Legionellosis

Description:

Legionellosis ("disease of legionaries"; other names — the Pittsburgh pneumonia, pontiaksky fever, a legionella-infection, fort fever Bragg) — the sapronozny acute infectious disease caused by different types of the microorganisms relating to the sort Legionella. The disease proceeds, as a rule, with the expressed fever, the general intoxication, damage of lungs, the central nervous system, digestive organs, development of a syndrome of multiorgan insufficiency is possible.

Legionellosis symptoms:

Incubation interval.  At various clinical forms of a disease varies from 2 to 10 days, averaging 4-7 days.

Most often clinically legionellosis diagnose as heavy pneumonia (actually "a disease of legionaries"). In the first days of a disease at a part of patients it is possible to observe the prodromal phenomena in the form of a headache, weaknesses, a loss of appetite, development of diarrhea is possible. At an acute onset of the illness temperature to 39-40 °C quickly increases, symptoms of heavy intoxication accrue. Patients complain of a fever, a headache, muscle and joints pains, the expressed perspiration. The general weakness, an adynamia develop. There are signs of toxic defeat of TsNS: emotional lability, block, faints, hallucinations, loss of consciousness and nonsense. Sometimes observe an ataxy, a dysarthtia, a nystagmus, paralysis of oculomotor muscles. To the middle of week there is cough, at first dry, then with scanty mucopurulent, and at a part of patients with a bloody phlegm. Short wind, severe pains develop in breasts, especially at the accompanying plastic pleuritis. In lungs reveal a dullness, sites of the weakened breath, a large number of dry and wet small-bubbling rattles. Almost at a half of patients listen to a pleural rub. On the roentgenogram define focal infiltrates of various localization; afterwards they merge and form the extensive centers of blackout as share, and quite often unilateral subtotal and even total pneumonia.

The course of pneumonia rough, difficult giving in to therapy. Development of abscesses, exudative pleurisy, infectious and toxic shock can complicate a disease. Often despite the carried-out treatment the respiratory and cardiovascular insufficiency demanding transfer of patients into IVL progresses.

Defeats of cardiovascular system are shown by hypotonia, the relative bradycardia which is replaced by tachycardia. Quite often (about 30% of cases) there are long diarrhea with abdominal pains and rumbling of intestines, hepatitises with jaundice and changes of biochemical indicators of blood. Renal failures up to the renal failure remaining afterwards for months are possible. At recovery an asthenic syndrome (weakness, dizziness, decrease in memory, irritability), the infiltrates radiological defined in lungs and pleural changes remain within many weeks.

Acute alveolitis. Emergence from the first days of a disease of dry cough against the background of high fever and other displays of intoxication (a headache, mialgiya, etc.) is characteristic. Further cough becomes wet with an otkhozhdeniye of a mucous or mucopurulent phlegm, an asthma accrues. In lungs at auscultation on both sides listen to plentiful diffusion, it is long the remaining crepitation. Process takes place with transuding in alveoluses of erythrocytes, fibrin, hypostasis of alveolar partitions. In certain cases the disease gets the long progressing current with development of fibrosis.

Acute respiratory disease (fever Pontiac). The Legionellyozny infection proceeding without pulmonary defeats. Against the background of temperature which is quickly increasing to -40 °C the fever, a headache, diffusion mialgiya appear. The respiratory syndrome in the form of rhinitises, a tracheobronchitis and bronchitis develops; quite often it is combined with abdominal pains and vomiting. Often reveal neurologic disturbances: dizziness, sleeplessness, disorders of consciousness and coordination of various degree. Disease is favorable, duration of the main clinical manifestations averages several days; the residual astenovegetativny syndrome remains much longer.

Acute feverish disease with a dieback (Fort fever Bragg). More rare form of legionellosis. Against the background of the moderate all-toxic and respiratory phenomena (is more often in the form of bronchitis) there is a dieback of krupnopyatnisty, korepodobny, scarlatiniform or petekhialny character. Elements of rash have no certain characteristic localization, after their disappearance, as a rule, do not observe a skin peeling.

In much more exceptional cases the disease can proceed in other forms: from subclinical to severe generalized forms with multiorgan defeats and sepsis.

Complications
The most terrible complication - the infectious and toxic shock arising at legionellyozny pneumonia. According to WHO data, in these cases the frequency of lethal outcomes of a disease reaches 20%.

Legionellosis reasons:

Activators - gram-negative aerobic mobile bacteria of the family Legionella of the Legionellaceae family. Now more than 40 types легионелл are known; for the person patogenno 22 look. The most frequent activator (more than 90%) - L. pneumophila. Allocate 18 serovars of bacteria; most often diseases cause bacteria of 1 serovar. L. pneumophila is cultivated on cellular environments (chicken embryos, Guinea pigs). For growth on artificial mediums of a bacterium need cysteine and iron. Pathogenicity factors легионелл include a lipopolisakharidny complex (endotoxin) and strong exotoxin. The activator is steady in external environment: in fluid medium at a temperature of 25 °C 112 days can remain, at 4 °C - 150 days. Under the influence of 1% of solution of formalin, 70 ° alcohol, 0,002% of solution of phenol perish in 1 min., in 3% chloroamine solution - within 10 min. Colonizing connecting nodes, rubber laying of tanks for water, bacteria intensively breeds in them.

Epidemiology
Tank and sources of an infection. The place of natural dwelling легионелл are fresh-water reservoirs and the soil. Most often legionella allocate from water of standing reservoirs where they live in associations with photosynthesizing blue-green seaweed and water amoebas. The warm habitals favorable for reproduction of seaweed are an ecological niche for L. pneumophila. At 35-40 °C of a legionella intensively breed in protozoa, for example the amoebas protecting bacteria from influence of high concentration of chlorine and other disinfectants. High adaptive abilities легионелл allow them to colonize successfully cooling systems, coolers, compressor devices, shower installations, swimming pools, decorative fountains, bathrooms for balneological procedures, the equipment for respiratory therapy, etc. In artificial constructions of a condition for survival легионелл can be more favorable, than in natural. The person is not a contagium source. Even at close communication with the patient cases of infection of people around are not registered. Also allocation of the activator from any animals, birds or arthropods is not established.

The transfer mechanism - aerosol, infection occurs most often at inhalation of a water aerosol. The majority of flashes is connected with water cooling systems, production cycles when which functioning the finely divided aerosol containing bacteria is formed. Also the air and dust (soil) way of infection is possible at construction and earthwork. The activator which collected in the soil, conditioners and heads of shower installations is inhaled in the form of a water or dust aerosol. In the conditions of treatment and prevention facilities the artificial way of infection connected with medical procedures is possible: vortex bathtubs, therapy by sonifiers, intubation, etc.

Natural susceptibility high. The disease is promoted by alcohol intake, smoking, endocrine disturbances, chronic diseases of lungs, immunodeficiencies. Duration of postinfectious immunity is not known, however palindromias are not registered.

Main epidemiological signs. Legionellosis is widespread everywhere; incidence is higher in economically developed countries. Arises among the living in hotels, health workers and sick geriatric and psychiatric hospitals more often. The possibility of infection of persons from risk groups at respiratory therapy is shown or an alimentary way (through drinking water). Flashes among the population arise more often in aestivo-autumnal months.

Special significance is attached to a problem of "travel-associated" of the legionellosis arising during tourist and business trips and diagnosed, as a rule, upon return from them in recent years. More than 30% of cases of sporadic legionellosis, numerous epidemic cases in hotels, frequent lethal outcomes, formed a basis for creation of uniform international system of epidemiological control of cases of the legionellosis connected with trips.

The cases of diseases connected with nozokomialny flashes note during the whole year. Elderly people, and men by 2-3 times are ill preferential more often than women. The intrahospital outbreaks of legionellosis are known. Specific weight of the pneumonia caused by legionella makes 0,5-5% while the acute respiratory disease of the legionellyozny nature (fever Pontiac) arises at 95% of total number of the persons which underwent infection.

Treatment of Legionellosis:

Basis of causal treatment of legionellosis - use of macroleads. In particular, erythromycin is appointed inside in a dose of 2-4 g/days, in hard cases enter intravenously kapelno (erythromycin phosphate on 1 g/days, as much as possible to 2-3 g/days). At absence or small expressiveness of clinical effect an antibioticotherapia is supplemented with purpose of rifampicin in a dose of 0,6-1,2 g/days. The course of treatment makes 2-3 weeks. The good clinical effect also gives purpose of ftorkhinolon (пефлоксацин).
The pathogenetic treatment directed to fight against intoxication, bleedings, development of a respiratory and renal failure, depressed cases is carried out by the standard rules. The oxygenotherapy is necessary, quite often apply IVL.