Anti-Biofilm Activity of Cannabigerol against Streptococcus mutans

Streptococcus mutans is a common cariogenic bacterium in the oral cavity involved in plaque formation. Previous studies showed that Cannabigerol (CBG) has bacteriostatic and bacteriocidic activity against S. mutans. The aim of the present study was to study its effect on S. mutans biofilm formation and dispersion. S. mutans was cultivated in the presence of CBG, and the resulting biofilms were examined by CV staining, MTT assay, qPCR, biofilm tracer, optical profilometry, and SEM. Gene expression was determined by real-time qPCR, extracellular polysaccharide (EPS) production was determined by Congo Red, and reactive oxygen species (ROS) were determined using DCFH-DA. CBG prevented the biofilm formation of S. mutans shown by reduced biofilm biomass, decreased biofilm thickness, less EPS production, reduced DNA content, diminished metabolic activity, and increased ROS levels. CBG altered the biofilm roughness profile, resulting in a smoother biofilm surface. When treating preformed biofilms, CBG reduced the metabolic activity of S. mutans with a transient effect on the biomass. CBG reduced the expression of various genes involved in essential metabolic pathways related to the cariogenic properties of S. mutans biofilms. Our data show that CBG has anti-biofilm activities against S. mutans and might be a potential drug for preventive treatment of dental caries.

Thermal and chemical disinfection of water and biofilms: only a temporary effect in regard to the autochthonous bacteria

Thermal and chemical disinfection of technical water systems not only aim at minimizing the level of undesired microorganisms, but also at preventing excessive biofouling, clogging and interference with diverse technical processes. Typically, treatment has to be repeated in certain time intervals, as the duration of the effect is limited. The transient effect of disinfection was demonstrated in this study applying different treatments to water and biofilms including heat, chlorination, a combination of hydrogen peroxide and peracetic acid and monochloramine. Despite the diverse treatments, the reduction in live bacteria was followed by regrowth in all cases, underlining the universal validity of this phenomenon. The study shows that autochthonous bacteria could reach the concentrations given prior to treatment. The reason is seen in the nutrient concentration that has not changed and that forms the basis for regrowth. Nutrients are released by disinfection from lysed cells or are still fixed in dead biomass that is subsequently scavenged by necrotrophic growth. Treatment cycles therefore only provide a transient reduction of water microbiology if nutrients are not removed. When aiming at greater sustainability of the effect, biocidal treatment has to be equally concerned about nutrient removal by subsequent cleaning procedures as about killing efficiency.

The transient effect of a peer support intervention to improve adherence among adolescents and young adults failing antiretroviral therapy in Harare, Zimbabwe: a randomized control trial

Background Adolescents and young adults living with HIV in sub Saharan Africa are at high risk of poor adherence to antiretroviral therapy (ART) and virologic failure (VF). Methods We conducted a randomized control trial among adolescents and young adults on ART with VF to assess the effectiveness of a community-based peer support intervention aimed at improving VF. Viral load (VL) levels were obtained at 12, 24 and 36 weeks. A subset of the participants had baseline HIV drug resistance (HIVDR) genotyped using Sanger sequencing. Results The participants’ median (interquartile range (IQR)) age was 18.1 (IQR: 15.1–20.0) years and half (50.5%, n = 107) were male. At week 24, the proportion of subjects with a detectable viremia was significantly lower in the intervention arm than in the standard of care (SOC) arm (76.0% (n = 79) vs. 89.0% (n = 96), p = 0.013). At Week 36, there remained a difference in the proportion of subjects with a detectable VL between the intervention arm (68.3%, n = 71) and SOC arm (79.6%, n = 86), which was trending towards statistical significance (p = 0.059). There was no difference in the probability of having a detectable VL over time between the intervention and SOC groups (adjusted odds ratio: 1.14, p = 0.439). Baseline HIVDR was observed in 44.0% of the participants in the intervention and 56.0% in the SOC group (p = 0.146). Conclusion A transient effect of the peer support intervention in improving VF was observed among adolescents and young people failing ART. Trial registration: This study is registered with www.clinicaltrials.gov under the reference number: NCT02833441

Volume Resistivity of Viton Polymer under Thermal Aging

This study examines the influence of various electrical parameters on the volume resistivity of the Viton fluoroelastomer. The transient current, the temperature dependence of volume resistivity, the voltage dependence of resistivity, and the surface morphology of Viton insulators are investigated for new and aged specimens. An accelerated aging process has been employed in order to simulate the natural aging of insulators in service. A detailed comparison between the new and aged samples is presented. The transient effect, which is a challenge to the resistivity measurement of insulators, has been investigated. The first 60 s of the resistivity measurement test showed a significant influence from the transient effect and should be excluded from the data. The volume resistivity of both new and aged samples decreased when the temperature increased. However, the resistivity of the aged sample was lower than the new one at all tested temperatures. When the temperature increased from 35 to 190 °C, resistivity decreased from 4.77 × 1010 to 6.99 × 108 Ω-cm for the new sample and from 2.6 × 1010 to 6.68 × 108 Ω-cm for the aged sample under 500 V. Additionally, the results from this study showed that the volume resistivity is inversely proportional to the applied voltage. Finally, scanning electron microscope (SEM) micrographs/images allowed us to closely examine the surface morphology of new and aged Viton samples. The surface of aged samples has been recognized with higher surface roughness and more significant surface cracks leading to poor performance under high voltage applications.