Jean-Marc Berjeaud

The antibacterial activity of Magainin I immobilized onto mixed thiols Self-Assembled Monolayers

An antibacterial peptide, Magainin I, was covalently bound to a mixed 11-mercaptoundecanoïc acid (MUA) and 6-mercaptohexanol (C6OH) (ratio 1:3) Self-Assembled Monolayer (SAM) on gold surfaces. Each step of the surface functionalization was characterized by Polarization Modulation Reflection Absorption InfraRed Spectroscopy (PM-RAIRS) and X-ray Photoelectron Spectroscopy (XPS). The antibacterial activity of the anchored Magainin was tested against three Gram-positive bacteria (Listeria ivanovii, Enterococcus faecalis and Staphylococcus aureus), and the results revealed that the adsorbed Magainin I reduced by more than 50% the adhesion of bacteria at the surface, together with the killing of the bacteria that nonetheless adhered to the surface. No release of the peptide was observed upon contact with the bacterial suspension; the activity has proven to be persistent overtime, up to six months after the first use.

In vitro activity of terpenes against Candida biofilms

The antibiofilm activity of 10 terpenes was tested in vitro against three Candida species by 24-h treatment of biofilms aged 1-5 days. Treatment of 24-h-old Candida albicans biofilms with carvacrol, geraniol or thymol (0.06%) resulted in >80% inhibition. Carvacrol (0.03%) inhibition was > or =75% independent of the age of the C. albicans biofilm. Carvacrol (0.125%) inhibition was >75% against Candida glabrata and Candida parapsilosis biofilms. Geraniol (> or =0.125%) and thymol (0.06% or 0.125%) inhibition was >75% against C. parapsilosis biofilms whatever their age. This study demonstrates the antibiofilm activity of terpenes and points out the exceptional efficiency of carvacrol, geraniol and thymol, which could represent candidates in the treatment of candidiasis associated with medical devices.

Method for Rapid Purification of Class IIa Bacteriocins and Comparison of Their Activities

ABSTRACT A three-step method was developed for the purification of mesentericin Y105 (60% yield) from the culture supernatant ofLeuconostoc mesenteroides Y105. The same procedure was successfully applied to the purification of five other anti-Listeria bacteriocins identified by mass spectrometry. Specific activities of the purified bacteriocins were compared.

δ-hemolysin, an update on a membrane-interacting peptide

delta-hemolysin is a hemolytic peptide produced by Staphylococcus, and it has been studied for nearly 50 years. Therefore, it has become a model in the study of peptides interacting with membranes. In this review, we report some recent findings and compare them with previous works. delta-hemolysin is a 26 amino acid peptide, somewhat hydrophobic and presenting a zero net charge. Study of its structure has shown that delta-hemolysin is alpha-helical and amphipathic, such as many antimicrobial peptides (e.g. magainin and melittin). However, delta-hemolysin had not displayed any reported antimicrobial activity until a recent publication showed its high potency against Legionella. Its mode of action is based on direct interaction with target membranes. In accordance with its concentration, delta-hemolysin may slightly perturb a membrane or lead to cell lysis. Peptide charge plays an important role in its interaction with membranes, as is shown in the study of peptide variants. Some positively charged variants become highly hemolytic and even active against Escherichia coli and Staphylococcus aureus. Finally, it has recently been demonstrated that peptide preferentially binds to lipid-disordered domains. It has been postulated that as a result, enrichment in lipid-ordered domains might increase peptide concentration in lipid-disordered domains and thereby improve its activity.

Sakacin G, a New Type of Antilisterial Bacteriocin

ABSTRACT Sakacin G is a 37-amino-acid-residue-long class IIa bacteriocin produced by Lactobacillus sake 2512, which is encoded by the duplicated structural genes skgA1 and skgA2. Sakacin G appears to be unique and seems to be an intermediate between pediocin-like bacteriocins, according to its double-disulfide bridges required for antimicrobial activity, and mesentericin-like bacteriocins in terms of sequence homologies, inhibition spectrum, and specific activity.

Optimized grafting of antimicrobial peptides on stainless steel surface and biofilm resistance tests

Antibacterial peptides, magainin I and nisin were covalently bound to stainless steel surfaces. Several procedures of surface functionalisation processes have been investigated and optimized, each step being characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and X-ray photoemission spectroscopy (XPS). Grafting of antibacterial peptides was successfully achieved by a 3 steps functionalisation process on a chitosan polymeric layer. The antibacterial activity of the anchored magainin and nisin was tested against a gram-positive bacteria, Listeria ivanovii, i.e., the possible survival and attachment of this bacteria, was characterized on modified stainless steel surfaces. The results revealed that the adsorbed peptides reduced the adhesion of bacteria on the functionalised stainless steel surface.

Co-grafting of amino-poly(ethylene glycol) and Magainin I on a TiO2 surface: tests of antifouling and antibacterial activities.

An antimicrobial peptide, Magainin I (Mag), was grafted to a titanium oxide surface, via an antiadhesive poly(ethylene glycol) (PEG) cross-linker. The latter plays a 2-fold part, being antiadhesive, and enabling the covalent immobilization of the peptide. The functionalization was characterized at each step by reflection absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The antiadhesive properties of PEG, and antibacterial activity of the anchored Magainin I, were individually tested toward adsorption of bovin serum albumin (BSA) proteins, and against Gram positive bacteria, Listeria ivanovii , respectively. The results reveal that adhesion of both proteins and bacteria have been considerably reduced, accompanied by an inhibition of the growth of remaining adhered bacteria. This work thus offers a novel approach to functionalize oxide surfaces against biofilms and to measure the so-obtained properties in each of the successive steps of a biofilm formation.

Possible role of azole and echinocandin lock solutions in the control of Candida biofilms associated with silicone

Until now, management of candidiasis related to implanted devices has remained problematic. The aim of this study was to investigate antifungal lock strategies against Candida albicans and Candida glabrata biofilms in vitro. Three antifungal agents were used against eight C. albicans and six C. glabrata clinical strains isolated from infected catheters. Caspofungin and micafungin, both echinocandins, as well as the azole posaconazole were tested. An in vitro model of Candida biofilm on 100% silicone catheters was used. Efficacy of the antifungal lock was tested against biofilms aged 12h and 5 days following exposure to caspofungin (5mg/L and 25mg/L), micafungin (5mg/L and 15 mg/L) and posaconazole (10mg/L) for 12h. Persistence of antibiofilm activity was investigated 1-3 days following drug elimination. Antifungal lock was considered effective in the event of a significant decrease (P<0.001) in the metabolic activity of the biofilm yeast. The results showed that micafungin had significant inhibitory effectiveness against young and mature C. albicans and C. glabrata biofilms. Moreover, this activity appeared to persist for up to 3 days. Caspofungin displayed similar activity against all C. albicans biofilms, but the activity was less persistent for C. glabrata biofilms. Posaconazole was less effective against C. albicans biofilms, but its activity was sustained. Echinocandin lock therapy could significantly enhance the management of candidiasis in patients with indwelling catheters by combating biofilms and enabling device maintenance in situ.

Mutational Analysis of Mesentericin Y105, an Anti-Listeria Bacteriocin, for Determination of Impact on Bactericidal Activity, In Vitro Secondary Structure, and Membrane Interaction

ABSTRACT 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 β-sheet and α-helical structures. To analyze structure-function relationships and the mode of action of this bacteriocin, we generated a collection of mesentericin derivatives. Mutations were obtained mostly by PCR random mutagenesis, and the peptides were produced by an original system of heterologous expression recently described (D. Morisset and J. Frère, Biochimie 84:569-576, 2002). Ten derivatives were obtained displaying modifications at eight different positions in the mesentericin Y105 sequence. Purified peptides were incorporated into lysophosphatidylcholine micelles and analyzed by circular dichroism. The α-helical contents of these peptides were compared and related to their respective bactericidal activities. Moreover, studies of the intrinsic fluorescence of tryptophan residues naturally occurring at positions 18 and 37 revealed information about insertion of the peptides in micelles. A model for the mode of action of mesentericin Y105 and related bacteriocins is proposed.

Synthesis and Antitumor Efficacy of a β-Glucuronidase-Responsive Albumin-Binding Prodrug of Doxorubicin

In this paper we describe the synthesis and biological evaluation of the first β-glucuronidase-responsive albumin-binding prodrug designed for the selective delivery of doxorubicin at the tumor site. This prodrug leads to superior antitumor efficacy in mice compared to HMR 1826, a well-known glucuronide prodrug of doxorubicin that cannot bind covalently to circulating albumin. Furthermore, this compound inhibits tumor growth in a manner similar to that of doxorubicin while avoiding side effects induced by the free drug.