Infectious diseases Internal Medicine Pulmonology

Pneumonia in Adults

Pneumonia in Adults
Chest X-ray of a pneumonia caused by influenza and Haemophilus influenzae, with patchy consolidations, mainly in the right upper lobe (arrow)

Introduction – Pneumonia in Adults

Approximately 1 person in 100 gets diagnosed annually with pneumonia. The incidence is highest for older people, but also quite high for young children. The prognosis is less favorable for older people, patients with underlying illnesses and in nosocomial pneumonia.

The etiologic agent of pneumonia in the individual patient cannot be predicted with certainty with the help of the clinical picture and x-rays alone. However, epidemiology, physical examination findings, and laboratory tests can often make a certain pathogen appear as the most likely cause.

Causes – Pneumonia in Adults

  • In community-acquired pneumonia, Streptococcus pneumoniae (pneumococci) dominates as the etiological agent.
  • In the society, Mycoplasma pneumoniae is also common, especially in young people.
  • In patients with underlying chronic obstructive pulmonary disease (COPD), pneumococci are the dominant agents, but Haemophilus influenzae and Moraxella catarrhalis are also common. In severe COPD, especially in severe bronchiectasis, pneumonia caused by Klebsiella, Pseudomonas aeruginosa and other gram-negative bacteria also occur.
  • In hospital-acquired pneumonia, a number of different bacteria can be involved – the spectrum depends on the type of ward the patient is being cared for, the length of the care period as well as on underlying illnesses and antibiotic treatment undergone.
  • In immunosuppressed patients, there are a number of opportunistic agents that do not occur in people with normal immune systems.

Pathogenesis, epidemiology – Pneumonia in Adults

  • Most often, pneumonia occurs by aspirating bacteria that colonize the upper respiratory tract, while the defense against bacterial infections in the lower respiratory tract is impaired due to viral infection, impaired cough reflex or local/general immunosuppression.
  • In healthy people – especially in young children – the upper respiratory tract is colonized commonly by pneumococci, H. influenzae, and M. catarrhalis .
  • Pneumococci are the most virulent and therefore the most common cause of pneumonia and by far the most common in severe pneumonia.
  • H. influenzae and M. catarrhalis are more common in patients with chronic lung disease.
  • Hospitalized patients are more often colonized by Staphylococcus aureus and gram-negative bacteria.
  • Respiratory care is associated with a very high risk of pneumonia, ventilator-associated pneumonia.
  • Mycoplasma infection is caused by direct transmission from other people; however, only about 10% get pneumonia, while others get upper respiratory tract infection or bronchitis.
  • Both Mycoplasma and Chlamydophila pneumonia occur, but with greatly increased incidence during epidemics every few years.
  • Legionella pneumophila (and other Legionella species) are normally found in fresh water, but can colonize different types of water plants and spread with humidified ventilation or showers. Infection from water facilities in hospitals is not uncommon.
  • Pneumocystis jiroveci appears to spread between humans but only gives rise to clinical infection in immunosuppressed individuals.
  • Aspergillus and other molds are omnipresent, but do not cause infections in people with normal immune systems.

Symptoms – Pneumonia in Adults

  • The symptoms of pneumonia disease can vary considerably in character and severity.
  • Cough and fever are cardinal symptoms, but in older people, for example, tachypnea, low-grade fever or even just confusion can be signs of severe pneumonia. Toxic symptoms of vomiting and diarrhea are not uncommon.
  • Pleuritic pain occurs and can be severe.
  • Both headache and abdominal pain can dominate the picture. Pulmonary x-rays must, therefore, be performed on broad indications in unclear acute infectious disease.

Clinical findings

  • The degree of general impact can vary widely, from completely unaffected patients (usually young patients with Mycoplasma infection) to septic shock (especially pneumococcal pneumonia).
  • Most patients with pneumonia have an increased respiratory rate, although they appear unaffected. The respiratory rate is correlated to prognosis and should always be noted.
  • Dyspnea and cyanosis can occur in severe pneumonia, especially in patients with underlying cardiac or pulmonary disease.
  • Most commonly, bronchial breathing sounds and rales are present. In lobar pneumonia – primarily suppressed breath sounds and hyporesonance during percussion. In mycoplasmic pneumonia, auscultatory findings are often sparse despite significant lung infiltration.

Differential diagnoses

  • From a therapeutic point of view, pulmonary embolism is the most important differential diagnosis, both in the case of illness at and outside of hospitals. Fairly high fever and moderate to severe laboratory inflammation do not rule out pulmonary embolism. Computed tomography of pulmonary arteries may have to be performed.
  • In hospitalized patients, especially in advanced respiratory care, new lung infiltrates may be due to pulmonary embolism, pulmonary failure, atelectasis, pulmonary hemorrhage, uremia or immunological reactions.
  • However, the most common dilemma is whether there is pneumonia or bronchitis alone, a question usually carrying decisive importance for whether or not antibiotics should be given.

Assessment / Diagnostics – Pneumonia in Adults

  • It is not possible to determine with certainty whether the patient suffers from pneumonia without performing lung radiographs. However, in patients who are treated in primary care and where history and physical examination indicate pneumonia, there is often no reason for further diagnostics, as treatment is usually simple and successful.
  • In more complicated conditions, in hospitalized and in more seriously ill patients, lung radiographs should be performed to ensure the diagnosis and to be able to follow the condition.
  • Blood cultures should be done on all patients who are the subject of hospital care on suspicion of pneumonia
  • Sputum culture is recommended if the patient can cough up mucus.
  • Cultivation from the nasopharynx secretion should be performed in all patients who fail to cough up purulent sputum samples at the emergency department. Findings of pneumococci, but also H. influenzae in a nasopharynx sample should be taken into account as it may constitute a significant etiologic finding.
  • For severely ill patients and in the case of nosocomial pneumonia, bronchoscopy sampling should be considered, but local resources and procedures must be followed here.
  • For markedly immunosuppressed patients, bronchoscopy should be the primary choice.
  • Urine detection of pneumococcal antigen has fairly high sensitivity and high specificity
  • Both Mycoplasma and C. pneumoniae can be detected by PCR from the nasopharynx secretion with high sensitivity and specificity
  • In the case of suspected Legionella pneumonia, both sputum for culture and PCR as well as urine for antigen detection should be taken.
  • Most patients with pneumonia have elevated CRP and WBC, the values ​​being higher in severe pneumonia, especially if it is caused by pneumococci.
  • In very severely ill patients, leukopenia is sometimes present, which is a prognostically unfavorable sign.
  • Hypoxia (blood gas or pulse oximetry), high respiratory rate, circulatory effects, confusion, serious underlying illnesses and, to some extent, high risk of serious illness and should generally lead to hospitalization.
  • Arterial blood gas is of value, especially in chronically ill pulmonary patients, to assess the tendency for carbon dioxide retention.

Treatment – Pneumonia in Adults

  • The choice of therapy is based on the suspected etiologic agent and on the patient’s general condition.
  • In socomial pneumonia in a patient with a fairly good general condition, treatment for pneumococcus, ie penicillin orally, can be given as it is the most important agent. In patients with moderately affected general condition or in patients who have difficulty taking medication orally, benzylpenicillin may be given. Intermediate resistant strains can be effectively treated with amoxicillin or parenteral penicillin G, but not with oral penicillin V. Oral cephalosporins have worse efficacy, while cefotaxime and ceftriaxone have an excellent effect even against the few strains designated as resistant. High-dose PcG also acts as a treatment for these strains.
  • If the patient does not respond to penicillin treatment within 2-3 days, other agents such as Mycoplasma and Legionella should be suspected.
  • If there is a clear suspicion of Mycoplasma or Chlamydophila, tetracycline or macrolides may be given in moderate to severe illness.
  • For critically ill patients, in addition to pneumococci, Mycoplasma and Legionella and also H. influenzae and other gram-negative bacteria, as well as S. aureus, must be considered as possible agents from the beginning – therapy, for example, cefotaxime + erythromycin or benzylpenicillin + quinolone. In suspected Legionella pneumonia, quinolone is probably a better choice than a macrolide.
  • In the case of hospital-acquired infection or pneumonia in immunosuppressed patients, it is generally necessary to provide fairly broad treatment, which is adapted to the type of care of the department, previous antibiotic treatment and the degree and type of immunosuppression.
  • The treatment time should not exceed 7-8 days for community-acquired and hospital-acquired pneumonia in uncomplicated disease courses. For legionella etiology, 10 days of treatment covering Pneumocystis jiroveci is recommended.


  • After treatment for diagnosed pneumonia, some form of follow-up should be performed, clinically or radiologically.
  • If the treatment is completely satisfactory and the patient does not belong to any special risk group, no pulmonary x-ray check needs to be performed.
  • In patients with complicated disease course or risk factors for lung cancer (smoker, exposure to carcinogenic substances) radiological follow-up should be performed.
  • In remarkably severe illness or in recurring cases of pneumonia, immunological diagnostics should be considered.

Further Reading