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 among 4400 participants in the American Legion congress in Philadelphia due to severe pneumonia. A total of 221 people fell ill, and the mortality rate from the disease was 15.4%. Such is he - legionellosis. Rickettsiologists McDate and Shepard tried to find out all about the causes, symptoms and treatment of this disease. And 6 months after the outbreak of the disease, the pathogen was identified and measures were taken to combat it.
Microbiological characteristics of the pathogen
As it was later discovered 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 refers to gram-negative species. At the same time, the defectiveness of its metabolism forces us to look for ways to survive associated with human life.
Firstly, Legionella is an intracellular parasite, where it is reliably protected from the immune system. Secondly, the 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 make it possible for bacteria to multiply. They also cohabit with cyanobacteria in warm bodies of water and pipes with warm water. For this reason, about 16% of all pneumonias develop with the participation of one or more types of legionella.
In total, there are about 50 strains of bacteria of this genus belonging to the tasonomic series of pneumotropic organisms of the Legionella genus. They also provoke legionellosis (or the disease of legionnaires), the causes, symptoms and competent treatment regimens of which are already known. Now there is enough information about the spread of infection, the characteristics of the interaction of the pathogen with the body, as well as the development of the disease. This also makes it possible to attempt 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 body itself. With sufficient effectiveness of the immune defense, a person even with repeated contact may not get sick. However, with a decrease in its functions, the likelihood of infection increases many times. 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.
Bacteria enter the body through the respiratory system and through wounds. The first type is respiratory droplet. The ability to spread Legionella with water droplets provides its epidemiological characteristics. Basically, all people from the team who work in the same room get sick if their immunity is reduced. The contact path is more rare, although it is not excluded. In this case, the symptoms of legionellosis appear locally, that is, in the area of the wound or skin lesion, 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 was determined that men aged 40 and more are more often and more seriously affected. Women and children are less likely to get sick. This symptom makes it possible to distinguish legionella pneumonia from mycoplasma. Mycoplasmas more often affect young people, regardless of gender.
The clinical course of legionella infection
With a disease such as legionellosis, symptoms occur not from the moment of initial contact, but after the incubation period. It should last about 2-10 days: for a given period of time legionella multiplies in the body, however, the activity of pathological processes is small, which leads to minor (subclinical) symptoms. The infection proceeds either along the easy path, characterized by a flu-like syndrome, or by the type of pneumonia with severe lesions of the respiratory tract.
The first type of course of legionellosis is associated with good protective abilities of the body. As a result of contact with the infection, acute respiratory legionellosis of the type of bronchitis develops. This type of clinical course is called Pontiac fever. The second type of disease course is legionella pneumonia. It is heavier and has a high mortality rate.
It is worth noting that Pontiac fever is an equally serious disease, it is only a less dangerous legionellosis. Legionnaire’s disease (the symptoms of the disease are identical to those of other SARS) is a manifestation of severe course legionellosis pneumonia, which often leads to death for the patient.
In the classification, it is also worth highlighting legionellosis, whose symptoms are the most severe. This alveolitis is a more severe form of pneumonia, enhancing the intoxication of the body and reducing the likelihood of recovery. In this case, 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 hospital legionellosis is valid only if clinical signs appear after 2 or more days from the moment of placement in the inpatient department.
Pontiac fever symptom profile
Pontiac fever is an example of a mild course of a disease such as legionellosis. Symptoms of legionellosis of this nature resemble flu or severe parainfluenza: the patient is worried about the high temperature (38-39 degrees), which appears about 36 hours after initial contact with the infection. Intense muscle and headaches also develop, and a dry cough begins. Occasionally, especially with fever over 38 degrees, vomiting develops.
Against the background of an increase in temperature, the accompanying symptoms worry: thirst, dry mouth, decreased urine. Chest pains also appear, although this symptom is more associated with legionella pneumonia affecting the pleura than with Pontiac fever. Occasionally, against the background of intoxication, photophobia appears, impaired thinking and concentration, 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 health. This makes its own adjustments and may become the basis for an unjustified diagnosis of "meningitis", because this disease also begins as the flu.
Symptoms of Legionnaire Pneumonia
Many symptoms of legionellosis, the disease of legionnaires, 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, muscle weakness, sweating and shortness of breath with a slight exertion, coughing. However, most often the incubation period proceeds only within 2-10 days. Then all the symptoms appear without a prodromal period, that is, also against the background of full health, 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 immunological reactivity of the patient and his physical endurance. The disease is severely tolerated and can lead to death. Initially, a fever of about + 39-40 degrees occurs, which may not be at all if the patient has immunodeficiency associated with HIV or with cytostatic therapy. Along with fever, cough and heaviness in the chest immediately appear. Initially, the cough is only dry, and sputum does not separate.
Along with this, pain in the chest begins to bother almost immediately, because the infection (legionella) causes the appearance of a fibrinous effusion in the pleural cavity and in the alveoli. All legionellosis is dangerous by this: 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, toxic toxic shock, respiratory alkalosis, aggravating the main symptoms and reducing the body's regenerative abilities.
General features of the diagnosis of legionellosis
With an infection such as legionellosis, diagnosis and treatment have their own difficulties. Firstly, without equipment for chromatography or ELISA, it is practically impossible to reliably determine the pathogen. Secondly, even with its presence, the isolation of legionella from sputum is difficult. Thirdly, without the possibility of a reliable determination of the bacteria that caused the disease, the doctor is forced to use beta-lactam antibiotics as a means of empirical antimicrobial therapy.
Legionella is resistant to most beta-lactams due to its intracellular location in the body. It 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 quick as possible. If there is no possibility of laboratory confirmation of the legionellosis pathogen, the doctor is forced to prescribe an empirical treatment regimen using macrolide or fluoroquinolone antibiotics.
Physical diagnosis of Legionnaire pneumonia
Recognizing the disease immediately, due to its relatively low frequency, is almost impossible. In addition, there are about 10 infections that, in the initial stages, resemble legionellosis. Symptoms and treatment of legionellosis for this reason begin with an empirical scheme - the appointment of two or more broad-spectrum antibiotics with maximum coverage of the genera of microorganisms. Physical diagnostics is also carried out here, based on an assessment of the data that can be obtained with a simple examination of the patient.
The first criterion for legionellosis is fever, although it is non-specific. At the first contact with the patient, a rapidly progressing worsening of well-being and an increase in shortness of breath, sometimes up to 40 breaths per minute, are striking. A cough without sputum immediately disturbs. 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 characterization of legionellosis
Also a physical sign is the presence of auscultatory changes. Large areas of the lung, often an entire lobe, are affected by wheezing. Moreover, if purely mechanically assessed legionellosis, the causes, symptoms, diagnosis and treatment will be more obvious. The point is this: mainly the lower lobes are affected, 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 lower right lobe is characterized by the presence of a wide and short lobar bronchus, departing from the main almost directly. Polluting particles get here more often than in the lower left lobe, although this is only statistics, which cannot be an absolutely exact rule.
With physical diagnosis, crepitus is detected. It is often bilateral, which happens infrequently. It should be distinguished with stagnant, moist, bubbly 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 must be supplemented by instrumental and laboratory studies.
Instrumental diagnosis of pneumonia
The two most valuable methods of instrumental diagnostics are the following: bronchoscopy and radiography. More often the second method is available, allowing you to get an image of the tissues of the chest, including inflamed areas. On the x-ray in a direct projection, a fairly large focal shadow is noticeable, which clearly does not correspond to the size of the focus assumed after auscultation.
In the picture, these areas of inflammation are wider, sometimes there are several or they merge with each other. Less common are pleural fibrin overlay in the area of legionellosis inflammation. At the same time, at the stage when, by means of radiography, confirmation has already been obtained that the patient has inflammation of the lung tissue, the doctor may still not suggest 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 flush and get the opportunity 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 bacteria, and their growth. Using the method, it is proved that the pathogenic microbe is 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 that can either independently cause pneumonia or aggravate its course also get into the smear. Therefore, chromatography and enzyme immunoassay are more often used .
Treatment of Legionnaire Pneumonia and Pontiac Fever
The existing protocols of the Ministry of Health and clinical recommendations for pulmonology indicate that bronchitis and pneumonia should be treated with two types of broad-spectrum antimicrobial agents. One of them is either aminopenicillin or cephalosporin. The second type of antibiotic is 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, Ciprofloxacin, Ofloxacin, Moxifloxacin, Gatifloxacin, and Levofloxacin are preferred. Rifampicin and Doxycycline may occasionally be used. The following combination of drugs is prescribed:
- a representative of the beta-lactam group as an element of the empirical scheme - Ceftriaxone, 1 gram intramuscularly twice a day after 12 hours;
- inside macrolide (Azithromycin 500 once a day or Erythromycin 500 6 p / day, or Clarithromycin 500 twice a day, or Midecamycin 400 3-4 times a day);
- fluoroquinolones with the ineffectiveness of the two previous classes of drugs (Ciprofloxacin 400 intravenously 2-3 times a day, Levofloxacin 500 inside 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 (bacteriostatics), it is recommended to use fluoroquinolones in cases of suspected legionellosis or other SARS. Macrolides are only in a high dose and only some of them ("Midecamycin" and "Roxithromycin") can have a bactericidal effect. Even when a balanced and competent antimicrobial therapy regimen is prescribed, the patient needs the support of mechanical ventilation, as well as infusion therapy to correct the toxic toxic shock.
Often, such treatment is carried out in the intensive care unit, where the patient is 3-5 days until the condition stabilizes. Then treatment is carried out in the infectious ward or in pulmonology. Moreover, recovery does not correlate with the results of radiography: infiltrative shadows remain on the images for about a month or more. And the entire treatment of Legionnaire pneumonia lasts about 20 days or more. After discharge, the patient will also have to be monitored, visiting the local GP 4 times a year.