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

Abstract

bLegionella pneumophila serogroup 1 causes Legionnaires' disease. Water systems contaminated with Legionella are the implicated sources of Legionnaires' disease. This study analyzed L. pneumophila serogroup 1 strains in China using sequence-based typing. Strains were isolated from cooling towers (n ‫؍‬ 96), hot springs (n ‫؍‬ 42), and potable water systems (n ‫؍‬ 26). Isolates from cooling towers, hot springs, and potable water systems were divided into 25 sequence types (STs; index of discrimination [IOD], 0.711), 19 STs (IOD, 0.934), and 3 STs (IOD, 0.151), respectively. The genetic variation among the potable water isolates was lower than that among cooling tower and hot spring isolates. ST1 was the predominant type, accounting for 49.4% of analyzed strains (n ‫؍‬ 81), followed by ST154. With the exception of two strains, all potable water isolates (92.3%) belonged to ST1. In contrast, 53.1% (51/96) and only 14.3% (6/42) of cooling tower and hot spring, respectively, isolates belonged to ST1. There were differences in the distributions of clone groups among the water sources. The comparisons among L. pneumophila strains isolated in China, Japan, and South Korea revealed that similar clones (ST1 complex and ST154 complex) exist in these countries. In conclusion, in China, STs had several unique allelic profiles, and ST1 was the most prevalent sequence type of environmental L. pneumophila serogroup 1 isolates, similar to its prevalence in Japan and South Korea. Bacteria of the genus Legionella, widely present in water, contribute to human diseases. To date, more than 50 Legionella species have been characterized, and 25 species are known to cause human disease (1, 2). Legionella was first reported as a pathogen following a pneumonia outbreak in 1976 (3). Since then, several community-, hospital-, and travel-associated Legionella outbreaks have been reported. The most severe form of pneumonia caused by Legionella is known as Legionnaires' disease; however, there is also a milder, flu-like form known as Pontiac fever (4). Legionella pneumophila is responsible for approximately 90% of human infections (5). L. pneumophila is divided into 15 serogroups, of which serogroup 1 is the most prevalent disease-causing variant. Few outbreaks by other Legionella species have been reported (5, 6). 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.The water systems of several countries are highly contaminated with Legionella. 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 C...

Sequence types diversity of Legionella pneumophila isolates from environmental water sources in Guangzhou and Jiangmen, China

“…The IOD of environmental isolates in our investigation (0.950) is higher than that previously reported in China (0.749) (Qin et al, 2014), Japan (0.886) (Amemura-Maekawa et al, 2012), Canada (0.888) (Reimer et al, 2010) and United States (0.822) (Kozak et al, 2009), and slightly lower than United Kingdom (0.954) (Harrison et al, 2009) and Singapore (0.970) (Lim et al, 2011). Taking the small sampling area of this study (two cities) into account, we speculated a higher genetic diversity of L. pneumophila isolates in our study.…”

Multiplication of Legionella pneumophila Sequence Types 1, 47, and 62 in Buffered Yeast Extract Broth and Biofilms Exposed to Flowing Tap Water at Temperatures of 38°C to 42°C

“…This species includes 15 polyclonal serogroups (SGs). Most of the clinical isolates represent SG1, which is present worldwide and is also the most commonly cultured SG from environmental samples (6,7,8,9,10,11). The use of monoclonal antibodies (MAbs) revealed more heterogeneity in L. pneumophila, and nine phenons reacting with different MAbs have been defined within SG1 (12).…”

Prevalence of 7 virulence genes of <i>Legionella</i> strains isolated from environmental water sources of public facilities and sequence types diversity of <i>L. pneumopila</i> strains in Macau

“…Similarly, another study conducted in Canada obtained the same result that locus mompS provided the most alleles (22). However, one study on SBT of L. pneumophila strains in mainland China indicated that mip and flaA individually provided the most alleles in the isolates from cooling water and hot spring water (19). This might be attributed to the geographical correlation which could lead to the emergence of these results.…”

“…In one study conducted in England and Wales, ST1 was the most frequent STs, accounting for 35% of the number of L. pneumophila environmental isolates (18). From the L. pneumophila serogroup 1 isolates from potable systems, cooling towers, and hot springs in China, ST1 were reported to be about 14.3%, to 53.1% and 92.3%, respectively (19). For L. pneumophila strains, ST1 (1, 4, 3, 1, 1, 1) is predominant in environmental samples, widely distributed around world (18,20,21).…”