Microorganisms In Biofilms Research Articles

Active percolation in pusher-type microswimmers

The aggregation of microorganisms in colonies and biofilms underpins a myriad of biological processes, and has crucial implications in ecology and biomedical sciences. While much of our knowledge of microbial motion is based on single-cell mechanisms or cell-cell interactions, the origin of cooperativity in microbial communities is not yet fully understood. Here, we reveal the existence of a continuum percolation transition in two model suspensions of pusher-type microswimmers: an asymmetric dumbbell and a squirmer model. Clusters of swimmers held together by hydrodynamic forces dynamically aggregate and separate. Using simulations with explicit hydrodynamics and theory, we find that as the microswimmers' filling fraction increases, the cluster size distribution approaches a scale-free form and system-spanning clusters emerge.

DEPOLARIZATION OF CELL MEMBRANES IN THE FORMATION OF DRUG RESISTANCE

Correlation of the properties of biofilms of microorganisms and malignant tumors indicates the existence of a certain analogy between them, which allows us to explain the essential circumstances of the formation of drug resistance. Intercellular substance plays a significant role in the functioning of both types of cell groups. Both types are characterized by the formation and local accumulation of structurally damaged proteins and peptides. The regularity of their interaction with membrane’s phospholipid bilayer creates prerequisites for the formation of β-structured inclusions that are characterized by electrical conductivity. This leads to membrane depolarization and, as a result, to disruption of its barrier function. An increase in the permeability of the membrane contributes to the entry of external genetic material, the formation of mutated forms and the development of drug resistance.

Impact of zinc ion addition on corrosion of EH40 steel in natural seawater

AbstractZinc ion is a common heavy metal in marine pollution, but its impact on corrosion of steels without passive films in natural seawater is far from being investigated. In this study, the impact of zinc ion addition (1.5 and 15 mmol/L) on corrosion of EH40 steel commonly utilized for building ships and offshore platforms was studied by numerous methods and technologies. It was found that EH40 steel corrosion was inhibited with the addition of zinc ion, and corrosion inhibition efficiency increased with the concentration added. The deposited ZnO and Zn(OH)2 on the steel surface was believed to hamper electron transfer, thus inhibiting corrosion. Meanwhile, the bactericidal zinc ion and ZnO mitigated the activity of microorganisms in biofilms to reduce the damage caused by microbiologically influenced corrosion. But pitting corrosion was enhanced with a high concentration of zinc ion added due to the inhomogeneity of ZnO layers.

The Effectiveness of Herbal Versus Non-Herbal Mouthwash for Periodontal Health: A Literature Review.

Dental plaque is a biofilm of microorganisms that present naturally on the exposed tooth surface; it is the main etiological factor for many periodontal conditions and other oral health issues and its regular removal from the oral cavity can prevent many periodontal problems. Despite several experiments using herbal oral care products to reduce dental plaque or gingivitis, the findings remain inconclusive. We performed a systematic literature search on PubMed and Cochrane Library for randomized controlled trials (RCTs) dating from 2001 up to and including the year 2021. The keywords and Medical Subject Headings (MeSH) terms comprised combinations of the following: herbal, clove oil, peppermint oil, ginger, basil, ajwain, betel leaf extract, neem, lavender, non-herbal, chlorhexidine, fluorides, hydrogen fluoride, hydrogen fluoride, stannous fluoride, and mouthwashes. Each of the titles that the search elicited was screened and duplicates were removed from the gathered results. The full-text versions of the remaining articles were downloaded and examined by title and abstract. Handsearching was not carried out. We initially identified 21 studies; 14 studies, which did not fulfill the selection criteria, were excluded. All the included studies reported a reduction in plaque index (PI) and gingival index (GI) scores in both herbal and non-herbal groups. Two studies reported the superiority of the non-herbal mouthwash over the herbal one while five of the studies showed no significant difference in PI and GI scores between herbal and non-herbal mouthwash, implying equal efficacy of both, i.e., Triphala, aloe vera, tea tree, and polyherbal groups like Zingiber officinale, Rosmarinus officinalis, and Calendula officinalis, and chlorhexidine. Current research suggests that herbal mouthwashes are as effective as non-herbal mouthwashes for reducing dental plaque in the short term; however, the evidence is based on low-quality trials.

Slower antibiotics degradation and higher resistance genes enrichment in plastisphere

Microplastics (MPs) are increasingly entering the urban aquatic ecosystems, and the environmental significance and health risks of plastisphere, a special biofilm on MPs, have received widespread attention. In this study, MPs of polylactic acid (PLA) and polyvinyl chloride (PVC) and quartzite were incubated in an urban water environment, and the tetracycline (TC) degradation ability was compared. Approximatedly 24% of TC biodegraded in 28 d in the water-quartzite system, which is significantly higher than that in the water-PLA (17.3%) and water-PVC systems (16.7%). Re-incubation of microorganisms in biofilms affirmed that quartzite biofilm has a higher TC degradation capacity than the plastisphere. According to high-throughput sequencing of 16S rRNA and metagenomic analysis, quartzite biofilm contained more abundant potential TC degrading bacteria, genes related to TC degradation (eutG, aceE, and DLAT), and metabolic pathways related to TC degradation. An oligotrophic environment on the quartzite surface might lead to the higher metabolic capacity of quartzite biofilm for unconventional carbons, e.g., TC. It is also found that, compared with quartzite biofilm, the distinct microbes in the plastisphere carried more antibiotic resistance genes (ARGs). Higher affinity of MPs surface to antibiotics may lead to higher antibiotics stress on the plastisphere, which further amplify the carrying capacity for ARGs of microorganisms in the plastisphere. Compared to the nondegradable PVC MPs, surface of the biodegradable PLA plastics harbored significantly higher amounts of biomass and ARGs. Compared to the mineral particles, the capability of plastisphere has lower ability to degrade unconventional carbon sources such as the refractory organic pollutants, due to the abundance of carbon sources (adsorbed organic carbon and endogenous organic carbon) on the MPs surface. Meanwhile, the stronger adsorption capacity for pollutants also leads to higher pollutant stress (such as antibiotic stress) in plastisphere, which in turn affects the microbiological characteristics of the plastisphere itself, such as carrying more ARGs.

Host's Immunity and Candida Species Associated with Denture Stomatitis: A Narrative Review.

Denture-related Candida stomatitis, which has been described clinically in the literature, is either localized or generalized inflammation of the oral mucosa in connection with a removable prosthesis. During this inflammatory process, the mycobacterial biofilm and the host’s immune response play an essential role. Among microorganisms of this mixed biofilm, the Candida species proliferates easily and changes from a commensal to an opportunistic pathogen. In this situation, the relationship between the Candida spp. and the host is influenced by the presence of the denture and conditioned both by the immune response and the oral microbiota. Specifically, this fungus is able to hijack the innate immune system of its host to cause infection. Additionally, older edentulous wearers of dentures may experience an imbalanced and decreased oral microbiome diversity. Under these conditions, the immune deficiency of these aging patients often promotes the spread of commensals and pathogens. The present narrative review aimed to analyze the innate and adaptive immune responses of patients with denture stomatitis and more particularly the involvement of Candida albicans sp. associated with this pathology.

A Novel Irrigant to Eliminate Planktonic Bacteria and Eradicate Biofilm Superstructure With Persistent Effect During Total Hip Arthroplasty.

Numerous studies have examined the use of topical and irrigation-related adjuvants to decrease the risk of periprosthetic joint infection (PJI) after total hip arthroplasty. Many issues related to their use remain to be investigated. These include cost, antibiotic stewardship, bactericidal effect on planktonic bacteria, host cytotoxicity, necessity to irrigate/dilute potentially cytotoxic agents after their application, and impact on biofilm. Bacterial strains of microorganisms were grown in optimal medium. After the growth phase, the organisms were exposed to the novel irrigation solution (XPerience) or phosphate buffer solution (PBS) for 5minutes before a neutralizing broth was added. The colony-forming units per milliliter and the log reduction in colony-forming units in the treated sample vs the control were then determined. Subsequently, biofilms of microorganisms were grown on hydroxyapatite-coated glass slides. Each slide was then exposed to irrigation solutions for various contact times. Biofilm quantification was performed and the log10 density of each organism was obtained. Invitro testing of the irrigant demonstrated 6-log reductions in planktonic bacteria in 5minutes, and 4-log to 8-log reductions in biofilms. Laboratory tissue testing has demonstrated minimal cytotoxic effects to host tissue allowing for solution to remain in contact with the host without need for subsequent irrigation, creating a barrier to biofilm for up to 5hours after its application. This novel irrigant demonstrates high efficacy against both planktonic bacteria and bacterial biofilms in laboratory testing. Large series invivo data are necessary to further establish its efficacy in reducing primary and recurrent surgical site infections.

Succession of function, assembly, and interaction of microbial community in sequencing biofilm batch reactors under selenite stress

The mechanism of interaction between selenite, a toxic substance, and the microbial community in wastewater is still not well understood. Herein, nine sequencing biofilm batch reactors were used to systematically investigate the response of the microbial community to the continuous selenite stress. The results showed that selenite affected the reactor performance and reduced the biofilm mass. Also, it increased the proportion of the living cells, and changed the protein and polysaccharide composition of the biofilm as well as cellular secretions. Selenite facilitated the removal of NO3–N, according to water-quality and bioinformatics analyses. As such, the selenite was converted into selenium nanoparticles. α-diversity analysis further revealed that 20 μM selenite enhanced the microbial community resilience, while 200 μM selenite had the reverse effect. Community composition analysis showed that Variovorax, Rhizobium, and Simkania had positive correlations with selenite (P < 0.05). Functional prediction suggested that selenite changed the C, N, and S cycle functions. Furthermore, determinism dominated the community assembly process, and the deterministic proportion increased with the increase of selenite concentration. Network analysis showed that selenite improved the stability and positive correlation ratio of the overall microbial network, and accelerated the communication between microorganisms. However, when compared with the 20 μM selenite, the 200 μM selenite boosted the competition and parasitism/predation among microorganisms. Low-abundance genera played a key role in the network of selenite-reducing microbial community. In addition, under selenite stress, biofilm network exhibited better stability and faster information exchange than suspended network, and the positive association between biofilm and suspended microorganisms increased. All in all, this research sheds light on the interaction between selenite and microbial community, as well as provides crucial information on selenium-containing wastewater.

Chalcones with potential antibacterial and antibiofilm activities against periodontopathogenic bacteria

ObjectivesPeriodontitis is a pathology resulting from complex interaction of microorganisms in the dental biofilm with the host's immune system. Increased use of antibiotics associated with their inappropriate use has increased resistance levels in anaerobic bacteria. Therefore, identifying new antimicrobial compounds, such as chalcones, is urgent. This study evaluates the antibacterial activity and the antibiofilm activity of 15 chalcones against the periodontopathogenic bacteria Prevotella nigrescens (ATCC 33563), P. oralis (ATCC 33269), Peptostreptococcus anaerobius (ATCC 27337), Actinomyces viscosus (ATCC 43146), Porphyromonas asaccharolytica (ATCC 25260), and Fusobacterium nucleatum (ATCC 25586). MethodsThe compounds were evaluated by minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) tests. ResultsCompounds 1–6 showed good antibacterial and antibiofilm activities against most of the evaluated bacteria: MIC was lower than or equal to 6.25 μg/mL, biofilm biomass was reduced by 95%, and the compounds at concentrations between 0.78 and 100 μg/mL totally inhibited cell viability. Among the tested chalcones, 3 stood out: it was effective against all the bacteria, as revealed by the MIC and MBIC results. ConclusionsOur results have consolidated a base for the development of new studies on the effects of the tested chalcones as agents to combat and to prevent periodontitis.

Role of decontamination treatment for implant surface in the treatment of peri-implantitis.

Peri-implantitis, characterized by inflammation of tissues around implants and gradual loss of supporting bone tissue, has become one of the main causes for implant failure. Thoroughly removing the plaque biofilm on the implant surface is the first principle in the treatment of peri-implantitis. For this reason, various decontamination methods have been proposed, which can be divided into 2 categories: Removing biofilm and killing microorganisms according to the effect of plaque biofilm on the implant surface. However, at present, there is no decontamination method that can completely remove the plaque biofilm on the implant surface, and it lacks of clinical recommended guidelines. To understand the advantages and disadvantages, effectiveness and safety for different implant surface decontamination methods is of great significance to guide the clinical selection for peri-implantitis treatment.

Diagnostics and prevention of aeromonosis Cyprinus sagrio

Relevance. Aeromonosis (carp rubella, hemorrhagic septicemia, infectious abdominal dropsy, Lublin disease) — an infectious disease of fish. Carp, common carp and their hybrids from underyearlings to broodstock are susceptible to the disease. The epizootic reaches its greatest distribution in the spring-summer period, by autumn it fades and the disease takes on a chronic course.Methods. The object of research was the fish Cyprinus carpio. In the experiments, we used the reference strain Aeromonas hydrophila ATCC 7966 of the Global Center for Bioresources, as well as isolates isolated during outbreaks of carp aeromonosis in fish farms in the Moscow region. The diagnosis for the presence of aeromonosis was established on the basis of epizootological, clinical and pathological data and the results of bacteriological studies. The study of biofilms of microorganisms was carried out during cultivation in liquid nutrient media, the CFU of microorganisms was counted and sown on the surface of solid media.Results.The total number of microorganisms (CFU, lg/g) of intestinal microbiocenoses— 54,21 ±0,05 – 66,09 ±0,12. Cultures of microorganisms A. hydrophyla, A. sobria, A. caviae were isolated from blood, heart, spleen, gills, intestine, liver and kidneys of fish. During cultivation at 37 °C for 6–72 h, the adhesion of vegetative forms of bacteria with a typical shape and size of the species and the formation of a bacterial monolayer — a diffuse layer of bacterial cells — was revealed. Viable and non-viable microorganisms were differentiated by fluorescence microscopy. On meat-peptone agar with 5,0% of defibrinated blood, as a rule, the growth of b-hemolytic colonies was observed, less often a-hemolytic colonies. When determining the enzyme DNase, a light zone was found along the inoculation line on the DNA BA medium. Growth of b-hemolytic cultures was observed on meat-peptone agar with 5,0% of defibrinated blood. When determining the DNase enzyme on the surface of the dense nutrient medium “DNA BA”, a light transparent zone was revealed around the colonies of microorganisms. Prevention of aeromonosis is based on systematic monitoring of the etiological structure of pathogens of aeromonosis; feeding in feeding and summer mother ponds begins in the spring when the water temperature rises to 14 °C.

PLA Nanofibers for Microenvironmental-Responsive Quercetin Release in Local Periodontal Treatment.

The management of periodontitis remains a vital clinical challenge due to the interplay between the microorganisms of the dental biofilm and the host inflammatory response leading to a degenerative process in the surrounding tissues. Quercetin (QUE), a natural flavonol found in many foods, including apples, onions and tea, has exhibited prolonged and strong antibiofilm and anti-inflammatory effects both in vitro and in vivo. However, its clinical application is limited by its poor stability and water solubility, as well as its low bioavailability. Thus, in the present study, electrospun polylactic acid (PLA) nanofibers loaded with different amounts (5–10% w/w) of QUE were produced to rapidly respond to the acidic microenvironment typical of periodontal pockets during periodontal disease. This strategy demonstrated that PLA-QUE membranes can act as a drug reservoir releasing high QUE concentrations in the presence of oral bacterial infection (pH < 5.5), and thus limiting Pseudomonas aeruginosa PAO1 and Streptococcus mutans biofilm maturation. In addition, released QUE exerts antioxidant and anti-inflammatory effects on P. gingivalis Lipopolysaccharide (LPS)-stimulated human gingival fibroblast (HGFs). The reported results confirmed that PLA-QUE membranes could inhibit subgingival biofilm maturation while reducing interleukin release, thereby limiting host inflammatory response. Overall, this study provided an effective pH-sensitive drug delivery system as a promising strategy for treating periodontitis.

ANTIMICROBIAL ACTIVITY OF SODIUM HYPOCHLORITE, NANO SILVER AND CHLORHEXIDINE AGAINST MONO-SPECIES BIOFILMS OF SELECTED MICROORGANISMS OF ORAL SOURCES

Background: Among the measures involved in the control of endodontic infection, irrigation is an important factor in the elimination of microorganisms present in the open root canal. It is known that mechanical debridement alone does not result in a complete or permanent reduction of bacteria, therefore antimicrobial agents are used as an aid to mechanical cleaning to completely kill or reduce the number of microorganisms. Aim: To investigate the antimicrobial activity of 2.5%, 5.25% sodium hypochlorite and 2.0% chlorhexidine liquid and as the first new study of 60 mg/L silver nanoparticles as an endodontic-irrigating substances against single-species biofilms. Methods: Biofilms of Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans oral sources were produced on a cellulose nitrate membrane placed on agar medium. Membrane filters were transferred to tubes containing 2 mL of fresh broth medium plus neutralizers. Microorganisms were suspended using a vortex, and the inoculum was serially diluted 10-fold. Aliquots of the dilutions were placed on 5% blood agar medium and incubated under appropriate gaseous conditions. Colony forming units were calculated. Results: The antimicrobial agents in liquid presentation, especially 5.25% NaOCl, 2% chlorhexidine, and 2% nano-silver liquid killed the tested microorganisms more rapidly with mean rank equal to 1.4, 1.9, and 1.6, respectively. Saline did not inhibit the growth of any of the tested microorganisms, as it was statistically (p &lt; 0.05) different for NaOCl, Nano-silver and chlorhexidine. Conclusions: Preferring agents in liquid supply to get rid of biofilm microorganisms, especially 5.25% NaOCl and 60mg/L nanosilver liquid. Peer Review History: Received: 9 January 2022; Revised: 11 February; Accepted: 9 March, Available online: 15 March 2022 Academic Editor: Dr. Nuray Arı, Ankara University, Turkiye, ari@ankara.edu.tr UJPR follows the most transparent and toughest ‘Advanced OPEN peer review’ system. The identity of the authors and, reviewers will be known to each other. This transparent process will help to eradicate any possible malicious/purposeful interference by any person (publishing staff, reviewer, editor, author, etc) during peer review. As a result of this unique system, all reviewers will get their due recognition and respect, once their names are published in the papers. We expect that, by publishing peer review reports with published papers, will be helpful to many authors for drafting their article according to the specifications. Auhors will remove any error of their article and they will improve their article(s) according to the previous reports displayed with published article(s). The main purpose of it is ‘to improve the quality of a candidate manuscript’. Our reviewers check the ‘strength and weakness of a manuscript honestly’. There will increase in the perfection, and transparency. Received file: Reviewer's Comments: Average Peer review marks at initial stage: 6.5/10 Average Peer review marks at publication stage: 7.5/10 Reviewers: Prof. Dr. Gorkem Dulger, Duzce University, Turkey, gorkemdulger@yandex.com Dr. Rawaa Souhil Al-Kayali, Aleppo University, Syria, rawah67@hotmail.com Dr. Wadhah Hassan Ali Edrees, Hajja University, Yemen, edress2020@gmail.com Similar Articles: INVESTIGATION OF LIPOIDIAL CONTENTS AND THEIR ANTIMICROBIAL ACTIVITY OF FORSSKAOLEA VIRIDIS AND TRICHODESMA EHRENBERGII WILDLY DISTRIBUTED IN EGYPT ANTIMICROBIAL AND ANTIOXIDANT ACTIVITY OF PSIDIUM GUAJAVA. (GUAVA) MEDICINAL PLANT LEAVES USED IN FOLK MEDICINE FOR TREATMENT OF WOUNDS AND BURNS IN HUFASH DISTRICT AL MAHWEET GOVERNORATE–YEMEN ANTIMICROBIAL ACTIVITIES FOR HADHRAMI HONEY ON GROWTH OF SOME PATHOGENIC BACTERIA

Evaluation of oral changes and modification of the oral microbiome in patients admitted to the Intensive Care Unit

Introduction: Chlorhexidine oral decontamination protocols are the usual care offered to patients in Intensive Care Units (ICU). The admission evaluation performed by dentists is absent from the routine, leading the medical team to overlook oral diseases, as they are rarely the main cause of hospitalization and the common absence of pain or other symptoms. Healthy or not, the oral cavity has an extensive reservoir of pathogens and can spread systemic infections and modify or worsen the general health of hospitalized patients. Methods: We conducted a prospective longitudinal study in the general ICU of Hospital Sírio Libanês, in São Paulo. Oral health was assessed at admission, three, and seven’s day of hospitalization by clinically (bedside oral examination (BOE), plaque and mucosa index (MPS), presence of infectious foci) and microbiologically indexes(identification of microorganisms in saliva and biofilm).Results: Sixty patients were initially included, with 70% of oral care dependency, and 39.47% were admitted and remained with oral infectious foci throughout the study. 38 patientes clinically followed presented improvement in BOE and MPS indices. With no statistically significant differences between saliva and biofilm during the hospital stay, 27 patients had a prevalence of Candida spp, ESKAPE (E. faecalis, S.aureus, K.pneumoniae, A.baumannii, P.mirabilis, and Enterobacter spp.) and pathogens associated with nosocomial pneumonia (S.aureus, K.pneumoniae, P.aeruginosa, E.cloacae, P.mirabilis, Streptococcus spp, E.coli, H.influenza, and S.pneumoniae). Conclusion: In addition to nursing care, oral assessment at hospital admission and dental follow-up can align patients' oral hygiene protocols with their real systemic needs.

River Biofilms Microbiome and Resistome Responses to Wastewater Treatment Plant Effluents Containing Antibiotics.

Continuous exposure to low concentrations of antibiotics (sub-minimal inhibitory concentration: sub-MIC) is thought to lead to the development of antimicrobial resistance (AMR) in the environmental microbiota. However, the relationship between antibiotic exposure and resistance selection in environmental bacterial communities is still poorly understood and unproven. Therefore, we measured the concentration of twenty antibiotics, resistome quality, and analyzed the taxonomic composition of microorganisms in river biofilms collected upstream (UPS) and downstream (DWS) (at the point of discharge) from the wastewater treatment plant (WWTP) of Poitiers (France). The results of statistical analysis showed that the antibiotic content, resistome, and microbiome composition in biofilms collected UPS were statistically different from that collected DWS. According to Procrustes analysis, microbial community composition and antibiotics content may be determinants of antibiotic resistance genes (ARGs) composition in samples collected DWS. However, network analysis showed that the occurrence and concentration of antibiotics measured in biofilms did not correlate with the occurrence and abundance of antibiotic resistance genes and mobile genetic elements. In addition, network analysis suggested patterns of co-occurrence between several ARGs and three classes of bacteria/algae: Bacteroidetes incertae sedis, Cyanobacteria/Chloroplast, and Nitrospira, in biofilm collected UPS. The absence of a direct effect of antibiotics on the selection of resistance genes in the collected samples suggests that the emergence of antibiotic resistance is probably not only due to the presence of antibiotics but is a more complex process involving the cumulative effect of the interaction between the bacterial communities (biotic) and the abiotic matrix. Nevertheless, this study confirms that WWTP is an important reservoir of various ARGs, and additional efforts and legislation with clearly defined concentration limits for antibiotics and resistance determinants in WWTP effluents are needed to prevent their spread and persistence in the environment.

HORIZONTAL GENE TRANSFER AND LETAL MUTATIONS IN DISSEMINATION OF BIOFILMS AND METASTASIS

Analysis of literature data and the results of our own research on the structure of malignant neoplasms indicate the existence of a certain analogy in the mechanisms of formation and spread of biofilms of microorganisms and malignant tumors. Despite the qualitative difference between cellular abnormalities of both types, they are characterized by horizontal gene transfer, which is a consequence of the formation and accumulation of extracellular DNA of dead tissues and increased permeability of the outer cell membranes. In both cases, this leads to the formation of mutated cells that differ significantly from the original forms. The direct consequence of such mutations is the formation of cells which are low-yielding in this environment and are doomed to death. This ensures both for enrichment of the intercellular component and for the disintegration of cellular aggregates with the formation of "floating islands" of intercellular associations of both types. Such formations are sharply superior to unicellular forms in resistance to adverse environmental factors, which provides the spread of biofilms and metastasis.

Experimental and modeling investigations on the unexpected hydrogen sulfide rebound in a sewer receiving nitrate addition: Mechanism and solution

Biogenic hydrogen sulfide is an odorous, toxic and corrosive gas released from sewage in sewers. To control sulfide generation and emission, nitrate is extensively applied in sewer systems for decades. However, the unexpected sulfide rebound after nitrate addition is being questioned in recent studies. Possible reasons for the sulfide rebounds have been studied, but the mechanism is still unclear, so the countermeasure is not yet proposed. In this study, a lab-scale sewer system was developed for investigating the unexpected sulfide rebounds via the traditional strategy of nitrate addition during 195-days of operation. It was observed that the sulfide pollution was even severe in a sewer receiving nitrate addition. The mechanism for the sulfide rebound can be differentiated into short-term and long-term effects based on the dominant contribution. The accumulation of intermediate elemental sulfur in biofilm resulted in a rapid sulfide rebound via the high-rate sulfur reduction after the depletion of nitrate in a short period. The presence of nitrate in sewer promoted the microorganism proliferation in biofilm, increased the biofilm thickness, re-shaped the microbial community and enhanced biological denitrification and sulfur production, which further weakened the effect of nitrate on sulfide control during the long-term operation. An optimized biofilm-initiated sewer process model demonstrated that neither the intermittent nitrate addition nor the continuous nitrate addition was a sustainable strategy for the sulfide control. To minimize the negative impact from sulfide rebounds, a (bi)monthly routine maintenance (e.g., hydraulic flushing with nitrate spike) to remove the proliferative microorganism in biofilm is necessary.

10 - Functionalization of Restorative Dental Glass-Ceramics with Bactericidal Properties

Clinically, the periodontitis is related with the dental plaque, a biofilm of microorganisms, growth on the gum line and on the tooth interface. Therefore, a strategy to minimize this condition is the functionalization of the dental prosthesis, usually in contact with the gum, with antibacterial properties. The purpose of this study was to investigate the bactericidal potential of some commercial restorative glass-ceramic materials and to functionalize a commercial dental porcelain with antibacterial properties. Commercially available restorative glass-ceramics in powder (IPS d.SIGN), or as monolithic (IPS E.max Press e GC Initial LiSi Press) were used as control samples, and characterized by X-ray diffraction (XRD), Rietveld refinement, differential thermal analysis and particle size distribution. The IPS d.SIGN glass-ceramic was selected for functionalization with nanostructured β-AgVO 3 that was synthetized by a hydrothermal route, using AgNO 3 and NH 4 VO 3 as precursors, and characterized by XRD and Scanning Electron Microscopy (SEM). The glass-ceramic material was mixed with different percentages (1%, 2%, 4% or 6%wt) of β-AgVO 3 , uniaxially pressed at 50 MPa, and thermally treated at 900 C for 5 min, as indicated by the manufacturer. The functionalized glass-ceramics was characterized by XRD, Rietveld refinement, SEM, Vickers Hardness and Vickers indentation fracture toughness. The three commercial glass-ceramics, IPS d.SIGN, IPS E.max Press and GC Initial LiSi Press as well as the functionalized samples were evaluated for its bactericidal potential against model bacteria (Escherichia coli and Staphylococcus aureus). The as-received control samples presented leucite (KAlSi 2 O 6 ) as the only detectable crystalline phase, 62%wt of amorphous phase and a median particle size (D50) of 25.5 m in IPS d.SIGN. The product of the hydrothermal synthesis was characterized as pure needle like shaped β-AgVO 3 crystals. The heat-treated control samples still presented KAlSi 2 O 6 as the only detectable crystalline phase. However, a secondary feldspar (KAlSi 3 O 8 ) phase could be detected in the functionalized samples, which turns to be the main crystalline phase as a function of the increase in the β-AgVO 3 concentration. None of the commercially available samples showed antibacterial activity, but the IPS d.SIGN samples functionalized with 2%wt or more of β-AgVO 3 presented a clear inhibition halo, from 12, 70, 3 mm to 15, 50, 1 mm, suggesting bactericidal activity against both model bacteria. Preliminary, in vitro results indicated that the analyzed commercial dental glass ceramics demonstrated no antibacterial activity. Nevertheless, the functionalization of a commercially available veneering glass-ceramic with at least 2%wt of β-AgVO 3 can induce bactericidal activity against gram-positive and gram-negative bacteria.

Efficacy of Ozone to Eliminate Endopathogenic Microorganism in Rootcanal Biofilm.

Objective:The researchers wanted to see whether ozonated water with ultrasonication and sodium hypochlorite can destroy Enterococcus faecalis bacteria in root canals.Materials and Methods:A total of 40 single-rooted human teeth were used. A total of 100 roots were harvested and mechanically prepared. The root canals were randomly divided into four classes (n = 10) after being infected with E. faecalis for 24 h. Each sample's MTT value was calculated.Conclusions:NaOCl and aqueous ozone provide antibacterial effects in in-vitro conditions in root canals.

Detection and quantification of pathogenic microorganisms in patients with chronic periodontitis before and after treatment with chlorhexidine digluconate

The aim of this study was to evaluate the efficiency of chlorhexidine digluconate solution (CHX) as an adjunct to nonsurgical therapy (NPT) of patients with chronic periodontitis (CP), by analyzing the presence and quantity of periopathogenic microorganisms in subgingival biofilm. DNA was extracted from the subgingival biofilm obtained from 40 patients with CP divided into two groups (NPT+CHX and NPT alone as control) at baseline and 2 months after the therapy. The presence of selected periodontal pathogens (A. actinomycetemcomitans, P. gingivalis, E. corrodens, T. denticola, and T. forsythia) was determined by polymerase chain reaction (PCR), while total bacterial load was assessed by quantitative PCR. The incidence of microorganisms decreased following treatment, both with NPT+CHX and NPT alone, but without reaching statistically significant difference in the NPT group. In the NPT+CHX group, a significant reduction of prevalence of two species: T. denticola (P = 0.008) and T. forsythia (P = 0.016), as well as of total microorganism count (P = 0.002) was observed two months after treatment. In conclusion, the present findings support the use of CHX as adjunctive therapy in CP.