Abstract
Cooling towers are a source of Legionnaires’ disease. It is important from a public health perspective to survey industrial cooling towers for the presence of Legionella. Prospective surveillance of the extent of Legionella pollution was conducted at factories in Shijiazhuang, China between March 2011 and September 2012. Overall, 35.7% of 255 industrial cooling tower water samples showed Legionella-positive, and their concentrations ranged from 100 Colony-Forming Units (CFU)/liter to 88,000 CFU/liter, with an average concentration of 9100 CFU/liter. A total of 121 isolates were obtained. All isolates were L. pneumophila, and the isolated serogroups included serogroups 1 (68 isolates, 56.2%), 6 (25, 20.7%), 5 (12, 9.9%), 8 (8, 6.6%), 3 (6, 5.0%) and 9 (2, 1.6%). All 121 isolates were analyzed by pulsed-field gel electrophoresis (PFGE) and 64 different patterns were obtained. All 121 isolates were analyzed sequence-based typing (SBT), a full 7-allele profile was obtained from 117 isolates. One hundred and seventeen isolates were divided into 49 sequence types. Two virulence genes, lvh and rtxA, are analyzed by polymerase chain reaction (PCR). 92.6% (112/121) and 98.3% (119/121) isolates carried lvh and rtxA respectively and 90.9% (110/121) of tested isolates carried both genes. Our results demonstrated high prevalence and genetic polymorphism of L. pneumophila in industrial cooling tower environments in Shijiazhang, China, and the SBT and virulence gene PCR results suggested that the isolates were pathogenic. Improved control and prevention strategies are urgently needed.
Highlights
Legionella, the aetiologic agents of legionellosis, are ubiquitous worldwide in rivers and lakes [1]and man-made water systems such as spas and cooling towers [2]
Most human infections are caused by Legionella pneumophila, which is responsible for approximately 90% of the identified clinical cases, and the predominant serogroup is serogroup 1 [2,4,5,6]
All 255 cooling tower water samples were collected during the study period, and the procedure for collection and pretreatments of the environmental water samples was based on the protocol according to ISO 11731 [18]
Summary
Legionella, the aetiologic agents of legionellosis, are ubiquitous worldwide in rivers and lakes [1]and man-made water systems such as spas and cooling towers [2]. Most human infections are caused by Legionella pneumophila, which is responsible for approximately 90% of the identified clinical cases, and the predominant serogroup is serogroup 1 [2,4,5,6]. Cooling towers that are contaminated by Legionella have been identified as the cause of sporadic cases and outbreaks of legionellosis among people living nearby [9,10]. It is important from a public health perspective to survey industrial cooling towers systems for the presence of Legionella [11,12]
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