The abundance of the potential pathogen Staphylococcus hominis in the air microbiome in a dental clinic and its susceptibility to far-UVC light.

The dental clinic air microbiome incorporates microbes from the oral cavity and upper respiratory tract (URT). This study aimed to establish a reliable methodology for air sampling in a dental clinic setting and quantify the abundance of culturable mesophilic aerobic bacteria present in these samples using regression modeling. Staphylococcus hominis, a potentially pathogenic bacterium typically found in the human oropharynx and URT, was consistently isolated. S. hominis was the most abundant species of aerobic bacteria (22%-24%) and comprised 60%-80% of all Staphylococcus spp. The study also assessed the susceptibility of S. hominis to 222 nm-far-UVC light in laboratory experiments, which showed an exponential surface inactivation constant of k = 0.475 cm2 /mJ. This constant is a critical parameter for future on-site use of far-UVC light as a technique for reducing pathogenic bacterial load in dental clinics.

Wavelength-dependent DNA Photodamage in a 3-D human Skin Model over the Far-UVC and Germicidal UVC Wavelength Ranges from 215 to 255 nm.

The effectiveness of UVC to reduce airborne-mediated disease transmission is well established. However, conventional germicidal UVC (~254 nm) cannot be used directly in occupied spaces because of the potential for damage to the skin and eye. A recently studied alternative with the potential to be used directly in occupied spaces is far UVC (200-235 nm, typically 222 nm), as it cannot penetrate to the key living cells in the epidermis. Optimal far-UVC use is hampered by limited knowledge of the precise wavelength dependence of UVC-induced DNA damage, and thus we have used a monochromatic UVC exposure system to assess wavelength-dependent DNA damage in a realistic 3-D human skin model. We exposed a 3-D human skin model to mono-wavelength UVC exposures of 100 mJ/cm2 , at UVC wavelengths from 215 to 255 nm (5 nm steps). At each wavelength, we measured yields of DNA-damaged keratinocytes, and their distribution within the layers of the epidermis. No increase in DNA damage was observed in the epidermis at wavelengths from 215 to 235 nm, but at higher wavelengths (240-255 nm) significant levels of DNA damage was observed. These results support use of far-UVC radiation to safely reduce the risk of airborne disease transmission in occupied locations.

Molecular characterisation of Beauveria bassiana isolates obtained from overwintering sites of Sunn Pests (Eurygaster and Aelia species).

110 isolates of Beauveria (104 B. bassiana, 5 Beauveria spp., 1 B. brongniartii) were obtained from Sunn Pests (Eurygaster and Aelia species), litter, and other insect samples at overwintering sites in seven countries in the Middle East and West Asia. DNA was extracted from these isolates, and four techniques were used to characterize and to investigate genetic diversity at the molecular level: ITS-RFLP, ITS sequencing, ISSR-PCR, and AFLP. The ITS-RFLP and ITS sequences did not detect significant genetic variation among the isolates. However, both ISSR-PCR and AFLP analyses gave indications of intraspecific groupings correlated with geographical origin and relative genetic diversity among some isolates, but no obvious association with Sunn Pest hosts. There was no obvious genotypic grouping of B. bassiana isolates from E. integriceps, perhaps suggesting the overwintering populations were infected by generalist native isolates rather than by host-specific ones that might be more suitable for biocontrol purposes.

The use of amplified fragment length polymorphism for molecular analysis of Beauveria bassiana isolates from Kenya and other countries, and their correlation with host and geographical origin.

Beauveria spp. (one Beauveria sp., two B. brongniartii, and 47 B. bassiana) isolated from insects and soil from Kenya and other 16 different countries, were obtained from the CABI Bioscience Genetic Resource Collection. DNA was extracted from the 50 isolates and their genetic variability was investigated using restriction analysis of the internal-transcribed-spacer ribosomal region restriction fragment length polymorphism (ITS-RFLP), ITS sequencing, and amplified fragment length polymorphism (AFLP). The B. bassiana isolates could not be distinguished by ITS-RFLP as all of them showed the same banding pattern. However, the AFLP technique provided more information on polymorphism between the isolates, allowing them to be clustered by relative similarity using band matching and unweighted pair group method with arithmetic mean analysis. Although no significant correlation between the isolates and host and geographical origins were observed, the technique revealed clonal populations of B. bassiana within Kenya.

Evaluation of the redox dye 5-cyano-2,3-tolyl-tetrazolium chloride for activity studies by simultaneous use of microautoradiography and fluorescence in situ hybridization.

Three microscopic in situ techniques were used simultaneously to investigate viability and activity on a single-cell level in activated sludge. The redox dye 5-cyano-2,3-tolyl-tetrazolium chloride (CTC) was compared with microautoradiography (MAR) and fluorescence in situ hybridization (FISH) to indicate activity of cells in Thiothrix filaments and in single floc-forming bacteria. The signals from MAR and FISH correlated well, whereas only 65% of the active Thiothrix cells and 41% of all single cells were detectable by CTC reduction, which mainly targeted the most active cells.