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Biomedical subjects

M F Prère

Publications and source records attributed to M F Prère.

At least 19 recordsLinked to original sources
PubMed2006

Genotype MRSA, a new genetic test for the rapid identification of staphylococci and detection of mecA gene.

Early detection of Staphylococcus methicillin resistance (MR) is essential. However MR determination may be difficult because it is necessary to perform investigation of heterogeneous resistance and low level of resistance and to discriminate between oxacillin resistance and borderline resistance. Several phenotypic methods are recommended but they fail to detect low level of production de PBP2a, the modified Penicillin Binding Protein responsible for MR. Detection of mecA gene, the gene encoding PBP2a, using PCR is considered to be the reference method. We evaluated Genotype MRSA, a new rapid system based on DNA multiplex amplification and further hybridisation, for the identification of staphylococci and detection of the mecA gene. The study was performed on a collection of various Staphylococcus strains (N=30) from clinical human isolates including S. aureus MR and methicillin susceptible (MS), S. epidermidis MR and MS, and other species of coagulase negative Staphylococcus (CNS) MR and MS. For all the strains, the hybridization banding pattern obtained using Genotype MRSA correlated with their expected phenotypic and genotypic characteristics. Genotype MRSA allows the identification of the mecA gene as well as S. aureus and S. epidermidis specific genes. This DNA strip technology based assay can easily be incorporated into routine diagnostics. In addition, the short testing time (less than 2 hours) optimises treatment orientation. Genotype MRSA completely complies with all requirements for a fast, safe, valid and cost-effective MR diagnosis in staphylococci.

Bacterial Proteins↗
PubMed2006

Bacterial aetiology of diarrhoea in young children: high prevalence of enteropathogenic Escherichia coli (EPEC) not belonging to the classical EPEC serogroups.

Diarrhoeal disease continues to be one of the most common causes of admittance in Children hospital emergency. The aim of the present study was to investigate the relative contribution of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively) as a cause of infectious bacterial diarrhoea in children from the region of Toulouse. We analysed 280 samples of stools from 280 children (<2 years) with diarrhoea admitted in the "Hopital des Enfants" from January to August 2005. Classic pathogens (Salmonella, Campylobacter, Yersinia, Shigella, Aeromonas and Vibrio) were detected by standard culture methods. Enterotoxigenic Clostridium difficile were identified after culture by immuno-enzyme assay (IEA). Virulence genes of EPEC and EHEC were detected by using PCR. Shiga-toxin production of EHEC strains was confirmed with an IEA test. Potential enteric pathogens were identified in 55 patients. EPEC was the most frequently identified agent (30 patients), followed by Campylobacter (9 cases: 7 C. jejuni and 2 C. coli) and C. difficile (8 patients), then EHEC (5 patients) and Salmonella (3 patients). No Shigella, Yersinia, Aeromonas or other pathogenic bacteria were detected during this period in that class of children. EPEC not belonging to the classical EPEC serogroups were highly prevalent (24 versus 6). EHEC possessed different genotypes and serogroups: O26 (2 strains), O157 (2 strains) and one un-typable strain. This study demonstrates the importance of EPEC (55 % of positive cases) and of EHEC (more frequent than Salmonella) in the aetiology of diarrhoeal diseases of young children. We confirm the usefulness of the PCR methodology: it allows the detection of virulent E. coli and thus increases by two fold the diagnosis of bacterial diarrhoea.

Diarrhea, Infantile↗
PubMed2001

RECODE: a database of frameshifting, bypassing and codon redefinition utilized for gene expression.

The RECODE database is a compilation of 'programmed' translational recoding events taken from the scientific literature and personal communications. The database deals with programmed ribosomal frameshifting, codon redefinition and translational bypass occurring in a variety of organisms. The entries for each event include the sequences of the corresponding genes, their encoded proteins for both the normal and alternate decoding, the types of the recoding events involved, trans-factors and cis-elements that influence recoding. The database is freely available at http://recode.genetics. utah.edu/.

Base Sequence↗
PubMed2001

The puzzle of zmpB and extensive chain formation, autolysis defect and non-translocation of choline-binding proteins in Streptococcus pneumoniae.

Choline-binding proteins (CBPs) from Streptococcus pneumoniae are involved in several important processes. Inactivation of zmpB, a gene that encodes a surface-located putative zinc metalloprotease, in a S. pneumoniae serotype 4 strain was recently reported to reveal a composite phenotype, including extensive chain formation, lysis defect and transformation deficiency. This phenotype was associated with the lack of surface expression of several CBPs, including the major autolysin LytA. LytA, normally 36 kDa in size, was reported to form an SDS-resistant 80 kDa complex with CinA. ZmpB was therefore proposed to control translocation of CBPs to the surface, possibly through the proteolytic release of CBPs (and RecA) from CinA. Based on the use of 12 independent mariner insertions in the zmpB gene of the well-characterized R6 laboratory strain, we could not confirm several of these observations. Our zmpB mutants: (i) did not form chains; (ii) lysed normally in the presence of deoxycholate, which indicates the presence of a functional autolysin; (iii) transformed at normal frequency; and (iv) contained bona fide CinA and LytA species. Polymorphism of ZmpB between R6 and the serotype 4 isolate could not account for the discrepancy, as inactivation of zmpB (through replacement by transposon-inactivated zmpB R6 alleles) in the latter strain did not affect separation of daughter cells and autolysis. The conflicting observations could be explained by our finding that the reportedly serotype 4 zmpB 'mutant' differed from its S. pneumoniae parent in lacking capsule and in exhibiting characteristic traits of the Streptococcus viridans group, including resistance to optochin.

Amino Acid Sequence↗
PubMed1999

A three-way junction and constituent stem-loops as the stimulator for programmed -1 frameshifting in bacterial insertion sequence IS911.

Several signals are required for the programmed frameshifting in translation of IS911 mRNA. These include a Shine Dalgarno (SD)-like sequence, a slippery sequence of six adenine residues and a guanine residue (A6G) and a 3' secondary structure. The structure of the mRNA containing these elements was investigated using chemical and enzymatic probing. The probing data show that the 3' structure is a three-way junction of stems. The function of the three-way junction was investigated by mutagenesis. Disrupting the stability of the structure greatly affects frameshifting and transposition levels as tested by separate in vivo assays. Structural probing and thermal melting profiles indicate that the disrupted three-way junctions have altered structures.

Aldehydes↗
PubMed1998

[Chronic meningococcemia: 3 cases in the immunocompetent child].

UNLABELLED: Chronic meningococcemia is a part of extra meningeal manifestations of meningococcal disease. Its diagnosis can be difficult because of lack of sensitivity of blood cultures. CASE REPORT: Three cases, concerning immunocompetent children, respectively aged of 14, 10 and 4 years are reported. The clinical course was characterized by recurrent fever, inflammatory joint manifestations and diffuse maculopapules secondary centered by petechiae. Microbiological findings revealed in one case a positive throat culture and presence of meningococcal soluble antigens in blood and urine. In the other two cases, diagnosis was done after done after positive blood culture at the 7th, and 13th days of course. CONCLUSION: The diagnosis should be considered in any children with a prolonged, recurrent fever and cutaneous and joint manifestations even if blood cultures remain negative. The response to therapy by usual antimeningococcal antibiotics is dramatic and curative while a prolonged untreated course may be complicated by metastatic infection.

Adolescent↗
PubMed1994

One-ended insertion of IS911.

An apparently nonreplicative integration reaction mediated by the insertion sequence IS911 has been analyzed. It is shown to involve the right-end inverted repeat (IRR) of the element and sequences in the flanking vector DNA. The flanking sequences appear to behave as a surrogate IS911 end, since integration is greatly reduced when limited similarities with IRR are eliminated by site-directed mutagenesis. Data are presented which suggest that the activity of the IRR junction results from the proximity of the transposase gene and may therefore reflect preferential transposase recognition of IRR in cis.

Bacteriophage lambda↗
PubMed1992

Transposase-induced excision and circularization of the bacterial insertion sequence IS911.

We have investigated the role of three IS911-specified proteins in transposition in vivo: the products of the upstream (OrfA) and downstream (OrfB) open reading frames, and a transframe protein (OrfAB) produced by -1 translational frameshifting between orfA and orfB. The production of OrfAB alone is shown to lead both to excision and to circularization of the element and to be sufficient for intermolecular transposition into a plasmid target. Simultaneous and independent production of OrfA is shown to stimulate OrfAB-mediated intermolecular transposition while greatly reducing the appearance of transposon circles. We have not been able to detect a role for OrfB. Although under certain conditions, the vector plasmid undergoes precise resealing after IS911 excision, the data suggest that this is not normally the case and that the donor plasmid is not generally conserved. The use of IS911 derivatives carrying mutations in the terminal 2 bp suggested that circle formation represents a site-specific intramolecular transposition event. We present a model which explains both intra- and intermolecular transposition events in terms of a single reaction mechanism of the 'cut and paste' type.

Bacteria↗
PubMed1991

Programmed translational frameshifting and initiation at an AUU codon in gene expression of bacterial insertion sequence IS911.

The proteins expressed by insertion sequence IS911, a member of the widespread IS3 family of elements, have been analyzed. The results indicate that three major species are produced from two consecutive reading frames. A protein of Mr 11,500, ORFA, is synthesized from an upstream reading frame. A larger protein, ORFAB, uses the same initiation codon and is produced by a -1 programmed translational frameshift between orfA and a downstream frame, orfB, whose amino acid sequence shows significant homology with retroviral integrase proteins. The orfB frame is also expressed independently in two alternative forms: the first uses a rare AUU initiation codon in the orfB phase whereas the second appears to initiate in the orfA phase and is produced by a -1 frameshift mechanism similar to that used in ORFAB expression. A specific IS911 integration reaction using a minimal active junction composed of 51 base-pairs of the right inverted repeat and a flanking phase lambda sequence resembling a second end in inverted orientation has been developed to analyze the functions of these proteins by transcomplementation in vivo. The orfA and orfB frames are shown to be essential and production of ORFAB is shown to stimulate integration in this system, suggesting that this fusion protein is the IS911 transposase.

Amino Acid Sequence↗
PubMed1991

Translational control of transposition activity of the bacterial insertion sequence IS1.

The experiments reported here provide strong evidence indicating that the transposition frequency of the bacterial insertion sequence IS1 is determined principally by two IS1-specified proteins. The first, InsA, was previously shown to bind to the ends of the element and to act as a repressor. We present both physical and genetic evidence which reveals that the second, the InsAB' transposase, is a fusion of InsA with the product of a downstream reading frame, InsB'. Synthesis of this protein occurs by a -1 frameshift between the insA and insB' frames. It requires the presence of an intact retroviral-like frameshift signal composed of an A6C motif and a downstream region able to form several alternative secondary structures. In vivo studies show that IS1 transposition activity depends on the relative rather than on the absolute levels of InsA and InsAB'. The ratio is determined primarily at the translational level by frameshifting and appears to be relatively insensitive to large variations in levels of transcription. This novel homeostatic control could therefore protect IS1 from activation as a consequence of insertion into active transcription units.

Base Composition↗
PubMed1990

Functional similarities between retroviruses and the IS3 family of bacterial insertion sequences?

Members of the IS3 family of insertion sequences are found in a wide range of bacteria. At least 10 members of this family carry two major open reading frames: a small upstream frame (0 phase), and a longer downstream frame in the -1 phase. The downstream frame shows significant similarity at the amino acid level. A highly conserved region of this frame also exhibits notable similarity with a region of the integrase (endonuclease) domain of retroviruses. Although the overall transposition mechanism of the insertion sequence and retroviral elements is certainly different, the two groups may share additional common features, including a -1 frameshift resulting in the production of a fusion protein.

Amino Acid Sequence↗
PubMed1990

Transposition in Shigella dysenteriae: isolation and analysis of IS911, a new member of the IS3 group of insertion sequences.

Twenty-nine clear-plaque mutants of bacteriophage lambda were isolated from a Shigella dysenteriae lysogen. Three were associated with insertions in the cI gene: two were due to insertion of IS600, and the third resulted from insertion of a new element, IS911. IS911 is 1,250 base pairs (bp) long, carries 27-bp imperfect terminal inverted repeats, and generates 3-bp duplications of the target DNA on insertion. It was found in various copy numbers in all four species of Shigella tested and in Escherichia coli K-12 but not in E. coli W. Analysis of IS911-mediated cointegrate molecules indicated that the majority were generated without duplication of IS911. They appeared to result from direct insertion via one end of the element and the neighboring region of DNA, which resembles a terminal inverted repeat of IS911. Nucleotide sequence analysis revealed that IS911 carries two consecutive open reading frames which code for potential proteins showing similarities to those of the IS3 group of elements.

Amino Acid Sequence↗
PubMed1988

[Tetracycline resistance and beta-lactamase production in pharyngeal commensal Neisseria].

Commensal Neisseria may constitute a potential source of resistance genes transferable to pathogenic Neisseria. We tested 150 strains of commensal Neisseria isolated from throat cultures for resistance to tetracycline and beta-lactamase production. Seven strains were high level tetracycline resistant (MIC greater than 16 mg/ml), and minocycline resistant. Only one strain carries a 40 kilobases plasmid. Seven strains were tetracycline resistant (MIC = 8 or 16 mg/l) and minocycline susceptible. Three strains were beta-lactamase producers. These strains were identified as Neisseria perflava or Neisseria sica.

Humans↗
PubMed1986

[Sensitivity of Kingella kingae to antibiotics].

Kingella kingae is a small Gram negative rod of the Neisseriaceae family, formerly called Moraxella kingae. This microorganism is found occasionally in the oral cavity and is capable of causing infections. We report three cases of septic arthritis in children due to K. kingae. In vitro susceptibility of the recovered strains was tested using determination of MICs in agar. The strains were susceptible to penicillin, ampicillin, ticarcillin, cephalothin, cefotaxime, gentamicin, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, and pefloxacin, less susceptible to erythromycin and resistant to lincomycin (MIC 32 mg/l).

Anti-Bacterial Agents↗
PubMed1986

[Osteoarthritis due to Kingella kingae. Apropos of 4 cases].

The authors describe for cases of osteoarthritis with Kingella Kingae, among children. This gram less than 0 germ, which is not well known, tends to be located in bones and joints. In the light of for observations and some of the cases yet observed, we could identified the clinical, biological, and bacteriological characteristics of this germ that has been just described.

Arthritis, Infectious↗
PubMed1983

[Quantitative determination of FTA abs IgM in different stages of syphilis before and after treatment].

The titres of treponemal specific IgM and IgG antibodies were determined by monospecific immunofluorescence (FTA abs IgM/IgG) on 191 sera from 107 patients with treated or untreated syphilis, at various stages and from 10 neonates born from seropositive mothers. IgM antitreponemal antibody was found in all cases of untreated syphilis but two neurosyphilis. After treatment the antibody usually disappeared within one year. However it persisted in three patients treated two years ago or more. When sera from these patients were fractionated by density gradient ultracentrifugation and examined for antitreponemal antibodies of the IgM classe (FTA abs IgM 19S) they never showed detectable concentrations of IgM. False reactive results as false non reactivity due to competitive inhibition, observed with FTA abs IgM can be eliminated after separation of immunoglobulins.

Adult↗