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G Corthier

Publications and source records attributed to G Corthier.

At least 37 records · Page 2Linked to original sources
PubMed1996

Prevalence and pathogenicity of Clostridium difficile in hospitalized patients. A French multicenter study.

BACKGROUND: Although Clostridium difficile is the main agent responsible for nosocomial diarrhea in adults, its prevalence in stool cultures sent to hospital microbiology laboratories is not clearly established. OBJECTIVES: To determine the prevalence of C difficile in inpatient stools sent to hospital microbiology laboratories and to assess the relationship between serotypes and toxigenicity of the strains isolated and the clinical data. METHODS: From January 18, 1993, to July 31, 1993, the presence of C difficile was systematically investigated in a case-control study on 3921 stool samples sent for stool culture to 11 French hospital microbiology laboratories. The prevalence of C difficile in this population (cases) was compared with that of a group of 229 random hospital controls matched for age, department, and length of stay (controls). Stool culture from controls was requested by the laboratory although not prescribed by the clinical staff. Serotype and toxigenesis of the strains isolated were compared. RESULTS: The overall prevalence of C difficile in the cases was twice the prevalence in the controls (9.7% vs 4.8%; P < .001) and was approximately 4 times as high in diarrheal stools (ie, soft or liquid) as in normally formed stools from controls (11.5% vs 3.3%; P < .001). The strains isolated from diarrheal stools were more frequently toxigenic than those isolated from normally formed stools. Serogroup D was never toxigenic, and its proportion was statistically greater in the controls than in the cases (45% vs 18%; chi 2 = 5.2; P < .05). Conversely, serogroup C was isolated only from the cases. Clostridium difficile was mainly found in older patients ( > 65 years), suffering from a severe disabling disease, who had been treated with antibiotics and hospitalized for more than 1 week in long-stay wards or in intensive care. CONCLUSIONS: This multicenter period prevalence study clearly supports the hypothesis of a common role of C difficile in infectious diarrhea in hospitalized patients. Disease associated with C difficile should therefore be systematically evaluated in diarrheal stools from inpatients.

Anti-Bacterial Agents↗
PubMed1996

Selective enumeration of Bacteroides vulgatus and B. distasonis organisms in the predominant human fecal flora by using monoclonal antibodies.

The genus Bacteroides represents about one-third of the isolates from human fecal samples. The proportions of the different species are difficult to estimate because there is no method for rapid identification of mixtures of anaerobes. Monoclonal antibodies against Bacteroides vulgatus and B. distasonis were prepared. They did not react with the other Bacteroides species of the B. fragilis group. These reagents allowed direct enumeration of B. vulgatus and B. diastasonis organisms in human fecal samples. Anaerobic bacteria resistant to 1-h contact with air were enumerated in fecal human samples, a filter was layered on the colonies, and then B. vulgatus colonies were identified by an immunoassay performed with the prepared monoclonal antibodies. Healthy human adult volunteers were tested. Most of them harbored B. vulgatus at high levels, while the B. distasonis levels were always lower. Kinetic studies suggested that time variations for each volunteer were small. The simplified quantification of Bacteroides strains at the species level described here will prove useful in complementing our knowledge of the factors which may influence the predominant human fecal flora.

Adult↗
PubMed1996

Imbalance of leucine flux in Lactococcus lactis and its use for the isolation of diacetyl-overproducing strains.

Diacetyl is a by-product of pyruvate metabolism in Lactococcus lactis, where pyruvate is first converted to alpha-acetolactate, which is slowly decarboxylated to diacetyl in the presence of oxygen. L. lactis usually converts alpha-acetolactate to acetoin enzymatically, by alpha-acetolactate decarboxylase encoded by the aldB gene. We took advantage of the fact that this enzyme also has a central role in the regulation of branched-chain amino acids, to select spontaneous aldB mutants in an unbalanced concentration of leucine versus those of valine and isoleucine in the medium. Industrial dairy strains of L. lactis subsp. lactis biovar diacetylactis containing point mutations and deletions of aldB were isolated and characterized. Their growth in milk was not affected, but they rapidly accumulated a large amount of alpha-acetolactate instead of acetoin from citrate in milk. Under aerated condition, strains devoid of AldB produced about 10 times more diacetyl than did the parental strains.

Amino Acid Sequence↗
PubMed1995

Metabolic operons in Lactococci.

The genes for the biosynthesis of histidine, tryptophan and branched-chain amino acids (ilv for isoleucine, leucine and valine) are clustered in large operons. In addition to genes encoding the pathway enzymes, the his and the ilv operons contain 4 and 3 other genes, respectively. The functions of two of these, orf3 and aldB are regulatory. The second gene of the his operon, orf3, encodes a protein homologous to the histidyl-tRNA synthetases. It is involved in transcription attenuation upstream of the his operon. This regulation is related to a new class of attenuation mechanisms controlling the expression of most tRNA synthetase genes and a few metabolic operons in Gram-positive bacteria. Gene aldB, the penultimate gene of the ilv operon, encodes acetolactate decarboxylase. This enzyme transforms acetolactate (AL), the first intermediate of leucine and valine biosynthesis, into acetoin. AL decarboxylase is positively controlled by the availability of leucine and possibly valine in the cell. This is the key enzyme for a new class of regulatory mechanisms, a metabolic shunt which guides the AL flux towards synthesis of amino acids or a secondary metabolite.

Amino Acid Sequence↗
PubMed1994

Kinetics of appearance of intestinal lesions in mice mono-associated with a lethal or non-lethal strain of Clostridium difficile.

The kinetics of the appearance of intestinal lesions induced by orogastric inoculation of gnotobiotic mice with a lethal strain of Clostridium difficile (VPI) that produced toxins A and B in vivo and in vitro was studied and compared with the lesions induced by non-lethal C. difficile strain 786 that produced toxins A and B in vitro but only toxin B in measurable amounts in vivo. Different portions of the intestine were removed 12, 20, 26 and 30 h after inoculation and studied by scanning electronmicroscopy. The remaining portions were homogenised for enumeration of C. difficile and quantification of toxin A by enzyme immunoassay and toxin B by cytotoxicity. The results showed that, following inoculation: (i) measurable amounts of both toxins were necessary to produce lesions; (ii) with strain VPI, the caecum and the colon were rapidly impaired and completely destroyed after 1 day, whereas the small intestine was damaged to a lesser extent; (iii) C. difficile strain 786 did not cause mucosal damage but induced mucus-like or serum-like secretion and morphological changes in the caecal enterocytes only.

Animals↗
PubMed1993

Heterogeneity of Clostridium difficile isolates from infants.

In order to improve our understanding of the role of Clostridium difficile in infants we characterised the strains isolated from this population. The production of toxin A and toxin B was studied. The toxin A, playing a major role in the disease, was searched for in faecal samples. The serogroup of the isolates was determined because some serogroups have been shown to be more pathogenic than others. Over a 9-month period, 102 faecal samples from 102 hospitalised infants (0-12 months) were analysed and 26% of the children were colonised with C. difficile. Fifteen isolates secreted neither toxin A nor B (62.5%). Nine isolates were toxigenic and secreted both toxins (37.5%). Of the eight toxigenic strains tested, six were from serogroup H and two serogroup K. Of the 13 nontoxigenic strains tested, 8 belonged to serogroup D, 2 to serogroup X, and 1 each to serogroup A, serogroup B and serogroup C. Three infants out of 102 studied had toxin A in their faeces. In summary, the infants can be colonised by (1) nontoxigenic strains, most of them from nonpathogenic serogroup D, without toxin A in the faeces; (2) toxigenic strains of virulent serogroups H and K, with or without toxin A in the faeces. Although some infants had diarrhoea, none needed a specific treatment for C. difficile. No specific C. difficile pathology could be retained and different mechanisms are advanced to explain this absence of pathogenicity.

Bacterial Toxins↗
PubMed1993

Production of monoclonal antibodies against Clostridium difficile cytotoxin using immunosorbent binding bioassay procedure.

In the following study, a novel screening approach was used to develop monoclonal antibodies specific for toxin B of Clostridium difficile. The approach, which consisted of an immunosorbent binding bioassay (ISBBA), is based on antigen immunocapture by monoclonal antibodies and detection of biological activity. Our results showed ISBBA, which uses unpurified antigen, to be more sensitive than the neutralization assay and ELISA for the detection of toxin B antibody.

Animals↗
PubMed1993

Saccharomyces boulardii for Clostridium difficile-associated enteropathies in infants.

Based on experimental evidence in animals showing that the oral administration of Saccharomyces boulardii is effective in reducing morbidity and mortality due to Clostridium difficile-induced pseudomembranous colitis, we conducted an open trial to examine the effects of the living yeast, given as primary therapy, in a selected group of infants and children with persistent intestinal symptoms related to toxinogenic C. difficile overgrowth. Over a period of 10 consecutive months, we studied 19 eligible patients (median age 8 months) who presented with enteral symptoms lasting for > 15 days and who had solely C. difficile in stools with positive cytotoxin B assay. Serotyping of the strains and determination in vitro of production of toxins A and B were performed subsequently. The patients presented with persistent or protracted diarrhea, malabsorption, and failure to grow (n = 8), or with repeated attacks of colics, emesis, and hypermeteorism without diarrhea (n = 4), or with both entities (n = 7). Patients with chronic protracted diarrhea (n = 3) had depressed jejunal disaccharidase activities and ultrastructural changes of enterocytes, including sparce and shortened microvilli. None had evidence of colitis. All the strains of C. difficile tested (n = 17) belonged to pathogenic serotypes (A1, A8, C, F, G, H, and K) and produced in vitro high levels of toxins A (n = 16) and B (n = 17). S. boulardii was given orally in a lyophilized form over 15 days (250 mg two to four times per day according to age).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Serogroup F strains of Clostridium difficile produce toxin B but not toxin A.

Most toxigenic strains of Clostridium difficile produce two toxins: an enterotoxin (toxin A) and a cytotoxin (toxin B). Only one strain (strain 8864) has been reported to produce toxin B but no toxin A. Serogroup F strains (44) of C. difficile, often isolated from asymptomatic infants, have been examined for toxin production. These strains, which were from distinct geographical and clinical sources, did not produce any detectable toxin A in vitro when examined in three distinct immunoassays. Nevertheless, all the strain produced a cytotoxin. Immunological differences between the cytotoxin of the serogroup F strains and that produced by C. difficile strain VPI 10463 (serogroup G) were demonstrated with monoclonal antibodies specific for either the toxin B produced by C. difficile strain VPI 10463 or C. sordellii lethal toxin (LT). Polymerase chain reaction amplification with primers derived from C. difficile strain VPI 10463 toxin A and B genes showed that serogroup F strains seem to possess a toxin B gene homologous with that of strain VPI 10463 and at least fragments of the toxin A gene. When axenic mice were inoculated with serogroup F strains, the animals survived; they did not develop diarrhoea and no toxin A could be detected in their faeces. However, cytotoxin was detected. Furthermore, these mice were protected against subsequent challenge with the otherwise lethally toxigenic C. difficile strain VPI 10463. The serogroup F strains appeared to be homogeneous and distinct from other C. difficile strains with regard to toxin production.

Animals↗
PubMed1993

Comparison of enterotoxin production, cytotoxin production, serogrouping, and antimicrobial susceptibilities of Clostridium difficile strains isolated from AIDS and human immunodeficiency virus-negative patients.

We analyzed and compared Clostridium difficile strains isolated from diarrheic stools of 49 human immunodeficiency virus (HIV)-negative and 50 AIDS patients. Our results suggest that distribution patterns of serogroups are different in these two populations. Serogroup C (which has been previously reported to be very resistant to antimicrobial agents) represents 66.0 and 18.4% of the isolates from AIDS and HIV-negative patients, respectively (P < 0.001); the selection of serogroup C could be explained by multiple antibiotic pressure to which AIDS patients have been subjected.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Use of an enzyme-linked immunoassay for Clostridium difficile serogrouping.

An enzyme-linked immunoassay (ELISA) with 11 Clostridium difficile serogroup-specific antisera was applied for serogrouping of C. difficile colonies from 314 consecutive positive fecal samples. Two hundred forty-nine strains (79%) were correctly serogrouped, 57 (18%) belonged to serogroups other than the 11 which were evaluated and gave a negative reaction with all antisera, and 8 isolates (2.5%) did not react with their corresponding antisera. ELISA is a rapid and reliable method for serogrouping C. difficile and should allow for the automation of this procedure.

Animals↗
PubMed1993

Detection of Clostridium difficile toxins in stools. Comparison between a new enzyme immunoassay for toxin A and other routine tests.

An enzyme-linked immunosorbent assay (ELISA) for detection of Clostridium difficile toxin A (enterotoxin) using a monoclonal antibody is described. No cross-reaction was observed with any of the Clostridium species tested except for toxigenic Clostridium difficile. One hundred and eight stool specimens from hospitalized patients harbouring C. difficile in their intestine and 43 samples negative for C. difficile isolation were studied to compare this test with a cytotoxicity assay, the isolation of toxigenic C. difficile and the commercial EIA Premier test (Meridian). As compared with the cytotoxicity assay and EIA, specificity was 91 and 100%, while sensitivity 83 and 74% respectively. This ELISA technique could be used as a routine test for toxin A detection in stools.

Adolescent↗
PubMed1992

Effect of oral Saccharomyces boulardii treatment on the activity of Clostridium difficile toxins in mouse digestive tract.

Human antibiotic-associated diarrhoea and pseudomembranous colitis are partly due to toxin production by Clostridium difficile. It is now well documented that Saccharomyces boulardii protects against C. difficile induced diseases. In an attempt to understand better the mechanism of this protective effect, the action of S. boulardii on a crude toxin preparation was studied in vitro and in vivo. The results showed that the yeast had no effect on the toxins in vitro but was able to protect mice inoculated with these toxins. Furthermore, the observation by scanning electron microscopy that the mucosa of S. boulardii protected mice was not damaged suggest that the yeast mainly acts on the intestinal mucosa.

Administration, Oral↗
PubMed1992

Effects of antibiotics and other drugs on toxin production in Clostridium difficile in vitro and in vivo.

In an attempt to understand more completely why patients treated with phenothiazines (chlorpromazine and cyamemazine), methotrexate, and certain antibiotics such as clindamycin have an increased risk of developing pseudomembranous colitis, the production of toxins A and B by Clostridium difficile in the presence of these drugs was measured in vitro as well as in vivo by using axenic mice. None of the drugs tested increased the production of toxins either in vitro or in vivo.

Animals↗
PubMed1992

Presence of Clostridium difficile and antibiotic and beta-lactamase activities in feces of volunteers treated with oral cefixime, oral cefpodoxime proxetil, or placebo.

Three groups of six healthy adult volunteers were randomly assigned to a treatment with 400 mg of oral cefpodoxime proxetil, oral cefixime, or placebo per day for 10 days. Informed consent was obtained from all volunteers. Clostridium difficile was not detected in the feces of any subject before treatment or at any time in the subjects in the placebo group. C. difficile was, however, detected in all subjects treated with cefpodoxime proxetil and in five of six treated with cefixime. Genomic DNA restriction patterns showed that the strains of C. difficile differed from one volunteer to another. Two subjects both shed different strains at different times during the 25-day surveillance period. All isolates were resistant to cefixime and cefpodoxime (MIC for 90% of strains, 256 and 512 mg/liter, respectively). Antibiotic activity was found in the feces of one volunteer treated with cefpodoxime proxetil and of four volunteers treated with cefixime. It was inversely correlated with the presence of fecal beta-lactamase activity. Intestinal side effects were limited to modifications of stool consistency, which occurred in only 3 of the 12 treated volunteers and did not lead to cessation of treatment. These modifications were significantly associated with the presence of fecal antibiotic activity (P less than 0.05) but not with the shedding of toxigenic or nontoxigenic strains of C. difficile or with the presence of toxin A in feces, which was detected only in one perfectly healthy treated volunteer.

Administration, Oral↗
PubMed1992

Characterization of a toxin A-negative, toxin B-positive strain of Clostridium difficile.

This study was undertaken to examine toxin production by Clostridium difficile 8864, a naturally occurring isolate that has been reported to produce toxin B in the absence of toxin A. To date, this is the only strain of C. difficile reported to produce only one of the toxins. The results of our initial studies with antibodies against toxins A and B confirmed these observations. Toxin B from strain 8864 and from VPI strain 10463, a strain that produces high levels of both toxin A and toxin B, was purified to homogeneity by sequential anion-exchange chromatography on DEAE-Sepharose CL-6B, gel filtration on Ultrogel AcA22, and immunoadsorption chromatography, and their toxic activities were compared. Our results showed that toxin B from strain 8864 and toxin B from C. difficile VPI strain 10463 were comparable in their cytotoxic activities and that the 8864 toxin B was more lethal. In addition, we observed that toxin B from strain 8864 was weakly enterotoxic, which may explain the ability of this strain to cause intestinal disease in hamsters treated with antibiotics. Analysis with specific antibodies showed that the toxin B molecules from these strains were highly related but contained distinct epitopes. The results of hybridization studies with probes specific for the toxin B gene of VPI strain 10463 demonstrated differences between the toxin B genes of the two strains. In addition, probes specific for the toxin A gene of VPI strain 10463 showed that strain 8864 contains a region which shows identity with the 5' end of the toxin A gene but not the region of the gene which encodes a hydrophobic region and the repeating units.

Bacterial Proteins↗
PubMed1991

Protection against experimental pseudomembranous colitis in gnotobiotic mice by use of monoclonal antibodies against Clostridium difficile toxin A.

The pathogenicity of Clostridium difficile is due to the production of two toxins (toxins A and B). We prepared monoclonal antibodies against toxin A and determined whether axenic mice passively immunized with the monoclonal antibodies were protected against C. difficile disease. The mice were kept in an isolator and were given ascites fluid intravenously prior to challenge with a toxinogenic strain of C. difficile. Control mice and mice receiving ascites fluid devoid of toxin antibody died within 2 days and had high levels of toxins A and B in their feces. Mice that received ascites fluid containing high amounts of toxin A monoclonal antibodies directed against the repeating units of the toxin survived. In protected mice, toxin B levels were similar to those in dying mice, but toxin A levels were greatly reduced. These data show that passive immunity induced by monoclonal antibodies against toxin A was effective against pseudomembranous cecitis.

Animals↗