Legionellae are homogeneously distributed in the
private health facilities under study and concentrations
of L. pneumophila in the water serving
the wards can easily exceed the threshold level of
104±105 cfu/L considered to be at high risk for an
outbreak of Legionnaires'disease.2 The high percentages
of positive samples also confirm this risk.3
On the basis of these findings, we advised the
management of the healthcare facilities to take the
following measures for decontaminating the water
plants which exceeded a concentration of 104 cfu/L:
thermal shock (flushing each distal outlet of the
hot water system for at least 15 minutes with water
60
C) or hyperchlorination (flushing all outlets
with water containing 20 mg/L of free residual
chlorine for at least 2 h); maintenance of heated water
at 55
C; periodic bacteriological controls. These
measures correspond to those suggested by the
Health Authority guidelines. In order to prevent
the nosocomial legionellosis, we believe it necessary
to carry out systematic bacteriological monitoring of
the hot water distribution network. In Italy there are
no requirements or standards for the control of
legionellae in domestic water system; monitoring is
recommended only for the water supplies of wards at
high risk and, for the other wards, only if cases of
legionellosis are reported.6
Despite the high levels of contamination from
L. pneumophila, no cases of nosocomial legionellosis
were reported during the period of the study. It is
probable that, given the epidemiological situation
in our country where the cases pneumonia caused by
L. pneumophila are considerably underestimated,
there are also cases of nosocomial legionellosis in
Bologna that escape notice. In fact, with the current
system of surveillance of the nosocomial pneumonia,
an aetiological diagnosis is made in less than 20% of
the cases. In the environmental conditions highlighted
by our study it is therefore necessary to set up
a system of active surveillance of cases of Legionnaires'
disease so that a real picture of the situation
can be obtained. It is our intention to continue work
with this purpose in mind.