Treatment of Legionnaires' disease

Description of the bacterium

introduction

Infections by opportunistic pathogens, whose natural habitat is the environment, have gained in the last two decades a higher profile. As they have evolved the diagnostic tools and their availability is still common diagnosis of cases of Legionella spp. in hospitals and its incidence is higher than that originally assumed. However, its diagnosis is very difficult and sometimes can only be confirmed by histological findings and / or pathological. Infections caused by these types of germs are generally feature affecting mainly patients with some form of immunosuppression.
Epidemiological research can be very complex and sometimes problematic security elucidate the origin community or nosocomial infection.
Because of its ecological niche is a germ of a great ubiquity and its mechanism of transmission is closely linked to engineering systems (air conditioning with Aspergillus spp. Water supply systems, particularly hot, and cooling with Legionella spp.) This implies that preventive actions depend primarily design and maintenance of such systems.

Historical Background

Legionella pneumophila is the causative agent of acute respiratory disease was originally called "Legionnaire's Disease" when affected many attendees LVIII Annual Convention of the American Legion in Bellevue-Stratford Hotel in Philadelphia, held between 21 and 25 July 1976.
In the Department of Public Health of Pennsylvania were collected 221 cases of a strange respiratory disease contracted during the convention and which concerned only the hotel guests. Symptoms include high fever, dizziness, muscle pain, headache and development of a dry cough with difficulty in breathing. Some patients developed pulmonary lesions similar to those of pneumonia. More than a third of the patients required hospitalization and 34 of them died.
Investigations on this case by the Centers for Disease Control and Prevention in Atlanta led to the discovery of the causative agent, a bacterium, in January 1977.
This bacterium was subsequently named Legionella pneumophila with reference to the professional activities of the personnel concerned and the clinical picture produced and when analyzed tissue samples (archived) for five years before had resulted in deaths with similar symptoms without identified etiologic agent disease, we found the same bacteria. In 1947 it had grown this organism but was not given any clinical importance because it also produces a mild clinical picture which is called Pontiac Fever by where it was discovered and the nature of the clinical antipyretic.
From that date have been many sporadic cases and outbreaks described, affecting different types of establishments (hotels, hospitals, spas and even boats). One of the biggest outbreaks described took place in March 1999 in the Netherlands during a flower exhibition, of the 233 people who became ill after visiting the exhibition, the diagnosis was confirmed at 106, 48 were labeled as probable and 4 as possible.
From 1989 to 1998, 55 outbreaks reported in Spain, of which the largest was the case in 1996 in Alcala de Henares, which affected 224 people and presenting as a peculiarity which was not restricted to a single building. The species has been identified most frequently L. pneumophila serogroup 1 subtype Pontiac.
Disease is more common than previously anticipated, estimated that in the United States ¬ rren occupy about 13,000 cases per year. The incidence of nosocomial pneumonia is very variable in the different series and usually has a high mortality (up to 50%). The highest recorded incidence is associated with a greater facility for the diagnosis of disease, especially after the introduction on a routine basis for the determination of urinary antigen for L pneumophila serogroup 1. Sometimes it is very difficult to eradicate the germ of water distribution system, have been described cases of nosocomial infection in a single center over many years.

Biology

Legionella bacterium is a strictly aerobic, movable by a polar flagellum, rod-shaped (0.3 to 0.9 microns, 2-20 microns), pleomorphic, Gram negative, non-spore which has strict nutritional requirements.
Biochemically is a bacterium not fermentative, oxidase positive, catalase positive and beta-lactamase positive, preferably using amino acids as a carbon source, rather than carbohydrate.
The growth of these organisms depends on the presence of L-cysteine, iron and traces of zinc and aluminum but can survive in a wide range of physicochemical conditions, multiply between 20 ° C and 45 ° C and destroyed at 70 ° C.
Its optimum growth temperature is 35 ° -37 ° C and pH between 6.5 and 7.5.
The molecular characterization of isolates from patients in Pennsylvania led to the creation of a new family of bacteria, Legionella which consists of a single genus, Legionella which were isolated more than 40 species. Immunological diversity within species is reflected by the creation of serogroups of Legionella pneumophila which holds the record with 15 different serological types.
Important antigens include outer membrane proteins, some of which are species-specific antigens, and lipopolysaccharides which are the greater number of antigen serogroups.
Each of the strains can be divided into subtypes by antigenic analysis (L. pneumophila serogroup 1 subtype Pontiac), although these fine distinctions may be valid for epidemiological studies but do not affect clinical decisions.
ISOLATED HUMAN SPECIES
L pneumophila (15 serogroups), L. gormanii (1 serogroup), L. micdadei (1s), L. feelei (2s), L dumoffii (1 s), L. hackellae (2s), L. bozemani (1s), L. israelensis (1 s), L. Jordanis (2 s), L. saninihelensis (2 s), L. longbeachae (1s), L. maceachemili (1s), L. oackridgensis (1s), L. wadsworthii (1s), L. birminghamensis (1s), L. cincinnatiensis (1s), L anisa (1s), L. tucsoniensis (1s), L. lansingensis (1s).
SPECIES ISOLATED ENVIRONMENT

L. Cherrii, L. erythra, L. jamestowniensis, L. parisiensis, L. shakespearei,
L. santicrucis, L. steigerwalsii, L. adelaidensis, L. fairfieldensis, L. Brunensis, L. Moravica, L. quinlivianii, L. Gratiana, L. quateirensis, L. nausarum, L. worsblerisis, L. londiniensis, L. geestiana, L. rubrilucens, L. spiritensis

Ecology

Legionella is considered an environmental bacterium as their natural niche is surface water such as lakes, rivers, ponds, forming part of the bacterial flora. Since these natural reservoirs colonize the bacteria pass supply systems of cities and through the water distribution network, is incorporated into domestic water systems (hot or cold) or others who require water to function and can generate aerosols. These facilities, sometimes favoring water stagnation and accumulation of products that serve as nutrients for the bacteria, such as sludge, organic matter, material corrosion and amoebae, forming a biofilm.
The presence of the biofilm plays an important role, together with the water temperature in the multiplication of Legionella concentrations up infective to man.
From these places, significant concentrations of bacteria can reach other parts of the system where, if an aerosol-producing mechanism, the bacteria can be dispersed in aerosol form. Water droplets containing the bacteria may remain suspended in the air and penetrate into the airways into the lungs.
The facilities most often are contaminated with Legionella and have been identified as sources of infection are domestic water systems, hot and cold water, cooling towers and evaporative condensers in hospitals or in hotels or other buildings. In the scientific literature are also described in the hospital, infections related to equipment used in respiratory therapy. Other facilities related to infection such as ornamental fountains, humidifiers, rehabilitation and recreation centers, swimming pools on cruise ships, etc..
An important biological characteristic of this bacterium is its ability to grow intracellularly, both in protozoa and in human macrophages.
In natural aquatic environments and facilities and industrial buildings the presence of protozoa plays an important role supporting the multiplication of intracellular bacteria, this process serving as a mechanism for survival in unfavorable environmental conditions. Legionella cells are able to live so endosymbiotic inside amoebae like Acanthamoeba, Naegleria, Tetrahymena and Hartmanella, which protect against adverse external conditions (resistance to biocides) and are also necessary nutrients for their growth. An amoeba can contain from 1 to 1,000 cells of Legionella and when they take the form of resistance (cyst) can survive a month without nutrients and in the most adverse conditions.
This is the way they survive in the environment bacteria so delicate and so difficult to reproduce in controlled laboratory conditions.
Similarly infective get their success inside the human body, when they get airway to the alveoli, are phagocytosed by alveolar macrophages but our are not digested, as they have a mechanism to inhibit the fusion of the digestive vacuoles with phagosomes contain them and thus they remain protected from the immune system, proliferate and increase their infectivity.

Description of the disease

Introduction

Legionellosis is a bacterial disease of environmental origin which has essentially two perfectly distinct clinical forms:
pulmonary infection or "Legionnaire's Disease" (McDade et al 1977) which is characterized by pneumonia with high fever that does not subside and unproductive cough. Extrapulmonary symptoms are headache, psychic disturbances with confusion and memory loss, stiffness, and joint and muscle pain, loss of energy and general discomfort, chills and trembling, shortness of breath and chest pain, and gastrointestinal upset.
pneumonic form is not known as "Pontiac Fever" (Fraser et al 1979) which manifests as an acute self-limiting febrile syndrome that results in a spontaneous recovery of those affected in 2 to 5 days. The most prominent symptoms are fever, muscle aches and loss of energy.
Pneumonia is clinically indistinguishable from other atypical pneumonias and patients often require hospitalization. The incubation period is usually 2 to 10 days is more common in people aged between 40 and 70 years, presenting two to three times higher among men than among women, is rare in children (Memorandum from WHO 1990) .
Many patients respond immediately to a treatment suitable amtimicrobiano but convalescence is often prolonged (several weeks to few months).
The risk of contracting the disease depends on the type and intensity of exposure and health status of the subject susceptible, increasing in immunocompromised patients, diabetics, patients with chronic lung disease and in smokers or alcoholics.
The attack rate (number of patients / number of people exposed) in crops is 0.1 to 5% in the general population (Memorandum from WHO 1990), the lethality, in the community, is less than 5% but can get to be 15 or 20% without introducing appropriate antibiotic therapy.
In the nosocomial cases the frequency ranges between 0.4 and 14% and mortality can be 40% to 80% even in immunocompromised patients without adequate treatment.
Antibiotic treatment of choice is erythromycin, for although it immunocompromised patients and risk of recurrence for immunocompetent patients are advised quinolones such as levofloxacin.
The delay in the implementation of quinolones or macrolides strengthens the resistance of legionella in the patient.
In the case of Pontiac fever treatment is symptomatic (WHO Memorandum 1990).
Legionella infection can be acquired primarily in two areas, the community and the hospital. In both cases the disease may be associated with several types of facilities and buildings, and can occur in outbreaks / cases grouped related cases and cases isolated or sporadic, forms that will be defined later.

Transmission of the bacteria to man

The entry of Legionella in the human body occurs primarily by inhaling aerosols containing a sufficient number of bacteria, there being no evidence of possible transmission from person to person, or the existence of known animal reservoir.
To produce infection in man have to give a series of requirements:
That the organism has an entry to the facility. This usually occurs by natural water supply contaminated by bacteria, usually in small amounts.
To multiply in the water until a sufficient number of microorganisms to be a risk to susceptible persons. Multiplication is a function of temperature of water, stagnation and the presence of other pollutants, including dirt inside the facility.
Dispersed into the air in aerosol form from the system. The polluted water presents a risk only when dispersed in the atmosphere as an aerosol (dispersion of a liquid or a solid in air or a gas). The risk increases when reducing the droplet size in suspension, because the droplets are suspended in the air over time and only droplets of size less than 5? M penetrate into the lungs.
That is virulent for man, because not all species or serogroups are also involved in the production of disease.
Susceptible individuals are exposed to aerosols containing Legionella enough viable.
In the hospital, the risk of acquiring the disease after exposure to contaminated water depends on the type and intensity of exposure and health status of the person. An increased risk immunocompromised patients and patients with chronic diseases such as chronic renal failure and hematological malignancies. Patients with moderate risk are diabetics, patients with chronic lung disease, patients with nonmalignant blood diseases, smokers and elderly.
For the prevention and control of Legionella can affect the following aspects: preventing the entry of Legionella to the facility, preventing them from multiplying and prevent aerosolization.

Diagnosis of the disease

The diagnosis of human infections caused by Legionella may be performed by microbiological methods following:
Cultivation of bacteria from respiratory specimens (sputum samples obtained by bronchoscopy or lung tissue) using the appropriate culture media (GVPC, BCYE and BCYE-Cys).
In the case of isolation of the bacteria in environmental samples (water), use the same culture media and the procedure described in the UNE EN ISO 11731.
Serology by indirect immunofluorescence (IFA), demonstrating the presence of specific antibodies in the serum of the patient after infection with the bacteria. The criteria for interpretation of results are detailed in paragraph 2.5 of this document.
Specific antigen of L. pneumophila serogroup 1 in urine. This technique is faster than in recent years is being applied increasingly in our country.
Visualization of the organism in liquid or pathological tissues by direct immunofluorescence (Fast FISH). This technique provides a presumptive diagnosis rapidly, but has some difficulty in interpreting the results, being important to rule out false positive results due to cross reactions with other microorganisms , and consider that a negative result does not exclude the presence of disease. An advantage is that it is capable of detecting both free cells as cells endosymbionts (inside amoebae).
The use of specific DNA probes and the application of the chain reaction (PCR) are some of the developing show the highest expectations for future diagnosis.
An evaluation of these diagnostic techniques taking into account their sensitivity and specificity is as follows:

Test	Sensitivity (%)	Specificity (%)
Sputum culture	80	100
IFA esput	33-70	96-99
Urinary antigen	70	100
Serology	40-60	96-99

Epidemiological data

Notifiable diseases (EDO)

Legionellosis in 1996 was included among the notifiable diseases at the national level, after the approval of Royal Decree 2210/95 of 28 December (BOE of 24 January) by establishing the National Epidemiological Surveillance Network .
The disclosure relates to medical practitioners in both public and private, is suspected of a case. The notification is weekly and is accompanied by some data on the case (identification, epidemiological and microbiological) collected in accordance with the Protocols of Notifiable Diseases (CNE 1996). Annex 1 contains the survey epidemiological case reporting system Legionellosis Notifiable Diseases.

Incidence of legionellosis in our country

In 1997, the first year that data is available System Notifiable Diseases, declared 201 cases of Legionnaires' disease by 11 autonomous regions, representing a rate of 0.51 cases per 100,000 population. That same year, seven hospitals reported 114 cases Autonomous Communities to SIM.
Information on the study of outbreaks provides data on risk factors and transmission mechanisms. From 1989 to 1997 reported 45 outbreaks of Legionnaires' disease (679 cases in total), some of them with a high number of cases, as occurred in a hotel in Granada in 1991, which affected 91 people, or the one in Alcala de Henares, Madrid, in 1996, affecting 224 people.
According to the field where there were 37 community outbreaks occurred (82%) and 8 hospitals (18%) (CNE, unpublished data).
Of the total of 1,365 cases in travelers, reported by different countries in Europe EWGLI in the period 1987-1997, 376 (28%) are related to Spanish facilities (CNE unpublished data). In our country, this information has clear social, economic and health.
In recent years there have been major outbreaks, such as occurred in Murcia during the summer of 2001, which allegedly affected 745 patients, 310 of which were confirmed by the laboratory.
In 2002 there were cases in Mataro (over 110), L'Hospitalet de Llobregat (12 cases), Jaén (8 cases), Segovia (6 cases), Terrassa (4 cases), Castellon (4 cases), Alcoy (4 cases ), among other populations.
Finally, the Legionella Reference Laboratory has been characterized since 1980, approximately 2,000 isolates of Legionella (300 and 2,700 human-induced environmental origin) from almost all the Autonomous Communities. From his results it appears that L. pneumophila serogroup 1 is the main pathogen and the most common serogroup in the environment.

Actions before the notification of cases of legionellosis 

Considerations

To address the actions to be taken in a building / facility associated with cases of Legionnaires' disease should take into account a number of factors affecting the degree of consideration of the building / facility as a possible source of infection. These factors could outline in:

• Number and presentation of cases, as we are at an isolated case or related cases consolidated cases / outbreaks.
• Type of building / premises involved, as this factor determines the number of people likely to undergo exposure depending on whether they are private homes, public buildings, installations outside of buildings or hospitals.
• Quantity and quality of Legionella species encountered, because as has previously expressed to produce Legionella infection is necessary that significant concentrations range and also not all serogroups of Legionella species and have been implicated in infection.

It is therefore recommend a more or less intense action depending on the combination of the above factors. For example, measures to take in the presence of an isolated case will be lower in the case of its association with private homes and even public buildings, but will have greater relevance if it is the hospital setting. Therefore, before deciding on measures to be applied should be a detailed analysis that includes the combination of the scenarios described.
From an epidemiological point of view we consider:

• Clustered cases / outbreaks, two or more cases in a time interval less than 6 months in people who have attended one place in the 2 to 10 days before the date of the first symptoms.
• Related cases: two or more cases in a time interval of 6 months in people who have attended one place in the 2 to 10 days before the date of the first symptoms.
• Isolated case: if there is an event not epidemiologically linked with anyone else.

Defined confirmed nosocomial case of that which occurs in a patient who has spent the 10 days preceding the date of onset of symptoms in a hospital setting and nosocomial case ç likely when the patient has been admitted at least one day in the 10 days preceding the date of onset of symptoms.

Research an isolated case of Legionnaires' disease

After the appearance of a case of Legionnaires must conduct a study to identify where, potentially, could contract the disease, investigate the occurrence of other cases involving him in the previous six months, confirm the diagnosis and, when combined a building for public use, carry out an inspection of the facilities allegedly involved. Likewise, there must be an early warning system for early detection of new cases associated with the same facility.
After identifying the case All data concerning the same individual according to the survey conducted for the purpose and that is reflected in the protocols of the National Epidemiological Surveillance Network for service, and it also makes the weekly statement numerically.
In identifying possible sources of infection means a detailed description of the places where the patient has been in the 10 days preceding the onset of the disease, with emphasis on the survey on those establishments such as hospitals or hotels.
In the hospital at the onset of an isolated case of nosocomial legionellosis shall be a comprehensive study, as applied in the investigation of clustered cases / outbreaks, detailed in paragraph 5.3, including an epidemiological study, a more alert to the emergence new cases and sampling for detection of Legionella.

Investigation of cases of Legionnaires' disease related or grouped / outbreaks

Notification of cases of legionellosis associated with building / facility triggers a series of epidemiological, microbiological and environmental responsibility of the health authority. The purpose of these studies is to establish the possible relationship between cases and detect a common source of infection in order to take appropriate action.
The investigation will consist of the following steps:

1. Epidemiological study: There shall be an initial descriptive study according to the variables of person, place and time, and to identify and confirm cases by the laboratory. From here, will be formulated hypotheses that attempt to verify, if possible, with an analytical study of cases and controls. When an outbreak is detected proceed to urgent notification to the National Epidemiological Surveillance Network. After a period of three months after the end of the outbreak, submit a report with supporting evidence containing the information end of the research conducted.
2. Environmental study. It includes the following actions:
   • Inspection of facilities. Whenever you suspect or report related or grouped cases / outbreak associated with a particular facility / building will be an inspection of it. This will involve a thorough review of the facility trying to make an identification and assessment of critical points. We will cover at least the issues listed in paragraph 4 (Preventive action) for the detection of structural defects, malfunction or faulty maintenance of the facilities.
   • Environmental sampling. The sampling should be performed in facilities / buildings where there is evidence of association with cases of Legionnaires' disease and aims to detect the presence of Legionella, which determines the possible sources of infection. Samples of water must be designed carefully in each building or facility, based on data derived from the epidemiological survey and inspection, to leave no important point without studying or unnecessary analysis, therefore, it is important to identify previous critical points. Annex 4 of the RD 865/2003 of the Ministry of Health, which sets out the hygienic criteria for the control of legionellosis, explains the points to be taken water samples for isolation of Legionella . Samples must be collected in sterile containers and packaging with proper sealing to prevent breaking or spilling their contents in transportation. Samples of water from a facility or building will always prior to treatment. If the first sampling yields negative results for isolation of Legionella, it is recommended that further sampling. In buildings that have undergone disinfection treatment must allow at least 15 days after treatment for a sampling. In the hospital setting should be carried further the study of personal therapy equipment and humidifiers.

1. Microbiological diagnosis / the event / s. It is advisable to confirm the clinical diagnosis by laboratory tests, according to the criteria expressed in the corresponding section of this website. The diagnosis should be performed in specialized laboratories. In the search for the sources of infection is important to have strains from patients. The comparison of the environmental isolates by application of typing methods, will establish the possible identity between the two, showing the relationship to a specific facility with the appearance of cases.
2. Treatment facilities and correction of structural defects. If as a result of these studies (epidemiological, microbiological and environmental) and inspections permitted facility or building associated with the reported cases, the health authority will decide the actions to perform. The performance of such action shall be the responsibility of the person responsible for installation, and may delegate to authorized companies. These actions are of three types:
   
   • Proper treatment or disinfection. Shall aim to eliminate contamination by bacteria. Disinfection should be addressed even in the absence of microbiological results of both patients and environmental samples, since the time needed to count them is long. When you decide to carry out this treatment should be chosen a procedure that least impact the daily life of the institution. This is especially important in hotels or hospitals to continue their normal operation. This treatment facilities / buildings, consists of two phases: an initial shock treatment, followed by continued treatment and carried out in accordance with the recommendations contained in Annexes 5.3 and 6.3 for domestic water facilities and towers cooling, respectively. The treatment of respiratory therapy equipment and humidifiers used in hospitals must ensure that their total sterilization and use of sterile water in its operation (Annex 8.1).
   • Reforms in structure. The inspection may result in the need to correct defects of the installation, such as elimination of blind sections in the pipe network of both hot and cold water, suppression of additional tanks or cisterns of connections, wells, etc..; Substitution Pipe in poor condition, change of location of cooling towers to prevent the aerosol discharge into areas of movement of persons; replacement of showers, taps or other terminals on the network, etc..
   • Total or partial paralysis of the installation. In extreme cases, in the presence of a large number of cases associated with very dirty facilities, contaminated by Legionella, obsolete or faulty maintenance, may recommend closure of the facility, until the defects found are corrected.

Actions after treatment facilities

If as a result of decisions we conclude that a building or facility must be processed, the health authority shall establish a further control to verify that the installation has been disinfected and structural defects detected during the inspection are corrected in order to prevent new cases. This monitoring shall include:

• Epidemiological surveillance. It should carry out active surveillance for early detection of cases associated with the same facility.
• Inspection. In facilities or buildings where the association with known previous cases of legionnaires' inspections are mandatory and must be carried out regularly (every six months for at least two years).
• Sampling post-treatment. It will take place with the same frequency that inspections, taking water samples for microbiological Legionella positive points that were previously in order to determine the effectiveness of treatments. It should be noted that the bacteria may not be detectable in the days following the treatment, but may again reach larger amounts after some time, if conditions permit multiplication system. Therefore, no checks are necessary for an installation until at least 15 days after application of a treatment.

Some follow-up studies of Legionella-contaminated buildings show the difficulty of achieving complete elimination of the bacteria, so that after performing a disinfection treatment must take extreme measures to maintain the facility to prevent the growth of Legionella. Therefore, the buildings at some time have been associated with cases should be subjected to special surveillance and continued, in order to minimize both the risk of colonization of the facilities, such as multiplication and spread of Legionella.

Facilities at risk from legionella

The facilities most often are contaminated with Legionella and have been identified as sources of infection are distribution systems for domestic water, hot and cold teams evaporative water cooling such as cooling towers and condensers evaporative in both health centers and in hotels or other buildings.
Legionella cells reach these facilities in low numbers with the waters of contribution whether well or domestic water network and this is where you will find ideal conditions to multiply to levels infectious for humans.
Therefore, the key to reducing the risk of legionella is to keep the level of Legionella in any given system of risk below a minimum, stopping them from dividing and thus prevent transmission of Legionella to people.

Multiplication of Legionella risk facilities 

Cooling towers

Water from cooling towers is a very suitable for the multiplication of legionella. The most important conditioning factor of this multiplication is the temperature, since the primary function of these systems is to cool hot water. Water in the circuits of the cooling towers usually exceeds the 25 0C, and during the summer months easily surpasses the 35 0C, temperatures suitable for growth of Legionella.
Another factor which favors the persistence and proliferation of legionella in cooling towers is the ability to form biofilms in the high internal surface which constitutes the filling installation. When there is a shortage of nutrients, these biofilms are ecological niches that allow microorganisms to share these nutrients and protect against possible chemical attack (disinfectants).
The presence of inappropriate materials in the cooling towers, mainly based on cellulose, lead to the confinement and multiplication of microorganisms and hinder cleaning and disinfecting them.
Water cooling towers often contain organisms such as protozoa, inside which it multiplies and where legionella is also physical protection against disinfectants.
Other factors that have been associated with growth of legionella at this facility are:

1. The stagnation of the water produced in the tray of cooling towers or, if any, in the intermediate deposits.
2. The products of corrosion of materials, especially if they are not specifically resistant to it.
3. Frequent fouling circuits.

In summary, the primary factors to consider, favoring the multiplication of legionella in the water from cooling towers, are:

• HIGH TEMPERATURES, especially in the summer months.
• DIRT, which guarantees the presence of other microorganisms (bacteria and protozoa) necessary for the multiplication of Legionella and the proper nutrients.
• Inadequate materials, like wood and other cellulose-based.
• Corrosion and fouling, due to improper maintenance of the facility and contribute to the multiplication of Legionella through the provision of nutrients (iron, phosphates, etc..) And favor the confinement of the bacteria, thus reducing the effectiveness of the cleaning and disinfection.

Evaporative cooling devices

In general these devices pose less risk of growth of Legionella because they work with a lower temperature than water cooling towers. However, high temperatures are reached in our environment during the summer months, when they just operate these devices, located in the open, can heat the water enough to allow the multiplication of legionella.
As in the case of cooling towers such devices can easily become dirty with the airborne matter (dust, smoke, microorganisms, etc..), With the dirt, along with temperature, an additional risk factor to consider in this case.
Similarly, the use of cellulose based materials favors the presence of microorganisms and makes the cleaning and disinfection.

Humidifiers

As in the previous case, the temperature of water in the system, especially in the tray or shell and dirt, are the determining factors to take into account, thus being increased risk of those devices exposed to high ambient temperatures and dirt from the weather.

Accumulators

Such systems are an ideal reservoir for Legionella proliferation and maintaining the water at elevated temperatures and stored for a while. Also tend to have enough lime deposits mainly from water supply which provides enough nutrients to become a perfect reservoir for the proliferation of Legionella.
The safe temperature for the operation of these systems must be maintained at 70 ° C, at which Legionella is destroyed. Poor performance to keep the water below 60 º C which will be promoting their proliferation rather than inhibit it.

Mode of transmission of legionellosis

That being said, legionellosis is transmitted by air. It is necessary to inhale the germ that carries air into very small droplets of water. These droplets come from spray (water spray) emitted by cooling towers, humidifiers and evaporative cooling apparatus when water containing contaminated by Legionella.
In the case of cooling towers, aerosols are released to the outside with the hot air stream coming out of those, and once on the outside, when it stops the momentum with which they are made, the smaller water droplets will be carried by the wind more or less distance, depending on weather conditions existing at the time and location of the tower can easily reach several hundred meters.
Thus we understand the importance of cooling towers are located in strategic locations, ie as far as possible from places frequented by people, so that drops of water that would accommodate these bacteria are deposited in the ground or evaporate (then dying bacteria) before coming to be inhaled by people, or aerosols are dispersed by wind as much as possible, so that the amount of bacteria that may exist in the inhaled air was minimal and did not lead to health risks. Therefore, the location of facilities should be done preferably on the roof of the building, provided it is within easy reach.
In the case of humidifiers and evaporative cooling apparatus, aerosols are emitted indoors, so that potentially contaminated water droplets can easily be inhaled by people. Therefore, the proper maintenance of these devices is the most effective tool to minimize the risks.
To minimize the risk of exposure can take a series of measures to prevent the proliferation of Legionella in the system or on the ground and reduce exposure to water droplets or aerosols. These measures will always be linked to proper maintenance of these facilities.

Maintenance of facilities at risk from Legionella

Precautions to be taken into consideration are the following:

• Minimizing the release of water sprays, with drop separators high efficiency.
• The amount of entrained water will be less than 0.1% of the circulating water flow of the equipment.
• Avoid temperatures and water conditions that may support the growth of Legionella and other microorganisms.
• Avoid standing water, such as by-pass piping, equipment reserve fund blind pipes etc.
• Installing drains in low points of the facilities and proper slope for complete emptying.
• Avoid the use of materials that harbor bacteria and other microorganisms, or provide nutrients for microbial growth.
• Avoid the use of materials deteriorate with water, chlorine and other disinfectants (biocides) to avoid corrosion.
• Equipment and appliances must be easily accessible for inspection and cleaning.
• Teams will be fitted in a place accessible by at least one device for sampling water recirculation.
• Maintaining the cleanliness of the system and the water therefrom.
• Use efficient techniques of water treatment.
• Where water is used from different sources to the public, should be assured by disinfection prior monthly by independent laboratory certified and duly registered in the Public Health Laboratory of the community where the facility is located, the absence of bacteria Legionella type.

All these facilities require technical maintenance for its operations, but the fact that these devices can cause Legionnaires' disease cases requiring it, in addition to a health maintenance to minimize the risk of multiplication of legionella.
In order to maintain the facilities at risk in the best cleaning along with a comprehensive microbiological control, are implemented maintenance programs involving the combination of several types of treatments.

Antifouling and dispersing

These products prevent salt precipitation within the circuit and deposits of sludge and sludge. Some of them act to increase the solubility of mineral encrustations generating (calcium carbonate, calcium phosphate and silica).

• Phosphonates (HEDP, AMP, PBTC) exhibit a resistance to degradation compared with very different oxidants. They may act by modifying the crystal structure of the first crystal formed, preventing new ones are added later.
• Polymers such as polyacrylate (PA) and polymethacrylates (PMA). Usually water soluble, low molecular weight chains and are acting on load and prevent the binding of particles of opposite sign.

Anticorrosives

Products to prevent oxidation of the metal making up the circuit.
The use of corrosion witnesses is a useful method for determining the corrosion rate.
Since corrosion is an electrochemical process where there is an anode and a cathode, we can distinguish between corrosion inhibitors:

• anode: prevent the transport of the metal into water. (Phosphate at high concentration, molybdate)
• cathode: avoid contact of oxygen with metal (polyphosphates, zinc)

There are also corrosion inhibitors for certain metals and copper are used for the aromatic azoles. In cases where there copper components in a circuit must use these specific anticorrosive to prevent oxidation during disinfection processes in which they are using high concentrations of oxidizing agents like chlorine.

Disinfectants or biocides

The biocide programs that are designed to prevent or eliminate Legionella risk facilities may include application of a single biocide or mixtures of several of them with different frequencies and application rates.
But a prerequisite is that they all have passed the bioefficacy against Legionella according to standard prEN13626 (Chemical disinfectants and antiseptics. Bacterial activity against Legionella pneumophila products), and also duly registered in the Directorate of Biocides Surgeon General of the Ministry of Health.

Classification of the biocides as its active ingredient

Halogenated oxidants

• Chlorine gas, gas, very toxic. Available in gas, but the dangers inherent in its management which hamper its use.
• Sodium hypochlorite: sold in aqueous solutions with different contents of active chlorine.
• Calcium hypochlorite is presented in solid form. Helps increase water hardness.
• Chloroisocyanurates: organic compounds that generate hypochlorous acid and ciannúrico by hydrolysis.

The disinfectant ability of these products depends greatly on the pH. Are not effective above 8.5, as the biocidal activity resides in the hypochlorous acid, cause corrosion of metals and is easily inactivated in the presence of organic matter of significant quantities of ammonia with formation of chloramines.

• Chlorine dioxide does not react with ammonia and its action is independent of pH (between 6 and 10). Their ability algicide is higher than that of chlorine.
• Bromine and derivatives: disinfectant effectiveness is more stable against pH. Can be used either active bromines activated in situ. In the latter case the bromine salt is dosed with sodium hypochlorite which generate sodium hipodromito already active.
• Iodine and derivatives of little use.

Disinfections with halogenated compounds involve reactions with the organic matter byproducts such as halogenated organic compounds (AOX) and other volatile compounds. They are persistent in the environment, toxic and mutagenic even at low concentrations.

Oxidizing non-chlorinated

• Hydrogen peroxide (hydrogen peroxide) does not include sales to the circuit and produces no toxic byproducts. Important point and the dosage form as is readily inactivated.
• Permanganate and peracetic acid: very limited use.
• Ozone: very strong oxidant, requires large power consumption. Is more effective than chlorine in some respects.

Quaternary ammonium compounds