Biomedical subjects

Patrick Berche

Publications and source records attributed to Patrick Berche.

42 records · Page 3Linked to original sources

PubMed2002

Use of 16S rRNA gene sequencing for identification of nonfermenting gram-negative bacilli recovered from patients attending a single cystic fibrosis center.

During 1999, we used partial 16S rRNA gene sequencing for the prospective identification of atypical nonfermenting gram-negative bacilli isolated from patients attending our cystic fibrosis center. Of 1,093 isolates of nonfermenting gram-negative bacilli recovered from 148 patients, 46 (4.2%) gave problematic results with conventional phenotypic tests. These 46 isolates were genotypically identified 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), a recently recognized species.

Alcaligenes↗

PubMed2001

Alterations to penicillin-binding proteins 1A, 2B and 2X amongst penicillin-resistant clinical isolates of Streptococcus pneumoniae serotype 23F from the nasopharyngeal flora of children.

Various amino acid substitutions were identified in the three major penicillin-binding proteins (PBP1A, PBP2B and PBP2X) of eight clinical isolates of Streptococcus pneumoniae serotype 23F collected from children. The particular changes related to the level of penicillin resistance. Alterations were detected in an isolate with a penicillin MIC as low as 0.06 mg/L. These results confirm that the level of penicillin resistance in pneumococci reflects with sequential alterations of PBPs in clinical isolates.

Amino Acid Sequence↗

PubMed2001

Functional assembly of two membrane-binding domains in listeriolysin O, the cytolysin of Listeria monocytogenes.

Listeriolysin O (LLO) is a major virulence factor secreted by the pathogenic Listeria monocytogenes and acts as pore-forming cytolysin. Based on sequence similarities between LLO and perfringolysin (PFO), the cytolysin from Clostridium perfringens of known crystallographic structure, two truncated LLO proteins were produced: LLO-d123, comprising the first three predicted domains, and LLO-d4, the last C-terminal domain. The two proteins were efficiently secreted into the culture supernatant of L. monocytogenes and were able to bind to cell membranes. Strikingly, when expressed simultaneously, the two secreted domains LLO-d123 and LLO-d4 reassembled into a haemolytically active form. Two in-frame linker insertions were generated in the hinge region between the d123 and d4 domains. In both cases, the insertion created a major cleavage site for proteolytic degradation and abolished cytolytic activity, which might suggest that the region connecting d123 and d4 participates in the interaction between the two portions of the monomer.

Animals↗

PubMed2000

Identification of new loci involved in adhesion of Listeria monocytogenes to eukaryotic cells. European Listeria Genome Consortium.

Insertional mutagenesis was performed with Tn1545 in the genetic background of an inIAB deletion mutant to identify new adhesion determinants in Listeria monocytogenes. Four insertion mutants defective in adhesion to eukaryotic cells were identified. Insertion sites were cloned by inverse-PCR and sequenced. The genetic organization of insertion regions was further analysed by screening and sequencing DNA fragments from a HindIII library and by searching databases. Three adhesion-defective mutants each had one copy of Tn1545 inserted into their chromosome. The insertion sites were different in the three mutants: (i) upstream from two ORFs in tandem, similar to dfp and priA of Bacillus subtilis, respectively; (ii) within an ORF encoding a putative 126 amino-acid-polypeptide with no significant similarity to any known protein; (iii) within an ORF similar to a B. subtilis ORF with no known function, just upstream from an operon similar to an ABC (ATP-binding cassette) transporter operon from B. subtilis. The excisants obtained from these mutants using the excision reporter plasmid pTCR9 recovered full adhesion capacity. A fourth mutant was the most severely defective in adhesion. It had five Tn1545 insertions, one of which was upstream from dfp and priA, and another of which was upstream from ami, a gene encoding a surface-exposed autolysin with a C terminus similar to that of InIB. Ami was clearly involved because an ami null mutant constructed in an EGDdeltainIA-F background was adhesion-defective. Thus new regions involved in the adhesion of L. monocytogenes to eukaryotic cells were identified. Further study is required to define more accurately the roles of these regions in the adhesion process itself.

Bacterial Adhesion↗

PubMed1997

Acute childhood otitis media: the diagnostic value of bacterial samples from the nasopharynx.

OBJECTIVE: To compare bacteriologic results in acute otitis media (AOM) from middle ear otorrhea and rhinopharyngeal samples. METHODS: Three hundred and fifty-four children suffering from AOM were included. Two samples were obtained for each patient, one in the middle ear fluid, and another in the rhinopharynx. RESULTS: The rhinopharyngeal sample shows a poor predictive value for the pathogen responsible for the AOM (only 30%). But antibiotic sensitivity from each bacteriologic sample (otorrhea and rhinopharynx) for the whole population showed a very good correlation. CONCLUSIONS: The collection of nasopharyngeal cultures should therefore be promoted for their collective epidemiologic value, especially with reference to the monitoring of pneumococcal susceptibility in children.

Journal Article↗

PubMed1996

The inlA gene required for cell invasion is conserved and specific to Listeria monocytogenes.

The Gram-positive bacterium Listeria monocytogenes can actively induce its own uptake by epithelial cells and fibroblasts through a surface-exposed 80 kDa protein, internalin (InIA), encoded by inIA. We studied the distribution and the DNA polymorphism of inIA sequences in a wide variety of wild strains of L. monocytogenes as compared to other Listeria species. This was done by PCR-amplifying inIA sequences encoding the fifteen repeats A and the three repeats B of InIA. inIA-repeated sequences were only found in L. monocytogenes. The amplified fragment of inIA encoding the repeats A displayed an AIuI DNA polymorphism which arises from point mutations. These results indicate that inIA required for cell invasion is specific to L. monocytogenes and that the intragenic repeats only exhibit a genetic heterogeneity due to point mutations and not to recombinations.

Bacterial Proteins↗