Background Dental procedures often produce aerosol and splatter which have the potential to transmit pathogens such as SARS‐CoV‐2. The existing literature is limited. Objective(s) To develop a robust, reliable and valid methodology to evaluate distribution and persistence of dental aerosol and splatter, including the evaluation of clinical procedures. Methods Fluorescein was introduced into the irrigation reservoirs of a high‐speed air‐turbine, ultrasonic scaler and 3‐in‐1 spray, and procedures were performed on a mannequin in triplicate. Filter papers were placed in the immediate environment. The impact of dental suction and assistant presence were also evaluated. Samples were analysed using photographic image analysis, and spectrofluorometric analysis. Descriptive statistics were calculated and Pearson’s correlation for comparison of analytic methods. Results All procedures were aerosol and splatter generating. Contamination was highest closest to the source, remaining high to 1–1.5 m. Contamination was detectable at the maximum distance measured (4 m) for high‐speed air‐turbine with maximum relative fluorescence units (RFU) being: 46,091 at 0.5 m, 3,541 at 1.0 m, and 1,695 at 4 m. There was uneven spatial distribution with highest levels of contamination opposite the operator. Very low levels of contamination (≤0.1% of original) were detected at 30 and 60 minutes post procedure. Suction reduced contamination by 67–75% at 0.5–1.5 m. Mannequin and operator were heavily contaminated. The two analytic methods showed good correlation ( r =0.930, n =244, p <0.001). Conclusion Dental procedures have potential to deposit aerosol and splatter at some distance from the source, being effectively cleared by 30 minutes in our setting.

The acquisition of genes by horizontal transfer can impart entirely new biological functions and provide an important route to major evolutionary innovation. Here we have used ancient gene reconstruction and functional assays to investigate the impact of a single horizontally transferred nucleotide transporter into the common ancestor of the Microsporidia, a major radiation of intracellular parasites of animals and humans. We show that this transporter provided early microsporidians with the ability to steal host ATP and to become energy parasites. Gene duplication enabled the diversification of nucleotide transporter function to transport new substrates, including GTP and NAD+, and to evolve the proton-energized net import of nucleotides for nucleic acid biosynthesis, growth and replication. These innovations have allowed the loss of pathways for mitochondrial and cytosolic energy generation and nucleotide biosynthesis that are otherwise essential for free-living eukaryotes, resulting in the highly unusual and reduced cells and genomes of contemporary Microsporidia.

AbstractBackgroundDental procedures often produce aerosol and splatter which are potentially high risk for spreading pathogens such as SARS-CoV-2. The existing literature is limited.Objective(s)To develop a robust, reliable and valid methodology to evaluate distribution and persistence of dental aerosol and splatter, including the evaluation of clinical procedures.MethodsFluorescein was introduced into the irrigation reservoirs of a high-speed air-turbine, ultrasonic scaler and 3-in-1 spray and procedures performed on a mannequin in triplicate. Filter papers were placed in the immediate environment. The impact of dental suction and assistant presence were also evaluated. Samples were analysed using photographic image analysis, and spectrofluorometric analysis. Descriptive statistics were calculated and Pearson’s correlation for comparison of analytic methods.ResultsAll procedures were aerosol and splatter generating. Contamination was highest closest to the source, remaining high to 1-1.5 m. Contamination was detectable at the maximum distance measured (4 m) for high-speed air-turbine with maximum relative fluorescence units (RFU) being: 46,091 at 0.5 m, 3,541 at 1.0 m, and 1,695 at 4 m. There was uneven spatial distribution with highest levels of contamination opposite the operator. Very low levels of contamination (≤0.1% of original) were detected at 30 and 60 minutes post procedure. Suction reduced contamination by 67-75% at 0.5-1.5 m. Mannequin and operator were heavily contaminated. The two analytic methods showed good correlation (r=0.930, n=244, p<0.001).ConclusionDental procedures have potential to deposit aerosol and splatter at some distance from the source, being effectively cleared by 30 minutes in our setting.

Mitosomes are highly reduced forms of mitochondria which have lost two of the ‘defining’ features of the canonical organelle, the mitochondrial genome, and the capacity to generate energy in the form of ATP. Mitosomes are found in anaerobic protists and obligate parasites and, in most of the studied organisms, have a conserved function in the biosynthesis of iron-sulfur clusters (ISC) that are indispensable cofactors of many essential proteins. The genomes of some mitosome-bearing human pathogenic Microsporidia encode homologues of an alternative oxidase (AOX). This mitochondrial terminal respiratory oxidase is absent from the human host, and hence is a potential target for the development of new antimicrobial agents. Here we present experimental evidence for the mitosomal localization of AOX in the microsporidian Trachipleistophora hominis and demonstrate that it has an important role during the parasite’s life cycle progression. Using a recently published methodology for synchronising T. hominis infection of mammalian cell lines, we demonstrated specific inhibition of T. hominis early meront growth and replication by an AOX inhibitor colletochlorin B. Treatment of T. hominis-infected host cells with the drug also inhibited re-infection by newly formed dispersive spores. Addition of the drug during the later stages of the parasite life cycle, when our methods suggest that AOX is not actively produced and T. hominis mitosomes are mainly active in Fe/S cluster biosynthesis, had no inhibitory effects on the parasites. Control experiments with the AOX-deficient microsporidian species Encephalitozoon cuniculi, further demonstrated the specificity of inhibition by the drug. Using the same methodology, we demonstrate effects of two clinically used anti-microsporidian drugs albendazole and fumagillin on the cell biology and life cycle progression of T. hominis infecting mammalian host cells. In summary, our results reveal that T. hominis mitosomes have an active role to play in the progression of the parasite life cycle as well as an important role in the biosynthesis of essential Fe/S clusters. Our work also demonstrates that T. hominis is a useful model for testing the efficacy of therapeutic agents and for studying the physiology and cell biology of microsporidian parasites growing inside infected mammalian cells.

No abstract