Detection of culturable and nonculturableLegionellaspecies from hot water systems of public buildings in Japan

Abstract

Aims: To investigate the prevalence of culturable and nonculturable Legionella species in hot water systems of public buildings in Japan and assess the risk factors associated with Legionella contamination in hot water systems. Methods and Results: Legionella species were detected by conventional culture and molecular methods in 130 water samples collected from 40 buildings. A total of 26 (20·0%) water samples from 17 (42·5%) buildings were positive by culture, qualitative PCR or both methods: Legionella pneumophila and Leg. anisa were detected in four samples by a culture method, whereas 23 samples were positive by qualitative PCR, with the presence of various Legionella species confirmed by sequencing. Of these 23 samples, bacterial counts were quantifiable in 21 by real‐time PCR (from 1·7 × 105 to 2·6 × 1011 cells per litre). Phylogenetic analysis of amplified partial 16S rRNA gene showed close relations to various species of Legionella, including Leg. anisa and Leg. micdadei, all of which have been associated with respiratory diseases or increased antibody titres in human sera. Assessment of risk factors showed that turbidity, free chlorine concentration, iron concentration and heterotrophic plate count (HPC) were significantly associated with Legionella contamination (P < 0·05). Conclusions: Contamination of hot water systems of public buildings with culturable and nonculturable Legionella species may be a potential risk factor for Legionella infection in Japan. Adequate levels of chlorine, low levels of iron and HPC are important maintenance measures in the reduction of Legionella contamination in hot water systems. Significance and Impact of the Study: More than 40% of hot water systems in the Japanese public buildings examined were contaminated by not only culturable Leg. pneumophila and Leg. anisa but also by nonculturable pathogenic species. To our knowledge, this is the first report of both culturable and nonculturable Legionella contamination in hot water systems of public buildings in Japan.

Legionella Survey in the Plumbing System of a Sparse Academic Campus: A Case Study at the University of Perugia

“…Our data are largely in agreement with other works indicating that strains of L. pneumophila, the species mostly associated to legionellosis, are those mostly often found to contaminate taps of private apartments, hotels and hospitals in Italy [13] as well as buildings in Hungary, Germany, the USA and Japan [14][15][16]23]. Nevertheless, we also recovered several isolates of L. anisa, a species already found in building plumbing [14] and known to be associated with human infections as one of the pathogens causing Pontiac fever [1]; as well as one isolate identified as L. tauriniensis, a species recently isolated from a hospital humidifier in Turin, Italy [24] but never linked to human disease. Since several isolates were cultured from each water sample, all the sequences were aligned, and a representative one was chosen from each group of isolates obtained from the same control-point tap and identified as the same Legionella species.…”

“…Nevertheless, only a few papers have investigated the presence of Legionella in this kind of system, and none in university buildings. Our data indicated that the contamination rate recorded in the University of Perugia buildings was lower than that found in offices or schools in other countries, ranging from more than 30% in Germany [16] to 60% in Japan and Hungary [14,15], and even lower than the 30.5% rate recorded in private apartments in Italy [13]. Moreover, even if many of the buildings at the University of Perugia are very ancient (ranging in age from the 1960s back to the 13th century) and it has been previously shown that the rate of positive samples increases with the age of the building [15], we found that only 1 of the 12 contaminated buildings was older than one century, while all the others were very recent (i.e., less than 30 years-old).…”

“…This corresponded to a 22% contamination rate, with 12% and 10% of low and high levels of contamination, respectively. It is well known that Legionella is more likely to be found in hot-water mains and, furthermore, the production of hot water by centralized systems has been often associated with higher rates of contamination [13][14][15]21]. Stagnation, low circulation efficiency, and temperature drop within the hot-water network are also considered typical risk factors of large buildings with extensive plumbing systems [15].…”

Validation of a Microbead-Based Format for Spoligotyping of Legionella pneumophila

“…Several species of the Legionella genus are responsible for LD; however, L. pneumophila is responsible for the majority of cases of LD, with Ͼ90% of all identified clinical cases within serogroup 1, which accounts for ϳ85% of all cases (2,3). The organism is quite ubiquitous in aqueous environments, whether natural or artificial (4).…”

Applicability assessment of ceramic microbeads coated with hydroxyapatite-binding silver/titanium dioxide ceramic composite earthplus&trade; to the eradication of Legionella in rainwater storage tanks for household use

“…In recent years, contamination of water systems has gradually become recognized as an important risk factor all over the world, [39][40][41][42][43][44] and many cases of Legionnaires' disease have been detected in Legionella-contaminated water systems.…”