Investigating the composition and distribution of microplastics surface biofilms in coral areas

In recent years, global climate change and pollution of the marine environment have caused large-scale coral deaths and severe damages to coral reef ecosystems. Numerous studies have shown that coral diseases are closely related to microorganisms. And microplastics (MPs) are a potential threat to corals. In marine ecosystems, MPs are an emerging contaminant. MPs have a strong adsorption effect on pollutants in the water environment, and they are very easily colonized by microorganisms to form biofilms. Biofilms may accumulate many pathogens, increasing the probability of coral disease. However, there is no report about the composition of biofilms on the surface of microplastics in coral growth areas. In this study, nine kinds of MPs were chosen in the experiments, which are commonly found in the ocean. Four stakeout points were selected in the coral area. Biofilms were cultivated in natural environment. The composition and distribution of biofilms on the surface of the MPs were analyzed by 16 S rRNA sequencing. The characteristics of biofilms were observed by scanning electron microscopy (SEM). The experimental results show that the species composition and abundance distribution of the biofilm on the MP surface are significantly different from the surrounding seawater. The type of MPs and the stake out point are important factors affecting the structure of the biofilm bacterial community. Compared to seawater samples, MPs are enriched with certain dominant bacteria such as Vibrionaceae, Rhodobacteraceae, Flavobacteraceae, Microtrichaceae and Sphingomonadaceae. Among them, Vibrionaceae, Rhodobacteraceae and Flavobacteraceae are closely related to the tissue damage of stony corals, and Vibrios are also the main pathogens of coral albinism. In addition, Pseudomonas and Bbellvibrio cholerae are also detected on the MPs biofilm. SEM graphs of the MPs after culture could clearly observe rod-shaped bacteria and Streptococci. This study can provide a new direction for the study of coral toxicology by MPs and provide basic data for the toxicology research of MPs.

Integrating floc, aggregate and carrier to reap high-quality anammox biofilm

This work investigated the effects of integration of floc, aggregate and carrier (IFAC) on anammox biofilm quality and development mechanisms. The IFAC system harvested high-quality anammox biofilm with a reduction of 60% in the formation period, an increment of 282.14%~397.26% in mechanical stability, an enhancement of 10.18 ~ 21.56% in ecological stability and an improvement of 9.44%~46.18% in abundance of the phylum Planctomycetes. Aggregates enabled carriers to accumulate initial biomass efficiently and equipped biofilm with additional joint forces. Floc promoted accumulation of terminal biomass, enhanced ecological stability by improving community diversity and raised abundance of the phylum Planctomycetes by assisting anammox consortium settlement. A model of the development procedure of high-quality anammox biofilm was established and a strategy for pre-designing the IFAC system to reap high-quality biofilm was proposed. We expect our findings to provide theoretical guidance for designs and applications of anammox process with excellent stability.

A novel coupling process with partial nitritation-anammox and short-cut sulfur autotrophic denitrification in a single reactor for the treatment of high ammonium-containing wastewater

In this study, a novel coupling process with partial nitritation-anaerobic ammonium oxidation (anammox) (PNA) and sulfur autotrophic denitrification (SAD) was studied using an upflow biofilm reactor with mechanical vibration. At a lower dissolved oxygen (DO) concentration (0.40 ± 0.20 mg L^-1), ammonia could be efficiently removed from synthetic wastewater by the coupling system with a total nitrogen removal efficiency (NRE) of 98% and an influent NH₄⁺-N concentration of 600 mg L^-1. In this system, the nitrate, which was produced during the anammox reaction, could be timely reduced by the SAD reaction. Compared with the conventional PNA and SAD processes, coupling the PNA and SAD processes in a single reactor prevented nitrite accumulation in the SAD reaction and reduced the total sulfate production by 59%. The high-throughput sequencing analysis supported that the SAD bacteria (Thiobacillus) and anammox bacteria (Candidatus Kuenenia) could coexist on the elemental sulfur stone. Additionally, sulfur consumption and sulfate production were increased under a high DO concentration. The sulfate production/nitrate reduction ratio and changing profile of the substrate suggested that the short-cut SAD process mainly occurred in this coupling system. Otherwise, batch experiments also suggested that the nitrite removal rate in the anammox process was 34.5 times higher than that in the SAD process. The outcomes of these experiments revealed that most of the nitrite, as an intermediate product in the SAD reaction, served as an electron acceptor for the anammox reaction. A stoichiometric calculation of this coupling process indicated that the novel reaction scheme with a high NRE was successfully achieved. Under an ideal short-cut SAD process, almost 55% of the sulfur consumption could be reduced in this coupling system. The coupling system provides a new perspective for nitrogen removal in a single reactor and further promotes anammox and SAD performance in wastewater treatment processes.

Sonophotocatalytic disinfection of Shigella species under visible light irradiation: Insights into its molecular mechanism, antibacterial resistance and biofilm formation

Microbial contamination of water is one of the major sources of many diseases worldwide. Evolution of antibacterial resistance (ABR) alongside the caveats in most of the water treatment methods causes the severity of the current problem extremely vexing. This calls for an urgent need to develop new treatment methods aiming to reduce the microbial as well as ABR load in the environment. Herein, we successfully developed a visible light assisted sonophotocatalysis (SPC) using Fe/ZnO nanoparticles (NPs) for the disinfection of Shigella dysenteriae. A consortia containing S. dysenteriae and S. flexineri was also completely disinfected using SPC. Growth conditions of S. dysenteriae like growth phases and growth temperaturehad different outcomes on the overall efficacy of SPC. Compared with catalysts such as ZnO and TiO₂, Fe/ZnO resulted in better disinfection. Multi-ROS production, mostly containing h⁺ and O₂· radicals, due to the electron displacement in the catalyst and acoustic cavitation was identified as the factors behind bacterial lethality. The ROS produced was found to interfere with the metabolic activities of S. dysenteriae by causing membrane perturbation. We identified DNA damage inside the cells and the subsequent release of intracellular components. The compositional changes in the fatty acid makeup of the cells were altered as a result of SPC and few fatty acid markers indicating the stress posed by SPC were also identified. Loss of ABR in S. dysenteriae was also recorded post SPC treatment. Abatement in the biofilm forming ability of the injured bacterial cells was also recorded, proving the extremity of stress induced by SPC. Hence, the excellent efficacy of SPC in disinfecting bacteria is proposed for tertiary water treatment applications.

Effects of Brazilian green propolis extract on planktonic cells and biofilms of multidrug-resistant strains of Klebsiella pneumoniae and Pseudomonas aeruginosa

Propolis could represent an alternative therapeutic agent for targeting multidrug-resistant bacteria due to its antimicrobial potential. The effect of Brazilian green propolis (BGP) aqueous extract (AqExt) was evaluated on eight multidrug-resistant clinical strains of Klebsiella pneumoniae and Pseudomonas aeruginosa, as well as on one reference strain for each bacterial species. The minimum bactericidal concentration (MBC) was determined and optimal concentrations were further evaluated in comparison with 0.12% chlorhexidine. The natural extract was chemically characterized by HPLC-DAD analysis. The MBC values ranged between 3.12 and 27.5 mg ml^-1. Analysis of bacterial metabolic activity after treatment for 5 min with BGP-AqExt revealed a strong antimicrobial potential, similar to chlorhexidine. The extract comprised several active compounds including quercetin, gallic acid, caffeic and p-coumaric acid, drupani, galangin, and artepillin C. Altogether, the findings suggest that BGP-AqExt is fast and effective against multidrug-resistant strains of K. pneumoniae and P. aeruginosa in planktonic cultures and biofilms.

Treating infections with ionizing radiation: a historical perspective and emerging techniques

Background

Widespread use and misuse of antibiotics have led to a dramatic increase in the emergence of antibiotic resistant bacteria, while the discovery and development of new antibiotics is declining. This has made certain implant-associated infections such as periprosthetic joint infections, where a biofilm is formed, very difficult to treat. Alternative treatment modalities are needed to treat these types of infections in the future. One candidate that has been used extensively in the past, is the use of ionizing radiation. This review aims to provide a historical overview and future perspective of radiation therapy in infectious diseases with a focus on orthopedic infections.

Methods

A systematic search strategy was designed to select studies that used radiation as treatment for bacterial or fungal infections. A total of 216 potentially relevant full-text publications were independently reviewed, of which 182 focused on external radiation and 34 on internal radiation. Due to the large number of studies, several topics were chosen. The main advantages, disadvantages, limitations, and implications of radiation treatment for infections were discussed.

Results

In the pre-antibiotic era, high mortality rates were seen in different infections such as pneumonia, gas gangrene and otitis media. In some cases, external radiation therapy decreased the mortality significantly but long-term follow-up of the patients was often not performed so long term radiation effects, as well as potential increased risk of malignancies could not be investigated. Internal radiation using alpha and beta emitting radionuclides show great promise in treating fungal and bacterial infections when combined with selective targeting through antibodies, thus minimizing possible collateral damage to healthy tissue.

Conclusion

The novel prospects of radiation treatment strategies against planktonic and biofilm-related microbial infections seem feasible and are worth investigating further. However, potential risks involving radiation treatment must be considered in each individual patient.

Biofilm Control Strategies: Engaging with the Public

There are few peer-reviewed publications about public engagement with science that are written by microbiologists; those that exist tend to be a narrative of an event rather than a hypothesis-driven investigation. However, it is relatively easy for experienced scientists to use a scientific method in their approach to public engagement. This short communication describes three public engagement activities hosted by the authors, focused on biofilm control: hand hygiene, plaque control and an externally applied antimicrobial coating. In each case, audience engagement was assessed using quantitative and/or qualitative methods. A critical evaluation of the findings enabled the construction of a public engagement 'tick list' for future events that would enable a hypothesis-driven approach with more effective communication activities and more robust evaluation.

Investigation on the effect of vitamin C on growth & biofilm-forming potential of Streptococcus mutans isolated from patients with dental caries

BACKGROUND

Streptococcus mutans is a major cause of dental caries. Its capacity to produce biofilm is fundamental in the pathogenesis of this ubiquitous condition. As maintaining a healthy dentition is a genuine goal given the contemporary advance in caries control, researchers are striving to achieve a breakthrough in caries therapy. We are taking the anti-cariogenic properties of vitamin C a step-further, considering the well-known evidence of the inversely proportionate relationship between salivary levels of vitamin C and dental caries. The aim of this study was to determine MIC, MBC, biofilm prevention concentration (BPC), and derivative measures of vitamin C against fresh clinical isolates of S. mutans to evaluate its efficacy as an anti-cariogenic agent.

RESULTS

Based on the data of four independent experiments done in quadruplicates, we found a concentration-dependent inhibitory effect of vitamin C on all S. mutans strains tested. The average MBC, MIC, and BPC of vitamin C were found to be 10.16, 9.38, and 5.61 mg/ml, respectively. Spectrophotometric quantitation of crystal violet showed diminished biofilm formation in the presence of vitamin C (p < 0.05). When compared with gentamicin, vitamin C produced a zone of inhibition that was three times as large against the clinical isolates.

CONCLUSION

Our results show that vitamin C has a negative effect on S. mutans growth and biofilm formation. Being the first to meticulously utilize BPC to explore a well-known effect of vitamin C, this report aims to help in the instigation of trials of higher evidence that will ultimately culminate in repurposing vitamin C as a novel anti-cariogenic agent, albeit further studies are required to provide auxiliary evidence in this context.

Comparison of Antibacterial Effect of Cationic Peptide LL-37 and Cefalexin on Clinical Staphylococcus aureus-induced Infection after Femur Fracture Fixation

Objective

Antimicrobial peptides are widely present in nature, with many of the antimicrobial peptides having antimicrobial activity against Gram‐positive and Gram‐negative bacteria, fungi, parasites, and even coated viruses. Internal fixation of fractures is a reliable technique. However, the fracture is difficult to heal and internal fixation is not easy to maintain after infection. This study aims to verify the antibacterial effect of cationic peptide LL‐37 on Staphylococcus aureus, explore the anti‐biofilm effects of LL‐37, and compare the effects of the cationic peptide LL‐37 and Cefalexin in treatment of postoperative infection of femoral fracture in vivo.

Methods

The Staphylococcus aureus was clinically isolated from one patient with clinical infection after the fracture fixation at Wuxi 9th People's Hospital. The cationic peptide LL‐37 was synthesized by Shanghai Apeptide Co. Ltd. To compare the effects of the cationic peptide LL‐37 and Cefalexin in the treatment of postoperative infection of femoral fracture in vivo, 63 rabbits with internal fixation of femoral fractures were inoculated intravenously with clinically isolated pathogenic bacteria suspensions. Rabbits in the treatment groups were treated with peptide LL‐37 and Cefalexin after surgery. Rabbits in the control groups were treated with physiological saline after surgery. The biofilms on internal fixtures were harvested from euthanized rabbits 1 h, 12 h, 1 day, 2 days, and 7 days after injection of LL‐37, Cefalexin, or saline and calculated by colony count. The biofilms from treatment and control groups at 7 days were analyzed by fluorescence microscopy. Blood samples were collected at 1 h, 12 h, 1 day, 2 days, and 7 days following peptide LL‐37 and Cefalexin injection.

Results

The results were compared statistically using Student's t‐test or two‐way analysis of variance (ANOVA). Cationic peptide LL‐37 showed significant inhibitory effects on clinically isolated Staphylococcus aureus (P < 0.05) compared with Cefalexin and control group at 1 day (P = 0.021), 2 days (P = 0.019), and 7 days (P = 0.025). Fluorescent images of the biofilm reveal that the numbers of cells on biofilms are far less than those in the Cefalexin and control groups at 7 days. The levels of Interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α) and C‐reactive protein (CRP) reached a maximum at 2 days following the operation. After the injection of LL‐37, there was an increase in the serum IL‐6, TNF‐α, and CRP contents in rabbits in both groups, however from 1 day postoperative the level of IL‐6 (P = 0.034), TNF‐α (P = 0.043), and CRP (P = 0.039) decreased significantly compared to the Cefalexin and control group. At 7 days postoperative, the level of IL‐6 (P = 0.029), TNF‐α (P = 0.033), and CRP (P = 0.027) had reverted to normal levels in LL‐37 groups.

Conclusions

Cationic peptide LL‐37 may be a promising agent to control internal femoral fracture fixation infection in vivo.

Characterization, antibiofilm and biocompatibility properties of chitosan hydrogels loaded with silver nanoparticles and ampicillin: an alternative protection to central venous catheters

The purpose of this study was to generate novel chitosan hydrogels (CHs) loaded with silver nanoparticles (AgNPs) and ampicillin (AMP) to prevent early formation of biofilms. AgNPs and CHs were characterized by UV-Vis, DLS, TEM, rheology, FT-IR, Raman, and SEM. The antibiofilm effect of the formulations was investigated against four multidrug-resistant and extensively drug-resistant pathogens using a colony biofilm, a high cell density and gradients model. Also, their hemostatic properties and cytotoxic effect were evaluated. Rheology results showed that CHs with AgNPs and AMP are typical non-Newtonian pseudoplastic fluids. The CH with 25 ppm of AgNPs and 50 ppm AMP inhibited the formation of biofilms of Acinetobacter baumannii, Enterococcus faecium and Staphylococcus epidermidis, while a ten-fold increase of the antimicrobial's concentration was needed to inhibit the biofilm of the β-lactamase positive Enterobacter cloacae. Further, CH with 250 ppm of AgNPs and 500 ppm AMP showed anticoagulant effect, and it was shown that all formulations were biocompatible. Besides to previous reports that described the bioadhesion properties of chitosan, these results suggest that AgNPs and AMP CHs loaded could be used as prophylactic treatment in patients with central venous catheter (CVC), inhibiting the formation of biofilms in their early stages, in addition to their anticoagulant effect and biocompatibility, those properties could keep the functionality of CVC helping to prevent complications such as sepsis and thrombosis.

Seagrass Halodule pinifolia active constituent 4-methoxybenzioic acid (4-MBA) inhibits quorum sensing mediated virulence production of Pseudomonas aeruginosa

Biofilm associated, multidrug resistant Pseudomonas aeruginosa infection remain a challenging problem in the clinical field since the conventional antibiotic therapy are largely inefficient and new approaches are needed. Inactivating the QS virulence mechanism with anti-infective agent is an attractive approach to prevent bacterial infections without resistance development. Seagrass Halodule pinifolia (Miki) Hartog has been shown to exhibit potential antimicrobial activities against harmful pathogens. Our study investigated the effects of seagrass H. pinifolia leaf extract and its bioactive constituents on QS-mediated virulence factors and biofilm formation in P. aerugonasa PAO1. Preliminary screening on antibiofilm activity showed that the methanolic extract of H. pinifolia exhibited potential inhibition of biofilm formation (96%) as compared to the control respectively. Further, the potential extract was column fractionated and the active fraction was characterized by GC-MS. In total eight active compounds (protocatacheuic acid (69.3%), rosmarinic acid (63.5%), caffeic acid (59.18%), p-coumaric acid (59.08%), 4-methoxybenzoic acid (53.19%), naringenin (52.9%), vanillic acid (49.19%), 4-hydroxybenzoic acid (41.73%)) were profiled from fraction 2 and were purified by HPLC, structurally confirmed by NMR. Among the eight compounds studied, 4-methoxybenzoic acid (4-MBA) showed an effective inhibition of bacterial growth and was considered as a lead molecule with minimum inhibitory concentration (MIC) of 62.5 μg/mL. Further the effect of 4-MBA on QS mediated virulence factors demonstrated that the compound at MIC concentration reduced the virulence factor production such as elastase (87.5%), protease (79.38%), pyocyanin (91.46%), rhamnolipid (86%), alginate (86%), chitinase (55%), exopolysaccharide production (83.72%) and CSH (78.39%) over the control respectively. Moreover, 4-MBA down regulated the QS-mediated virulence transcript levels upon treatment with 4-MBA. The present findings suggests that seagrasses may act as a newer source for the marine based drug discovery and the lead compound 4-MBA derived from H. pinifolia may act as anti-infective agent against P. aeruginosa as it controls the QS-mediated virulence production.

Spinal implant-associated infections: a prospective multicentre cohort study

This study evaluated the clinical, laboratory, microbiological, radiological and treatment characteristics of patients with early-onset and late-onset spinal implant-associated infections. Patients diagnosed with spinal implant-associated infection between 2015-2019 were prospectively included and treated according to a standardised algorithm. Infections were classified as early-onset (≤6 weeks) and late-onset (>6 weeks). Among 250 patients, 152 (61%) had early-onset and 98 (39%) had late-onset infection. Local inflammatory signs was the most common manifestation in early-onset infections (84%), whereas late-onset infections presented mainly with persisting or increasing local pain (71%). Sonication fluid was more often positive than peri-implant tissue samples (90% vs. 79%; P = 0.016), particularly in late-onset infections (92% vs. 75%; P = 0.005). Predominant pathogens were coagulase-negative staphylococci, Staphylococcus aureus and Cutibacterium spp. Debridement and implant retention was the most common surgical approach in early-onset infections (85%), whereas partial or complete implant exchange was mainly performed in late-onset infections (62%). Of the 250 patients, 220 (88%) received biofilm-active antibiotics, and median treatment duration was 11.7 weeks. Moreover, 49 patients (20%) needed more than one revision for infection and six patients (2.4%) died during hospital stay. Concluding, most spinal implant-associated infections were acquired during surgery and presented within 6 weeks of surgery. Infections presented mainly with local inflammatory signs in early-onset and with persisting or increasing pain in late-onset infections. Sonication was the most sensitive microbiological method, particularly in late-onset infections. Debridement and implant retention was used in well-integrated implants without loosening, independent of the time of infection onset.

Combined antimicrobial use of essential oils and bacteriocin bacLP17 as seafood biopreservative to control Listeria monocytogenes both in planktonic and in sessile forms

The antilisterial activity of Thymus vulgaris, Salvia officinalis essential oils (EOs) and bacteriocin bacLP17 (previously isolated from seafood) was determined, using the compounds alone and in combination. The Disk Diffusion, Minimal Inhibitory Concentration (MIC) and Agar Well Diffusion assays were used to evaluate the effectiveness of the compounds against 12 Listeria monocytogenes in planktonic form, whereas the anti-Listeria biofilm activity was determined against the same strains in optical density (O.D.) at 570 nm, with crystal violet staining method. The lowest MIC values resulted for T. vulgaris EO and bacLp17 (0.5 μl/ml and 2 μl/ml, respectively). The combinations with the best results, expressed as FIC-Index, were T. vulgaris/S. officinalis EOs and EOs/bacLp17. The anti-biofilm activity of single EOs and bacLP17 was similar, whereas the combined use of the two kinds of EOs led to a synergistic activity. Lastly, the best anti-biofilm effect was observed with the combination bacLP17/S. officinalis and bacLP17/T. vulgaris, compared to both control and the single use of the EOs. The present study suggests that the combination of natural compounds such as T. vulgaris, S. officinalis EOs and bacLp17 may be a useful approach to the control of planktonic and sessile cells of L. monocytogenes in seafood products.

Synthesis, density functional theory study and in vitro antimicrobial evaluation of new benzimidazole Mannich bases

The tri-component synthesis of novel chiral benzimidazole Mannich bases, by reaction between benzimidazole, aqueous 30% formaldehyde and an amine, the biological evaluation and DFT studies of the new compounds are reported here. The ¹H-NMR, ¹³C-NMR, FTIR spectra and elemental analysis confirm the structures of the new compounds. All synthesized compounds were screened by qualitative and quantitative methods for their in vitro antibacterial activity against 4 bacterial strains. DFT studies were accomplished using GAMESS 2012 software and HOMO-LUMO analysis allowed the calculation of electronic and structural parameters of the chiral Mannich bases. The geometry of 1-methylpiperazine, the cumulated Mullikan atomic charges of the two heteroatoms and of the methyl, and the value of the global electrophilicity index (ω = 0.0527) of the M-1 molecule is correlated with its good antimicrobial activity. It was found that the presence of saturated heterocycles from the amine molecule, 1-methyl piperazine and morpholine, respectively, contributes to an increased biological activity, compared to aromatic amino analogs, diphenylamino-, 4-nitroamino- and 4-aminobenzoic acid. The planarity of the molecules, specific bond lengths and localization of HOMO-LUMO orbitals is responsible for the best biological activities of the compounds.

Effect of anaerobic phases length on denitrifying dephosphatation biocenosis - a case study of IFAS-MBSBBR

BACKGROUND

The study aimed to evaluate the influence of the duration times of anaerobic phases on the bacterial biocenosis characterisation while denitrifying dephosphatation in the Integrated Fixed-Film Activated Sludge - Moving-Bed Sequencing Batch Biofilm Reactor (IFAS-MBSBBR). The experiment was conducted in a laboratory model. The study consisted of four series, which differed in terms of the ratio of the anaerobic phases. duration concerning the overall reaction time in the cycle. The anaerobic phases covered from 18 to 30% of the whole cycle duration. During the reactor performance that took 9 months, the influent and effluent were monitored by analysis of COD, TKN, NH₄-N, NO₂-N, NO₃-N, TP, PO₄-P, pH, alkalinity and the phosphorus uptake batch tests. Characterisation of the activated sludge and the biofilm biocenosis was based on fluorescent in situ hybridisation (identification of PAO and GAO) and the denaturing gradient gel electrophoresis patterns.

RESULTS

The organic compounds removal was high (more than 95.7%) independently of cycle configuration. The best efficiency for nitrogen (91.1%) and phosphorus (98.8%) removal was achieved for the 30% share of the anaerobic phases in the reaction time. Denitrifying PAO (DPAO) covered more than 90% of PAO in the biofilm and usually around 70% of PAO in the activated sludge. A substantial part of the polyphosphate accumulating organisms (PAO) community were Actinobacteria. The denitrifying dephosphatation activity was performed mainly by Accumulibacter phosphatis.

CONCLUSIONS

High nutrient removal efficiencies may be obtained in IFAS-MBSBBR using the denitrifying dephosphatation process. It was found that the length of anaerobic phases influenced denitrification and the biological phosphorus removal. The extension of the anaerobic phases duration time in the reaction time caused an increase in the percentage share of denitrifying PAO (DPAO) in PAO. The biocenosis of the biofilm and the activated sludge reveal different species patterns and domination of the EBPR community.

The importance of intracellular bacterial biofilm in infectious diseases

Various bacterial species, previously known as extracellular pathogens, can reside inside different host cells by adapting to intracellular modes by forming microbial aggregates with similar characteristics to bacterial biofilms. Additionally, bacterial invasion of human cells leads to failure in antibiotic therapy, as most conventional anti-bacterial agents cannot reach intracellular biofilm in normal concentrations. Various studies have shown that bacteria such as uropathogenic Escherichia coli, Pseudomonas aeruginosa, Borrelia burgdorferi,Moraxella catarrhalis, non-typeable Haemophilus influenzae, Streptococcus pneumonia, and group A Streptococci produce biofilm-like structures within the host cells. For the first time in this review, we will describe and discuss the new information about intracellular bacterial biofilm formation and its importance in bacterial infectious diseases.

Scanning electrochemical microscopy and its potential for studying biofilms and antimicrobial coatings

Biofilms are known to be well-organized microbial communities embedded in an extracellular polymeric matrix, which supplies bacterial protection against external stressors. Biofilms are widespread and diverse, and despite the considerable large number of publications and efforts reported regarding composition, structure and cell-to-cell communication within biofilms in the last decades, the mechanisms of biofilm formation, the interaction and communication between bacteria are still not fully understood. This knowledge is required to understand why biofilms form and how we can combat them or how we can take advantage of these sessile communities, e.g. in biofuel cells. Therefore, in situ and real-time monitoring of nutrients, metabolites and quorum sensing molecules is of high importance, which may help to fill that knowledge gap. This review focuses on the potential of scanning electrochemical microscopy (SECM) as a versatile method for in situ studies providing temporal and lateral resolution in order to elucidate cell-to-cell communication, microbial metabolism and antimicrobial impact, e.g. of antimicrobial coatings through the study of electrochemical active molecules. Given the complexity and diversity of biofilms, challenges and limitations will be also discussed.

Managed floodplain inundation maintains ecological function in lowland rivers

Managed environmental flows are one mechanism by which managers may restore carbon dynamics, diversity and ecological function of rivers affected by anthropogenic activities. Empirical studies that quantify such interactions in detail are few, so we measured the amounts of dissolved organic carbon, nutrients, algae and invertebrates in the main river channel following a managed environmental flow that inundated an adjacent floodplain forest. Dissolved organic carbon (DOC), seston carbon, total nitrogen (TN), and chlorophyll-a (chl-a) concentrations were greatly increased downstream. The net yield of DOC, seston carbon, TN and chl-a from the floodplain peaked at approximately 100, 50, 5 and 0.1 t d^-1, respectively during the major flow event. Total phosphorus mobilisation peaked at approximately 0.4 t d^-1. Stable isotope analysis showed that allochthonously-derived carbon was rapidly incorporated into biofilm and grazing macroinvertebrates, persisting in riverine food webs for up to four months following the flood. During a subsequent smaller flow event, the floodplain either generated no further carbon or nutrients, or was a sink for carbon and nutrients. Our results provide empirical support for the River Wave Concept and show that allowing floodplain water to return to the river downstream of forests is important for maintaining ecological function within the river channel.

Characterization of biofilm formed by multidrug resistant Pseudomonas aeruginosa DC-17 isolated from dental caries

The present work reports with the screening of biofilm-producing bacteria from the dental caries. The dental pathogens showed resistance against various antibiotics and biofilm forming ability at various levels. Among the bacterial strain, Pseudomonas aeruginosa DC-17 showed enhanced biofilm production. Extracellular polymeric substance (EPS) was synthesized by the selected bacterial isolate considerably and contributed as the major component of biofilm. EPS composed of eDNA, proteins and lipids. The total protein content of the EPS was found to be 1.928 mg/mL and was the major component than carbohydrate and DNA. Carbohydrate content was 162.3 mg/L and DNA content of EPS was 4.95 μg/mL. These macromolecules interacted in the matrix to develop dynamic and specific interactions to signalling biofilm to differentiating various environments. Also, the isolated bacteria showed resistant against various commercially available antibiotics. The isolates showed more resistance against penicillin (98%) and were sensitive against amoxicillin. Among the factors, temperature, pH and sugar concentration influenced biofilm formation. Biofilm forming ability of the selected bacterial stain was tested at various pH values and alkaline pH was favoured for biofilm production. Biofilm production was found to be maximum at 40 °C and 8% sucrose enhanced biofilm formation. Biofilm formed by P. aeruginosa DC-17 was resistant against various tested antimicrobials and chemicals.

In vivo efficacy of a unique first-in-class antibiofilm antibiotic for biofilm-related wound infections caused by Acinetobacter baumannii

Wounds complicated by biofilms challenge even the best clinical care and can delay a return to duty for service members. A major component of treatment in wounded warriors includes infected wound management. Yet, all antibiotic therapy options have been optimized against planktonic bacteria, leaving an important gap in biofilm-related wound care. We tested the efficacy of a unique compound (CZ-01179) specifically synthesized to eradicate biofilms. CZ-01179 was formulated as the active agent in a hydrogel, and tested in vitro and in vivo in a pig excision wound model for its ability to treat and prevent biofilm-related wound infection caused by Acinetobacter baumannii. Data indicated that compared to a clinical standard—silver sulfadiazine—CZ-01179 was much more effective at eradicating biofilms of A. baumannii in vitro and up to 6 days faster at eradicating biofilms in vivo. CZ-01179 belongs to a broader class of newly-synthesized antibiofilm agents (referred to as CZ compounds) with reduced risk of resistance development, specific efficacy against biofilms, and promising formulation potential for clinical applications. Given its broad spectrum and biofilm-specific nature, CZ-01179 gel may be a promising agent to increase the pipeline of products to treat and prevent biofilm-related wound infections.

Characterization of Actinobacillus seminis biofilm formation

Actinobacillus seminis is an autochthonous gram-negative bacterium that affects reproductive organs, causing epididymitis, low fertility, and occasional abortions in ovine and goats. The virulence factors and the pathogenicity mechanisms of A. seminis have not been clearly elucidated yet. In this work, biofilm production by A. seminis in in vitro assays is described and characterized. After 48-h incubation at 37 °C in trypticase soy broth, A. seminis formed biofilms containing an extracellular matrix comprised mainly of fibrillar material. Microaerophilia or the presence of calcium diminished biofilm formation in approximately 50% and 70%, respectively, but low iron concentrations increased it 40%. Through enzymatic digestion, it was found that proteins were the main component of these biofilms. Structural observations through scanning electron microscopy indicated the presence of a high amount of fibrillar material in which bacteria were immersed. Antibodies against different bacterial surface proteins, such as anti-biofilm matrix and anti-adhesin, diminished biofilm formation in 70% and 25%, respectively; whereas furanone C-30 and LED-209, compounds described as quorum-sensing inhibitors, completely inhibited biofilm formation. In conclusion, environmental conditions can influence strongly biofilm formation in A. seminis, and this could be an advantageous strategy that allows bacteria to persist inside a host.

[Fracture-related infections in traumatology : Current standards and new developments in diagnostics and treatment]

BACKGROUND

The high demands that fracture-related infections put on patients, physicians and the healthcare system have led to the establishment of a international group of experts called the Fracture-Related Infection (FRI) Consensus Group, whose aim is to develop evidence-based treatment recommendations.

DIAGNOSIS

Fracture-related infections are classified according to the time of occurrence, extent and treatment options. The diagnostic algorithm distinguishes between confirmatory and suggestive diagnostic criteria. If there are indications of an infection, tissue biopsy with microbiological and histological workup is recommended to confirm the diagnosis.

THERAPY

The primary objective of FRI treatment is to achieve fracture consolidation, while avoiding osteomyelitis. Therapeutic options are removal of the implant, eradication of the infection with implant retention or suppression of FRI. A multidisciplinary team is recommended to develop a patient-specific, optimized surgical and antimicrobial therapy.

1,3-Disubstituted urea derivatives: Synthesis, antimicrobial activity evaluation and in silico studies

The development of new antimicrobial compounds is in high demand to overcome the emerging drug resistance against infectious microbial pathogens. In the present study, we carried out the extensive antimicrobial screening of disubstituted urea derivatives. In addition to the classical synthesis of urea compounds by the reaction of amines and isocyanates, we also applied a new route including bromination, oxidation and azidination reactions, respectively, to convert 2-amino-3-methylpyridine to 1,3-disubstituted urea derivatives using various amines. The evaluation of antimicrobial activities against various bacterial strains, Candida albicans as well as Mycobacterium tuberculosis resulted in the discovery of new active molecules. Among them, two compounds, which have the lowest MIC values on Pseudomonas aeruginosa, were further evaluated for their inhibition capacities of biofilm formation. In order to evaluate their potential mechanism of biofilm inhibition, these two compounds were docked into the active site of LasR, which is the transcriptional regulator of bacterial signaling mechanism known as quorum sensing. Finally, the theoretical parameters of the bioactive molecules were calculated to establish their drug-likeness properties.

Chlorine-based DUWL disinfectant leads to a different microbial composition of water derived biofilms compared to H2O2-based chemical disinfectants in vitro

Background

Biofilm formation in dental unit waterlines (DUWL) may lead to health risks for dental staff and patients. Therefore, dental unit waterlines need to be disinfected, for instance by using chemical disinfectants. However, the application of chemical disinfectants may lead to the selection of specific microorganisms. Therefore, the aim of our study was to assess the microbial composition of water-derived biofilms, after a continuous exposure to maintenance doses of commercially available chemical disinfectants, in vitro.

Methods

The AAA-model was used to grow water derived biofilms. The biofilms were subjected to the maintenance dose of each disinfectant. To determine the microbial composition, the V4 hypervariable region of the 16S rRNA gene was sequenced. The sequences were clustered in operational taxonomic units (OTUs).

Results

The bacterial composition of biofilms in all treatment groups differed significantly (PERMANOVA F = 4.441, p = 0.001). Pairwise comparisons revealed Anoxyl treated biofilms were significantly different from all groups (p = 0.0001). In the Anoxyl-treated biofilms, the relative abundance of Comamonadaceae and Sphingopyxis was high compared to the Dentosept, Green and Clean and Oxygenal groups.

Conclusion

We concluded that exposure to low doses of the chlorine-based chemical disinfectant Anoxyl led to a substantially different composition of water derived biofilms compared to biofilms exposed to H₂O₂-based chemical disinfectants.

Polymeric nanoparticles protect the resin-dentin bonded interface from cariogenic biofilm degradation

The objective was to assess doxycycline (Dox) and zinc (Zn) doped nanoparticles' (NPs) potential to protect the resin-dentin interface from cariogenic biofilm. Three groups of polymeric NPs were tested: unloaded, loaded with zinc and with doxycycline. NPs were applied after dentin etching. The disks were exposed to a cariogenic biofilm challenge in a Drip-Flow Reactor during 72 h and 7 d. Half of the specimens were not subjected to biofilm formation but stored 72 h and 7 d. LIVE/DEAD® viability assay, nano-dynamic mechanical assessment, Raman spectroscopy and field emission electron microscopy (FESEM) analysis were performed. The measured bacterial death rates, at 7 d were 46% for the control group, 51% for the undoped-NPs, 32% for Dox-NPs, and 87% for Zn-NPs; being total detected bacteria reduced five times in the Dox-NPs group. Zn-NPs treated samples reached, in general, the highest complex modulus values at the resin-dentin interface over time. Regarding the mineral content, Zn-NPs-treated dentin interfaces showed the highest mineralization degree associated to the phosphate peak and the relative mineral concentration. FESEM images after Zn-NPs application permitted to observe remineralization of the etched and non-resin infiltrated collagen layer, and bacteria were scarcely encountered. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Dox-NPs exerted an antibacterial role but did not remineralize the bonded interface. Undoped-NPs did not improve the properties of the interfaces. Application of Zn-doped NPs during the bonding procedure is encouraged. STATEMENT OF SIGNIFICANCE: Application of Zn-doped nanoparticles on acid etched dentin reduced biofilm formation and viability at the resin-dentin interface due to both remineralization and antibacterial properties. Doxycycline-doped nanoparticles also diminished oral biofilm viability, but did not remineralize the resin-dentin interface.