Live Bacteria Research Articles

Removal effect of disinfection factors in low concentration on Pseudomonas aeruginosa biofilm

Experimental model of Pseudomonas aeruginosa biofilm was established in vitro by using biofilm reactor. The aim of this study was evaluating the removal effect of two kinds of water flowing through bactericide resin on Pseudomonas aeruginosa biofilm, and exploring the effectiveness of continuous treatment with low concentration disinfection factor on dental unit waterlines. The experimental group selected 1-2 mg/L iodinated resin (IR) filtered water and bromined hydantoin resin (BHR) filtered water with the control group selecting the sterile distilled water. Biofilms were treated by using the immersion method for 3, 7, 10, 20, and 40 days. Total viable count (TVC) and laser confocal microscopy method (CLSM) were selected to evaluate the biofilm removal effect. The result of TVC showed that in group IR, the bacterial clearance after the treatment of 3, 7, 10, and 20 days was lower than 99.9% and unqualified. The bacterial clearance after the treatment of 40 days was 99.9%,which is qualified. In group BHR, it was lower than 99.9% and unqualified after the treatment of 3, 7, and 10 days. It was and 99.99%, 100.00% after the treatment of 20, 40 days, respectively. The result of CLSM showed that before treatment, Pseudomonas aeruginosa biofilm showed a sheet and mass distribution. The bacterial coverage was 19.24%±1.97%. The proportion of viable bacteria was 93.91%±1.39%, and the biofilm matrix coverage was 17.69%±1.11%. After 20 days of treatment, the biofilm was decreased in the IR group, with the biofilm bacterial coverage reducing to 6.77%±1.61%, the proportion of live bacteria reducing to 54.85%±5.65%, and the biofilm matrix coverage reducing to 2.41%±0.85%.There was significant difference from the pre-treatment and the control (F=359.996,P<0.001). No biofilm-like structure was found in the BHR group. After 40 days of treatment, there was still a small amount of biofilm matrix residue in the IR group, with no bacterial coverage observed. The biofilm matrix coverage was 0.67%±0.47% (F=1 021.373,P<0.001). No biofilm-like structure was found in the BHR group. In conclusion, the continuous application of BHR filter water has more advantages in killing microorganisms in biofilms, removing live and dead bacteria and biofilm matrix in biofilms. Treatment water containing corresponding low concentration disinfection factors can play an important role in the field of biofilm control in dental unit waterlines.

Engineering, Structural Materials and Biomaterials: A Review of Sustainable Engineering Using Advanced Biomaterials

This paper introduces the state-of-the-art biomaterials that may be used to build in a way that is both environmentally friendly and long-term. Concrete, polymers, admixtures, asphalt, and soils are all examples of these materials. It is only because of natural selection that biomaterials may have desirable characteristics that would otherwise be impossible. They are known for characteristics that cannot be replicated in a laboratory setting. These characteristics develop throughout time and by natural means. Biomaterials' naturally occurring characteristics are ideal for meeting the demands of the building industry. Biomaterials having negligible or very negligible linear coefficients of thermal expansion may be utilized in different building applications. They aid in the reduction of internal strains because to their resistance to any change in length brought on by variations in temperature. Biomaterials have various benefits over synthetic materials, including lower production costs and less of an impact on the environment. Use of biodegradable materials may help alleviate the environmental problem caused by the dumping of synthetics. Cracks in the concrete are patched by the live bacteria inside it, making the material stronger.

Advances in anti-tumor based on various anaerobic bacteria and their derivatives as drug vehicles.

Cancer therapies, such as chemotherapy and radiotherapy, are often unsatisfactory due to several limitations, including drug resistance, inability to cross biological barriers, and toxic side effects on the body. These drawbacks underscore the need for alternative treatments that can overcome these challenges and provide more effective and safer options for cancer patients. In recent years, the use of live bacteria, engineered bacteria, or bacterial derivatives to deliver antitumor drugs to specific tumor sites for controlled release has emerged as a promising therapeutic tool. This approach offers several advantages over traditional cancer therapies, including targeted drug delivery and reduced toxicity to healthy tissues. Ongoing research in this field holds great potential for further developing more efficient and personalized cancer therapies, such as E. coli, Salmonella, Listeria, and bacterial derivatives like outer membrane vesicles (OMVs), which can serve as vehicles for drugs, therapeutic proteins, or antigens. In this review, we describe the advances, challenges, and future directions of research on using live bacteria or OMVs as carriers or components derived from bacteria of delivery systems for cancer therapy.

Effect of florfenicol on Piscirickettsia salmonis biofilm formed in materials used in salmonid nets, nylon and high-density polyethylene.

Piscirickettsiosis is the most prevalent bacterial disease affecting seawater salmon in Chilean salmon industry. Antibiotic therapy is the first alternative to counteract infections caused by Piscirickettsia salmonis. The presence of bacterial biofilms on materials commonly used in salmon farming may be critical for understanding the bacterial persistence in the environment. In the present study, the CDC Biofilm Reactor® was used to investigate the effect of sub- and over-MIC of florfenicol on both the pre-formed biofilm and the biofilm formation by P. salmonis under the antibiotic stimuli on Nylon and high-density polyethylene (HDPE) surfaces. This study demonstrated that FLO, at sub- and over-MIC doses, decreases biofilm-embedded live bacteria in the P. salmonis isolates evaluated. However, it was shown that in the P. salmonis Ps007 strain the presence of sub-MIC of FLO reduced its biofilm formation on HDPE surfaces; however, biofilm persists on Nylon surfaces. These results demonstrated that P. salmonis isolates behave differently against FLO and also, depending on the surface materials. Therefore, it remains a challenge to find an effective strategy to control the biofilm formation of P. salmonis, and certainly other marine pathogens that affect the sustainability of the Chilean salmon industry.

Sterile Fecal Filtrate From A Healthy Donor Improves Microbial Diversity In Patients With Hepatic Encephalopathy.

Hepatic encephalopathy (HE) remains one of the most debilitating complications of liver cirrhosis. Changes in gut microbiome composition have been linked to liver diseases and its complications including HE. Recent randomized controlled trials showed fecal microbiota transplantation to be safe and effective in HE treatment, however transferring unidentified live bacteria could cause various complications, including infections, especially in immunocompromised patients. This study aimed to evaluate the safety and efficacy of sterile fecal filtrate transfer (SFFT) for the modulation of the intestinal microbiome of patients with cirrhosis and HE. A custom-made air pressure filtration device was used for the sterile fecal filtrate preparation. Seven patients received SFFT from the same healthy donor. Patients were monitored at least 30 days after the procedure. Cognition tests, blood and stool sampling were performed to assess the safety and efficacy of SFFT on HE, liver function, and stool microbiome composition on follow-up days 7 and 30. SFFT was well tolerated and resulted in fluctuations in the microbial composition of study participants: α-diversity increased in 4/7 of the patients, without robust engraftment of donors' microbial composition as assessed by β-diversity analysis. No significant effect on cognition tests or liver function was noted after the procedure. One death occurred three months after the procedure, however, it was not related to the SFFT. Despite the effect on the gut microbiome, we did not observe robust improvement in patients' liver function or HE cognition tests after the procedure.

Ensiling alfalfa of foreign selection with experimental biological preparations

The article considers the results of a laboratory study of the use of experimental preparations Inoculant 1 and Inoculant 2, containing live bacteria and their combinations, in the preparation of silage from the green mass of alfalfa of foreign selection in the budding phase. The mass fraction of moisture, crude protein (CP), crude fiber (CF), as well as the concentration of the mass fraction of organic acids (lactic, acetic and butyric) were determined. The positive influence of the consortium of microorganisms in the preservation of nutrients and energy of the finished silage has been established. Elevated indicators of dry matter and metabolic energy in experimental samples were revealed, the concentration of which is significantly higher than the control ones in terms of dry matter - by 1.55 and 1.69%, in terms of metabolic energy - by 2.60 and 1.38%.

Assessment of changes in the phenotype, intensity of degranulation, death and lysis of neutrophils in &lt;i&gt;ex vivo&lt;/i&gt; modeling of &lt;i&gt;Staphylococcal&lt;/i&gt; bacteremia

Introduction. At present, it is important to study the interaction of Staphylococcus aureus with human innate immunity cells under conditions of ex vivo bacteremia modeling, but not only in experiments with phagocytes previously isolated from the blood.&#x0D; Purpose: comparative assessment of changes in the phenotype, intensity of aurophilic degranulation, death and lysis of neutrophils in whole blood samples from apparently healthy donors following the addition of live and killed microbial cells of S. aureus ATCC 6538 (209-P).&#x0D; Materials and methods. Bacteremia was modeled by adding microbes to whole blood (with heparin) at doses ranging from 108 to 101 mc/ml. The bactericidal effect was determined at different time points of blood incubation at 37C (for 6 hours) by the microbiological method. The blood leukocyte immunophenotyping was performed using flow cytometry according to the Lyse/No-Wash protocol to determine the expression of markers of azurophilic degranulation (CD63), early apoptosis (CD95) on the surface of neutrophilic granulocytes (NG) and cell adhesion (CD62L), as well as to assess the surface expression density of the molecular trigger of netosis FcᵧRIIIb (CD16) and tyrosine protein phosphatase (CD45), which is a regulator of FcR-mediated cell signaling during phagocytosis and netosis. The presence of degenerative changes in NG was confirmed by microscopy in the analysis of blood smears stained according to RomanovskyGiemsa.&#x0D; Results. Significant differences were revealed in the response of human blood NG to live and killed S. aureus cells according to the studied phenotypic parameters. Only live microbes triggered azurophilic degranulation in NCs and stimulated, starting from 2 h incubation, the appearance of a large number of NG with the CD95+ phenotype in the blood. In addition, live bacteria induced in phagocytes twice as much functional rearrangement in terms of CD45 expression. They induced a rapid decrease in the density of CD16 expression on NG and activated NG lysis in the blood with an intensity depending on the initial microbial concentration. Following 6 h incubation at concentrations of more than 105 mc/ml, flow cytometry detected the presence in the blood of a population of low density neutrophils characteristic of sepsis (Low Density Neutrophils with the CD63+CD16low phenotype), whose cells are prone to spontaneous autolysis (netosis).&#x0D; Conclusion. Under the conditions of ex vivo modeling of bacteremia, various strategies of human blood neutrophils in the implementation of the mechanisms of protection of the macroorganism from infection were evaluated, and the prospects of using the obtained information to identify individuals at high risk of developing staphylococcal sepsis were determined.

Human pathogenic bacteria on high-touch dry surfaces can be controlled by warming to human-skin temperature under moderate humidity.

Healthcare-associated infections have become a major health issue worldwide. One route of transmission of pathogenic bacteria is through contact with "high-touch" dry surfaces, such as handrails. Regular cleaning of surfaces with disinfectant chemicals is insufficient against pathogenic bacteria and alternative control methods are therefore required. We previously showed that warming to human-skin temperature affected the survival of pathogenic bacteria on dry surfaces, but humidity was not considered in that study. Here, we investigated environmental factors that affect the number of live bacteria on dry surfaces in hospitals by principal component analysis of previously-collected data (n = 576, for CFU counts), and experimentally verified the effect of warming to human-skin temperature on the survival of pathogenic bacteria on dry surfaces under humidity control. The results revealed that PCA divided hospital dry surfaces into four groups (Group 1~4) and hospital dry surfaces at low temperature and low humidity (Group 3) had much higher bacterial counts as compared to the others (Group 1 and 4) (p<0.05). Experimentally, warming to human-skin temperature (37°C with 90% humidity) for 18~72h significantly suppressed the survival of pathogenic bacteria on dry surfaces, such as plastic surfaces [p<0.05 vs. 15°C (Escherichia coli DH5α, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and blaNDM-5 E. coli)] or handrails [p<0.05 vs. 15~25°C (E. coli DH5α, S. aureus, P. aeruginosa, A. baumannii)], under moderate 55% humidity. Furthermore, intermittent heating to human-skin temperature reduced the survival of spore-forming bacteria (Bacillus subtilis) (p<0.01 vs. continuous heating to human-skin temperature). NhaA, an Na+/H+ antiporter, was found to regulate the survival of bacteria on dry surfaces, and the inhibitor 2-aminoperimidine enhanced the effect of warming at human-skin temperature on the survival of pathogenic bacteria (E. coli DH5α, S. aureus, A. baumannii) on dry surfaces. Thus, warming to human-skin temperature under moderate humidity is a useful method for impairing live pathogenic bacteria on high-touch surfaces, thereby helping to prevent the spread of healthcare-associated infections.

Effect of the Encapsulation Process on the Viability of Probiotics in a Simulated Gastrointestinal Tract Model Medium

The primary objective of this study was to investigate the survival rate of three species of encapsulated bacteria (Propionibacterium acidipropionicici, Propionibacterium freudenreichii, and Propionibacterium thoenii) in model solutions designed to simulate the acidity levels found within the human gastrointestinal tract. The capsules were prepared by extrusion from gelatin and sodium alginate in a 1:1 ratio on a laboratory encapsulator. The use of gelatin and sodium alginate was found to provide optimum characteristics suitable for encapsulation of live bacteria. Three strains of Propionibacterium asidirgorionici, Propionibacterium freudenreichii, and Propionibacterium thoenii were subjected to in vitro assay to evaluate their probiotic potential. The final cell survival rate of P. freudenreichii was 105 CFU/mL, indicating that this probiotic is sensitive to acidic medium. The viability of encapsulated probiotics was studied in a model medium simulating the gastrointestinal tract. It was found that alginate–gelatin capsules could provide protection to P. freudenreichii from gastric acid and lead to high levels of viable bacteria released in the intestine. Practical application: Encapsulation of Propionibacterium freudenreichii into alginate–gelatin capsules produced capsules capable of delivering live probiotic bacteria into the intestine.

Biofilm formation and development during the pyrite bioleaching of moderately thermophilic microorganisms

Bioleaching is a process that uses microorganisms to recover metals from intractable metal sulfide ores. Metal sulfide bioleaching is an interfacial process, and biofilm growth is crucial during the early phases. To study the interactions between microbes and minerals during the bioleaching of moderately thermophilic microorganisms, the formation and development of biofilms on pyrite coupons incubated in shake flasks for 40 days were evaluated. The biofilm biomass progressively increased as bioleaching proceeded. The most extensive biofilm was formed on day 30, when bacteria were attached to the mineral surface or submerged in extracellular polymeric substances. Confocal laser scanning microscopy indicated that the biofilm biomass of pyrite on day 40 was 6.55, 5.28, 3.17, and 1.70 times higher than that on days 5, 10, 20, and 30, respectively. Extracellular protein content exhibited an increasing trend throughout the process, whereas extracellular polysaccharides played a significant role during the early stages. Live/dead staining showed the highest mortality rate of 94% when cells were in contact with pyrite in the early stage, and the percentage of live bacteria increased in the later period. In the bioleaching environment, mature biofilms appeared to form relatively quickly after day 20. Real-time quantitative fluorescent quantitative analysis indicated that biofilm formation played an important role in defense against hostile external environments. In this study, biofilm formation and the associated RNA transcript numbers of moderately thermophilic microorganisms during pyrite bioleaching were investigated, contributing to the understanding of cell-mineral interactions.

Antibacterial Activity of a Lysin LysP53 against Streptococcus mutans.

Dental caries is a common disease affecting quality of life globally. In the present study, we found that a bacteriophage lysin LysP53 against Acinetobacter baumannii possesses selective activity on Streptococcus mutans, the main etiological agent of dental caries, even in low pH caries microenvironments, whereas only minor LysP53 activity was detected against Streptococcus sanguinis, Streptococcus oralis, and Streptococcus mitis. Testing activity against S. mutans planktonic cells showed that 4 μM LysP53 could kill more than 84% of S. mutans within 1 min in buffer with optimal pHs ranging from 4.0 to 6.5. Daily application of LysP53 on biofilms formed in BHI medium supplemented or not with sucrose could reduce exopolysaccharides, expression of genes related to acid resistance and adhesion, and the number of live bacteria in the biofilms. LysP53 treatment also showed similar effects as 0.12% chlorhexidine in preventing enamel demineralization due to S. mutans biofilms, as well as effective removal of S. mutans colonization of tooth surfaces in mice without observed toxic effects. Because of its selective activity against main cariogenic bacteria and good activity in low pH caries microenvironments, it is advantageous to use LysP53 as an active agent for preventing caries.

Prevention and Control of Human Salmonella enterica Infections: An Implication in Food Safety.

Salmonella is a foodborne zoonotic pathogen causing diarrhoeal disease to humans after consuming contaminated water, animal, and plant products. The bacterium is the third leading cause of human death among diarrhoeal diseases worldwide. Therefore, human salmonellosis is of public health concern demanding integrated interventions against the causative agent, Salmonella enterica. The prevention of salmonellosis in humans is intricate due to several factors, including an immune-stable individual infected with S. enterica continuing to shed live bacteria without showing any clinical signs. Similarly, the asymptomatic Salmonella animals are the source of salmonellosis in humans after consuming contaminated food products. Furthermore, the contaminated products of plant and animal origin are a menace in food industries due to Salmonella biofilms, which enhance colonization, persistence, and survival of bacteria on equipment. The contaminated food products resulting from bacteria on equipment offset the economic competition of food industries and partner institutions in international business. The most worldwide prevalent broad-range Salmonella serovars affecting humans are Salmonella Typhimurium and Salmonella Enteritidis, and poultry products, among others, are the primary source of infection. The broader range of Salmonella serovars creates concern over multiple strategies for preventing and controlling Salmonella contamination in foods to enhance food safety for humans. Among the strategies for preventing and controlling Salmonella spread in animal and plant products include biosecurity measures, isolation and quarantine, epidemiological surveillance, farming systems, herbs and spices, and vaccination. Other measures are the application of phages, probiotics, prebiotics, and nanoparticles reduced and capped with antimicrobial agents. Therefore, Salmonella-free products, such as beef, pork, poultry meat, eggs, milk, and plant foods, such as vegetables and fruits, will prevent humans from Salmonella infection. This review explains Salmonella infection in humans caused by consuming contaminated foods and the interventions against Salmonella contamination in foods to enhance food safety and quality for humans.

Commensal bacterial hybrid nanovesicles improve immune checkpoint therapy in pancreatic cancer through immune and metabolic reprogramming

Harnessing the immunomodulatory ability of the microbiota, such as fecal microbiota transplantation (FMT), has emerged as a promising strategy to improve cancer immunotherapy. However, the lack of standardization in fecal material formulation and safety concerns have hindered clinical application. To overcome these limitations, we developed a high-yielding method by hybridizing bacteria protoplast-derived membrane nanovesicles (PDNVs) from three colon bacteria strains that have been associated with favorable responses to immune checkpoint therapy, including Akkermansia muciniphila, Bifidobacterium longum, and Bifidobacterium breve. The resulting hybrid nanovesicles (HNVs) are composed mainly of cytoplasmic membrane proteins inherited from the originating bacteria but lack pyrogens such as lipopolysaccharide and lipoteichoic acid. Our study demonstrated that HNVs have superior targeting abilities to tumors and peripheral lymphoid organs, leading to greater capability in inducing innate immune activation, dendritic cell maturation and antigen presentation, as well as tumor microenvironment reprogramming. Combined with αPD-1 blockade therapy, HNVs efficiently inhibited the tumor growth in multiple pancreatic cancer mouse models, including Panc02 subcutaneous and liver metastatic models, and orthotopic KPC-Luc pancreatic cancer model. Mechanically, HNVs simultaneously activated the innate arm of immunity and inhibited tumor oxidative phosphorylation (OXPHOS) to reshape the tumor immune microenvironment for improved αPD-1 blockade therapy. Notably, HNVs administration gave rise to similar tumor regression rates to oral transfer of a mixture of live or inactivated bacteria during αPD-1 blockade therapy, but with fewer adverse effects such as diarrhea and colon-intestinal inflammation. Our findings present a stable, cost-effective, and safe alternative to live bacteria for regulating tumor microenvironment for improved cancer immunotherapy.

Comparison of automatic methods MALDI-TOF, VITEK2 and manual methods for the identification of intestinal microbial communities on the example of samples from alpacas (Vicugna pacos).

Universally, in microbiological diagnostics the detection of live bacteria is essential. Rapid identification of pathogens enables appropriate remedial measures to be taken. The identification of many bacteria simultaneously facilitates the determination of the characteristics of the accompanying microbiota and/or the microbiological complexity of a given environment. The effectiveness of the VITEK2 Compact automated microbial identification system and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS), analytical profile index (API) and Remel RapID tests were compared in identification of bacteria isolated from the alpaca gastrointestinal tract. Most isolates were Gram-positive, such as Bacillus cereus, Bacillus flexus, Bacillus licheniformis, Bacillus pumilus and Bacillus subtilis; Enterococcus faecium, Enterococcus gallinarum, Enterococcus hirae and Enterococcus casseliflavus; Staphylococcus aureus, Staphylococcus equorum, Staphylococcus lentus, Staphylococcus pseudintermedius and Staphylococcus sciuri; Paenibacillus amylolyticus; Cellulosimicrobium cellulans; Leuconostoc mesenteroides; Clostridium perfringens; Corynebacterium stationis, Corynebacterium xerosis, and Corynebacterium diphtheriae (the last only isolated manually by API Coryne and the VITEK2 system and Corynebacteria (CBC) card). Corynebacterium diphtheriae was misidentified by MALDI-TOF MS as Candida lipolytica (currently Yarrowia lipolytica). Gram-positive and Gram-variable Micrococcus luteus were also isolated. Gram-negative Enterobacter cloacae, Enterobacter gergoviae, Enterobacter hormaechei and Enterobacter ludwigii; E. coli; Klebsiella pneumoniae subsp. pneumoniae; Citrobacter braakii and Citrobacter freundii; Serratia liquefaciens, Serratia odorifera and Serratia marcescens; Morganella morganii subsp. morganii; Providencia alcalifaciens; Pseudomonas aeruginosa; Stenotrophomonas maltophilia; Moraxella osloensis; and Ochrobactrum intermedium were also found. The yeasts Candida albicans, Candida haemulonii and Candida ciferrii were also present. MALDI-TOF MS enabled the identification of pathogens and opportunistic pathogens from the alpaca gut which may represent a high risk to human and animal health.

Detection of immune effects of the Mannheimia haemolytica gamma irradiated vaccine in sheep.

Exposure to gamma rays from cobalt 60 (Co60) can induce a complete inactivation of Mannheimia haemolytica. The inactivated bacterial pathogen is a potential vaccine candidate for immunization of ruminants such as sheep. The subcutaneous administration of irradiated vaccine in a two-dose regimen (4.0 × 109 colony forming unit (CFU) per dose) results in no mortality in any of the vaccinated sheep during immunization and after subsequent challenge of the live bacteria of the same strain of M. haemolytica. A significant rise in serum IgG titer, detected through ELISA, is observed after the passage of two weeks from the inoculation of the first dose whereas, the peak of the mean serum antibody titer occurred after two weeks of booster dose. The vaccination does not bring significant change to the IFN-γ levels in serum. The bacterial challenge of the vaccinated sheep does not induce a further seroconversion relative to serum antibody titer. In conclusion, the vaccinated sheep are protected by the elevated IgG titer and increased levels of IL-4 (Th-2 response) compared to the non-vaccinated sheep. Radiation technology can provide the opportunity for mass production of immunologically safe vaccines against animal and zoonotic diseases. Ethics Approval by the National Research Center Ethics Committee (Trial Registration Number (TRN) no 13,602,023, 13/5/2023) was obtained.

Amidation of glutamate residues in mycobacterial peptidoglycan is essential for cell wall cross-linking.

Mycobacteria assemble a complex cell wall with cross-linked peptidoglycan (PG) which plays an essential role in maintenance of cell wall integrity and tolerance to osmotic pressure. We previously demonstrated that various hydrolytic enzymes are required to remodel PG during essential processes such as cell elongation and septal hydrolysis. Here, we explore the chemistry associated with PG cross-linking, specifically the requirement for amidation of the D-glutamate residue found in PG precursors. Synthetic fluorescent probes were used to assess PG remodelling dynamics in live bacteria. Fluorescence microscopy was used to assess protein localization in live bacteria and CRISPR-interference was used to construct targeted gene knockdown strains. Time-lapse microscopy was used to assess bacterial growth. Western blotting was used to assess protein phosphorylation. In Mycobacterium smegmatis, we confirmed the essentiality for D-glutamate amidation in PG biosynthesis by labelling cells with synthetic fluorescent PG probes carrying amidation modifications. We also used CRISPRi targeted knockdown of genes encoding the MurT-GatD complex, previously implicated in D-glutamate amidation, and demonstrated that these genes are essential for mycobacterial growth. We show that MurT-rseGFP co-localizes with mRFP-GatD at the cell poles and septum, which are the sites of cell wall synthesis in mycobacteria. Furthermore, time-lapse microscopic analysis of MurT-rseGFP localization, in fluorescent D-amino acid (FDAA)-labelled mycobacterial cells during growth, demonstrated co-localization with maturing PG, suggestive of a role for PG amidation during PG remodelling and repair. Depletion of MurT and GatD caused reduced PG cross-linking and increased sensitivity to lysozyme and β-lactam antibiotics. Cell growth inhibition was found to be the result of a shutdown of PG biosynthesis mediated by the serine/threonine protein kinase B (PknB) which senses uncross-linked PG. Collectively, these data demonstrate the essentiality of D-glutamate amidation in mycobacterial PG precursors and highlight the MurT-GatD complex as a novel drug target.

Enhancing the Hydrophobicity and Antibacterial Properties of SiCN-Coated Surfaces with Quaternization to Address Peri-Implantitis.

Peri-implantitis is a major cause of dental implant failure. This disease is an inflammation of the tissues surrounding the implant, and, while the cause is multi-factorial, bacteria is the main culprit in initiating an inflammatory reaction. Dental implants with silicon carbonitride (SiCN) coatings have several potential advantages over traditional titanium implants, but their antibacterial efficiency has not yet been evaluated. The purpose of this study was to determine the anti-bacterial potential of SiCN by modifying the surface of SiCN-coated implants to have a positive charge on the nitrogen atoms through the quaternization of the surface atoms. The changes in surface chemistry were confirmed using contact angle measurement and XPS analysis. The modified SiCN surfaces were inoculated with Streptococcus mutans (S. mutans) and compared with a silicon control. The cultured bacterial colonies for the experimental group were 80% less than the control silicon surface. Fluorescent microscopy with live bacteria staining demonstrated significantly reduced bacterial coverage after 3 and 7 days of incubation. Scanning electron microscopy (SEM) was used to visualize the coated surfaces after bacterial inoculation, and the mechanism for the antibacterial properties of the quaternized SiCN was confirmed by observing ruptured bacteria membrane along the surface.

Biofilm Removal from In Vitro Narrow Geometries Using Single and Dual Pulse Er:YAG Laser Photoacoustic Irrigation.

The disinfection and removal of biofilm from titanium dental implants remains a great challenge in oral medicine. Here we present results of novel photoacoustic irrigation laser modalities for biofilm removal in model geometries mimicking the peri-implant pocket. The efficacy of single pulse (Er:YAG-SSP) and dual pulse (Er:YAG-AutoSWEEPS) photoacoustic irrigation modalities were determined for Enterococcus faecalis biofilm decontamination from titanium surfaces in narrow cylindrical and square gap geometries. The density of bacteria as well as the number of live bacteria were determined prior and after different photoacoustic treatments. Both SSP and AutoSWEEPS photoacoustic irrigation techniques removed at least 92% of biofilm bacteria during the 10 s photoacoustic treatment. The effectiveness of cleaning was better in the narrow square gap geometry compared to the cylindrical geometry. The dual pulse Er:YAG-AutoSWEEPS photoacoustic irrigation showed better results compared to SSP modality. No chemical adjuvants were needed to boost the effectiveness of the photoacoustic irrigation in the saline solution. The results imply that photoacoustic irrigation is an efficient cleaning method for debridement and decontamination in narrow geometries and should be considered as a new therapeutic option for the treatment of peri-implant diseases.

Design of an anticorrosion/bactericidal dual functional organic coating based on the slippery liquid-infused porous surface

In this work, a long-lasting slippery liquid-infused porous surface (SLIPS) was fabricated on an organic coating to achieve both anticorrosion and antibacterial functions. Phenyl-modified etched basalt (PEB) scales were produced to construct micro-nano capillary structures and generate π electrons, which facilitated the retention of lubricant on the surface when assembled onto an epoxy resin layer. Plant oil was selected as a lubricant to introduce numerous –COOH, and was robustly trapped on the surface by π-COOH interactions, which enhanced the durability of the SLIPS coating. Based on the electrochemical tests, the coating displayed superior anticorrosion performance with |Z|0.01Hz values of 1.99 × 1010 Ω·cm2 after 14 days of immersion, which benefited from excellent barrier effect and liquid repellency. The zeta potential result proved that the corrosion resistance of SLIPS coating was further improved by the electrostatic repulsion. In addition, the antibacterial experiment results demonstrated only 0.32% of biofilm coverage and no live bacteria after 3 days of immersion, which implied the dual mechanisms of SLIPS coating in killing bacteria and inhibiting bacterial adhesion. The SLIPS coating with excellent lubricant retention and promising anticorrosion/bactericidal performance possesses tremendous application potential in marine protection.

Dynamic monitoring of oscillatory enzyme activity of individual live bacteria via nanoplasmonic optical antennas

Dynamic monitoring of oscillatory enzyme activity of individual live bacteria via nanoplasmonic optical antennas