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Biomedical subjects

F Vandenesch

Publications and source records attributed to F Vandenesch.

At least 91 records · Page 5Linked to original sources
PubMed1994

Coagulase expression in Staphylococcus aureus is positively and negatively modulated by an agr-dependent mechanism.

Expression of staphylocoagulase by agr+ Staphylococcus aureus depends on the growth phase, being maximal during exponential growth and decreasing sharply postexponentially, while an agr-deleted strain continuously expresses an intermediate level of coagulase. Therefore, coagulase expression appears to be both positively and negatively modulated by an agr-dependent mechanism.

Coagulase↗
PubMed1994

Clotting activity in Staphylococcus schleiferi subspecies from human patients.

Staphylococcus schleiferi subsp. schleiferi is a coagulase-negative staphylococcus, usually present as a contaminant in human specimens. A near relative, S. schleiferi subsp. coagulans, possesses coagulase activity but has not been reported from humans. We here describe three isolates of pseudocoagulase-positive S. schleiferi subsp. schleiferi and one isolate of S. schleiferi subsp. coagulans from human patients. The pseudocoagulase from the S. schleiferi subsp. schleiferi isolates differs from S. aureus staphylocoagulase by being sensitive to a combination of protease inhibitors (aprotinin, N-ethylmaleimide, and heparin). These isolates could all easily be confused with S. aureus in a typical clinical laboratory, since they all possess a heat-stable DNase and promote clotting formation. Moreover, S. schleiferi subsp. coagulans produces protein A, and S. schleiferi subsp. schleiferi expresses a clumping factor (fibrinogen affinity factor). Southern blot hybridization with an S. aureus coa-specific probe revealed no sequence related to the coa gene in any of the S. schleiferi isolates, and their riboprobe profiles and biochemical characteristics were typical of S. schleiferi subspecies, not of S. aureus. This study demonstrates that both subspecies of S. schleiferi can promote clotting of rabbit plasma in the standard tube test for coagulase.

Animals↗
PubMed1993

Agr-related sequences in Staphylococcus lugdunensis.

Sequences related to the Staphylococcus aureus accessory gene regulator (agr) were demonstrated in S. lugdunensis by Southern blot analysis of 13 strains and sequencing of the S. lugdunensis agr-like locus (agr-sl). Northern blot analysis of cellular RNA revealed the presence of a transcript having homology with the agr-P3 transcript (RNAIII) for three of the six strains tested. The three strains containing this transcript produce a hemolysin with phenotypic properties similar to that of S. aureus delta-hemolysin. Nevertheless, unlike agr-P3 from S. aureus, agr-sl does not encode any potential peptide homologous to S. aureus delta-hemolysin, suggesting that the hemolytic activity detected in S. lugdunensis is encoded elsewhere and may be controlled by agr-sl.

Amino Acid Sequence↗
PubMed1993

Role of bacteriophages in genomic variability of related coagulase-negative staphylococci.

DNA analysis using pulsed-field gel electrophoresis (PFGE) has emerged as one of the most sensitive epidemiological tools for the characterization of coagulase-negative staphylococci (CNST). The significance of some minor differences observed between the DNA restriction pulsed patterns of two CNST strains are difficult to interpret since they can theoretically be due to minor chromosomal rearrangements or to phage DNA integration. The latter possibility was investigated by comparing DNA restriction patterns of Staphylococcus epidermidis strains with those of their lysogenized derivatives. In vitro lysogenisation was obtained by exposing the strains to phage 118II. The pulsed patterns of the lysogenized strains were compared to those of their parental strains, revealing a shift in size of approximately 50 kb in a single band which was shown by Southern blotting to contain prophage. One strain was lysogenized ten times, revealing a potential preferred attachment site for phage 118II. These results confirm that chromosomal integration of a phage can be responsible for minor stable variations in DNA restriction patterns.

Blotting, Southern↗
PubMed1993

Epidemiological markers of coagulase-negative staphylococci.

Several different epidemiological typing methods have been used in studies of coagulase-negative staphylococci; these include biotyping, antibiotic susceptibility pattern analysis, serological typing, phage typing, slime production detection, protein profile analysis, immunoblot fingerprinting and DNA typing. The most frequently used tests are antibiotic susceptibility and extrachromosomal DNA banding patterns. Comparison of chromosomal DNA restriction patterns is facilitated when the fragments are separated by pulsed-field electrophoresis. Typing variations occur quite frequently even in isolates of demonstrated clinical significance. Caution should therefore be exercised in denying the clinical relevance of coagulase-negative staphylococci, even when successive isolates show distinct typing differences.

Bacteriological Techniques↗
PubMed1993

Endocarditis due to Staphylococcus lugdunensis: report of 11 cases and review.

Staphylococcus lugdunensis is a recently described coagulase-negative staphylococcus that has been associated with human infections, including nine reported cases of infective endocarditis. The present study describes 11 other cases of infective endocarditis caused by this organism. The infection occurred in patients whose mean age was 61 years and was community-acquired in most cases. A preexisting cardiac abnormality was present in eight patients. Three of the 11 infections involved prosthetic valves. Ten strains were susceptible to penicillin. The destructive course of the infection, the need for valve replacement, and the high mortality suggest that S. lugdunensis causes a virulent form of endocarditis.

Adult↗
PubMed1993

[Bacterial endocarditis: current bacteriological data].

The bacteria causing infective endocarditis have not changed significantly despite the diversity of potential portals of entry. Streptococci (viridans) cause 35 to 45% of cases of endocarditis. Group D streptococci of gastrointestinal origin cause about 20% of cases of endocarditis: Streptococcus bovis is the most commonly isolated species followed by the enterococcus. The beta-haemolytic streptococci of Groups A, B, C and G are rarely isolated. Seventeen to thirty per cent of endocarditis is caused by staphylococci, above all Staphylococcus aureus. These infections are mainly observed in patients with prosthetic valves or intravenous catheters and in intravenous drug addicts. With respect to gram-negative bacilli, enterobacteria are rarely responsible for endocarditis and those of the HACEK group (Haemophilus, Actinobacillus, Cardiobacterium, etc.) were isolated in 3% of cases. Q fever and Chlamydia endocarditis are rare, as are fungal infections usually due to Candida. Endocarditis with negative blood cultures is still observed in about 10% of cases.

Blood↗
PubMed1992

Cadmium-resistance plasmid in Staphylococcus lugdunensis.

Plasmids that confer resistance to cadmium (MIC > or = 125 microM), were found in 18 out of 30 independent Staphylococcus lugdunensis strains from clinical specimens. Variants that were cured of their plasmid were cadmium sensitive. Restriction endonuclease sites of a 3.2-kb cadmium-resistance plasmid of S. lugdunensis, designated pLUG10, were similar to those of pOX6, a S. aureus cadmium-resistance plasmid containing the cadB gene. Southern-blot hybridisation was performed with a probe intragenic to cadB. Hybridisation was found with the cadB probe in the cadmium-resistant S. lugdunensis isolates to the 2.9-, 3.2- and 3.7-kb plasmids. These findings suggest that cadmium-resistance in some S. lugdunensis strains is due to a gene sharing homology with the cadB gene of S. aureus.

Cadmium↗
PubMed1992

Comparison of coagulase-negative staphylococci by pulsed-field electrophoresis.

Five pathogenic strains each of Staphylococcus epidermidis, S. haemolyticus, S. lugdunensis and S. schleiferi were analysed by conventional electrophoresis and field inversion gel electrophoresis. For these coagulase-negative staphylococci, the restriction endonuclease SmaI emerged as the most suitable enzyme for pulsed-field electrophoresis by providing an adequate number of clearly separated DNA fragments. Field inversion gel electrophoresis confirmed the differences among strains already discriminated by conventional electrophoresis, and furthermore, differentiated strains which had previously appeared identical. Among the species that were studied, S. epidermidis showed great genomic diversity with a few common bands. On the contrary, S. haemolyticus, S. lugdunensis and S. schleiferi showed less diversity. Although these minor variations may be epidemiologically significant, this question has to be investigated on a larger number of strains.

Coagulase↗
PubMed1991

Delta-like haemolysin produced by Staphylococcus lugdunensis.

Thirty independent clinical isolates of Staphylococcus lugdunensis were tested for expression of haemolysin characteristics of Staphylococcus aureus and for the presence of DNA sequences with homology to S. aureus toxin genes. Twenty-six strains produced a thermostable haemolysin with greatest activity against rabbit erythrocytes. DNA-DNA hybridisation was performed with S. lugdunesis DNA and probed with the alpha, beta, delta and gamma toxin gene probes of S. aureus as well as that for coagulase. Hybridisation was found with the delta probe in 28 strains including 6 which did not express haemolysin. Two strains did not hybridise with any of the probes. These findings suggest that S. lugdunensis strains produce a delta-like toxin which shares homology with the delta toxin of S. aureus.

Bacterial Proteins↗
PubMed1991

A temporal signal, independent of agr, is required for hla but not spa transcription in Staphylococcus aureus.

Staphylococcus aureus exoprotein expression is controlled by a global regulon known as agr. This system activates transcription of some target genes and represses transcription of others. Target genes expressed postexponentially such as alpha-hemolysin (hla) are activated by agr; target genes expressed during exponential phase such as protein A (spa) are repressed by agr. A unique feature of the agr system is that this transcriptional regulation is mediated by a 517-nucleotide transcript, RNAIII. While it is clear that agr differentially regulates the expression of exponential and postexponential exoproteins, the precise role of agr in the temporal control of these events has not yet been explored. In this report, we examine the effects of expressing RNAIII, the agr regulator, under the control of the inducible beta-lactamase (bla) promoter at different times in the growth cycle. We confirm previous results showing that agr is required for postexponential-phase expression of hla and further show that a separate postexponential-phase signal independent of agr function is also needed for activation of hla transcription. We also show that in an agr mutant transcription of spa occurs throughout the growth cycle, is inhibited immediately upon induction of RNAIII, and is thus indifferent to the postexponential signal required for hla activation.

Bacterial Toxins↗
PubMed1990

Relationship between free amoeba and Legionella: studies in vitro and in vivo.

In 1980, Robowtham demonstrated that Legionella multiplies in free amoeba cytoplasm and hypothesized that the amoeba could act as a reservoir of virulent bacteria. In this paper we report various aspects of the relationship between amoeba and Legionella. A liquid medium co-culture method was applied to Acanthamoeba sp. and Legionella pneumophila serogroup 1. Within 4 days, Legionella growth increased by 2 log s CFU/ml. Using a direct immunofluorescence assay and electron microscopy, Legionella was shown to grow abundantly inside phagosomes, and bacteria and/or antigen were present on the cytoplasmic membrane of the amoeba. These aspects are very similar to those observed with Legionella-infected alveolar macrophages. The morphology and structure of Legionella cells were modified after 20 days of co-culture: - viable bacteria showed large fatty cytoplasmic inclusions, - gas liquid chromatography analysis demonstrated a decrease in the i16:0 fatty acid ratio. Cystic forms of amoeba were abundant but none contained viable Legionella. In an in-vivo study using a guinea-pig aerosol infection model, we compared the virulence of Legionella in co-culture with Legionella grown on charcoal dialysed yeast extract (CDYE) agar medium. The Legionella obtained by co-culture had an LD 50 (50% lethal dose) similar to that obtained for those grown on CDYE, showing that bacterial virulence is preserved in the cellular model.

Acanthamoeba↗
PubMed1989

Susceptibilities to ceftriaxone of streptococcal strains associated with infective endocarditis.

We determined the bactericidal activity of ceftriaxone on 20 streptococci isolated from patients with infective endocarditis and that of penicillin G on 5 strains. The MICs of ceftriaxone were less than or equal to 2 micrograms/ml and the MBCs were low for 5 nontolerant strains (less than or equal to 2 micrograms/ml) and high for 15 tolerant strains (greater than or equal to 16 micrograms/ml). The maximal reduction of the viable bacterial counts after 24 h of exposure to antibiotic was achieved for a concentration of ceftriaxone of 4, 32 and 256 micrograms/ml, respectively for 5, 10 and 19 strains. The activity of penicillin G was similar.

Ceftriaxone↗
PubMed1988

Postoperative infant septicemia caused by Pseudomonas luteola (CDC group Ve-1) and Pseudomonas oryzihabitans (CDC group Ve-2).

Pseudomonas luteola (CDC group Ve-1) and Pseudomonas oryzihabitans (CDC group Ve-2) were both isolated from the same blood culture of a 5-month-old infant, 8 days after open-heart surgery. He quickly responded to appropriate antibiotics. Carbon substrate assimilation tests and fatty acid analysis clearly differentiated these two rarely pathogenic organisms.

Humans↗
PubMed1987

Hemoglobin J-Baltimore (beta 16(A13)Gly----Asp): interference with the assay of HbA1c.

Three independent cases of Hemoglobin J-Baltimore(beta 16(A13)Gly----Asp) were detected through the assay of HbA1c in diabetic patients. Using chromatography on Bio-Rex 70 resin, one large peak replaced the usually well resolved peaks of HbA1a + b and HbA1c. The species that overlapped the latter fractions was identified as HbJ1c. HbJ-Baltimore itself was identified using HPLC of the beta-chain tryptic peptides. This observation emphasizes the errors that hemoglobin variants may introduce in the assay of HbA1c.

Adult↗