Alveola, interstitial, atypical pneumonia, aspiration pneumonia and other types

Pneumonia is an inflammatory process of pulmonary tissue in the area of the alveoli, which fill with white and red blood cells, as well as fibrin (a blood protein that forms together with a blood coagel).

It may be due to:

  • an infection,
  • toxic substances,
  • Environmental causes.

Pneumonia was once a common cause of death, but with the introduction of antibiotics, it became a benign disease.
Later, resistant bacterial strains formed due to inappropriate and incorrect use of the antibiotics.

The consequence of this is that pneumonia today is a pathology that is difficult to treat, especially in:

  • hospitalized patients,
  • elderly people.


General, nosocomial and immunosuppression-acquired pneumonia

This distinction is important because the doctor decides on the most appropriate therapy depending on the type of pneumonia.

Community-acquired pneumonia (CAP)

Pneumonia is defined as acquired on an outpatient basis when it manifests itself in a patient:

  • who is not being treated in hospital,
  • who has been hospitalized for less than 48-72 hours.

It is the most common type of pneumonia (60-80% overall).

It is classified into:

  • Mild
  • Moderate
  • Serious

Depending on the season, a distinction is made between:

  • Winter pneumonia, a complication of influenza,
  • mycoplasma pneumonia, which occurs mainly in autumn,
  • Legionella pneumonia, which most often occurs in summer, as it is often caused by air conditioning.

Nosocomial acquired pneumonia

This type of pneumonia is acquired in the hospital, clinic or nursing home.

It can be divided into:

– HAP: acquired in hospital (it is acquired during hospitalization and can be early or delayed depending on the time of its occurrence). It develops at least 48 hours after admission to the hospital or appears 7 days after discharge.

– HCAP: pneumonia related to medical treatment, which occurs in:

  • patients who have been hospitalized for at least 2 days in the last 3 months,
  • patients coming from a nursing home or long-term care,
  • by hemodialysis.

– VAP: Associated with intubation, assisted ventilation and invasive treatments. It occurs less frequently than those mentioned above.

Pneumonia in immunosuppressive patients

This species is caused by viruses, bacteria, fungi and single-celled organisms that are distributed in the environment and are usually harmless to healthy people.

However, they become “pathogenic opportunists” if the patient has a weakened immune system.

Depending on the microorganisms responsible, pneumonia can be:

  • Alveolar
  • Interstitial

It is usually a complication that occurs in conjunction with other diseases that have led to immunosuppression.

Aspiration pneumonia

Patients affected by aspiration pneumonia inhale substances vomited from the stomach.
This occurs especially in older people in nursing homes, less often at home.
Often aspiration pneumonia is caused by gram-negative and anaerobic enterobacteria (whose natural habitat is the intestine).

The cause is the poor general condition of the patient, the consequences are:

  • reduction of gastric acid secretion,
  • esophageal disease (gastroesophageal reflux and stenosis of the esophagus),
  • swallowing disorders,
  • Decreased or absent reflex when coughing. The latter is observed in patients with impaired consciousness or loss of consciousness.

Risk factors for aspiration pneumonia include:

  • Alcoholism
  • Drug abuse
  • Epileptic Attacks
  • Nervous diseases that cause dysphagia (swallowing disorders).

Consequences of aspiration pneumonia are:

  • lung abscess,
  • Empyema (accumulation of pus).

This type of pneumonia is a serious problem and the doctor usually performs percutaneous endoscopic gastrostomy (PEG), which is a surgical procedure in which the stomach is connected outwards to a tube.

In this way, one can deliver food and fluids directly to the stomach without risking them mistakenly entering the trachea instead of the esophagus.

Classification of pneumonia by age

Depending on age, the microorganisms that cause pneumonia differ.

  • Newborn:
    • Chlamydia trachomatis: As a rule, the newborn acquires the infection in the mother’s birth canal. Usually, the first seat of infection in the newborn is the conjunctiva (eye inflammation of the newborn), but it can also be interstitial pneumonia.
    • Streptococcus agalactiae: This bacterium is also found in the mother’s genital tract and may be present without causing symptoms. However, it can lead to severe and fulminant pneumonia and even meningitis in newborns.
  • Children over 1 year of age → Pneumonia is mainly viral (caused by respiratory syncytial virus or parainfluenza virus) or secondary to viral infection by bacteria (e.g. measles).
  • Adults→ The pneumonia is mainly bacterial, but the microorganisms are different from those found in children and vary depending on the condition of the person:
    • healthy
    • inpatient in hospital,
    • immunosuppressed

Alveolar and interstitial pneumonia

Depending on the structure and metabolism, harmful microorganisms are localized:

  1. In the alveoli: These are bacteria with a solid capsule, not suitable for phagocytosis (digestible by white blood cells)
  2. In the interstitium: First of all, one finds:
  • Viruses
  • chlamydia,
  • Mycoplasma pneumoniae.

Alveolar pneumonia

These are inflammations and fluid retention inside the pulmonary alveoli.

Usually the cause is bacterial and the bacteria responsible are:

  • Community-acquired pneumonia: Streptococcus pneumoniae and Haemophilus influenzae (Staphylococcus aureus)
  • Nosocomial Pneumonia (mainly affects people in a clinic who have assisted ventilation, endotracheal probes, etc.):
    • Pseudomonas aeruginosa,
    • Klebsiella pneumoniae,
    • Staphylococcus aureus,
    • Enterobacter,
    • Serratia
    • Escherichia coli.

First of all, enterobacteria are characterized by increased drug resistance because they usually live in the intestine, where millions of microorganisms are present, and here they often acquire plasmids (filaments of DNA in the cytoplasm), which can lead to resistance.

  • Pneumonia caused by environmental contact in a community or hospital: Legionella pneumophila reproduces only in the lungs and does not occur in the upper respiratory tract.

Interstitial pneumonia

It is an inflammation and thickening of:

  • alveolar walls,
  • Alveolar septa (area between two adjacent alveoli).

The result is a reduction in the space available for air inside the alveolus.

Interstitial pneumonia is caused by microorganisms that settle in the interstitium, i.e. in the structures located between adjacent alveoli.

Reasons for this can be:

  • Bacteria: Mycoplasma pneumoniae, Chlamydia psittaci, Chlamydia pneumoniae, Chlamydia trachomatis (in the newborn) and Bordetella pertussis. Chlamydia are intracellular pathogens that, like mycoplasma, are found only inside the interstitial cells.
  • Fungi: Pneumocystis jirovecii. They are the most feared pathogens in AIDS and other immune deficiencies.
  • Viruses: influenza and parainfluenza viruses, respiratory syncytial virus, adenovirus, herpes virus, CMV, measles, VZV, etc. They prefer to affect children and immunocompromised people. Some viruses (influenza, measles, etc.) predispose to secondary bacterial infection.

Necrotizing pneumonia

Necrotizing pneumonia is a serious complication of community-acquired pneumonia.
It is characterized by liquefaction and cavity formation (volatilization) of the lung tissue.
Necrosis can occur in up to 7% of bacterial pneumonia.
It can affect patients of all ages and is increasing in children.

Lobear, lobular , interstitial and abscess-forming pneumonia

Depending on the effect on the lung tissue, it is divided into the following types of pneumonia:

  1. a) Lobar pneumonia → the laboratory examination reveals inflamed alveoli rich in neutrophils and fibrin, while the X-ray shows limited shading on one lobe of the lung. This is typically caused by pneumococci.
  2. b) Diffuse bronchopneumonia (or lobular pneumonia) → there is an irregular spread (inflammation) to different areas of the lung (caused by mycoplasma).
  3. (c) interstitial pneumonia.
  4. (d) lung abscess.

Opportunistic fungal pneumonia

Pneumonia caused by Pneumocystis carinii is an opportunistic infection that affects people suffering from AIDS.

It is the leading cause of death in patients suffering from AIDS.

The first diagnostic examination is the analysis of coughing sputum (sputum examination), followed by bronchoalveolar lavage (BAL).

If a protein material is found in the bronchial aspirate of an HIV-positive person that comes from the inside of the alveoli, the diagnosis of pneumocystosis is as good as confirmed.
To confirm this suspected diagnosis, a Grocott silver impregnation of the material is sufficient.

Perinatal disseminated invasive aspergillosis is typical for premature infants with assisted nutrition and ventilation, which are responsible fungi:

  • Aspergillus flavus,
  • Aspergillus fumigatus.

In premature infants, aspergillosis can enter the blood vessels via a feeding catheter and ventilation catheter.

Atypical pneumonia

Once upon a time, atypical pneumonia was very rare, but for various reasons, it is becoming more common and severe today.
They are caused by:

  • atypical bacteria,
  • Viruses

Often the cause is not clear.
They differ from other pneumonia at the level of:

  • the affected patients,
  • the development of the disease,
  • Symptoms and signs.

Unlike the typical species, these forms cause small epidemics, so the anamnesis and the study of other diseases is very important:

  • within the family,
  • in the environment in which the patient lives.

Often other people are also affected.

They also tend to be very serious and can develop fulminant forms because these microorganisms are much more aggressive than the others.

Usually, their diagnosis is difficult (except in the case of Legionella), because they often affect young and/or healthy people.

In the typical forms, there were harmful microorganisms in the respiratory tract that descended into the lungs, but in this case they penetrate from the outside via a contaminated environmental source, for example:

  • of Legionella,
  • of Q fever through contact with certain animals.

The pneumonia is almost always interstitial, while the classic pneumonia only affected the alveoli.

However, the alveoli are rarely affected here. They can also attack entire lobes of the lungs and long-term consequences are very rare.

The diagnosis is often made on the basis of a chest X-ray, which shows an important inflammation in the interstitial or lobar area.

Pneumonia caused by Legionella or Legionellosis

There are about 20 types of Legionella, but the most important is Legionella pneumophila, because it is the most dangerous and responsible for human legionellosis in 90% of cases.
Transmission occurs via inhalation of contaminated water droplets that form into:

  • Air conditioners
  • hospital equipment used for assisted ventilation,
  • Bathrooms with whirlpool,
  • Gyms

So there are small epidemics:

  • in hotels,
  • in hospitals,
  • on cruise ships.

The risk factors are:

  • Smoke
  • bronchopneumopathies,
  • Immunosuppression.

It can be focal (localized) or affect an entire lobe of the lung

Symptoms include:

Typically, half of these patients suffer from diarrhea and bradycardia.
The clinical and physical examination shows no signs of pneumonia: there is a discrepancy between:

  • the clinical picture (signs and symptoms),
  • the objective thoracic findings.

An X-ray is important to find interstitial compaction (accumulation of fluid).
To establish the diagnosis, it is necessary to isolate the germs responsible: the doctor performs:

  • sputum culture,
  • direct immunofluorescence of the sputum sample,
  • urinary antigen test (less reliable),
  • Look for antibodies in the blood.

As with classic pneumonia, macrolides are very effective, but also:

  • quinolones,
  • Tetracyclines.

Pneumonia caused by Mycoplasma pneumoniae

Mycoplasma pneumoniae is widely used as an agent involved in these atypical forms.
It is a microorganism, very similar:

  • viruses,
  • the bacteria.

It is harmful to the entire respiratory system.
Epidemics within the family are common, the infection almost always comes from school-age children who:

  • inhale it,
  • transmit it via saliva droplets.

Epidemics among soldiers are typical.
Adolescents/adults are often affected and initially it seems to be flu.
The patient has a fever, then his condition progressively worsens.
Initially, bronchitis or interstitial inflammation is caused, after which the inflammation spreads to the alveoli.
The incubation period is 2-3 weeks.

To make a diagnosis, the doctor looks for antibodies.
Mycoplasma pneumoniae provokes the development of auto-antibodies that cause aggregation of red blood cells in cold: cold agglutinins.
An X-ray is required because it is the only examination that can confirm the disease. After that, the doctor looks for antibodies in the blood.
The disease is benign, serious forms are rare.
Rarely, pleurisy is caused.

Pneumonia caused by chlamydia

There are several subspecies of chlamydia:

  1. Chlamydia trachomatis, which leads to infections of the genitals, conjunctivitis and, rarely, endocarditis.
  2. Chlamydia pneumoniae is the subspecies that concerns us and is similar to mycoplasmas
  3. Chlamydia psittaci, which infects chickens and parrots: these are the so-called ornithoses that are transmitted to humans by these animals.

They can lead to serious interstitial forms, but can also be necrotizing.
Chlamydia pneumoniae can also affect the upper airways (nose, throat).

Sometimes the heart or liver are also affected by this pneumonia, especially in
ornithoses (transmitted by birds).
Laboratory tests and also physical examinations are not very helpful.
The main diagnostic elements are:

  • anamnesis to detect whether the patient has had contact with birds that could be carriers of these microorganisms,
  • Thoracic X-ray.

Without treatment, the condition can become very serious.
Pneumonia caused by chlamydia responds well to the antibiotics that are also used in typical pneumonia.

Q fever

This is caused by the bacterium Coxiella burneti from the genus Rickettsia.
It mainly infects:

  • Peasants
  • Cowman.

Q fever has an incubation period of about two weeks.
Symptoms include:

  • remitting fever (which decreases at least once a day, but does not pass),
  • Irritable cough

It is benign.
Usually it has an endemic shape and is due to contact with livestock.

Other forms of pneumonia

Eosinophilic pneumonia
Eosinophilic pneumonia is associated with the accumulation of a large number of white blood cells in the lungs called eosinophils.
These white blood cells strengthen the body’s protection against parasites and pathogens.
Eosinophils can:

  • counteract the effects of allergens, i.e. allergic reactions,
  • Produce substances that damage or kill the parasites.

Infiltration with eosinophils in the lungs occurs when one suffers from:

  • allergy,
  • Infections caused by microorganisms, almost always parasites (ascarids, Ancylostoma dubium, filariae, etc.)

Acute interstitial pneumonia
Acute interstitial pneumonia is a serious and idiopathic (with unknown cause) disease.

Symptoms include:

  • Fever
  • Cough
  • Respiratory insufficiency

Interstitial pneumonia is nonspecific.
The mortality rate is high, 60-70% in the three months after diagnosis.

Hypersensitivity pneumonitis or exogenous allergic alveolitis
The cause is the inhalation of field dust or microorganisms and, more rarely, that of chemicals that:

  • provoke inflammation of the alveoli,
  • prevent gas exchange with the outside world.

An example of this pathology is farmer’s lung, in which the reaction is provoked by thermophilic actinomycetes.

In addition to the typical symptoms of pneumonia, the doctor may hear a diffuse crackling over both sides of the chest during auscultation, especially basal.
That can be:

  • Acute (symptoms appear 6 hours after contact and end about 24 hours after removal of the antigen)
  • Subacute (the symptoms are less pronounced than in the acute form)
  • Chronic (slow and progressive).

The doctor recommends staying away from the allergen.

Radiation pneumonitis
This type of pneumonia occurs after radiation therapy for a tumor.
It occurs after an irradiation period between one and three months, usually asymptomatic, but can lead to a reduced air volume:

  • on exhalation,
  • when inhaled.

The consequences include pulmonary fibrosis, which occurs within 12 months of radiation therapy.

Lipid pneumonia
The usually neoplastic (and focal) narrowing causes stagnation of the surface-active, highly fatty substance (surfactant) inside the lungs.

Uremic pneumonia
It affects people with renal insufficiency and no longer occurs in the Western world thanks to dialysis.
Radiation therapy leads to interstitial fibrosis and extensive dose-related
alveolar damage.

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