Corentine Alauzet

Effects of the Trem-1 pathway modulation during mesenteric ischemia-reperfusion in rats

Objectives: The triggering receptor expressed on myeloid cells (TREM)-1, a receptor expressed on the surface of neutrophils and monocytes/macrophages, synergizes with the Toll-like receptors in amplifying the inflammatory response mediated by microbial components. Because the pathogenesis of ischemia-reperfusion-induced gastrointestinal tissue injury and multiple organ failure implies leukocyte activation and bacterial translocation, we hypothesized that the TREM-1 pathway modulation would prove beneficial in this setting. Design: Animal study. Setting: Research laboratory. Subjects: Adult male Wistar rats (250–300 g). Interventions: Rats were subjected to intestinal ischemia-reperfusion induced by occlusion of the superior mesenteric artery during 60 mins and reperfused for 180 mins. At the time of reperfusion, animals were administered with LP17 (a synthetic TREM-1 inhibitor), a control peptide, or a vehicle (normal saline). Plasma concentrations of tumor necrosis factor-&agr;, interleukin-6, and soluble TREM-1 were measured by enzyme-linked immunosorbent assay. Hepatic activation of the transcriptional factor nuclear factor-&kgr;B was assessed by electrophoretic mobility shift assay. Hepatic oxidant-antioxidant balance was estimated by measurement of lipid peroxidation and catalase activity. Ileal mucosal permeability was estimated by fluorescein dextran-4 clearance and bacterial translocation by mesenteric lymph nodes culture. Measurements and Main Results: Ischemia-reperfusion was associated with cardiovascular collapse, lactic acidosis, and systemic and hepatic inflammatory response that were partly prevented by LP17 administration. Liver lipid peroxidation and catalase depletion were attenuated by LP17. Ischemia-reperfusion induced a marked increase in ileal mucosal permeability and an associated bacterial translocation that was also prevented by TREM-1 modulation. LP17 delayed mortality. Conclusions: The modulation of the TREM-1 pathway by the means of a synthetic peptide may be useful during acute mesenteric ischemia.

New insights into Prevotella diversity and medical microbiology

In light of recent studies based on cultivation-independent methods, it appears that the diversity of Prevotella in human microbiota is greater than was previously assumed from cultivation-based studies, and that the implication of these bacteria in several human diseases was unrecognized. While some Prevotella taxa were found during opportunistic infections, changes in Prevotella abundance and diversity were discovered during dysbiosis-associated diseases. As member of the microbiota, Prevotella may also be considered as a reservoir for resistance genes. Greater knowledge on Prevotella diversity, as well as new insights into its pathogenic potential and implication in dysbiosis are expected from the use of human microbe identification microarrays, from whole-genome sequence analyse, and from the NIH Human Microbiome Project data. New approaches, including molecular-based methods, could contribute to improve the diagnosis of Prevotella infections.

Proposal to unify Clostridium orbiscindens Winter et al. 1991 and Eubacterium plautii (Séguin 1928) Hofstad and Aasjord 1982, with description of Flavonifractor plautii gen. nov., comb. nov., and reassignment of Bacteroides capillosus to Pseudoflavonifractor capillosus gen. nov., comb. nov.

We isolated several strains from various clinical samples (five samples of blood, four of intra-abdominal pus and one of infected soft tissue) that were anaerobic, motile or non-motile and Gram-positive rods. Some of the strains formed spores. Phylogenetic analysis of the 16S rRNA gene sequence showed that these organisms could be placed within clostridial cluster IV as defined by Collins et al. [(1994). Int J Syst Bacteriol 44, 812-826] and shared more than 99 % sequence similarity with Clostridium orbiscindens DSM 6740(T) and Eubacterium plautii DSM 4000(T). Together, they formed a distinct cluster, with Bacteroides capillosus ATCC 29799(T) branching off from this line of descent with sequence similarities of 97.1-97.4 %. The next nearest neighbours of these organisms were Clostridium viride, Oscillibacter valericigenes, Papillibacter cinnamivorans and Sporobacter termitidis, with sequence similarities to the respective type strains of 93.1-93.4, 91.2-91.4, 89.8-90 and 88.7-89.3 %. On the basis of biochemical properties, phylogenetic position, DNA G+C content and DNA-DNA hybridization, it is proposed to unify Clostridium orbiscindens and Eubacterium plautii in a new genus as Flavonifractor plautii gen. nov., comb. nov., with the type strain Prévot S1(T) (=ATCC 29863(T) =VPI 0310(T) =DSM 4000(T)), and to reassign Bacteroides capillosus to Pseudoflavonifractor capillosus gen. nov., comb. nov., with the type strain CCUG 15402A(T) (=ATCC 29799(T) =VPI R2-29-1(T)).

Metronidazole Resistance in Prevotella spp. and Description of a New nim Gene in Prevotella baroniae

ABSTRACT Nonduplicate clinical isolates of Prevotella spp. recovered from patients hospitalized between 2003 and 2006 in two French tertiary-care teaching hospitals were investigated for their susceptibility to metronidazole and the presence of nim genes. Of the 188 strains tested, 3 isolates displayed reduced susceptibility to metronidazole after 48 h of incubation, while 27 additional isolates exhibited heterogeneous resistance after prolonged incubation; all 30 of the isolates were nim negative. Among the remaining 158 isolates, 7 nim-positive isolates were detected. All of these strains were identified as Prevotella baroniae by 16S rRNA gene sequence analysis and contained a new nim gene, named nimI, as determined by DNA sequence analysis. Chromosomal localization of this single-copy gene was demonstrated in all clinical isolates as well as in type strain P. baroniae DSM 16972 by using Southern hybridization. No known associated insertion sequence elements were detected upstream of the nimI gene in any of the nim-positive strains by PCR mapping. After prolonged exposure to metronidazole, stable resistant subpopulations could be selected in nimI-positive Prevotella isolates (n = 6) as well as in nim-negative Prevotella isolates (n = 6), irrespective of their initial susceptibility to this antibiotic. This study is the first description of a new nitroimidazole resistance gene in P. baroniae which seems to be silent and which might be intrinsic in this species. Moreover, our findings highlight the fact that high-level resistance to metronidazole may be easily induced in both nim-positive and nim-negative Prevotella sp. strains.

Gluconobacter as Well as Asaia Species, Newly Emerging Opportunistic Human Pathogens among Acetic Acid Bacteria

ABSTRACT Acetic acid bacteria (AAB) are broadly used in industrial food processing. Among them, members of the genera Asaia, Acetobacter, and Granulibacter were recently reported to be human opportunistic pathogens. We isolated AAB from clinical samples from three patients and describe here the clinical and bacteriological features of these cases. We report for the first time (i) the isolation of a Gluconobacter sp. from human clinical samples; (ii) the successive isolation of different AAB, i.e., an Asaia sp. and two unrelated Gluconobacter spp., from a cystic fibrosis patient; and (iii) persistent colonization of the respiratory tract by a Gluconobacter sp. in this patient. We reviewed the main clinical features associated with AAB isolation identified in the 10 documented reports currently available in the literature. Albeit rare, infections as well as colonization with AAB are increasingly reported in patients with underlying chronic diseases and/or indwelling devices. Clinicians as well as medical microbiologists should be aware of these unusual opportunistic pathogens, which are difficult to detect during standard medical microbiological investigations and which are multiresistant to antimicrobial agents. Molecular methods are required for identification of genera of AAB, but the results may remain inconclusive for identification to the species level.

Multilocus analysis reveals diversity in the genus Tissierella: Description of Tissierella carlieri sp. nov. in the new class Tissierellia classis nov.☆

The genus Tissierella and its relatives Tepidimicrobium, Soehngenia and Sporanaerobacter comprise anaerobic Gram-positive bacilli classified along with Gram-positive cocci in a family with controversial placement designated as incertae sedis XI, in the phylum Firmicutes. We performed a top-down reappraisal of the taxonomy from the phylum to the species level within the genus Tissierella. Reconstruction of high-rank 16S rRNA gene-based phylogenies and their interpretation in a taxonomic purpose allowed defining Tissierellia classis nov. within the phylum Firmicutes while the frames of Tissierellales ord. nov. and Tissierellaceae fam. nov. have to be further strengthened. For species delineation in the genus Tissierella, we studied a population of clinical strains. Beside Tissierella praeacuta, a sub-population of five strains formed a clade in multilocus phylogenies (16S rRNA, cpn60, tpi, recA and spo0A genes). Data such as 16S rRNA gene similarity level, population structure, chromosome organization and murein type indicated that this clade corresponded to a novel species for which the name Tissierella carlieri sp. nov. is proposed, with type strain LBN 295(T)=AIP 268.01(T)=DSM 23816(T)=CCUG 60010(T). Such an approach, associating a phylogenetic reappraisal of high-level taxonomic ranks with weak taxonomic structure and a population study for genus and species delineation is needed to strengthen the taxonomic frame of incertae sedis groups in the phylum Firmicutes.

Effects of the TREM 1 pathway modulation during hemorrhagic shock in rats.

The triggering receptor expressed on myeloid cells (TREM) 1, a receptor expressed on the surface of neutrophils and monocytes/macrophages, synergizes with the Toll-like receptors in amplifying the inflammatory response mediated by microbial components. Because the pathogenesis of severe blood loss-induced excessive inflammation and multiple organ failure implies leukocyte activation and bacterial translocation, we hypothesized that the TREM-1 pathway modulation would prove beneficial in this setting. Wistar rats were subjected to a 1-h period of hemorrhagic shock and then reperfused with shed blood and ringer lactate for 1 h. At the time of reperfusion, animals were administered with LP17 (a synthetic soluble TREM-1 decoy receptor), a control peptide, or a vehicle (isotonic sodium chloride solution). Plasma concentration of TNF-&agr;, IL-6, and soluble TREM-1 were measured by enzyme-linked immunosorbent assay. Lung permeability was assessed by the weight-dry ratio and fluorescein isothiocyanate-labeled albumin lung-blood ratio. Organ dysfunction was appreciated by measuring plasma aspartate aminotransferase and urea concentrations. Bacterial translocation was estimated by blood, mesenteric lymph nodes, and spleens culture. Hemorrhagic shock associated with cardiovascular collapse, lactic acidosis, systemic inflammatory response, and organ dysfunction that was partly prevented by LP17 administration. Hemorrhagic shock induced a marked increase in lung permeability that was also prevented by TREM-1 modulation. Finally, LP17 improved survival. Thus, the early modulation of the TREM-1 pathway by means of a synthetic peptide may be useful during severe hemorrhagic shock in rats in preventing organ dysfunction and improving survival.ABBREVIATIONS-CFU-colony-forming unit; CP-control peptide; Ig-immunoglobulin; MLN-mesenteric lymph nodes; TLR-Toll-like receptor; TREM-triggering receptor expressed on myeloid cells

Effects of a TREM-like transcript 1-derived peptide during hypodynamic septic shock in pigs.

ABSTRACT The objective of this study was to determine the effects of a TREM (triggering receptor expressed on myeloid cells 1)–like transcript 1–derived peptide (LR12) administration during septic shock in pigs. Two hours after induction of a fecal peritonitis, anesthetized and mechanically ventilated adult male minipigs were randomized to receive LR12 (n = 6) or its vehicle alone (normal saline, n = 5). Two animals were operated and instrumented without the induction of peritonitis and served as controls (sham). Resuscitation was achieved using hydroxyethyl starch (up to 20 mL/kg) and norepinephrine infusion (up to 10 &mgr;g/kg per minute). Hemodynamic parameters were continuously recorded. Gas exchange, acid-base status, organ function, and plasma cytokines concentrations were evaluated at regular intervals until 24 h after the onset of peritonitis when animals were killed under anesthesia. Peritonitis induced profound hypotension, myocardial dysfunction, lactic acidosis, coagulation abnormalities, and multiple organ failure. These disorders were largely attenuated by LR12. In particular, cardiovascular failure was dampened as attested by a better mean arterial pressure, cardiac index, cardiac power index, and SvO2, despite lower norepinephrine requirements. LR12, a TREM-like transcript 1–derived peptide, exhibits salutary properties during septic shock in adult minipigs.

Characterization of a New blaOXA-48-Carrying Plasmid in Enterobacteriaceae

ABSTRACT In this work, we characterized a new, 160-kb, blaOXA-48-harboring IncL/M-type plasmid isolated from a Klebsiella pneumoniae strain from France. Moreover, we report the transfer of a 60-kb OXA-48-encoding plasmid from Klebsiella pneumoniae to other Enterobacteriaceae in two patients.

Comparison of seven methods for extraction of bacterial DNA from fecal and cecal samples of mice

Analysis of bacterial DNA from fecal samples of mice is commonly performed in experimental studies. Although DNA extraction is a critical step in various molecular approaches, the efficiency of methods that may be used for DNA extraction from mice fecal samples has never been evaluated. We compared the efficiencies of six widely used commercial kits (MasterPure™ Gram Positive DNA Purification Kit, QIAamp® DNA Stool Mini Kit; NucliSENS® easyMAG®, ZR Fecal DNA MiniPrep™, FastDNA® SPIN Kit for Feces and FastDNA® SPIN Kit for Soil) and a non-commercial method for DNA isolation from mice feces and cecal contents. DNA quantity and quality were assessed by fluorometry, spectrophotometry, gel electrophoresis and qPCR. Cell lysis efficiencies were evaluated by qPCR targeting three relevant bacteria in spiked specimens. For both feces and intestinal contents, the most efficient extraction method was the FastDNA® SPIN Kit for Soil.