Two years ago I wrote a blog post on whether Legionella bacteria can survive in sea water with the answer being a hypothetical yes. Unfortunately a case of Legionnaires’ disease has now been reported from a sea water whirlpool.
In the paper entitled “Sea water whirlpool spa as a source of Legionella infection” by D.T.Linsak et al is a description of a case of pneumonia caused by Legionella pneumophila sg.1 in a 58-year-old man who visited a sea water-ﬁlled whirlpool within a hotel and spa complex. The patient’s Legionella urine antigen test was positive for L. pneumophila sg.1. Typing results indicated the sea water isolate belonged to Sequence type ST82 and Allentown/France MAb subgroup. The possible source of infection was thought to be the addition of potable water for ﬁlling up the whirlpool.
Another factor that could facilitate the survival of Legionella in sea water are amoebae (Gast et al.). Zbikowska et al. showed coexistence and interactions between free-living amoebae (Naegleria and Hartmannella) and L. pneumophila in thermal saline baths used in balneotherapy.
Gast’s team found that amoebae capable of growing in saline environments may harbour not only a diverse collection of Legionella species, but also species potentially pathogenic to humans.
Zbikowska et al further found despite relatively high salinity level, ranging from 1.5 to 5.0 %, L. pneumophila were found in all investigated baths, although their number never exceeded 106 cells.dm−3
Findings from this investigation indicated that on the whole spa pool facilities should be expected to have pure sea water with the usual conductivity of over 45,000 μS/cm. Conductivity parameter from whirlpool sea water contaminated with Legionella is rather low and amounts to 10,780 μS/cm which indicates that fresh-water has been added to this particular sea water bathtub.
L. pneumophila proved to be more resistant to survival in sea water than other tested species (L. bozemanni, L. anisa and L. longbeachae).
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Gast, R. J., Moran, D. M., Dennett, M. R., Wurtsbaugh, W. A. & Amaral- Zettler, L. A. Amoebae and Legionella pneumophila in saline environments. Journal of Water and Health 9 (1), 37–52. doi:10.2166/wh.2010.103.
Zbikowska, E., Walczak, M. & Krawiec, A. Distribution of Legionella pneumophila bacteria and Naegleria and Hartmannella amoebae in thermal saline baths used in balneotherapy. Parasitology Research 112 (1), 77–83. doi:10.1007/s00436-012-3106-4.