Antibacterial Activity Evaluation of ZnO, CuO, and TiO2 Nanoparticles in Solution and Thin Films.

This chapter introduces unique methodology of antibacterial activity evaluation of nanoparticles in both solution and thin films. Nanoparticles of ZnO, TiO2, and CuO are synthesized via the sol-gel method. Antibacterial tests are carried out against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria using disk diffusion and bioluminescence. To perform antibacterial tests on thin films and to overcome bacterial strains recuperation on the supports, a new method of bacterial detaching from the slides is developed based on French standard NF EN 14561.

Impact of sampling and DNA extraction methods on skin microbiota assessment.

The skin microbiota is characterized by high intra- and inter-variability among individuals, due to a multitude of intrinsic and extrinsic parameters such as genetics, lifestyles or pollution. This variability may be heightened due to sampling method as the skin is a multilayer organ and its outermost layer consists of dead cells. In order to investigate this biological variability in a reproducible way, we studied how sampling procedure and DNA extraction methods influence the qualitative and quantitative gathering of bacterial communities. Here, we tested a new sampling procedure that consists in exerting a slight abrasion (scrubbing) on the skin prior to swabbing and extracting DNA in order to remove squames and access deeper ecological niches. Scrubbed and non-scrubbed samples were collected from a panel of six volunteers, and four DNA extraction methods were performed on the samples. The abundance, diversity and structure of the bacterial communities were measured using qPCR technics and 16S rDNA gene-metabarcoding. Bacterial community abundance was significantly impacted by the DNA extraction method (in favor of a method designed for tissues) but not by sampling procedure, as scrubbing does not increase bacterial biomass gathered. Bacterial α- and ß-diversities were both affected by DNA extraction methods and sampling procedure. Scrubbing reveals different microbial composition by gathering bacteria living in deeper skin layer, resulting in a lower intra-personal variability. The taxonomic analysis showed that more bacteria belonging to anaerobes groups were present in scrubbed samples. We conclude that DNA extraction methods designed for tissue are not necessarily associated with high qualitative efficiency and slight scrubbing prior DNA extraction reduces intrapersonal variability and give access to a new microbial diversity.

Antibacterial activity of ZnO and CuO nanoparticles against gram positive and gram negative strains.

This is a report on the antibacterial activity of ZnO and CuO nanoparticles synthesized via sol-gel method. The studies were performed on Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria using disc and well diffusion methods, bioluminescence and optical density analysis. The results show a strong decline of bacterial strains after a short contact with nanoparticles. The modelling allowed clarifying the bacterial sensitivity of toxic agents at different stages of their population evolution kinetics. It was concluded that the bacterial suppression is most effective at the exponential growth phase while it is of a lower effectiveness at the lag and stationary phases. The CuO and ZnO nanoparticles showed comparable effectiveness at the exponential growth phase. In the same time, ZnO was almost inactive at the lag phase and of lower effectiveness at the stationary phase, at which CuO conserved a significant activity.

Does the intestinal bifidobacterial colonisation affect bacterial translocation?

The aim of this work was to investigate the possible role of the intestinal anaerobic flora (especially bifidobacteria) in regulating bacterial translocation (BT) which can be defined as the passage of intestinal microbes through the mucosa to internal organs. Default in BT regulation concurs with pathogenesis of sepsis in various human conditions, such as acute pancreatitis, cirrhosis, necrotising enterocolitis or multiple organ failure. The intestinal flora was studied in human flora associated mice (HF mice) and BT was quantified in Peyer's patches (PP), blood, spleen, liver and lungs. HF mice displayed a heterogenic intestinal colonisation with bifidobacteria. High colonisation of both caecum and colon by bifidobacteria led to a poorer bacterial contamination of blood, liver and lungs. Moreover, ileal, caecal and colonic bifidobacterial counts negatively correlated with the bacterial dissemination (number of contaminated organs per mouse). In contrast, Bacteroides fragilis group counts positively correlated with bacteraemia, lungs contamination or bacterial dissemination. Additionally, clostridia localised in the colon affected bacterial uptake by PP and lungs contamination as indicated by positive correlations between bacterial populations in these respective locations. These results indicate that bifidobacteria, when established in high counts, reduced BT to liver, blood and lungs, whereas B. fragilis group favoured the bacterial passage. Clostridia established in the distal ileum also seemed to favour BT to lungs. The manipulation of the bacterial flora to optimise the regulatory effect on BT should therefore focus on the selective promotion of bifidobacteria and avoid an increase in potentially detrimental populations such as B. fragilis group and clostridia.