Increasing prevalence of toxin A-negative, toxin B-positive isolates of Clostridium difficile in Korea: impact on laboratory diagnosis. J Clin Microbiol. 2008;46:1116-1117. [PMID: 18199783 DOI: 10.1128/jcm.01188-07]

Clostridioides difficile in food and food products of animal origin in Assam, India

OBJECTIVE

Considering the paucity of information about food-associated Clostridioides difficile from India, a study was undertaken to establish the prevalence of C. difficile in a variety of foods of animal origin, together with molecular strain characterization and antimicrobial resistance.

METHODS

A total of 235 samples comprising raw meat and meat products, fish products, and milk and milk products were screened for C. difficile. Toxin genes and other parts of PaLoc were amplified in isolated strains. The resistance pattern towards commonly used antimicrobial agents was studied by the Epsilometric test.

RESULTS

C. difficile was isolated from 17(7.23%) different food samples of animal origin, including toxigenic (6) and non-toxigenic (11) isolates. In four toxigenic strains, the tcdA gene could not be detected under used conditions (tcdA-tcdB+). However, all strains had binary toxin-associated genes (cdtA and cdtB). The antimicrobial resistance was highest in non-toxigenic C. difficile isolates in food of animal origin.

CONCLUSION

Meat, meat products and dry fish, but not milk and milk products were contaminated with C. difficile. Contamination rates were low with diverse toxin profiles and antibiotic resistance patterns among the C. difficile strains.

Clostridioides difficile: Current overview and future perspectives

The most common world-wide cause of antibiotic-associated infectious diarrhea and colitis is the toxin producing bacterium, Clostridioides difficile (C. difficile). Here we review the background and characteristics of the bacterium and the toxins produced together with the epidemiology and the complex pathogenesis that leads to a broad clinical spectrum of disease. The review describes the difficulties faced in obtaining a quick and accurate diagnosis despite the range of sensitive and specific diagnostic tools available. We also discuss the problem of disease recurrence and the importance of disease prevention. The high rates of infection recurrence mean that treatment strategies are constantly under review and we outline the diverse treatment options that are currently in use and explore the emerging treatment options of pulsed antibiotic use, microbial replacement therapies and the use of monoclonal antibodies. We summarize the future direction of treatment strategies which include the development of novel antibiotics, the administration of oral polyclonal antibody formulations, the use of vaccines, the administration of competitive non-toxigenic spores and the neutralization of antibiotics at the microbiota level. Future successful treatments will likely involve a combination of therapies to provide the most effective and robust approach to C. difficile management.

Genetic Relatedness of 5-Year Isolates of Clostridioides difficile Polymerase Chain Reaction Ribotype 017 Strains in a Hospital

The objective of this study was to analyse the genetic relatedness of Clostridioides difficile polymerase chain reaction ribotype 017 (RT017) strains from patients with hospital-acquired C. difficile infection (HA-CDI) in a hospital with a high RT017 prevalence. From 2009 to 2013, 200 RT017 strains (26.8%) were collected from 745 HA-CDI patient isolates. They comprised 64 MLVA types, and 197 (98.5%) strains were genetically related to 5 clonal complexes (CCs). The largest cluster, CC-A, included 163 isolates of 40 MLVA types. CC-A accounted for 20% of RT017 strains in 2009 and sharply increased to 94.9% in 2010, 94% in 2011, 86.2% in 2012, and 73.5% in 2013. The other 4 CCs included 20 isolates with 7 MLVA types. The resistance rates of antimicrobials were as follows: clindamycin 100%, moxifloxacin 99%, rifaximin 88.5%, and vancomycin 1%. All isolates were susceptible to metronidazole and piperacillin/tazobactam. Comparing antibiotic resistance among CCs, the geometric mean of the minimum inhibitory concentrations of moxifloxacin, vancomycin, and piperacillin/tazobactam were significantly higher for CC-A isolates than for the other CCs. RT017 clones constantly evolved over the 5 years studied with regard to genetic relatedness. The levels of antibiotic resistance may contribute to the persistence of organisms in the institution.

Defining the black box: a narrative review of factors associated with adverse outcomes from severe Clostridioides difficile infection

In the United States, Clostridioides difficile infection (CDI) is the leading cause of healthcare-associated infection, affecting nearly half a million people and resulting in more than 20,000 in-hospital deaths every year. It is therefore imperative to better characterize the intricate interplay between C. difficile microbial factors, host immunologic signatures, and clinical features that are associated with adverse outcomes of severe CDI. In this narrative review, we discuss the implications of C. difficile genetics and virulence factors in the molecular epidemiology of CDI, and the utility of early biomarkers in predicting the clinical trajectory of patients at risk of developing severe CDI. Furthermore, we identify associations between host immune factors and CDI outcomes in both animal models and human studies. Next, we highlight clinical factors including renal dysfunction, aging, blood biomarkers, level of care, and chronic illnesses that can affect severe CDI diagnosis and outcome. Finally, we present our perspectives on two specific treatments pertinent to patient outcomes: metronidazole administration and surgery. Together, this review explores the various venues of CDI research and highlights the importance of integrating microbial, host, and clinical data to help clinicians make optimal treatment decisions based on accurate prediction of disease progression.

Ultrasensitive and quantitative toxin measurement correlates with baseline severity, severe outcomes, and recurrence among hospitalized patients with Clostridioides difficile infection

BACKGROUND

Stool toxin concentrations may impact Clostridioides difficile infection (CDI) severity and outcomes. We correlated fecal C. difficile toxin concentrations, measured by an ultrasensitive and quantitative assay, with CDI baseline severity, attributable outcomes, and recurrence.

METHODS

We enrolled 615 hospitalized adults (≥ 18y) with CDI (acute diarrhea, positive stool NAAT, and decision to treat). Baseline stool toxin A and B concentrations were measured by Single Molecule Array. Subjects were classified by baseline CDI severity (four scoring methods) and outcomes within 40 days (death, ICU stay, colectomy, and recurrence).

RESULTS

Among 615 patients (median 68.0 years), in all scoring systems, subjects with severe baseline disease had higher stool toxin A+B concentrations than those without (P<0.01). Nineteen subjects (3.1%) had a severe outcome primarily-attributed to CDI (group 1). This group had higher median toxin A+B [14,303 pg/mL (IQR 416.0, 141,967)] than subjects in whom CDI only contributed to the outcome [group 2, 163.2 pg/mL(0.0, 8423.3)], subjects with severe outcome unrelated to CDI [group 3, 158.6 pg/mL (0.0, 1795.2)], or no severe outcome [group 4, 209.5 pg/mL (0.0, 8566.3)](P=0.003). Group 1 was more likely to have detectable toxin (94.7%) than groups 2-4 (60.5-66.1%)(P=0.02). Individuals with recurrence had higher toxin A+B [2266.8 pg/mL(188.8, 29411)] than those without [154.0 pg/mL(0.0, 5864.3)](P<0.001) and higher rates of detectable toxin (85.7% versus 64.0%, P=0.004).

CONCLUSIONS

In CDI patients, ultrasensitive stool toxin detection and concentration correlated with severe baseline disease, severe CDI-attributable outcomes, and recurrence, confirming the contribution of toxin quantity to disease presentation and clinical course.

A Rare Case of Arterial and Venous Thromboembolism in a Patient With Severe Clostridium difficile Infection

Most cases of Clostridium difficile infection are hospital acquired; but in recent times, the incidence of community-acquired infections has increased. Patients with Clostridium difficile infections are at an increased risk for thrombosis. We report a case of an 82-year-old female who was admitted to the intensive care unit for acute hypoxic respiratory failure and septic shock. She was found to have Clostridium difficile infection at presentation. During the hospitalization, we discovered bilateral lower extremity venous thromboembolism, bilateral pulmonary embolism, multifocal thromboembolic brain infarctions, and acute arterial thromboembolic occlusion of right upper and lower extremities. This patient adds to the list of cases of venous thromboembolism associated with Clostridium difficile infections and is the first case of associated arterial embolic phenomenon. There is a need to further investigate the association of Clostridium difficile infections and thromboembolism.

Functional analyses of epidemic Clostridioides difficile toxin B variants reveal their divergence in utilizing receptors and inducing pathology

Clostridioides difficile toxin B (TcdB) is a key virulence factor that causes C. difficile associated diseases (CDAD) including diarrhea and pseudomembranous colitis. TcdB can be divided into multiple subtypes/variants based on their sequence variations, of which four (TcdB1-4) are dominant types found in major epidemic isolates. Here, we find that these variants are highly diverse in their receptor preference: TcdB1 uses two known receptors CSPG4 and Frizzled (FZD) proteins, TcdB2 selectively uses CSPG4, TcdB3 prefers to use FZDs, whereas TcdB4 uses neither CSPG4 nor FZDs. By creating chimeric toxins and systematically switching residues between TcdB1 and TcdB3, we determine that regions in the N-terminal cysteine protease domain (CPD) are involved in CSPG4-recognition. We further evaluate the pathological effects induced by TcdB1-4 with a mouse intrarectal installation model. TcdB1 leads to the most severe overall symptoms, followed by TcdB2 and TcdB3. When comparing the TcdB2 and TcdB3, TcdB2 causes stronger oedema while TcdB3 induces severer inflammatory cell infiltration. These findings together demonstrate divergence in the receptor preference and further lead to colonic pathology for predominant TcdB subtypes.

Clostridioides difficile is a major cause of nosocomial and community-associated gastrointestinal infections. The bacterium produces three exotoxins including TcdA, TcdB, and CDT, of which TcdB is known as a key virulence factor causing the diseases. Since C. difficile was first linked to antibiotic-associated infections in 1978, a large number of clinically relevant strains were characterized and many of them were found to harbor some variant forms of TcdB. In this study, we examined four predominant TcdB variants from epidemic C. difficile strains. We found that these variants are highly diverse in preference to the known receptors, CSPG4 and Frizzled proteins. By conducting a systematically designed mutagenesis study, we determined that TcdB interacts with CSPG4 via regions across multiple domains. We also found that TcdB variants could induce distinguishable pathological phenotypes in a mouse model, suggesting C. difficile strains harboring divergent TcdB variants might exhibit different disease progression. Our study provides new insights into the toxicology and pathology of C. difficile toxin variants.

The Relative Role of Toxins A and B in the Virulence of Clotridioides difficile

Most pathogenic strains of C. difficile possess two large molecular weight single unit toxins with four similar functional domains. The toxins disrupt the actin cytoskeleton of intestinal epithelial cells leading to loss of tight junctions, which ultimately manifests as diarrhea in the host. While initial studies of purified toxins in animal models pointed to toxin A (TcdA) as the main virulence factor, animal studies using isogenic mutants demonstrated that toxin B (TcdB) alone was sufficient to cause disease. In addition, the natural occurrence of TcdA−/TcdB+ (TcdA−/B+)mutant strains was shown to be responsible for cases of C. difficile infection (CDI) with symptoms identical to CDI caused by fully toxigenic (A+/B+) strains. Identification of these cases was delayed during the period when clinical laboratories were using immunoassays that only detected TcdA (toxA EIA). Our hospital laboratory at the time performed culture as well as toxA EIA on patient stool samples. A total of 1.6% (23/1436) of all clinical isolates recovered over a 2.5-year period were TcdA−/B+ variants, the majority of which belonged to the restriction endonuclease analysis (REA) group CF and toxinotype VIII. Despite reports of serious disease due to TcdA−/B+ CF strains, these infections were typically mild, often not requiring specific treatment. While TcdB alone may be sufficient to cause disease, clinical evidence suggests that both toxins have a role in disease.

Recommendations for the diagnosis and treatment of Clostridioides difficile infection: An official clinical practice guideline of the Spanish Society of Chemotherapy (SEQ), Spanish Society of Internal Medicine (SEMI) and the working group of Postoperative Infection of the Spanish Society of Anesthesia and Reanimation (SEDAR)

This document gathers the opinion of a multidisciplinary forum of experts on different aspects of the diagnosis and treatment of Clostridioides difficile infection (CDI) in Spain. It has been structured around a series of questions that the attendees considered relevant and in which a consensus opinion was reached. The main messages were as follows: CDI should be suspected in patients older than 2 years of age in the presence of diarrhea, paralytic ileus and unexplained leukocytosis, even in the absence of classical risk factors. With a few exceptions, a single stool sample is sufficient for diagnosis, which can be sent to the laboratory with or without transportation media for enteropathogenic bacteria. In the absence of diarrhoea, rectal swabs may be valid. The microbiology laboratory should include C. difficile among the pathogens routinely searched in patients with diarrhoea. Laboratory tests in different order and sequence schemes include GDH detection, presence of toxins, molecular tests and toxigenic culture. Immediate determination of sensitivity to drugs such as vancomycin, metronidazole or fidaxomycin is not required. The evolution of toxin persistence is not a suitable test for follow up. Laboratory diagnosis of CDI should be rapid and results reported and interpreted to clinicians immediately. In addition to the basic support of all diarrheic episodes, CDI treatment requires the suppression of antiperistaltic agents, proton pump inhibitors and antibiotics, where possible. Oral vancomycin and fidaxomycin are the antibacterials of choice in treatment, intravenous metronidazole being restricted for patients in whom the presence of the above drugs in the intestinal lumen cannot be assured. Fecal material transplantation is the treatment of choice for patients with multiple recurrences but uncertainties persist regarding its standardization and safety. Bezlotoxumab is a monoclonal antibody to C. difficile toxin B that should be administered to patients at high risk of recurrence. Surgery is becoming less and less necessary and prevention with vaccines is under research. Probiotics have so far not been shown to be therapeutically or preventively effective. The therapeutic strategy should be based, rather than on the number of episodes, on the severity of the episodes and on their potential to recur. Some data point to the efficacy of oral vancomycin prophylaxis in patients who reccur CDI when systemic antibiotics are required again.

The characteristics of Clostridium difficile ST81, a new PCR ribotype of toxin A- B+ strain with high-level fluoroquinolones resistance and higher sporulation ability than ST37/PCR ribotype 017

Antibiotic exposure, Clostridium difficile toxins, and spore formation are key factors involved in the pathogenesis of Clostridium difficile infection (CDI). A high incidence of CDI due to toxin A- B+ strains, which were classified into two genotypes (ST81 and ST37) by multilocus sequence typing, was identified in Beijing Friendship Hospital in 2016-2017. ST81 was the most prevalent type, accounting for 81.25% of toxin A- B+ strains. ST81 corresponded to a novel PCR ribotype, PKI-017, with one less band than ST37/ribotype 017 in PCR ribotyping. All ST81 strains showed a high level of ciprofloxacin resistance (MICs ≥ 64 μg mL-1) and moxifloxacin resistance (MICs ≥ 128 μg mL-1) with the amino acid substitutions Thr82 to Ile in GyrA and Ser416 to Ala in GyrB. There was either no mutation or only the single amino acid mutation Thr82 to Ile in the GyrA subunit of ST37/ribotype 017 strains, which had lower MICs of ciprofloxacin (4-64 μg mL-1) and moxifloxacin (4-16 μg mL-1). In addition, ST81 strains exhibited higher spore formation ability than ST37/ribotype 017 strains. Overall, our results indicated that ST81 strains had unique characteristics distinguishable from ST37 strains and emphasized the importance of ongoing surveillance for this new genotype.

Clostridium difficile ribotype 017 - characterization, evolution and epidemiology of the dominant strain in Asia

Clostridium difficile ribotype (RT) 017 is an important toxigenic C. difficile RT which, due to a deletion in the repetitive region of the tcdA gene, only produces functional toxin B. Strains belonging to this RT were initially dismissed as nonpathogenic and circulated largely undetected for almost two decades until they rose to prominence following a series of outbreaks in the early 2000s. Despite lacking a functional toxin A, C. difficile RT 017 strains have been shown subsequently to be capable of causing disease as severe as that caused by strains producing both toxins A and B. While C. difficile RT 017 strains can be found in almost every continent today, epidemiological studies suggest that the RT is endemic in Asia and that the global spread of this MLST clade 4 lineage member is a relatively recent event. C. difficile RT 017 transmission appears to be mostly from human to human with only a handful of reports of isolations from animals. An important feature of C. difficile RT 017 strains is their resistance to several antimicrobials and this has been documented as a possible factor driving multiple outbreaks in different parts of the world. This review summarizes what is currently known regarding the emergence and evolution of strains belonging to C. difficile RT 017 as well as features that have allowed it to become an RT of global importance.

Clostridium difficile in patients attending tuberculosis hospitals in Cape Town, South Africa, 2014-2015

Background

Diarrhoea due to Clostridium difficile infection (CDI) poses a significant burden on healthcare systems around the world. However, there are few reports on the current status of the disease in sub-Saharan Africa.

Objectives

This study examined the occurrence of CDI in a South African population of tuberculosis patients, as well as the molecular epidemiology and antibiotic susceptibility profiles of C. difficile strains responsible for disease.

Methods

Toxigenic C. difficile in patients with suspected CDI attending two specialist tuberculosis hospitals in the Cape Town area were detected using a PCR-based diagnostic assay (Xpert^® C. difficile). C. difficile strains isolated from PCR-positive specimens were characterised by ribotyping, multilocus variable-number tandem-repeat analysis and antibiotic susceptibility testing.

Results

The period prevalence of CDI was approximately 70.07 cases per 1000 patient admissions. Strains belonging to ribotype 017 (RT017) made up over 95% of the patient isolates and all of them were multi-drug resistant. Multilocus variable-number tandem-repeat analysis revealed several clusters of highly related C. difficile RT017 strains present in tuberculosis patients in several wards at each hospital.

Conclusion

Tuberculosis patients represent a population that may be at an increased risk of developing CDI and, in addition, may constitute a multi-drug resistant reservoir of this bacterium. This warrants further investigation and surveillance of the disease in this patient group and other high-risk patient groups in sub-Saharan Africa.

Detection of toxigenic Clostridioides [Clostridium] difficile: Usefulness of two commercially available enzyme immunoassays and a PCR assay on stool samples and stool isolates

The best laboratory diagnostic approach to detect Clostridioides [Clostridium] difficile infection (CDI) is a subject of ongoing debate. With the aim of evaluating four laboratory diagnostic methods, 250 unformed stools from patients with suspected CDI submitted to nine medical center laboratories from November 2010 to December 2011, were studied using: (1) an immunochromatographic rapid assay test that combines the qualitative determination of glutamate dehydrogenase (GDH) plus toxins A and B (QAB), the CDIFF QUIK CHEK COMPLETE assay; (2) an enzyme immunoassay for qualitative determination of toxins A and B, the RIDASCREEN™ C. difficile Toxin A/B assay (RAB); (3) a PCR for the toxin B gene assay (PCR); and (4) the toxigenic culture (TC). C. difficile isolates from direct toxin negative stools by QAB, RAB and PCR were evaluated for toxigenicity by the same direct tests, in order to assess the contribution of the TC (QAB-TC, RAB-TC, PCR-TC). A combination of the cell culture cytotoxicity neutralization assay (CCCNA) in stools, and the same assay on isolates from direct negative samples (CCCNA-TC) was considered the reference method (CCCNA/CCCNA-TC). Of the 250 stools tested, 107 (42.8%) were positive by CCCNA/CCCNA-TC. The GDH and PCR/PCR-TC assays were the most sensitive, 91.59% and 87.62%, respectively. The QAB, RAB, QAB/QAB-TC and RAB/RAB-TC had the highest specificities, ca. 95%. A negative GDH result would rule out CDI, however, its low positive likelihood ratio (PLR) of 3.97 indicates that a positive result should always be complemented with the detection of toxins. If the RAB, QAB, and PCR assays do not detect toxins from direct feces, the toxigenic culture should be performed. In view of our results, the most accurate and reliable methods to be applied in a clinical microbiology laboratory were the QAB/QAB-TC, and RAB/RAB-TC, with PLRs >10 and negative likelihood ratios <0.30.

A human gut ecosystem protects against C. difficile disease by targeting TcdA

BACKGROUND

A defined Microbial Ecosystem Therapeutic (MET-1, or "RePOOPulate") derived from the feces of a healthy volunteer can cure recurrent C. difficile infection (rCDI) in humans. The mechanisms of action whereby healthy microbiota protect against rCDI remain unclear. Since C. difficile toxins are largely responsible for the disease pathology of CDI, we hypothesized that MET-1 exerts its protective effects by inhibiting the effects of these toxins on the host.

METHODS

A combination of in vivo (antibiotic-associated mouse model of C. difficile colitis, mouse ileal loop model) and in vitro models (FITC-phalloidin staining, F actin Western blots and apoptosis assay in Caco2 cells, transepithelial electrical resistance measurements in T84 cells) were employed.

RESULTS

MET-1 decreased both local and systemic inflammation in infection and decreased both the cytotoxicity and the amount of TcdA detected in stool, without an effect on C. difficile viability. MET-1 protected against TcdA-mediated damage in a murine ileal loop model. MET-1 protected the integrity of the cytoskeleton in cells treated with purified TcdA, as indicated by FITC-phalloidin staining, F:G actin assays and preservation of transepithelial electrical resistance. Finally, co-incubation of MET-1 with purified TcdA resulted in decreased detectable TcdA by Western blot analysis.

CONCLUSIONS

MET-1 intestinal microbiota confers protection against C. difficile and decreases C. difficile-mediated inflammation through its protective effects against C. difficile toxins, including enhancement of host barrier function and degradation of TcdA. The effect of MET-1 on C. difficile viability seems to offer little, if any, contribution to its protective effects on the host.

Current knowledge on the laboratory diagnosis of Clostridium difficile infection

Clostridium difficile (C. difficile) is a spore-forming, toxin-producing, gram-positive anaerobic bacterium that is the principal etiologic agent of antibiotic-associated diarrhea. Infection with C. difficile (CDI) is characterized by diarrhea in clinical syndromes that vary from self-limited to mild or severe. Since its initial recognition as the causative agent of pseudomembranous colitis, C. difficile has spread around the world. CDI is one of the most common healthcare-associated infections and a significant cause of morbidity and mortality among older adult hospitalized patients. Due to extensive antibiotic usage, the number of CDIs has increased. Diagnosis of CDI is often difficult and has a substantial impact on the management of patients with the disease, mainly with regards to antibiotic management. The diagnosis of CDI is primarily based on the clinical signs and symptoms and is only confirmed by laboratory testing. Despite the high burden of CDI and the increasing interest in the disease, episodes of CDI are often misdiagnosed. The reasons for misdiagnosis are the lack of clinical suspicion or the use of inappropriate tests. The proper diagnosis of CDI reduces transmission, prevents inadequate or unnecessary treatments, and assures best antibiotic treatment. We review the options for the laboratory diagnosis of CDI within the settings of the most accepted guidelines for CDI diagnosis, treatment, and prevention of CDI.

Comparative Genome Analysis and Global Phylogeny of the Toxin Variant Clostridium difficile PCR Ribotype 017 Reveals the Evolution of Two Independent Sublineages

The diarrheal pathogen Clostridium difficile consists of at least six distinct evolutionary lineages. The RT017 lineage is anomalous, as strains only express toxin B, compared to strains from other lineages that produce toxins A and B and, occasionally, binary toxin. Historically, RT017 initially was reported in Asia but now has been reported worldwide. We used whole-genome sequencing and phylogenetic analysis to investigate the patterns of global spread and population structure of 277 RT017 isolates from animal and human origins from six continents, isolated between 1990 and 2013. We reveal two distinct evenly split sublineages (SL1 and SL2) of C. difficile RT017 that contain multiple independent clonal expansions. All 24 animal isolates were contained within SL1 along with human isolates, suggesting potential transmission between animals and humans. Genetic analyses revealed an overrepresentation of antibiotic resistance genes. Phylogeographic analyses show a North American origin for RT017, as has been found for the recently emerged epidemic RT027 lineage. Despite having only one toxin, RT017 strains have evolved in parallel from at least two independent sources and can readily transmit between continents.

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).

Molecular Epidemiology and Antimicrobial Susceptibility of Clostridium difficile Isolates from a University Teaching Hospital in China

While the developed world has seen a significant increase in the number of scientific articles on Clostridium difficile infection (CDI), the developing world still lags behind on this subject due to limited laboratory capacity, low awareness, and limited surveillance of this problem. As such, CDI is considered a neglected but potentially huge problem in developing countries. The major aim of this study was to systemically evaluate the utility of several molecular typing tools for CDI, including their relevance in epidemiological studies in developing countries such as China. A total of 116 non-repetitive toxigenic C. difficile isolates from Chinese patients, were studied. The isolates comprised 83 (71.6%) A+B+CDT- isolates, 27 (23.3%) A-B+CDT- isolates, and 6 (5.1%) A+B+CDT+ isolates. Typing methods evaluated included multilocus variable-number tandem-repeat analysis, PCR ribotyping, multilocus sequence typing, and sequencing of slpA and tcdC genes, which identified 113, 30, 22, 18, and 8 genotypes each and exhibited discriminatory powers of 0.999, 0.916, 0.907, 0.883, and 0.765, respectively. Compared to A+B+ strains, A-B+ strains exhibited higher prevalence of drug resistance to clindamycin, erythromycin, levofloxacin, rifampicin, rifaximin, and tetracycline. Furthermore, drug resistance rates of strains with different PCR ribotypes differed, supporting the importance of molecular typing in management and control of CDI. Based on our earlier suggestion to improve the diagnostic laboratory capacity of CDI in developing countries, setting up efficient surveillance programs complemented by relevant molecular typing methods is warranted.

Homogeneous and digital proximity ligation assays for the detection of Clostridium difficile toxins A and B

Background

The proximity ligation assay (PLA) detects proteins via their interaction with pairs of proximity probes, which are antibodies coupled to noncomplementary DNA oligonucleotides. The binding of both proximity probes to their epitopes on the target protein brings the oligonucleotides together, allowing them to be bridged by a third oligonucleotide with complementarity to the other two. This enables their ligation and the detection of the resulting amplicon by real-time quantitative PCR (qPCR), which acts as a surrogate marker for the protein of interest. Hence PLA has potential as a clinically relevant diagnostic tool for the detection of pathogens where nucleic acid based tests are inconclusive proof of infection.

Methods

We prepared monoclonal and polyclonal proximity probes targeting Clostridium difficile toxins A (TcdA) and B (TcdB) and used hydrolysis probe-based qPCR and digital PCR (dPCR) assays to detect antibody/antigen interactions.

Results

The performance of the PLA assays was antibody-dependent but both TcdA and TcdB assays were more sensitive than comparable ELISAs in either single- or dualplex formats. Both PLAs could be performed using single monoclonal antibodies coupled to different oligonucleotides. Finally, we used dPCR to demonstrate its potential for accurate and reliable quantification of TcdA.

Conclusions

PLA with either qPCR or dPCR readout have potential as new diagnostic applications for the detection of pathogens where nucleic acid based tests do not indicate viability or expression of toxins. Importantly, since it is not always necessary to use two different antibodies, the pool of potential antibodies useful for PLA diagnostic assays is usefully enhanced.

Monitoring in real time the cytotoxic effect of Clostridium difficile upon the intestinal epithelial cell line HT29

The incidence and severity of Clostridium difficile infections (CDI) has been increased not only among hospitalized patients, but also in healthy individuals traditionally considered as low risk population. Current treatment of CDI involves the use of antibiotics to eliminate the pathogen, although recurrent relapses have also been reported. For this reason, the search of new antimicrobials is a very active area of research. The strategy to use inhibitors of toxin's activity has however been less explored in spite of being a promising option. In this regard, the lack of fast and reliable in vitro screening methods to search for novel anti-toxin drugs has hampered this approach. The aim of the current study was to develop a method to monitor in real time the cytotoxicity of C. difficile upon the human colonocyte-like HT29 line, since epithelial intestinal cells are the primary targets of the toxins. The label-free, impedance based RCTA (real time cell analyser) technology was used to follow overtime the behaviour of HT29 in response to C. difficile LMG21717 producing both A and B toxins. Results obtained showed that the selection of the medium to grow the pathogen had a great influence in obtaining toxigenic supernatants, given that some culture media avoided the release of the toxins. A cytotoxic dose- and time-dependent effect of the supernatant obtained from GAM medium upon HT29 and Caco2 cells was detected. The sigmoid-curve fit of data obtained with HT29 allowed the calculation of different toxicological parameters, such as EC50 and LOAEL values. Finally, the modification in the behaviour of HT29 reordered in the RTCA was correlated with the cell rounding effect, typically induced by these toxins, visualized by time-lapsed captures using an optical microscope. Therefore, this RTCA method developed to test cytotoxicity kinetics of C. difficile supernatants upon IEC could be a valuable in vitro model for the screening of new anti-CDI agents.

Preparation and preliminary application of monoclonal antibodies to the receptor binding region of Clostridium difficile toxin B

A previous nationwide Chinese epidemiological study revealed through isolation of A‑B+ Clostridium difficile strains, which produce toxin B (TcdB), but not toxin A TcdA, that the strains are widespread and more frequent in east Asian countries,. The development of a process capable of detecting TcdB is required in microbiological laboratories in order to facilitate the control of the A‑B+ C. difficile strains, however, no diagnostic reagents have been developed to date. The aim of the present study was to prepare monoclonal antibodies (mAbs) targeting the receptor binding region of TcdB (CDB3), and to establish a double‑antibody sandwich enzyme-linked immunosorbent assay (ds‑ELISA), which can be used for the diagnosis of C. difficile infection. The recombinant protein, glutathione S transferase (GST)‑CDB3 was expressed and purified using an Escherichia coli system. BALB/c mice were immunized with GST‑CDB3 recombinant protein. A hybridoma technique was used for the production of anti‑CDB3 mAb. The hybridoma clones were then screened using indirect ELISA, and anti‑CDB3 mAb was produced in the ascites of the BALB/c mice. Isotyping of anti‑CDB3 mAb was performed using an SBA Clonotyping system/horseradish peroxidase (HRP) ELISA kit. Protein G affinity chromatography was used for purification of anti‑CDB3 mAbs, and the titer and specificity of the anti‑CDB3 mAbs were assessed using indirect ELISA and western blot analysis, respectively. The ds‑ELISA was established using HRP‑labeled anti‑CDB3 mAbd, which were used to detect TcdB clinically in diarrhea stools. A total of five stable hybridoma cell clones (1E7B, 1F8D3, 2F8A6, 3B6F1 and 4A4G2) producing anti‑CDB3 mAb were established. The results of the present study indicated that the immunoglobulin (Ig)G isotype was predominant, as 1E7B2 IgG1 (λ), 2F8A6 IgG2a (κ) and 4A4G2 IgG1 (κ). In addition, the highest titer of anti‑CDB3 mAb (2F8A6 and 4A4G2) was 1:51,200. Western blotting revealed that the 2F8A6 and 4A4G2 mAbs recognized the CDB3 protein specifically. Following anti‑CDB3 mAb (4A4G2) HRP‑labeling, the optimal working concentration was confirmed to be 1:400, and the concentration of coated antibody (2F8A6) was 20 µg/ml. The sensitivity of the ds‑ELISA was 73.33% for the A+B+ toxigenic C. difficile strains, and 86.67% for the A‑B+ toxigenic C. difficile strains, with a specificity of 100% for all. In conclusion, the present study successfully developed novel mAbs specific to CDB3, and developed a ds-ELISA kit with high specificity and sensitivity for the rapid detection of TcdB. This offers a useful tool for the diagnostic assessment of TcdB.

Genomic Epidemiology of a Protracted Hospital Outbreak Caused by a Toxin A-Negative Clostridium difficile Sublineage PCR Ribotype 017 Strain in London, England

Clostridium difficile remains the leading cause of nosocomial diarrhea worldwide, which is largely considered to be due to the production of two potent toxins: TcdA and TcdB. However, PCR ribotype (RT) 017, one of five clonal lineages of human virulent C. difficile, lacks TcdA expression but causes widespread disease. Whole-genome sequencing was applied to 35 isolates from hospitalized patients with C. difficile infection (CDI) and two environmental ward isolates in London, England. The phylogenetic analysis of single nucleotide polymorphisms (SNPs) revealed a clonal cluster of temporally variable isolates from a single hospital ward at University Hospital Lewisham (UHL) that were distinct from other London hospital isolates. De novo assembled genomes revealed a 49-kbp putative conjugative transposon exclusive to this hospital clonal cluster which would not be revealed by current typing methodologies. This study identified three sublineages of C. difficile RT017 that are circulating in London. Similar to the notorious RT027 lineage, which has caused global outbreaks of CDI since 2001, the lineage of toxin-defective RT017 strains appears to be continually evolving. By utilization of WGS technologies to identify SNPs and the evolution of clonal strains, the transmission of outbreaks caused by near-identical isolates can be retraced and identified.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Bacterial Gastroenteritis

Bacterial gastroenteritis is a disease that is pervasive in both the developing and developed worlds. While for the most part bacterial gastroenteritis is self-limiting, identification of an etiological agent by bacterial stool culture is required for the management of patients with severe or prolonged diarrhea, symptoms consistent with invasive disease, or a history that may predict a complicated course of disease. Importantly, characterization of bacterial enteropathogens from stool cultures in clinical laboratories is one of the primary means by which public health officials identify and track outbreaks of bacterial gastroenteritis. This article provides guidance for clinical microbiology laboratories that perform stool cultures. The general characteristics, epidemiology, and clinical manifestations of key bacterial enteropathogens are summarized. Information regarding optimal specimen collection, transport, and processing and current diagnostic tests and testing algorithms is provided. This article is an update of Cumitech 12A (P. H. Gilligan, J. M. Janda, M. A. Karmali, and J. M. Miller, Cumitech 12A, Laboratory diagnosis of bacterial diarrhea, 1992).

The epidemiology and economic burden of Clostridium difficile infection in Korea

The prevalence of Clostridium difficile infection and the associated burden have recently increased in many countries. While the main risk factors for C. difficile infection include old age and antibiotic use, the prevalence of this infection is increasing in low-risk groups. These trends highlight the need for research on C. difficile infection. This study pointed out the prevalence and economic burden of C. difficile infection and uses the representative national data which is primarily from the database of the Korean Health Insurance Review and Assessment Service, for 2008–2011. The annual economic cost was measured using a prevalence approach, which sums the costs incurred to treat C. difficile infection. C. difficile infection prevalence was estimated to have increased from 1.43 per 100,000 in 2008 to 5.06 per 100,000 in 2011. Moreover, mortality increased from 69 cases in 2008 to 172 in 2011. The economic cost increased concurrently, from $2.4 million in 2008 to $7.6 million, $10.5 million, and $15.8 million in 2009, 2010, and 2011, respectively. The increasing economic burden of C. difficile infection over the course of the study period emphasizes the need for intervention to minimize the burden of a preventable illness like C. difficile infection.

Investigation of toxin gene diversity and antimicrobial resistance of Clostridium difficile strains

The incidence of Clostridium difficile infection (CDI) has been previously reported in a number of studies. However, data collected from the Chinese population is limited. In the present study, the diversity of the toxin genes, tcdA and tcdB, of 57 Clostridium difficile (C. difficile) isolates from a Chinese population were investigated by polymerase chain reaction (PCR) (38 A⁺B⁺, 14 A^-B⁺ and 5 A^-B^-). Quantitative PCR was used to check the expression of these two genes and it was found that the genes were not expressed by all the strains. The absence of tcdA or tcdB expression in certain strains could be due to the lower expression of tcdD and the higher expression of tcdC, which are positive and negative regulators for these two toxin genes, respectively. In addition, the antimicrobial susceptibilities of 57 isolates were investigated. Therefore, these data would aid in the future prevention of CDI outbreaks and improve the understanding of the infection.

Variations in virulence and molecular biology among emerging strains of Clostridium difficile

Clostridium difficile is a Gram-positive, spore-forming organism which infects and colonizes the large intestine, produces potent toxins, triggers inflammation, and causes significant systemic complications. Treating C. difficile infection (CDI) has always been difficult, because the disease is both caused and resolved by antibiotic treatment. For three and a half decades, C. difficile has presented a treatment challenge to clinicians, and the situation took a turn for the worse about 10 years ago. An increase in epidemic outbreaks related to CDI was first noticed around 2003, and these outbreaks correlated with a sudden increase in the mortality rate of this illness. Further studies discovered that these changes in CDI epidemiology were associated with the rapid emergence of hypervirulent strains of C. difficile, now collectively referred to as NAP1/BI/027 strains. The discovery of new epidemic strains of C. difficile has provided a unique opportunity for retrospective and prospective studies that have sought to understand how these strains have essentially replaced more historical strains as a major cause of CDI. Moreover, detailed studies on the pathogenesis of NAP1/BI/027 strains are leading to new hypotheses on how this emerging strain causes severe disease and is more commonly associated with epidemics. In this review, we provide an overview of CDI, discuss critical mechanisms of C. difficile virulence, and explain how differences in virulence-associated factors between historical and newly emerging strains might explain the hypervirulence exhibited by this pathogen during the past decade.

Comparison of polymerase chain reaction ribotyping, toxinotyping and nutritional aspects of toxin production of Clostridium difficile strains

Clostridium difficile (C. difficile) is the leading cause of infectious diarrhea in hospitals worldwide. Enterotoxin A (TcdA) and cytotoxin B (TcdB), have been identified as the main virulence factors of C. difficile. In China, data on polymerase chain reaction (PCR) ribotypes and abilities of hospital-derived C. difficile isolates to produce TcdA and TcdB are sparse. In this study, we identified 40 C. difficile isolates from the Taizhou hospital and investigated their PCR ribotypes based on the 16S-23S rRNA gene intergenic spacer region. The ability of different ribotypes to produce TcdA and TcdB was determined by immunochromatography and cytotoxicity assays, respectively. The effects of the nutritional status on the production of these toxins were also investigated.

Diagnosis of Clostridium difficile infection: an ongoing conundrum for clinicians and for clinical laboratories

Clostridium difficile is a formidable nosocomial and community-acquired pathogen, causing clinical presentations ranging from asymptomatic colonization to self-limiting diarrhea to toxic megacolon and fulminant colitis. Since the early 2000s, the incidence of C. difficile disease has increased dramatically, and this is thought to be due to the emergence of new strain types. For many years, the mainstay of C. difficile disease diagnosis was enzyme immunoassays for detection of the C. difficile toxin(s), although it is now generally accepted that these assays lack sensitivity. A number of molecular assays are commercially available for the detection of C. difficile. This review covers the history and biology of C. difficile and provides an in-depth discussion of the laboratory methods used for the diagnosis of C. difficile infection (CDI). In addition, strain typing methods for C. difficile and the evolving epidemiology of colonization and infection with this organism are discussed. Finally, considerations for diagnosing C. difficile disease in special patient populations, such as children, oncology patients, transplant patients, and patients with inflammatory bowel disease, are described. As detection of C. difficile in clinical specimens does not always equate with disease, the diagnosis of C. difficile infection continues to be a challenge for both laboratories and clinicians.

Clostridium difficile infection: a worldwide disease

Clostridium difficile, an anaerobic toxigenic bacterium, causes a severe infectious colitis that leads to significant morbidity and mortality worldwide. Both enhanced bacterial toxins and diminished host immune response contribute to symptomatic disease. C. difficile has been a well-established pathogen in North America and Europe for decades, but is just emerging in Asia. This article reviews the epidemiology, microbiology, pathophysiology, and clinical management of C. difficile. Prompt recognition of C. difficile is necessary to implement appropriate infection control practices.

Molecular epidemiology of Clostridium difficile at a medical center in Taiwan: persistence of genetically clustering of A⁻B⁺ isolates and increase of A⁺B⁺ isolates

Introduction

We investigated the changing trend of various toxigenic Clostridium difficile isolates at a 3 500-bed hospital in Taiwan. Genetic relatedness and antimicrobial susceptibility of toxigenic C. difficile isolates were also examined.

Methods

A total of 110 non-repeat toxigenic C. difficile isolates from different patients were collected between 2002 and 2007. Characterization of the 110 toxigenic isolates was performed using agar dilution method, multilocus variable-number tandem-repeat analysis (MLVA) genotyping, tcdC genotyping, and toxinotyping.

Results

Among the 110 toxigenic isolates studied, 70 isolates harbored tcdA and tcdB (A⁺B⁺) and 40 isolates harbored tcdB only (A⁻B⁺). The annual number of A⁺B⁺ isolates considerably increased over the 6-year study (P = 0.055). A total of 109 different MLVA genotypes were identified, in which A⁺B⁺ isolates and A⁻B⁺ isolates were differentiated into two genetic clusters with similarity of 17.6%. Twenty-four (60%) of the 40 A⁻B⁺ isolates formed a major cluster, MLVA-group 1, with a similarity of 85%. Seven (6.4%) resistant isolates were identified, including two metronidazole-resistant and five vancomycin-resistant isolates.

Conclusions

This study indicated a persistence of a MLVA group 1 A⁻B⁺ isolates and an increase of A⁺B⁺ isolates with diverse MLVA types. Moreover, C. difficile isolates with antimicrobial resistance to metronidazole or vancomycin were found to have emerged. Continuous surveillance is warranted to understand the recent situation and control the further spread of the toxigenic C. difficile isolates, especially among hospitalized patients.

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.

Susceptibility of hamsters to Clostridium difficile isolates of differing toxinotype

Clostridium difficile is the most commonly associated cause of antibiotic associated disease (AAD), which caused ∼21,000 cases of AAD in 2011 in the U.K. alone. The golden Syrian hamster model of CDI is an acute model displaying many of the clinical features of C. difficile disease. Using this model we characterised three clinical strains of C. difficile, all differing in toxinotype; CD1342 (PaLoc negative), M68 (toxinotype VIII) & BI-7 (toxinotype III). The naturally occurring non-toxic strain colonised all hamsters within 1-day post challenge (d.p.c.) with high-levels of spores being shed in the faeces of animals that appeared well throughout the entire experiment. However, some changes including increased neutrophil influx and unclotted red blood cells were observed at early time points despite the fact that the known C. difficile toxins (TcdA, TcdB and CDT) are absent from the genome. In contrast, hamsters challenged with strain M68 resulted in a 45% mortality rate, with those that survived challenge remaining highly colonised. It is currently unclear why some hamsters survive infection, as bacterial & toxin levels and histology scores were similar to those culled at a similar time-point. Hamsters challenged with strain BI-7 resulted in a rapid fatal infection in 100% of the hamsters approximately 26 hr post challenge. Severe caecal pathology, including transmural neutrophil infiltrates and extensive submucosal damage correlated with high levels of toxin measured in gut filtrates ex vivo. These data describes the infection kinetics and disease outcomes of 3 clinical C. difficile isolates differing in toxin carriage and provides additional insights to the role of each toxin in disease progression.

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.

The continually evolving Clostridium difficile species

Clostridium difficile is a spore-forming Gram-positive bacterium that causes chronic diarrhea and sometimes life-threatening disease mainly in elderly and hospitalized patients. The reported incidence of C. difficile infection has changed dramatically over the last decade and has been related to the emergence of distinct clonal lineages that appear more transmissible and cause more severe infection. These include PCR ribotypes 027, 017 and more recently 078. Population biology studies using multilocus sequence typing and whole-genome comparisons has helped to define the C. difficile species into four clonal complexes that include PCR ribotypes 027, 017, 078 and 023, as well as a general grouping of most other PCR ribotypes. Further analysis of strains from diverse sources and geographical origins reveal significant microdiversity of clonal complexes and confirms that C. difficile is continuing to evolve. The study of C. difficile represents a real-time global evolutionary experiment where the pathogen is responding to a range of selective pressures created by human activity and practices in healthcare settings. The advent of whole-genome sequencing coupled with phylogeny (phylogeography and phylohistory) will provide unprecedented detail on the local and global emergence and disappearance of C. difficile clones, and facilitate more rational approaches to disease control. This review will highlight the emergence of virulent C. difficile clones and our current understanding of molecular epidemiology of the species.

Epidemiology of Clostridium difficile infections in a tertiary-care hospital in Korea

To survey healthcare-associated Clostridium difficile infection (HA-CDI) in a 900-bed tertiary-care hospital, we prospectively investigated the epidemiology of CDI and distribution of PCR-ribotypes. From February 2009 through January 2010, all patients with HA-CDI were enrolled. Epidemiological information and prescription records for antibiotics were collected. The C. difficile isolates were characterized using reference strains and were tested for antibiotic susceptibility. During the survey, incidence of HA-CDI was 71.6 per 100 000 patient-days. In total, 140 C. difficile isolates were obtained from 166 patients with HA-CDI. The PCR-ribotyping yielded 38 distinct ribotypes. The three most frequently found ribotypes made up 56.4% of all isolates; they comprised 37 isolates (26.4%) of PCR-ribotype 018, 22 (15.7%) of toxin A-negative PCR-ribotype 017, and 20 (14.3%) of PCR-ribotype 001. Clostridium difficile PCR-ribotype 018 was present in all departments throughout the hospital during the 11 months, whereas ribotype 017 and ribotype 001 appeared mostly in the pulmonary department. Hypervirulent C. difficile PCR-ribotype 027 was detected in 1 month on two wards. The incidence of CDI in each department showed a seven-fold difference, which correlated significantly with the amount of prescribed clindamycin (R = 0.783, p 0.013) or moxifloxacin (R = 0.733, p 0.025) in the departments. The rates of resistance of the three commonest ribotypes to clindamycin and moxifloxacin were significantly higher than those of other strains (92.1% versus 38.2% and 89.5% versus 27.3%, respectively). CDI is an important nosocomially acquired infection and this study emphasizes the importance of implementing country-wide surveillance to detect and control CDI in Korea.

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.

Epidemiology and control of Clostridium difficile infections in healthcare settings: an update

PURPOSE OF REVIEW

The epidemiology of Clostridium difficile infections (CDIs) has dramatically changed over the last decade in both North America and Europe. The objectives of this review are to highlight the recent epidemiological data and to provide an overview of the current knowledge of infection control measures.

RECENT FINDINGS

Since 2003, many countries have reported increased incidence of CDI and outbreaks of severe cases of CDI. This trend is assumed to be due, in part, to the emergence and rapid spread of a 'hypervirulent' strain, known as 027/BI/NAP1. This strain has become endemic in many hospitals in North America and Europe. CDI rates have also increased in the community and new genotypes (e.g. PCR ribotype 078) are emerging in both humans and animals. To prevent cross-contamination and to reduce the incidence of CDI, infection control guidelines, based primarily on experience of hospitals during outbreaks, have been recently updated in Europe and the United States. CDI prevention relies on a bundle of measures including antimicrobial stewardship, prompt diagnosis, and the implementation of contact precautions. Currently, most of these measures have appeared effective in controlling outbreaks, but the best methods to reduce CDI incidence in settings of endemicity are still unknown.

SUMMARY

The recent changes in CDI epidemiology have pushed infection control healthcare workers and scientific societies to revisit and update their guidelines for infection control.

Epidemiology and clinical characteristics of Clostridium difficile infection in a Korean tertiary hospital

In order to investigate the incidence, clinical and microbiologic characteristics of Clostridium difficile infection (CDI) in Korea, a prospective observational study was performed. From September 2008 through January 2010, all patients whose stool was tested for toxin assay A&B and/or C. difficile culture were studied for clinical characteristics. Toxin types of the isolates from stool were tested. The mean incidence of CDI per 100,000 patient-days was 71.6 by month (range, 52.5-114.0), and the ratio of CDI to antibiotic-associated diarrhea was 0.23. Among 200 CDI patients, 37.5% (75/200) was severe CDI based on severity score. Clinical outcome of 189 CDI was as followed; 25.9% (49/189) improved without treatment, 84.3% (118/140) achieved clinical cure and attributed mortality was 0.7% (1/140) with the treatment. Recurrence rate was 21.4% (30/140) and cure without recurrence was 66.4% (93/140). The most common type of toxin was toxin A-positive/toxin B-positive strain (77.5%), toxin A-negative/toxin B-positive strains or binary toxin-producing strains comprised 15.4% or 7.1%, respectively. In conclusion, the incidence of CDI in Korea is a little higher than other reports during the non-epidemic setting. We expect that the change of epidemiology and clinical severity in CDI can be evaluated based on these results.

Detection of Clostridium difficile toxin A/B genes by multiplex real-time PCR for the diagnosis of C. difficile infection

Toxigenic Clostridium difficile culture is considered to be the standard diagnostic method for the detection of C. difficile infection (CDI). Culture methods are time-consuming and although enzyme immunoassay is rapid and easy to use, it has low sensitivity. In the present study, the AdvanSure CD real-time (RT)-PCR kit (LG Life Sciences) was evaluated for its ability to detect C. difficile toxin A (tcdA) and B (tcdB) genes, simultaneously. A total of 127 fresh diarrhoeal stool specimens, submitted to the clinical microbiology laboratory for C. difficile culture, were tested. C. difficile toxins and toxin genes were detected with a VIDAS C. difficile A&B (VIDAS-CDAB) enzyme-linked fluorescent immunoassay (ELFA) and the AdvanSure RT-PCR kit, respectively, according to the manufacturers' instructions. Their performance was compared with a standard toxigenic culture method as a reference. The sensitivity, specificity and positive and negative predictive values using the AdvanSure RT-PCR kit were 100 %, 98.3 %, 84.6 % and 100 %, respectively, while those of the VIDAS-CDAB system were 63.6 %, 100 %, 100 % and 96.6 %, respectively. Four tcdA(+)/tcdB(+) strains of C. difficile were detected with the AdvanSure RT-PCR kit, which offers comparable sensitivity and specificity to the reference method with a turnaround time of ~3 hours.

Sporulation studies in Clostridium difficile

Clostridium difficile is a leading cause of healthcare-associated diarrhoea. In recent years, certain C. difficile types have become highly represented among clinical isolates and are associated with outbreaks of increased disease severity, higher relapse rates and an expanded repertoire of antibiotic resistance. Endospores, produced during sporulation, play a pivotal role in infection and disease transmission and it has been suggested in the literature that these so-called 'hypervirulent' C. difficile types are more prolific in terms of sporulation in vitro. However, work in our laboratory has provided evidence to the contrary suggesting that although there is significant strain-to-strain variation in C. difficile sporulation characteristics this variation does not appear to be type-associated. On analysis of the literature, it is apparent that the methods used to quantify sporulation in previous studies have varied greatly and sample sizes have remained small. The conflicting data in the literature may, therefore, not necessarily be generally representative of C. difficile sporulation. Instead, these inconsistencies may reflect differences in the experimental design of each study. In this review, the need for further investigations of C. difficile sporulation rates is highlighted. Specifically, the advantages and disadvantages of the different experimental approaches previously used are discussed and a standard set of principles for measuring C. difficile sporulation in the future is proposed.

The analysis of para-cresol production and tolerance in Clostridium difficile 027 and 012 strains

BACKGROUND

Clostridium difficile is the major cause of antibiotic associated diarrhoea and in recent years its increased prevalence has been linked to the emergence of hypervirulent clones such as the PCR-ribotype 027. Characteristically, C. difficile infection (CDI) occurs after treatment with broad-spectrum antibiotics, which disrupt the normal gut microflora and allow C. difficile to flourish. One of the relatively unique features of C. difficile is its ability to ferment tyrosine to para-cresol via the intermediate para-hydroxyphenylacetate (p-HPA). P-cresol is a phenolic compound with bacteriostatic properties which C. difficile can tolerate and may provide the organism with a competitive advantage over other gut microflora, enabling it to proliferate and cause CDI. It has been proposed that the hpdBCA operon, rarely found in other gut microflora, encodes the enzymes responsible for the conversion of p-HPA to p-cresol.

RESULTS

We show that the PCR-ribotype 027 strain R20291 quantitatively produced more p-cresol in-vitro and was significantly more tolerant to p-cresol than the sequenced strain 630 (PCR-ribotype 012). Tyrosine conversion to p-HPA was only observed under certain conditions. We constructed gene inactivation mutants in the hpdBCA operon in strains R20291 and 630Δerm which curtails their ability to produce p-cresol, confirming the role of these genes in p-cresol production. The mutants were equally able to tolerate p-cresol compared to the respective parent strains, suggesting that tolerance to p-cresol is not linked to its production.

CONCLUSIONS

C. difficile converts tyrosine to p-cresol, utilising the hpdBCA operon in C. difficile strains 630 and R20291. The hypervirulent strain R20291 exhibits increased production of and tolerance to p-cresol, which may be a contributory factor to the virulence of this strain and other hypervirulent PCR-ribotype 027 strains.

Investigation of toxin gene diversity, molecular epidemiology, and antimicrobial resistance of Clostridium difficile isolated from 12 hospitals in South Korea

BACKGROUND

Clostridium difficile is a major cause of antibiotic-associated diarrhea. The objective of this study was to characterize clinical isolates of C. difficile obtained from various regions in Korea with regard to their toxin status, molecular type, and antimicrobial susceptibility.

METHODS

We analyzed a total of 408 C. difficile isolates obtained between 2006 and 2008 from 408 patients with diarrhea in 12 South Korean teaching hospitals. C. difficile toxin genes tcdA, tcdB, cdtA, and cdtB were detected by PCR. Molecular genotyping was performed by PCR ribotyping. Antimicrobial susceptibilities of the 120 C. difficile isolates were assessed by agar dilution methods.

RESULTS

Among 337 toxigenic isolates, 105 were toxin A-negative and toxin B-positive (A(-)B(+)) and 29 were binary toxin-producing strains. PCR ribotyping showed 50 different ribotype patterns. The 5 most frequently occurring ribotypes comprised 62.0% of all identified ribotypes. No isolate was susceptible to cefoxitin, and all except 1 were susceptible to piperacillin and piperacillin-tazobactam. The resistance rates of isolates to imipenem, cefotetan, moxifloxacin, ampicillin, and clindamycin were 25%, 34%, 42%, 51%, and 60%, respectively. The isolates showed no resistance to metronidazole or vancomycin.

CONCLUSIONS

This is the first nationwide study on the toxin status, including PCR ribotyping and antimicrobial resistance, of C. difficile isolates in Korea. The prevalence of A-B+ strains was 25.7%, much higher than that reported from other countries. Binary toxin-producing strains accounted for 7.1% of all strains, which was not rare in Korea. The most prevalent ribotype was ribotype 017, and all A-B+ strains showed this pattern. We did not isolate strains with decreased susceptibility to metronidazole or vancomycin.

The changing epidemiology of Clostridium difficile infections

The epidemiology of Clostridium difficile infection (CDI) has changed dramatically during this millennium. Infection rates have increased markedly in most countries with detailed surveillance data. There have been clear changes in the clinical presentation, response to treatment, and outcome of CDI. These changes have been driven to a major degree by the emergence and epidemic spread of a novel strain, known as PCR ribotype 027 (sometimes referred to as BI/NAP1/027). We review the evidence for the changing epidemiology, clinical virulence and outcome of treatment of CDI, and the similarities and differences between data from various countries and continents. Community-acquired CDI has also emerged, although the evidence for this as a distinct new entity is less clear. There are new data on the etiology of and potential risk factors for CDI; controversial issues include specific antimicrobial agents, gastric acid suppressants, potential animal and food sources of C. difficile, and the effect of the use of alcohol-based hand hygiene agents.

The changing epidemiology of Clostridium difficile infections

The epidemiology of Clostridium difficile infection (CDI) has changed dramatically during this millennium. Infection rates have increased markedly in most countries with detailed surveillance data. There have been clear changes in the clinical presentation, response to treatment, and outcome of CDI. These changes have been driven to a major degree by the emergence and epidemic spread of a novel strain, known as PCR ribotype 027 (sometimes referred to as BI/NAP1/027). We review the evidence for the changing epidemiology, clinical virulence and outcome of treatment of CDI, and the similarities and differences between data from various countries and continents. Community-acquired CDI has also emerged, although the evidence for this as a distinct new entity is less clear. There are new data on the etiology of and potential risk factors for CDI; controversial issues include specific antimicrobial agents, gastric acid suppressants, potential animal and food sources of C. difficile, and the effect of the use of alcohol-based hand hygiene agents.

Evolutionary dynamics of Clostridium difficile over short and long time scales

Clostridium difficile has rapidly emerged as the leading cause of antibiotic-associated diarrheal disease, with the transcontinental spread of various PCR ribotypes, including 001, 017, 027 and 078. However, the genetic basis for the emergence of C. difficile as a human pathogen is unclear. Whole genome sequencing was used to analyze genetic variation and virulence of a diverse collection of thirty C. difficile isolates, to determine both macro and microevolution of the species. Horizontal gene transfer and large-scale recombination of core genes has shaped the C. difficile genome over both short and long time scales. Phylogenetic analysis demonstrates C. difficile is a genetically diverse species, which has evolved within the last 1.1-85 million years. By contrast, the disease-causing isolates have arisen from multiple lineages, suggesting that virulence evolved independently in the highly epidemic lineages.

Molecular characterization of toxin A-negative, toxin B-positive variant strains of Clostridium difficile isolated in Korea

A(-)B(+)Clostridium difficile strains are prevalent in Korea. We performed pulsed-field gel electrophoresis (PFGE), polymerase chain reaction ribotyping, and toxinotyping in 82 A(-)B(+) clinical isolates in Korea. PFGE showed highest discriminatory capability among the 3 methods. By PFGE, persistence of a clone was found, suggesting this clone has adapted to the hospital environment.

Typing of Clostridium difficile isolates endemic in Japan by sequencing of slpA and its application to direct typing

A typing system for Clostridium difficile using sequencing of the surface-layer protein A encoding gene (slpA) was evaluated and used to analyse clinical isolates in Japan. A total of 160 stool specimens from symptomatic patients in Japan was examined and 87 C. difficile isolates were recovered. slpA sequence typing was found to have reliable typability and discriminatory power in comparison with PCR ribotyping, and the typing results were highly reproducible and comparable. slpA sequence typing was used to type C. difficile in DNA extracted directly from stool specimens. Among the 90 stool specimens in which direct typing results were obtained, 77 specimens were positive for C. difficile culture, and typing results from isolated strains agreed with those from direct typing in all 77 specimens. The slpA sequence type smz was dominant at all four hospitals examined, and this endemic type was detected by culture and/or direct typing in 61 (62 %) of 99 stool specimens positive for toxic culture and/or direct slpA sequence typing. Comparison of epidemic strains reported throughout the world revealed one isolate identified as slpA sequence type gc8, which was found to correspond to PCR ribotype 027 (BI/NAP1/027), whereas no isolates were found with the slpA gene identical to that of PCR ribotype 078 strain. slpA sequence typing is valuable for comparison of C. difficile strains epidemic in diverse areas because the typing results are reproducible and can easily be shared. In addition, slpA sequence typing could be applied to direct typing without culture.