Assessment of seven culture media for the growth and isolation of Capnocytophaga spp.

International audienc

(Eta6-arene) ruthenium(II) complexes and metallo-papain hybrid as Lewis acid catalysts of Diels-Alder reaction in water.

International audienceCovalent embedding of a (eta(6)-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water

Contribution à l'étude biochimique et génétique des b-lactamases des bactéries anaérobies et des Aeromonadaceae

Le but de ce travail a été dans une première partie d effectuer la caractérisation biochimique et génétique des ß-lactamases des bactéries anaérobies du biofilm de la flore buccale : Prevotella spp. (CfxA2), Capnocytophaga spp. (CfxA3 et SPU-1) et Fusobacterium spp. (FUS-1). La mobilité du gène CfxA2 chez Prevotella sp. est due à un transposon et au plasmide pCAP01 chez Capnocytophaga ochracea. La deuxième partie a permis de caractériser les ß-lactamases produites par Aeromonas spp. Bactérie ubiquitaire de l environnement : A. caviae (CAV-1 progéniteur de la ß-lactamase de type ampCplasmidique FOX-1), A. enteropelogenes (TRU-1), A. hydrophila (TEM-24 BLSE plasmidique) et aeromonas media (PER-6 nouvelle BLSE). La distribution des trois types de b-lactamases endogènes (classes B, C et D) était dépendante de l espèce.The aim of the first part of this work was to determine the biochemical and genetic characteristics of b-lactamases of anaerobic bacteria isolated from oral flora biofilm : Prevotella spp. (CfxA2), Capnocytophaga spp. (CfxA3 and SPU-1) and Fusobacterium spp. (FUS-1). The mobility of the CfxA2 gene is due to a transposon in Prevotella species gene and to the pCAP01 plasmid in Capnocytophaga ochracea. In contrast, F. nucleatum polymorphum (FUS-1) and C. sputigena (SPU-1) b-lactamases seem non transferable and species related. In the second part, we characterized b-lactamases produced by Aeromonas spp., an ubiquitous environmental bacterium : a. caviae (CAV-1 the progenitor of FOX-1 a plasmidic ampC type b-lactamase), A. enteropelogenes (TRU-1), A. hydrophila (TEMM-24 a plasmidic ESBL) and aeromonas media (PER-6 a new ESBL). The distribution of the 3 types of endogenous b-lactamases (Classes B, C and D) was species dependent.NICE-BU Sciences (060882101) / SudocSudocFranceF

Distribution des gènes de résistance tet(M), tet(O) et erm(B) chez Streptococcus bovis (analyse selon le phénotype de résistance, le biotype, l'identification ARNr 16s et la notion d'endocardite infectieuse)

NICE-BU Médecine Odontologie (060882102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Experiments with a Layered Transmission Scheme over the Internet

Combining hierarchical coding of data with receiver-driven control appears to be an attractive scheme for the multicast transmission of audio/video flows in a heterogeneous multicast environment such as the Internet. However, little experimental data is available regarding the actual performance of such schemes over the Internet. Previous work such as that on receiver driven layered multicast uses join experiments to choose the best quality signal a receiver can subscribe to. In this paper, we present a receiver-based multicast rate control mechanism based on a recently proposed TCP-friendly unicast mechanism. We have implemented this mechanism and evaluate its performance in conjunction with a simple layered audio coding scheme. We nd that it has interesting convergence and performance properties, but also bring out its limitations

Genetic and Biochemical Characterization of FUS-1 (OXA-85), a Narrow-Spectrum Class D β-Lactamase from Fusobacterium nucleatum subsp. polymorphum

Previous studies have reported β-lactamase-mediated penicillin resistance in Fusobacterium nucleatum, but no β-lactamase gene has yet been identified in this species. An F. nucleatum subsp. polymorphum strain resistant to penicillin and amoxicillin was isolated from a human periodontitis sample. DNA cloning and sequencing revealed a 765-bp open reading frame encoding a new class D β-lactamase named FUS-1 (OXA-85). A recombinant Escherichia coli strain carrying the bla(FUS-1) gene exhibited resistance to amoxicillin with a moderate decrease in the MICs with clavulanic acid. The bla(FUS-1) gene was found in two additional clonally unrelated F. nucleatum subsp. polymorphum isolates. It was located on the chromosome in a peculiar genetic environment where a gene encoding a putative transposase-like protein is found, suggesting a possible acquisition of this class D β-lactamase gene. The FUS-1 enzyme showed the closest ancestral relationship with OXA-63 from Brachyspira pilosicoli (53% identity) and with putative chromosomal β-lactamases of Campylobacter spp. (40 to 42% identity). FUS-1 presents all of the conserved structural motifs of class D β-lactamases. Kinetic analysis revealed that FUS-1 exhibits a narrow substrate profile, efficiently hydrolyzing benzylpenicillin and oxacillin. FUS-1 was poorly inactivated by clavulanate and NaCl. FUS-1 is the first example of a class D β-lactamase produced by a gram-negative, anaerobic, rod-shaped bacterium to be characterized

Role of DNA gyrase and topoisomerase IV mutations in fluoroquinolone resistance of Capnocytophaga spp. clinical isolates and laboratory mutants

International audienceObjectives: Capnocytophaga spp. are often reported to cause bacteraemia and extra-oral infections and are characterized by their significant contribution to resistance to beta-lactam and macrolide-lincosamide-streptogramin antibiotics in the human oral microbiota. The implication of mutations in the quinolone resistance-determining region (QRDR) of DNA gyrase A and B (gyrA and gyrB) and topoisomerase IV (parC and parE) of fluoroquinolone (FQ)-resistant Capnocytophaga spp., hitherto unknown, was explored in this study.Methods: Two reference strains (Capnocytophaga gingivalis ATCC 33624 and Capnocytophaga sputigena ATCC 33612) and four Capnocytophaga spp. isolated from clinical samples were studied. Nine in vitro FQ-resistant mutants, derived from two reference strains and one FQ-susceptible clinical isolate, were selected by successive inoculations onto medium containing levofloxacin. MICs of ofloxacin, norfloxacin, ciprofloxacin, levofloxacin and moxifloxacin were determined. The presumed QRDRs of GyrA, GyrB, ParC and ParE from Capnocytophaga spp. were determined by sequence homology to Bacteroides fragilis and Escherichia coli. PCR primers were designed to amplify the presumed QRDR genetic region of Capnocytophaga spp. and sequence analyses were performed using the BLAST program at the National Center for Biotechnology Information. Results and conclusions: gyrA mutations leading to a substitution from amino acid position 80 to 86 were systematically detected in Capnocytophaga spp. with ciprofloxacin MIC >1 mg/L and considered as the primary target of FQs. No mutational alteration in the QRDR of gyrB was detected. Other mutations in parC and parE led to spontaneous amino acid substitutions of DNA topoisomerase IV subunit B with no alteration in FQ susceptibility

High prevalence of β-lactam and macrolide resistance genes in human oral Capnocytophaga species.

International audienceOBJECTIVES: To determine macrolide-lincosamide-streptogramin (MLS) resistance determinants in the Capnocytophaga genus and to describe the prevalence of β-lactam resistance genes in human oral Capnocytophaga species. METHODS: Forty-eight Capnocytophaga isolates identified by analysis of 16S rRNA sequences were isolated from subgingival samples from 14 haematology patients (HPs), 11 periodontitis patients (PPs) and 17 healthy volunteers (HVs). MICs of β-lactam and MLS antibiotics were obtained for all isolates. blaCfxA, blaCSP-1 (encoding a new class A β-lactamase) and MLS resistance genes [erm(F), erm(B), erm(Q), erm(D), erm(C) and erm(A)] were evaluated using specific PCR and sequencing. RESULTS: In HVs, which had the lowest prevalence of β-lactamase-producing isolates in comparison with the other groups (16%; P < 0.001), Capnocytophaga ochracea was the prominent species (68%; P < 0.03). In PPs, which had a high prevalence of β-lactamase-positive isolates (82%; P < 0.001), Capnocytophaga sputigena was more frequently identified (64%; P < 0.03). In HPs, 50% of isolates were β-lactamase-positive. The more rarely identified species (15%) Capnocytophaga gingivalis, Capnocytophaga granulosa and Capnocytophaga leadbetteri were isolated only from PPs and/or HPs. All β-lactam-resistant isolates (44%) were PCR-positive for blaCfxA (31%) or blaCSP-1 (12.5%). Interestingly, blaCSP-1 was identified only in a subgroup of the C. sputigena species. Twenty-nine percent of isolates were MLS resistant independently of species identification, β-lactamase production or patient group. The MLS-resistant isolates carried the erm(F) or erm(C) gene (93% and 7%, respectively), previously unknown in the Capnocytophaga genus. CONCLUSIONS: Our findings illustrate that Capnocytophaga species are important contributors to the β-lactam and MLS resistance gene reservoir in the oral microbiome