Modification of polyester filters with synthesized copper nanoparticles for use as biocide in a real environment.

Antimicrobial air filtration techniques have recently been widely studied to enhance indoor air quality and mitigate hazardous airborne microorganisms. Here, CuNPs were incorporated into a commercial polyester fiber surface and Scanning Mobility Particle Sizer was used to measure the adherence between fibers and nanoparticles. An acid pretreatment previous CuNP incorporation was effective against the particle release and enhanced the adhesion between particle and fiber. CuNP was a mixture of Cu0 and Cu2O with a diameter size of 90 nm (SEM micrographs). The permeability of the filter was low, in order of 10-9 m2. The activity against pathogens was tested in loco in a real environment using a filtration prototype apparatus. It was observed that the presence of CuNP mitigated the fungi and bacteria growth not only on the surface but also reduced microbe concentrations after passing through the filter. These results show that CuNP can be used as an inhibitor of various microorganisms, making them a good alternative for indoor environments to control indoor air quality.

Broad-spectrum bactericidal activity of a new bioactive grafting material (F18) against clinically important bacterial strains.

Infection is the most relevant surgical complication in implant or grafting procedures. Osteomyelitis and other chronic conditions pose a constant challenge in current medical practice. In this context, a grafting biomaterial that possesses antibacterial properties combined with bioactivity could have great clinical impact. Researchers at the Vitreous Materials Laboratory (LaMaV-UFSCar) recently developed a glass composition, named F18, that presents an improved workability range combined with high bioactivity. With F18, one can easily manufacture complex shapes, such as scaffolds, continuous fibres and coat implants. This biomaterial has proven to be a viable alternative for bone and skin regeneration in in vivo tests, however its antimicrobial properties have not been explored. Hence, the purpose of this study was to systematically investigate the antibacterial activity of F18 in powder and fibre forms according to the JIS Z 2801:2010 standard. Whether incorporation of silver into F18 glass could impact its antimicrobial activity was also evaluated. Four clinically relevant Gram-positive and Gram-negative pathogenic bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa) were used in this study. In both powder and fibre forms, F18 presented extremely efficient bactericidal activity against all strains tested, eliminating virtually 100% of the bacterial cells after 24 h. Kinetic tests showed that silver doping further increased the bactericidal activity, leading to S. aureus eradication in only 30 min after incubation. Both doped and non-doped glasses demonstrated very high bactericidal activity, making F18 a promising infection-preventing alternative for bone and wound regeneration in clinical practice.

The influence of experimental conditions on the final result of photoinhibition of Staphylococcus aureus.

BACKGROUND: By and large, phototherapies are a promising approach to promote inactivation of microorganisms using light exposure, providing an effective alternative to control multidrug-resistant bacterial infections. Considering this, intercomparison between experiments is vitally important. Most experiments are performed using multiwell plates in which the volume of the culture medium is not standardized. In such cases, light attenuation and the distance it travels, which also depends on the volume and vessel geometry, can lead to different results. This study investigated how the different volumes imply different depths that light will have to travel through in this volume and the relation of this parameter with the result that will be obtained. METHODS: Staphylococcus aureus was exposed to 460nm light with 50, 100 and 200J/cm2, in 100, 200, 500 and 1000µL of inocula in a 24-well plate to investigate pure light inactivation. RESULTS: The literature suggests that fluence is the most important light parameter to obtain a high eradication of microbial cells in phototherapies. Our results show evidence that different geometrical configurations, taking into account the volume of the vessels, clearly affect the in vitro results, risking misinterpretation of dosimetry studies. Effects, such as dose distribution and decantation, are discussed throughout the paper. CONCLUSION: The outcome strongly depends on the volume and vessel geometry used. This study aims to encourage the standardization of phototherapies in vitro in general.

Lignocellulolytic enzymes and bacteria associated with the digestive tracts of Stenochironomus (Diptera: Chironomidae) larvae.

We analyzed the digestive activity of the enzymes that digest cellulose and hemicellulose and the bacterial community that is capable of hydrolyzing wood compounds in the digestive tracts of Stenochironomus (Diptera: Chironomidae) larvae, which are miners of decomposing submerged tree and bush branches. Based on quantification of reducing sugars, these larvae have a limited capacity for cellulose degradation but a good capacity for xylan hydrolysis. We isolated 31 types of colonies from two larval morphotypes, of which 19 tested positive for the capacity to hydrolyze at least one of the four substrates that were used as the main carbon source in the culture media. Their woody compound degradation capacity was assessed using colorimetric tests. The bacteria were identified by the analysis of the 16S rRNA gene. None of the bacteria were capable of degrading lignin. The genus Pseudomonas had the greatest species richness; Bacillus spp exhibited the greatest capacity for degrading the different substrates, and Sphingobium was found in both morphotypes. Microorganisms participate in the degradation of wood consumed by Stenochironomus larvae. This is the first report of lignocellulolytic bacteria and enzymes in the digestive tracts of mining chironomids.