Legionellosis is caused by the inhalation of aerosolized water contaminated with Legionella bacteria. In this study, we investigated the prevalence of Legionella species in aerosols collected from outdoor sites near asphalt roads, bathrooms in public bath facilities, and other indoor sites, such as buildings and private homes, using amoebic co-culture, quantitative PCR, and 16S rRNA gene amplicon sequencing. Legionella species were not detected by amoebic co-culture. However, Legionella DNA was detected in 114/151 (75.5%) air samples collected near roads (geometric mean ± standard deviation: 1.80 ± 0.52 log10 copies/m3), which was comparable to the numbers collected from bathrooms [15/21 (71.4%), 1.82 ± 0.50] but higher than those collected from other indoor sites [11/30 (36.7%), 0.88 ± 0.56] (P < 0.05). The amount of Legionella DNA was correlated with the monthly total precipitation (r = 0.56, P < 0.01). It was also directly and inversely correlated with the daily total precipitation for seven days (r = 0.21, P = 0.01) and one day (r = − 0.29, P < 0.01) before the sampling day, respectively. 16S rRNA gene amplicon sequencing revealed that Legionella species were detected in 9/30 samples collected near roads (mean proportion of reads, 0.11%). At the species level, L. pneumophila was detected in 2/30 samples collected near roads (the proportion of reads, 0.09 and 0.11% of the total reads number in each positive sample). The three most abundant bacterial genera in the samples collected near roads were Sphingomonas, Streptococcus, and Methylobacterium (mean proportion of reads; 21.1%, 14.6%, and 1.6%, respectively). In addition, the bacterial diversity in outdoor environment was comparable to that in indoor environment which contains aerosol-generating features and higher than that in indoor environment without the features. DNA from Legionella species was widely present in aerosols collected from outdoor sites near asphalt roads, especially during the rainy season. Our findings suggest that there may be a risk of exposure to Legionella species not only in bathrooms but also in the areas surrounding asphalt roads. Therefore, the possibility of contracting legionellosis in daily life should be considered.

中文翻译：

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日本富山县柏油马路附近室外场地气溶胶中军团菌种类的检测、降水对军团菌 DNA 量的影响和细菌微生物组

军团菌病是由吸入被军团菌污染的雾化水引起的。在这项研究中，我们使用阿米巴共培养、定量 PCR 和 16S 方法调查了从沥青路面附近的室外场所、公共浴室设施的浴室以及其他室内场所（例如建筑物和私人住宅）收集的气溶胶中军团菌的流行情况。 rRNA 基因扩增子测序。阿米巴共培养未检测到军团菌。然而，在道路附近收集的 114/151 (75.5%) 个空气样本中检测到军团菌 DNA（几何平均值 ± 标准偏差：1.80 ± 0.52 log10 拷贝/m3），这与从浴室收集的数字相当 [15/21 (71.4 %), 1.82 ± 0.50] 但高于从其他室内站点收集的 [11/30 (36.7%), 0.88 ± 0.56] (P < 0.05)。军团菌 DNA 的数量与每月的总降水量相关（r = 0.56，P < 0.01）。它也分别与采样日前 7 天（r = 0.21，P = 0.01）和 1 天（r = - 0.29，P < 0.01）的每日总降水量呈正相关和负相关。16S rRNA 基因扩增子测序显示，在道路附近收集的 9/30 样本中检测到军团菌（平均读数比例，0.11%）。在物种水平上，在道路附近收集的 2/30 样本中检测到嗜肺军团菌（读取的比例，每个阳性样本中读取总数的 0.09% 和 0.11%）。在道路附近收集的样本中，三个最丰富的细菌属是鞘氨醇单胞菌、链球菌和甲基杆菌（读数的平均比例；分别为 21.1%、14.6% 和 1.6%）。此外，室外环境的细菌多样性与含有气溶胶产生特征的室内环境相当，高于没有产生气溶胶特征的室内环境。军团菌的 DNA 广泛存在于从沥青路面附近的室外地点收集的气溶胶中，尤其是在雨季。我们的研究结果表明，不仅在浴室中，而且在柏油路周围的区域，都可能存在接触军团菌的风险。因此，应考虑在日常生活中感染军团菌病的可能性。军团菌的 DNA 广泛存在于从沥青路面附近的室外地点收集的气溶胶中，尤其是在雨季。我们的研究结果表明，不仅在浴室中，而且在柏油路周围的区域，都可能存在接触军团菌的风险。因此，应考虑在日常生活中感染军团菌病的可能性。军团菌的 DNA 广泛存在于从沥青路面附近的室外地点收集的气溶胶中，尤其是在雨季。我们的研究结果表明，不仅在浴室中，而且在柏油路周围的区域，都可能存在接触军团菌的风险。因此，应考虑在日常生活中感染军团菌病的可能性。