Protocol for the assessment of viral retention capability of membranes

A series of experiments has been carried out to determine the Log removal value (LRV) of MS2 bacteriophages suspended in various buffers (osmosed water, tap water, aqueous solutions of NaCl and phosphate buffer solution) during filtration through hollow fiber membranes made of cellulose acetate. Viral concentrations in permeate and retentate were determined using two different methods, namely plaque forming unit (PFU) counting, which reveals only infectious particles and quantitative RT-PCR which detects the total (infectious + inactivated) number of viral genomes regardless of their infectivity.From this experimental study, we propose guidelines for preparing the challenging solutions and measuring their concentration which ensure a reliable assessment of the membrane performance

Synthesis,antimicrobial activity and physico-chemical properties of some n-alkyldimethylbenzylammonium halides

Quaternary ammonium salts (chloride, bromide and iodide; QUATs) with n-alkyl chain lengths between C8 and C18 have been synthesized under optimized experimental conditions. These compounds were tested in vitro for antimicrobial activity against representative bacterial strains (Staphylococcus aureus CIP 4.83, Enterococcus hirae CIP 5855, Pseudomonas aeruginosa CIP 82118, Escherichia coli CIP 53126, Mycobacterium smegmatis CIP 7326) and fungal species (Aspergillus niger ATCC 16404, Candida albicans IP 118079, Trichophyton interdigitale IP 146583). While these compounds showed moderate antifungal activity, several of them (particularly C14-I−) may be considered as highly potential antibacterial agents against S. aureus, E. hirae and E. coli with MIC values lower than that of commercial benzalkonium chloride and ciprofloxacin used as standards. The relationship between the lipophilicity and the antibacterial activity of the tested QUATs was quantified by a multiple linear regression method

Preventive effects of an original combination of grape seed polyphenols with amine fluoride on dental biofilm formation and oxidative damage by oral bacteria

To investigate the preventive effects of an original combination of a grape seed extract (GSE) with an amine fluoride (Fluorinol(®) ) on dental plaque formation and oxidative damage caused by oral bacteria. METHODS AND RESULTS: The antibacterial activity of the compounds was assessed using the broth macrodilution method, and their antiplaque activity was evaluated on a multispecies biofilm grown on saliva-coated hydroxyapatite discs. The effect on glucosyltransferases activity was analysed through reductions in the overall reaction and the quantity of insoluble glucan synthesized. The combination of 2000 μg ml(-1) of GSE with 10·2 mg ml(-1) of Fluorinol(®) significantly decreased the biofilm formation (up to 4·76 log10 of reduction) and inhibited by 97·4% the insoluble glucan synthesis by glucosyltransferases. The antioxidant activity of this combination, alone or incorporated into a formulated mouthwash (Eludril daily(®) ), was determined using the Trolox equivalent antioxidant capacity assay (TEAC), and both showed significantly greater antioxidant capacity than vitamin C. CONCLUSIONS : The GSE/Fluorinol(®) combination showed both a significant antiplaque activity and an important antioxidant capacity in vitro, without any bactericidal effects. SIGNIFICANCE AND IMPACT OF THE STUDY: This is, to our knowledge, the first report on the properties of an original combination of a polyphenolic extract with amine fluoride that could be used for the prevention of oral diseases and oxidative damage associated

Impairment of Pseudomonas aeruginosa Biofilm Resistance to Antibiotics by Combining the Drugs with a New Quorum-Sensing Inhibitor.

Pseudomonas aeruginosa plays an important role in chronic lung infections among patients with cystic fibrosis (CF) through its ability to form antibiotic-resistant biofilms. In P. aeruginosa, biofilm development and the production of several virulence factors are mainly regulated by the rhl and las quorum-sensing (QS) systems, which are controlled by two N-acyl-homoserine lactone signal molecules. In a previous study, we discovered an original QS inhibitor, N-(2-pyrimidyl)butanamide, called C11, based on the structure of C4-homoserine lactone, and found that it is able to significantly inhibit P. aeruginosa biofilm formation. However, recent data indicate that P. aeruginosa grows under anaerobic conditions and forms biofilms in the lungs of CF patients that are denser and more robust than those formed under aerobic conditions. Our confocal microscopy observations of P. aeruginosa biofilms developed under aerobic and anaerobic conditions confirmed that the biofilms formed under these two conditions have radically different architectures. C11 showed significant dose-dependent antibiofilm activity on biofilms grown under both aerobic and anaerobic conditions, with a greater inhibitory effect being seen under conditions of anaerobiosis. Gene expression analyses performed by quantitative reverse transcriptase PCR showed that C11 led to the significant downregulation of rhl QS regulatory genes but also to the downregulation of both las QS regulatory genes and QS system-regulated virulence genes, rhlA and lasB. Furthermore, the activity of C11 in combination with antibiotics against P. aeruginosa biofilms was tested, and synergistic antibiofilm activity between C11 and ciprofloxacin, tobramycin, and colistin was obtained under both aerobic and anaerobic conditions. This study demonstrates that C11 may increase the efficacy of treatments for P. aeruginosa infections by increasing the susceptibility of biofilms to antibiotics and by attenuating the pathogenicity of the bacterium

Antimicrobial activity of metal oxide microspheres: an innovative process for homogeneous incorporation into materials

AIMS:To investigate the potent control of microbial surface contamination of an innovative process which consists in incorporating metal oxide microspheres homogeneously into materials. Spherical microspheres containing zinc and magnesium oxides synthesized via a one-step manufacturing process (Pyrolyse Pulvérisée® ) and incorporated into different plastic matrices were evaluated for their antimicrobial activity according to JIS Z 2801 standard. A significant activity was observed for microsphere-added polyethylene coupons with a reduction of all tested bacteria populations, including Gram negative and Gram positive even expressing acquired antibiotic resistance (Escherichia coli ESBL, Staphylococcus aureus metiR). An antiviral activity higher than 2 log of reduction was also observed on H1N1 and HSV-1 viruses. This antimicrobial effect was dose-dependent and time-dependent for both polyethylene and polypropylene matrices. Antimicrobial activity was maintained after exposition to disinfectants and totally preserved 50 months after the preparation of the coupons. CONCLUSIONS:Incorporated into plastic matrices, metal oxide microspheres showed significant antibacterial and antiviral activities. SIGNIFICANCE AND IMPACT OF STUDY: This is, to our knowledge, the first report on an original process incorporating metal oxide microspheres, which have specific physico-chemical and antimicrobial properties, into materials that could be used for surface contamination prevention

Insights into cystic fibrosis polymicrobial consortia: the role of species interactions in biofilm development, phenotype, and response to in-use antibiotics

The Supplementary Material for this article can be found online at: http://journal.frontiersin.org/article/10.3389/fmicb. 2016.02146/full#supplementary-materialCystic Fibrosis (CF) airways disease involves complex polymicrobial infections where different bacterial species can interact and influence each other and/or even interfere with the whole community. To gain insights into the role that interactions between Pseudomonas aeruginosa in co-culture with Staphylococcus aureus, Inquilinus limosus,and Stenotrophomonas maltophilia may play in infection, the reciprocal effect during biofilm formation and the response of dual biofilms toward ciprofloxacin under in vitro atmospheres with different oxygen availabilities were evaluated. Biofilm formation kinetics showed that the growth of S. aureus, I. limosus, and S. maltophilia was disturbed in the presence of P. aeruginosa, under both aerobic and anaerobic environments. On the other hand, under aerobic conditions, I. limosus led to a decrease in biofilm mass production by P. aeruginosa, although biofilm-cells viability remains unaltered. The interaction between S. maltophilia and P. aeruginosa positively influenced dual biofilm development by increasing its biomass. Compared with monocultures, biomass of P. aeruginosaC S. aureus biofilms was significantly reduced by reciprocal interference. When grown in dual biofilms with P. aeruginosa, ciprofloxacin was less effective against S. aureus, I. limosus, and S. maltophilia, with increasing antibiotic doses leading to drastic inhibitions of P. aeruginosa cultivability. Therefore, P. aeruginosa might be responsible for the protection of the whole dual consortia against ciprofloxacin activity. Based on the overall data, it can be speculated that reciprocal interferences occur between the different bacterial species in CF lung, regardless the level of oxygen. The findings also suggest that alterations of bacterial behavior due to species interplay may be important for disease progression in CF infection.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT), under the scope of the strategic funding of UID/BIO/04469/2013 and COMPETE 2020 (POCI01-0145-FEDER-006684). This study was also supported by FCT and the European Community fund FEDER, through Program COMPETE, under the scope of the Projects RECI/BBBEBI/0179/2012 (FCOMP-01-0124-FEDER-027462), “BioHealth– Biotechnology and Bioengineering approaches to improve health quality”, Ref. NORTE-07-0124-FEDER-000027 and NORTE-070124-FEDER-000025 – RL2_ Environment & Health, co-funded by the Programa Operacional Regional do Norte (ON.2 – O NovoNorte), QREN, FEDER. The authors also acknowledge the grants of Susana P. Lopes (SFRH/BPD/95616/2013) and Andreia P.Magalhães (UMINHO/BD/25/2016)

Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation