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The high incidence of this microorganism in extensive distribution systems
and in large reservoirs of water is due to the ideal conditions of growth:
temperature, presence of nutrients in the sediments and in biofilms, and
the possible existence of commensalism between
Legionella
and other
microorganisms or protozoa (Lin
et al
., 1998, Leoni
et al
., 2005).
Considering that the outbreaks of Legionellosis cause high levels of
morbidity andmortality to the exposed individuals, and that the fatality rate
of the legionnaire disease can vary from 40 to 80% in hospitalized persons
(WHO, 2007), several works, from the second half of the 20th century, have
tried to establish measures to eliminate or control the presence of
Legionella
spp. in the storage and distribution systems of water, either potable or
non-potable water.
With the purpose of trying to eliminate the presence of
Legionella
spp.,
we have to know the main characteristics of the species (WHO, 2002):
• Legionellae does not multiply in sterile water fromwhich the cells were
previously isolated. This characteristic indicates that this microorganism
is part of a microbial ecosystem in which it is protected from the physical
removal caused by the water flow and the agents with antimicrobial
properties. Significant numbers of these microorganisms are detected
only when the existing sediments in the water are already colonized by
other microorganisms or when in the presence of biofilms;
•
Legionella
is not able to reproduce at high speed in water with
temperatures below 25 °C; According to Hosein
et al
. (2005) viable cells
of
Legionella
can be isolated from water that is between 6 to 60 °C, but
apparently they do not multiply at temperatures lower than 20 °C, and
