difficile infection: A multicentre external validation of the toxin B amplification cycle

Classification of patients according to their risk of poor outcomes in Clostridioides difficile infection (CDI) would enable implementation of costly new treatment options in a subset of patients at higher risk of poor outcome. In a previous study, we found that low toxin B amplification cycle thresholds (C_t) were independently associated with poor outcome CDI. Our objective was to perform a multicentre external validation of a PCR-toxin B C_t as a marker of poor outcome CDI. We carried out a multicentre study (14 hospitals) in which the characteristics and outcome of patients with CDI were evaluated. A subanalysis of the results of the amplification curve of real-time PCR gene toxin B (XpertTM C. difficile) was performed. A total of 223 patients were included. The median age was 73.0 years, 50.2% were female, and the median Charlson index was 3.0. The comparison of poor outcome and non-poor outcome CDI episodes revealed, respectively, the following results: median age (years), 77.0 vs 72.0 (p = 0.009); patients from nursing homes, 24.4% vs 10.8% (p = 0.039); median leukocytes (cells/μl), 10,740.0 vs 8795.0 (p = 0.026); and median PCR-toxin B C_t, 23.3 vs 25.4 (p = 0.004). Multivariate analysis showed that a PCR-toxin B C_t cut-off <23.5 was significantly and independently associated with poor outcome CDI (p = 0.002; OR, 3.371; 95%CI, 1.565-7.264). This variable correctly classified 68.5% of patients. The use of this microbiological marker could facilitate early selection of patients who are at higher risk of poor outcome and are more likely to benefit from newer and more costly therapeutic options.

The CspC pseudoprotease regulates germination of Clostridioides difficile spores in response to multiple environmental signals

The gastrointestinal pathogen, Clostridioides difficile, initiates infection when its metabolically dormant spore form germinates in the mammalian gut. While most spore-forming bacteria use transmembrane germinant receptors to sense nutrient germinants, C. difficile is thought to use the soluble pseudoprotease, CspC, to detect bile acid germinants. To gain insight into CspC's unique mechanism of action, we solved its crystal structure. Guided by this structure, we identified CspC mutations that confer either hypo- or hyper-sensitivity to bile acid germinant. Surprisingly, hyper-sensitive CspC variants exhibited bile acid-independent germination as well as increased sensitivity to amino acid and/or calcium co-germinants. Since mutations in specific residues altered CspC's responsiveness to these different signals, CspC plays a critical role in regulating C. difficile spore germination in response to multiple environmental signals. Taken together, these studies implicate CspC as being intimately involved in the detection of distinct classes of co-germinants in addition to bile acids and thus raises the possibility that CspC functions as a signaling node rather than a ligand-binding receptor.

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.

Characterization of the virulence of a non-RT027, non-RT078 and binary toxin-positive Clostridium difficile strain associated with severe diarrhea

The expression of the Clostridium difficile binary toxin CDT is generally observed in the RT027 (ST1) and RT078 (ST11) C. difficile isolates, which are associated with severe C. difficile infection (CDI). However, we recently reported that the non-RT027 and non-RT078 C. difficile strain LC693 (TcdA⁺TcdB⁺ CDT⁺, ST201) caused severe diarrhea in a patient in Xiangya Hospital in China. C.difficile LC693 is a member of Clade 3, and in this study, we identified LC693 as RT871 and compared its virulence and pathogenicity to those of C.difficile R20291 (TcdA⁺TcdB⁺CDT⁺, ST1/RT027), UK6 (TcdA⁺TcdB⁺CDT⁺, ST35/RT027), CD630 (TcdA⁺TcdB⁺CDT⁻, ST54, RT012), and 1379 (TcdA⁺TcdB⁺CDT⁻, ST54/RT012), with strain 1379 being an epidemic C.difficile isolate from the same hospital. LC693 displayed a higher sporulation rate than R20291, CD630 or strain 1379. LC693 was comparable to R20291 with respect to spore germination, motility, and biofilm formation, but showed a faster germination rate, higher motility and a higher biofilm formation capability compared to CD630 and strain 1379. The adherence of spores to human gut epithelial cells was similar for all strains.The total toxin release of LC693 was lower than that of R20291, but higher than that of CD630 and strain 1379. Finally, in a mouse model of CDI, LC693 was capable of causing moderate to severe disease. Our findings demonstrate the pathogenicity of non-RT027 and non-RT078 binary toxin-positive C. difficile strains. Furthermore, our data indicate that LC693 may be more virulent than strain 1379, an epidemic strain from the same hospital, and provide the first phenotypic characterization of a non-RT027 and non-RT078 binary toxin-positive ST201 isolate.

Molecular epidemiologic study of Clostridium difficile infections in university hospitals: Results of a nationwide study in Japan

We conducted a nationwide molecular epidemiological study of Clostridium difficile infection (CDI) in Japan investigated the correlation between the presence of binary toxin genes and CDI severity. This is the first report on molecular epidemiological analyses for CDI in multiple university hospitals in Japan, to our knowledge. We examined 124,484 hospitalized patients in 25 national and public university hospitals in Japan between December 2013 and March 2014, investigating antimicrobial susceptibilities and toxin-related genes for C. difficile isolates from stools. Epidemiological genetic typing was performed by PCR-ribotyping and repetitive sequence-based (rep)-PCR to examine the genetic similarities. The results detected toxin A-positive, toxin B-positive, binary toxin-negative (A⁺B⁺CDT^-) detected from 135 isolates (80.8%) and toxin A-negative, toxin B-positive, binary toxin-negative (A^-B⁺CDT^-) in 23 (13.8%). Toxin A-positive, toxin B-positive, and binary toxin-positive (A⁺B⁺CDT⁺) were seen in 9 isolates (5.4%). Vancomycin (n = 81, 37.7%) or metronidazole (n = 88, 40.9%) therapies were undertaken in analyzed cases. Ribotypes detected from isolates were 017/subgroup 1, 070, 078, 126, 176, 449, 475/subgroup 1, 499, 451, 566 and newtypes. Rep-PCR classified 167 isolates into 28 cluster groups including 2-15 isolates. In addition, 2 pairs of strains isolated from different institutions belonged to the same clusters. Seven out of 9 (77.8%) of the patients with binary toxin producing strains had "mild to moderate" outcome in evaluated symptoms. In conclusion, we found that binary toxin did not show regional specificity and had no relevance to severity of CDI.

Establishment of an Endogenous Clostridium difficile Rat Infection Model and Evaluation of the Effects of Clostridium butyricum MIYAIRI 588 Probiotic Strain

Clostridium difficile is well known as an agent responsible for pseudomembranous colitis and antibiotic-associated diarrhea. The hamster model utilizing an oral route for infection of C. difficile has been considered to be the standard model for analysis of C. difficile infection (CDI) but this model exhibits differences to human CDI, most notably as most hamsters die without exhibiting diarrhea. Therefore, we attempted to develop a new non-lethal and diarrheal rat CDI model caused by endogenous C. difficile using metronidazole (MNZ) and egg white. In addition, the effects of probiotic strain Clostridium butyricum MIYAIRI 588 (CBM) on CDI were examined using this model. Syrian Golden hamsters received clindamycin phosphate orally at 30 mg/kg on 5 days before challenge with either C. difficile VPI10463 (hypertoxigenic strain) or KY34 (low toxigenic clinical isolate). Mortality and the presence of diarrhea were observed twice a day for the duration of the experiment. Wistar rats received 10% egg white dissolved in drinking water for 1 week ad libitum following intramuscular administration of 200 mg/kg MNZ twice a day for 3 days. Diarrhea score was determined for each day and fecal water content, biotin concentration, and cytotoxin titer in feces were examined. More than 70% of hamsters orally infected with C. difficile died without exhibiting diarrhea regardless of toxigenicity of strain. The rats receiving egg white after MNZ administration developed diarrhea due to overgrowth of endogenous C. difficile. This CDI model is non-lethal and diarrheal, and some rats in this model were spontaneously cured. The incidence of diarrhea was significantly decreased in C. butyricum treated rats. These results indicate that the CDI model using egg white and MNZ has potentially better similarity to human CDI, and implies that treatment with C. butyricum may reduce the risk of CDI.

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

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

Clostridium difficile Infections: A Global Overview of Drug Sensitivity and Resistance Mechanisms

Clostridium difficile (C. difficile) is the most prevalent causative pathogen of healthcare-associated diarrhea. Notably, over the past 10 years, the number of Clostridium difficile outbreaks has increased with the rate of morbidity and mortality. The occurrence and spread of C. difficile strains that are resistant to multiple antimicrobial drugs complicate prevention as well as potential treatment options. Most C. difficile isolates are still susceptible to metronidazole and vancomycin. Incidences of C. difficile resistance to other antimicrobial drugs have also been reported. Most of the antibiotics correlated with C. difficile infection (CDI), such as ampicillin, amoxicillin, cephalosporins, clindamycin, and fluoroquinolones, continue to be associated with the highest risk for CDI. Still, the detailed mechanism of resistance to metronidazole or vancomycin is not clear. Alternation in the target sites of the antibiotics is the main mechanism of erythromycin, fluoroquinolone, and rifamycin resistance in C. difficile. In this review, different antimicrobial agents are discussed and C. difficile resistance patterns and their mechanism of survival are summarized.

The Epidemiology of Clostridium difficile Infection in Japan: A Systematic Review

Abstract

To increase understanding of the epidemiology, risks, consequences and resource utilization of Clostridium difficile infection (CDI) in Japan, a systematic literature review was undertaken of relevant publications from January 2006 to November 2017. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and methods, 55 articles met the criteria for full review. The majority (58%) of studies were from a single site, with the most recent data from 2015. The incidence, reported prevalence and recurrence rate of CDI in Japan were 0.8–4.71/10,000 patient-days, 0.3–5.5/1000 patients and 3.3–27.3%, respectively, and varied according to setting, population, CDI definition and detection method. Most C. difficile isolates associated with CDI in Japan were toxin A+B+, with a low level of C. difficile binary toxin-positive (CDT+) strains (0–6.8% reported across studies). The most common C. difficile PCR ribotypes associated with infection in Japan were smz/018, 002, 052 and 369. Data regarding the impact of CDI on length of hospital stay were limited. Reported all-cause mortality in patients with CDI ranged from 3.4 to 15.1% between 2007 and 2013. Two studies assessed risk factors for CDI recurrence, identifying malignant disease, intensive care unit hospitalization and use of proton pump inhibitors as factors increasing the risk of initial and/or recurrent CDI. No study analyzed initial CDI treatment in relation to recurrence. More comprehensive surveillance and coordinated studies are needed to map trends, understand risk factors, and recognize the extent and impact of CDI in Japanese patients.

Funding

Astellas Pharma, Inc.

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Antibiotic Resistances of Clostridium difficile

The rapid evolution of antibiotic resistance in Clostridium difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances and most of epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways and biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, recent data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

Revisiting the Role of Csp Family Proteins in Regulating Clostridium difficile Spore Germination

Clostridium difficile causes considerable health care-associated gastrointestinal disease that is transmitted by its metabolically dormant spore form. Upon entering the gut, C. difficile spores germinate and outgrow to produce vegetative cells that release disease-causing toxins. C. difficile spore germination depends on the Csp family of (pseudo)proteases and the cortex hydrolase SleC. The CspC pseudoprotease functions as a bile salt germinant receptor that activates the protease CspB, which in turn proteolytically activates the SleC zymogen. Active SleC degrades the protective cortex layer, allowing spores to outgrow and resume metabolism. We previously showed that the CspA pseudoprotease domain, which is initially produced as a fusion to CspB, controls the incorporation of the CspC germinant receptor in mature spores. However, study of the individual Csp proteins has been complicated by the polar effects of TargeTron-based gene disruption on the cspBA-cspC operon. To overcome these limitations, we have used pyrE-based allelic exchange to create individual deletions of the regions encoding CspB, CspA, CspBA, and CspC in strain 630Δerm Our results indicate that stable CspA levels in sporulating cells depend on CspB and confirm that CspA maximizes CspC incorporation into spores. Interestingly, we observed that csp and sleC mutants spontaneously germinate more frequently in 630Δerm than equivalent mutants in the JIR8094 and UK1 strain backgrounds. Analyses of this phenomenon suggest that only a subpopulation of C. difficile 630Δerm spores can spontaneously germinate, in contrast with Bacillus subtilis spores. We also show that C. difficile clinical isolates that encode truncated CspBA variants have sequencing errors that actually produce full-length CspBA.IMPORTANCEClostridium difficile is a leading cause of health care-associated infections. Initiation of C. difficile infection depends on spore germination, a process controlled by Csp family (pseudo)proteases. The CspC pseudoprotease is a germinant receptor that senses bile salts and activates the CspB protease, which activates a hydrolase required for germination. Previous work implicated the CspA pseudoprotease in controlling CspC incorporation into spores but relied on plasmid-based overexpression. Here we have used allelic exchange to study the functions of CspB and CspA. We determined that CspA production and/or stability depends on CspB and confirmed that CspA maximizes CspC incorporation into spores. Our data also suggest that a subpopulation of C. difficile spores spontaneously germinates in the absence of bile salt germinants and/or Csp proteins.

Clinical, epidemiological and microbiological characteristics of relapse and re-infection in Clostridium difficile infection

Recurrent diarrhea is a common complication of Clostridium difficile infection (CDI). Recurrent CDI (r-CDI) may be produced by the persistence of spores (relapse) or by the acquisition of a new strain (reinfection). In this study, we analyze epidemiological, clinical, microbiological and laboratory data from patients with r-CDI, relapse, and reinfection-CDI over 5 years and compared with a control group (non r-CDI). Among 60 patients with r-CDI, 36 patients had stool samples collected from two or more episodes, which were molecularly analyzed. Based on ribotyping, 63.9% of the samples were relapse, and 36.1% reinfection. In a multivariable logistic regression analysis, previous antibiotic exposure was found to be a risk factor for r-CDI (OR: 2.23; 95% CI: 1.0-4.9; p = 0.04). Patients with relapse had previous antibiotic exposure more frequently than did patients with reinfection (p = 0.03), and patients with reinfection suffered more frequently from chronic liver disease (p = 0.02) than did relapse patients. Relapse patients compared with the control group had a higher percentage of previous antibiotic exposure, although the difference was statistically no significant (73.9% vs. 91.3 p = 0.06). No significant differences for the selected variables were observed between the reinfection and control groups, although we observed a higher percentage of patients with chronic liver disease (30.8% vs 13.3%; p = 0.08). All isolates were sensitive to metronidazole and vancomycin. No significant differences in antibiotic susceptibility were found between the different groups. Sporulation and germination frequency of r-CDI were higher than non r-CDI (p = 0.02 and p < 0.01, respectively). Nevertheless, there were statistically not significant differences between the relapse and reinfection groups. Both frequencies were compared between the first and second episode of CDI for the relapse and reinfection groups, but differences were not observed to be statistically significant. In conclusion, our study showed that the recurrence of CDI was associated with antibiotic use and sporulation/germination frequency, regardless of relapse or reinfection. The use of antibiotics would produce a dysbiosis and favor the persistence of the C. difficile spores and relapse. A possible alteration of the intestinal microbiota and the bile salts produced by chronic liver disease could favor reinfection.

An in silico evaluation of treatment regimens for recurrent Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) is a significant nosocomial infection worldwide, that recurs in as many as 35% of infections. Risk of CDI recurrence varies by ribotype, which also vary in sporulation and germination rates. Whether sporulation/germination mediate risk of recurrence and effectiveness of treatment of recurring CDI remains unclear. We aim to assess the role of sporulation/germination patterns on risk of recurrence, and the relative effectiveness of the recommended tapered/pulsing regimens using an in silico model.

METHODS

We created a compartmental in-host mathematical model of CDI, composed of vegetative cells, toxins, and spores, to explore whether sporulation and germination have an impact on recurrence rates. We also simulated the effectiveness of three tapered/pulsed vancomycin regimens by ribotype.

RESULTS

Simulations underscored the importance of sporulation/germination patterns in determining pathogenicity and transmission. All recommended regimens for recurring CDI tested were effective in reducing risk of an additional recurrence. Most modified regimens were still effective even after reducing the duration or dosage of vancomycin. However, the effectiveness of treatment varied by ribotype.

CONCLUSION

Current CDI vancomycin regimen for treating recurrent cases should be studied further to better balance associated risks and benefits.

Clinical, immunological and microbiological predictors of poor outcome in Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) causes increased morbidity and mortality. Clinical data cannot clearly predict poor CDI outcome. Data on the value of microbiological predictors is scarce.

OBJECTIVE

To identify early predictors of poor outcome of CDI.

METHODS

We prospectively included patients with CDI aged >2years. Clinical, immunological (Toxin B IgG/Ig A and Toxin A IgG/Ig A), microbiological factors (bacterial load, toxin quantification, sporulation, germination, and metronidazole susceptibility) were evaluated to identify early independent predictors of poor outcome.

RESULTS

We identified 204 cases of CDI; outcome was poor in 22.1%. Advanced age, presence of comorbidities, leukocytosis and high toxigenic C. difficile load were independently associated with poor outcome. We could not demonstrate this correlation for antitoxin antibodies.

CONCLUSION

We identified high bacterial load as a microbiological predictor of poor outcome. We propose this factor to be included in combined clinical and microbiological prediction rules of poor outcome in CDI.

A Clostridium difficile-Specific, Gel-Forming Protein Required for Optimal Spore Germination

Clostridium difficile is a Gram-positive spore-forming obligate anaerobe that is a leading cause of antibiotic-associated diarrhea worldwide. In order for C. difficile to initiate infection, its aerotolerant spore form must germinate in the gut of mammalian hosts. While almost all spore-forming organisms use transmembrane germinant receptors to trigger germination, C. difficile uses the pseudoprotease CspC to sense bile salt germinants. CspC activates the related subtilisin-like protease CspB, which then proteolytically activates the cortex hydrolase SleC. Activated SleC degrades the protective spore cortex layer, a step that is essential for germination to proceed. Since CspC incorporation into spores also depends on CspA, a related pseudoprotease domain, Csp family proteins play a critical role in germination. However, how Csps are incorporated into spores remains unknown. In this study, we demonstrate that incorporation of the CspC, CspB, and CspA germination regulators into spores depends on CD0311 (renamed GerG), a previously uncharacterized hypothetical protein. The reduced levels of Csps in gerG spores correlate with reduced responsiveness to bile salt germinants and increased germination heterogeneity in single-spore germination assays. Interestingly, asparagine-rich repeat sequences in GerG’s central region facilitate spontaneous gel formation in vitro even though they are dispensable for GerG-mediated control of germination. Since GerG is found exclusively in C. difficile, our results suggest that exploiting GerG function could represent a promising avenue for developing C. difficile-specific anti-infective therapies.

The spore-forming bacterium Clostridium difficile is a leading cause of health care-associated infections. While a subset of antibiotics can treat C. difficile infections (CDIs), the primary determinant of CDI disease susceptibility is prior antibiotic exposure, since it reduces the colonization resistance conferred by a diverse microflora. Thus, therapies that minimize perturbations to the gut microbiome should be more effective at reducing CDIs and their recurrence, the main source of disease complications. Given that spore germination is essential for C. difficile to initiate infection and that C. difficile uses a unique pathway to initiate germination, methods that inhibit distinct elements of germination could selectively prevent C. difficile disease recurrence. Here, we identify GerG as a C. difficile-specific protein that controls the incorporation of germinant signaling proteins into spores. Since gerG mutant spores exhibit germination defects and are less responsive to germinant, GerG may represent a promising target for developing therapeutics against CDI.

The incidence and drug resistance of Clostridium difficile infection in Mainland China: a systematic review and meta-analysis

It has been widely reported that the incidence and severity of Clostridium difficile infection (CDI) have increased dramatically in North America and Europe. However, little is known about CDI in Mainland China. In this study, we aimed to investigate the incidence of CDI and the main epidemic and drug-resistant strains of C. difficile in Mainland China through meta-analysis of related studies published after the year 2010. A total of 51 eligible studies were included. The pooled incidence of toxigenic C. difficile among patients with diarrhoea was 14% (95% CI = 12–16%). In Mainland China, ST-37 and ST-3 were the most prevalent strains; fortunately, hypervirulent strains, such as ST-1 (BI/NAP1/027) and ST-11 (RT 078), have only occurred sporadically to date. The rates of C. difficile resistance to ciprofloxacin (98.3%; 95% CI = 96.9–99.7%), clindamycin (81.7%; 95% CI = 76.1–87.3%) and erythromycin (80.2%; 95% CI = 73.5–86.9%) are higher than in other counties; however, none of the C. difficile isolates reported in Mainland China were resistant to metronidazole (n/N = 0/960), vancomycin (n/N = 0/960), tigecycline (n/N = 0/41) or piperacillin/tazobactam(n/N = 0/288).

Predominance of Clostridium difficile Ribotypes 017 and 078 among Toxigenic Clinical Isolates in Southern Taiwan

Ribotypes and toxin genotypes of clinical C. difficile isolates in Taiwan are rarely reported. A prospective surveillance study from January 2011 to January 2013 was conducted at the medical wards of a district hospital in southern Taiwan. Of the first toxigenic isolates from 120 patients, 68 (56.7%) of 120 isolates possessed both tcdA and tcdB. Of 52 (43.3%) with tcdB and truncated tcdA (tcdA-/tcdB+), all were ribotype 017 and none had binary toxin or tcdC deletion. Eighteen (15%) toxigenic isolates harbored binary toxins (cdtA and cdtB) and all had tcdC deletion, including Δ39 (C184T) deletion (14 isolates), Δ18 in-frame deletion (3 isolates), and Δ18 (Δ117A) deletion (1 isolate). Eleven of 14 isolates with Δ39 (C184T) deletion belonged to the ribotype 078 family, including ribotype 127 (6 isolates), ribotype 126 (4 isolates), and ribotype 078 (1 isolate). Among 8 patients with consecutive C. difficile isolates, these isolates from 6 (75%) patients were identical, irrespective of the presence or absence of diarrhea, suggestive of persistent fecal carriage or colonization. In conclusion in southern Taiwan, ribotype 017 isolates with a tcdA-/tcdB+ genotype were not uncommon and of C. difficile isolates with binary toxin, the ribotype 078 family was predominant.

Determining the cause of recurrent Clostridium difficile infection using whole genome sequencing

Understanding the contribution of relapse and reinfection to recurrent Clostridium difficile infection (CDI) has implications for therapy and infection prevention, respectively. We used whole genome sequencing to determine the relation of C. difficile strains isolated from patients with recurrent CDI at an academic medical center in the United States. Thirty-five toxigenic C. difficile isolates from 16 patients with 19 recurrent CDI episodes with median time of 53.5days (range, 13-362) between episodes were whole genome sequenced on the Illumina MiSeq platform. In 84% (16) of recurrences, the cause of recurrence was relapse with prior strain of C. difficile. In 16% (3) of recurrent episodes, reinfection with a new strain of C. difficile was the cause. In conclusion, the majority of CDI recurrences at our institution were due to infection with the same strain rather than infection with a new strain.

A case of multiple recurrence of Clostridium difficile infection with severe hematochezia in an immunocompromised host

Clostridium difficile infection (CDI) is increasing in incidence and severity. Clinically, diarrhea frequently occurs, but severe hematochezia is rarely seen with CDI. We describe here a hematopoietic stem cell transplantation (HSCT) recipient who experienced life-threatening gastrointestinal bleeding due to severe CDI. Subsequent stool surveillance and molecular typing observed the patient who had two episodes of recurrence with a new strain of C. difficile distinct from the initial infection. We analyze C. difficile strains obtained from the patient, and also discuss the diagnosis and treatment of this case.

Clostridium difficile recurrences in Stockholm

Sixty-eight hospital-admitted patients with a first episode of Clostridium difficile infection (CDI) were included and followed up during 1 year. Faeces samples were collected at 1, 2, 6 and 12 months after inclusion and analyzed for the presence of C. difficile toxin B, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped and the MICs of the isolates were determined against eight antimicrobial agents. In 68 patients initially included, antibiotics, clinical signs and co-morbidities were analyzed and 56 were evaluable for recurrences. The mean number of different antibiotics given during 3 months prior to inclusion was 2.6 (range 0-6). Six patients had not received any antibiotics and three of them had diagnosed inflammatory bowel disease. Thirty-two patients (57%) had either a microbiological or clinical recurrence, 16 of whom had clinical recurrences that were confirmed microbiologically (13, 23%) or unconfirmed by culture (3, 5%). Twenty-nine patients were positive in at least one of the follow-up tests, 16 had the same ribotype in follow-up tests, i.e. relapse, and 13 a different ribotype, i.e., reinfection. Most common ribotypes were 078/126, 020, 023, 026, 014/077, 001 and 005. No strain of ribotype 027 was found. Strains ribotype 078/126 and 023 were positive for binary toxin and were the strains most prone to cause recurrence. All strains were sensitive to vancomycin and metronidazole. Patients with recurrences were significantly older (p = 0.02) and all patients had a high burden of comorbidities, which could explain the high fatality rate, 26 (38%) patients died during the 1-year follow-up.

Recent advances in the understanding of antibiotic resistance in Clostridium difficile infection

Clostridium difficile epidemiology has changed in recent years, with the emergence of highly virulent types associated with severe infections, high rates of recurrences and mortality. Antibiotic resistance plays an important role in driving these epidemiological changes and the emergence of new types. While clindamycin resistance was driving historical endemic types, new types are associated with resistance to fluoroquinolones. Furthermore, resistance to multiple antibiotics is a common feature of the newly emergent strains and, in general, of many epidemic isolates. A reduced susceptibility to antibiotics used for C. difficile infection (CDI) treatment, in particular to metronidazole, has recently been described in several studies. Furthermore, an increased number of strains show resistance to rifamycins, used for the treatment of relapsing CDI. Several mechanisms of resistance have been identified in C. difficile, including acquisition of genetic elements and alterations of the antibiotic target sites. The C. difficile genome contains a plethora of mobile genetic elements, many of them involved in antibiotic resistance. Transfer of genetic elements among C. difficile strains or between C. difficile and other bacterial species can occur through different mechanisms that facilitate their spread. Investigations of the fitness cost in C. difficile indicate that both genetic elements and mutations in the molecular targets of antibiotics can be maintained regardless of the burden imposed on fitness, suggesting that resistances may persist in the C. difficile population also in absence of antibiotic selective pressure. The rapid evolution of antibiotic resistance and its composite nature complicate strategies in the treatment and prevention of CDI. The rapid identification of new phenotypic and genotypic traits, the implementation of effective antimicrobial stewardship and infection control programs, and the development of alternative therapies are needed to prevent and contain the spread of resistance and to ensure an efficacious therapy for CDI.

Toxin B PCR cycle threshold as a predictor of poor outcome of Clostridium difficile infection: a derivation and validation cohort study

OBJECTIVES

Prediction of patients with poor outcome is necessary in order to plan the proper management of Clostridium difficile infection (CDI); however, clinical criteria are insufficient. In a previous study, we observed that high toxigenic C. difficile cfu stool counts at diagnosis were associated with a poor outcome. Our objective was to investigate the role of the PCR toxin B amplification cycle threshold (Ct) in the prediction of CDI poor outcome and to derive and validate a high-risk prediction rule using this marker.

METHODS

We prospectively included patients with CDI (derivation cohort, January 2013 to June 2014; and validation cohort, December 2014 to May 2015), who were followed for at least 2 months after their last episode/recurrence. All samples were tested with Xpert™ C. difficile.

RESULTS

For the derivation cohort (n = 129) toxin B Ct was independently associated with poor outcome (P < 0.001). The receiver operating characteristic (ROC) curve yielded an AUC of 0.816. Using a cut-off of <23.5 cycles for high risk of poor outcome, the diagnostic accuracy was 81.4%, the sensitivity was 46.5% (95% CI 32.5-61.1) and the specificity was 98.8% (95% CI 93.7-99.8). For the validation cohort (n = 170), the diagnostic accuracy was 81.8%, the sensitivity was 88.4% (95% CI 75.5-94.9) and the specificity was 79.5% (95% CI 71.7-85.6). The ROC curve yielded an AUC of 0.857.

CONCLUSIONS

Low toxin B Ct values from samples collected at the initial moment of diagnosis appears to be a strong marker for poor outcome. This available test may identify, at an early stage, patients who are at higher risk of a poor outcome CDI.

Predominance of Clostridium difficile ribotypes 012, 027 and 046 in a university hospital in Chile, 2012

In a 1-year survey at a university hospital we found that 20·6% (81/392) of patients with antibiotic associated diarrohea where positive for C. difficile. The most common PCR ribotypes were 012 (14·8%), 027 (12·3%), 046 (12·3%) and 014/020 (9·9). The incidence rate was 2·6 cases of C. difficile infection for every 1000 outpatients.

Distribution and characterization of Clostridium difficile isolated from dogs in Japan

We collected 204 nondiarrhoeic canine fecal samples and isolated 68 Clostridium difficile strains from 62 of these samples. Strains were grouped into 29 PCR ribotypes. Only 47% of the strains were toxigenic.

Outcome of relapsing Clostridium difficile infections do not correlate with virulence-, spore- and vegetative cell-associated phenotypes

One of the main clinical challenges of Clostridium difficile infections (CDI) is the high rate of relapse episodes. The main determinants involved in relapse of CDI include the presence of antibiotic-resistant C. difficile spores in the colonic environment and a permanent state of dysbiosis of the microbiota caused by antibiotic therapy. A possible scenario is that phenotypes related to the persistence of C. difficile spores might contribute to relapsing infections. In this study, 8 C. difficile isolates recovered from 4 cases with relapsing infection, and 9 isolates recovered from single infection cases were analyzed for PCR ribotyping and the presence of tcdA, tcdB and cdtAB genes. Factors associated to spore persistence, sporulation, spore adherence and biofilm formation and sporulation during biofilm formation were characterized. We also evaluated motility and cytotoxicity. However, we observed no significant difference in the analyzed phenotypes among the different clinical outcomes, most likely due to the high variability observed among strains within clinical backgrounds in each phenotype and the small sample size. It is noteworthy that C. difficile spores adhered to similar extents to undifferentiated and differentiated Caco-2 cells. By contrast, spores of all clinical isolates tested had increased germination efficiency in presence of taurocholate, while decreased sporulation rate during biofilm development in the presence of glucose. In conclusion, these results show that, at least in this cohort of patients, the described phenotypes are not detrimental in the clinical outcome of the disease.

Recurrent Clostridium difficile infection: From colonization to cure

Clostridium difficile infection (CDI) is increasingly prevalent, dangerous and challenging to prevent and manage. Despite intense national and international attention the incidence of primary and of recurrent CDI (PCDI and RCDI, respectively) have risen rapidly throughout the past decade. Of major concern is the increase in cases of RCDI resulting in substantial morbidity, morality and economic burden. RCDI management remains challenging as there is no uniformly effective therapy, no firm consensus on optimal treatment, and reliable data regarding RCDI-specific treatment options is scant. Novel therapeutic strategies are critically needed to rapidly, accurately, and effectively identify and treat patients with, or at-risk for, RCDI. In this review we consider the factors implicated in the epidemiology, pathogenesis and clinical presentation of RCDI, evaluate current management options for RCDI and explore novel and emerging therapies.

Multiplex Real-Time PCR Method for Simultaneous Identification and Toxigenic Type Characterization of Clostridium difficile From Stool Samples

Background

The aim of this study was to develop and validate a multiplex real-time PCR assay for simultaneous identification and toxigenic type characterization of Clostridium difficile.

Methods

The multiplex real-time PCR assay targeted and simultaneously detected triose phosphate isomerase (tpi) and binary toxin (cdtA) genes, and toxin A (tcdA) and B (tcdB) genes in the first and sec tubes, respectively. The results of multiplex real-time PCR were compared to those of the BD GeneOhm Cdiff assay, targeting the tcdB gene alone. The toxigenic culture was used as the reference, where toxin genes were detected by multiplex real-time PCR.

Results

A total of 351 stool samples from consecutive patients were included in the study. Fifty-five stool samples (15.6%) were determined to be positive for the presence of C. difficile by using multiplex real-time PCR. Of these, 48 (87.2%) were toxigenic (46 tcdA and tcdB-positive, two positive for only tcdB) and 11 (22.9%) were cdtA-positive. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the multiplex real-time PCR compared with the toxigenic culture were 95.6%, 98.6%, 91.6%, and 99.3%, respectively. The analytical sensitivity of the multiplex real-time PCR assay was determined to be 103colonyforming unit (CFU)/g spiked stool sample and 0.0625 pg genomic DNA from culture. Analytical specificity determined by using 15 enteric and non-clostridial reference strains was 100%.

Conclusions

The multiplex real-time PCR assay accurately detected C. difficile isolates from diarrheal stool samples and characterized its toxin genes in a single PCR run.

Whole-genome sequencing improves discrimination of relapse from reinfection and identifies transmission events among patients with recurrent Clostridium difficile infections

BACKGROUND

Recurrent Clostridium difficile infection (CDI) represents a significant healthcare challenge. Patients may suffer multiple episodes of CDI with the index strain (relapse) or become infected by another strain acquired nosocomially (reinfection).

AIM

We aimed to characterize C. difficile isolates causing recurrent CDI at a tertiary referral hospital by whole-genome sequencing (WGS) to assess strain similarities at the highest level of genetic resolution and accurately detect relapse, reinfection, and putative strain transmission events.

METHODS

An 18-month prospective study of recurrent CDI was undertaken. Clostridium difficile was cultured from stool samples collected longitudinally from any patients suffering ≥2 clinically defined CDI episodes. Patient demographics and clinical data were recorded, and strain relatedness investigated by both polymerase chain reaction (PCR)-based ribotyping and WGS.

FINDINGS

Nineteen patients were identified with ≥2 clinically defined CDI episodes who cumulatively suffered 39 recurring CDI episodes (58 total episodes). Patients had a median length of stay (LOS) of 144 days and experienced between two and seven CDI episodes. Ribotyping indicated 27 apparent same-strain relapses, five reinfections and the predominance of ribotypes 078 (ST-11) and 020 (ST-2). WGS allowed characterization of relapse with increased certainty and identified emergent within-strain single nucleotide variants (SNVs) with potential functional impact on diverse genes. Shared ribotypes among 14 patients with recurrent CDI suggested 10 possible patient-to-patient transmission events. However, WGS revealed greater diversity at the sub-ribotype level, excluding all but four transmission events.

CONCLUSION

WGS exhibits several advantages over PCR-based ribotyping in terms of its ability to distinguish relapse from reinfection, to identify patient-to-patient transmission events, and to exact fine structure characterization of recurrent CDI epidemiology. This offers the potential for more focused infection prevention strategies to eliminate strain transmission among patients with recurrent CDI.

Rapid spread of Clostridium difficile NAP1/027/ST1 in Chile confirms the emergence of the epidemic strain in Latin America

Clostridium difficile infection has gained importance in recent years as a result of the rapid spread of epidemic strains, including hypervirulent strains. This study reports the molecular epidemiology of C. difficile obtained from hospitalized patients in Chile. Seven hundred and nineteen isolates of toxigenic C. difficile from 45 hospitals across the country were characterized through toxin profile, pulsed-field gel electrophoresis (PFGE), and sequencing of the tcdC gene. In addition, polymerase chain reaction (PCR) ribotyping and multilocus sequence typing (MLST) were performed on a subset of selected strains. PFGE typing of 719 isolates of C. difficile produced 60 PFGE patterns (subtypes). Subtype 1 was predominant (79% of isolates) and related to the hypervirulent strain (NAP1). Subtype 1 showed 73% relatedness with nine other subtypes, which had a similar tcdC deletion. Subtype 1 corresponded to ribotype 027 and ST1. This report shows the wide dissemination of the hypervirulent strain NAP1/027/ST1 in Chile.