Legionellapollution in cooling tower water of air-conditioning systems in Shanghai, China

Abstract

Aims: To determine Legionella pollution prevalence, describe the amount of Legionellae with respect to temperature in Shanghai cooling tower water (CTWs) in various types of public sites. Methods and Results: Six urban districts were selected as the study fields, adopting multiple‐phase sampling methods. Routine culture was used to identify Legionellae. Of the samples, 58·9% (189/321) were observed to be positive, 19·9% were isolated over 100 CFU ml−1. Legionella pneumophila serogroup 1 was the most frequently isolated species (155/189, 82·0%), followed by Leg. micdadei that was at the second place (44/189, 23·3%). The mean CFU ml−1 of Legionellae in CTWs reached its peak from July to September. Over all 15·4% of the samples exceeding 100 CFU ml−1 were observed in a hospital setting. Conclusions: The prevalence of Legionella pollution in CTWs, especially in CTWs of subway stations and hospitals, is worrying, and the positive rate and CFU ml−1 of Legionellae in CTWs have a close relationship with air temperature. Significance and Impact of the Study: The study demonstrates pollution prevalence rates in different types of sites and various seasons, and provides a proportion of different serogroups of Legionellae. It illuminates an urgent need for dealing with the potential risk of legionellosis in Shanghai, through improved control and prevention strategies.

High Prevalence, Genetic Diversity and Intracellular Growth Ability of Legionella in Hot Spring Environments

“…The Legionella pollution and concentration were also different between seasons in this study: the levels were higher in spring and winter but lower in summer and autumn. In another study that looked at cooling towers in China, the highest isolation rate and concentration was observed in autumn and showed a positive association between Legionella presence in cooling towers and increasing air temperatures [15]. However, in this study, the association between the presence of Legionella in spring water samples and increasing air temperatures was negative.…”

“…The water systems of artificial facilities, including potable water systems [8], [9], spa water [10] and cooling towers [11], [12] in large buildings, hotels, hospitals and public baths that are contaminated by Legionella are the implicated sources of outbreaks and sporadic cases of Legionnaires' disease. Thus, it is important from a public health perspective to continually survey environmental water systems for the presence of Legionella [13], [14], [15], [16]. In particular, the contamination of hot-water systems has gradually become recognized as an important risk factor all over the world [17], [18], [19], [20], [21], [22], and many cases of Legionnaires' disease have been detected in Legionella -contaminated hot-water systems.…”

Presence of Legionella and Free-Living Amoebae in Composts and Bioaerosols from Composting Facilities

“…The environmental reservoirs of Legionella are ground water, lakes and rivers [1], [2]; Legionella , however, was also isolated from potting soils and composts [3], [4], [5]. Most LD infections are linked to contaminated hot water systems, cooling towers [6], and air-conditioning systems [7], but LD cases related to potting soil use or gardening have also been described [4].…”

Distribution of Sequence-Based Types of Legionella pneumophila Serogroup 1 Strains Isolated from Cooling Towers, Hot Springs, and Potable Water Systems in China

“…In our previous study that compared the efficacy of different Legionella detection methods, we isolated Legionella at rates of 26.39%, 54.44%, and 18.94% from cooling towers, hot springs, and piped water systems, respectively, with Legionella concentrations of Ͼ1,000 CFU/liter (15). Studies have reported that L. pneumophila serogroup 1 is the most frequently isolated species in cooling towers and hot springs (9,11).…”

“…Transmission of bacteria from the environment to humans occurs via inhalation or aspiration of Legionella-containing aerosols (7,8). Cooling towers (9,10), hot springs (11,12), and potable water systems (13,14) in large facilities, hotels, hospitals, and public baths that are contaminated with Legionella are the implicated sources of outbreaks and sporadic cases of Legionnaires' disease.…”