Legionellosis: symptoms, diagnosis, treatment

Legionella is a genus of bacteria that can cause severe pneumonia and alveolitis in adults. The first recorded epidemic dates back to 1976, when 35 veterans died in Philadelphia because of severe pneumonia among 4,400 participants in the Congress of the American Legion. A total of 221 people fell ill, and the death rate from the disease was 15.4%. This is legionellosis. All about the causes, symptoms and treatment of the disease tried to find out the rickettsiologists McDead and Shepard. And 6 months after the outbreak of the disease, the pathogen was identified and found measures to combat it.

Microbiological characteristics of the pathogen

As later found out by scientists, the causative agent is the bacterium Legionella pneumophila. It belongs to the category of anaerobes that can exist in an environment without oxygen. It does not form spores and capsules, the microbe does not have a strong cell wall and belongs to Gram-negative species. At the same time, the defectiveness of his metabolism forces us to look for ways to survive, connected with the vital activity of man.

First, legionella is an intracellular parasite, where it is reliably protected from the immune system. Secondly, the "Legionella" is waiting for a person in unexpected places for him, where he is comfortable - in the shower, in the pool, in the rooms and cars equipped with air conditioning devices. Warm water and metal pipes make it possible to multiply by bacteria. Also they actively cohabitate with cyanobacteria in warm reservoirs and pipes with warm water. For this reason, about 16% of all pneumonias develop with the participation of one or more species of legionella.

In total there are about 50 strains of bacteria of this genus belonging to the taxonomic series of pneumotropic organisms of the genus Legionella. They also provoke legionellosis (or legionnaires' disease), causes, symptoms and competent treatment regimens are already known. Now there is enough information about the spread of the infection, the peculiarities of the interaction of the pathogen with the body, and also about the development of the disease. This also allows attempts to reduce mortality from legionella pneumonia and alveolitis.

Morbidity and distributional features

With a disease such as legionellosis, the symptoms and severity of the condition depend on the characteristics of the organism itself. With sufficient effectiveness of immune defense, a person can not get sick even with repeated contact. However, with a decrease in its functions, the probability of infection multiplies many times. And in patients with immunodeficiencies, including those caused by HIV infection, the symptoms of legionellosis are much more pronounced, and the period of illness is longer.

The bacterium enters the body through the respiratory system and through the wound. The first type is respiratory-drip. The possibility of spreading legionella with water drops provides its epidemiological characteristics. In general, all people from the collective who work in the same room are ill, if their immunity is reduced. The contact path is more rare, although it is not excluded. In this case, the symptoms of legionellosis are manifested locally, that is, in the area of injury or skin damage, and systemically - signs of intoxication.

The patterns of morbidity are associated not only with the characteristics of immunity, but also with the age characteristics of a group of people. It is determined that men aged 40 and over are more often and heavier. Women and children get sick less often. This feature makes it possible to distinguish legionellosis pneumonia from mycoplasmal. Mycoplasmas often affect young people regardless of sex.

Clinical course of legionella infection

With such a disease as legionellosis, the symptoms do not arise from the moment of primary contact, but after the incubation period. It should last about 2-10 days: for a given period of time in the body legionella multiplies, but the activity of pathological processes is small, which causes minor (subclinical) signs. Infection takes place either along an easy path, characterized by an influenza-like syndrome, or by the type of pneumonia with severe lesions of the respiratory tract.

The first type of flow of legionellosis is associated with good protective abilities of the body. As a result of contact with the infection, acute respiratory legionellosis develops as a type of bronchitis. This type of clinical course is called Pontiac fever. The second type of disease is legionellosis pneumonia. It is more severe and proceeds with high mortality.

It is worth noting that Pontiac fever is no less severe, it is only a less dangerous legionellosis. Legionnaires' disease (the symptoms of the disease are identical with those of other atypical pneumonia) is a manifestation of legionellosis pneumonia of severe course, which often leads to a lethal outcome for the ill.

Legionellosis, whose symptoms are most severe, is also worthy of classification. This alveolitis is a heavier form of pneumonia, which increases intoxication of the body and reduces the likelihood of recovery. In this case, it is also worth highlighting two forms of legionellosis, depending on the place of origin. This is hospital legionellosis and sporadic, that is, out-of-hospital. The diagnosis of hospital legionellosis is valid only if the clinical signs were manifested after 2 or more days from the moment of placement in the inpatient department.

Characteristics of the symptoms of Pontiac fever

Pontiac fever is an example of a mild course of a disease such as legionellosis. Symptoms of legionellosis of this nature resemble influenza or severe parainfluenza: the patient is worried by a high fever (38-39 degrees), appearing about 36 hours after the initial contact with the infection. Also, intense muscle and headaches develop, a dry cough begins. Occasionally, especially when fever is more than 38 degrees, vomiting develops.

Against the background of fever, accompanying symptoms are troubling: thirst, dry mouth, decrease in the amount of urine. There are also pains in the chest, although this symptom is more associated with legionella pneumonia affecting the pleura than with Pontiac fever. Occasionally, photophobia, disturbance of thinking and concentration of attention appear against the background of intoxication, although after recovery, as a rule, there are no complications of a neurological nature.

It is remarkable how legionellosis manifests itself: the symptoms are not immediately apparent, as is the time of first contact with the infection. And as soon as the body has accumulated enough pathogens, they appear. It seems to the patient that all clinical signs showed up without precursors, that is, against a background of complete health. It makes its own adjustments and can become the basis for an unjustified diagnosis of "meningitis", because this disease also begins as a flu.

Symptoms of Legionella Pneumonia

Many symptoms of legionellosis, legionnaires' diseases, manifest themselves in advance, before the manifestation, because against the background of immunological disorders the incubation period can last up to 3 weeks. This term is called the prodromal period and is manifested by common signs: the presence of a small fever, weakness in the muscles, sweating and shortness of breath with little exercise, coughing. However, most often the incubation period occurs only for 2-10 days. Then all the symptoms manifest themselves without a prodromal period, that is also against a background of complete health, as in the case of the Pontiac fever.

With a disease such as legionellosis pneumonia (legionella), the symptoms and their characteristics no longer depend on the patient's immunological reactivity and physical endurance. The disease is difficult to tolerate and can lead to death. Initially, a fever occurs around + 39-40 degrees, which may not be at all, if the patient is suffering from immunodeficiency, associated with HIV or with cytostatic therapy. Together with the fever, a cough and heaviness in the chest immediately appears. Initially, the cough is only dry, and sputum is not separated.

Along with this, pain in the chest almost immediately begins to worry, because the infection (legionella) causes the appearance of fibrinous effusion into the pleural cavity and into the alveoli. All legionelleses are dangerous for this: the symptoms, diagnosis, treatment and prognosis because of this are also doubtful. Together with these symptoms, the patient develops dyspnea, infectious-toxic shock, respiratory alkalosis, aggravating the main symptoms and reducing the recovery ability of the body.

General features of legionellosis diagnostics

With such an infection as legionellosis, diagnosis and treatment have their difficulties. First, without the equipment for chromatography or ELISA it is practically impossible to reliably determine the causative agent. Secondly, even with its presence, the isolation of legionella from sputum is difficult. Thirdly, without the possibility of a reliable definition of the bacterium that caused the disease, the doctor is forced to use beta-lactam antibiotics as a means of empirical antimicrobial therapy.

To the majority of beta-lactams, legionella is stable because of its intracellular location in the body. This also reduces the effectiveness of immunity in the fight against infection and increases the amount of toxins that have a systemic harmful effect. Therefore, the diagnosis should be as fast as possible. If there is no laboratory confirmation of the legionellosis pathogen, the physician must prescribe an empirical treatment regimen using macrolide or fluoroquinolone antibiotics.

Physical diagnostics of legionella pneumonia

To recognize the disease immediately, in view of its relatively small frequency, is almost impossible. In addition, there are about 10 infections, with the flow in the initial periods resembling legionellosis. Symptoms and treatment of legionellosis for this reason begin with an empirical scheme - the appointment of two or more broad-spectrum antibiotics with the maximum coverage of the genera of microorganisms. Here we also carry out physical diagnostics, based on the evaluation of data that can be obtained by simply examining the patient.

The first criterion of legionellosis is fever, although it is non-specific. At the first contact with the patient, a rapidly progressing weight gain of feeling and a build-up of dyspnea, sometimes up to 40 breaths per minute, is evident. Immediately worried about cough without phlegm. The patient makes deep breaths, but later begins to spare the chest due to developing pleurisy. When legionellosis, pleurisy develops faster than with pneumococcal pneumonia.

Auscultatory characteristic of legionellosis

Also the physical sign is the presence of auscultatory changes. Large areas of the lungs are affected by the choruses, more often a whole lot. In this case, if purely mechanical evaluation of legionellosis, the causes, symptoms, diagnosis and treatment will be more obvious. The thing is this: the lower shares are mostly affected, and more often one of them. Left - due to the fact that its lobar bronchus is narrow and branches off from the main bronchus at an angle, it suffers less often. The right lower lobe is characterized by the presence of a wide and short lobar bronchus, which extends from the main almost straight. This pollutants fall more often than the left lower share, although this is only statistics, which can not be an absolutely accurate rule.

In physical diagnosis, crepitation is detected. It is more often bilateral, which happens infrequently. It should be distinguished from stagnant, wet, small bubbling rales that are heard in chronic heart failure with signs of fluid retention in the lungs. Nevertheless, only physical data can not be diagnosed. It needs to be supplemented by instrumental and laboratory research.

Instrumental diagnosis of pneumonia

The two most valuable methods of instrumental diagnosis are the following: bronchoscopy and radiography. More often the second method is available, allowing to obtain an image of the tissues of the chest, including inflamed patches. On the roentgenogram in a direct projection a fairly large focal shadow is noticeable, which obviously does not correspond to the size of the foci presumed after auscultation.

In the picture, these areas of inflammation are wider, sometimes there are several or they merge. Less commonly observed pleural overlays of fibrin in the area of occurrence of a site of legionellosis inflammation. At the same time, at the stage when confirmations have already been received by radiography that the patient has inflammation of the lung tissue, the doctor may not even presume the presence of legionella.

Bronchoscopy is a less valuable method, although it does have some significance. It is important for differential diagnosis. With its help, it is permissible to take a bronchoalveolar rinse and to be able to isolate a microbe that caused pneumonia. Of course, for bronchoscopy there are some contraindications, one of which is the severity of the patient's condition.

Laboratory diagnostic methods

The gold standard of diagnostics in the field of infectious diseases is bacterioscopy, isolation of a bacterium and its cultivation. By means of the method it is proved that the pathogenic microbe is in the human body and its present state is due to this. But in the case of legionellosis, bacterioscopy is practically impossible, because along with legionella, other organisms that can either cause pneumonia themselves or aggravate its course also fall into the smear. Therefore, chromatography and enzyme immunoassay are often used .

Treatment of legionella pneumonia and fever Pontiac

The existing protocols of the Ministry of Health and clinical recommendations on pulmonology contain indications that bronchitis and pneumonia should be treated with the use of two types of broad-spectrum antimicrobial agents. One of them is either aminopenicillin or cephalosporin. The second type of antibiotic is macrolide. The appropriateness of the former is justified by the probability of having an accompanying microflora, whereas macrolides are active against Legionella.

It is believed that in addition to macrolides ("Midekamycin", "Azithromycin", "Erythromycin", "Clarithromycin"), and fluoroquinolones with rifampicin are active against legionella. Among fluoroquinolones, preference is given to "Ciprofloxacin", "Ofloxacin", "Moxifloxacin", "Gatifloxacin", "Levofloxacin". Rifampicin and Doxycycline may be used occasionally. The following combination of drugs is prescribed:

• A representative of the group of beta-lactams as an element of the empirical scheme - "Ceftriaxone" 1 gram intramuscularly twice a day after 12 hours;
• Macrolide inside ("Azithromycin 500" once a day or "Erythromycin 500" 6 p / day, or "Clarithromycin 500" twice a day, or "Midekamycin 400" 3-4 times a day);
• Fluoroquinolones with ineffectiveness of the two previous classes of drugs ("Ciprofloxacin 400" intravenously 2-3 times a day, "Levofloxacin 500" orally once a day, "Moxifloxacin 400" once a day).

As you can see, first-line drugs are macrolides. However, in view of the fact that they only suppress the vital activity of the bacterium, leaving it alive (bacteriostats), it is recommended to use fluoroquinolones in case of suspected legionellosis or other atypical pneumonia. Macrolides only in a high dose and only some of them ("Midekamycin" and "Roxithromycin") are able to have a bactericidal effect. Even when a weighted and competent scheme of antimicrobial therapy is prescribed, the patient needs support for IVL, as well as in infusion therapy to correct infectious-toxic shock.

Often, such treatment is carried out in the intensive care unit, where the patient is 3-5 days before the stabilization of the condition. Then treatment is carried out in the infectious department or in pulmonology. And the recovery does not correlate with the results of radiography: infiltrative shadows remain on the pictures for about a month or more. And all the treatment of legionellosis pneumonia lasts about 20 days or more. After discharge, the patient will also need to be observed dispensary, visiting the local therapist 4 times a year.