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Biomedical subjects

F Vandenesch

Publications and source records attributed to F Vandenesch.

At least 19 recordsLinked to original sources
PubMed1996

New serotype of Bartonella henselae in endocarditis and cat-scratch disease.

BACKGROUND: The fastidious nature of Bartonella henselae is such that demonstration of clinical infection relies mainly on serological or molecular biological methods. Only five isolates have been obtained from patients with cat-scratch disease (CSD) and none from endocarditis. METHODS: We isolated B henselae from a CSD patient and, for the first time, from a patient with endocarditis. The isolates were characterised on the basis of morphology, biochemistry, cell-wall fatty-acid analysis, PCR-restriction fragment length polymorphism analysis of the 16-23S intragenic spacer region, and 16S rRNA gene sequences. Characterisation of these isolates indicated them to belong to a new serogroup, which we have called "Marseille", and to a new genotype based on the 16S rRNA gene sequence. The new variant was incorporated into an immuno-fluorescence antibody test (IFAT), which was used to reassess serum samples from 113 CSD patients who were seronegative with the conventional IFAT. FINDINGS: 18 (16%) of these apparently seronegative patients yielded significantly raised titres. 20 CSD patients who were seropositive as judged by the conventional IFAT remained seropositive with the new IFAT. INTERPRETATION: Antigenic variability within the species is one possible reason for inconsistent results in the serological diagnosis of CSD.

Adult↗
PubMed1996

Coagulase-negative staphylococci isolated from two cases of toxic shock syndrome lack superantigenic activity, but induce cytokine production.

Two strains of Staphylococcus epidermidis isolated from patients with toxic shock symptoms have been reported to carry genes related to S. aureus enterotoxins B and C by dot-blot hybridisation, although the corresponding superantigenic toxins were not detected immunologically. We here show that these strains produce no superantigens capable of stimulating proliferation of human mononuclear leukocytes or rabbit splenocytes, and that no DNA homologous to the seb or sec genes can be detected by PCR. However, stimulation of human monocytes by whole killed bacteria induced dose-dependent production of the cytokines TNF alpha, IL-1 beta and IL-6, which may be responsible for the clinical symptoms in these patients.

Antigens, Bacterial↗
PubMed1995

The agr P2 operon: an autocatalytic sensory transduction system in Staphylococcus aureus.

The synthesis of virulence factors and other exoproteins in Staphylococcus aureus is controlled by the global regulator, agr. Expression of secreted proteins is up-regulated in the postexponential growth phase, whereas expression of surface proteins is down-regulated by agr. The agr locus consists of two divergent operons, transcribed from neighboring but non-overlapping promoters, P2 and P3. The P2 operon sequence, reported here, contains 4 open reading frames, agrA, C, D, and B, of which A and C appear to encode proteins of a classical 2-component signal transduction pathway. The P3 operon specifies a 0.5 kb transcript, RNA III, which is the actual effector of the agr response, and, incidentally, encodes the agr-regulated peptide delta-hemolysin. Transcriptional fusions have shown that both P2 and P3 are agr sensitive (function in an agr+ but not in an agr- background) and deletion analysis has shown that all four of the P2 ORFs are involved; agrA and agrC seem to be absolutely required for the transcriptional activation of the agr locus, whereas agrB and agrD seem to be partially required. Since transcription of P2 requires P2 operon products, the P2 operon is autocatalytic, and is thus admirably suited to the need for rapid production of exoproteins at a time when overall growth is coming to a halt.

Amino Acid Sequence↗
PubMed1995

Bartonella (Rochalimaea) quintana endocarditis in three homeless men.

BACKGROUND: Bartonella (Rochalimaea) quintana is the agent of trench fever and is transmitted by the body louse. We searched for this organism in three alcoholic homeless men with endocarditis. METHODS: Blood samples were cultured on a human endothelial cell line and on blood agar. Bacteria were identified by sequencing the amplified 16S ribosomal RNA gene. The presence of bartonella in tissue was assessed by Gram's staining, immunostaining, and polymerase-chain-reaction amplification. Serologic studies for antibodies to bartonella species were performed by indirect immunofluorescence and Western immunoblotting. RESULTS: B. quintana was isolated from one patient in the blood-agar culture and from the other two patients in the endothelial-cell culture. The organism was also identified by both immunostaining and molecular techniques in the valvular vegetations from the three patients and in a cervical lymph node from one patient. The 16S ribosomal RNA gene sequences of the three isolates were almost identical to that of the prototype strain of B. quintana. High titers of antibodies to B. quintana were detected in all three patients, but so were cross-reacting antibodies to chlamydia species. In all three patients studies were repeatedly negative for antibodies to the human immunodeficiency virus. CONCLUSIONS: B. quintana is a cause of endocarditis in homeless patients and may be serologically misdiagnosed as a chlamydial infection.

Adult↗
PubMed1995

[Aseptic meningitis. Demonstration of bacterial DNA in cerebrospinal fluid by gene amplification].

OBJECTIVE: To develop a diagnostic tool to recognize whether a postoperative meningitis occurring in neurosurgical patients is of bacteriological origin or not, in detecting in CSF bacterial DNA with the polymerase chain reaction (PCR) technique. STUDY DESIGN: Laboratory study. PATIENTS: Twenty-seven neurosurgical ICU patients associating, in the postoperative period, the CDC criteria of meningitis and a neutrophil polymorphonuclear count over 100 cells.mm-3 were allocated either into the MB+ group (n = 7) when their CSF culture was positive or in the MB- group (n = 20) when the culture was sterile. The CSF of 43 neurosurgical ICU patients without postoperative clinical and biological features of meningitis acted as controls. Sixteen specimens out of the 43 were inoculated with bacteria at a known concentration. METHODS: The CSF specimens of all patients were tested for the presence of eurcaryote DNA using the PCR technique. Beforehand its sensitivity had been assessed using the inoculated CSF of control group: a positive amplification at 20 cycles was equivalent to 10(5) CFU.mL-1 and a positive amplification at 25 cycles to 10(3) CFU.mL-1. RESULTS: In the 43 sterile control CSF specimens the amplification was negative in all at 20 cycles and in 42 at 25 cycles. In the 16 previously sterile control specimens supplemented with bacteria, as well as in the CSF of all 7 patients of MB+ group the amplification was positive at 20 and 25 cycles. In those of MB- group the amplification was negative in all at 20 cycles, but was positive in 19 out of 20 at 25 cycles. Southern blot with specific procaryote probes was positive with amplification products from CSF of MB+ and MB- groups and negative with control CSFs and human DNA. DISCUSSION: The presence of bacteria in CSF of patients sustaining a meningitis can be accurately detected through their DNA. Postoperative aseptic meningitides may have a bacterial origin. PCR can be used as a routine technique to provide a diagnosis of bacterial meningitis in less than 6 hours. Additionally specific oligonucleotides allow to identify the bacteria in less than 12 hours.

Adolescent↗
PubMed1995

Identification and ribotypes of Staphylococcus caprae isolates isolated as human pathogens and from goat milk.

We report five cases of human infection with Staphylococcus caprae. Two were community acquired (one case each of endocarditis and urinary tract infection); the other three were acquired in a hospital (two cases of bacteremia associated with intravenous access and one case of urinary tract infection). Analysis of human isolates and goat isolates from eight herds showed that they could be misidentified by some commercial identification systems but were clearly identified as S. caprae by ribotyping, according to their species-specific ribotype. Phylogenetic methods applied to the ribotypes did not reveal two distinct lineages corresponding to the goat and human origins of the isolates, although human ribotypes were clearly distinguishable by the presence of a core of four specific bands. The latter observation may reflect some degree of evolutionary change within the species between human and goat isolates.

Adult↗
PubMed1995

Catheter-related bacteremia associated with coagulase-positive Staphylococcus intermedius.

We report a case of catheter-related bacteremia in a 63-year-old patient caused by Staphylococcus intermedius. Clinical resolution of the infection was obtained after removal of the intravenous device and antibiotic treatment. This observation emphasizes the risk of confusion between S. intermedius and Staphylococcus aureus if only a coagulase test is done.

Bacteremia↗
PubMed1994

Coagulase deficiency in clinical isolates of Staphylococcus aureus involves both transcriptional and post-transcriptional defects.

The molecular basis of the non-expression of coagulase was investigated for 14 coagulase-negative isolates of Staphylococcus aureus obtained from different clinical samples. These isolates had typical S. aureus characteristics such as production of clumping factor, DNAase and protein A, but, with one exception, failed to produce detectable amounts of alpha-haemolysin. All 14 strains had DNA homologous to the coagulase gene (coa), but a coa-specific transcript was found in only seven of them. alpha-Haemolysin mRNA was detected in only eight strains without direct correlation to coa-mRNA expression. Thus, coagulase and alpha-haemolysin deficiencies in S. aureus may involve either transcriptional or post-transcriptional alterations although additional regulatory factors may influence the expression of both genes.

Bacterial Toxins↗
PubMed1994

Glycerol monolaurate inhibits the production of beta-lactamase, toxic shock toxin-1, and other staphylococcal exoproteins by interfering with signal transduction.

Glycerol monolaurate (GML) is a naturally occurring surfactant that is used widely as an emulsifier in the food and cosmetics industries and is generally regarded as lacking in important biological activities. The recent observation that it inhibits the production of staphylococcal toxic shock toxin-1 (P. M. Schlievert, J. R. Deringer, M. H. Kim, S. J. Projan, and R. P. Novick, Antimicrob. Agents Chemother. 36:626-631, 1992) is therefore rather surprising and raises the interesting question of how such a compound might interact with cells. In this report, we show that GML inhibits the synthesis of most staphylococcal toxins and other exoproteins and that it does so at the level of transcription. We find that GML blocks the induction but not the constitutive synthesis of beta-lactamase, suggesting that it acts by interfering with signal transduction.

Bacterial Proteins↗
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↗