Single-species Biofilms Research Articles

Polymeric micelles with anti-virulence activity against Candida albicans in a single- and dual-species biofilm

Infections caused by fungal biofilms with rapidly evolving resistance against the available antifungal agents are difficult to manage. These difficulties demand new strategies for effective eradication of biofilms from both biological and inert surfaces. In this study, polymeric micelles comprised of di-block polymer, poly-(ethylene glycol) methyl ether methacrylate and poly 2-(N,N-diethylamino) ethyl methacrylate polymer, P(PEGMA-b-DEAEMA), were observed to exhibit remarkable inhibitory effects on hyphal growth of Candida albicans (C. albicans) and C. tropicalis, thus preventing biofilm formation and removing existing biofilms. P(PEGMA-b-DEAEMA) micelles showed biofilm removal efficacy of > 40% and a 1.4-log reduction in cell viability of C. albicans in its single-species biofilms. In addition, micelles alone promoted high removal percentage in a mixed biofilm of C. albicans and C. tropicalis (~ 70%) and remarkably reduced cell viability of both strains. Co-delivery of fluconazole (Flu) and amphotericin B (AmB) with micelles showed synergistic effects on C. albicans biofilms (3-log reduction for AmB and 2.2-log reduction for Flu). Similar effects were noted on C. albicans planktonic cells when treated with the micellar system combined with AmB but not with Flu. Moreover, micelle-drug combinations showed an enhancement in the antibiofilm activity of Flu and AmB against dual-species biofilms. Furthermore, in vivo studies using Caenorhabditis elegans nematodes revealed no obvious toxicity of the micelles. Targeting morphologic transitions provides a new strategy for defeating fungal biofilms of polymorphic resistance strains and can be potentially used in counteracting Candida virulence.

Антибактериальная активность хлоргексидина биглюконата по отношению к биопленочным монокультурам

On the background of a high percentage of caries incidence, the prevalence of its complications is increasing – pulpitis, apical periodontitis. Teeth with complicated caries can cause odontogenic inflammatory processes in the maxillofacial region. Being foci of chronic infection and intoxication, they have an adverse effect on the body as a whole. In connection with the above, it is obvious that determining the optimal concentration of chlorhexidine bigluconate and exposure to the dentin of the crown part of the tooth in case of carious lesion of the latter is currently very important. The purpose of the study was to evaluate the antimicrobial activity of chlorhexidine (by suspension and contact method) in various concentrations in relation to monocultures of biofilm formed on tooth sections and in U-shaped 96-well plastic plates. Material and methods. In this work, one of the most relevant pathogens for modern medicine was Staphylococcus aureus, which was one of the most powerful pathogens that form biofilms, was used as a model. The antimicrobial activity of chlorhexidine bigluconate was evaluated on S. aureus and E. coli biofilm cultures formed on dental samples and in polystyrene plastic tablets. Antimicrobial activity was evaluated by the reduction factor was determined by the difference in the number of decimal logarithms of CFU/ml in the experiment compared to the control. The obtained data was subjected to statistical processing. Results and discussion. The study revealed that 2.0 % solution of chlorhexidine bigluconate had a high level of antibacterial activity against tablet biofilm cultures of S. aureus and E. coli. When it was exposed to S. aureus and E. coli tablet biofilm cultures with exposures of 30 and 60 seconds, statistically significant differences were found (p=0.02). Secondly, statistically significant differences in the effect of sensitivity of single-species biofilm cultures of dental samples to the effect of antiseptic at the specified concentration were determined (p=0.007). At the same time, the level of antibacterial activity of 2.0 % chlorhexidine bigluconate solution in respect of tablet biofilm cultures of S. aureus and E. coli was significantly higher than in biofilm cultures of S. aureus and E. coli of dental samples (p<0.05). Conclusion. The obtained results give grounds for using them in clinical practice in order to improve the effectiveness of caries treatment which will help reduce the number of complications and on the one hand, corresponds to the main direction of medicine ‒ prevention and on the other hand, increases the level of specialized medical care provided to the population as a whole

Topography quantifications allow for identifying the contribution of parental strains to physical properties of co-cultured biofilms

Most biofilm research has so far focused on investigating biofilms generated by single bacterial strains. However, such single-species biofilms are rare in nature where bacteria typically coexist with other microorganisms. Although, from a biological view, the possible interactions occurring between different bacteria are well studied, little is known about what determines the material properties of a multi-species biofilm. Here, we ask how the co-cultivation of two B. subtilis strains affects certain important biofilm properties such as surface topography and wetting behavior. We find that, even though each daughter colony typically resembles one of the parent colonies in terms of morphology and wetting, it nevertheless exhibits a significantly different surface topography. Yet, this difference is only detectable via a quantitative metrological analysis of the biofilm surface. Furthermore, we show that this difference is due to the presence of bacteria belonging to the ‘other’ parent strain, which does not dominate the biofilm features. The findings presented here may pinpoint new strategies for how biofilms with hybrid properties could be generated from two different bacterial strains. In such engineered biofilms, it might be possible to combine desired properties from two strains by co-cultivation.

Developing New Marine Antifouling Surfaces: Learning from Single-Strain Laboratory Tests

The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is intuitive that microbial composition plays a major role in surface colonization. The rationale behind this study is to investigate whether using a mixed population for the in vitro tests yields substantially different results than using single strains during initial screening. A polymeric coating was tested against single- and dual-species cultures of two common microfouler organisms for 49 days. A bacterium (Pseudoaltermonas tunicata) and a cyanobacterium (Cyanobium sp. LEGE 10375) were used in this study. Linear regression analysis revealed that Cyanobium sp. biofilms were significantly associated with a higher number of cells, wet weight, thickness, and biovolume compared to dual-species biofilms. P. tunicata alone had a biofilm growth kinetics similar to dual-species biofilms, although the P. tunicata–Cyanobium sp. mixture developed less dense and thinner biofilms compared to both single-species biofilms. Cyanobium sp. LEGE 10375 biofilms provided the worst-case scenario, i.e., the conditions that caused higher biofilm amounts on the surface material under test. Therefore, it is likely that assessing the AF performance of new coatings using the most stringent conditions may yield more robust results than using a mixed population, as competition between microfouler organisms may reduce the biofilm formation capacity of the consortium.

Low-Temperature Plasma as an Approach for Inhibiting a Multi-Species Cariogenic Biofilm

This study aimed to determine how low-temperature plasma (LTP) treatment affects single- and multi-species biofilms formed by Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii formed on hydroxyapatite discs. LTP was produced by argon gas using the kINPen09™ (Leibniz Institute for Plasma Science and Technology, INP, Greifswald, Germany). Biofilms were treated at a 10 mm distance from the nozzle of the plasma device to the surface of the biofilm per 30 s, 60 s, and 120 s. A 0.89% saline solution and a 0.12% chlorhexidine solution were used as negative and positive controls, respectively. Argon flow at three exposure times (30 s, 60 s, and 120 s) was also used as control. Biofilm viability was analyzed by colony-forming units (CFU) recovery and confocal laser scanning microscopy. Multispecies biofilms presented a reduction in viability (log10 CFU/mL) for all plasma-treated samples when compared to both positive and negative controls (p < 0.0001). In single-species biofilms formed by either S. mutans or S. sanguinis, a significant reduction in all exposure times was observed when compared to both positive and negative controls (p < 0.0001). For single-species biofilms formed by S. gordonii, the results indicate total elimination of S. gordonii for all exposure times. Low exposure times of LTP affects single- and multi-species cariogenic biofilms, which indicates that the treatment is a promising source for the development of new protocols for the control of dental caries.

Biofilm Formation between Species Associated with Denture Stomatitis

Denture stomatitis (DS) can affect about 70% of denture wearers causing inflammation of oral mucosa underneath the removable denture mostly seen at the palatal area. Candida albicans is a well-known as the main causative agent associated with denture stomatitis. Studies shown that DS-related biofilm consists of complex structured of microbial communities. Presence of co-existing bacteria in these biofilms may also contribute to the infection. In order to understand the microbial interaction between C. albicans and bacteria, this study focus on the ability of bacteria species which are Streptococcus mutans and Staphylococcus aureus to form biofilm with and without the presence of C. albicans. For this study, two groups were observed which are the single species biofilm and the mixed species biofilm. Biofilm assay was utilized to measure biofilm mass using spectrophotometer. From the observation, single species groups formed a better biofilm when compared to fungal-bacterial biofilm. Even though biofilm assay is unable to determine the number of cell available, both species were present when fungal-bacterial biofilm sample was observed microscopically using Gram stain technique. This experiment showed that both fungal and bacteria species are able to form biofilm together and this finding can be investigated further for better understanding of DSrelated biofilm.

In vitro Activity of Oral Health Care Products on Candida Biofilm Formation.

The activity of mouthwash ingredients used in daily oral care (chlorhexidine digluconate, benzalkonium chloride, povidone iodine solution, tea tree oil) and of nystatin was evaluated not only on planktonic Candida albicans or C. glabrata, but also on the inhibition of biofilm formation. A microbroth dilution technique was used to determine the minimum inhibitory concentration of the substances against two laboratory strains and seven clinical isolates. Furthermore, a potential inhibition of biofilm formation of C. albicans or C. glabrata (single-species biofilm or mixed with two oral bacteria) was assessed. The results showed an activity of all tested substances against all C. albicans and C. glabratastrains. In the biofilm assays, a concentration-dependent effect of the substances was visible. However, a low concentration of povidone iodine solution and in particular of benzalkonium chloride seemed to increase the virulence of C. albicans. Most test substances affected both bacteria and yeasts in the mixed biofilms, only nystatin predominately reduced the yeasts. In conclusion, nystatin might be the drug of choice when exclusively preventing the colonization of Candida sp. in biofilms. The alternatives, benzalkonium chloride, povidone iodine solution, and tea tree oil, should be investigated further.

Biofilm Models for the Evaluation of Dental Treatment.

When analyzing the activity of antimicrobial agents, it should be considered that microorganisms mainly occur in biofilms. Data obtained for planktonic bacteria cannot be transferred non-critically to biofilms. Biofilm models should consider both the relevant microorganisms and the conditions present in the environment. The selection of the model depends on the question to be answered. In dentistry, single species, multispecies, or microcosms originating from saliva or dental biofilm are used to culture biofilms. Microorganism selection depends on the focus of the study, for example caries biofilms mostly include Streptococcus mutans, an endodontic biofilm consists mostly of Enterococcus faecalis, and defined anaerobes are used in periodontal/peri-implant biofilms. In contrast to single-species biofilm models in medicine, where the lowest concentration of the antimicrobial that kills microorganisms is measured, the common analyzed variables are counts of colony-forming units or the percentage of dead bacteria determined by confocal laser scanning microscopy after applying a differentiating stain. All the models are helpful to evaluate new antimicrobial treatment options. Conclusions regarding the antimicrobial activity tendency of the therapeutics can be drawn. However, there are limitations of the model and ultimately a new therapy has to be proven in randomized controlled clinical trials.

Interkingdom interaction between C. albicans and S. salivarius on titanium surfaces

BackgroundIn oral candidiasis models, Candida albicans and Streptococcus salivarius sp. biofilms have an antagonistic relationship. Due to this, S. salivarius have been used experimentally as probiotic. However, the interaction between these microorganisms in the peri-implantitis-like microenvironment remains unknown. This study aimed to evaluate the interaction between C. albicans and S. salivarius biofilms developed on titanium surfaces, under reduced oxygen levels.MethodsTitanium specimens were pre-conditioned with artificial saliva (1 h, 37 °C). Single-species biofilms of C. albicans (ATCC 90028) and co-culture biofilms of C. albicans and S. salivarius (ATCC 7073) was developed for 24 and 72 h on titanium specimens. Subsequently, the effect of these intervals of biofilm formation and the interactions among the cells were evaluated. Biofilms from cultures were collected and analyzed for cell viability (CFU/mL), biofilm biomass, and total protein dosage. Data were analyzed using Mann–Whitney test (α = 5%). In addition, co-culture biofilms were analyzed using fluorescence microscopy.ResultsC. albicans growth did not change due to the presence of S. salivarius. Besides, co-culture biofilms showed a significant difference in the number of viable cells between 24 and 72 h of biofilm development (p < 0.05). The highest biofilm biomass and protein dosage were observed in co-cultures at 72 h of biofilm development. Fluorescence microscopy showed that co-cultures biofilms at 24 h have limited number of pseudo-hyphal and hyphae cells of C. albicans. At 72 h, these types of cells have increased. S. salivarius in both stages of development was present in some clusters surrounded by C. albicans.ConclusionsCo-cultivation of C. albicans with S. salivarius in biofilms developed on titanium surfaces, under lower oxygen levels, did not affect fungus growth. In addition, S. salivarius did not hind C. albicans virulence. These findings suggest that the use of S. salivarius as a probiotic would be ineffective in peri-implant disease treatment.

Comparison of Cariogenic Characteristics between Fluoride-sensitive and Fluoride-resistant Streptococcus mutans

The aim of this study is to compare cariogenic characteristics of fluoride-sensitive &lt;i&gt;Streptococcus mutans&lt;/i&gt; [fluoride-sensitive (FS) &lt;i&gt;S. mutans&lt;/i&gt; ] and fluoride-resistant &lt;i&gt;Streptococcus mutans&lt;/i&gt; [fluoride-resistant (FR) &lt;i&gt;S. mutans&lt;/i&gt;] in the presence of sucrose, and to evaluate its effect on cariogenic biofilm formation. &lt;i&gt;S. mutans&lt;/i&gt; ATCC 25175 was continuously cultured in trypticase soy broth (TSB) containing NaF (70 ppm) for 40 days to generate FR &lt;i&gt;S. mutans&lt;/i&gt; . FS and FR &lt;i&gt;S. mutans&lt;/i&gt; were inoculated in TSB with or without 2% sucrose, and optical density and pH were measured every hour. An oral biofilm was formed using saliva bacteria and analyzed through confocal laser scanning microscopy and CFU count. Finally, the expression of glucosyltransferases genes of both &lt;i&gt;S. mutans&lt;/i&gt; was investigated through RT-PCR. FR &lt;i&gt;S. mutans&lt;/i&gt; exhibited slower growth and lower acidogenicity in the presence of sucrose compared to FS &lt;i&gt;S. mutans&lt;/i&gt; . Both cariogenic and single species biofilm formation was lower in the presence of FR &lt;i&gt;S. mutans&lt;/i&gt; , along with reduced number of bacteria. FR &lt;i&gt;S. mutans&lt;/i&gt; showed significantly low levels of gtfB, gtfC, and gtfD expression compared to FS &lt;i&gt;S. mutans&lt;/i&gt; . On the basis of results, FR &lt;i&gt;S. mutans&lt;/i&gt; may be less virulent in the induction of dental caries.

Surface properties and Streptococcus mutans - Streptococcus sanguinis adhesion of fluorotic enamel

ObjectivesThe aim of this in vitro study was to evaluate the surface properties of moderately to severely fluorotic enamel and the adhesion of Streptococcus mutans and Streptococcus sanguinis to enamel, exploring the relationship between dental fluorosis and dental caries from a microbiology perspective. MethodsWe examined the basic surface properties of moderately to severely fluorotic enamel by surface microhardness test, scanning electron microscopy (SEM) and atomic force microscopy. Then S. mutans single-species biofilms and S. mutans - S. sanguinis dual-species biofilms were cultured on fluorotic enamel surface. The morphology of biofilms, the volume of bacteria and expolysaccharides (EPS) and the number of bacteria were respectively tested by SEM, confocal laser scanning microscopy and colony-forming units (CFU) counting. ResultsFluorotic enamel displayed lower average microhardness and greater surface roughness than sound enamel, and it also showed structure defects like pores or pits. The biofilm thickness, volume of bacteria and EPS, and CFU counts of bacteria in both single-species and dual-species biofilms on fluorotic enamel were all significantly higher than those on sound enamel. The volume of bacteria and EPS in dual-species biofilms are both less than those of single-species biofilms. ConclusionsThe higher surface roughness and the structure defects of teeth with moderate to severe dental fluorosis contributed to the adhesion of S. mutans and S. sanguinis, and the increased adhesion of S. mutans may increase the susceptibility of dental caries. However, S. sanguinis would play a role as a “designer bacteria” which reduce the cariogenicity of the biofilms on fluorotic enamel surface.

BACTERIAL BIOFILM STATES ON THE GENETIC MAKEUP OF THE ORGANISM AND ITS ENVIRONMENT

The intent of this review is to consider the reasons why bacteria switch from a free-floating to a biofilm mode of growth. The currently available wealth of data pertaining to the molecular genetics of biofilm formation in commonly studied, clinically relevant, single-species biofilms will be discussed in an effort to decipher the motivation behind the transition from Planktonic to sessile growth in the human body. Four potential incentives behind the formation of biofilms by bacteria during infection are considered protection from harmful conditions in the host (defense) sequestration to a nutrient-rich area (colonization) utilization of cooperative benefits (community) biofilms normally grow as biofilms and Planktonic cultures are an in vitro artifact (biofilms as the default mode of growth).

Insights Into Mechanisms of Antimicrobial Photodynamic Action Toward Biofilms Using Phenalen-1-One Derivatives as Photosensitizers.

IntroductionIn view of increasing resistance against antibiotics and antiseptics, antimicrobial photodynamic therapy (aPDT) may be a promising approach for use in dentistry. The aim of this study was to investigate the mechanism of action of aPDT with the phenalene-1-one derivatives SAPYR and SA-PN-05 as photosensitizers by evaluating bacterial ability to replicate, membrane integrity, metabolic activity, and formation of reactive oxygen species (ROS) in biofilms of Actinomyces naeslundii, Streptococcus mutans, and Escherichia coli.Materials and MethodsSingle-species biofilms (A. naeslundii, S. mutans, and E. coli) were cultured under aerobic conditions for 48 h followed by treatment with the photosensitizers SAPYR and SA-PN-05 at various concentrations (0, 50, 100, 500 μM) and different incubation periods of 5, 10, 20, and 30 min and subsequent irradiation for 10 min (Waldmann PIB 3000; λem = 360–600 nm; 50 mW/cm2; 30 J/cm2). Control samples were treated with dH2O and kept in dark for the same periods. Bacterial ability to replicate was evaluated by colony forming unit (CFU) assay. The cytoplasmic membrane integrity was investigated by flow cytometry using SYBR Green and propidium iodide and visualized by scanning and transmission electron microscopy. For SAPYR, metabolic activity and formation of intracellular ROS after irradiation were evaluated via luminescence and fluorometric assays, respectively.ResultsSAPYR showed antimicrobial effects (>3 log10 CFU reduction) on S. mutans after 5 min and on A. naeslundii after 20 min incubation and light activation. For E. coli, CFU reduction was >2 log10 after 30 min of incubation. SA-PN-05 showed an antimicrobial effect after 5 min for all bacteria. Membrane damage upon aPDT with SAPYR was observed for E. coli, but not for S. mutans and A. naeslundii. Following treatment with SA-PN-05, irradiated samples and dark controls of all three species showed loss of membrane integrity. Luminescence and fluorometric assays showed a reduction in metabolic activity and an increase in formation of intracellular ROS in all three species upon aPDT treatment with SAPYR.ConclusionThe observed loss in ability to replicate upon aPDT with SAPYR in single-species biofilms may be due to an increase in formation of intracellular ROS upon photodynamic treatment.

High osmotic stress initiates expansion and detachment of Thalassospira sp. biofilms in glass microchannels

Control of microbial activity and biofilm growth is an essential factor in a variety of medical and industrial applications. As microbial biofilms can protect cells within from physical or chemical threats, biocide treatments are often limited in their efficiency due to the low permeability of the biofilm. Therefore, finding new treatment options against biofilms remains an issue of high importance. We explored the option of using osmotic pressure to physically deform the biofilm matrix and increase detachment from a glass surface. Our model system is a single-species biofilm of Thalassospira sp. growing in a microfluidic set-up, enabling the observation of changes in biofilm volume and detachment rate. We observed that injection of a high salinity brine (NaCl) led to a reduction of biofilm volume (water efflux), and that subsequent injection of low salinity brine caused biofilm expansion (water influx). The differential osmotic pressure imposed on the biofilm was sufficient to weaken its adhesive strength to the glass surface, causing major detachment. The current approach has value as a method for cleaning glass microfluidic channels and other glass tubing or equipment clogged by biofilms, thus avoiding the use of harsh chemicals. As the basic physical principle of osmotic pressure initiating biofilm expansion and detachment is universal, our findings could be applied to other forms of biofilm growth.

Inhibition of Mixed Biofilms of Candida albicans and Methicillin-Resistant Staphylococcus aureus by Positively Charged Silver Nanoparticles and Functionalized Silicone Elastomers.

Both bacterial and fungal organisms display the ability to form biofilms; however, mixed bacterial/fungal biofilms are particularly difficult to control and eradicate. The opportunistic microbial pathogens Candida albicans and Staphylococcus aureus are among the most frequent causative agents of healthcare-acquired infections, and are often co-isolated forming mixed biofilms, especially from contaminated catheters. These mixed species biofilms display a high level of antibiotic resistance; thus, these infections are challenging to treat resulting in excess morbidity and mortality. In the absence of effective conventional antibiotic treatments, nanotechnology-based approaches represent a promising alternative for the treatment of highly recalcitrant polymicrobial biofilm infections. Our group has previously reported on the activity of pure positively charged silver nanoparticles synthesized by a novel microwave technique against single-species biofilms of C. albicans and S. aureus. Here, we have expanded our observations to demonstrate that that silver nanoparticles display dose-dependent activity against dual-species C. albicans/S. aureus biofilms. Moreover, the same nanoparticles were used to functionalize catheter materials, leading to the effective inhibition of the mixed fungal/bacterial biofilms. Overall, our results indicate the potent activity of silver nanoparticles against these cross-kingdom biofilms. More studies are warranted to examine the ability of functionalized catheters in the prevention of catheter-related bloodstream infections.

The Rhodamine Isothiocyanate Analogue as a Quorum Sensing Inhibitor Has the Potential to Control Microbially-Induced Biofouling.

Quorum sensing inhibitors (QSIs) have been proven to be an innovative approach to interfering with biofilm formation, since this process is regulated by QS signals. However, most studies have focused on single-species biofilm formation, whereas studies of the effects of signal interference on the development of multispecies biofilm, especially in the natural environment, are still lacking. Here we develop and evaluate the anti-biofilm capability of a new QSI (rhodamine isothiocyanate analogue, RIA) in natural seawater. During the experiment, biofilm characteristics, microbial communities/functions and network interactions were monitored at 36, 80, and 180 h, respectively. The results showed that the biomass and 3D structure of the biofilm were significantly different in the presence of the QSI. The expression of genes involved in extracellular polysaccharide synthesis was also downregulated in the QSI-treated group. Dramatic differences in microbial composition, β-diversity and functions between the RIA-treated group and the control group were also observed, especially in the early stage of biofilm development. Furthermore, co-occurrence model analysis showed that RIA reduced the complexity of the microbial network. This study demonstrates that rhodamine isothiocyanate analogue is an efficient QS inhibitor and has potential applications in controlling biofouling caused by multispecies biofilm, especially in the early stage of biofouling formation.

Evaluation of different culture media to support in vitro growth and biofilm formation of bacterial vaginosis-associated anaerobes.

BackgroundBacterial vaginosis (BV) is one of the most common vaginal infections worldwide. It is associated with the presence of a dense polymicrobial biofilm on the vaginal epithelium, formed mainly by Gardnerella species. The biofilm also contains other anaerobic species, but little is known about their role in BV development.AimTo evaluate the influence of different culture media on the planktonic and biofilm growth of six cultivable anaerobes frequently associated with BV, namely Gardnerella sp., Atopobium vaginae, Lactobacillus iners, Mobiluncus curtisii, Peptostreptococcus anaerobius and Prevotella bivia.MethodsA total of nine different culture media compositions, including commercially available and chemically defined media simulating genital tract secretions, were tested in this study. Planktonic cultures and biofilms were grown under anaerobic conditions (10% carbon dioxide, 10% helium and 80% nitrogen). Planktonic growth was assessed by optical density measurements, and biofilm formation was quantified by crystal violet staining.ResultsSignificant planktonic growth was observed for Gardnerella sp., A. vaginae and L. iners in New York City III broth, with or without ascorbic acid supplementation. Biofilm quantification showed high in vitro biofilm growth for Gardnerella sp., P. anaerobius and P. bivia in almost all culture media excluding Brucella broth. Contrary, only New York City III broth was able to promote biofilm formation for A. vaginae, L. iners and M. curtisii.ConclusionsOur data demonstrate that New York City III broth relative to the other tested media is the most conducive for future studies addressing polymicrobial biofilms development as this culture medium allowed the formation of significant levels of single-species biofilms.

The Best-Practice Organism for Single-Species Studies of Antimicrobial Efficacy against Biofilms Is Pseudomonas aeruginosa.

As potable water scarcity increases across the globe; it is imperative to identify energy and cost-effective processes for producing drinking-water from non-traditional sources. One established method is desalination of brackish and seawater via reverse osmosis (RO). However, the buildup of microorganisms at the water-membrane interface, known as biofouling, clogs RO membranes over time, increasing energy requirements and cost. To investigate biofouling mitigation methods, studies tend to focus on single-species biofilms; choice of organism is crucial to producing useful results. To determine a best-practice organism for studying antimicrobial treatment of biofilms, with specific interest in biofouling of RO membranes, we answered the following two questions, each via its own semi-systematic review: 1. Which organisms are commonly used to test antimicrobial efficacy against biofilms on RO membranes? 2. Which organisms are commonly identified via genetic analysis in biofilms on RO membranes? We then critically review the results of two semi-systematic reviews to identify pioneer organisms from the listed species. We focus on pioneer organisms because they initiate biofilm formation, therefore, inhibiting these organisms specifically may limit biofilm formation in the first place. Based on the analysis of the results, we recommend utilizing Pseudomonas aeruginosa for future single-species studies focused on biofilm treatment including, but not limited to, biofouling of RO membranes.

Effects of interspecific interactions on biofilm formation potential and chlorine resistance: Evaluation of dual-species biofilm observed in drinking water distribution systems

Interspecific interactions could influence microbial resistance to disinfectants in drinking water distribution systems (DWDS). Understanding the effects of interspecific interactions on biofilm formation potential and chlorine resistance could improve future disinfection strategies and prevent the spread of infectious water-borne diseases. The present study first investigated biofilm formation of 10 bacterial groups with two mixed bacterial strains isolated from a simulated DWDS over different incubation times (24 h, 48 h, and 72 h), and then evaluated chlorine resistance of the 72 h incubated biofilms under residual 0.3, 0.6, 1, 2, 4, and 10-mg/L chlorine concentrations. The Acidovorax + Acinetobacter, Sphingomonas + Bacillus, Sphingomonas + Acidovorax, and Acidovorax + Microbacterium groups exhibited high biofilm formation potential, which could be attributed to synergism interactions. The Acinetobacter + Microbacterium, Sphingomonas + Microbacterium, and Sphingomonas + Acinetobacter groups exhibited weak or moderate biofilm formation potential, which could be attributed to competition interactions. The Acidovorax + Bacillus, Bacillus + Acinetobacter, and Bacillus + Microbacterium groups exhibited moderate biofilm formation potential, which could be attributed to the neutralism interactions. The chlorine resistance of most of the dual-species biofilms associated with Sphingomonas sp. and Bacillus cereus was higher than those of the corresponding single-species biofilms. Considering the interspecific interactions between the Microbacterium laevaniforms and four other species were mainly either neutralism or competition interactions, the chlorine resistance of the group associated with M. laevaniforms could be inhibited to some extent. The specific structures (e.g., extracellular polymeric substances and spores) of dual-species biofilm had a greater influence on chlorine resistance than interspecific interactions. There were diverse interspecific interactions. Synergism could promote chlorine resistance in dual-species biofilm, neutralism had minimal effect on the chlorine resistance, while competition could reduce the chlorine resistance, and the reduction in chlorine resistance could be mitigated if there were specific morphological structures in the biofilm such as spores.

The role of sodium alginate and gellan gum in the design of new drug delivery systems intended for antibiofilm activity of morin

The use of controlled drug delivery systems represents an alternative and promising strategy for the use of antimicrobials in the oral cavity. Microparticles, films and oral tablets based on alginate and gellan gum were developed also as a strategy to overcome the low aqueous solubility of morin. The systems were characterized in terms of morphological characteristics, mucoadhesion and in vitro drug release. Antibiofilm activity was analyzed for acidogenicity, microbial viability and the composition of the extracellular matrix of single-species biofilms. Scanning Electron Microscopy demonstrated that the microparticles were spherical, rough and compact. The film and the tablet presented smooth and continuous surface and in the inner of the tablet was porous. These systems were more mucoadhesive compared to the microparticles. The in vitro morin release profiles in artificial saliva demonstrated that the microparticles controlled the release better (39.6%), followed by the film (41.1%) and the tablet (91.4%) after 20 h of testing. The morin released from the systems reduced the acidogenicity, microbial viability, concentration of insoluble extracellular polysaccharides and dry weight of biofilms, when compared to the control group. The findings of this study showed that the morin has antibiofilm activity against cariogenic microorganisms.