Investigating the impact of antibiotic-induced dysbiosis on protection from Clostridium difficile colitis by mouse colonic innate lymphoid cells

Innate lymphoid cells (ILCs) play a critical role in maintaining intestinal health in homeostatic and diseased conditions. During Clostridium difficile infection (CDI), IL-33 activates ILC2 to protect from colonic damage and mortality. The function of IL-33 and ILC is tightly regulated by the intestinal microbiota. We set out to determine the impact of antibiotic-induced disruption of the microbiome on ILC function. Our goal was to understand antibiotic-induced changes in ILC function on susceptibility to C. difficile colitis in a mouse model. We utilized high-throughput single-cell RNAseq to investigate the phenotypic features of colonic ILC at baseline, after antibiotic administration with or without IL-33 treatment. We identified a heterogeneous landscape of colonic ILCs with gene signatures of inflammatory, anti-inflammatory, migratory, progenitor, plastic, and antigen-presenting ILCs. Antibiotic treatment decreased ILC2 while coordinately increasing ILC1 and ILC3 phenotypes. Notably, Ifng+, Ccl5+, and Il23r+ ILC increased after antibiotics. IL-33 treatment counteracted the antibiotic effect by downregulating ILC1 and ILC3 and activating ILC2. In addition, IL-33 treatment markedly induced the expression of type 2 genes, including Areg and Il5. Finally, we identified amphiregulin, produced by ILC2, as protective during C. difficile infection. Together, our data expand our understanding of how antibiotics induce susceptibility to C. difficile colitis through their impact on ILC subsets and function.IMPORTANCEClostridium difficile infection (CDI) accounts for around 500,000 symptomatic cases and over 20,000 deaths annually in the United States alone. A major risk factor of CDI is antibiotic-induced dysbiosis of the gut. Microbiota-regulated IL-33 and innate lymphoid cells (ILCs) are important in determining the outcomes of C. difficile infection. Understanding how antibiotic and IL-33 treatment alter the phenotype of colon ILCs is important to identify potential therapeutics. Here, we performed single-cell RNAseq of mouse colon ILCs collected at baseline, after antibiotic treatment, and after IL-33 treatment. We identified heterogeneous subpopulations of all three ILC subtypes in the mouse colon. Our analysis revealed several potential pathways of antibiotic-mediated increased susceptibility to intestinal infection. Our discovery that Areg is abundantly expressed by ILCs, and the protection of mice from CDI by amphiregulin treatment, suggests that the amphiregulin-epidermal growth factor receptor pathway is a potential therapeutic target for treating intestinal colitis.

Pseudomembranous colitis as a complication in Covid-19

OBJECTIVE

Aim: To improve the results of treatment of patients with pseudomembranous colitis against the background of coronavirus infection.

PATIENTS AND METHODS

Materials and Methods: The study presents the results of a retrospective analysis of 96 patients with pseudomembranous colitis, who were treated in the infectious Covid department at the base of the Uzhhorod City Clinical Hospital since 2020 to 2022. The average age of patients was 55.2 years, there were 38 (39.5%) men and 58 (60.5%) women. Diagnosis of complications - pseudomembranous colitis (PMC) - was based on clinical data, ultrasound and CT of the abdominal organs, fibrocolonoscopy, laparoscopy.

RESULTS

Results: The frequency of PMC from the total number of patients who were in hospital treatment (8205 patients) due to COVID-19 was 1.17%, and this indicator was 0.62% in 2020, and 2.28% in 2021. Indications for operative treatment were: colon perforation - 9.4% of patients; peritonitis (diffuse, widespread) without obvious perforation of the colon wall - 85.5% of patients; mesenteric thrombosis - 4.1% of patients. In the case of perforation of the colon, resection of the colon was performed with the formation of a proximal colostomy and ileostomy. In case of mesenteric thrombosis, resection of the affected part of the small intestine was performed. In case of peritonitis without clear intraoperative detection of perforation of the colon wall, intraoperative lavage was performed.

CONCLUSION

Conclusions: 1) The frequency of detection of PMC in patients with COVID-19 in 2020 was 0.62%, and in 2021 - 2.28%. 2) The sensitivity of CT in the diagnosis of surgical complications of PMC was 72%, and the specificity was 58%. 3) Conservative treatment was effective in patients with PMC in 88.8% of cases, 21.2% had complications that required emergency surgical interventions. 4) The total mortality in patients with PMC was 11.36%, although this indicator was significantly higher in the event of surgical complications and operative treatment (22.4%).

An Updated View on the Cellular Uptake and Mode-of-Action of Clostridioides difficile Toxins

Research on the human gut pathogen Clostridioides (C.) difficile and its toxins continues to attract much attention as a consequence of the threat to human health posed by hypervirulent strains. Toxin A (TcdA) and Toxin B (TcdB) are the two major virulence determinants of C. difficile. Both are single-chain proteins with a similar multidomain architecture. Certain hypervirulent C. difficile strains also produce a third toxin, namely binary toxin CDT (C. difficile transferase). C. difficile toxins are the causative agents of C. difficile-associated diseases (CDADs), such as antibiotics-associated diarrhea and pseudomembranous colitis. For that reason, considerable efforts have been expended to unravel their molecular mode-of-action and the cellular mechanisms responsible for their uptake. Many of these studies have been conducted in European laboratories. Here, we provide an update on our previous review (Papatheodorou et al. Adv Exp Med Biol, 2018) on important advances in C. difficile toxins research.

Detection of Clostridium difficile among diarrheic children using cultural and polymerase chain reaction technique

INTRODUCTION

Clostridium difficile is the most common cause of antibiotic-associated diarrhea and colitis. Several methods are available for the detection of C. difficile in stool samples. This study aimed to use glutamate dehydrogenase (GDH), toxin detection, culture and polymerase chain reaction (PCR) techniques for the diagnosis of this pathogen.

METHODOLOGY

A total of 300 stool samples were collected from children with hospital acquired diarrhea (HA-D), community acquired diarrhea (CA-D), and hospitalized non-diarrheic children as control with ages ranging from 6 months to 6 years (mean 3.7 ± 1.7). Each stool sample was divided into two parts; one part was tested for the enzyme GDH, toxin A and B and then cultured on selective media; and the other part for direct DNA extraction.

RESULTS

From a total of 300 stool samples, 9 (3.0%) were positive for C. difficile by the PCR technique, 7 (7%) samples of which were from HA-D cases and 2 (2.0%) from CA-D cases; the control group samples were negative. The enzyme GDH was detected in 12 (12%) samples and toxins A and B in 8 (8%) samples from HA-D cases compared to 5 (5%) and 2 (2%), respectively from CA-D cases. Both GDH and the toxins were negative in control samples. Only 19 (19.0%) samples from HA-D cases gave suspected growth and all of these were negative by PCR.

CONCLUSIONS

Based on the results of this study, we conclude that the PCR technique is the only reliable method for the diagnosis of this pathogen.

Diagnosis and treatment of "chronic Lyme": primum non nocere

BACKGROUND

Approximately 10% of patients experience prolonged symptoms after Lyme disease. PTLDS (post treatment Lyme disease syndrome) is a controversial topic. It has been described as a source of overdiagnosis and off-label treatment. This review aims to describe the diagnostic errors and adverse events associated with the diagnosis and treatment of PTLDS.

METHODS

systematic review of the literature in the Medline and Cochrane Library databases, according to PRISMA criteria, including randomized clinical trials (RCT), observational studies, and case reports addressing diagnostic errors and adverse events published between January 2010 and November 2020 in English or French. Selection used a quadruple reading process on the basis of the titles and abstracts of the different articles, followed by a full reading.

RESULTS

17 studies were included: 1 RCT, 6 observational studies and 10 case reports. In the 6 observational studies, overdiagnosis rates were very high, ranging from 80 to 100%. The new diagnoses were often psychiatric, rheumatological and neurological. Disorders with somatic symptoms were often cited. Diagnostic delays were identified for cancers and frontoparietal dementia. In the RCT and observational studies, prolonged anti-infective treatments were also responsible for adverse events, with emergency room visits and/or hospitalization. The most common adverse events were diarrhea, sometimes with Clostridium difficile colitis, electrolyte abnormalities, sepsis, bacterial and fungal infections, and anaphylactic reactions.

CONCLUSION

This review highlights the risks of prolonged anti-infective treatments that have not been proven to be beneficial in PTLDS. It emphasizes the ethical imperative of the "primum non nocere" principle, which underscores the importance of not causing harm to patients. Physicians should exercise caution in diagnosing PTLDS and consider the potential risks associated with off-label treatments.

Butyrate Protects against Clostridium difficile Infection by Regulating Bile Acid Metabolism

Clostridium difficile infection (CDI) is caused by a prevalent nosocomial enteric pathogen, leading to high morbidity and mortality. CDI recurrence after antibiotic treatment is high; therefore, it is necessary to develop novel therapeutics against this enteric pathogen. Butyrate is used to treat many diseases because it provides energy, has anti-inflammatory properties, and maintains intestinal barrier function. An anti-CDI effect for butyrate has been reported; however, the specific mechanism remains elusive. This study aimed to explore the potential role and mechanism of butyrate in the treatment of CDI. Using a CDI mouse model, we found that butyrate significantly inhibited CDI development by regulating bile acid metabolism. Dysregulation of fecal bile acid was significantly higher, and levels of short-chain fatty acids were significantly lower in patients with CDI than those in controls. In CDI mice, butyrate exhibited a protective role by enhancing barrier protection, exerting anti-inflammatory effects, and regulating bile acid metabolism. Butyrate treatment also regulated the production of bile salt hydrolase (BSH) flora and activated farnesoid X receptor (FXR), and its therapeutic effects were reduced in CDI mice treated with BSH or FXR inhibitors. Thus, butyrate treatment may serve as a novel therapeutic approach for patients with CDI. IMPORTANCE Here, we show that levels of fecal short-chain fatty acids (SCFAs), particularly butyrate, are reduced, and normal colon structure is damaged in patients with CDI compared with those in healthy individuals. Bile acid (BA) metabolic disorder in patients with CDI is characterized by increased primary BA levels and decreased secondary BAs. In mice, butyrate alters BA metabolism in CDI and may play a vital role in CDI treatment by promoting secondary BA metabolism. Lastly, butyrate-mediated therapeutic effects in CDI require FXR. Our findings demonstrate that butyrate treatment significantly decreases the severity of CDI-induced colitis in mice and affects BA metabolism and FXR activation, which provides a potential alternative treatment for CDI.

Bibliometric and visual analysis of fecal microbiota transplantation research from 2012 to 2021

BACKGROUND

Fecal microbiota transplantation (FMT) is an emerging therapy for diseases associated with intestinal flora imbalance that has attracted increasing attention in recent years. This study aims to provide an overview of research trends in the field, and act as a reference point for future scientific research by analyzing the state of current research, identifying hotspots, and potential frontiers of FMT.

METHODS

Articles relating to FMT that were published between the years 2012 and 2021 were retrieved from the Web of Science Core Collection. Bibliometric analysis was performed using Microsoft Excel and CiteSpace.

RESULTS

A total of 2,403 English language articles relating to FMT research were published over the last ten years. Most of this research was carried out in the United States of America, with Harvard Medical school being the most productive institution. Much of the research was published in the PLoS One journal. Alexander Khoruts was identified as a prominent, productive researcher in the field. Keyword analysis revealed that research hot spots included gut microbiota, Clostridium difficile infection (CDI), and diseases. Burst detection indicated that future research frontiers include clinical practice guidelines and strategies.

CONCLUSION

Our analysis explored hot spots and emerging trends in the FMT field. Indications for use of FMT extended from digestive system diseases to other systemic diseases. Additionally, areas such as risk assessment and control, along with application methods were also a focus of current research. Moreover, research relating to optimization of clinical practice has excellent prospects.

The impact of dietary fibers on Clostridioides difficile infection in a mouse model

Diets rich in fiber may provide health benefits and regulate the gut microbiome, which affects the immune system. However, the role of dietary fiber in Clostridioides difficile infection (CDI) is controversial. Here, we investigated the use of fermentable fibers, such as inulin or pectin, to replace the insoluble fiber cellulose to explore how dietary fiber affects C. difficile-induced colitis in mice through intestinal microecology and metabolomics. Using C. difficile VPI 10463, we generated a mouse model of antibiotic-induced CDI. We evaluated disease outcomes and the microbial community among mice fed two fermentable fibers (inulin or pectin) versus the insoluble fiber cellulose. We analyzed and compared the gut microbiota, intestinal epithelium, cytokine levels, immune responses, and metabolites between the groups. Severe histological injury and elevated cytokine levels were observed in colon tissues after infection. Different diets showed different effects, and pectin administration protected intestinal epithelial permeability. Pectin also steadily increased the diversity of the microbiome and decreased the levels of C. difficile-induced markers of inflammation in serum and colonic tissues. The pectin group showed a higher abundance of Lachnospiraceae and a lower abundance of the conditionally pathogenic Enterobacteriaceae than the cellulose group with infection. The concentration of short-chain fatty acids in the cecal contents was also higher in the pectin group than in the cellulose group. Pectin exerted its effects through the aryl hydrocarbon receptor (AhR) pathway, which was confirmed by using the AhR agonist FICZ and the inhibitor CH2223191. Our results show that pectin alters the microbiome and metabolic function and triggers a protective immune response.

Fecal microbiota transplantation in the metabolic diseases: Current status and perspectives

With the development of microbiology and metabolomics, the relationship between the intestinal microbiome and intestinal diseases has been revealed. Fecal microbiota transplantation (FMT), as a new treatment method, can affect the course of many chronic diseases such as metabolic syndrome, malignant tumor, autoimmune disease and nervous system disease. Although the mechanism of action of FMT is now well understood, there is some controversy in metabolic diseases, so its clinical application may be limited. Microflora transplantation is recommended by clinical medical guidelines and consensus for the treatment of recurrent or refractory Clostridium difficile infection, and has been gradually promoted for the treatment of other intestinal and extraintestinal diseases. However, the initial results are varied, suggesting that the heterogeneity of the donor stools may affect the efficacy of FMT. The success of FMT depends on the microbial diversity and composition of donor feces. Therefore, clinical trials may fail due to the selection of ineffective donors, and not to faulty indication selection for FMT. A new understanding is that FMT not only improves insulin sensitivity, but may also alter the natural course of type 1 diabetes by modulating autoimmunity. In this review, we focus on the main mechanisms and deficiencies of FMT, and explore the optimal design of FMT research, especially in the field of cardiometabolic diseases.

An Update on Clostridioides difficile Binary Toxin

Infection with Clostridioides difficile (CDI), a common healthcare-associated infection, includes symptoms ranging from mild diarrhea to severe cases of pseudomembranous colitis. Toxin A (TcdA) and toxin B (TcdB) cause cytotoxicity and cellular detachment from intestinal epithelium and are responsible for CDI symptomatology. Approximately 20% of C. difficile strains produce a binary toxin (CDT) encoded by the tcdA and tcdB genes, which is thought to enhance TcdA and TcdB toxicity; however, the role of CDT in CDI remains controversial. Here, we focused on describing the main features of CDT and its impact on the host, clinical relevance, epidemiology, and potential therapeutic approaches.

The potential of microbiome replacement therapies for Clostridium difficile infection

PURPOSE OF REVIEW

There is a paradox when treating Clostridium difficile infection (CDI); treatment antibiotics reduce C. difficile colonization but cause further microbiota disruption and can lead to recurrent disease. The success of faecal microbiota transplants (FMT) in treating CDI has become a new research area in microbiome restorative therapies but are they a viable long-term treatment option?

RECENT FINDINGS

C. difficile displays metabolic flexibility to use different nutritional sources during CDI. Using microbiome therapies for the efficient restoration of bile homeostasis and to reduce the bioavailability of preferential nutrients will target the germination ability of C. difficile spores and the growth rate of vegetative cells. Several biotechnology companies have developed microbiome therapeutics for treating CDI, which are undergoing clinical trials.

SUMMARY

There is confidence in using restorative microbiome therapies for treating CDI after the demonstrated efficacy of FMT, where several biotechnology companies are aiming to supply what would be a 'first in class' treatment option. Efficient removal of C. difficile from the different intestinal biogeographies should be considered in future microbiome therapies. With the gut microbiota implicated in different diseases, more work is needed to assess the long-term consequences of microbiome therapies.

Toxin-Producing Klebsiella oxytoca in Healthy Infants: Commensal or Pathobiont?

OBJECTIVES

Klebsiella oxytoca is a gastrointestinal pathobiont with the potential to produce the toxins tilivalline and tilimycin, which cause antibiotic-associated hemorrhagic colitis. Overgrowth of toxigenic K oxytoca has recently been implicated in necrotizing enterocolitis. K oxytoca colonizes 2-9% of healthy adults, however, there is no systematic data on colonization in healthy children. We investigated K oxytoca colonization and its toxigenic properties in healthy infants.

METHODS

We sampled stool of healthy infants and determined K oxytoca colonization using stool culture and PCR (pehX). Toxin in stool was measured with HPLC/high-resolution mass spectrometry. K oxytoca isolates were typed using multi-locus sequence typing (MLST) and K oxytoca toxin PCR (npsA/B). Cytotoxin production of isolates was analyzed by MTT assay.

RESULTS

K oxytoca was detected in 30 of 61 infants (49%) using stool culture and in 45 of 61 (73%) using PCR (pehX). Toxin marker PCR (npsA/B) was positive in 66% of stool samples positive for K oxytoca PCR. Stool toxin levels were too low for quantitation but traces of tilivalline were detected. Contrarily, 49% of K oxytoca isolates demonstrated toxicity in the MTT assay. MLST revealed 36 distinct sequence types affiliated with all known K oxytoca sequence type clusters (A, B1 and B2).

CONCLUSIONS

More than 70% of healthy infants were colonized with K oxytoca. Toxin quantities in stool of colonized healthy infants were below detection level, yet half of the isolates produced toxin in vitro demonstrating their pathobiont potential. The high occurrence of toxigenic K oxytoca in healthy infants has to be considered for future disease association studies.

Delayed ileostomy closure increases the odds of Clostridium difficile infection

AIM

A diverting ileostomy is typically performed to divert intestinal contents in high-risk colorectal anastomoses. Ileostomy closure is associated with high rates of postoperative Clostridium difficile infection (CDI). Risk factors for the development of CDI are unclear; however, a correlation has been observed with delayed closure. This study aimed to assess the odds of developing CDI in patients who had a delay to reversal of ileostomy, compared to those who had no delay.

METHODS

A retrospective cohort study was conducted of patients undergoing reversal of ileostomy between 2010 and 2019 at a single tertiary centre. A delay to reversal of ileostomy was defined if the procedure was performed at >365 days following the index procedure. CDI was defined as the presence of Clostridium difficile toxin associated with diarrhoea. Univariable logistic regression analysis was performed to estimate odds of CDI for each covariable, comparing patients who had a delay to reversal of ileostomy with those who did not. Multivariable logistic regression analysis was used to adjust for the potential confounding effects of covariables.

RESULTS

Of 195 patients, 11 (5.6%), developed postoperative CDI. Multivariable analysis showed that delay to reversal of ileostomy was associated with a nearly 7-fold increase in odds of CDI (OR = 6.95, CI: 1.06-81.6; p-value = 0.03).

CONCLUSION

A delay to reversal of ileostomy of >365 days was associated with a higher incidence of CDI postoperatively. Careful consideration should be given to the timing of reversal and appropriate preoperative counselling of patients.

Novel Detection of Norovirus and Double Clostridium difficile in a Closed Cartridge System

Clostridium difficile infection (CDI) has become the main cause of diarrhea-related diseases in domestic (China) inpatients. High-sensitivity and high-specificity detection methods for CDI must be applied clinically for CDI supervisory control. In this paper, we introduce a detection method for C. difficile and Norovirus based on real-time PCR. We developed and optimized a primer-probe for Norovirus targets tcdA and tcdB with remarkably increased detection sensitivity. We then used this method in an integrated cassette, and found increased detection efficiency for Norovirus standards in the cassette compared to C. difficile samples. These results provide a basis for further exploration of automatic testing system design.

An Automated Microrobotic Platform for Rapid Detection of C. diff Toxins

OBJECTIVE

Clostridium difficile (C. diff) infection leads to hundreds of nosocomial infections, and early diagnosis of this toxin-mediated disease is important. This paper aims to develop a microrobotic system and related methods that enable the automated and rapid detection of toxins secreted by C. diff that exist in patient's stool.

METHODS

We utilize the fluorescent magnetic spore-based microrobot (FMSM), a microscale mobile sensing tool, to efficiently detect C. diff toxins by utilizing its property of selective fluorescence responses to C. diff toxins. A plug-and-play (PnP) electromagnetic coil system integrated with fluorescence microscopy is developed for actuation, control and observation of FMSMs. In order to track in real time and accurately obtain the fluorescence parameters of a FMSM under varied background noise in fluorescence signal, an image gradient-based method is proposed. For accelerating the FMSM-toxin interaction in different samples, an automated navigation control scheme for the FMSM is proposed and implemented. Moreover, data post-processing methods that can optimally extract the fluorescence decay trend from the dense and fluctuated fluorescence data are developed.

RESULTS

This automated mobile detection process finishes within only 20 minutes, and the toxin detection result is immediately given by adopting the proposed system and methods. Experimental results on different biological samples confirm the qualitative detection capability. And, C. diff toxins are automatically detected from the clinical stool of infectious patients and the relationship between the fluorescence decay and the toxin concentration is calibrated for semi-quantitative detection purpose.

SIGNIFICANCE

The proposed automated microrobotic platform provides a rapid and low-cost detection technique for C. diff toxins, and it has good competency for future clinical use.

Clostridium difficile Associated Diarrhea: Diagnostic Challenges

Clostridium difficile associated diarrhea (CDAD) is a key indicator for monitoring the success of antibiotic stewardship programs in hospitals. Indiscriminate use of antimicrobials coupled with emergence of hyper virulent strains and inadequate infection control measures in hospitals have led to rise in incidence of CDAD. In India, CDAD is still an under recognized cause of diarrhea, due to lack of clinical suspicion, difficulty in culturing the organism and nonavailibility of other diagnostic assays due to their high costs. In Indian scenario, we need to generate data on the burden of the disease by conducting robust epidemiological studies. Diagnosis and management of CDAD is a challenge in best of the setups all over the world. There is a need for development of rapid, affordable, point of care gold standard diagnostic assays.

Hydralazine-Induced ANCA Vasculitis in the Setting of Acute Clostridium Difficile Infection

We report a rare case of Hydralazine-induced ANCA associated glomerulonephritis with alveolar hemorrhage in the setting of acute Clostridium Difficile Infection. A 71-year-old Caucasian woman with hypertension, who was being treated with hydralazine 25 mg twice a day for six years, presented to the hospital with diarrhea, nausea, vomiting and anemia. She had acute kidney injury and urinalysis showed proteinuria, dysmorphic RBCs, and rare RBC cast. She was found to have Clostridium difficile colitis which was successfully treated. She became hypoxemic; CT scan findings showed bilateral pulmonary infiltrates. Broncho-alveolar lavage was consistent with pulmonary hemorrhage. Kidney biopsy revealed focal segmental necrotizing and diffuse crescentic glomerulonephritis, pauci-immune type (ANCA-associated). Hydralazine was discontinued and the patient was treated with corticosteroids, intravenous cyclophosphamide and plasmapheresis. To our knowledge, hydralazine-associated low complement in the setting of C-diff infection has not been previously reported. This is considered a potentially life-threatening condition requiring immediate discontinuation of the offending medication and expedited lifesaving measures. [Full article available at http://rimed.org/rimedicaljournal-2016-11.asp].

A tool to assess student performance in a Clostridium difficile infection simulation scenario

OBJECTIVE

To develop and validate an evaluation tool to assess student pharmacists' performance in a simulation scenario involving a patient with Clostridium difficile infection (CDI).

METHODS

The authors used an expert panel review process to establish content validity of the tool. Four faculty members used the tool to evaluate student pharmacist groups during 2011 and tested a modified version of the tool in 2012. The authors analyzed the results for each year to determine internal consistency and inter-rater reliability.

RESULTS

The 2011 tool demonstrated sound internal consistency, but several items had poor inter-rater agreement. The revised 2012 tool demonstrated acceptable internal consistency and good to excellent inter-rater agreement for all items except one.

CONCLUSIONS

The tool facilitated reliable assessment of student pharmacists' clinical decision-making during simulation performance involving a patient with CDI.

Clostridium difficile 027/BI/NAP1 encodes a hypertoxic and antigenically variable form of TcdB

The Clostridium difficile exotoxin, TcdB, which is a major virulence factor, varies between strains of this pathogen. Herein, we show that TcdB from the epidemic BI/NAP1/027 strain of C. difficile is more lethal, causes more extensive brain hemorrhage, and is antigenically variable from TcdB produced by previously studied strains of this pathogen (TcdB₀₀₃). In mouse intoxication assays, TcdB from a ribotype 027 strain (TcdB₀₂₇) was at least four fold more lethal than TcdB₀₀₃. TcdB₀₂₇ caused a previously undescribed brain hemorrhage in mice and this correlated with a heightened sensitivity of brain microvascular endothelial cells to the toxin. TcdB₀₀₃ and TcdB₀₂₇ also differed in their antigenic profiles and did not share cross-neutralizing epitopes in a major immunogenic region of the protein. Solid phase humoral mapping of epitopes in the carboxy-terminal domains (CTD) of TcdB₀₂₇ and TcdB₀₀₃ identified 11 reactive epitopes that varied between the two forms of TcdB, and 13 epitopes that were shared or overlapping. Despite the epitope differences and absence of neutralizing epitopes in the CTD of TcdB₀₂₇, a toxoid form of this toxin primed a strong protective response. These findings indicate TcdB₀₂₇ is a more potent toxin than TcdB₀₀₃ as measured by lethality assays and pathology, moreover the sequence differences between the two forms of TcdB alter antigenic epitopes and reduce cross-neutralization by antibodies targeting the CTD.

During the past decade, the C. difficile BI/NAP1/027 strain has emerged and in some settings predominated as the cause of C. difficile infection. Moreover, in some reports C. difficile BI/NAP1/027 has been associated with more severe disease. The reasons for association of this strain with more severe disease and relapse are poorly understood. We compared the toxicity and antigenic profiles of the major C. difficile virulence factor, TcdB, from a previously studied reference strain and a BI/NAP1/027 strain. The results indicate TcdB₀₂₇, the toxin from the BI/NAP1/027 strain, is more lethal and causes more extensive brain hemorrhaging than TcdB₀₀₃, the toxin produced by a reference strain of C. difficile. Furthermore, the results show that the antigenic carboxy-terminal domain (CTD) encodes at least 11 epitopes that differ between the two forms of TcdB. In line with this, experiments demonstrate that antiserum against the CTD does not cross-neutralize TcdB₀₀₃ and TcdB₀₂₇ toxicity against CHO cells, and TcdB₀₂₇ appears to be devoid of neutralizing epitopes in this domain. These findings indicate differences in TcdB₀₀₃ and TcdB₀₂₇ contribute to increased virulence of C. difficile BI/NAP1/027 and reduce the likelihood of acquired immunity providing cross-protection against infection by these strains.

Preventing ventilator-associated pneumonia: does the evidence support the practice?

Ventilator-associated pneumonia (VAP) is among the most common infections in patients requiring endotracheal tubes with mechanical ventilation. Ventilator-associated pneumonia is associated with increased hospital costs, a greater number of days in the intensive care unit, longer duration of mechanical ventilation, and higher mortality. Despite widely accepted recommendations for interventions designed to reduce rates of VAP, few studies have assessed the ability of these interventions to improve patient outcomes. As the understanding of VAP advances and new technologies to reduce VAP become available, studies should directly assess patient outcomes before the health care community implements specific prevention approaches in clinical practice.

Antibiotic therapy and treatment failure in patients hospitalized for acute exacerbations of chronic obstructive pulmonary disease

CONTEXT

Guidelines recommend antibiotic therapy for acute exacerbations of chronic obstructive pulmonary disease (COPD), but the evidence is based on small, heterogeneous trials, few of which include hospitalized patients.

OBJECTIVE

To compare the outcomes of patients treated with antibiotics in the first 2 hospital days with those treated later or not at all.

DESIGN, SETTING, AND PATIENTS

Retrospective cohort of patients aged 40 years or older who were hospitalized from January 1, 2006, through December 31, 2007, for acute exacerbations of COPD at 413 acute care facilities throughout the United States.

MAIN OUTCOME MEASURES

A composite measure of treatment failure, defined as the initiation of mechanical ventilation after the second hospital day, inpatient mortality, or readmission for acute exacerbations of COPD within 30 days of discharge; length of stay, and hospital costs.

RESULTS

Of 84,621 patients, 79% received at least 2 consecutive days of antibiotic treatment. Treated patients were less likely than nontreated patients to receive mechanical ventilation after the second hospital day (1.07%; 95% confidence interval [CI], 1.06%-1.08% vs 1.80%; 95% CI, 1.78%-1.82%), had lower rates of inpatient mortality (1.04%; 95% CI, 1.03%-1.05% vs 1.59%; 95% CI, 1.57%-1.61%), and had lower rates of readmission for acute exacerbations of COPD (7.91%; 95% CI, 7.89%-7.94% vs 8.79%; 95% CI, 8.74%-8.83%). Patients treated with antibiotic agents had a higher rate of readmissions for Clostridium difficile (0.19%; 95% CI, 0.187%-0.193%) than those who were not treated (0.09%; 95% CI, 0.086%-0.094%). After multivariable adjustment, including the propensity for antibiotic treatment, the risk of treatment failure was lower in antibiotic-treated patients (odds ratio, 0.87; 95% CI, 0.82-0.92). A grouped treatment approach and hierarchical modeling to account for potential confounding of hospital effects yielded similar results. Analysis stratified by risk of treatment failure found similar magnitudes of benefit across all subgroups.

CONCLUSION

Early antibiotic administration was associated with improved outcomes among patients hospitalized for acute exacerbations of COPD regardless of the risk of treatment failure.

Clostridium difficile PCR ribotype 027 outbreaks in the Netherlands: recent surveillance data indicate that outbreaks are not easily controlled but interhospital transmission is limited

In June 2005, shortly after outbreaks of Clostridium difficile-associated diarrhoea (CDAD) caused by PCR ribotype 027 (toxinotype III) were reported in Britain,

Small bowel review: diseases of the small intestine

In the past year there have been many advances in the area of small bowel physiology and pathology and therapy. In preparation for this review, over 1500 papers were assessed. The focus is on presenting clinically useful information for the practicing gastroenterologist. Selected important clinical learning points include the following: (1) glutamine may restore the AIDs-associated increased intestinal permeability to normal; (2) substance P is a major mediator of diarrhea caused by Costridium difficile toxin A, acting by binding to a G-protein-coupled receptor, and represents a possible 2therapeutic target; (3) the serological diagnosis of celiac disease has been greatly enhanced with the use of anti-endomysial antibody testing, and the recent antitransglutaminase; (4) a quarter of patients with celiac disease may have secondary pancreatic insufficiency and require enzyme replacement therapy; (5) in the patient with unexplained elevation in the serum transaminase concentration, consider celiac disease as an obscure possibility; (6) bosentan and endothelin receptor agonist may prove to be useful in reducing gut ischemia in patients with septic shock; and (7) the administration of recombinant human fibroblast growth factor-2 may prove to be useful to prevent radiation damage to the gastrointestinal tract.

The use of breastmilk in a neonatal unit and its relationship to protein and energy intake and growth

OBJECTIVE

A nutritional audit was performed to determine whether current feeding regimes were achieving nutritional goals and to evaluate the use of breastmilk (BM) in a neonatal unit (NNU).

METHODS

All fluid consumed or infused daily was documented with daily weight and weekly length and head circumference measurements in 90 preterm infants (gestational age 30.1 +/- 2.6 weeks) while in the NNU for 60 +/- 27 days. Daily protein and energy intakes were calculated using values for South Australian preterm BM.

RESULTS

Parenteral nutrition provided 85% of the daily energy in week 1 falling to 11% by week 6. Ninety per cent of infants received some of their mother's BM and 62% were discharged at least partially breastfed. Protein and energy intakes were 1.03 +/- 0.35 g and 55 +/- 10 kcal/kg/day in week 1, increasing to 2.52 +/- 0.60 g and 109 +/- 15 kcal/kg per day by week 4. Protein intake correlated with weight gain (r2 = 0.39). Weight gain was 14.0 +/- 2.0 g/kg per day and z-scores for weight declined from -0.25 on admission to -1.22 on discharge, P < 0.0001. When infants were divided into two groups comprising those who received BM or formula as their predominant enteral feed, growth and protein intake (but not energy intake) were lower in the BM-fed infants. However, enteral feeds were tolerated earlier and more quickly in those infants receiving predominantly BM.

CONCLUSION

Energy requirements were readily met using current feeding regimes for preterm infants but protein intakes were marginal. Mothers of preterm infants had similar breastfeeding rates to mothers of term infants in South Australia. The long-term effects of the lower growth rates of preterm infants fed predominantly BM compared with those fed predominantly formula are unknown and need be balanced against the benefits of BM.

The role of luminal nutrients in intestinal injury from mesenteric reperfusion and platelet-activating factor in the developing rat

Necrotizing enterocolitis (NEC) develops primarily after the onset of enteral feeds in the premature infant. The purpose of this study was to evaluate the influence of intestinal luminal nutrients on histologic injury and the oxidant response in a rat model of NEC. On postnatal Days 10 and 35, Sprague-Dawley rats (total n = 81) underwent abdominal laparotomy. A control group received sham-injury only. The ischemia groups received a single intraluminal injection of 0.25 ml (Day 10) or 1.0 ml (Day 35) of lactose (8.6 g/dl), casein (2.2 g/dl), corn oil (4.4 g/dl), or infant formula (Similac; 20 g/dl). After injection of the nutrient solutions, ischemia groups underwent mesenteric occlusion for 1 hr and intraluminal injection of platelet-activating factor (50 microgram/kg). Necropsies were performed after 6 hr or at demise. Intestinal samples were taken for histology, total glutathione (GSH; an antioxidant), and conjugated dienes (a lipid peroxidation product). Histologic injury was scored from 0 (normal) to 5 (transmural necrosis). Microscopic injury scores in the oil group were significantly higher than the casein group (P < 0.05) and trended toward being higher in the formula group (P = 0.085) at age 10 days. Total GSH activity was significantly higher in the sham groups than all ischemia groups on Day 10 (P < 0.001) and than the corn oil group on Day 35 (P < 0.05). GSH activity did not differ among ischemia groups. Conjugated diene concentrations were significantly higher in the casein group than the lactose and sham groups at age 10 days (P < 0.05) only. We conclude that intraluminal lipids may augment intestinal ischemic injury in the newborn (age 10 days) but not the weanling rat. While oxygen-free radicals were present during injury, lipid peroxidation from oxygen radicals was not responsible for this increase in histologic injury.