Search PubMed⌕ Search

Biomedical subjects

P Berche

Publications and source records attributed to P Berche.

At least 19 recordsLinked to original sources
PubMed2003

[Phenotypic and genotypic characteristics of non fermenting atypical strains recovered from cystic fibrosis patients].

We used partial 16S rRNA gene (16S DNA) sequencing for the prospective identification of nonfermenting Gram-negative bacilli recovered from patients attending our cystic fibrosis center (hôpital Necker-Enfants malades), which gave problematic results with conventional phenotypic tests. During 1999, we recovered 1093 isolates of nonfermenting Gram-negative bacilli from 702 sputum sampled from 148 patients. Forty-six of these isolates (27 patients) were not identified satisfactorily in routine laboratory tests. These isolates were identified by 16S DNA sequencing as Pseudomonas aeruginosa (19 isolates, 12 patients), Achromobacter xylosoxidans (10 isolates, 8 patients), Stenotrophomonas maltophilia (9 isolates, 9 patients), Burkholderia cepacia genomovar I/III (3 isolates, 3 patients), Burkholderia vietnamiensis (1 isolate), Burkholderia gladioli (1 isolate) and Ralstonia mannitolilytica (3 isolates, 2 patients). Fifteen isolates (33%) were resistant to all antibiotics in routine testing. Sixteen isolates (39%) resistant to colistin were recovered on B. cepacia-selective medium: 2 P. aeruginosa, 3 A. xylosoxidans, 3 S. maltophilia and the 8 Burkholderia--Ralstonia isolates. The API 20NE system gave no identification for 35 isolates and misidentified 11 isolates (2 P. aeruginosa, 2 A. xylosoxidans and 1 S. maltophilia classified as B. cepacia ). Control measures and/or treatment were clearly improved as a result of 16S DNA sequencing in three of these cases. This study confirms the weakness of phenotypic methods for identification of atypical nonfermenting Gram-negative bacilli recovered from cystic fibrosis patients. The genotypic methods, such as 16S DNA sequencing which allows identification of strains in routine practice, appears to have a small, but significant impact on the clinical management of CF patients.

Achromobacter↗
PubMed2003

[Bacterial aggression].

In all living species, the first line of defence against microbial aggressions is constituted by innate immunity. During Evolution, it appears in invertebrates and plants, long before adaptive immunity, which appears in vertebrate. Adaptive immunity induces acquired resistance against microorganisms through random somatic rearrangements of genes encoding immunoglobulins and T cell receptors, thus generating a high level of diversity of receptors (>10(9)) in response to microbial aggressions. Acquired resistance is not vertically transmitted and reflects the "infectious history" of every individual. In contrast, innate immunity relies on recognition of antigens by a small number of weakly specific receptors (>10(2)) designated Pattern-Recognition Receptors (PRR) and is vertically transmitted by germinal cells. The PRR are expressed on macrophages dendritic cells and B lymphocytes and recognize antigenic structures highly conserved in the living world, termed Pathogen-Associated Molecular Patterns (PAMP), as lipopolysaccharides peptidoglycanes and lipoteichoic acids. PRR are secreted (complement, lectins), or expressed at the cell surface of cells to induce endocytosis or signaling (Toll-like receptors or TLRs). The recognition of antigens induces an immediate inflammatory response and triggers adaptive immunity. Among secreted PRR, the system of complement plays a major role in the immediate inflammatory response, controlling infections by its major role in opsonization, chemotactism and activation of leucocytes. TLRs induce the inflammatory response against microorganisms through NF-kB, a cytoplasmic factor controlling transcription of many genes, including cytokines (TNF, INF, IL-1, IL-2, IL-8, IL-12.) and defensines. So, within few minutes following microbial aggression, the inflammatory response is rapidly triggered to destroy infectious agents and to generate a long-term memory against pathogens.

Animals↗
PubMed2001

Comparative genomics of Listeria species.

Listeria monocytogenes is a food-borne pathogen with a high mortality rate that has also emerged as a paradigm for intracellular parasitism. We present and compare the genome sequences of L. monocytogenes (2,944,528 base pairs) and a nonpathogenic species, L. innocua (3,011,209 base pairs). We found a large number of predicted genes encoding surface and secreted proteins, transporters, and transcriptional regulators, consistent with the ability of both species to adapt to diverse environments. The presence of 270 L. monocytogenes and 149 L. innocua strain-specific genes (clustered in 100 and 63 islets, respectively) suggests that virulence in Listeria results from multiple gene acquisition and deletion events.

Adaptation, Physiological↗
PubMed2001

Conventional alpha beta T cells are sufficient for innate and adaptive immunity against enteric Listeria monocytogenes.

We have begun to dissect the cellular requirements for generation of immunity against enteric infection by Listeria monocytogenes using a novel T(-) B(-) NK(-) mouse strain (mice double deficient for the common cytokine receptor gamma-chain (gamma(c)) and the recombinase-activating gene-2 (RAG2/gamma(c) mice). Initial experiments showed that C57BL/6 mice and alymphoid RAG2/gamma(c) mice had similar kinetics of bacterial accumulation in the spleen, liver, and brain early after intragastric L. monocytogenes infection (up to day 3), calling into question the physiologic role of gut-associated lymphoid cells during the passage of this enterobacterium into the host. However, in contrast to C57BL/6 mice, RAG2/gamma(c) mice rapidly succumbed to disseminated infection by day 7. Polyclonal lymph node CD4(+) and CD8(+) alphabeta T cells were able to confer RAG2/gamma(c) mice with long-lasting protection against enteric L. monocytogenes infection in the absence of gammadelta T, NK, and NK-T cells. Moreover, these alphabeta T-reconstituted RAG2/gamma(c) mice produced IFN-gamma at levels comparable to C57BL/6 mice in response to L. monocytogenes both in vitro and in vivo. Protection was IFN-gamma dependent, as RAG2/gamma(c) mice reconstituted with IFN-gamma-deficient alphabeta T cells were unable to control enteric L. monocytogenes infection. Furthermore, alphabeta T cell-reconstituted RAG2/gamma(c) mice were able to mount memory responses when challenged with lethal doses of L. monocytogenes. These data suggest that NK, NK-T, gammadelta T, and B cells are functionally redundant in the immunity against oral L. monocytogenes infection, and that in their absence alphabeta T cells are able to mediate the early IFN-gamma production required for both innate and adaptive immunity.

Animals↗
PubMed2001

[Contribution of the laboratory to the epidemiologic study of bacterial infections].

The laboratory plays a significant role in the epidemiologic investigations by the comparative analysis of the bacterial strains involved in the outbreaks. Recently, the use of molecular analysis methods provided better performance than traditional phenotypic methods which are still used as preliminary tests because of their relatively low cost and technical simplicity. These analyses deal with either the whole chromosome of the bacterium, plasmids or particular genes. The classification of these methods runs up against the lack of consensus concerning their nomenclature. A clearer denomination based upon the technique responsible for revealing the polymorphisms of these various targets, makes it possible to divide these methods in two principal groups: methods of RFLP (based on the fragments resulting from digestion with restriction enzymes) and methods of AFLP (based on the products of amplification by PCR). The knowledge of the typability of the strains and the qualities of these various methods, particularly their discriminatory power, is essential to the accuracy of the laboratory analysis in the investigations of outbreaks.

Bacteria↗
PubMed2001

The threat of smallpox and bioterrorism.

Smallpox (variola) was a devastating disease with a high case-fatality rate. Although the disease was eradicated in 1977, the remaining stocks of smallpox virus constitute one of the most dangerous threats to humanity. The smallpox virus is highly specific for humans and non-pathogenic in animals. There is no antiviral treatment and a vaccine is active only if administered in the first four days post-exposure. Smallpox virus represents a potential biological weapon that could be used by terrorists, and the destruction of stocks raises political, social, scientific and ethical issues.

Biological Warfare↗
PubMed2001

Dendritic cells are early cellular targets of Listeria monocytogenes after intestinal delivery and are involved in bacterial spread in the host.

We studied the sequence of cellular events leading to the dissemination of Listeria monocytogenes from the gut to draining mesenteric lymph nodes (MLNs) by confocal microscopy of immunostained tissue sections from a rat ligated ileal loop system. OX-62-positive cells beneath the epithelial lining of Peyer's patches (PPs) were the first Listeria targets identified after intestinal inoculation. These cells had other features typical of dendritic cells (DCs): they were large, pleiomorphic and major histocompatibility complex class II(hi). Listeria were detected by microscopy in draining MLNs as early as 6 h after inoculation. Some 80-90% of bacteria were located in the deep paracortical regions, and 100% of the bacteria were present in OX-62-positive cells. Most infected cells contained more than five bacteria each, suggesting that they had arrived already loaded with bacteria. At later stages, the bacteria in these areas were mostly present in ED1-positive mononuclear phagocytes. These cells were also infected by an actA mutant defective in cell-to-cell spreading. This suggests that Listeria are transported by DCs from PPs to the deep paracortical regions of draining MLNs and are then transmitted to other cell populations by mechanisms independent of ActA. Another pathway of dissemination to MLNs was identified, probably involving free Listeria and leading to the infection of ED3-positive mononuclear phagocytes in the subcapsular sinus and adjacent paracortical areas. This study provides evidence that DCs are major cellular targets of L. monocytogenes in PPs and that DCs may be involved in the early dissemination of this pathogen. DCs were not sites of active bacterial replication, making these cells ideal vectors of infection.

Animals↗
PubMed2001

Microbiology of otitis media in the Paris, France, area from 1987 to 1997.

PURPOSE OF THE STUDY: To investigate epidemiologic trends in the bacteriology of acute otitis media, data were recorded during a 10-year period by the same group of investigators during clinical studies in pediatric outpatients. METHODS: Bacterial samples were obtained before antibiotic treatment from 2149 children (age 3 to 36 months) with acute otitis media. All samples were transported, handled and cultured in the same way throughout the 10-year period. RESULTS: From the study patients 1862 samples of middle ear secretion were collected by tympanocentesis and 287 samples were collected from spontaneous otorrhea occurring within 24 h. Pathogens were isolated from 70% of patients. Pathogens included Haemophilus influenzae (40%), Streptococcus pneumoniae (31%) and Moraxella catarrhalis (8%). The incidence of beta-lactamase-producing H. influenzae was approximately 20% from 1987 to 1989, was approximately 35% from 1990 to 1995 and increased to 60 and 70% during the last 2 years. The rate of S. pneumoniae with decreased susceptibility to penicillin gradually increased from 7% in 1987 to 70% in 1996 and 1997. CONCLUSION: The very high incidence of antimicrobial resistant strains reached during a short period in pediatric acute otitis media in our area, emphasizes the need for frequent epidemiologic studies.

Drug Resistance, Microbial↗
PubMed2001

Nasopharyngeal colonization by Haemophilus influenzae in children living in an orphanage.

AIM: To study colonization and transmission of Haemophilus influenzae in a cohort of children <2 years old living in the unique epidemiologic conditions of a closed community of an orphanage. METHODS: Fifty-three children, ages 0 to 24 months, were followed for 1 year. All children >2 months were vaccinated against H. influenzae serotype b. Nasopharyngeal cultures were collected monthly or, in children <6 months of age, every 2 weeks. Antibiotic susceptibility, serotype, biotype and genotype (pulsed field gel electrophoresis) of each isolate were determined. As control, 39 H. influenzae isolates were recovered from various regions in France. RESULTS: The mean monthly rate of carriage was 45% ranging from 17 to 70%. Most isolates belonged to biotype II (62%), 4 isolates to serotype f (3.6%) and none to serotype b, and 60% of the 111 isolates produced beta-lactamase. A complete concordance was found among biotype, serotype, pulsotype and antimicrobial susceptibility. On average children were sequentially colonized by 3 different isolates. The mean duration of carriage for a given isolate was approximately 1.4 months. In younger children the mean age of primary colonization was 2 months. Contrasting with the high genetic heterogeneity of 39 control isolates, most isolates (82%) belonged to only 5 pulsotypes. Three main H. influenzae clones rapidly spread in the community and colonized children in waves. CONCLUSION: During early life nasopharyngeal colonization by H. influenzae is a dynamic phenomenon with sequential carriage of various clones spreading in the community.

Carrier State↗
PubMed2001

SvpA, a novel surface virulence-associated protein required for intracellular survival of Listeria monocytogenes.

A previously unknown protein, designated SvpA (surface virulence-associated protein) and implicated in the virulence of the intracellular pathogen Listeria monocytogenes, was identified. This 64 kDa protein, encoded by svpA, is both secreted in culture supernatants and surface-exposed, as shown by immunogold labelling of whole bacteria with an anti-SvpA antibody. Analysis of the peptide sequence revealed that SvpA contains a leader peptide, a predicted C-terminal transmembrane region and a positively charged tail resembling that of the surface protein ActA, suggesting that SvpA might partially reassociate with the bacterial surface by its C-terminal membrane anchor. An allelic mutant was constructed by disrupting svpA in the wild-type strain LO28. The virulence of this mutant was strongly attenuated in the mouse, with a 2 log decrease in the LD50 and restricted bacterial growth in organs as compared to the wild-type strain. This reduced virulence was not related either to a loss of adherence or to a lower expression of known virulence factors, which remained unaffected in the svpA mutant. It was caused by a restriction of intracellular growth of mutant bacteria. By following the intracellular behaviour of bacteria within bone-marrow-derived macrophages by confocal and electron microscopy studies, it was found that most svpA mutant bacteria remained confined within phagosomes, in contrast to wild-type bacteria which rapidly escaped to the cytoplasm. The regulation of svpA was independent of PrfA, the transcriptional activator of virulence genes in L. monocytogenes. In fact, SvpA was down-regulated by MecA, ClpC and ClpP, which are highly homologous to proteins of Bacillus subtilis forming a regulatory complex controlling the competence state of this saprophyte. The results indicate that: (i) SvpA is a novel factor involved in the virulence of L. monocytogenes, promoting bacterial escape from phagosomes of macrophages; (ii) SvpA is, at least partially, associated with the surface of bacteria; and (iii) SvpA is PrfA-independent and controlled by a MecA-dependent regulatory network.

Amino Acid Sequence↗
PubMed2001

The autolysin Ami contributes to the adhesion of Listeria monocytogenes to eukaryotic cells via its cell wall anchor.

Adherence of pathogenic microorganisms to the cell surface is a key event during infection. We have previously reported the characterization of Listeria monocytogenes transposon mutants defective in adhesion to eukaryotic cells. One of these mutants had lost the ability to produce Ami, a 102 kDa autolytic amidase with an N-terminal catalytic domain and a C-terminal cell wall-anchoring domain made up of repeated modules containing the dipeptide GW ('GW modules'). We generated ami null mutations by plasmid insertion into L. monocytogenes strains lacking the invasion proteins InlA (EGDDeltainlA), InlB (EGDDeltainlB) or both (EGDDeltainlAB). These mutants were 5-10 times less adherent than their parental strains in various cell types. The adhesion capacity of the mutants was restored by complementation with a DNA fragment encoding the Ami cell wall-anchoring domain fused to the Ami signal peptide. The cell-binding activity of the Ami cell wall-anchoring domain was further demonstrated using the purified polypeptide. Growth of the ami null mutants constructed in EGD and EGDDeltainlAB backgrounds was attenuated in the livers of mice inoculated intravenously, indicating a role for Ami in L. monocytogenes virulence. Adhesive properties have recently been reported in the non-catalytic domain of two other autolysins, Staphylococcus epidermidis AtlE and Staphylococcus saprophyticus Aas. Interestingly, we found that these domains were also composed of repeated GW modules. Thus, certain autolysins appear to promote bacterial attachment by means of their GW repeat domains. These molecules may contribute to the colonization of host tissues by Gram-positive bacteria.

Amino Acid Sequence↗
PubMed2001

Identification of a PEST-like motif in listeriolysin O required for phagosomal escape and for virulence in Listeria monocytogenes.

The hly-encoded listeriolysin O (LLO) is a major virulence factor secreted by the intracellular pathogen Listeria monocytogenes, which plays a crucial role in the escape of bacteria from the phagosomal compartment. Here, we identify a putative PEST sequence close to the N-terminus of LLO and focus on the role of this motif in the biological activities of LLO. Two LLO variants were constructed: a deletion mutant protein, lacking the 19 residues comprising this sequence (residues 32-50), and a recombinant protein of wild-type size, in which all the P, E, S or T residues within this motif have been substituted. The two mutant proteins were fully haemolytic and were secreted in culture supernatants of L. monocytogenes in quantities comparable with that of the wild-type protein. Strikingly, both mutants failed to restore virulence to a hly-negative strain in vivo. In vitro assays showed that L. monocytogenes expressing the LLO deletion mutant was strongly impaired in its ability to escape from the phagosomal vacuole and, subsequently, to divide in the cytosol of infected cells. This work reveals for the first time that the N-terminal portion of LLO plays an important role in the development of the infectious process of L. monocytogenes.

Amino Acid Motifs↗
PubMed2001

Sputum itraconazole concentrations in cystic fibrosis patients.

Itraconazole diffusion in sputum was studied in 11 cystic fibrosis patients with allergic bronchopulmonary aspergillosis. There was a high interindividual variability in sputum itraconazole concentration and sputum/serum drug concentration ratio. Three children had sputum drug concentrations before oral administration that were lower than the itraconazole MIC at which 90% of Aspergillus fumigatus strains were inhibited, although their serum drug concentrations were within the therapeutic range.

Adolescent↗
PubMed2001

Listeria pathogenesis and molecular virulence determinants.

The gram-positive bacterium Listeria monocytogenes is the causative agent of listeriosis, a highly fatal opportunistic foodborne infection. Pregnant women, neonates, the elderly, and debilitated or immunocompromised patients in general are predominantly affected, although the disease can also develop in normal individuals. Clinical manifestations of invasive listeriosis are usually severe and include abortion, sepsis, and meningoencephalitis. Listeriosis can also manifest as a febrile gastroenteritis syndrome. In addition to humans, L. monocytogenes affects many vertebrate species, including birds. Listeria ivanovii, a second pathogenic species of the genus, is specific for ruminants. Our current view of the pathophysiology of listeriosis derives largely from studies with the mouse infection model. Pathogenic listeriae enter the host primarily through the intestine. The liver is thought to be their first target organ after intestinal translocation. In the liver, listeriae actively multiply until the infection is controlled by a cell-mediated immune response. This initial, subclinical step of listeriosis is thought to be common due to the frequent presence of pathogenic L. monocytogenes in food. In normal individuals, the continual exposure to listerial antigens probably contributes to the maintenance of anti-Listeria memory T cells. However, in debilitated and immunocompromised patients, the unrestricted proliferation of listeriae in the liver may result in prolonged low-level bacteremia, leading to invasion of the preferred secondary target organs (the brain and the gravid uterus) and to overt clinical disease. L. monocytogenes and L. ivanovii are facultative intracellular parasites able to survive in macrophages and to invade a variety of normally nonphagocytic cells, such as epithelial cells, hepatocytes, and endothelial cells. In all these cell types, pathogenic listeriae go through an intracellular life cycle involving early escape from the phagocytic vacuole, rapid intracytoplasmic multiplication, bacterially induced actin-based motility, and direct spread to neighboring cells, in which they reinitiate the cycle. In this way, listeriae disseminate in host tissues sheltered from the humoral arm of the immune system. Over the last 15 years, a number of virulence factors involved in key steps of this intracellular life cycle have been identified. This review describes in detail the molecular determinants of Listeria virulence and their mechanism of action and summarizes the current knowledge on the pathophysiology of listeriosis and the cell biology and host cell responses to Listeria infection. This article provides an updated perspective of the development of our understanding of Listeria pathogenesis from the first molecular genetic analyses of virulence mechanisms reported in 1985 until the start of the genomic era of Listeria research.

Animals↗
PubMed2001

Identification of new genes involved in the virulence of Listeria monocytogenes by signature-tagged transposon mutagenesis.

Listeria monocytogenes is a gram-positive, facultative intracellular pathogen that can cause severe food-born infections in humans and animals. We have adapted signature-tagged transposon mutagenesis to L. monocytogenes to identify new genes involved in virulence in the murine model of infection. We used transposon Tn1545 carried on the integrative vector pAT113. Forty-eight tagged transposons were constructed and used to generate banks of L. monocytogenes mutants. Pools of 48 mutants were assembled, taking one mutant from each bank, injected into mice, and screened for those affected in their multiplication in the brains of infected animals. From 2,000 mutants tested, 18 were attenuated in vivo. The insertions harbored by these mutants led to the identification of 10 distinct loci, 7 of which corresponded to previously unknown genes. The properties of four loci involving putative cell wall components were further studied in vitro and in vivo. The data suggested that these components are involved in bacterial invasion and multiplication in the brain.

Amino Acid Sequence↗
PubMed2001

Stress-induced ClpP serine protease of Listeria monocytogenes is essential for induction of listeriolysin O-dependent protective immunity.

The stress-induced protease ClpP is required for virulence of the facultative intracellular pathogen Listeria monocytogenes. We previously found that in the absence of ClpP, the virulence of this pathogen was strongly reduced, mainly due to the decreased production of functional listeriolysin O (LLO), a major immunodominant virulence factor promoting intracellular growth. In this work, a clpP deletion mutant of L. monocytogenes was used to study the generation of anti-Listeria protective immunity. We found that ClpP is required for the intracellular growth of L. monocytogenes in resident macrophages in vivo. Mice infected with doses as high as 10(6) clpP mutant bacteria were not protected against a lethal challenge of wild-type bacteria and did not develop any detectable LLO-specific cytolytic T cells or antibodies, suggesting that the amount of LLO produced in infected mice under these conditions was too low to induce a specific immune response. However, in contrast to the results obtained with a mutant with a disrupted hly gene, this lack of protection was overcome by inoculation of very high infecting doses of clpP mutant bacteria (5 x 10(8)), thus producing sufficient amounts of LLO to stimulate anti-Listeria immunity. The role of ClpP was confirmed by showing that anti-Listeria immunity was restored in mice infected with a clpP-complemented mutant. These results indicate that the stress-induced serine protease ClpP is a potential target for modulating the presentation of protective antigens such as LLO and thereby the immune response against L. monocytogenes.

Adenosine Triphosphatases↗