The ability of face masks to reduce transmission of microbes

Optometrists have been advised to wear face masks during the COVID-19 pandemic. This study examined whether face masks were equally protective against transmission of microbes. The aim of the current study was to examine the ability of face masks to reduce transmission of microbes in aerosols and during speech. Different face masks, surgical, medical 3-ply and cloth masks with different layers were used. The masks were tested under the ASTM standard F2101–1 to measure their ability to reduce the transmission of aerosolised <i>Staphylococcus aureus</i>. Bacterial cells in different sized aerosols were captured on agar plates. The ability of masks to reduce the transmission of bacteria during speech over 30 cm was measured. Bacteria were captured in masks or on agar plates at a distance of 30 cm during the speech. All masks reduced the transmission of aerosolised <i>S. aureus</i> (p ≤ 0.007). The medical 3-ply and cloth masks with three layers reduced the transmission of <i>S. aureus</i> aerosols (3.3 μm) by 98% and surgical and seven-layer masks reduced this by 100%. An antibacterial silver mask showed significantly greater transmission of <i>S. aureus</i> in aerosols of 4.7 μm (16 ± 6 cells) and 3.3 μm (122 ± 66 cells) compared to all other masks (0–3 cells and 0–15 cells, respectively; p ≤ 0.016). Surgical and three-layer masks had significantly worse filtration of 1.1 μm aerosols than for other aerosol sizes. Wearing a mask reduced the transmission of bacteria during speech, but the inner surface of these masks became contaminated with 528–3060 bacterial cells. Face masks effectively reduce the transmission of microbes in laboratory tests. Face masks made with seven layers were very effective at stopping transmission of <i>S. aureus</i> in all aerosol particle sizes. However, face masks become rapidly contaminated during wear. If masks are to be re-used, they should be regularly replaced or appropriately washed.在新冠疫情期间，验光师被建议佩戴口罩。本研究旨在探究口罩对微生物传播是否均具备防护效果。本研究的核心目标为评估口罩减少气溶胶及说话过程中微生物传播的能力。本次实验选用了不同类型的口罩，包括外科口罩、医用三层口罩以及不同层数的布制口罩。研究依据美国材料与试验协会（ASTM）标准F2101–1开展测试，以评估口罩减少气溶胶化金黄色葡萄球菌（Staphylococcus aureus）传播的能力。不同粒径气溶胶中的细菌细胞会被收集于琼脂平板上。研究同时测定了口罩在30厘米距离内，减少说话过程中细菌传播的能力。说话过程中，30厘米距离处的细菌会被口罩或琼脂平板捕获。所有口罩均能减少气溶胶化S. aureus的传播（p ≤ 0.007）。医用三层口罩与三层布制口罩可使3.3μm粒径的S. aureus气溶胶传播量降低98%，外科口罩与七层布制口罩的降低幅度则达100%。与其余所有口罩（对应粒径下细菌量分别为0~3个和0~15个，p ≤ 0.016）相比，抗菌银口罩在4.7μm和3.3μm粒径的气溶胶中，S. aureus的传播量显著更高，分别为(16±6)个和(122±66)个。外科口罩与三层口罩对1.1μm粒径气溶胶的过滤效果，显著差于其对其他粒径气溶胶的过滤效果。佩戴口罩可减少说话过程中的细菌传播，但口罩内侧表面会被528~3060个细菌细胞污染。实验室测试结果表明，口罩可有效减少微生物的传播。七层结构的布制口罩可在所有粒径的气溶胶中，高效阻断S. aureus的传播。但口罩在佩戴过程中会快速被污染。若需重复使用口罩，应定期更换或进行恰当的清洗消毒。