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Background and Objectives: Adhesion of microorganisms on facemask surfaces is a major problem that produces contam- ination of the mask wearer either by inhalation or by direct contact. Generally, physicochemical properties of the material and the microorganism are responsible for this adhesion and are also reported to influence the filtration efficiency of face- masks. However, theses surface proprieties and their effect on particles attachment on facemask materials remain poorly documented. The purpose of this study was to investigate the physicochemical properties of seven facemasks and evaluate the influence of these characteristics on the adhesion of Sataphylococcus aureus. Materials and Methods: Physicochemical properties is done by contact angle method and scanning electron microscopy while theoretical adhesion of S. aureus is done according to XDLVO approach. Results: The obtained results showed that all masks have a hydrophobic character. The electron donor and electron acceptor parameters change depending on each mask. Chemical analysis demonstrates the presence of two chemical elements (car- bon and oxygen). Predictive adhesion demonstrate that S. aureus has an attractive behavior towards the masks used but the potential of adhesion is not the same. Conclusion: Such information is valuable to understand attachment of biological particles and to contribute in the inhibition of this attachment.

Biofilm formation and microbial adhesion are two related and complex phenomena. These phenomena are known to play an important role in microbial life and various functions with positive and negative aspects. Actinobacteria have wide distribution in aquatic and terrestrial ecosystems. This phylum is very large and diverse and contains two important genera Streptomyces and Mycobacteria. The genus Streptomyces is the most biotechnologically important, while the genus Mycobacteria contains the pathogenic species of Mycobacteriaceae. According to the literature, the majority of studies carried out on actinomycetes are focused on the detection of new molecules. Despite the well-known diversity and metabolic activities, less attention has been paid to this phylum. Research on adhesion and biofilm formation is not well developed. In the present review, an attempt has been made to review the literature available on the different aspects on biofilm formation and adhesion of Actinobacteria. We focus especially on the genus Streptomyces. Furthermore, a brief overview about the molecules and structures involved in the adhesion phenomenon in the most relevant genus is summarized. We mention the mechanisms of quorum sensing and quorum quenching because of their direct association with biofilm formation.

Streptomyces has many advantages for exploration in biotechnological applications because of their ability to elaborate a multitude of bioactive molecules and secondary metabolites. Despite the importance of this genus in biotechnology, biofilm formation in Streptomyces is under-investigated. The objective of this research is to adapt two assays for the assessment of biofilm formation in Streptomyces. In the present investigation, we assess and follow biofilm formation in eight Streptomyces strains using quantitative and qualitative methods. The quantitative study based on a staining of the retained biomass in the microtiter plate with crystal violet “5%” and destaining using ethanol/acetone mixture, the concentration of crystal violet in the alcoholic solution reflect the intensity of the attached biofilm. On the other hand, the qualitative one consists of using modified freeman’s method a modified congo red agar method based on the color of colonies. Quantification of biomass by crystal violet staining method confirmed that Streptomyces bellus A43 and Streptomyces bellus A61 are biofilm-forming and this ability increase with the period of incubation. Our results showed that sixStreptomyces strains arenon-slime producing/non-biofilm forming. Two Streptomyces strains are slime producing/biofilm forming; this character vanishes at five days. Further research on genes responsible for biofilm formation in Streptomyces is highly recommended for better understanding of the phenomenon.

The corona virus pandemic at the international and national levels constitutes a real problem for health, economy, trade and certainly education. In Morocco, general confinement, since March 20, 2020, is an obligation to limit the spread of this virus. The Ministry of National Education decided to close education and training institutions on March 16, 2020. It adopted, in parallel, several proactive and preventive measures to deal with this pandemic on several levels, including distance education. Certainly these measures taken in the field of education are highly important, but require reinforcement for a continuous improvement of the safety and health of learners and the professional body. Continuous prevention measures are proposed in this study, acting on legal, human resources and educational content aspects, as well as on the preventive aspect on which we offer simplified methods and tools for the effective management of COVID-19 risk. In particular, we propose a checklist, adapted to the school context, used to carry out periodic internal audits for regular control and monitoring of the health situation in the school institution and the implementation of corrective and preventive actions.

The choice of the best support for microbial adhesion can improve the start-up speed and efficiency of dairy wastewater treatment by biofilm bioreactors. In this study, three substrates were tested: PP (polypropylene), PET (Polyethylene terephthalate), and PVC (polyvinyl chloride). By using the contact angle method, the surface physicochemical characteristics of the bacterium, inert substrates, and substrates after dairy wastewater (DWW) conditioning film were measured to understand its impact on adhesion as well as the most suitable material to optimize bacterial adhesion. DWW conditioning film affects the physicochemical characteristics of plastic supports and improves the initial adhesion of bacteria to substrates. Results of initial adhesion tests for untreated and treated supports showed differences in how bacterial cells adhered to substrates. Before treatment, PVC and then PP showed a significant adhesion capacity, double that of PET. After modifying by DWW, initial bacterial adhesion increased by 106 (105 to 1011 CFU/cm2) and PVC demonstrated the highest adhesion capacity, followed by PP and finally PET. Therefore, before the modification of the supports by DWW, PP and PVC are in the same rank for the initial bacterial adhesion and after the modification, PVC seems to be the best for initial bacterial adhesion.

Premise plumbing promotes the regrowth and survival of opportunistic pathogens, such as Legionella pneumophila (L. pneumophila), especially within biofilms. The purpose of this study was to investigate the effectiveness of chlorine disinfection against L. pneumophila serogroup 1 and serogroup 2–15 planktonic form and biofilms. Planktonic cells were able to survive during the study period in the presence of chlorine at recommended free chlorine levels (0.2–0.5 mg/L). Biofilms were developed on galvanized steel and polyvinyl chloride (PVC) for 18 and 30 days and exposed to 50, 100, 150, and 200 mg/L for 2 hours. No colony appeared immediately after chlorination; however, persistent cells were able to tolerate treatment and continue to grow on subsequent days. The biofilm formation was evaluated by atomic force microscopy. This study demonstrates that the biofilm formed on the surfaces of plumbing materials increases bacterial resistance against high levels of chlorination. A new approach towards monitoring and eradicating L. pneumophila from water systems is required.

Objective: Legionella is a waterborne pathogen that causes a severe form of pneumonia called Legionnaires' diseases, which is normally acquired by inhalation of aerosols containing Legionella origi...

Classification is a crucial stage in the processing of satellite images that influence considerably the quality of the result. A variety of methods is proposed in the literature for the purposes of image classification. They present many differences in their basic principles, thus in the quality of the results obtained. Therefore, a study of different classification methods seems to be essential. The classification of satellite images with conventional methods can be done in several ways using different algorithms. These algorithms can be divided into two main categories: supervised and non-supervised. Decision tree on the contrary is a machine learning tool. It is a plain model characterized by the simplicity of understanding and interpretation. This work aims firstly, to classify a high resolution Quickbird satellite image of an urban area by the decision tree method and compare it with the conventional classification algorithms in order to evaluate its efficiency. The methodology consists of two main stages: classification and evaluation of results. The second is based on the calculation of a number of statistical indices derived from the confusion matrix: the statistical parameter “kappa’ and the overall coefficient of precision.

Background and Objectives: Legionnaires’ disease continues to be a public health concern. Colonized water distribution systems are often implicated in Legionella transmission, despite the use of various disinfection strategies, the bacterium is capable to persist and survive in water systems. The aim of this study was to investigate the persistence of Legionella pneumophila to sodium chloride over time at different temperatures and analysing the role of biofilms in the survival of this bacteria. Materials and Methods: L. pneumophila serogroup 1 and L. pneumophila serogroup 2-15 were used to study the effect of sodium chloride on planktonic and sessile cells. The tested concentrations were: 0.5%, 1%, 2%, 3%, 4%, 6% and 8% (W/V) NaCl. Biofilms were grown on 24-well microplates. Results: At 20°C, L. pneumophila planktonic cells were able to survive in sodium chloride concentrations up to 2%. How- ever, at 37°C, a sodium chloride concentration over 1.5%, reduced systematically the numbers of bacterial cells. Biofilms were grown for 20 days in the absence and presence of sodium chloride. The results show that bacterial strains were able to survive and regrow after the sodium chloride shock (2-3%). Moreover, it seems that this effect is less expressed with the age of the biofilm; old biofilms were more persistent than the young ones. Conclusion: Results from this study demonstrate that the sodium chloride disinfection strategy was effective on Legionella pneumophila planktonic cells but not on biofilms, which demonstrate the role of biofilms in the persistence and recoloniza- tion of L. pneumophila in water distribution systems.

The biofilm formation on equipment surfaces in dairy manufacturing is a major concern for industry and consumers alike, which may affect the safety and quality of dairy products. In order to identify the bio-contamination risk of materials commonly used in dairy manufacturing, adhesion of Staphylococcus aureus on glass coated by two kinds of UHT milk (whole milk and skimmed milk) was investigated. It is known that adhesion is mainly governed by surface physicochemical properties, for that, the effect of milk components on physicochemical properties of glass and bacterial surfaces were exanimated through contact angle measurements. MATLAB software was used to evaluate the ability of S. aureus adhesion on glass. The hydrophobic quantitative and electron acceptor characteristics of the glass appear to increase with the presence of fat in milk, while its electron donor property decreases with this component. The percentage of occupied surface of untreated glass was more important than in treated surfaces for 50% of the strains studied. As well, the percentage of occupied surface by bacterial strains in untreated glass by skimmed milk is generally more important compared to the whole milk. Therefore, the risk of bio-contamination of untreated glass is more favorable for bacteria cultured in skimmed milk compared to these in whole milk but the bio-contamination risk on covered glass by milk is not milk dependent and is strain dependent.

To improve the start-up speed and efficiency of bioreactors, biofilm technology is sometimes used. This technology uses various types of materials to facilitate the adhesion of microorganisms. In this study, the surface characteristics of inert substrates and substrates after olive oil-mill wastewater (OMWW) conditioning film were evaluated to understand the impact of OMWW on adhesion as well as the most suitable material to optimize bacterial adhesion. Three common substrates made of different polymers were tested for bacterial adhesion before and after treatment with OMWW: PP (polypropylene), PET (Polyethylene terephthalate), and PVC (polyvinyl chloride). The surfaces’ physicochemical characteristics were studied by measuring the contact angle for the studied bacteria strain and the supports, before and after treatment with OMWW. Results of initial adhesion tests for untreated and treated supports showed differences in how bacterial cells adhered to substrates. Before treatment with OMWW, PVC and then PP showed a significant adhesion capacity, double that of PET [PVC: 1.58 × 105 CFU/cm2, PP: 1.48 × 105 CFU/cm2 and PET: 0.72 × 105 CFU/cm2]. After treatment with OMWW, initial bacterial adhesion increased by 106 (from 105 CFU/cm2 for untreated supports to 1011 CFU/cm2 for treated supports), and PET followed by PP demonstrated the highest adhesion capacity, 2 and 1.7 times more than PVC, respectively [PET: 1.39 × 1011 CFU/cm2, PP: 1.15 × 1011 CFU/cm2 and PVC: 0.67 × 1011 CFU/cm2]. OMWW conditioning film affects the physicochemical characteristics of plastic supports, especially the donor electron character, and improves the initial adhesion of bacteria to substrates (105 to 1011 CFU/cm2). Therefore, surfaces’ physicochemical characteristics were important in the initial adhesion of the bacteria onto the support before and after treatment.

The main aim of this work was to determine the most appropriate materials for the installation of a water system according to the characteristics of the water that passes through it. To this end, we conducted an investigation of the effect of two types of water (SDW: sterile distilled water and STW: sterile tap water) on the properties of bacterial surfaces and the theoretical adhesion of two bacteria (Pseudomonas aeruginosa and Escherichia coli) on six plumbing materials. Contact angle measurements were used to determine the surface energies of bacteria and materials. XDLVO theory was used to estimate the interactions between bacteria and plumbing materials. The results showed that water had a clear impact on the electron donor character and the hydrophobicity of the bacterial surfaces. Also, the predictive adhesion showed that all tested materials could be colonized by P. aeruginosa and E. coli ([Formula: see text]

Biofilms are increasingly identified as the source of major industrial, societal and public health problems. The aim of the present paper is to evaluate the risk of contamination of medical surfaces by pathogenic strains. For this purpose, a theoretically estimation of the ability of four pathogenic strains in the medical field: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella Kentucky to adhere to the surface of four different substrata: Glass, polystyrene (PS), polyethylene (PE) and Stainless Steel 316L (Inox), was studied according to the thermodynamic approach. In order to modify the surface tension of these supports, they were treated with surfactants. The contact angle method was used to estimate the physicochemical properties of the two matrices. According to the results of the total free energy of interactions, the adhesion of these four strains on the treated and untreated glass was not favorable. For the other supports (PE, PS, and inox), the adhesion of the strains was favorable but after the treatment of the supports with surfactants, it appears that the attachment of the cells became unfavorable.

We aimed to investigate the adhesion of Legionella pneumophila serogroup1 and L. pneumophila serogroup2-15 on glass, galvanized steel, stainless steel, copper, Polyvinyl chloride(PVC), Cross-linked polyethylene(PEX-c) and Polypropylene Random Copolymer(PPR). The surface physicochemical properties of both bacterial cells and materials were estimated through contact angle measurements. The roughness and surface topography of the materials were evaluated by Atomic Force Microscopy. The two L. pneumophila serogroups and plumbing materials showed a hydrophobic character, while glass surface was hydrophilic. All strains were adhered to all materials with the exception of copper. The result showed that the adhesion of both L. pneumophila sg1 and sg2-15 was systematically expressed with high intensity on galvanized steel followed by PVC, PEX-c, PPR, stainless steel and the low intensity on glass. The extent of adhesion is in correlation with the surface roughness and acid-bases interactions, while hydrophobicity seems to have no effect in adhesion intensity.

The purpose of our study was to investigate the biofilm formation by Legionella pneumophila serogroup1 and serogroup2-15 on plumbing materials mostly used in building water systems in Morocco. The ...

Bacterial proliferation in the form of biofilm fixed on a substrate is the result of a set of physical, chemical and biological processes. Microbial adhesion to a substrate is often considered to be the result of physicochemical interactions between the substrate and the microbial cells. These interactions include electrostatic interactions, Van der Waals interactions and acid-base interactions (electron donor - electron acceptor). The exact role of these physicochemical properties is still poorly documented. The purpose of this work is to provide some clarifications on this subject. The phenomenon of adhesion is often studied on clean surfaces, whereas in reality, it is always conditioned depending on its environment (medical, food or cosmetic). This is why in the present work we treated two different surfaces: glass and polyethylene, with diverse surfactants: nonionic, anionic and cationic. The choice of surfactants was motivated by its wide application in different fields. The physicochemical properties of the two substrata (treated and untreated) were defined using contact angle measurements. Moreover, the adhesive behavior of Staphylococcus aureus, as a bacterial model, on the studied substratum was assessed. The obtained results indicate that the physicochemical parameters of the two supports have changed in a specific way to each surfactant. The non-ionic surfactant turned both the surfaces more hydrophilic. However, the anionic and cationic surfactants have reversed the physicochemical characteristics of the surfaces. The correlation coefficients of the physicochemical properties and the adhesive behavior show that there is an association between the wettability of the two surfaces and the rate of the adherent cells.

This study aims to understand the relationship between capabilities of Escherichia coli strains to form biofilm and serotype groups expressed on cell surface. Sixteen strains of E. coli were originally isolated from different food processing lines in different Moroccan cities. Strains serotyped based on their O (somatic), H (flagellar), and K (capsular) surface antigen profiles using different antiserums. Biofilm assays carried out in 96-well microtiter dishes using the method of O’Toole et al. Our results show that no clear relation observed between origin and serotype groups. In the other hand, we observed that not all studied strains were able to form biofilm. Furthermore, combination of antigens H40 and K11 appears to be involved in biofilm formation. In fact, the H antigen seems to be implicated in the placement of the bacterial cells near the surface and the K antigen may play a role in physicochemical interactions between bacteria and inert surface.

The surface energy characteristics of uncoated (clean) and coated stainless steel with UHT milk at various contact time (5 min, 30 min, 1 hours, 3 hours, 6 hours, 24 hours) were determined using contact angle measurement. Whatever the contact time, the clean stainless steel coupons became more hydrophobic and more electron acceptor when they are coated by milk. Inversely, the electron donor character seems to decreasing in this condition. The calculated surface energy component of coated stainless steel was found to vary with contact time. Its hydrophobicity and its electron acceptor were minimal after 3 hours of contact, but its electron donor was minimal after 1 hours of contact. Adhesion experiments of Staphylococcus aureus were carried out on uncoated and coated stainless steels at various contact times. For all contact times, the adhesion results show that milk reduce S. aureus adhesion, and the level of this reduction depend on contact time. This reduction was lower and higher after 1 hours, 5 min and 30 min of contact respectively.

A simple and rapid method, Microbial adhesion to hexadecane, for estimating the cell surface charge is proposed. This method is based on the determination of cell affinity to hexadecane at low ionic strength and at high ionic strength. The difference between these two affinities can provide the relative cell surface charge. The application of this method for Staphylococcus aureus and Escherichia coli show that the profile of surface charge evolution as a function of pH was similar to these obtained by microelectrophoresis method.