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Four novel selenite-reducing bacterial strains Achromobacter agilis, Lysinibacillus xylanticus, Lysinibacillus macroides, and Citrobacter freundi were isolated from industrial waste-contaminated soils in the coastal region of Chennai, India. The isolates reduced selenite and synthesized biogenic selenium nanoparticles (BioSeNPs) using extracellular metabolites. Nuclear magnetic resonance (NMR) and High-performance liquid chromatography (HPLC) data of the extracellular metabolites indicated that Nicotinamide adenine dinucleotide (NADH) and phenazine carboxylic acid (PCA) were involved in the synthesis. Culture ages, pH, initial selenite concentration with extracellular cell-free extracts mixing ratio, and reaction times were optimized using the classical method to synthesize BioSeNPs. Transmittance electron microscopy (TEM), High-resolution scanning electron microscopy (HR-SEM), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis confirmed the synthesized BioSeNPs are spherical and homogenous, with a 2–14 nm size range. BioSeNPs from Lysinibacillus xylanticus and Achromobacter agilis showed strong antibacterial effects against the pathogens Escherichia coli and Staphylococcus aureus even at low concentrations (40 µg/mL). BioSeNPs from Lysinibacillus macroides removed the pathogen’s biofilm at 20 µg/mL. This study demonstrated that the findings could aid in investigating cost-effective BioSeNPs-based wastewater treatment technologies for removing pathogenic drug-resistant bacteria.Highlights: BioSeNPs synthesized from Achromobacter agilis, Lysinibacillus xylanticus, Lysinibacillus macrolides, and Citrobacter freundi reduced selenite by 94% in 24 hours. The extracellular cell-free extract of the isolates, containing NADH and PCA, successfully synthesized spherical and homogeneous selenium nanoparticles under the optimized conditions. BioSeNPs removed 85% of the biofilm at 20 μg/mL with 99% antibacterial efficacy against Staphylococcus aureus and Escherichia coli. [ABSTRACT FROM AUTHOR]

Biofilm formation and growth is a significant concern for water treatment professionals, as it can lead to the contamination of water systems and pose a threat to public health. Biofilms are complex communities of microorganisms that adhere to surfaces and are embedded in an extracellular matrix of polysaccharides and proteins. They are notoriously difficult to control, as they provide a protective environment for bacteria, viruses, and other harmful organisms to grow and proliferate. This review article highlights some of the factors that favor biofilm growth, as well as various strategies for controlling biofilm in water systems. Adopting the best available technologies, such as wellhead protection programs, proper distribution system maintenance, and filtration and disinfection, can prevent the formation and growth of biofilms in water systems. A comprehensive and multi-faceted approach to biofilm control can reduce the occurrence of biofilms and ensure the delivery of high-quality water to consumers. [ABSTRACT FROM AUTHOR]

Objectives: To compare ultrasonic scaler prototypes based on a planar piezoelectric transducer with different working frequencies featuring a titanium (Ti-20, Ti-28, and Ti-40) or stainless steel (SS-28) instrument, with a commercially available scaler (com-29) in terms of biofilm removal and reformation, dentine surface roughness and adhesion of periodontal fibroblasts. Materials and methods: A periodontal multi-species biofilm was formed on specimens with dentine slices. Thereafter specimens were instrumented with scalers in a periodontal pocket model or left untreated (control). The remaining biofilms were quantified and allowed to reform on instrumented dentine slices. In addition, fibroblasts were seeded for attachment evaluation after 72 h of incubation. Dentine surface roughness was analyzed before and after instrumentation. Results: All tested instruments reduced the colony-forming unit (cfu) counts by about 3 to 4 log10 and the biofilm quantity (each p < 0.01 vs. control), but with no statistically significant difference between the instrumented groups. After 24-hour biofilm reformation, no differences in cfu counts were observed between any groups, but the biofilm quantity was about 50% in all instrumented groups compared to the control. The attachment of fibroblasts on instrumented dentine was significantly higher than on untreated dentine (p < 0.05), with the exception of Ti-20. The dentine surface roughness was not affected by any instrumentation. Conclusions: The planar piezoelectric scaler prototypes are able to efficiently remove biofilm without dentine surface alterations, regardless of the operating frequency or instrument material. Clinical relevance: Ultrasonic scalers based on a planar piezoelectric transducer might be an alternative to currently available ultrasonic scalers. [ABSTRACT FROM AUTHOR]

Objectives: Low-frequency, low-intensity ultrasound is commonly utilized in various dental research fields to remove biofilms from surfaces, but no clear recommendation exists in dental studies so far. Therefore, this study aims to optimize the sonication procedure for the dental field to efficiently detach bacteria while preserving viability. Materials and methods: Initial biofilm was formed in vivo on bovine enamel slabs (n = 6) which were worn by four healthy participants for 4 h and 24 h. The enamel slabs covered with biofilm were then ultrasonicated ex vivo for various time periods (0, 1, 2, 4, 6 min). Colony-forming units were determined for quantification, and bacteria were identified using MALDI-TOF. Scanning electron microscopic images were taken to also examine the efficiency of ultrasonications for different time periods. Results: Ultrasonication for 1 min resulted in the highest bacterial counts, with at least 4.5-fold number compared to the non-sonicated control (p < 0.05). Most bacteria were detached within the first 2 min of sonication, but there were still bacteria detached afterwards, although significantly fewer (p < 0.0001). The highest bacterial diversity was observed after 1 and 2 min of sonication (p < 0.03). Longer sonication periods negatively affected bacterial counts of anaerobes, Gram-negative bacteria, and bacilli. Scanning electron microscopic images demonstrated the ability of ultrasound to desorb microorganisms, as well as revealing cell damage and remaining bacteria. Conclusions: With the use of low-frequency, low-intensity ultrasound, significantly higher bacterial counts and diversity can be reached. A shorter sonication time of 1 min shows the best results overall. Clinical relevance: This standardization is recommended to study initial oral biofilms aged up to 24 h to maximize the outcome of experiments and lead to better comparability of studies. [ABSTRACT FROM AUTHOR]

Objectives: Whereas the key role of subgingival instrumentation in periodontal therapy is well known, the influence of operators' experience/training with different devices on treatment results is yet uncertain. Therefore, we assessed untrained undergraduate students, working on manikins, as to how effectively they learn to use curettes (GRA) and sonic scalers (AIR); hypothesizing that AIR will result in higher relative cleaning efficacy (RCE) than GRA. Material and methods: Before baseline evaluation (T0), 30 operators (9 males, 21 females) received a 2-h theoretical lesson for both instruments, followed by a 12-week period with a weekly digitized training program for 45 min. During three sessions (T1–T3), the operators had to instrument six equivalent test teeth with GRA and AIR. At T0–T3, treatment time, proportion of removed simulated biofilm (RCE-b), and hard deposits (RCE-d) were measured. Results: At T0, RCE-b was in mean(SD) 64.18(25.74) % for GRA, 62.25(26.69) % for AIR; (p = 0.172) and RCE-d 85.48(12.32) %/ 65.71(15.27) % (p < 0.001). At T3, operators reached highest RCE-b in both groups (GRA/AIR 71.54(23.90) %/71.75(23.05)%; p = 0.864); RCE-d GRA/AIR: 84.68(16.84) %/77.85(13.98) %; p < 0.001). Both groups achieved shorter treatment times after training. At T3, using curettes was faster (GRA/AIR 16.67(3.31) min/19.80(4.52) min; p < 0.001). Conclusions: After systematic digitized training, untrained operators were able to clean 70% of the root surfaces with curettes and sonic scalers. Clinical relevance: It can be concluded that a systematic digitized and interactive training program in manikin heads is helpful in the training of root surface debridement. [ABSTRACT FROM AUTHOR]

Various methods have been reported to quantify total biofilm or different components of biofilm; however, these methods are often confusedly used, leading to discrepancies and misleading results. In this study, different methods for quantification of biofilm, including those for total biomass, total amount of bacterial cells, viable cell number, and amount of extracellular polymeric substances, were systematically compared in microtiter plates. To evaluate which method is suitable for assessment of biofilm removal and for bacterial killing, biofilm samples were treated with various cleaners possessing removing and/or killing capacities. It was found that most of the methods tested in this study in general exhibited high reproducibility and repeatability. Crystal Violet staining was a simple but reliable method for total biomass quantification. Total bacteria cell numbers could be reliably quantified by the fluorescent DNA-binding dye Acridine Orange. Viable cells could be quantified by either an ATP-based assay or a proliferation assay. Both of these viability methods showed a broad detection range and led to precise measurement. For quantification of proteins in the biofilm, staining with fluorescein isothiocyanate was most suitable. Furthermore, it was revealed that a combination of different methods is required to determine if a cleaner kills or removes biofilm. [ABSTRACT FROM AUTHOR]

Many techniques to inactivate or remove biofilms in a wide variety of applications have been developed. Most of these techniques have been applied to biofilms at their initial stage of growth, since they are generally difficult to eradicate once established. The removal of established biofilms has received relatively little attention. In this paper, we report the effectiveness of periodic jets of carbon dioxide aerosols (a mixture of solid and gaseous CO) to remove Escherichia coli (XL1-blue) biofilms of different ages (up to 3 weeks) on silicon surfaces. The biofilms were not immersed in liquids after growth/rinsing and were treated with the CO aerosols. The CO aerosols were generated by the adiabatic expansion of high-pressure CO2 gas through a nozzle. The surface area of the biofilms was measured from fluorescent images before and after applying the aerosols for 11, 20, and 30 cycles (each cycle: 8 sec), to compute the removal efficiency. The removal efficiencies decreased with increasing growth time and for the 3-week-old biofilms, they ranged from 91.5 to 99.6% within 4 min. This technique was highly effective for removing both fresh and old biofilms, but some of the biofilm debris such as growth media remained. Further, this CO aerosol technique was compared with other removal techniques. [ABSTRACT FROM AUTHOR]