Légionellose

Definition

The légionellose is a Infectious illness due to a bacterium of hydrous origin of the family of Legionellaceae (Brenner and Al 1979) of which most known is Legionella pneumophila . The bacterium develops in heated water and an organic medium favorable to their development (thermal spa etc) rich in iron, zinc, aluminum. It is known also under the name of disease of the legionaries, it is with obligatory declaration.

Causal agent

The infectious agents, are bacteria belonging to the class of the légionellas, bacillus in negative Gram; they exist at least 47 species, but the bacterium Legionella pneumophila is most frequently met in pathology at the man. Other species of legionella were isolated such: L. micdadei, L. bozemanii, L. longbeachae, etc

Mode of Contamination

The disease is acquired by the Inhalation of Gouttelette S of Eau containing bacteria, in suspension in the Air. It can be a question of a Douche with water containing of the bacteria, or, of the inhalation of aerosols coming from an installation of turns aéroréfrigérantes.

The bacterium develops mainly in tepid and hot water, i.e. precisely what one can find in the installations of warm water or circuits of turns aéroréfrigérantes. The bacillus lives ideally with 37 °C, even in a fork of Température S higher. This is why it is recommended to regulate its Chauffe-eau at a temperature of 60 °C to kill the bacillus (and not higher to avoid the Entartrement Canalisation S).

The disease owes its name with an epidemic of Pneumonie among legionaries participating in a convention of the American Legion with Philadelphia in 1976.

Forms

There exist 2 forms of the disease:

a form Benign, called fever of Pontiac , similar to a Syndrome grippal. spontaneous Cure in 2 to 5 days. It accounts for 95% of the cases.
a serious form, called légionellose, which occurs at a weakened person (elderly, Immunodéprimés, Fumeurs,…). It is characterized by a Infection Pulmonaire Aiguë which can involve the Décès in a little more than 15% of the cases. Time of Incubation from 2 to 10 days

This disease is not Contagieuse (transmissible of a sick subject on a healthy subject). It belongs to the Infectious illness to obligatory declaration.

Transmission

A recent epidemic causing 85 cases of légionelloses in a district of Lens and accusing like one of the possible sources a tower aéroréfrigérante of a company, shows us that the urbanization and the technological advancements gave the possibility to bacteria antédiluviennes of the family of Légionelles, to develop in our technical installations, to be diffused in the form of aerosols, then inhaled. The inhalation being the way of commonly allowed contamination. The many work undertaken since the first cases of légionelloses in 1976 in Philadelphia showed that the natural and artificial watery environment (lakes, rivers, ponds and even in the grounds) was the reserve of the big family of légionelles for which only some species even sérogroupes are mainly responsible for respiratory affections.

One of the characteristics of this family of bacteria is that it is detectable in water or networks water supply, at temperatures going from 5,7 to 63 °C (1) even if its thermal optimum lies between 25 and 43°C. The other great characteristic of this thermophilous bacterium is its mode of survival based on a natural parasitism of various protozaires of the watery microflora (ciliés and free amoebas of type Naegleria , Acanthamoeba ).

This double ecological property, thermophilie and parasitism, make the légionelles ones of frightening bacteria ubiquitaires of our environment explaining their presence in 30 to 60% of the taking away of medical warm water carried out in the hospitals, hotels, buildings and places of dwelling (real or houses). In addition of many water supply networks can be contaminated, beside traditional domestic medical warm water or turns aéroréfrigérantes, are also concerned the equipment of thermal spas, the decorative fountains, the baths with movement and more surprising rare machines with ice and cooling fountains.

The prevention and the monitoring of the légionelloses, in particular in the health care institutions were the object in France since 1997 of a lawful reinforcement, justified by the evolution of knowledge. The last circular of April 22nd, 2002 relating to the prevention of the risk related to légionelles specifies amongst other things, of the preventive measures to be implemented to fight against the légionelloses (2). Taking into account the weak production of aerosols during the normal use of water to a tap, the preventive provisions were carried out firstly in the places equipped with showers or scanner heads. Until 2002, the warm water delivery systems were at the origin of the greatest number of cases of légionelloses in the health care institutions but since the application of this circular, the turns air coolers seem to be the person in charge.

Symptoms

The incubation period (time passed between the contact with the microbe and the appearance of the first signs) of pneumopathy is from 2 to 12 days. The frequency of the légionelloses is higher during the summer because of the temperature of the water and the increased use of the cooling systems.

The disease of the legionaries and the fever of Pontiac involve a pneumopathy which generally starts with:

•A feeling of faintness. •Cephalgias.

•Myalgias (muscular pains).

•A deterioration of the general state.

•Shivers.

•A fever (the temperature exceeding 40°C at more half of the patients).

•A dry cough or not (i.e. producing a expectoration) rather frequently.

•A hemoptysy (spittles of blood of low abundance).

•A thoracic pain.

•A dyspnea (difficulty of breathing) being able to make accept a pulmonary embolism.

•A diarrhea.

•Nauseas.

•Vomiting.

•Abdominal pains.

•A confusion.

•A lethargy.

•Hallucinations.

•A depression.

•One is delirious.

•An obnubilation.

•A coma.

Prevention

To limit the development of légionelles, it is necessary to act on three levels:

to avoid the stagnation and to ensure a good circulation of water,

to fight against scaling and corrosion by a design and a maintenance adapted to the water quality and the characteristics of the installation,
to maintain water with an high temperature in the installations, since the production and throughout the distribution systems and to mitigate water at readiest points of use.

The implementation of these actions limits, even removes, the need for carrying out specific curative interventions on the networks such as chlorinated or thermal shocks, which do not guarantee a reduction of the contamination on the long run. Indeed of such measurements can sometimes have for consequences, an imbalance of the microbial flora, and the degradation of the installations, thus supporting the creation of new lodgings favorable to the proliferation of the légionelles ones.

It should not be forgotten that a water supply network solely does not consist of a container, the drain and of contents, transported water, but of a very complex ecosystem. The inner face of the drains is quasi systematically covered with a biofilm, i.e. a complex matrix of polymers extracellular and rock salt in which bacteria like the légionelles ones fix themselves. This biofilm plays a dominating protective part of the lodged bacteria. In a water distribution network, only the fixed bacteria proliferate, because the bacterial growth is negligible for the bacteria in suspension (case of légionelles free). Unfortunately, the bacteria of the biofilms resist of the temperatures or concentrations of disinfecting 1000 to 1500 times higher than those which kill the planktonique cells of the same species (3). The increase in this resistance is related to the consumption of disinfecting by the biofilm. Consequently, the results of the tests of disinfecting carried out in vitro are very different from those obtained in situ.

Moreover, the evolution of the content of cultivable bacteria in the biofilm during the treatments of disinfection shows that a treatment repeated in a sequential way (alternation of disinfection of a few hours and phase of recolonisation of a few days) with different disinfecting (chlorine, monochloramine, ozone, acid peracetic, quaternary ammonium or thermal shock + chlorinated shock) has as a consequence which the second disinfection is less effective than the first and the bacterial recolonisation is faster.

To avoid disinfecting, it is necessary to have a well conceived network and to carry out a rigorous and regular maintenance of this one. The control of the temperature of medical warm water of the production to the distribution is a key factor of the control of the légionelles ones. The preventive actions relate to the treatments which aim preventing a significant development of légionelles and at maintaining the concentration into légionelles, possibly present in suspension in medical warm water, on an acceptable level. These preventive actions can be discontinuous and consist, with regular interval, for example every month, in a treatment including/understanding a disinfection shock preceded at semi-annual or annual intervals, of a cleaning. This discontinuous treatment was currently validated only on small networks. The continuous preventive actions implement a process or an injection of products in a permanent way, allowing the continual control of the bacteria in suspension. The use of disinfecting uninterrupted in medical warm water is to be avoided, as much as possible (corrosion, premature ageing of certain materials, “habituations” possible of certain stocks bacterial.).

Strategies of disinfection

Dogma: the effectiveness of disinfecting is dubious even hazardous in time on the hydrous bacteria and more particularly on the légionelles ones.

The curative actions correspond to the character treatments temporary which can be necessary following the description in the water of concentrations into légionelles excessive (4, 5,6).

Medical warm water networks

When

Several conditions are obligatory:

level of action reached

is > 100 UFC Legionella pneumophila/L if water distributed to patients at the risk (defined by the circular of April 22nd, 2002)

is > 1000 UFC Legionella pneumophila/L in the other situations,

failure of the technical interventions: satisfactory temperature and flow,
species L. pneumophila causes some and not the whole of the species the légionelles ones.

UFC/L = Unit Forming Colony per Liter of water

Thermal shock

Advantages: no the special equipment (interest in the event of epidemics), acceptable cost
Disadvantages: procedure long and difficult to implement (70 °C/30 minutes in all the network), risk of burn (one second with 70 °C), inescapable bacterial recolonisation (not of remanent nature), impossible to implement with certain materials (steels galvanized, certain polymers…), increase in the phenomena of scaling and corrosion.

Ultra-violets

Disinfection into final (at the point of use)

Advantages: easy to install, not interference with water and plumbing,
Disadvantages: no the residual activity from where use only continues (cost with use), to note that UV, under certain conditions of use, can even degrade certain oxidants (hydrogen peroxide, chlorinates)

Hyperchloration

Two approaches: chlorinated shock (15 to 100 mg/l according to the procedure) and hyperchloration continuously (at least 1 free chlorine mg/l)

Advantages: disinfecting activity residual if discontinuous treatment, simple treatment has to implement.
Disadvantages: corrosion and damage on plumbing, inescapable bacterial recolonisation after chlorinated shock, formation of organochlorinated.

Dioxide of chlorine

Unstable gas produces in situ, water soluble, powerful oxidizing (1 mg/l uninterrupted)

Advantages: important remanent activity, corrosive activity less large than with hypochlorites, not of taste to water, good capacity penetrating of the biofilms, not of formation the organochlorinated ones,
Disadvantages: process difficult, expensive, chlorite generator and chlorate (potentiellemnt toxic).

Ozone

Unstable gas produces in situ. The speed of decomposition increases with heat. Acts by oxidation and ridicalizing reaction (inhibited by carbonates and phosphates and activated by UV)

Advantages: decrease by 1 to 2 decimal logarithms the number of légionelles, not of corrosion, not of tri-halation methane,
Inconvénients: no the remanent effect, formation of by-products of oxidation, expensive process, complex production.

Ionization by copper-money

Generating electrodes of Cu²⁺ ions = 0,2-0,8 mg/l and Ag⁺ = 0,02-0,08 mg/l monitoring by atomic absorption spectrometry

Advantages: acceptable cost, installation and maintenance. No the interference with water at high temperature, chlorinates and UV
Inconvénients: clogging electrodes, risk of coloring of water and especially unauthorized to date in France.

Others

hydrogen peroxide mixture - money,
acid mixture oxygenated peracetic-water: 200-1000 mg/l

In the United States, all the caused products are authorized for the practices of disinfection of the circuits of water, but in the last recommendations of the CDC published in 2003, for the control of the infections related to the environment in the hospitals, it should be noted that in the scientific absence of proof and consensus on their effectiveness, the water treatment by disinfecting is not recommended (7).

The turns aéroréfrigérantes

When

level targets < 1000 UFC Legionella species /L
level of alarm 1000-100 000 UFC Legionella species /L = cleaning and disinfection
level of action > 100.000 UFC Legionella species /L = stop then cleaning and disinfection

How to treat

The treatments indicated in the decree of December 13rd, 2004 relating to the installations of cooling by water dispersion in a flow of air are mainly preventive actions of cleaning and disinfection of the installation. These treatments are detailed and explained in guides placed at the disposal on the site of the sustainable development and Department of the Environment. http://www.ecologie.gouv.fr/spip.php?page=mot&id_mot=178

Conclusion

In conclusion, the prevention of the colonization of a water supply network by Legionella pneumophila remains the sourest approach of the prevention of the légionelloses; the procedure of disinfection of the water circuits is too much random more especially as the network old and thus is corroded and covered with a bacterial biofilm. Short-term successes of the procedures of disinfection in the form of chemical or thermal shock should not mask the inescapable recolonisation in the medium term.

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