ABSTRACT
Featured Application: A potential application of the methodologies employed within the present work may be related to an easier and cheaper characterization of new materials developed for filtering purposes (specifically concerning the development of face masks for health issues). The possibility to employ a fast characterization technique as an official process to determine the filtering efficiency would both improve the solidity of the characterization method as well as lighten the bureaucratic burden which likely restricts the materials’ supply in shortage periods due to the long validation tests required for their trade. During the pandemic, the provision of Personal Protective Equipment (PPE) (e.g., face masks) to specialized personnel and general population represented a critical point to prevent virus spread;in addition, a huge variety of new manufacturers and products entered the market, widening the time required to test and validate the equipment’s performances according to the current regulations. In this study, we employ a simple method recently developed in our laboratory, to discriminate the filtering capability of a set of KN95-certified face masks from different producers. The method is based on a methylene blue (MB) solution which is sprayed towards a pneumatic lung simulator, connected to a dummy head dressed in different types of masks. The amounts of MB droplets passing through the tested devices are collected by a cotton pad and analyzed through UV-Vis Diffuse Reflectance. In the framework of interdisciplinary collaborations between the University and the Hospital, additional characterization techniques were performed including light optical and scanning electron microscopy morphological characterization, pressure decay, and bacterial filtration efficiency (BFE). All masks were compared to a reference one, considered the gold standard for filtering performances. © 2022 by the authors.
ABSTRACT
SCIENTIFIC BACKGROUND: Environmental sampling of SARS-CoV-2 is a fundamental tool for evaluating the effectiveness of non-specific prophylaxis measures in counteracting virus spread. The purpose of our work was to evaluate the effectiveness of the different sampling methods in the hospital setting to assess their correlation with the structural, functional, and operational situation of the monitored departments and to define the dynamics of the spread of the virus in indoor environments. METHODS: The monitoring (air bubbling sampling, surface wipe test) was carried out at the San Martino Polyclinic Hospital (Genoa, Italy) in the period since April 2020 to June 2021. The presence of viral RNA in the collected samples was evaluated by qPCR. The infection capacity of the samples collected was also evaluated by an in vitro challenge test on cells sensitive to SARS-CoV-2 infection. RESULTS: The percentage of positivity with respect to the number of tests performed (sensitivity) were air bubbler 50%, wipe test 17%, and challenge test 11%. Only 20% of the samples tested positive in the wipe test and 43% of the samples tested positive in the bubbler sampling were also positive in the challenge test. All the positivity obtained was detected at a distance of less than 2 m and height of less than 1.5 from COVID-19 patients. CONCLUSIONS: Environmental contamination from SARS-CoV-2 detected at the San Martino Polyclinic Hospital is found lower than similar assessments performed in other hospitals both in Italy and abroad. Our study predicted that environmental monitoring of SARS-CoV-2 must be carried out in an integrated way by not using a single sampling method, as each individual test has a different biological significance and performance. However, the virus detected by wipe test only is often a degraded viral fragment and not an intact infecting virion.