Microbial Biofilm Development Research Articles

Research on Obtaining Nanostructured Surfaces Efficient in Combating Microbial Biofilm

Infections that occur after the insertion of biomedical devices are a major problem; potential sources of infection are due to the adhesion of bacteria on the surface of implants, bacteria that form biofilms. In order to combat or to effectively prevent various microbial, which occur in medical procedures, we try to make compounds and materials that prevent the formation or development of microbial biofilm. The aim of this study was to obtain nanostructured surfaces based on magnetite, carboxymethylcellulose and ceftriaxone, as films with anti-infective properties in order to use them in the field of current biomedicine. To obtain nanostructured surfaces with high non-stick potential, the carboxymethylcellulose-functionalized magnetite powder was homogenized with an anti-infective agent, ceftriaxone. From the analysis of the obtained results it was found that the nanostructured surfaces obtained had a strong antimicrobial character infections and can be used successfully in the coating of medical implants, in order to combat the microbial biofilm.

New holistic approach for the management of biofilm-associated infections by myco-metabolites.

Biofilm-associated infections have increased excessively over the recent years due to the increased population having impaired immune systems or as a result of certain medical conditions like transplantation, cancer, and any other chronic ailments. The abrupt enhancement of antibiotic resistance and enhanced utilization of biomedical devices offer new opportunities for microbial colonization leading to the development of microbial biofilms. Total eradication of recalcitrant microbial biofilms demands the adoption of a holistic approach and since the fungal metabolites enriched with bioactive compounds show efficacy in inhibiting the multiple factors behind biofilm formation, the anti-biofilm activities of fungal metabolites need to be appraised. Being effective in preventing various steps of biofilm formation, including inhibition of surface adhesion and cell-to-cell communication through quorum quenching, blocking of quorum sensing receptors, and enzymes involved in microbial cell wall biosynthesis, targeting the virulence factors and finally killing of biofilm bound individual cells; myco-metabolites are found effective as a potent holistic anti-biofilm agent. The wide spectrum of bioactive substances of fungi and their anti-biofilm activities against different pathogens and their multitarget characteristics are very promising in the field of treating biofilm infections.

Evaluation Of Anti-Biofilm Activity Of Bacterial Amylase Against Human Pathogens

Global healthcare crisis has a significant impact on human health and economy because of antimicrobial resistance. Emergence of antibiotic resistance due to excessive antibiotic use results in resistant microbes. Biofilm shows integral resistance to antimicrobial agents and the host defense system. Microbes that exist in the biofilms, shows 10-1000 times resistance to antibiotics as compared to the free life style. The biofilms of bacteria serve as a great issue in not only environmental and industrial line but also play an important role in healthcare setting. The biofilm producing bacteria such as Vibrio cholerae and antibiotic resistant bacteria like methicillin resistant Staphylococcus aureus (MRSA) cause deadly infections. In present study, efficacy of bacterial amylase was tested against biofilm formation of pathogenic microbes. For this, Amylase producing bacterial isolates (isolated from a variety of sources, such as waste, rhizosphere of vegetable soil, rice field, potato, and sugarcane field soils sources (ArPs, ArDs, ArSs, ArVs and ArRs) were utilized to reduce the microbial biofilm development against pathogenic isolates of Staphylococcus aureus and Pseudomonas aeruginosa. Six bacterial isolates (SB, SW, SU, PB, PW, and PU) obtained from cancer patients of tertiary care hospitals. Amylase enzyme extracted from ArPs showed maximum growth inhibitory effect on SW pathogen, while ArRs showed minimum growth effect upon SB pathogens. However, amylase showed highest anti-biofilm activity against SW pathogen. In general, the highest biofilm inhibition was recorded at pH7 at 37°C as compared to rest of pHs and temperatures. The efficacy of bacterial amylase in biofilm inhibition of human pathogens, seem promising and having significant potential in health care systems.

Toward Personalized Oral Diagnosis: Distinct Microbiome Clusters in Periodontitis Biofilms.

Periodontitis is caused by pathogenic subgingival microbial biofilm development and dysbiotic interactions between host and hosted microbes. A thorough characterization of the subgingival biofilms by deep amplicon sequencing of 121 individual periodontitis pockets of nine patients and whole metagenomic analysis of the saliva microbial community of the same subjects were carried out. Two biofilm sampling methods yielded similar microbial compositions. Taxonomic mapping of all biofilms revealed three distinct microbial clusters. Two clinical diagnostic parameters, probing pocket depth (PPD) and clinical attachment level (CAL), correlated with the cluster mapping. The dysbiotic microbiomes were less diverse than the apparently healthy ones of the same subjects. The most abundant periodontal pathogens were also present in the saliva, although in different representations. The single abundant species Tannerella forsythia was found in the diseased pockets in about 16–17-fold in excess relative to the clinically healthy sulcus, making it suitable as an indicator of periodontitis biofilms. The discrete microbial communities indicate strong selection by the host immune system and allow the design of targeted antibiotic treatment selective against the main periodontal pathogen(s) in the individual patients.

Demonstration of Allium sativum Extract Inhibitory Effect on Biodeteriogenic Microbial Strain Growth, Biofilm Development, and Enzymatic and Organic Acid Production.

To the best of our knowledge, this is the first study demonstrating the efficiency of Allium sativum hydro-alcoholic extract (ASE) againstFigure growth, biofilm development, and soluble factor production of more than 200 biodeteriogenic microbial strains isolated from cultural heritage objects and buildings. The plant extract composition and antioxidant activities were determined spectrophotometrically and by HPLC–MS. The bioevaluation consisted of the qualitative (adapted diffusion method) and the quantitative evaluation of the inhibitory effect on planktonic growth (microdilution method), biofilm formation (violet crystal microtiter method), and production of microbial enzymes and organic acids. The garlic extract efficiency was correlated with microbial strain taxonomy and isolation source (the fungal strains isolated from paintings and paper and bacteria from wood, paper, and textiles were the most susceptible). The garlic extract contained thiosulfinate (307.66 ± 0.043 µM/g), flavonoids (64.33 ± 7.69 µg QE/g), and polyphenols (0.95 ± 0.011 mg GAE/g) as major compounds and demonstrated the highest efficiency against the Aspergillus versicolor (MIC 3.12–6.25 mg/mL), A. ochraceus (MIC: 3.12 mg/mL), Penicillium expansum (MIC 6.25–12.5 mg/mL), and A. niger (MIC 3.12–50 mg/mL) strains. The extract inhibited the adherence capacity (IIBG% 95.08–44.62%) and the production of cellulase, organic acids, and esterase. This eco-friendly solution shows promising potential for the conservation and safeguarding of tangible cultural heritage, successfully combating the biodeteriogenic microorganisms without undesirable side effects for the natural ecosystems.

In doping effect on the structural, morphological, optical and enhanced antimicrobial activity of facilely synthesized novel CuS nanostructures

In this paper, we report the impact of Indium on the structural, morphological, optical, and antibacterial properties of copper sulfide (CuS) nanoparticles produced by facile chemical Co-precipitation process. X-ray diffraction, Raman, scanning electron microscope and X-ray photoelectron spectroscopy techniques were used to investigate the phase composition and purity. Antibacterial tests were performed by well diffusion method and growth kinetics assay. The hexagonal structure of CuS nanoparticles is revealed by XRD/Raman analysis, with crystallite size ranging from 6 to 11 nm. SEM pictures also revealed a larger crystallite size with the addition of indium doping. For maximum indium doping (5 wt.%), the morphology was modified from nanoparticle to nanosheet. The existence of indium dopant was also confirmed by XPS analysis. The energy band gap shifted from 2.16 – 2.47 eV with altering indium concentrations in CuS. Indium doped CuS NPs exhibited highest antibacterial effect against Mycobacterium smegmatis (20–24 mm) while Pseudomonas aeruginosa had the lowest antimicrobial activity (12–14 mm). Growth kinetics study delineated that In:CuS had high antibacterial efficacy against all the tested microbial strains and suppress the microbial growth in the logarithmic growth phase. Hence, In:CuS might be applied as antimicrobial coatings to inhibit microbial biofilm development.

Preliminary Study on Light-Activated Antimicrobial Agents as Photocatalytic Method for Protection of Surfaces with Increased Risk of Infections

Preventing and controlling the spread of multidrug-resistant (MDR) bacteria implicated in healthcare-associated infections is the greatest challenge of the health systems. In recent decades, research has shown the need for passive antibacterial protection of surfaces in order to reduce the microbial load and microbial biofilm development, frequently associated with transmission of infections. The aim of the present study is to analyze the efficiency of photocatalytic antimicrobial protection methods of surfaces using the new photocatalytic paint activated by light in the visible spectrum. The new composition is characterized by a wide range of analytical methods, such as UV-VIS spectroscopy, electron microscopy (SEM), X-ray powder diffraction (PXRD) or X-ray photoelectron spectroscopy (XPS). The photocatalytic activity in the UV-A was compared with the one in the visible light spectrum using an internal method developed on the basis of DIN 52980: 2008-10 standard and ISO 10678—2010 standard. Migration of metal ions in the composition was tested based on SR EN1186-3: 2003 standard. The new photocatalytic antimicrobial method uses a type of photocatalytic paint that is active in the visible spectral range and generates reactive oxygen species with inhibitory effect against all tested microbial strains.

Transcriptomic Responses to Coaggregation between Streptococcus gordonii and Streptococcus oralis.

ABSTRACTCell-cell adhesion between oral bacteria plays a key role in the development of polymicrobial communities such as dental plaque. Oral streptococci such as Streptococcus gordonii and Streptococcus oralis are important early colonizers of dental plaque and bind to a wide range of different oral microorganisms, forming multispecies clumps or “coaggregates.” S. gordonii actively responds to coaggregation by regulating gene expression. To further understand these responses, we assessed gene regulation in S. gordonii and S. oralis following coaggregation in 25% human saliva. Coaggregates were formed by mixing, and after 30 min, RNA was extracted for dual transcriptome sequencing (RNA-Seq) analysis. In S. oralis, 18 genes (6 upregulated and 12 downregulated) were regulated by coaggregation. Significantly downregulated genes encoded functions such as amino acid and antibiotic biosynthesis, ribosome, and central carbon metabolism. In total, 28 genes were differentially regulated in Streptococcus gordonii (25 upregulated and 3 downregulated). Many genes associated with transporters and a two-component (NisK/SpaK) regulatory system were upregulated following coaggregation. Our comparative analyses of S. gordonii-S. oralis with different previously published S. gordonii pairings (S. gordonii-Fusobacterium nucleatum and S. gordonii-Veillonella parvula) suggest that the gene regulation is specific to each pairing, and responses do not appear to be conserved. This ability to distinguish between neighboring bacteria may be important for S. gordonii to adapt appropriately during the development of complex biofilms such as dental plaque.IMPORTANCE Dental plaque is responsible for two of the most prevalent diseases in humans, dental caries and periodontitis. Controlling the formation of dental plaque and preventing the transition from oral health to disease requires a detailed understanding of microbial colonization and biofilm development. Streptococci are among the most common colonizers of dental plaque. This study identifies key genes that are regulated when oral streptococci bind to one another, as they do in the early stages of dental plaque formation. We show that specific genes are regulated in two different oral streptococci following the formation of mixed-species aggregates. The specific responses of S. gordonii to coaggregation with S. oralis are different from those to coaggregation with other oral bacteria. Targeting the key genes that are upregulated during interspecies interactions may be a powerful approach to control the development of biofilm and maintain oral health.

Antibiofouling Activity of Graphene Materials and Graphene-Based Antimicrobial Coatings.

Microbial adhesion and biofilm formation is a common, nondesirable phenomenon at any living or nonliving material surface in contact with microbial species. Despite the enormous efforts made so far, the protection of material surfaces against microbial adhesion and biofilm formation remains a significant challenge. Deposition of antimicrobial coatings is one approach to mitigate the problem. Examples of such are those based on heparin, cationic polymers, antimicrobial peptides, drug-delivering systems, and other coatings, each one with its advantages and shortcomings. The increasing microbial resistance to the conventional antimicrobial treatments leads to an increasing necessity for new antimicrobial agents, among which is a variety of carbon nanomaterials. The current review paper presents the last 5 years’ progress in the development of graphene antimicrobial materials and graphene-based antimicrobial coatings that are among the most studied. Brief information about the significance of the biofouling, as well as the general mode of development and composition of microbial biofilms, are included. Preparation, antibacterial activity, and bactericidal mechanisms of new graphene materials, deposition techniques, characterization, and parameters influencing the biological activity of graphene-based coatings are focused upon. It is expected that this review will raise some ideas for perfecting the composition, structure, antimicrobial activity, and deposition techniques of graphene materials and coatings in order to provide better antimicrobial protection of medical devices.

Revisiting the Microscopic Processes of Biofilm Formation on Organic Carriers: A Study under Variational Shear Stresses.

The microscopic process of biofilm development on carriers is critical for interfacial regulation of biofilms in attached-growth wastewater treatment. However, the process under shear stress has not been well understood. The study purposed to revisit the processes of biofilm formation on organic carriers under different shear stresses with special highlights on bacterial reversible adhesion and pioneers in the microbial community. Biofilm formation on high-density polyethylene, polyamide, acrylonitrile butadiene styrene plastic, polyvinyl chloride, and polycarbonate carriers under shear stresses ranging from 1.0 to 2.5 Pa was investigated using Couette-Taylor reactors. Employing extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the bacterial reversible adhesion regions ranging from 3.74 ± 0.20 to 5.51 ± 0.24 nm on an organic carrier were quantified for the first time, elucidating significant differences among different carriers (p < 0.01). The colonization of pioneers in the microbial community was significantly altered by shear stress rather than carrier properties (p < 0.01). In particular, the diversity of the biofilm microbial community was pronouncedly enhanced by a higher shear stress (p < 0.01). XDLVO analysis suggested that extracellular polymeric substances had a negative feedback on subsequent microbial adhesion and biofilm development, especially the transition from reversible to irreversible bacterial adhesion. This study contributed to a better understanding of the biofilm formation process at the microscopic scale and shed light on micro-interfacial manipulation for biofilm accumulation or renewal.

Effects of Hydrogen Peroxide on Organically Fertilized Hydroponic Lettuce (Lactuca sativa L.)

Hydroponic production typically uses conventional fertilizers, but information is lacking on the use of organic hydroponic fertilizers. Development of microbial communities and biofilm that can reduce dissolved oxygen availability is a difficulty with organic hydroponics. One potential solution is the use of hydrogen peroxide (H2O2) which can reduce microbial populations and decompose to form oxygen. However, information is lacking on the impact of hydrogen peroxide on hydroponic crop performance. The aim of this study was to determine the effects of H2O2 concentrations in deep water culture hydroponics by assessing how it affects plant size and yield in lettuce (Lactuca sativa L.) “Rouxai”. In this experiment, three H2O2 treatments, namely the application of 0, 37.5 or 75 mg/L H2O2 to 4 L aerated hydroponic containers with either conventional or organic fertilizer, were compared. The containers had either fish-based organic fertilizer (4-4-1, N-P2O5-K2O) or inorganic mineral based conventional nutrient solution (21-5-20, N-P2O5-K2O), both applied at 150 mg/L N. Three replicates of each H2O2 treatment–fertilizer combination were prepared resulting in a total of eighteen mini hydroponic containers each with one head of lettuce. There were two growth cycles: fall 2018 and spring 2019. When added to conventional fertilizers, both 37.5 mg/L and 75 mg/L of H2O2 led to stunted growth or death of lettuce plants. However, when 37.5 mg/L of H2O2 was applied to organic fertilizers, the lettuce yield nearly matched that of the conventionally fertilized control, demonstrating that the application of H2O2 has the potential to make organic hydroponic fertilization a more viable method in the future.

Development of microbial biofilms on cellulosic fibers for organic matter removal in river water treatment

Development of microbial biofilms on cellulosic fibers for organic matter removal in river water treatment

Antimicrobial and Anti-Biofilm Activities of Citrus sinensis and Moringa oleifera Against the Pathogenic Pseudomonas aeruginosa and Staphylococcus aureus.

ContextThe plant Moringa oleifera Lam (Moringaceae), generally termed as drumstick tree, and Citrus sinensis Linn (Rutaceae) fruit have the ability to treat multiple human infections. A biofilm is none other than a complicated microbial community whose nature is greatly resistant to antimicrobial elements. The development of biofilms in abiotic and biotic surfaces has a connection with higher levels of mortality and morbidity. Along with that, it is regarded as a vital element of bacterial pathogenicity.AimThe present study evaluated the inhibitory effect and anti-biofilm activity of Moringa oleifera (M. oleifera) and Citrus sinensis (C. sinensis) extracts against those of pathogenic Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus).Materials and methodsTwo plant materials were collected from the local market of Tabuk city and two human pathogenic microbial strains were used in the study: S. aureus and P. aeruginosa. Further, a series of morphological, physiological, and conventional biochemical tests were performed to identify the selected microorganisms. In addition to this, the study conducted the following tests: antibiotic sensitivity test, extended-spectrum β-lactamase (ESβL), and methicillin-resistant Staphylococcus aureus (MRSA) production, biofilm formation in 96-well microtiter plates, minimum inhibitory concentration (MIC) determination, the effect of sub-MICs of C. sinensis extract and M. oleifera extract on the viability of test bacteria, and finally, measurement of the inhibition of biofilm.ResultsA remarkable result of the research is that the peel extract of C. sinensisand the flesh extract of M. oleifera efficiently inhibited biofilm formation by the addition of sub-inhibitory concentrations of (1/16 x MIC - 1/2 x MIC) MRSA and ESBL, respectively. P. aeruginosa shows high resistance to piperacillin (85.0%). Similarly, the resistance of MRSA was also high (65%) against gentamycin and amikacin antibiotics. Regarding ESBL, 12 (60%) isolates showed confirmed positive and 45% of S. aureus showed MRSA activity. On observing the 12 ESβL-positive P. aeruginosa, it was found that five strains (PS1, PS4, PS6, PS8, and PS11) have formed strong biofilm, methicillin-resistant S. aureus while four strains showed strong biofilm activity (SA2, SA4, SA5, and SA8). The MIC of C. sinensis extract and M. oleifera extract against strong biofilm producers had a range of 50-2000 µg/ml concentration after overnight incubation. The study results revealed that the antibiofilm activity comparatively showed the extract of M. oleifera was better than C. sinensisagainst the mixed culture (PS1+SA8, PS6+SA2, and PS8+SA4). Hence, it is recommended to use M. oleifera as an option to monitor the development of microbial biofilms or as a model for looking for better medicines.ConclusionThe presence of antimicrobial activity found in M. oleifera and C. sinensis extracts offers convincing evidence of their likely action as antimicrobial metabolites against the studied microorganism. Anti-biofilm assay findings have shown that M. oleifera and C. sinensis extracts have effectively blocked MRSA and ESBL development in the biofilm matrix.

The Influence of Surface Roughening and Polishing on Microbial Biofilm Development on Different Ceramic Materials.

To test the hypothesis that surface roughening and polishing of ceramics have no effect on their surface roughness and biofilm adhesion. Feldspathic ceramic Vitablocks™ TriLuxe forte (VTF), lithium disilicate glass IPS e.max Press™ (IPS) and zirconia reinforced lithium silicate Vita Suprinity™ (VS) ceramic blocks (n = 27 per group) were prepared from sintered CAD blocks using a water-cooled saw. They were further subdivided into 3 subgroups according to the surface treatment protocols (n = 9): as prepared, roughened and polished. The surface roughness of the ceramic blocks was measured using an electro-mechanical profilometer. The ceramic sections were inoculated with Streptococcus mutans and incubated for 48 hours to form a biofilm. The ceramic surfaces with the biofilms were analyzed using Confocal Laser Scanning Microscopy to calculate the percentage of live bacteria and substratum coverage by the biofilm, and further visualized using scanning electron microscopy. Statistical analysis was done with SPSS software using two-way ANOVA, followed by post hoc Bonferroni test to identify significant differences between the groups. The level of significance was set at p = 0.05. As prepared VTF showed significantly higher mean surface roughness values than as prepared IPS and VS. The mean percentage of live bacteria and biofilm coverage of the substrate were significantly higher in the roughened ceramic blocks than the as prepared and polished blocks for all three ceramic types (p < 0.05). Polished specimens of VS significantly lower percentage of biofilm coverage than the other groups (p < 0.05). This study sheds new light that adjustments of ceramic restorations prior to cementation increases the likelihood for formation and adhesion of microbial biofilms on the surface. Polished zirconia reinforced lithium disilicate ceramics demonstrated the lowest bacterial adhesion among the evaluated ceramics.

Degradation of low-density poly ethylene (LDPE) by Enterobacter cloacae AKS7: a potential step towards sustainable environmental remediation.

Plastics composed of polyethylene are non-biodegradable and are mostly harmful to the environment. Literature studies documented that the extent of microbial degradation of low-density polyethylene (LDPE) seems to be insufficient and the underlying mechanisms of such degradation remain unexplored. In the present study, efforts were given to degrade LDPE by a recently isolated bacteria Enterobacter cloacae AKS7. Scanning electron microscopic (SEM) image, tensile strength, and weight loss analysis confirmed the efficient degradation of LDPE by AKS7. To investigate the mechanism, it was observed that with the progression of time, the extent of microbial colonization got increased considerably over the LDPE surface. It was also observed that the organism (AKS7) gradually increased the secretion of extracellular polymeric substances (EPS) suggesting the formation of efficient biofilm over the LDPE surface. Furthermore, to comprehend the role of cell-surface hydrophobicity towards biofilm formation, two mutants of AKS7 were screened that showed a considerable reduction in cell-surface hydrophobicity in contrast to its wild type. The result showed that the mutants revealed compromised LDPE degradation than wild-type cells of AKS7. Further investigation revealed that the mutant cells of AKS7 were incapable of adhering to LDPE in contrast to wild-type cells. Thus, the results demonstrated that the cell-surface hydrophobicity of AKS7 favors the development of microbial biofilm over LDPE that leads to the enhanced degradation of LDPE by AKS7. Therefore, the organism holds the assurance to be considered as a promising bio-remediating agent for the sustainable degradation of polythene-based hazardous waste.

New insecticides and antimicrobials derived from Sargassum wightii and Halimeda gracillis seaweeds: Toxicity against mosquito vectors and antibiofilm activity against microbial pathogens

Phytochemicals derived from seaweeds offer a novel source of compounds to develop new insecticides and antimicrobials. In the present study, two seaweed species, the brown Sargassum wightii and the green Halimeda gracilis, were investigated. Extracts were obtained using five solvents of varying polarity (acetone, chloroform, methanol, ethanol, and water). The total phenolic content, total flavonoid content and the antioxidant activities of the extracts were estimated. The ethanol extract from S. wightii exhibited more potent antioxidant activity compared to that of the H. gracilis extracts. The ethanol extract from S. wightii possessed higher values of total phenolics, flavonoids, and antioxidant activity compared to those of the H. gracillis ethanol extract. The total phenolic and flavonoid content for ethanol extracts of S. wightii and H. gracillis was 5.5 mg gallic acid equivalent (GAE)/g, 3.8 mg GAE/g, 10 mg quercetin equivalent (QE)/g, and 8.3 mg QE/g, respectively. The total antioxidant activity of the seaweed extracts was 47 mg ascorbic acid equivalent (AAE)/g for S. wightii and 35.9 mg AAE/g for H. gracilis. Additionally, the bioactive compounds present in these seaweeds were characterized by FTIR spectroscopy and GC–MS analysis, and the antimicrobial activity of these extracts was then tested against the biofilm formation capabilities of three pathogenic Gram-negative bacteria. The ethanol extracts from S. wightii and H. gracillis presented the highest inhibitory effect with up to a 40–75% significant reduction in biofilm formation by Gram-negative bacteria. Finally, their insecticidal potential was assessed against late third instar larvae of malaria vectors (Anopheles stephensi), dengue and Zika virus vectors (Aedes aegypti), and the Japanese encephalitis vector (Culex tritaeniorhynchus). LC50 values estimated for the S. wightii ethanol extract were lower than 50 ppm against all tested mosquito species. Light microscopy revealed that morphological changes were triggered upon exposure to seaweed extracts. Overall, the present study sheds light on the relevant bioactivity of phytochemicals obtained from two widespread seaweeds, suggesting the possibility that these seaweeds can be used to develop novel and biodegradable pesticides and also antimicrobial drugs that can be used to inhibit the development of microbial biofilms.

Stress induced biofilm formation in Propionibacterium acidipropionici and use in propionic acid production.

Propionibacterium acidipropionici produces propionic acid from different sugars and glycerol; the production can be improved by high cell density fermentations using immobilized cells that help to overcome the limitations of the non-productive lag phase and product inhibition. In this study, the use of stress factors to induce P. acidipropionici to form biofilm and its use as an immobilization procedure in fermentations in bioreactors for producing propionic acid was investigated. Citric acid and sodium chloride increased exopolysaccharide production, biofilm forming capacity index and trehalose production. Analysis of the expression of trehalose synthesis-related genes otsA and treY by RT-qPCR showed significantly increased expression of only treY during log phase with citric acid, while FISH analysis showed expression of treY and luxS under the influence of both stress factors. The stress factors were then used for development of microbial biofilms as immobilization procedure on Poraver® and AnoxKaldnes® carriers in recycle batch reactors for propionic acid production from 20g/L glycerol. Highest productivities of 0.7 and 0.78g/L/h were obtained in Poraver® reactors, and 0.39 and 0.43g/L/h in AnoxKaldnes® reactors with citric acid and NaCl, respectively.

The effect of silver nanoparticles incorporation in the self-etch adhesive system on its antibacterial activity and degree of conversion: an in-vitro study

Introduction: Despite of the recent advances in the adhesive dentistry, high possibility of microbial biofilm development at the resin restoration surfaces may lead to marginal gaps and recurrent caries. Degree of conversion of the dental adhesive represents a relative assessment to its quality, and a direct correlation with its mechanical behavior. This in vitro study was carried out to investigate the minimum inhibitory concentration of antimicrobial silver nanoparticles incorporated in two forms into the self-etch adhesive system and the effect of their incorporation on the degree of conversion of the self-etch adhesive. Methods: Minimum Inhibitory Concentration of the self-etch adhesive system incorporated with nanosilver powder and solution against Streptococcus mutans was tested using an agar diffusion test. The effect of nanosilver incorporation (powder and ethanol-based solution) in the self-etch adhesive system on its degree of conversion was assessed using Attenuated Total Reflectance/ Fourier Transform Infra-Red spectrometer (ATR/ FTIR). Results: The results showed that silver nanoparticles incorporation (powder or ethanol based at 12.5 µg/ml concentration) significantly increased the antibacterial efficacy of the self-etch adhesive against Streptococcus mutans (P&lt; 0.05). Nanosilver powder possessed higher significant antibacterial effect when compared to silver ethanol based solution (P&lt; 0.05). Degree of conversion of self-etch adhesive containing nanosilver powder showed non-significant difference from the control group (p &gt; 0.05). In contrast, self-etch adhesive with nanosilver solution recorded significantly lower values when compared to the control or nanosilver powder group (P&lt; 0.05). Conclusion: The antibacterial efficacy of the adhesive system can be greatly potentiated with the addition of silver nanoparticles (12µg/mL concentration) especially the nanosilver powder. Incorporation of the antibacterial nanosilver powder in the adhesive system didn’t compromise the degree of conversion of the adhesive resin.

Study the antibacterial and antibiofilm activity of Carum copticum against antibiotic-resistant bacteria in planktonic and biofilm forms

ObjectivesMicrobial biofilms has attracted interest in the recent years because they has become the most important cause of nosocomial infections. This study was aimed to examine the antibacterial activities of Carum copticum extracts on the development of microbial biofilms and planktonic form of six pathogenic bacteria. MethodsAntimicrobial activity of the crude extracts against the planktonic form of six pathogenic bacteria: Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii and Klebsiella pneumonia was evaluated by using the disc diffusion method. Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) values was determined by macro-broth dilution technique. Anti-biofilm effects were assessed by microtiter plate method. The chemical composition of the herbal extract was identified by GC-MS. ResultsAccording to disc diffusion test (MIC and MBC) the ability of C. copticum extracts for inhibition of bacteria in planktonic form was confirmed. The best inhibitory effect of this plant on S. aureus and low inhibitory effect on A. baumannii in planktonic forms were observed. These extracts were efficient to inhibit biofilm structures and concentration of each extract has direct relation with inhibitory effect. The maximum and minimum inhibitory effects of C. copticum methanolic extract on biofilm formation were observed on A. baumannii (98%) and K. pneumoniae (19%) respectively. ConclusionThe GC-MS analysis revealed that five active compounds were present in the extract of this plant. Data obtained, suggested that the C. copticum extracts applied as antimicrobial agents against these pathogens particularly in biofilm making.

Antimicrobial Activity of Olea europaea Fatty Oil against Multi-Drug Resistant and Biofilm Forming Microorganisms

The aim of the present study was to investigate the potential antimicrobial activity of Olea europaea fatty oil against a collection of bacterial (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and fungal (Candida albicans) clinical isolates. The antimicrobial and antibiofilm activity were evaluated by broth microdilution method for establishing the minimal inhibitory concentration (MIC) and microtiter assay for determining the minimal biofilm eradication concentration (MBEC). Some of the potential microbial targets of the fatty oil were investigated by flow cytometry (FCM). The results obtained hereby revealed that Olea europaea fatty oil inhibited microbial planktonic growth (MICs values of 5.23-41.8 mg/ mL) and biofilm development on inert substrata (MBEC values of 1.31-20.9 mg/ mL). The FCM measurements confirmed that the analyzed oil induced microbial membrane damages and inhibited microbial efflux pump activity.