Legionella pneumophila can be transmitted to people, especially immunocompromised patients, via hospital water pipe systems and cause severe pneumonia. The aim of our study was to investigate the presence of major virulence factor genes, ability of biofilms formation, and correlation between presence of Legionella isolates and temperature, pH, and residual chlorine of water. Hundred water samples were collected from nine hospitals in Tehran, Iran. Temperature, pH, and residual chlorine were determined during sampling. Different virulence genes and the ability to form biofilms were subsequently analyzed among the L. pneumophila isolates. Results showed that 12 (12%) samples were positive in culture method and all of the isolates were positive as L. pneumophila species (mip). A correlation was found between Legionella culture positivity and temperature and pH of water, but there was no significant correlation between residual chlorine of water samples and the presence of Legionella. The isolation of Legionella rate in summer and spring was higher than winter and autumn. Twelve (100%) isolates were positive for mip genes, 9 (75%) for dot genes, 8 (66.66%) for hsp, 6 (50%) for lvh, and 4 (33.33%) for rtx. All of the isolates displayed strong ability for biofilm production every three days. Two of these isolates (16.6%) displayed weak ability to form biofilm on the first day of incubation. This study revealed that water sources in hospitals were colonized by virulent Legionella and should be continuously monitored to avoid elevated concentrations of Legionella with visible biofilm formation.

嗜肺军团菌可通过医院水管系统传播给人类，尤其是免疫功能低下的患者，并导致严重肺炎。我们研究的目的是调查主要毒力因子基因的存在、生物膜形成的能力，以及军团菌分离株的存在与温度、pH 值和水中余氯之间的相关性。从伊朗德黑兰的九家医院采集了数百个水样。取样期间测定温度、pH 值和余氯。随后分析了嗜肺军团菌分离株的不同毒力基因和形成生物膜的能力。结果显示，12份（12%）样品培养法呈阳性，全部分离株均为嗜肺军团菌（mip）。军团菌培养阳性率与水的温度和 pH 值之间存在相关性，但水样中的余氯与军团菌的存在之间没有显着相关性。夏、春季军团菌分离率高于冬、秋季。 12 株 (100%) 分离株mip基因阳性，9 株 (75%)点基因阳性，8 株 (66.66%) hsp阳性，6 株 (50%) lvh阳性，4 株 (33.33%) rtx 阳性。所有分离株均表现出很强的每三天产生生物膜的能力。其中两个分离株 (16.6%) 在孵化的第一天表现出较弱的形成生物膜的能力。这项研究表明，医院的水源被有毒的军团菌定殖，应持续监测，以避免军团菌浓度升高并形成可见的生物膜。