Plant-derived bioactive compounds for the inhibition of biofilm formation: a comprehensive review.

Biofilm formation is a widespread phenomenon that impacts different fields, including the food industry, agriculture, health care and the environment. Accordingly, there is a serious need for new methods of managing the problem of biofilm formation. Natural products have historically been a rich source of varied compounds with a wide variety of biological functions, including antibiofilm agents. In this review, we critically highlight and discuss the recent progress in understanding the antibiofilm effects of several bioactive compounds isolated from different plants, and in elucidating the underlying mechanisms of action and the factors influencing their adhesion. The literature shows that bioactive compounds have promising antibiofilm potential against both Gram-negative and Gram-positive bacterial and fungal strains, via several mechanisms of action, such as suppressing the formation of the polymer matrix, limiting O2 consumption, inhibiting microbial DNA replication, decreasing hydrophobicity of cell surfaces and blocking the quorum sensing network. This antibiofilm activity is influenced by several environmental factors, such as nutritional cues, pH values, O2 availability and temperature. This review demonstrates that several bioactive compounds could mitigate the problem of biofilm production. However, toxicological assessment and pharmacokinetic investigations of these molecules are strongly required to validate their safety.

Chlorination of Pseudomonas aeruginosa in potable water.

The present study examined the effects of chlorine (NaOCl) disinfection on Pseudomonas aeruginosa in potable water. The adhesion of the bacteria on glass surfaces and the growth of the adherent cells were measured after treatment with chlorine (0, 0.25, 0.5, 0.75, and 1 mg/L). Adhesion was assessed by optical microscopy, and cultivability of the adherent cells was estimated by counting the bacteria on solid medium after being recovered from the support surface. Regardless of the concentration applied, P. aeruginosa did not lose the ability to adhere or grow after adhesion. However, the two factors were influenced by the chlorine treatments. The results showed that the adhesive capacity and cultivability of adherent cells were linked. The maximum inhibition of adherence and cultivability was observed in the 0.25 and 0.5 mg/L treatments. At 0.75 and 1 mg/L, the adhesive capability and post-adhesive cultivability were slightly increased. The results suggest that residual concentrations of sodium hypochlorite fixed by standards (less than 1 mg/L) may be ineffective against P. aeruginosa, and thus could have an impact on consumers.

Physicochemical characterization of reusable facemasks and theoretical adhesion by a challenged bacterium.

Background and Objectives: Adhesion of microorganisms on facemask surfaces is a major problem that produces contamination 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 facemasks. 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 (carbon 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.

Anti-adherence Activity of Monomicrobial and Polymicrobial Food-Derived Enterococcus spp. Biofilms Against Pathogenic Bacteria.

Enterococcus species are commensal organisms of the gastrointestinal tract and can also be isolated from traditional food products. They are used as probiotics in animals and less often in humans. This study aimed to investigate the antibacterial and anti-adhesive activities of twelve food-origin Enterococcus spp. biofilms on stainless steel AISI 316 L against foodborne pathogens, including Listeria monocytogenes CECT4032, Pseudomonas aeruginosa ATCC27853, and Escherichia coli ATCC25922. The antimicrobial and co-aggregation abilities of Enterococcus spp. were evaluated using spots-agar test and spectrophotometry aggregation assay, respectively. The anti-adhesive activity of selected strains on pathogenic bacteria was tested using serial dilution technique. Enterococci strains in planktonic mode showed strong inhibition activity against different pathogens tested with a significant difference in co-aggregation capacity. Moreover, L. monocytogenes and E. coli presented a low auto-aggregation rate compared to P. aeruginosa, which showed an amount of 11.25%. Scanning electron microscopy (SEM) revealed that biofilm biomass of Enterococcus spp. increased after 10 days. The thick layer of enterococci biofilms on AISI 316 L caused a low adhesion of L. monocytogenes, resulting in a reduction of approximately 2.8 log CFU/cm² for some selected strains. Additionally, Enterococcus monocultures' biofilms were more efficient than polymicrobial cultures (a cocktail of enterococci strains) in controlling pathogen adhesion. These results indicate that monocultures of Enterococcus spp. biofilms could be used to prevent the adhesion of pathogenic bacteria on AISI 316 L.

Disruption of Pseudomonas aeruginosa Adherent Cells by NaCl and NaOCl in Drinking Water.

The aim of this study was to compare and explain the disruptive effect of sodium chloride and sodium hypochlorite on the adherent cells of P. aeruginosa on glass slides. To this end, the surface characteristics of glass slides and P. aeruginosa were estimated using the contact angle method. In addition, the effects of NaCl and NaOCl on the attachment of the adherent cells were revealed using optical microscopy. The contact angle data showed moderate effects of NaCl and NaOCl on the P. aeruginosa surface, which became faintly more hydrophilic (21.9 mJ/m2, 51.1 mJ/m2) and a stronger electrons donor (53.4 mJ/m2, 54.3 mJ/m2). NaCl reversed the hydrophobicity of glass, with its surface becoming very hydrophobic (- 31.7 mJ/m2) and a weak electrons donor (7.4 mJ/m2), whereas NaOCl enhanced the hydrophobicity of glass (49.3 mJ/m2) and its electrons donor character (62.7 mJ/m2). The optical microscopy showed that NaCl caused a clear and progressive disruption of the colonization, while NaOCl had no effect. Briefly, this study suggests that a combination of NaCl and NaOCl may solve the problem of P. aeruginosa installation in water tracks.

Anti-adhesion and antibiofilm activities of Lavandula mairei humbert essential oil against Acinetobacter baumannii isolated from hospital intensive care units.

This study aimed to assess, for the first time, the anti-adhesion and antibiofilm effects of Lavandula mairei Humbert essential oil against multidrug resistant Acinetobacter baumannii. Scanning electron microscope was used for visualizing its antibiofilm activity and the effect of this oil on surface physicochemical parameters was examined as a possible anti-adhesive target. Chemical analysis of Lavandulaa mairei essential oil showed a high content of carvacrol composition (79.12%). The oil tested exhibited antibacterial efficacy with inhibition diameters of 33 to 37.33 mm and minimum inhibitory and bactericidal concentrations of 1.56 µl ml-1. The oil inhibited adhesion by 83.66%, detach 73.30% of adherent cells and eliminated 64.02% of the biofilm compared to the untreated control. Lavandula mairei essential oil has proven its possible application as a preventive strategy by intervening in the initial adhesion of Acinetobacter baumannii to polystyrene.

COVID-19: unbalanced management of occupational risks-case of the analysis of the chemical risk related to the use of disinfectants in the dairy industry in Morocco.

Moroccan employers have a strong responsibility for the safety and health of their employees in the workplace and for protecting them from the risk of COVID-19 and any occupational hazards, as required by Moroccan law. As a consequence, industries, including the agri-food sector, have put in place preventive measures to deal with this pandemic on several fronts, including the use of hydroalcoholic products and bleach for personal and surface disinfection. These disinfection actions may eliminate or reduce the risk of coronavirus infection, but the increased use of these products by employees could lead to serious health problems and increase the occupational chemical risk in the event of uncontrolled exposure. In order to analyze this risk in the dairy industry in Morocco, we have launched a qualitative and quantitative study to identify and assess the severity of chemical risk to which its employees are exposed. This involves an analysis of the safety data sheets [MSDS] of the disinfectants used and a health and safety survey of the users of these products, particularly for hand disinfection. This analysis showed that this chemical risk is omnipresent and prevention measures are partially adopted. Indeed, the strengthening of health safety measures to combat COVID-19 has significantly increased this risk, resulting in a remarkable imbalance in the assessment and management of occupational risks in this industry. These results have led us to propose corrective and preventive measures against this risk to interested parties and to adopt an integrated management of food and occupational health risks in a single system. This is the use of the Risk Analysis-Critical Control Points (HACCP)-Tool for a First Risk Assessment by Activity Analysis (OPERA) approach, which we developed and proposed in a previous study, for a simplified management of chemical risk in the food industry, especially in small- and medium-sized enterprises.

Adhesion Behavior of Escherichia coli Strains on Glass: Role of Cell Surface Qualitative and Quantitative Hydrophobicity in Their Attachment Ability.

Microbial adhesion to surfaces is thought to involve physicochemical interactions between the substrate and microbial cells. Understanding the physicochemical aspects involved in the adhesion phenomenon, as a critical step in biofilm formation, is essential to finding ways to prevent their formation and control biocontamination risks. The aim of this study was to investigate the relation between the adhesion behavior of 12 Escherichia coli strains isolated from food and their surface hydrophobicities using qualitative (θ w ) and quantitative (ΔG iwi ) approaches. The surface physicochemical properties of both bacterial cells and glass material were estimated through contact angle measurements. The adhesive behavior of E. coli strains on a glass surface was assessed. The results showed a good logarithmic relation between the percentage of the adhered cells and their surface hydrophobicity with the quantitative approach ΔG iwi ; however, qualitative hydrophobicity (θ w ) appeared to demonstrate no effect regarding adhesion behavior. This work lays the foundation for future studies and opens an important debate on the mechanisms underlying the adhesion behavior of E. coli strains by using the thermodynamic approach (ΔG iwi ) as an important model of hydrophobicity that could explain and predict better bacterial adhesion ability.

Environmental surveillance of Legionella pneumophila in hot water systems of hotels in Morocco.

OBJECTIVE: Environmental monitoring of Legionella in hot water systems of hotels in Morocco was performed during the period from January 2016 to April 2018. A total of 149 water samples from 118 different hotels were analyzed. METHODS: A total of 149 water samples from 118 different hotels were analyzed. Possible risk factors were prospectively recorded, and data were analyzed in connection with building and plumbing systems characteristics. Data about building and risk factors were collected through a questionnaire survey. RESULTS: Out of the 149 samples, 77(51.7%) were positive for L. pneumophila. Serological typing of the isolates revealed that 54 (70.1%) are L. pneumophila serogroup 2-15 and 23 (29.9%) are L. pneumophila serogroup 1. 56.8% of all buildings were colonized by L. pneumophila. Counts were over 1,000 CFU/L in 44%. Contamination was strongly correlated with temperature in the circulation, the age of the premise plumbing and the size of the building. CONCLUSIONS: The results showed a relevant exposure to L. pneumophila in the community and the identified risk factors can serve as indicators for risk assessment and relevant actions.

Role of biofilms in the survival of Legionella pneumophila to sodium chloride treatment.

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%. However, 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 recolonization of L. pneumophila in water distribution systems.

The theoretical adhesion of Pseudomonas aeruginosa and Escherichia coli on some plumbing materials in presence of distilled water or tap water.

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]<0). However, colonization became thermodynamically less favorable or unfavorable (increase in [Formula: see text] values) with SDW and STW, respectively. Finally, the results suggest that the choice of the most suitable material for a drinking water installation is related to the quality of the water itself.

Focus on the predictive management of COVID-19 risk in educational institutions in Morocco.

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.

Structural characterization, antioxidant, and antibiofilm activities of Coffea canephora green seeds.

OBJECTIVES: In order to explore Coffea canephora green seeds as natural extract for application in the functional-food industry, we focused this study to the evaluation of the antioxidant and the antiadhesion effect of C. canephora green seeds extracts. METHODS: The analysis of C. canephora green seeds extracts was carried out by RP-HPLC-PDA. These extracts were screened for antioxidant activities by ABTS and phenanthroline assays. The antibacterial activity was determined by microdilution method against three reference bacteria. The inhibition of bacterial adhesion at 1/8 MIC was carried out against three reference bacteria. RESULTS: The RP-HPLC-PDA revealed the presence of gallic acid, vanillin, quercetin, chlorogenic acid, and P-coumaric acid. The n-buatnol extract have the highest activity ABTS assays (3.96 ± 0.08 µg/mL). For this extract, the A0.5 was 1.90 ± 0.05 µg/mL for phenanthroline assay. The n-butanol extract and the methanolic extract have the higher antibacterial activity against Staphylococcus aureus ATCC 25923 (40 µg/mL).At MIC/8, the extracts of C. canephora showed 70% higher antidhesive activity against S. aureus ATCC 25923. CONCLUSIONS: Our finding provides an effective and specific new approach to the search of antioxidant and antiadhesive compounds for different uses.

Pseudomonas aeruginosa Biofilm Removal from Two Kinds of Granite Commonly Found in Catering Kitchen.

The biofilm formation on the surfaces which are in direct contact with food products might lead to their contamination and, consequently, present serious health problems for the consumers. The goals of the present work were to study P. aeruginosa biofilm formation on two granites and to investigate the efficiency of sodium hypochlorite (NaCLO) against the same biofilm formed on these substrata using the plate count method (PCM) and epifluorescence microscopy (EP). More biofilm cells adhered to Rosa Porrino than Gris Pinhel, and the PCM method indicated that NaCLO was efficient against the biofilm installed on the Gris Pinhel at the concentration of 1.5% after 15 min of treatment, while it was not efficient against the one installed on the Rosa Porrino. By contrast, the EP showed that the biofilm persists on two granites after NaCLO treatment, at different concentrations and contact times. In addition, the surface properties of granites such as mineral composition, roughness, and physicochemical properties were determined by X-ray diffraction (XRD), scanning electron microscopy coupled with electron diffraction spectroscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared (FTIR), atomic force microscopy (AFM), and contact angle measurement (CAM), respectively. The results revealed that Gris Pinhel is hydrophilic with a high roughness value and Rosa Porrino is hydrophobic with low roughness, while both of them contain the quartz, feldspar, and mica as the main dominant compositions.

Antimicrobial Susceptibility Patterns of Legionella spp. Strains Isolated from Water Systems in Morocco.

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 originating from natural and man-made water systems. The aim of this study was to describe the level of antimicrobial susceptibility of environmental Legionella spp. strains to preferred and recommended therapeutic agents to treat Legionella disease. Methods: The minimum inhibitory concentrations (MICs) of 60 environmental Legionella spp. strains were tested using the broth dilution method. Susceptibility testing was performed for 12 antimicrobial agents: macrolides (erythromycin, azithromycin [AZI], and clarithromycin [CLA]), fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin, and gemifloxacin), a ketolide (telithromycin), cefotaxime (CEF), tigecycline (TIG), doxycycline (DOX), and rifampicin (RIF). Results: All tested strains of Legionella spp. were inhibited by low concentrations of fluoroquinolones and macrolides. Regarding the macrolides, CLA was the most active antibiotic, and AZI was the least active. RIF was the most effective antibiotic against the isolates in vitro. All isolates were inhibited by the following antibiotics (in decreasing order of their MICs): DOX>CEF>TIG. Conclusions: No resistance against these drugs was detected, and all isolates were inhibited by low concentrations of the tested antibiotics. Susceptibility testing of environmental Legionella spp. isolates must be monitored often to detect and evaluate the possible development of antibiotic resistance.

Adhesion of Legionella pneumophila on glass and plumbing materials commonly used in domestic water systems.

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.

A study of pH effects on the bacterial surface physicochemical properties of Acinetobacter baumannii.

The first step in the biofilm formation is the bacterial attachment to solid surfaces, which is dependent on the bacteria cell surface physico-chemical properties. The purpose of this work was to analyze the effect of pH on the physicochemical cell surface properties of Acinetobacter baumannii by two different methods. The cell surface properties were evaluated using the microbial adhesion to solvents method (MATS) and contact angle measurements (CAM). MATS technique allowed us to enlighten that A. baumannii was hydrophilic at the different values of pH. It was found that at a desired pH of 6.5, the strain presents a maximum and stable value of electron-donor characteristic, while the electron acceptor character increased as the pH increased. Regardless of the methods employed, the obtained results using MATS and CAM confirmed the influence of the pH on the surface physicochemical properties of A. baumannii. The cell surface electron-donor and electron-acceptor character at pH 6.5 was found to be quite similar using both methods.

Environmental Scanning Electron Microscopy characterization of the adhesion of conidia from Penicillium expansum to cedar wood substrata at different pH values.

Initial microbial adhesion to surfaces is a complicated process that is affected by a number of factors. An important property of a solution that may influence adhesion is pH. The surface properties of the cedar wood were characterized by the sessile drop technique. Moreover, the interfacial free energy of surface adhesion to the cedar wood was determined under pH values (2, 3, 5, 7, 9 and 11). The results showed that cedar wood examined at different pH levels could be considered hydrophobic ranged from Giwi = -13.1 mJ/m(2) to Giwi = -75 mJ/m(2). We noted that the electron-donor character of cedar wood was important at both basic and limit acidic conditions (pH 11 and pH 3) and it decreased at intermediate pH (pH 5). The cedar wood substratum presents a weak electron acceptor under various pH's. In addition, the adhesion of conidia from Penicilllium expansum to the cedar wood surfaces at different pH values (2, 3, 5, 7, 9 and 11) was investigated using Environmental Scanning Electron Microscopy and image analysis was assessed with the Mathlab(®) program. The data analysis showed that the conidia from P. expansum were strongly influenced by the pH. The maximum adhesion occurs in the pH 11 and pH 3 and decreased to 24% at pH 5.

Evaluation of the relative cell surface charge by using microbial adhesion to hydrocarbon.

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 ofpH was similar to these obtained by microelectrophoresis method.

Comparison of contact angle measurement and microbial adhesion to solvents for assaying electron donor-electron acceptor (acid-base) properties of bacterial surface.

The electron donor-electron acceptor (acid-base properties) of cell surfaces of a series of bacteria were determined by two methods, namely, Microbial Adhesion to Solvents (MATS) and Contact Angle Measurements (CAM) combined with equation of Van Oss. The efficiency of these two methods was then compared. Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ILP 142B, Staphylococcus aureus ATCC 25923 and four Escherichia coli strains including HB101, AL52, O128B12 and ATCC 25922, acid-base properties were examined under the two different conditions mentioned above. The results showed that the correlation between acid-base properties determined by MATS and CAM was very weak. We have also found that when the microbial cell surface was electron donor by CAM method, similar result was found by MATS, but the reverse was not always true. In contrast, a good correlation between the two methods was obtained when the four E. coli strains were examined.