Normal flora: diversity and functions

Impact of Sublethal Concentrations of Nitrite on Goldfish (Carassius auratus) Microbiomes

Elevated concentrations of nitrite are toxic to fish and can cause a myriad of well documented issues. However, the effects of sublethal concentrations of nitrite on fish health, and specifically, fish tissue microbiomes have not been studied. To test the effects of nitrite exposure, goldfish were exposed to sublethal concentrations of nitrite, 0.0 mM, 0.1 mM, and 1.0 mM, for 2 months. The bacteria in the nose, skin, gills, and water were then extracted and sequenced to identify changes to the microbial composition. The water microbiome was not significantly changed by the added nitrite; however, each of the tissue microbiomes was changed by at least one of the treatments. The skin and gill microbiomes were significantly different between the control and 1.0 mM treatment and the nose microbiome showed significant changes between the control and both the 0.1 mM and 1.0 mM treatments. Thus, sublethal concentrations of nitrite in the environment caused a shift in the fish tissue microbiomes independently of the water microbiome. These changes could lead to an increased chance of infection, disrupt organ systems, and raise the mortality rate of fish. In systems with high nitrite concentrations, like intensive aquaculture setups or polluted areas, the effects of nitrite on the microbiomes could negatively affect fish populations.

Molecular imaging approaches to facilitate bacteria-mediated cancer therapy

Bacteria-mediated cancer therapy is a potential therapeutic strategy for cancer that has unique properties, including broad tumor-targeting ability, various administration routes, the flexibility of delivery, and facilitating the host's immune responses. The molecular imaging of bacteria-mediated cancer therapy allows the therapeutically injected bacteria to be visualized and confirms the accurate delivery of the therapeutic bacteria to the target lesion. Several hurdles make bacteria-specific imaging challenging, including the need to discriminate therapeutic bacterial infection from inflammation or other pathologic lesions. To realize the full potential of bacteria-specific imaging, it is necessary to develop bacteria-specific targets that can be associated with an imaging assay. This review describes the current status of bacterial imaging techniques together with the advantages and disadvantages of several imaging modalities. Also, we describe potential targets for bacterial-specific imaging and related applications.

Histometric parameters of the large intestine of hybrid marmosets Callithrix sp. under the influence of seasonality

Morphofunctional characteristics of the large intestine are rarely explored to understand the physiology, behavior and ecology of neotropical primates. In this study, we analyzed the histometric parameters of the large intestine of hybrid marmosets (Callithrix sp.) captured in forest fragments of Viçosa-Brazil, under seasonal interference. These animals were predominantly insectivorous in the rainy season and gummivores in the dry season. Large intestine fragments were collected and processed according to histological methods and stained with toluidine blue for general analysis, periodic acid of Schiff (PAS) and Alcian blue (AB) for goblet cells, Grimelius and Masson Fontana for argyrophil and argentaffin endocrine cells. Several histometric parameters were more expressive in the large intestine of the rainy season marmosets: greater thickness of the parietal layers, greater number of argyrophil and argentaffin endocrine cells, and AB-positive goblet cells, characteristics favor secretomotor functions and reduce the passage time of the fecal bolus, which is consistent with an insectivorous diet. In contrast, parameters such as crypt width, height of the absorptive cells and striated border, and the number of PAS-positive cells were more expressive in the dry season marmosets, reflecting the need for longer passage time for digestion and absorption of food items from tree gum, which are more complex and demand the action of microorganisms present in the large intestine, as well as greater protection against the abrasive action of dietary fibers and against microorganisms. Thus, it can be said that the marmoset's large intestine has morphological adaptations to maximize energy intake from the diet, which alternates under the influence of seasonality.

Microwave-Assisted Rapid Green Synthesis of Gold Nanoparticles Using Seed Extract of Trachyspermum ammi: ROS Mediated Biofilm Inhibition and Anticancer Activity

Green synthesis of metal nanoparticles using plant extracts as capping and reducing agents for the biomedical applications has received considerable attention. Moreover, emergence and spread of multidrug resistance among bacterial pathogens has become a major health concern and lookout for novel alternative effective drugs has gained momentum. In current study, we synthesized gold nanoparticles using the seed extract of Trachyspermum ammi (TA-AuNPs), assessed its efficacy against drug resistant biofilms of Listeria monocytogenes and Serratia marcescens, and evaluated its anticancer potential against HepG2 cancer cell lines. Microwave-assisted green synthesis of gold nanoparticles was carried out and characterization was done using UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Most nanoparticles were observed as spherical and spheroidal with few anisotropies with an average crystalline size of 16.63 nm. Synthesized TA-AuNPs demonstrated significant biofilm inhibitory activity against L. monocytogenes (73%) as well as S. marcescens (81%). Exopolysaccharide (EPS), motility, and CSH, key elements that facilitate the formation and maintenance of biofilm were also inhibited significantly at the tested sub-minimum inhibitory concentrations (sub-MICs). Further, TA-AuNPs effectively obliterated preformed mature biofilms of S. marcescens and L. monocytogenes by 64% and 58%, respectively. Induction of intracellular ROS production in TA-AuNPs treated bacterial cells could be the plausible mechanism for the reduced biofilm formation in test pathogens. Administration of TA-AuNPs resulted in the arrest of cellular proliferation in a concentration-dependent manner. TA-AuNPs decrease the intracellular GSH in HepG2 cancer cell lines, cells become more prone to ROS generation, hence induce apoptosis. Thus, this work proposes a new eco-friendly and rapid approach for fabricating NPs which can be exploited for multifarious biomedical applications.

In the Back Drop of Overuse of Synthetic Drugs, can Botanicals be One of the Answers: A Pilot Study on the Medicinal Use of Chlorophytum and Curcuma by Tribals of Central India

Background:

In several recent surveys, it has been found that more people suffer because of over and indiscriminate use of synthetic drugs, chemicals and antibiotics, particularly with regard to issues like drug sensitivity, resistance, immune disturbances, and economic burdens, ultimately leading to a weak prognosis of a large number of diseases, eventually defeating the purpose of medicinal efficacy. We propose the old age use of scientifically validated natural compounds of plants and their products for a strong immune system along with a successful treatment regimen which can be effective as well as safe without side effects.

Objective:

The aim of the present work is to evaluate the various medicinal uses and applicability of Chlorophytum borivilianum, Chlorophytum tuberosum and Curcuma longa as natural plant-based ingredients by tribal communities.

Methods:

A survey was carried on the rural folks who used natural botanicals for alleviating their several common disorders successfully. Chlorophytum species of Liliaceae and Curcuma of Zingiberaceae are traditional rare Indian medicinal herbs widely used in the indigenous system of medicine since ancient time. A total number of 196 individuals were interviewed which included both men and women, in which the main objective was to explore the different forms of these medicinal plant species used with water or with milk by tribal folk for their wide range of common ailments such as pain in joints, loss of appetite, cold, sore throat, fever and general weakness.

Results:

The tribal people were found to use these plants for many of their problems such as physical weakness, natal and postnatal problems, lactation problems, cold and fever, sore throat, inflammation, joint pain, etc. Many of them (60-80%) were able to overcome their varied health problems to a great extent such as inflammation (69.4%), joint pain and arthritis (66.6%), sore throat and cold (87.5%), physical weakness (66%), natal and postnatal problems (75%).

Conclusion:

The findings strongly support the use of natural compounds for a safe and effective means of treating loss of appetite, general weakness, pain of the joints, inflammation and other related ailments by the people of tribal areas of Border States of MP and Maharashtra, having little access to modern health care facilities.

EVALUATION OF CARBOHYDRATE AND FIBER CONSUMPTION IN PATIENTS WITH IRRITABLE BOWEL SYNDROME IN OUTPATIENT TREATMENT

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic functional condition, which main symptoms of pain, discomfort and abdominal distension, constipation, diarrhea, altered fecal consistency and sensation of incomplete evacuation can be influenced by the presence of dietary fiber and fermentable carbohydrates (FODMAPs). This study aimed to assess the relationship between the quantity of fermentable carbohydrates (FODMAP) and fiber consumed by individuals diagnosed with IBS, and their classification according to the Rome III criteria.

METHODS

A transversal study was carried out in the Intestinal Outpatient Clinic of the Gastroenterology Discipline of UNIFESP. The nutrients of interest for the study were: fiber, general carbohydrates and FODMAPs, with intake quantity measured in grams, analyzed through portions consumed. A nutrition log was used, along with a semi-quantitative questionnaire of consumption frequency.

RESULTS

The sample included 63 adult patients; 21 with constipated IBS, 21 with diarrhea IBS, and 21 with mixed IBS. Carbohydrate intake was suboptimal in 55.6% of patients in all groups; excessive consumption was identified in 38.1% of the diarrhea group, 14.3% of the mixed group and 38.1% of the constipated group. Low consumption of carbohydrates was found in 28.6% of diarrhea patients and 47.6% of the mixed group. A mean intake of 23 g of fiber per day was identified, lower than recommended.

CONCLUSION

The study identified a number of inadequacies in the consumption of different nutrients, excessive carbohydrate intake, especially FODMAPs, identified by the respondents as responsible for a worsening of their conditions. By contrast, other food groups such as meat, eggs and dairy were consumed by the sample population in insufficient quantities.

Can the use of probiotics reduce the incidence of nosocomial Clostridium difficile infection in 60 years or older patients?

Background:

Antibiotic-associated diarrhea (AAD) is a common side effect of antibiotic use. The pathogenesis of AAD may be mediated by disruption of the host’s normal flora resulting in overgrowth of pathogens. One of these pathogens is Clostridium difficile. Probiotics may help reestablish the disrupted intestinal flora and help clear the pathogen and its toxins from the host. Although numerous studies have been conducted, results are variable due to study design, type of probiotic, differing dose of probiotic, and duration of treatment. Our study aims to assess the efficacy and safety of the probiotics Lactobacillus GG and Saccharomyces boulardii for the prevention of C. difficile associated diarrhea.

Methods:

Study data were collected from two community hospitals in Kansas City over a period of 5 months. All patients in the study were initiated on antibiotics and were then given probiotics. This study was controlled and not blinded.

Results:

In data from two community hospitals, 816 patients who were being treated with antibiotics prior to the investigation served as a control; 14 (1.72%) had C. difficile Infections. During the study using probiotic administration, 803 patients also being treated with antibiotics prior to the investigation were followed and in this population; five patients (0.62%) contracted a C. difficile infection.

Use of antibiotics and the prevalence of antibiotic-associated diarrhoea in patients with spinal cord injuries: an international, multi-centre study

BACKGROUND

Little is known about the use of antibiotics and the extent of antibiotic-associated diarrhoea (AAD) in patients with spinal cord injuries (SCIs).

AIMS

To record the use of antibiotics, establish the prevalence of AAD and Clostridium difficile infection (CDI), and assess if there was any seasonal variation in antibiotic use and incidence of AAD in patients with SCIs.

METHODS

A retrospective study was conducted in six European SCI centres between October 2014 and June 2015. AAD was defined as two or more watery stools (Bristol Stool Scale type 5, 6 or 7) over 24 h.

FINDINGS

In total, 1267 adults (median age 54 years, 30.7% female) with SCIs (52.7% tetraplegia, 59% complete SCI) were included in this study. Among the 215 (17%) patients on antibiotics, the top three indications for antibiotics were urinary tract infections (UTIs), infected pressure ulcers and other skin infections. Thirty-two of these 215 (14.9%) patients developed AAD and two patients out of the total study population (2/1267; 0.16%) developed CDI. AAD was more common in summer than in spring, autumn or winter (30.3% vs 3.8%, 7.4% and 16.9%, respectively; P<0.01). AAD was associated with age ≥65 years, tetraplegia, higher body mass index, hypoalbuminaemia, polypharmacy, multiple antibiotic use and high-risk antibiotic use. Summer and winter seasons and male sex were identified as independent predictors for the development of AAD.

CONCLUSION

This survey found that AAD is common in patients with SCIs, and UTI is the most common cause of infection. Summer and winter seasons and male sex are unique predictors for AAD. Both AAD and UTIs are potentially preventable; therefore, further work should focus on preventing the over-use of antibiotics, and developing strategies to improve hospital infection control measures.

Standardizing the microbiota of fish used in research

Little attention has been paid to the effects of fish microbiotas on the reproducibility and comparability of fish studies so far. Extrinsic and intrinsic factors, such as water quality, environmental microbial populations, diet, host genetic profile, gender, age and stress status, affect fish microbiotas and create significant inter- and intra-species variations. Fish microbiotas play critical roles in many key aspects of host physiology, such as protection against pathogens, digestion and development of the digestive tract and the local immune system. Thus, greater effort should be invested in standardizing the microbiological profiles of research fish. In this context, issues requiring consideration include the establishment of isogenic and isobiotic fish lines, the standardization of rearing conditions and the development of appropriate tests to adequately describe microbial populations. There are many challenges involved in each of these issues, and the research community must decide which aspects should be standardized for each species and each type of research. For all studies in which microbiota is expected to exert an influence, thorough reporting is of paramount importance. Every step towards standardization increases study quality and simultaneously contributes to reducing the number of fish used in research, which is a legal and ethical obligation.

How Can Diet Affect the Accumulation of Advanced Glycation End-Products in the Human Body?

The accumulation of advanced glycation end products (AGEs) is associated with the complications of diabetes, kidney disease, metabolic disorders and degenerative diseases. It is recognized that the pool of glycation products found in the human body comes not only from an endogenous formation, but also from a dietary exposure to exogenous AGEs. In recent years, the development of pharmacologically-active ingredients aimed at inhibiting endogenous glycation has not been successful. Since the accumulation of AGEs in the human body appears to be progressive throughout life, an early preventive action against glycation could be effective through dietary adjustments or supplementation with purified micronutrients. The present article provides an overview of current dietary strategies tested either in vitro, in vivo or both to reduce the endogenous formation of AGEs and to limit exposure to food AGEs.

From yaks to yogurt: the history, development, and current use of probiotics

The development of probiotics, which are living bacteria or yeasts used to confer a health benefit on the host, has paralleled our research in food preservation, microbiologic identification techniques, and our understanding of how the complex interactions in microbiota impact the host's health and recovery from disease. This review briefly describes the history of probiotics, where probiotic strains were originally isolated, and the types of probiotic products currently available on the global market. In addition, the uses or indications for these probiotics are described, along with the types of clinical investigations that have been done. Continuing challenges persist for the proper probiotic strain identification, regulatory pathways, and how healthcare providers can choose a specific strain to recommend to their patients.

Episensitization: Defying Time's Arrow

The development of cancer is driven by complex genetic and epigenetic changes that result in aberrant and uncontrolled cellular growth. Epigenetic changes, in particular, are implicated in the silencing or activation of key genes that control cellular growth and apoptosis and contribute to transformative potential. The purpose of this review is to define and assess the treatment strategy of “episensitization,” or the ability to sensitize cancer cells to subsequent therapy by resetting the epigenetic infrastructure of the tumor. One important facet is resensitization by epigenetic mechanisms, which goes against the norm, i.e., challenges the long-held doctrine in oncology that the reuse of previously tried and failed therapies is a clinically pointless endeavor. Thus, episensitization is a hybrid term, which covers recent clinically relevant observations and refers to the epigenomic mechanism of resensitization. Among the many formidable challenges in the treatment of cancer, the most inevitable is the development of acquired therapeutic resistance. Here, we present the basic principles behind episensitization and highlight the evidence suggesting that epigenetically mediated histone hypoacetylation and DNA hypermethylation events may reverse clinical drug resistance. The potential reversibility of epigenetic changes and the microenvironmental impact of epigenetic control on gene expression may mediate a return to a baseline state of treatment susceptibility. Episensitization is a novel and highly practical management strategy both to prevent the practice of permanent treatment discontinuation with the occurrence of resistance, which rapidly exhausts remaining options in the pharmaceutical armamentarium and to significantly extend patient survival. Accordingly, this review highlights several epigenetic agents including decitabine, vorinostat, entinostat, 5-azacitidine, oncolytic viruses, and RRx-001.

Excretion of Host DNA in Feces Is Associated with Risk of Clostridium difficile Infection

Clostridium difficile infection (CDI) is intricately linked to the health of the gastrointestinal tract and its indigenous microbiota. In this study, we assessed whether fecal excretion of host DNA is associated with CDI development. Assuming that shedding of epithelial cell increases in the inflamed intestine, we used human DNA excretion as a marker of intestinal insult. Whole-genome shotgun sequencing was employed to quantify host DNA excretion and evaluate bacterial content in fecal samples collected from patients with incipient CDI, hospitalized controls, and healthy subjects. Human DNA excretion was significantly increased in patients admitted to the hospital for a gastrointestinal ailment, as well as prior to an episode of CDI. In multivariable analyses, human read abundance was independently associated with CDI development. Host DNA proportions were negatively correlated with intestinal microbiota diversity. Enterococcus and Escherichia were enriched in patients excreting high quantities of human DNA, while Ruminococcus and Odoribacter were depleted. These findings suggest that intestinal inflammation can occur prior to CDI development and may influence patient susceptibility to CDI. The quantification of human DNA in feces could serve as a simple and noninvasive approach to assess bowel inflammation and identify patients at risk of CDI.

Use of probiotics to correct dysbiosis of normal microbiota following disease or disruptive events: a systematic review

OBJECTIVE

To assess the evidence for the claim probiotics can correct dysbiosis of the normal microbiota resulting from disease or disruptive events.

SETTING

Systematic review of published clinical trials of patients receiving a probiotic intervention for the prevention or treatment of various diseases.

DATA SOURCES

Sources searched (1985-2013): PubMed, EMBASE, Cochrane Database of Systematic Reviews, CINAHL, AMED and ISI Web of Science. Three on-line clinical trial registries were searched: Cochrane Central Register of Controlled trials, MetaRegister of Controlled Trials and National Institutes of Health.

REVIEW METHODS

Included studies were randomised clinical trials of probiotic interventions having microbiological assays. Studies were evaluated following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for specific probiotic strains. A standard data extraction form was used to collect the raw data.

OUTCOME MEASURES

The primary outcome is the degree of microbiota correction by specific probiotic strains. Secondary outcome was the association between the degree of dysbiosis correction and clinical efficacy.

RESULTS

The review of the literature found three distinct study designs: model A (restoration) assayed patients enrolled with a healthy, undisturbed microbiota and then assayed postdisruptive event and probiotic therapy; model B (alteration) assayed patients with pre-existing disrupted microbiota and then postprobiotic therapy; model C (no dysbiosis) assayed volunteers with no disruptive event prebiotic and postprobiotic. From a total of 63 trials, 83% of the probiotic products using model A restored the microbiota, 56% using model B improved the microbiota and only 21% using model C had any effect on microbiota. Clinical efficacy was more commonly associated with strains capable of restoration of the normal microbiota.

CONCLUSIONS

The ability to assess the degree of dysbiosis improvement is dependent on the enrolled population and the timing of microbiological assays. The functional claim for correcting dysbiosis is poorly supported for most probiotic strains and requires further research.

TRIAL REGISTRATION NUMBER

PROSPERO (CRD42014007224).

A Lactobacillus casei Shirota probiotic drink reduces antibiotic-associated diarrhoea in patients with spinal cord injuries: a randomised controlled trial

Certain probiotics may prevent the development of antibiotic-associated diarrhoea (AAD) and Clostridium difficile-associated diarrhoea (CDAD), but their effectiveness depends on both strain and dose. There are few data on nutritional interventions to control AAD/CDAD in the spinal cord injury (SCI) population. The present study aimed to assess (1) the efficacy of consuming a commercially produced probiotic containing at least 6·5 × 10⁹ live Lactobacillus casei Shirota (LcS) in reducing the incidence of AAD/CDAD, and (2) whether undernutrition and proton pump inhibitors (PPI) are risk factors for AAD/CDAD. A total of 164 SCI patients (50·1 (sd 17·8) years) with a requirement for antibiotics (median 21 d, range 5-366) were randomly allocated to receive LcS (n 76) or no probiotic (n 82). LcS was given once daily for the duration of the antibiotic course and continued for 7 days thereafter. Nutritional risk was assessed by the Spinal Nutrition Screening Tool. The LcS group had a significantly lower incidence of AAD (17·1 v. 54·9%, P< 0·001). At baseline, 65% of patients were at undernutrition risk. Undernutrition (64·1 v. 33·3%, P< 0·01) and the use of PPI (38·4 v. 12·1 %, P= 0·022) were found to be associated with AAD. However, no significant difference was observed in nutrient intake between the groups. The multivariate logistic regression analysis identified poor appetite ( < 1/2 meals eaten) (OR 5·04, 95% CI 1·28, 19·84) and no probiotic (OR 8·46, 95% CI 3·22, 22·20) as the independent risk factors for AAD. The present study indicated that LcS could reduce the incidence of AAD in hospitalised SCI patients. A randomised, placebo-controlled study is needed to confirm this apparent therapeutic success in order to translate into improved clinical outcomes.

Gut solutions to a gut problem: bacteriocins, probiotics and bacteriophage for control of Clostridium difficile infection

Clostridium difficile infection (CDI) is a major cause of morbidity and mortality among hospitalized patients and imposes a considerable financial burden on health service providers in both Europe and the USA. The incidence of CDI has dramatically increased in recent years, partly due to the emergence of a number of hypervirulent strains. The most commonly documented risk factors associated with CDIs are antibiotic usage leading to alterations of the gut microbiota, age >65 years and long-term hospital stay. Since standard therapies for antibiotic-associated diarrhoea and CDI have limited efficacy, there is now an urgent need for alternative therapeutics. In this review, we outline the current state of play with regard to the potential of gut-derived bacteriocins, probiotics and phage to act as antimicrobial agents against CDI in the human gut.

A review of the pathogenesis of adult peritonsillar abscess: time for a re-evaluation

OBJECTIVES

To perform a multifactorial exploration of the aetiology of peritonsillar abscess (PTA) in adults, in order to develop greater clinical understanding of the condition and improve management.

DESIGN

A literature review exploring key pathogens, predisposing host factors and current pathogenic hypotheses.

METHODS

A PubMed search for articles published between January 1980 and January 2012 using the terms 'peritonsillar abscess AND microbiology', 'peritonsillar abscess AND pathophysiology' and 'peritonsillar abscess AND etiology'.

RESULTS

Major pathogens in PTA are opportunistic microflora. Group A streptococcal PTA infections present differently from polymicrobial PTA. A number of host factors influence the conditions required for the pathogenesis of PTA.

CONCLUSIONS

PTA is clinically distinct from acute tonsillitis and occurs in people with a chronic underlying susceptibility. Targeting host factors, including oral hygiene, antibiotic use and smoking, may prevent PTA. Re-education of clinicians concerning the aetiology of PTA is necessary for appropriate disease management.

A meta-analysis of probiotic efficacy for gastrointestinal diseases

Background

Meta-analyses on the effects of probiotics on specific gastrointestinal diseases have generally shown positive effects on disease prevention and treatment; however, the relative efficacy of probiotic use for treatment and prevention across different gastrointestinal diseases, with differing etiology and mechanisms of action, has not been addressed.

Methods/Principal Findings

We included randomized controlled trials in humans that used a specified probiotic in the treatment or prevention of Pouchitis, Infectious diarrhea, Irritable Bowel Syndrome, Helicobacter pylori, Clostridium difficile Disease, Antibiotic Associated Diarrhea, Traveler's Diarrhea, or Necrotizing Enterocolitis. Random effects models were used to evaluate efficacy as pooled relative risks across the eight diseases as well as across probiotic species, single vs. multiple species, patient ages, dosages, and length of treatment. Probiotics had a positive significant effect across all eight gastrointestinal diseases with a relative risk of 0.58 (95% (CI) 0.51–0.65). Six of the eight diseases: Pouchitis, Infectious diarrhea, Irritable Bowel Syndrome, Helicobacter pylori, Clostridium difficile Disease, and Antibiotic Associated Diarrhea, showed positive significant effects. Traveler's Diarrhea and Necrotizing Enterocolitis did not show significant effects of probiotcs. Of the 11 species and species mixtures, all showed positive significant effects except for Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium infantis. Across all diseases and probiotic species, positive significant effects of probiotics were observed for all age groups, single vs. multiple species, and treatment lengths.

Conclusions/Significance

Probiotics are generally beneficial in treatment and prevention of gastrointestinal diseases. Efficacy was not observed for Traveler's Diarrhea or Necrotizing Enterocolitis or for the probiotic species L. acidophilus, L. plantarum, and B. infantis. When choosing to use probiotics in the treatment or prevention of gastrointestinal disease, the type of disease and probiotic species (strain) are the most important factors to take into consideration.

Clostridium difficile infection: toxins and non-toxin virulence factors, and their contributions to disease establishment and host response

Clostridium difficile infection is the leading cause of antibiotic- and healthcare-associated diarrhea, and its containment and treatment imposes a significant financial burden, estimated to be over $3 billion in the USA alone. Since the year 2000, CDI epidemics/outbreaks have occurred in North America, Europe and Asia. These outbreaks have been variously associated with, or attributed to, the emergence of Clostridium difficile strains with increased virulence, an increase in resistance to commonly used antimicrobials such as the fluoroquinolones, or host susceptibilities, including the use of gastric acid suppressants, to name a few. Efforts to elucidate C. difficile pathogenic mechanisms have been hampered by a lack of molecular tools, manipulatable animal models, and genetic intractability of clinical C. difficile isolates. However, in the past 5 y, painstaking efforts have resulted in the unraveling of multiple C. difficile virulence-associated pathways and mechanisms. We have recently reviewed the disease, its associated risk factors, transmission and interventions (Viswanathan, Gut Microbes 2010). This article summarizes genetics, non-toxin virulence factors, and host-cell biology associated with C. difficile pathogenesis as of 2011, and highlights those findings/factors that may be of interest as future intervention targets.

Bacterial profile of the oropharynx in infants: an assessment of the confounding factors for colonization

OBJECTIVE

To determine the composition of non pathogenic microflora (NPM) and pathogenic microflora (PM) and the assessment of factors affecting their colonization in the oropharynx.

METHODS

Oropharyngeal swabs were obtained from 464 infants, aged 15 days to I year, with or without clinical signs and symptoms of upper respiratory tract infection (URTI), for the current study.Culture was done on blood and chocolate agar, and the colonies were identified using standard microbiological procedures.

RESULTS

The influence of age, presence of siblings and feeding patterns on colonization of oropharynx and the profile of NPM and PM in symptomatic and asymptomatic infants was studied. Colonization of oropharynx by NPM decreased with age whereas by PM increased with age significantly. Isolation of PM significantly increased in cases having siblings less than 18 years of age at home. Season showed a significant influence on the colonization of microflora in the oropharynx. Colonization by NPM was significantly higher in exclusively breast fed (EBF) infants, whereas by PM was higher in mixed fed (MF) infants. Symptomatic infants were higher in the MF group than in EBF group. Certain species of NPM exhibited significant inhibitory effects on colonization of PM.

CONCLUSIONS

Assessment of the factors influencing the oropharyngeal colonization of microflora in infants identifies the risk factors for various infections in later life.

Effects on weight gain and gut microbiota in rats given bacterial supplements and a high-energy-dense diet from fetal life through to 6 months of age

The aim of the present study was to assess the long-term effects of a high-energy-dense diet, supplemented with Lactobacillus plantarum (Lp) or Escherichia coli (Ec), on weight gain, fattening and the gut microbiota in rats. Since the mother's dietary habits can influence offspring physiology, dietary regimens started with the dams at pregnancy and throughout lactation and continued with the offspring for 6 months. The weight gain of group Lp was lower than that of groups C (control) and Ec (P = 0·086). More retroperitoneal adipose tissue (P = 0·030) and higher plasma leptin (P = 0·035) were observed in group Ec compared with group Lp. The viable count of Enterobacteriaceae was higher in group Ec than in group Lp (P = 0·019), and when all animals were compared, Enterobacteriaceae correlated positively with body weight (r 0·428, P = 0·029). Bacterial diversity was lower in group Ec than in groups C (P ≤ 0·05) and Lp (P ≤ 0·05). Firmicutes, Bacteroidetes and Verrucomicrobia dominated in all groups, but Bacteroidetes were more prevalent in group C than in groups Lp (P = 0·036) and Ec (P = 0·056). The same five bacterial families dominated the microbiota of groups Ec and C, and four of these were also present in group Lp. The other five families dominating in group Lp were not found in any of the other groups. Multivariate data analysis pointed in the same directions as the univariate statistics. The present results suggest that supplementation of L. plantarum or E. coli can have long-term effects on the composition of the intestinal microbiota, as well as on weight gain and fattening.

[The microbiota and infectious diarrhea]

Understanding the importance of the fecal microbiota has been key in understanding the pathophysiology of some infectious diarrheas. In addition to normal protective measures of bile, gastric acid, and immune response, among others, we now know that the healthy gut flora protects us from some infectious diarrheas. Antibiotic associated diarrhea (AAD) is an excellent example, as antibiotics perturb the normal flora; the resulting diarrhea may be due to changes in short chain fatty acid metabolism. A severe form of AAD is due to Clostridium difficile, a pathogen that can cause severe diarrhea, colitis and even death. Recurrent Clostridium difficile diarrhea is a difficult clinical problem to treat successfully because one recurrence makes further recurrences more likely, probably because antibiotics are still needed to treat and thus the fecal flora remains abnormal. There is no single effective treatment but therapies include pulsed and tapered antibiotics, the probiotic Saccharomyces boulardii as an adjunct to antibiotics, and even fecal flora reconstitution. It is likely that we will learn even more in the future about the beneficial effect of our microbiota.

Effect of probiotic Lactobacillus (Lacidofil® cap) for the prevention of antibiotic-associated diarrhea: a prospective, randomized, double-blind, multicenter study

Antibiotic-associated diarrhea (AAD) is a common complication of antibiotic use. There is growing interest in probiotics for the treatment of AAD and Clostridium difficile infection because of the wide availability of probiotics. The aim of this multicenter, randomized, placebo-controlled, double-blind trial was to assess the efficacy of probiotic Lactobacillus (Lacidofil® cap) for the prevention of AAD in adults. From September 2008 to November 2009, a total of 214 patients with respiratory tract infection who had begun receiving antibiotics were randomized to receive Lactobacillus (Lacidofil® cap) or placebo for 14 days. Patients recorded bowel frequency and stool consistency daily for 14 days. The primary outcome was the proportion of patients who developed AAD within 14 days of enrollment. AAD developed in 4 (3.9%) of 103 patients in the Lactobacillus group and in 8 (7.2%) of 111 patients in the placebo group (P=0.44). However, the Lactobacillus group showed lower change in bowel frequency and consistency (50/103, 48.5%) than the placebo group (35/111, 31.5%) (P=0.01). Although the Lacidofil® cap does not reduce the rate of occurrence of AAD in adult patients with respiratory tract infection who have taken antibiotics, the Lactobacillus group maintains their bowel habits to a greater extent than the placebo group.

Evidence-based review of probiotics for antibiotic-associated diarrhea and Clostridium difficile infections

Probiotics are living microbes taken to confer a health benefit on the host. Although probiotics have a long history of use in Europe and Asia and have been on the U.S. market for over 14 years, there is still confusion about how to effectively use them. The use of probiotics for the prevention of antibiotic-associated diarrhea (AAD) and the treatment of Clostridium difficile infections (CDI) has been tested in randomized controlled clinical trials. This paper will review the evidence supporting probiotic therapy for these two diseases and also review the advantages and disadvantages of probiotics. The advantages of probiotic therapy include multiple mechanisms of action against pathogens, the ability to interact with the host's natural defense systems, survival to the target organ and a good risk to benefit ratio. Disadvantages of probiotics include lack of standardization for clinical trial designs, variations in regulatory standards, poor quality control for some products and infrequent serious adverse reactions. Overall, probiotics offer a promising strategy for the prevention and treatment for AAD and CDI.

Fecal bacteriotherapy for recurrent Clostridium difficile infection

Clostridium difficile infection (CDI) has emerged as a major complication associated with the use of systemic antimicrobial agents. Broad-spectrum antimicrobial agents disrupt the ecological bacterial balance in the colon and create an opportunity for C. difficile overgrowth with attendant production of toxins and clinical symptoms of colitis. Recommended therapies for CDI include oral administration of metronidazole or vancomycin for 10-14 days. However, 5% to 35% of patients experience infection relapse after completion of treatment. Recently, patients who failed to resolve their infection with conventional therapies and went on to develop chronic relapsing CDI were successfully treated with fecal bacteriotherapy. Stool obtained from a healthy individual was instilled from either end of the GI tract. Although the published experience with fecal bacteriotherapy is still limited, the published treatment results for 100 patients have demonstrated an average success-rate close to 90%. Fecal bacteriotherapy is a low tech procedure which is easy to perform, and breaks the cycles of repeated antibiotic use, which in turn reduces the risk of antibiotic associated resistance and adds potential cost savings when compared to repeated antibiotic administration and hospitalizations.

Impact of a jelly containing short-chain fructo-oligosaccharides and Sideritis euboea extract on human faecal microbiota

In this randomized, double-blinded, placebo-controlled clinical study we aimed to evaluate the in vivo prebiotic effects of a functional food containing short-chain fructo-oligosaccharides (sc-FOS) and Sideritis euboea extract on human faecal microflora. Sixty-four healthy volunteers 26 men and 38 women (age range: 22-51) were assigned to consume daily a jelly containing 5 g sc-FOS and 0.3 g S.euboea extract or a placebo for 30 d. Stool samples were collected prior to the study on day 15 and 30 of intervention and 2 weeks after. Enumeration of faecal bacteria was performed by plate count techniques. Gastrointestinal side effects were recorded during the treatment period. Data demonstrated a significant bifidogenic effect of the experimental jelly compared to the placebo after 15 [9.54+/-0.83 vs. 8.57+/-1.91 log(10)CFU (colony forming units)/g faeces P=0.001] and 30 d of consumption (9.34+/-1.04 vs. 8.57+/-1.98 log(10)CFU/g faeces P=0.027) and significant higher bifidobacterial levels in the sc-FOS+extract group 2 weeks after the end of intervention (9.33+/-0.61 vs. 8.79+/-0.93 log(10)CFU/g faeces P=0.015). A trend for greater flatulence was detected after 15 d of functional food ingestion with no further differences in gastrointestinal symptoms. In conclusion the daily intake of a jelly containing sc-FOS and S.euboea extract is well-tolerated and demonstrated significant bifidogenic properties in healthy volunteers consuming their usual diets.

Probiotic therapy to men with incipient arteriosclerosis initiates increased bacterial diversity in colon: a randomized controlled trial

OBJECTIVE

This study aimed to clarify the microbial change in the intestinal microbiota in patients, with cardiovascular disease, consuming a drink with high numbers of live Lactobacillus plantarum.

METHODS

Sixteen males, with atherosclerotic plaque on the carotid wall, were randomly selected from a larger cohort and included in this double blind, placebo controlled study. Colonic biopsies, taken before and after four weeks of probiotic treatment, were analysed with Terminal Restriction Fragment Length Polymorphism, including digestion with MspI and HaeIII. Microbial diversity was calculated, short-chain fatty acids in faeces, and blood markers were analysed.

RESULTS

Consumption of one probiotic strain of L. plantarum (DSM 9843) increased intestinal microbial diversity. The probiotic group had an increased diversity after consumption of the probiotic drink compared to the change in the placebo group when Shannon and Weaner diversity index (MspI and HaeIII, p=0.026) and Simpson index of diversity (MspI, p=0.044 and HaeIII, p=0.026) were calculated. The fermentation pattern of short-chain fatty acids in faeces were unaffected for most acids, but the probiotic group had decreased concentration of isovaleric acid (p=0.006) and valeric acid (p=0.029). Viable count of lactobacilli increased in the probiotic group (p=0.001), but no significant changes in blood markers were observed.

CONCLUSION

Administration of a single-strain probiotic increases the bacterial diversity in the gut, and affects the concentration of some short-chain fatty acids. Consumption of the single strain L. plantarum DSM 9843 might be a strategy to favour a diverse intestinal microbiota, which is beneficial for the host.

Lactobacillus fermentum ME-3 - an antimicrobial and antioxidative probiotic

The paper lays out the short scientific history and characteristics of the new probiotic Lactobacillus fermentum strain ME-3 DSM-14241, elaborated according to the regulations of WHO/FAO (2002). L. fermentum ME-3 is a unique strain of Lactobacillus species, having at the same time the antimicrobial and physiologically effective antioxidative properties and expressing health-promoting characteristics if consumed. Tartu University has patented this strain in Estonia (priority June 2001, patent in 2006), Russia (patent in 2006) and the USA (patent in 2007). The paper describes the process of the identification and molecular typing of this probiotic strain of human origin, its deposition in an international culture collection, and its safety assessment by laboratory tests and testing on experimental animals and volunteers. It has been established that L. fermentum strain ME-3 has double functional properties: antimicrobial activity against intestinal pathogens and high total antioxidative activity (TAA) and total antioxidative status (TAS) of intact cells and lysates, and it is characterized by a complete glutathione system: synthesis, uptake and redox turnover. The functional efficacy of the antimicrobial and antioxidative probiotic has been proven by the eradication of salmonellas and the reduction of liver and spleen granulomas in Salmonella Typhimurium-infected mice treated with the combination of ofloxacin and L. fermentum strain ME-3. Using capsules or foodstuffs enriched with L. fermentum ME-3, different clinical study designs (including double-blind, placebo-controlled, crossover studies) and different subjects (healthy volunteers, allergic patients and those recovering from a stroke), it has been shown that this probiotic increased the antioxidative activity of sera and improved the composition of the low-density lipid particles (LDL) and post-prandial lipids as well as oxidative stress status, thus demonstrating a remarkable anti-atherogenic effect. The elaboration of the probiotic L. fermentum strain ME-3 has drawn on wide international cooperative research and has taken more than 12 years altogether. The new ME-3 probiotic-containing products have been successfully marketed and sold in Baltic countries and Finland.

Development of Candida-associated denture stomatitis: new insights

Despite therapeutic progress, opportunistic oral fungal infectious diseases have increased in prevalence, especially in denture wearers. The combination of entrapment of yeast cells in irregularities in denture-base and denture-relining materials, poor oral hygiene and several systemic factors is the most probable cause for the onset of this infectious disease. Hence colonization and growth on prostheses by Candida species are of clinical importance. The purpose of this review is to critically discuss several key factors controlling the adhesion of Candida species which are relevant to denture-associated stomatitis. Although there is some consensus on the role of surface properties, studies on several other factors, as the use of denture liners, salivary properties and yeast-bacterial interactions, have shown contradictory findings. A comprehensive fundamental understanding is hampered by conflicting findings due to the large variations in experimental protocols, while other factors have never been thoroughly studied. Surface free energy and surface roughness control the initial adherence, but temporal changes have not been reported. Neither have in vivo studies shown if the substratum type is critical in dictating biofilm accumulation during longer periods in the oral environment. The contribution of saliva is unclear due to factors like variations in its collection and handling. Initial findings have disclosed that also bacteria are crucial for the successful establishment of Candida in biofilms, but the clinical significance of this observation is yet to be confirmed. In conclusion, there is a need to standardize experimental procedures, to bridge the gap between laboratory and in vivo methodologies and findings and – in general – to thoroughly investigate the factors that modulate the initial attachment and subsequent colonization of denture-base materials and the oral mucosa of patients subjected to Candida infections. Information on how these factors can be controlled is required and this may help to prevent the disease. The societal impact of such information is significant given the magnitude of the candidosis problem worldwide.

New agents for Clostridium difficile-associated disease

BACKGROUND

Clostridia-derived diseases, in particular C. difficile-associated disease (CDAD), have been increasing in incidence, severity, and morbidity. The mainstay of treatment options has relied upon metronidazole and vancomycin, but these treatments routinely result in high relapse rates (20%) and, in the case of metronidazole, decreasing efficacy.

OBJECTIVE

Evaluate and compare the current clinical and preclinical therapies of CDAD.

METHODS

RESULTS/CONCLUSION

The new antibiotics in development and preclinical development reflect next-generation versions of older drugs or two new mechanism-of-action class drugs (OPT-80, REP3123). Based on the current preclinical and clinical data, the next-generation drugs impart only a subtle difference from the intrinsic weaknesses of their genre. In contrast, OPT-80 and REP3123 seem to be differentiated.

The effect of lactic acid bacteria isolates on the urinary tract pathogens to infants in vitro

Urinary tract infections are common clinical problems in children, even though lots of treatment strategies have been tried. Many studies of the application of probiotics for urinary tract infection in female adults exist, but there is a lack of studies in children. The aims of this study were to screen probiotic strains for inhibiting the uropathogens in vitro, to find candidates for in vivo study. Nine strains of E. coli were isolated from children with urinary tract infection and six uropathogens were obtained from Korean Collection for Type Cultures and American Type Culture Collection. Also 135 lactic acid bacteria (LAB) strains were isolated from healthy children, and were identified through physiologic, biochemical methods, 16S rDNA PCR, and data analysis. And with agar disk diffusion assay technique the antimicrobial activities of these LAB strains against those uropathogens were examined. Three strains of separated LAB strains demonstrated major antimicrobial activity against all the uropathogens. In the agar disk diffusion assay technique, antimicrobial activities increased most in the 4th day culture broth with separated Lactobacillus. In summary, some LAB can be used as candidates to develop the probiotic microorganisms that inhibit uropathogens in children, and are expected to be applied to treatment and prevention of pediatric urinary tract infection.

Antibiotic-associated diarrhea: epidemiology, trends and treatment

A common complication of antibiotic use is the development of gastrointestinal disease. This complication ranges from mild diarrhea to pseudomembranous colitis. Outbreaks of antibiotic-associated diarrhea (AAD) may also occur in healthcare settings, usually caused by Clostridium difficile. AAD typically occurs in 5-35% of patients taking antibiotics and varies depending upon the specific type of antibiotic, the health of the host and exposure to pathogens. The pathogenesis of AAD may be mediated through the disruption of the normal microbiota resulting in pathogen overgrowth or metabolic imbalances. The key to addressing AAD is prompt diagnosis followed by effective treatment and institution of control measures. Areas of active research include the search for other etiologies and more effective treatments.

Meta-analysis of probiotics for the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic condition affecting 3%-25% of the general population. As no curative treatment is available, therapy is aimed at reducing symptoms, often with little success. Because alteration of the normal intestinal microflora has been observed in IBS, probiotics (beneficial microbes taken to improve health) may be useful in reducing symptoms. This paper systematically reviews randomized, controlled, blinded trials of probiotics for the treatment of IBS and synthesizes data on efficacy across trials of adequate quality. PubMed, Medline, Google Scholar, NIH registry of clinical trials, metaRegister, and the Cochrane Central Register of Controlled Trials were searched from 1982-2007. We also conducted secondary searches of reference lists, reviews, commentaries, relevant articles on associated diseases, books and meeting abstracts. Twenty trials with 23 probiotic treatment arms and a total of 1404 subjects met inclusion criteria. Probiotic use was associated with improvement in global IBS symptoms compared to placebo [pooled relative risk (RR_pooled) 0.77, 95% confidence interval (95% CI) 0.62-0.94]. Probiotics were also associated with less abdominal pain compared to placebo [RR_pooled = 0.78 (0.69-0.88)]. Too few studies reported data on other IBS symptoms or on specific probiotic strains to allow estimation of a pooled RR. While our analyses suggest that probiotic use may be associated with improvement in IBS symptoms compared to placebo, these results should be interpreted with caution, given the methodological limitations of contributing studies. Probiotics warrant further study as a potential therapy for IBS.

Tolevamer, an anionic polymer, neutralizes toxins produced by the BI/027 strains of Clostridium difficile

Clostridium difficile-associated diarrhea (CDAD) is caused by the toxins the organism produces when it overgrows in the colon as a consequence of antibiotic depletion of normal flora. Conventional antibiotic treatment of CDAD increases the likelihood of recurrent disease by again suppressing normal bacterial flora. Tolevamer, a novel toxin-binding polymer, was developed to ameliorate the disease without adversely affecting normal flora. In the current study, tolevamer was tested for its ability to neutralize clostridial toxins produced by the epidemic BI/027 strains, thereby preventing toxin-mediated tissue culture cell rounding. The titers of toxin-containing C. difficile culture supernatants were determined using confluent cell monolayers, and then the supernatants were used in assays containing dilutions of tolevamer to determine the lowest concentration of tolevamer that prevented > or =90% cytotoxicity. Tolevamer neutralized toxins in the supernatants of all C. difficile strains tested. Specific antibodies against the large clostridial toxins TcdA and TcdB also neutralized the cytopathic effect, suggesting that tolevamer is specifically neutralizing these toxins and that the binary toxin (whose genes are carried by the BI/027 strains) is not a significant source of cytopathology against tissue culture cells in vitro.

Tonic shock induces detachment of Giardia lamblia

BACKGROUND

The parasite Giardia lamblia must remain attached to the host small intestine in order to proliferate and subsequently cause disease. However, little is known about the factors that may cause detachment in vivo, such as changes in the aqueous environment. Osmolality within the proximal small intestine can vary by nearly an order of magnitude between host fed and fasted states, while pH can vary by several orders of magnitude. Giardia cells are known to regulate their volume when exposed to changes in osmolality, but the short-timescale effects of osmolality and pH on parasite attachment are not known.

METHODOLOGY AND PRINCIPAL FINDINGS

We used a closed flow chamber assay to test the effects of rapid changes in media osmolality, tonicity, and pH on Giardia attachment to both glass and C2(Bbe)-1 intestinal cell monolayer surfaces. We found that Giardia detach from both surfaces in a tonicity-dependent manner, where tonicity is the effective osmolality experienced by the cell. Detachment occurs with a characteristic time constant of 25 seconds (SD = 10 sec, n = 17) in both hypo- and hypertonic media but is otherwise insensitive to physiologically relevant changes in media composition and pH. Interestingly, cells that remain attached are able to adapt to moderate changes in tonicity. By exposing cells to a timed pattern of tonicity variations and adjustment periods, we found that it is possible to maximize the tonicity change experienced by the cells, overcoming the adaptive response and resulting in extensive detachment.

CONCLUSIONS AND SIGNIFICANCE

These results, conducted with human-infecting Giardia on human intestinal epithelial monolayers, highlight the ability of Giardia to adapt to the changing intestinal environment and suggest new possibilities for treatment of giardiasis by manipulation of tonicity in the intestinal lumen.

Fluoroquinolone use and risk factors for Clostridium difficile-associated disease within a Veterans Administration health care system

BACKGROUND

Prompted by the changing profile of Clostridium difficile infection and the impact of formulary policies in hospitals, we performed this study when an increase in the incidence of C. difficile-associated disease was noted at our health care center (Veterans Administration Puget Sound Health Care System, Seattle, Washington).

METHODS

A retrospective, matched case-control study of patients presenting to the Veterans Administration Puget Sound Health Care System, Seattle, Washington during 2004 was performed. Conditional logistic analysis determined risk factors for case patients, defined as individuals with diarrhea and test results (i.e., culture or toxin assay results) positive for C. difficile, and control subjects, defined as individuals with diarrhea and test results negative for C. difficile.

RESULTS

C. difficile-associated disease incidence was 29.2 cases per 10,000 inpatient-days. The increase in the incidence of C. difficile-associated diarrhea that paralleled increased gatifloxacin use was not attributable to use of the antimicrobial but was a reflection of seasonal variation in the rate of C. difficile-associated disease. Multivariate analysis controlling for the time at which the assay was performed, the age of the patient, ward, and source of acquisition (community-acquired vs. nosocomial disease) found 6 significant risk factors for C. difficile-associated diarrhea: receipt of clindamycin (adjusted odds ratio [aOR], 29.9; 95% confidence interval [CI], 3.58-249.4), receipt of penicillin (aOR, 4.1; 95% CI, 1.2-13.9), having a lower intestinal condition (aOR, 2.8; 95% CI, 1.3-6.1), total number of antibiotics received (aOR, 1.4; 95% CI, 1.1-1.7), number of prior hospital admissions (aOR, 1.3; 95% CI, 1.1-1.6), and number of comorbid conditions (aOR, 1.3; 95% CI, 1.1-1.5).

CONCLUSIONS

The increase in the number of cases of C. difficile-associated disease was not attributable to a formulary change of fluoroquinolones; instead, the incidence was within expected seasonal variations for C. difficile-associated disease. Recognition of community-acquired cases and the use of culture may help to identify additional cases of C. difficile-associated disease. Early diagnosis and treatment of C. difficile cases may shorten the duration of hospital stays and reduce the number of outbreaks and readmissions, mortality, and other consequences of C. difficile infection.

Colonization and impact of disease and other factors on intestinal microbiota

The aim of this study was to review the process of microbial colonization and the environmental and host factors that influence colonization and microbial succession. The impact of some diseases on intestinal microbiota composition is also described. Microbial colonization of the gut by maternal vaginal and fecal bacteria begins during and after birth. During the first 2 years of life, specific microbes become established in a process designated microbial succession. Microbial succession in the gastrointestinal tract is influenced by numerous external and internal host-related factors, and by the second year of life, the intestinal microbiota composition is considered identical to that of adults. Nevertheless, intestinal microbiota in both infants and adults remain incompletely characterized and their diversity poorly defined. The main explanation is that many intestinal bacteria that live in an anaerobic environment are difficult or impossible to culture outside the intestine. However, recent advances in molecular biology techniques have initiated the description of new bacteria species. The composition of gut microbiota can be modulated by host, environmental, and bacterial factors, and strong evidence has emerged of substantial modifications during illness or exposure to threatening experiences. It has been postulated that improvements in hygienic measures have led to an increase in allergic diseases ("hygiene hypothesis"). Alterations in gut microbiota and their functions have been widely associated with many chronic and degenerative diseases, including inflammatory bowel disease, colon cancer, and rheumatoid arthritis.

The micro-flora of the small bowel in health and disease

The micro-flora of the proximal jejunum in healthy volunteers was compared with the micro-flora in patients with gastrointestinal symptoms suggestive of spontaneous bacterial overgrowth in the small intestine. Biopsies were taken distally to the ligament of Treitz with a Watson capsule. The samples were diluted and inoculated on selective and non-selective agar plates that were incubated aerobically and anaerobically. No major differences were found in the small jejunum micro-flora in healthy persons or in a heterogenous group of patients with gastrointestinal disorders. Oropharyngeal micro-organisms dominated the micro-flora in all subjects and colonic micro-organisms were found in low numbers in a few subjects from both groups. Streptococcus intermedius and Haemophilus parahaemolyticus were only found in the micro-flora of healthy subjects while Lactobacillus spp. was more frequently found in the samples from patients. Eight of 20 healthy subjects and five of 18 patients met the criterion of small intestinal overgrowth. Emerging evidence suggests that other factors are involved in the pathogenesis of the irritable bowel syndrome complex. There is a need for better understanding of the complicated interactions between the host and the endogenous micro-flora.

Implications of the changing face of Clostridium difficile disease for health care practitioners

Recent reported outbreaks of Clostridium difficile-associated disease in Canada have changed the profile of C difficile infections. Historically, C difficile disease was thought of mainly as a nosocomial disease associated with broad-spectrum antibiotics, and the disease was usually not life threatening. The emergence of an epidemic strain, BI/NAP1/027, which produces a binary toxin in addition to the 2 classic C difficile toxins A and B and is resistant to some fluoroquinolones, was associated with large numbers of cases with high rates of mortality. Recently, C difficile has been reported more frequently in nonhospital-based settings, such as community-acquired cases. The C difficile disease is also being reported in populations once considered of low risk (children and young healthy women). In addition, poor response to metronidazole treatment is increasing. Faced with an increasing incidence of C difficile infections and the changing profile of patients who become infected, this paper will reexamine the current concepts on the epidemiology and treatment of C difficile-associated disease, present new hypotheses for risk factors, examine the role of spores in the transmission of C difficile, and provide recommendations that may enhance infection control practices.