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 due to severe pneumonia among 4,400 participants in the American Legion Congress. A total of 221 people fell ill, and the mortality rate from the disease was 15.4%. That's legionellosis. Rickettsiologists McDate and Shepard tried to find out everything about the causes, symptoms and treatment of this disease. And after 6 months from the moment of the outbreak of the disease, the pathogen was identified and found measures to combat it.
Microbiological characterization of the pathogen
As scientists later found out, 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 its metabolism makes it necessary to look for ways for survival associated withhuman life.
Firstly, legionella is an intracellular parasite, where it is well protected from the immune system. Secondly, legionella “waits” for a person in places unexpected for him, where he is comfortable - in the shower, in the pool, in rooms and cars equipped with air conditioning devices. Warm water and metal pipes allow bacteria to multiply. They also actively cohabit with cyanobacteria in warm reservoirs and pipes with warm water. For this reason, about 16% of all pneumonias involve one or more Legionella species.
In total, there are about 50 strains of bacteria of this genus, belonging to the tasonomic series of pneumotropic organisms of the genus Legionella. They also provoke legionellosis (or legionnaires' disease), the causes, symptoms and competent treatment regimens of which are already known. Now there is enough information about the spread of infection, the features of the interaction of the pathogen with the body, as well as the development of the disease. It also allows attempts to reduce mortality from legionella pneumonia and alveolitis.
Incidence and distribution 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 protection, a person, even with repeated contact, may not get sick. However, with a decrease in its functions, the likelihood of infection many timesincreases. Moreover, in patients with immunodeficiencies, including those caused by HIV infection, the symptoms of legionellosis are much more pronounced, and the period of the disease is longer.
The bacterium enters the body through the respiratory system and through wounds. The first type is respiratory drop. The possibility of spreading legionella with water droplets provides its epidemiological characteristics. Basically, all people from the team working in the same room get sick if their immunity is reduced. The contact route is more rare, although it is not excluded. In this case, the symptoms of legionellosis appear locally, that is, in the area of \u200b\u200bthe wound or skin damage, and systemically - signs of intoxication.
Patterns of morbidity are associated not only with the characteristics of immunity, but also with the age characteristics of a group of people. It has been determined that men aged 40 and over are more often and more severely ill. Women and children get sick less often. This feature allows you to distinguish legionella pneumonia from mycoplasma. Mycoplasmas are more likely to affect young people, regardless of gender.
Clinical course of Legionella infection
With a disease such as legionellosis, symptoms do not appear from the moment of initial contact, but after the incubation period. It should last about 2-10 days: over a given period of time, legionella multiplies in the body, but the activity of pathological processes is low, which causes minor (subclinical) signs. The infection proceeds either along an easy path, characterized by a flu-like syndrome, or as a type of pneumonia with severerespiratory tract lesions.
The first type of legionellosis is associated with good protective abilities of the body. As a result of contact with the infection, acute respiratory legionellosis develops according to the type of bronchitis. This type of clinical course is called Pontiac fever. The second type of the course of the disease is legionella pneumonia. It is more severe and has a high mortality rate.
It is worth noting that Pontiac fever is no less serious disease, it is only a less dangerous legionellosis. Legionnaires' disease (the symptoms of the disease are identical to those of other atypical pneumonias) is a manifestation of severe legionella pneumonia, which often leads to death for the sick person.
In the classification, it is also worth highlighting legionellosis, the symptoms of which are the most severe. This is alveolitis - a more severe form of pneumonia, which increases the intoxication of the body and reduces the likelihood of recovery. It is also worth highlighting two forms of legionellosis, depending on the place of occurrence. This is nosocomial legionellosis and sporadic, that is, out-of-hospital. The diagnosis of nosocomial legionellosis is only valid if clinical signs appear 2 or more days after admission to the inpatient department.
Characterization of symptoms of Pontiac fever
Pontiac fever is an example of a mild disease known as legionellosis. Symptoms of legionellosis of this nature resemble influenza or severe parainfluenza: the patient is worried about hightemperature (38-39 degrees), which appears approximately 36 hours after the initial contact with the infection. Intense muscle and headaches also develop, a dry cough begins. Occasionally, especially with a fever over 38 degrees, vomiting develops.
Against the background of rising temperature, accompanying symptoms are disturbing: thirst, dry mouth, decrease in the amount of urine. Chest pain also appears, although this symptom is more associated with legionella pneumonia affecting the pleura than with Pontiac fever. Occasionally, against the background of intoxication, photophobia, impaired thinking and concentration appear, although after recovery, as a rule, there are no neurological complications.
It is noteworthy how legionellosis manifests itself: the symptoms are not immediately noticeable, as well as the time of the first contact with the infection. And as soon as enough pathogens have accumulated in the body, they appear. It seems to the patient that all clinical signs appeared without predecessors, that is, against the background of complete he alth. This makes its own adjustments and may become the basis for an unjustified diagnosis of meningitis, because this disease also begins like the flu.
Symptoms of Legionella Pneumonia
Many symptoms of legionellosis, Legionnaires' disease, appear in advance, before the manifestation, because against the background of immunological disorders, the incubation period can last up to 3 weeks. This period is called the prodromal period and is manifested by common signs: the presence of a slight fever,weakness in the muscles, sweating and shortness of breath with little exertion, coughing. However, most often the incubation period is only 2-10 days. Then all the symptoms appear without a prodromal period, that is, also against the background of full he alth, as in the case of Pontiac fever.
With a disease such as legionella pneumonia (legionella), the symptoms and their characteristics no longer depend on the patient's immunological reactivity and physical endurance. The disease is severe and can lead to death. Initially, a fever appears around + 39-40 degrees, which may not be at all if the patient is ill with immunodeficiency associated with HIV or with cytostatic therapy. With fever, coughing and heaviness in the chest immediately appear. Initially, the cough is only dry, and sputum does not come out.
At the same time, chest pains begin to disturb almost immediately, because the infection (legionella) causes the appearance of fibrinous effusion in the pleural cavity and in the alveoli. This is why all legionellosis is dangerous: the symptoms, diagnosis, treatment and prognosis are also doubtful because of this. Together with these signs of the disease, the patient develops shortness of breath, infectious-toxic shock, respiratory alkalosis, which aggravate the main symptoms and reduce the body's regenerative abilities.
Common features of legionellosis diagnosis
With an infection such as legionellosis, diagnosis and treatment have their own difficulties. First, without chromatography or ELISA equipment, it is almost impossible to reliably determine the pathogen. Secondly, even with its presence, the isolation of legionella from sputum is difficult. Third, without the ability to reliably determine the bacterium that caused the disease, the doctor is forced to use beta-lactam antibiotics as an empiric antimicrobial therapy.
Legionella is resistant to most beta-lactams due to its intracellular location in the body. This also reduces the effectiveness of immunity in fighting infection and increases the amount of toxins that have a systemic detrimental effect. Therefore, the diagnosis should be as fast as possible. If there is no possibility of laboratory confirmation of the legionella pathogen, the doctor is forced to prescribe an empirical treatment regimen using macrolide or fluoroquinolone antibiotics.
Physical diagnosis of legionella pneumonia
It is practically impossible to recognize the disease immediately, due to its relatively low frequency. In addition, there are about 10 infections that resemble legionellosis in the course of the initial periods. 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. Physical diagnostics is also carried out here, based on the evaluation of data that can be obtained from a simple examination of the patient.
The first criterion for legionellosis is fever, although it is not specific. At the first contact with the patient, a rapidly progressive aggravation of well-being and an increase in shortness of breath, sometimes up to 40 breaths per minute, are striking. Immediately disturbed by coughing without sputum. The patient takes deep breaths, but later begins to spare the chest due to developing pleurisy. With legionellosis, pleurisy develops faster than with pneumococcal pneumonia.
Auscultatory characteristics of legionellosis
Also, a physical sign is the presence of auscultatory changes. Wheezing affects large areas of the lung, often the whole lobe. Moreover, if legionellosis is purely mechanically assessed, the causes, symptoms, diagnosis and treatment will be more obvious. The point is this: mainly the lower lobes are 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, extending almost straight from the main bronchus. This is where pollutants enter more frequently than the lower left lobe, although this is just a statistic and cannot be an absolute rule.
Physical examination reveals crepitus. It is more often bilateral, which happens infrequently. It should be distinguished from congestive moist small bubbling rales, which are heard in chronic heart failure with signs of fluid retention in the lungs. Nevertheless, diagnostics cannot be built on physical data alone. It needs to be supplemented with instrumental and laboratory studies.
Instrumental diagnosis of pneumonia
The two most valuable imaging modalities are bronchoscopy and radiography. The second method is more commonly available, which allows one to obtainimage of chest tissue, including inflamed areas. On the radiograph in frontal projection, a fairly large focal shadow is noticeable, which clearly does not correspond to the size of the focus expected after auscultation.
In the picture, these areas of inflammation are wider, sometimes there are several of them or they merge with each other. Less commonly, pleural fibrin overlays are seen in the area of the site of legionella inflammation. At the same time, at the stage when radiography has already confirmed that the patient has inflammation of the lung tissue, the doctor may not yet assume the presence of legionella.
Bronchoscopy is a less valuable method, although it still has some significance. It is important for differential diagnosis. With its help, it is permissible to take a bronchoalveolar lavage and be able to isolate the microbe that caused pneumonia. Of course, there are some contraindications for bronchoscopy, one of which is the severity of the patient's condition.
Laboratory diagnostic methods
The gold standard for diagnosing infectious diseases is bacterioscopy, isolation of the bacterium and its cultivation. By means of the method, it is proved that the pathogenic microbe exists in the human body and its current state is due to this. But in the case of legionellosis, bacterioscopy is practically impossible, because along with legionella, other organisms also enter the smear, which can either cause pneumonia on their own or aggravate its course. Therefore, chromatography and enzyme immunoassay are more often used.
Treatmentlegionella pneumonia and Pontiac fever
The existing protocols of the Ministry of He alth and clinical guidelines for pulmonology indicate that bronchitis and pneumonia should be treated with two types of broad-spectrum antimicrobials. One of these is either aminopenicillin or a cephalosporin. The second type of antibiotic is a macrolide. The relevance of the former is justified by the likelihood of the presence of an accompanying microflora, while macrolides are active against legionella.
It is believed that in addition to macrolides ("Midecamycin", "Azithromycin", "Erythromycin", "Clarithromycin"), fluoroquinolones with rifampicin are also active against Legionella. Among fluoroquinolones, preference is given to Ciprofloxacin, Ofloxacin, Moxifloxacin, Gatifloxacin, Levofloxacin. Occasionally, "Rifampicin" and "Doxycycline" can be used. The following combination of drugs is prescribed:
- representative of the beta-lactam group as an element of the empirical scheme - "Ceftriaxone" 1 gram intramuscularly twice a day after 12 hours;
- oral macrolide (Azithromycin 500 once a day or Erythromycin 500 6 times a day, or Clarithromycin 500 twice a day, or Midecamycin 400 3-4 times a day);
- fluoroquinolones when the two previous classes of drugs are ineffective ("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 aremacrolides. However, due to the fact that they only suppress the vital activity of the bacterium, leaving it alive (bacteriostatics), it is recommended to use fluoroquinolones if legionellosis or other atypical pneumonia is suspected. Macrolides only in high doses, and only some of them (Midecamycin and Roxithromycin) are able to have a bactericidal effect. Even when a balanced and competent antimicrobial therapy regimen is prescribed, the patient needs mechanical ventilation support, as well as infusion therapy in order to correct toxic shock.
Often, such treatment is carried out in the intensive care unit, where the patient stays for 3-5 days until the condition stabilizes. Then treatment is carried out in the infectious diseases department or in pulmonology. Moreover, recovery does not correlate with the results of radiography: infiltrative shadows remain on the pictures for about a month or more. And the entire treatment of legionella pneumonia lasts about 20 days or more. After discharge, the patient will also have to be observed at the dispensary, visiting the local therapist 4 times a year.
