Definition of pneumonia is a group of acute etiological, pathogenesis, and morphological characteristics of acute focal infectious and inflammatory diseases of the lungs with the primary involvement of the respiratory departments in the pathological process and the mandatory presence of intra-alveolar inflammatory exudation.
We will analyze this definition:
· Whenever people speak of pneumonia, they mean an acute illness. Therefore, in the concept of acute pneumonia, the word acute is superfluous.
· Pneumonia is always a focal disease. The concept of kruppoznaya pneumonia has historical significance. Therefore, the concept of focal pneumonia does not apply.
· Pneumonia is an infectious disease.
· Alveolar inflammatory exudation – there is always a limited involvement in the process of alveoli. There are no interstitial pneumonias (this is either overdiagnosis – incorrect interpretation of images, poor-quality images, or the alveolitis phase is not detected – the patient was treated for several days at home). Pneumonia is always a local alveolitis, even if this phase is not captured.

The classification of academician Molchanov, 1962, is very common.
Now adhere to the etiopathogenetic classification (classification). This classification is very simple, but very easy to apply in practice.
1. Common (community-acquired) pneumonia – make up the majority of pneumonia. The diagnosis is made if the patient falls ill at home.
2. Nosocomial (nosocomial) pneumonia. Here, as a rule, endogenous infection takes place. It is clearly indicated that pneumonia is diagnosed at least 48 hours after admission to the hospital. This group is divided into pneumonia that occurs in persons in nursing homes, psychiatric hospitals, etc. In fact, these patients are seriously ill with some other disease.
3. Aspiration pneumonia. This in no case can be attributed to gasoline pneumonia. These are pneumonia caused by aspiration of acidic gastric contents, with which various flora penetrate.
4. Pneumonia in people with severe immune defects (congenital immunodeficiency, HIV infection, etc.).

The relevance of the problem.
Incidence: according to academician A.G. Chuchalin (chief pulmonologist of the Ministry of Health of the Russian Federation) – from 3 to 8 per 1000 population, according to the European Respiratory Society and the American Thoracic Society – 4.7 – 12. By this criterion it is difficult to say, because the reversibility is different, not everyone is diagnosed with pneumonia.
Mortality is a fairly reliable indicator – 2-3% as a whole. With certain forms of pneumonia, especially the so-called hospital secondary, it reaches 50-60%. Frequency of occurrence and level of clinical diagnosis of pneumonia according to autopsy in St. Petersburg hospitals for the period 1993-1995 – 15633 autopsy. In a fairly large percentage of cases, pneumonia is not diagnosed.
The causes of hypodiagnosis of pneumonia are: objective – short duration of hospital stay, severity of the condition – 50-60%, subjective – as a rule, incorrect interpretation of the x-ray picture in the lungs.

It varies in dependence on the pathogenetic variant of pneumonia. Due to objective and subjective reasons, in almost 100% of cases, the doctor has to prescribe antibacterial therapy, not knowing which flora caused the disease. Therefore, it is very important to know the flora that dominates with various etiopathogenetic variants of pneumonia. In the case of hospital pneumonia, one must know the nosocomial strains.
The causative agent is not found in approximately 30-50% of common pneumonia. For practical reasons, in patients over 65 years old and / or suffering from concomitant diseases (COPD, diabetes mellitus, etc.) along with Str.pneumonie and Haemophilus Influenza, aerobic gram-negative microorganisms (Klebsiella, Staphilococcus aureus, etc.) occupy a special place.
In the case of hospital pneumonia, gram-negative microbes and golden pneumococcus are more common.
With aspiration pneumonia, Gr-flora, E. Coli is more common.
With pneumonia in individuals with severe immunodeficiency, cytomegalovirus, pneumocysts, etc. are detected.

Groupings of pneumonia in severity.
Criteria for extremely severe pneumonia:
· Pronounced intoxication with cerebral and neurological disorders (acute psychosis, soporous conditions with respiratory disorders, meningitis, etc.)
· Acute severe and recurrent vascular and cardiovascular failure (severe collapse, cardiac asthma, edema lungs).
· Pronounced respiratory failure with impaired CBS and hypoxemia.

Mycoplasmal pneumonia can only be proved by immunological methods (serological blood tests – an increase in antibody titer by 4 times in repeated sera) – however, this has epidemiological significance.