218
they do not survive at temperatures higher than 60 °C, which gives us
the ideal range for its multiplication between 25 and 45 °C. Therefore,
as we shall see, the control of the temperature of the water can be used
to avoid the colonization in distribution systems by
Legionella
.
• It is believed that high concentrations of calcium and magnesium, i.e.,
in water with high temporary hardness, are associated to the presence
of
Legionella pneumophila
in reservoirs of warmwater (Lin
et al
., 1998).
• This microorganism has the ability to multiply at the interior of
protozoa (Rowbotham, 1980). Subsequently, several authors show that
the main amoebic hosts belong to the Acanthamoeba, Naegleria and
Hartmannella genera. The
Legionella
-protozoan association hinders
the disinfection process, making the control more difficult, and this
is possibly the main factor responsible for the continuous presence of
Legionella
in the environment (Barker
et al
., 1993; Lin
et al
., 1998; Burak
andZeybek, 2011;Kim
et al
., 2002;Kwaik
et al
., 1998; Lasheras
et al
.,2006).
According to several studies, the cells of
Legionella
that multiply within
the protozoan present greater resistance to the environmental variations
of temperature, osmolarity, pH and exposure to oxidizing agents, as for
example chlorine, as compared to the cells cultured in vitro (Dupuy
et
al
.,2011; Kwaik
et al
., 1998; Marchesi
et al
.,2011).
• Another important aspect to be observed with relation to the process
of disinfection of water distribution systems is the condition in which
the microorganisms, including
Legionella
, have developed. Kim
et al
.
(2002) citing several studies state that the cells associated to biofilms
show a greater resistance to the disinfectant than those in suspension,
for in the first condition the disinfectant must first penetrate the biofilm
to then cause the destruction of the microorganism.
