Comparative evaluation of the antimicrobial activity of 19 essential oils.

In our research on natural compounds efficient against human pathogen or opportunist microorganisms contracted by food or water, the antimicrobial activity of 19 essential oils (EOs) was investigated against 11 bacterial species (6 Gram positive, 5 Gram negative) and 7 fungal species (2 dermatophytes, 1 mould, 4 yeasts) using microdilution assays. Five essential oils were obtained from Tunisian plants (EOtun): Artemisia herba-alba Asso, Juniperus phoenicea L., Rosmarinus officinalis L.

Activity of Six Essential Oils Extracted from Tunisian Plants against Legionella pneumophila.

The aim of this study was to investigate the composition of six essential oils extracted from Tunisian plants, i.e., Artemisia herba-alba Asso, Citrus sinensis (L.

Intra-amoeba multiplication induces chemotaxis and biofilm colonization and formation for Legionella.

Legionella pneumophila, a facultative intracellular bacterium, is the causative agent of legionellosis. In the environment this pathogenic bacterium colonizes the biofilms as well as amoebae, which provide a rich environment for the replication of Legionella. When seeded on pre-formed biofilms, L.

VBNC Legionella pneumophila cells are still able to produce virulence proteins.

Legionella pneumophila is the agent responsible for legionellosis. Numerous bacteria, including L. pneumophila, can enter into a viable but not culturable (VBNC) state under unfavorable environmental conditions.

Diversity of legionellae strains from Tunisian hot spring water.

The aim of this study was to evaluate the frequency of Legionella pneumophila in three hot spring water recreation areas by conventional culture on GVPC and by Real Time-PCR. No legionellae were isolated from the spring water upstream the distribution system suggesting strongly that the thermal area was the probable source of these pathogens. L.

Involvement of minerals in adherence of Legionella pneumophila to surfaces.

Legionella pneumophila is the causative agent of 90 % of Legionnaires' disease cases. This bacterium lives naturally in fresh water and can colonize biofilms, which play an important role in the protection of Legionella against environmental stress factors. Relationship between the presence of minerals in water and Legionella adherence to surfaces is not well-known.

Effects of disinfection on Legionella spp., eukarya, and biofilms in a hot water system.

Legionella species are frequently detected in hot water systems, attached to the surface as a biofilm. In this work, the dynamics of Legionella spp. and diverse bacteria and eukarya associated together in the biofilm, coming from a pilot scale 1 system simulating a real hot water system, were investigated throughout 6 months after two successive heat shock treatments followed by three successive chemical treatments.

Detection of free-living amoebae by using multiplex quantitative PCR.

Free-living amoebae (FLA) are protozoa found worldwide in soil and aquatic environments, which are able to colonize man-made water networks. Some FLA have the potential to be pathogenic and others might harbour pathogenic bacteria. Indeed, FLA feed on bacteria, but some bacteria could resist phagocytosis and either survive in FLA or even multiply within FLA.

Chemical disinfection of Legionella in hot water systems biofilm: a pilot-scale 1 study.

Legionella bacteria encounter optimum growing conditions in hot water systems and cooling towers. A pilot-scale 1 unit was built in order to study the biofilm disinfection. It consisted of two identical loops, one used as a control and the other as a 'Test Loop'.

Passage through Tetrahymena tropicalis enhances the resistance to stress and the infectivity of Legionella pneumophila.

Legionella pneumophila is a gram-negative bacterium prevalent in fresh water which accidentally infects humans and is responsible for the disease called legionellosis. Intracellular growth of L. pneumophila in Tetrahymena is inconsistent; in the species Tetrahymena tropicalis stationary-phase forms (SPFs) of L.

Long-term survival of Legionella pneumophila in the viable but nonculturable state after monochloramine treatment.

Legionella pneumophila, a facultative intracellular human pathogen, can persist for long periods in natural and artificial aquatic environments. Eradication of this bacterium from plumbing systems is often difficult. We tested L.

Development of a real-time PCR assay for quantification of Acanthamoeba trophozoites and cysts.

Free-living amoebae have been found to be a reservoir for various pathogenic bacteria in aquatic environments. For example, the Acanthamoeba genus renders possible the intracellular multiplication of Legionella pneumophila, which is responsible for legionellosis. It consequently matters to quantify Acanthamoeba cells and thereby enhance our assessment of the risk of contamination.

Armadillidin: a novel glycine-rich antibacterial peptide directed against gram-positive bacteria in the woodlouse Armadillidium vulgare (Terrestrial Isopod, Crustacean).

We report the isolation and the characterization of a novel antibacterial peptide from hemocytes of the woodlouse Armadillidium vulgare, naturally infected or uninfected by Wolbachia, an intracellular Gram-negative bacterium. This molecule displays antibacterial activity against Gram-positive bacteria despite its composition which classes it into the glycine-rich antibacterial peptide family, usually directed against fungi and Gram-negative bacteria. The complete sequence was determined by a combination of Edman degradation, mass spectrometry and cDNA cloning using a hemocyte library.

Influence of amino acid substitutions in the leader peptide on maturation and secretion of mesentericin Y105 by Leuconostoc mesenteroides.

By site-specific mutagenesis, the hydrophobic conserved amino acids and the C-terminal GG doublet of the leader peptide of pre-mesentericin Y105 were demonstrated to be critical for optimal secretion of mesentericin Y105, as well as for the maturation of the pre-bacteriocin by the protease portion of the ABC transporter MesD.

Mutational analysis of mesentericin y105, an anti-Listeria bacteriocin, for determination of impact on bactericidal activity, in vitro secondary structure, and membrane interaction.

Mesentericin Y105 is a 37-residue bacteriocin produced by Leuconostoc mesenteroides Y105 that displays antagonistic activity against gram-positive bacteria such as Enterococcus faecalis and Listeria monocytogenes. It is closely related to leucocin A, an antimicrobial peptide containing beta-sheet and alpha-helical structures. To analyze structure-function relationships and the mode of action of this bacteriocin, we generated a collection of mesentericin derivatives.

Differences in mesentericin secretion systems from two Leuconostoc strains.

Leuconostoc mesenteroides Y105 and L. mesenteroides FR52 produce both mesentericin Y105 and B105, in equal amounts. The mesentericin operons of L.

Heterologous expression of bacteriocins using the mesentericin Y105 dedicated transport system by Leuconostoc mesenteroides.

Mesentericin Y105 (MesY105) is a class IIa anti-Listeria bacteriocin, produced by Leuconostoc (Ln.) mesenteroides Y105 and with potential food grade application. This bacterium produces a second bacteriocin, mesentericin B105 (MesB105), that does not belong to the same class.

Analysis of sigma(54)-dependent genes in Enterococcus faecalis: a mannose PTS permease (EII(Man)) is involved in sensitivity to a bacteriocin, mesentericin Y105.

The sigma(54) RNA polymerase subunit has a prominent role in susceptibility of Listeria monocytogenes and Enterococcus faecalis to mesentericin Y105, a class IIa bacteriocin. Consequently, sigma(54)-dependent genes as well as specific activators also required for expression of these genes were sought. Five putative sigma(54)-associated activators were detected in the genome of E.