Consequences of Clostridium difficile infection: understanding the healthcare burden

Sensitive assays enable detection of serum IgG antibodies against Clostridium difficile toxin A and toxin B in healthy subjects and patients with Clostridium difficile infection

BACKGROUND

Pathogenic Clostridium difficile produces two proinflammatory exotoxins, toxin A and toxin B. Low level of serum antitoxin IgG antibodies is a risk factor for the development of primary and recurrent C. difficile infection (CDI).

RESULTS

We developed and validated two sensitive, titer-based electrochemiluminescence assays for the detection of serum antibody levels against C. difficile toxins A and B. These assays demonstrated excellent precision. The sensitivity of the assays allowed the detection of antitoxin A and antitoxin B IgG antibodies in all tested serum samples during assay validation.

CONCLUSION

The validated titer-based assays enable assessment of antitoxin A and antitoxin B IgG antibodies as potential biomarkers to identify patients with CDI at increased risk for CDI recurrence.

Fecal microbiota transplantation for Clostridium difficile infection: back to the future

INTRODUCTION

Clostridium difficile infection (CDI) is a leading cause of diarrhea in the industrialized world. The estimated costs of this infection are impressive: over 3.2 billion dollars annually in the US. The introduction of fecal microbiota transplantation (FMT) to clinical practice can be considered a Copernican Revolution. The rationale of this approach consists of correcting the imbalance of the organisms dwelling in the gut by reintroducing a normal flora.

AREAS COVERED

This review focuses on the indication for FMT in CDI; it examines in-depth the most relevant aspects of the techniques used, and the safety and efficacy of this new 'old' therapy.

EXPERT OPINION

Authoritative guidelines about the management of CDI strongly recommend FMT for multiple recurrent episodes of infection by C. difficile unresponsive to repeated antibiotic treatment. The cure rates are about 90%, with no serious adverse events having been reported. The main concerns are the long-term outcomes, lack of a standardized procedure for the delivery of donor material, and a cultural barrier to the transplantation of fecal microbiota. A promising solution to some of these problems could be the use of a more acceptable administration route of fecal material, namely, oral capsules.

Spectrum of Clostridium difficile infections: Particular clinical situations

Incidence, pathogenesis, diagnostic techniques and therapeutic management of CDI have prompted abundant and adequate recent literature. However, report on clinical manifestations of CDI is frequently biased by the type of patients selected, the retrospective nature of many papers, the epidemic or endemic characteristics of the population reported. This article seeks to review some less discussed clinical and epidemiological aspects of CDI trying to include the clinical manifestations of this disease in unselected populations and also including discussion of CDI in specific groups of patients such as patients without colon and rectum, pediatric and critical care patients.

Rapid detection of ermB gene in Clostridium difficile by loop-mediated isothermal amplification

Macrolide-lincosamide-streptogramin B resistance in Clostridium difficile is mostly due to the ermB resistance determinant. Here, we describe a sensitive and rapid molecular method to detect ermB in C. difficile to contribute to the wider epidemiological study. Five sets of loop-mediated isothermal amplification (LAMP) primers were designed and optimized for rapid detection of ermB. The specificity and sensitivity of the primers for ermB were detected, and the ermB LAMP assay was compared to conventional PCR with 80 clinical isolates of C. difficile. Real-time monitoring of turbidity and chromogenic reaction were used to determine negative and positive results. A total of 26 pathogenic bacterial strains of different species were found to be negative for ermB, which indicated the high specificity of the primers. ermB was detected in 78.8 % (63/80) of the clinical isolates by both LAMP and conventional PCR. The detection limit of LAMP was 36.1  pg DNA μl- 1 and its sensitivity was 10-fold greater than that of conventional PCR. This study is the first report regarding the development and application of the LAMP assay for detection of the ermB gene in C. difficile strains. The developed LAMP method is sensitive, specific and provides a user-friendly visual approach for the rapid detection of ermB-bearing C. difficile.

Clostridium difficile recurrent infection: possible implication of TA systems

Clostridium difficile is an important nosocomial pathogen associated with antibiotic treatments. C. difficile's ability to survive antimicrobial therapy and transition from inert colonization to active infection is one of the most perplexing aspects of C. difficile infections and suggests that additional mechanisms are involved in persistence. In this regard, novel mechanisms linked with pathogenesis and persistence of C. difficile such as toxin–antitoxin systems might significantly contribute to biofilm formation and persistent infection. This review will focus on advances of toxin–antitoxin systems in C. difficile and their putative roles will be discussed.

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.

Routine disc diffusion antimicrobial susceptibility testing of Clostridium difficile and association with PCR ribotype 027

Reduced susceptibility to metronidazole and vancomycin in Clostridium difficile has been reported, which emphasises the need for simple antimicrobial susceptibility testing methods. The aim of this study was to apply a published disc diffusion method and zone diameter breakpoint correlates to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological minimum inhibitory concentration (MIC) cut-off values in a routine setting. Metronidazole and vancomycin zone diameters from 2702 isolates were recorded. Fifteen isolates had a metronidazole zone diameter below the published breakpoint (<23 mm) and five isolates had a vancomycin zone diameter below the published breakpoint (<19 mm), most of which were polymerase chain reaction (PCR) ribotype 027. The total number of PCR ribotype 027 was 29 (1.1 %). Overall, C. difficile PCR ribotype 027 isolates had smaller zone diameters than non-027 isolates. The disc diffusion method is very simple and inexpensive, and the published zone diameter breakpoints will detect C. difficile isolates with reduced susceptibility to metronidazole and vancomycin.

Efficient national surveillance for health-care-associated infections

Background

Detecting novel healthcare-associated infections (HCAI) as early as possible is an important public health priority. However, there is currently no evidence base to guide the design of efficient and reliable surveillance systems. Here we address this issue in the context of a novel pathogen spreading primarily between hospitals through the movement of patients.

Methods

Using a mathematical modelling approach we compare the current surveillance system for a HCAI that spreads primarily between hospitals due to patient movements as it is implemented in Scotland with a gold standard to determine if the current system is maximally efficient or whether it would be beneficial to alter the number and choice of hospitals in which to concentrate surveillance effort.

Results

We validated our model by demonstrating that it accurately predicts the risk of meticillin-resistant Staphylococcus aureus bacteraemia cases in Scotland.

Using the 29 (out of 182) sentinel hospitals that currently contribute most of the national surveillance effort results in an average detection time of 117 days. A reduction in detection time to 87 days is possible by optimal selection of 29 hospitals. Alternatively, the same detection time (117 days) can be achieved using just 22 optimally selected hospitals. Increasing the number of sentinel hospitals to 38 (teaching and general hospitals) reduces detection time by 43 days; however decreasing the number to seven sentinel hospitals (teaching hospitals) increases detection time substantially to 268 days.

Conclusions

Our results show that the current surveillance system as it is used in Scotland is not optimal in detecting novel pathogens when compared to a gold standard. However, efficiency gains are possible by better choice of sentinel hospitals, or by increasing the number of hospitals involved in surveillance. Similar studies could be used elsewhere to inform the design and implementation of efficient national, hospital-based surveillance systems that achieve rapid detection of novel HCAIs for minimal effort.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2172-9) contains supplementary material, which is available to authorized users.

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

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

Understanding the current state of infection prevention to prevent Clostridium difficile infection: a human factors and systems engineering approach

BACKGROUND

Achieving and sustaining high levels of health care worker (HCW) compliance with contact isolation precautions is challenging. The aim of this study was to determine HCW work system barriers to and facilitators of adherence to contact isolation for patients with suspected or confirmed Clostridium difficile infection (CDI) using a human factors and systems engineering approach.

METHODS

This prospective cohort study took place between September 2013 and November 2013 at a large academic medical center (hospital A) and an affiliated Veterans Administration hospital (hospital B). A human factors engineering (HFE) model for patient safety, the Systems Engineering Initiative for Patient Safety model, was used to guide work system analysis and direct observation data collection. There were 288 observations conducted. HCWs and visitors were assessed for compliance with all components of contact isolation precautions (hand hygiene, gowning, and gloving) before and after patient contact. Time required to complete contact isolation precautions was measured, and adequacy of contact isolation supplies was assessed.

RESULTS

Full compliance with contact isolation precautions was low at both hospitals A (7%) and B (22%). Lack of appropriate hand hygiene prior to room entry (compliance for hospital A: 18%; compliance for hospital B: 29%) was the most common reason for lack of full compliance. More time was required for full compliance compared with compliance with no components of contact isolation precautions before patient room entry, inside patient room, and after patient room exit (59.9 vs 3.2 seconds, P < .001; 507.3 vs 149.7 seconds, P = .006; 15.2 vs 1.3 seconds, P < .001, respectively). Compliance was lower when contact isolation supplies were inadequate (4% vs 16%, P = .005).

CONCLUSIONS

Adherence to contact isolation precautions for CDI is a complex, time-consuming process. HFE analysis indicates that multiple work system components serve as barriers and facilitators to full compliance with contact isolation precautions and should be addressed further to prevent CDI.

Cwp84, a Clostridium difficile cysteine protease, exhibits conformational flexibility in the absence of its propeptide

In recent decades, the global healthcare problems caused by Clostridium difficile have increased at an alarming rate. A greater understanding of this antibiotic-resistant bacterium, particularly with respect to how it interacts with the host, is required for the development of novel strategies for fighting C. difficile infections. The surface layer (S-layer) of C. difficile is likely to be of significant importance to host-pathogen interactions. The mature S-layer is formed by a proteinaceous array consisting of multiple copies of a high-molecular-weight and a low-molecular-weight S-layer protein. These components result from the cleavage of SlpA by Cwp84, a cysteine protease. The structure of a truncated Cwp84 active-site mutant has recently been reported and the key features have been identified, providing the first structural insights into the role of Cwp84 in the formation of the S-layer. Here, two structures of Cwp84 after propeptide cleavage are presented and the three conformational changes that are observed are discussed. These changes result in a reconfiguration of the active site and exposure of the hydrophobic pocket.

Is Clostridium difficile infection an increasingly common severe disease in adult intensive care units? A 10-year experience

PURPOSE

Despite the high concentration of patients with known risk factors for Clostridium difficile infection (CDI) in intensive care units (ICUs), data on ICU patients are scarce. The aim of this study was describe the incidence, clinical characteristics, and evolution of CDI in critically ill patients.

MATERIALS AND METHODS

From 2003 to 2012, adult patients admitted to an ICU (A-ICU) and positive for CDI were included and classified as follows: pre-ICU, if the positive sample was obtained within ±3 days of ICU admission; in-ICU, if obtained after 3 days of ICU admission and up to 3 days after ICU discharge.

RESULTS

We recorded 4095 CDI episodes, of which 328 were A-ICU (8%). Episodes of A-ICU decreased from 19.4 to 8.7 per 10000 ICU days of stay (P < .0001). Most A-ICU CDIs (66.3%) were mild to moderate. Pre-ICU episodes accounted for 16.2% and were more severe complicated than in-ICU episodes (11% vs 0%; P = .020). Overall mortality was 28.6%, and CDI-attributable mortality was only 3%.

CONCLUSION

The incidence of A-ICU CDI has decreased steadily over the last 10 years. A significant proportion of A-ICU CDI episodes are pre-ICU and are more severe than in-ICU CDI episodes. Most episodes of A-ICU CDI were nonsevere, with low associated mortality.

Effect of airborne hydrogen peroxide on spores of Clostridium difficile

BACKGROUND

Contamination of surfaces by spores of Clostridium difficile is a major factor influencing the spread of healthcare-associated C. difficile infection. The aim of this study was to test the effect of an automated room disinfection system that provides an aerosol of 7.5 % hydrogen peroxide (H2O2) disinfectant, on spores of two different strains of C. difficile, and to evaluate the impact of biological soiling on the efficacy of H2O2 disinfection.

MATERIAL AND METHOD

The strains used were a C. difficile PCR ribotype 027 and a C. difficile ATCC 9689. Spore suspensions of each strain were applied to ceramic tiles and exposed to aerosolized H2O2 at different locations in a test room. Biological soiling was simulated by bovine serum albumin and sheep erythrocytes. At set time points spores were recovered, plated onto Columbia 5 % sheep blood agar, and surviving bacteria were counted as colony-forming units (cfu).

RESULTS

No viable spores of either strain were recovered after a 3 h exposure to gaseous H2O2. Spores located inside a drawer showed recovery of approximately 1E5 cfu/ml for C. difficile ribotype 027 after 1 h. In the presence of organic matter, a more than fivefold log reduction compared with not exposed controls could be observed for spores of either strain tested.

CONCLUSION

Appropriate decontamination of surfaces exposed to spores of C. difficile is challenging for conventional cleaning methods. Aerosolized H2O2 delivered by automated room disinfection systems could possibly improve surface decontamination and thereby reduce transmission of healthcare-associated C. difficile infection. Also in the presence of organic matter H2O2 disinfection appears to be an effective adjunct for decontamination of environmental surfaces.

Flooding and emergency room visits for gastrointestinal illness in Massachusetts: a case-crossover study

Introduction

Floods and other severe weather events are anticipated to increase as a result of global climate change. Floods can lead to outbreaks of gastroenteritis and other infectious diseases due to disruption of sewage and water infrastructure and impacts on sanitation and hygiene. Floods have also been indirectly associated with outbreaks through population displacement and crowding.

Methods

We conducted a case-crossover study to investigate the association between flooding and emergency room visits for gastrointestinal illness (ER-GI) in Massachusetts for the years 2003 through 2007. We obtained ER-GI visits from the State of Massachusetts and records of floods from the National Oceanic and Atmospheric Association’s Storm Events Database. ER-GI visits were considered exposed if a flood occurred in the town of residence within three hazard periods of the visit: 0–4 days; 5–9 days; and 10–14 days. A time-stratified bi-directional design was used for control selection, matching on day of the week with two weeks lead or lag time from the ER-GI visit. Fixed effect logistic regression models were used to estimate the risk of ER-GI visits following the flood.

Results and Conclusions

A total of 270,457 ER-GI visits and 129 floods occurred in Massachusetts over the study period. Across all counties, flooding was associated with an increased risk for ER-GI in the 0–4 day period after flooding (Odds Ratio: 1.08; 95% Confidence Interval: 1.03–1.12); but not the 5–9 days (Odds Ratio: 0.995; 95% Confidence Interval: 0.955–1.04) or the 10–14 days after (Odds Ratio: 0.966, 95% Confidence Interval: 0.927–1.01). Similar results were observed for different definitions of ER-GI. The effect differed across counties, suggesting local differences in the risk and impact of flooding. Statewide, across the study period, an estimated 7% of ER-GI visits in the 0–4 days after a flood event were attributable to flooding.

Effects of Clostridium difficile infection in patients with alcoholic hepatitis

BACKGROUND & AIMS

Infection increases mortality in patients with alcoholic hepatitis (AH). Little is known about the association between Clostridium difficile infection (CDI) and AH. We examined the prevalence and effects of CDI in patients with AH, compared with those of other infections.

METHODS

We performed a cross-sectional analysis using data collected from the Nationwide Inpatient Sample, from 2008 through 2011. International Classification of Diseases, 9th revision, Clinical Modification codes were used to identify patients with AH. We used multivariable logistic regression to determine risk factors that affect mortality, negative binomial regression to evaluate the effects of CDI on predicted length of stay (LOS), and Poisson regression to determine the effects of CDI on predicted hospital charges. Chi-square and Wilcoxon rank-sum analyses were used to compare mortality, LOS, and hospital charges associated with CDI with those associated with urinary tract infection (UTI) and spontaneous bacterial peritonitis (SBP).

RESULTS

Of 10,939 patients with AH, 177 had CDI (1.62%). Patients with AH and CDI had increased odds of inpatient mortality (adjusted odds ratio, 1.75; P = .04), a longer predicted LOS (10.63 vs 5.75 d; P < .001), and greater predicted hospital charges ($36,924.30 vs $29,136.58; P < .001), compared with those without CDI. Compared with UTI, CDI was associated with similar mortality but greater LOS (9 vs 6 d; P < .001) and hospital charges ($45,607 vs $32,087; P < .001). SBP was associated with higher mortality than CDI (17.3% vs 10.1%; P = .045), but similar LOS and hospital charges.

CONCLUSIONS

In patients with AH, CDI is associated with greater mortality and health care use. These effects appear similar to those for UTI and SBP. We propose further studies to determine the cost effectiveness of screening for CDI among patients with AH.

Effect of treatment variation on outcomes in patients with Clostridium difficile

PURPOSE

New guidelines for the treatment of Clostridium difficile-associated diarrhea were published by the Infectious Disease Society of America (IDSA) in 2010, however, there has been no literature evaluating the effectiveness of these guidelines. The purpose of this study was to examine the clinical outcomes of Clostridium difficile infection including death, C difficile infection recurrence, toxic megacolon, and surgery between patients who received guideline-concordant therapy vs guideline-discordant therapy.

METHODS

Retrospective case-control study of hospitalized adults with C difficile infection presenting to a 420-bed tertiary care referral county teaching hospital. Patients were identified by International Classification of Diseases-9th Revision codes, and included if they were ≥18 years of age and treated for C difficile infection during their hospital visit. Complication rates (death, infection recurrence, toxic megacolon, and surgery) of patients with C difficile infection were measured to determine if following the IDSA guidelines improves outcomes.

RESULTS

Only 51.7% of the patients' prescribers followed the 2010 IDSA guidelines. Patients whose prescribers followed the IDSA guidelines experienced fewer complications than patients whose prescribers strayed from the guidelines (17.2% vs 56.3%, P <.0001). This difference was mainly due to a reduction in mortality (5.4% vs 21.8%, P = .0012) and infection recurrence (14% vs 35.6%, P = .0007). Patients who presented with severe and complicated disease received guideline-based therapy significantly less often than patients with mild disease (19.7%, 35.3%, and 81.2%, respectively, P <.0001).

CONCLUSIONS

There was a significant reduction in C difficile infection recurrence and mortality when prescribers followed the IDSA/Society for Healthcare Epidemiology of America guidelines for treatment of C difficile infection.

Evaluation of an automated rapid diagnostic test for detection of Clostridium difficile

The Verigene Clostridium difficile Nucleic Acid Test (Verigene CDF Test) (Nanosphere, Northbrook, IL, USA) is a new multiplex qualitative polymerase chain reaction (PCR) test used to detect C. difficile toxin genes in fecal specimens. To evaluate the performance of the new method, we tested 69 fecal samples from patients with suspected C. difficile infection using the Verigene CDF test, an enzyme immunoassay (EIA) and PCR following anaerobic fecal culture. The sensitivity, specificity, and accuracy of the Verigene CDF test were 96.7% (29/30), 97.4% (38/39), and 97.1% (67/69) respectively, using PCR following fecal culture as a reference method. We also analyzed the potential clinical impact of the Verigene CDF test using chart reviews of the 69 patients with suspected C. difficile infection and found that 11 of the 69 patients were incorrectly diagnosed, and the Verigene CDF test would have led to them receiving more appropriate management including practice of treatment and contact precaution, although, of the 69 patients, there are two whose samples were incorrectly identified with the Verigene CDF test. The Verigene CDF test will have a positive impact on patient care.

Abundant and diverse clustered regularly interspaced short palindromic repeat spacers in Clostridium difficile strains and prophages target multiple phage types within this pathogen

Clostridium difficile is an important human-pathogenic bacterium causing antibiotic-associated nosocomial infections worldwide. Mobile genetic elements and bacteriophages have helped shape C. difficile genome evolution. In many bacteria, phage infection may be controlled by a form of bacterial immunity called the clustered regularly interspaced short palindromic repeats/CRISPR-associated (CRISPR/Cas) system. This uses acquired short nucleotide sequences (spacers) to target homologous sequences (protospacers) in phage genomes. C. difficile carries multiple CRISPR arrays, and in this paper we examine the relationships between the host- and phage-carried elements of the system. We detected multiple matches between spacers and regions in 31 C. difficile phage and prophage genomes. A subset of the spacers was located in prophage-carried CRISPR arrays. The CRISPR spacer profiles generated suggest that related phages would have similar host ranges. Furthermore, we show that C. difficile strains of the same ribotype could either have similar or divergent CRISPR contents. Both synonymous and nonsynonymous mutations in the protospacer sequences were identified, as well as differences in the protospacer adjacent motif (PAM), which could explain how phages escape this system. This paper illustrates how the distribution and diversity of CRISPR spacers in C. difficile, and its prophages, could modulate phage predation for this pathogen and impact upon its evolution and pathogenicity.

IMPORTANCE

Clostridium difficile is a significant bacterial human pathogen which undergoes continual genome evolution, resulting in the emergence of new virulent strains. Phages are major facilitators of genome evolution in other bacterial species, and we use sequence analysis-based approaches in order to examine whether the CRISPR/Cas system could control these interactions across divergent C. difficile strains. The presence of spacer sequences in prophages that are homologous to phage genomes raises an extra level of complexity in this predator-prey microbial system. Our results demonstrate that the impact of phage infection in this system is widespread and that the CRISPR/Cas system is likely to be an important aspect of the evolutionary dynamics in C. difficile.

Sepsis outside intensive care unit: the other side of the coin

INTRODUCTION

A growing body of evidence points out that a large amount of patients with sepsis are admitted and treated in medical ward (MW). With most of the sepsis studies conducted in intensive care unit (ICU), these patients, older and with more comorbidities have received poor attention. Provided the differences between the two groups of patients, results of diagnostic and therapeutic trials from ICU should not be routinely transferred to MW, where sepsis seems to be at least as common as in ICU.

METHODS

We analyzed clinical trials on novel tools for an early diagnosis of sepsis published in the last two year adopting strict research criteria. Moreover we conducted a target review of the literature on non-invasive monitoring of severe sepsis and septic shock.

RESULTS AND CONCLUSIONS

The combination of innovative and non-invasive tools for sepsis rule in/out, as quick alternatives to blood cultures (gold standard) with bedside integrated ultrasonography could impact triage, diagnosis and prognosis of septic patients managed in MW, preventing ICU admissions, poor outcomes and costly complications, especially in elderly that are usually highly vulnerable to invasive procedures.

The structure of the cysteine protease and lectin-like domains of Cwp84, a surface layer-associated protein from Clostridium difficile

Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4 Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33-497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism.

Surotomycin demonstrates low in vitro frequency of resistance and rapid bactericidal activity in Clostridium difficile, Enterococcus faecalis, and Enterococcus faecium

Surotomycin (CB-183,315) is an orally administered, minimally absorbed, selective bactericidal cyclic lipopeptide in phase 3 development for the treatment of Clostridium difficile-associated diarrhea. The aim of this study was to evaluate the emergence of resistance in C. difficile (ATCC 700057 and three recent clinical isolates from the restriction endonuclease analysis groups BI, BK, and K), vancomycin-susceptible (VS) Enterococcus faecalis (ATCC 49452), vancomycin-resistant (VR) E. faecalis (ATCC 700802), VS Enterococcus faecium (ATCC 6569), and VR E. faecium (ATCC 51559) under anaerobic conditions. The rate of spontaneous resistance was below the limit of detection (<10(-8) to <10(-9)) for surotomycin at 16 and 32× the MIC for all isolates tested. Under selective pressure by serial passage, C. difficile grew in a maximum of 4 μg/ml surotomycin (final MICs of 2 to 8 μg/ml [4- to 16-fold higher than those of the naive control]) at day 15, with the exception of the C. difficile BK strain, which grew in 16 to 32 μg/ml (final MICs of 8 to 32 μg/ml [16- to 64-fold higher than those of the naive control]). Enterococci remained relatively unchanged over 15 days, growing in a maximum of 8 μg/ml surotomycin (final MICs of 2 to 16 μg/ml [8- to 64-fold higher than those of the naive control]). Of the isolates tested, no cross-resistance to vancomycin, rifampin, ampicillin, metronidazole, or moxifloxacin was observed. Surotomycin at 20× MIC demonstrated equally rapid bactericidal activity (≥ 3-log-unit reduction in CFU/ml in ≤ 8 h) against naive and reduced-susceptibility isolates of C. difficile, VS Enterococcus (VSE), and VR Enterococcus (VRE), except for C. difficile BK (2.6-log-unit reductions for both). These results suggest that emergence of resistance to surotomycin against C. difficile, E. faecalis, and E. faecium is likely to be rare.

Initiation of sporulation in Clostridium difficile: a twist on the classic model

The formation of dormant endospores is a complex morphological process that permits long-term survival in inhospitable environments for many Gram-positive bacteria. Sporulation for the anaerobic gastrointestinal pathogen Clostridium difficile is necessary for survival outside of the gastrointestinal tract of its host. While the developmental stages of spore formation are largely conserved among endospore-forming bacteria, the genus Clostridium appears to be missing a number of conserved regulators required for efficient sporulation in other spore-forming bacteria. Several recent studies have discovered novel mechanisms and distinct regulatory pathways that control the initiation of sporulation and early-sporulation-specific gene expression. These differences in regulating the decision to undergo sporulation reflects the unique ecological niche and environmental conditions that C. difficile inhabits and encounters within the mammalian host.

Comparison of the Verigene Clostridium difficile, Simplexa C. difficile Universal Direct, BD MAX Cdiff, and Xpert C. difficile assays for the detection of toxigenic C. difficile

We compared the Verigene Clostridium difficile test (Nanosphere, Northbrook, IL, USA), the Simplexa C. difficile Universal Direct (Focus Diagnostics, Cypress, CA, USA), the BD MAX Cdiff (Becton Dickinson, Franklin Lakes, NJ, USA), and the Xpert C. difficile (Cepheid, Sunnyvale, CA, USA) assays for the detection of toxigenic C. difficile. One hundred and ninety deidentified, remnant diarrheal specimens were included in this study. After resolution of discordant results by toxigenic culture, the Xpert C. difficile assay displayed the highest sensitivity (100%), with a specificity of 98.8%. The sensitivity and specificity were 95.2% and 99.4% and 87% and 100% for the Verigene CDF and Simplexa Universal Direct assays, respectively. Finally, the BD MAX assay showed a sensitivity of 87% and a specificity of 98.8%. Despite differences in the overall performance of these assays, these results support the routine use of these platforms for the detection of toxigenic C. difficile in the clinical laboratory.

Clostridium difficile phages: still difficult?

Phages that infect Clostridium difficile were first isolated for typing purposes in the 1980s, but their use was short lived. However, the rise of C. difficile epidemics over the last decade has triggered a resurgence of interest in using phages to combat this pathogen. Phage therapy is an attractive treatment option for C. difficile infection, however, developing suitable phages is challenging. In this review we summarize the difficulties faced by researchers in this field, and we discuss the solutions and strategies used for the development of C. difficile phages for use as novel therapeutics. Epidemiological data has highlighted the diversity and distribution of C. difficile, and shown that novel strains continue to emerge in clinical settings. In parallel with epidemiological studies, advances in molecular biology have bolstered our understanding of C. difficile biology, and our knowledge of phage–host interactions in other bacterial species. These three fields of biology have therefore paved the way for future work on C. difficile phages to progress and develop. Benefits of using C. difficile phages as therapeutic agents include the fact that they have highly specific interactions with their bacterial hosts. Studies also show that they can reduce bacterial numbers in both in vitro and in vivo systems. Genetic analysis has revealed the genomic diversity among these phages and provided an insight into their taxonomy and evolution. No strictly virulent C. difficile phages have been reported and this contributes to the difficulties with their therapeutic exploitation. Although treatment approaches using the phage-encoded endolysin protein have been explored, the benefits of using “whole-phages” are such that they remain a major research focus. Whilst we don’t envisage working with C. difficile phages will be problem-free, sufficient study should inform future strategies to facilitate their development to combat this problematic pathogen.

Cost-effectiveness of competing strategies for management of recurrent Clostridium difficile infection: a decision analysis

BACKGROUND

Clostridium difficile infection (CDI) is an important cause of morbidity and healthcare costs, and is characterized by high rates of disease recurrence. The cost-effectiveness of newer treatments for recurrent CDI has not been examined, yet would be important to inform clinical practice. The aim of this study was to analyze the cost effectiveness of competing strategies for recurrent CDI.

METHODS

We constructed a decision-analytic model comparing 4 treatment strategies for first-line treatment of recurrent CDI in a population with a median age of 65 years: metronidazole, vancomycin, fidaxomicin, and fecal microbiota transplant (FMT). We modeled up to 2 additional recurrences following the initial recurrence. We assumed FMT delivery via colonoscopy as our base case, but conducted sensitivity analyses based on different modes of delivery. Willingness-to-pay threshold was set at $50 000 per quality-adjusted life-year.

RESULTS

At our base case estimates, initial treatment of recurrent CDI using FMT colonoscopy was the most cost-effective strategy, with an incremental cost-effectiveness ratio of $17 016 relative to oral vancomycin. Fidaxomicin and metronidazole were both dominated by FMT colonoscopy. On sensitivity analysis, FMT colonoscopy remained the most cost-effective strategy at cure rates >88.4% and CDI recurrence rates <14.9%. Fidaxomicin required a cost <$1359 to meet our cost-effectiveness threshold. In clinical settings where FMT is not available or applicable, the preferred strategy appears to be initial treatment with oral vancomycin.

CONCLUSIONS

In this decision analysis examining treatment strategies for recurrent CDI, we demonstrate that FMT colonoscopy is the most cost-effective initial strategy for management of recurrent CDI.

Multicenter evaluation of the Quidel Lyra Direct C. difficile nucleic acid amplification assay

Clostridium difficile is a Gram-positive bacterium commonly found in health care and long-term-care facilities and is the most common cause of antibiotic-associated diarrhea. Rapid detection of this bacterium can assist physicians in implementing contact precautions and appropriate antibiotic therapy in a timely manner. The purpose of this study was to compare the clinical performance of the Quidel Lyra Direct C. difficile assay (Lyra assay) (Quidel, San Diego, CA) to that of a direct cell culture cytotoxicity neutralization assay (CCNA) and enhanced toxigenic culture. This study was performed at three geographically diverse laboratories within the United States using residual stool specimens submitted for routine C. difficile testing. Residual samples were tested using the Lyra assay on three real-time PCR platforms, and results were compared to those for direct CCNA and enhanced toxigenic culture. The test results for all platforms were consistent across all three test sites. The sensitivity and specificity of the Lyra assay on the SmartCycler II, ABI 7500 Fast DX, and ABI QuantStudio DX instruments compared to CCNA were 90.0% and 93.3%, 95.0% and 94.2%, and 93.8% and 95.0%, respectively. Compared to enhanced toxigenic culture, the sensitivity and specificity of the Lyra assay on the SmartCycler II, ABI 7500, and QuantStudio instruments were 82.1% and 96.9%, 89.3% and 98.8%, and 85.7% and 99.0%, respectively. Overall, the Lyra assay is easy to use and versatile and compares well to C. difficile culture methods.

Fidaxomicin in Clostridium difficile infection: latest evidence and clinical guidance

The incidence of Clostridium difficile infection (CDI) has risen 400% in the last decade. It currently ranks as the third most common nosocomial infection. CDI has now crossed over as a community-acquired infection. The major failing of current therapeutic options for the management of CDI is recurrence of disease after the completion of treatment. Fidaxomicin has been proven to be superior to vancomycin in successful sustained clinical response to therapy. Improved outcomes may be due to reduced collateral damage to the gut microflora by fidaxomicin, bactericidal activity, inhibition of Clostridial toxin formation and inhibition of new sporulation. This superiority is maintained in groups previously reported as being at high risk for CDI recurrence including those: with relapsed infection after a single treatment course; on concomitant antibiotic therapy; aged >65 years; with cancer; and with chronic renal insufficiency. Because the acquisition cost of fidaxomicin far exceeds that of metronidazole or vancomycin, in order to rationally utilize this agent, it should be targeted to those populations who are at high risk for relapse and in whom the drug has demonstrated superiority. In this manuscript is reviewed the changing epidemiology of CDI, current treatment options for this infection, proposed benefits of fidaxomicin over currently available antimicrobial options, available analysis of cost effectiveness of the drug, and is given recommendations for judicious use of the drug based upon the available published literature.

What does the talking?: quorum sensing signalling genes discovered in a bacteriophage genome

The transfer of novel genetic material into the genomes of bacterial viruses (phages) has been widely documented in several host-phage systems. Bacterial genes are incorporated into the phage genome and, if retained, subsequently evolve within them. The expression of these phage genes can subvert or bolster bacterial processes, including altering bacterial pathogenicity. The phage phiCDHM1 infects Clostridium difficile, a pathogenic bacterium that causes nosocomial infections and is associated with antibiotic treatment. Genome sequencing and annotation of phiCDHM1 shows that despite being closely related to other C. difficile myoviruses, it has several genes that have not been previously reported in any phage genomes. Notably, these include three homologs of bacterial genes from the accessory gene regulator (agr) quorum sensing (QS) system. These are; a pre-peptide (AgrD) of an autoinducing peptide (AIP), an enzyme which processes the pre-peptide (AgrB) and a histidine kinase (AgrC) that detects the AIP to activate a response regulator. Phylogenetic analysis of the phage and C. difficile agr genes revealed that there are three types of agr loci in this species. We propose that the phage genes belonging to a third type, agr3, and have been horizontally transferred from the host. AgrB and AgrC are transcribed during the infection of two different strains. In addition, the phage agrC appears not to be confined to the phiCDHM1 genome as it was detected in genetically distinct C. difficile strains. The discovery of QS gene homologs in a phage genome presents a novel way in which phages could influence their bacterial hosts, or neighbouring bacterial populations. This is the first time that these QS genes have been reported in a phage genome and their distribution both in C. difficile and phage genomes suggests that the agr3 locus undergoes horizontal gene transfer within this species.

Bugs or drugs: are probiotics safe for use in the critically ill?

Probiotics are living microorganisms which have demonstrated many benefits in prevention, mitigation, and treatment of various disease states in critically ill populations. These diseases include antibiotic-associated diarrhea, Clostridium difficile diarrhea, ventilator-associated pneumonia, clearance of vancomycin-resistant enterococci from the GI tract, pancreatitis, liver transplant, major abdominal surgery, and trauma. However, their use has been severely limited due to a variety of factors including a general naïveté within the physician community, lack of regulation, and safety concerns. This article focuses on uses for probiotics in prevention and treatment, addresses current concerns regarding their use as well as proposing a protocol for safe use of probiotics in the critically ill patient.

Multicenter evaluation of the Verigene Clostridium difficile nucleic acid assay

The Verigene Clostridium difficile Nucleic Acid test (Verigene CDF test) (Nanosphere, Northbrook, IL) is a multiplex qualitative PCR assay that utilizes a nanoparticle-based array hybridization method to detect C. difficile tcdA and tcdB in fecal specimens. In addition, the assay detects binary toxin gene sequences and the single base pair deletion at nucleotide 117 (Δ 117) in tcdC to provide a presumptive identification of the epidemic strain 027/NAP1/BI (referred to here as ribotype 027). This study compared the Verigene CDF test with anaerobic direct and enriched toxigenic culture on stool specimens from symptomatic patients among five geographically diverse laboratories within the United States. The Verigene CDF test was performed according to the manufacturer's instructions, and the reference methods performed by a central laboratory included direct culture onto cycloserine cefoxitin fructose agar (CCFA) and enriched culture using cycloserine cefoxitin mannitol broth with taurocholate and lysozyme. Recovered isolates were identified as C. difficile using gas liquid chromatography and were tested for toxin using a cell culture cytotoxicity neutralization assay. Strains belonging to ribotype 027 were determined by PCR ribotyping and bidirectional sequencing for Δ 117 in tcdC. A total of 1,875 specimens were evaluable. Of these, 275 specimens (14.7%) were culture positive by either direct or enriched culture methods. Compared to direct culture alone, the overall sensitivity, specificity, positive predictive value, and negative predictive value for the Verigene CDF test were 98.7%, 87.5%, 42%, and 99.9%, respectively. Compared to combined direct and enriched culture results, the sensitivity, specificity, positive predictive value, and negative predictive values of the Verigene CDF test were 90.9%, 92.5%, 67.6%, and 98.3%, respectively. Of the 250 concordantly culture-positive specimens, 59 (23.6%) were flagged as "hypervirulent"; 53 were confirmed as ribotype 027, and all 59 possessed Δ 117 in tcdC. Time to results was approximately 2.5 h per specimen. The Verigene CDF test is a novel nucleic acid microarray that reliably detects both C. difficile toxins A and B in unformed stool specimens and appears to adequately identify ribotype 027 isolates.

Culturing and maintaining Clostridium difficile in an anaerobic environment

Clostridium difficile is a Gram-positive, anaerobic, sporogenic bacterium that is primarily responsible for antibiotic associated diarrhea (AAD) and is a significant nosocomial pathogen. C. difficile is notoriously difficult to isolate and cultivate and is extremely sensitive to even low levels of oxygen in the environment. Here, methods for isolating C. difficile from fecal samples and subsequently culturing C. difficile for preparation of glycerol stocks for long-term storage are presented. Techniques for preparing and enumerating spore stocks in the laboratory for a variety of downstream applications including microscopy and animal studies are also described. These techniques necessitate an anaerobic chamber, which maintains a consistent anaerobic environment to ensure proper conditions for optimal C. difficile growth. We provide protocols for transferring materials in and out of the chamber without causing significant oxygen contamination along with suggestions for regular maintenance required to sustain the appropriate anaerobic environment for efficient and consistent C. difficile cultivation.

Genetically diverse Clostridium difficile strains harboring abundant prophages in an estuarine environment

Clostridium difficile is the leading cause of antibiotic-associated diarrheal disease in health care settings across the world. Despite its pathogenic capacity, it can be carried asymptomatically and has been found in terrestrial and marine ecosystems outside hospital environments. Little is known about these environmental strains, and few studies have been conducted on estuarine systems. Although prophage abundance and diversity are known to occur within clinical strains, prophage carriage within environmental strains of C. difficile has not previously been explored. In this study, we isolated C. difficile from sites sampled in two consecutive years in an English estuarine system. Isolates were characterized by PCR ribotype, antibiotic resistance, and motility. The prevalence and diversity of prophages were detected by transmission electron microscopy (TEM) and a phage-specific PCR assay. We show that a dynamic and diverse population of C. difficile exists within these sediments and that it includes isolates of ribotypes which are associated with severe clinical infections and those which are more frequently isolated from outside the hospital environment. Prophage carriage was found to be high (75%), demonstrating that phages play a role in the biology of these strains.