Bacterial pneumonia natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Arooj Naz, M.B.B.S

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Overview

Bacterial pneumonia is often transmitted via oral secretions and undergoes a variety of stages including congestion, hepatization and resolution. Symptoms may vary amongst individuals but commonly include abrupt fever, chills, rigors, and cough. Infectious organisms are commonly transmitted via oral secretions containing droplets and the incubation period is generally short and ranges from 1-3 days. Germs can also be transferred by touching unclean surfaces with hands that may later come in contact with the eyes, nostrils, or mouth allowing bacteria to enter the body. There are a multitude of pulmonary and extra-pulmonary complications that contribute to determining the outcome of recovery. Common complications include acute respiratory distress, pleural effusion, sepsis and shock. Prognosis varies according to age and underlying conditions such as bronchiectasis, abscesses, and neoplasms. The CURB-65 scale takes into account confusion, BUN, respiratory rate, blood pressure, and age. A score of 3 or more requires a prolonged hospital duration and has a higher risk of mortality. This criteria has proven to be a useful tool in predicting the outcome of disease.

Natural History

Route of Transmission

• Contamination is via oral secretions containing droplets; this commonly occurs when coughing or sneezing.
• Germs can also be transferred by touching unclean surfaces with hands that may later come in contact with the eyes, nostrils, or mouth allowing bacteria to enter the body.

Incubation period

• The incubation period is generally short and ranges from 1-3 days. This does not however determine the period an individual may experience symptoms for, which may be prolonged due to the development of complications.

Presenting Symptoms

• Common symptoms: abrupt fever, chills, rigors, cough (often productive). If present, the colour of any phlegm may help determine the underlying pathogen but must still be confirmed to treat with the correct antibiotics. Some examples of sputum specifications include:
  • Currant Jelly sputum: Klebsiella
  • Rust coloured sputum: Streptococcus pneumoniae
  • Green sputum: Hemophilus, Pseudomonas
  • Foul smelling/ bad-tasting sputum: Anaerobes
• Other symptoms: pleuritic chest pain, dyspnea, tachypnea, myalgias, generalized weakness and fatigue

Stages

Bacterial Pneumonia progresses through a variety of Stages that include:

1. Congestion: The first stage stage shows a lobe that consists of many neutrophils, some macrophages and serous exudates in the alveoli. Presents on days 1-2 of the infection.
2. Red hepatization: During this period, the lung lobe undergoes consolidation and appears firm resembling the appearance of that of the liver. There is an abundance of neutrophils, macrophages as well as serous exudate. Presents on days 3-4 of the infection.
3. Gray hepatization: The lobe continues to appear liver like but had changed rather than red, no appears slightly gray in colour. Presents on days 5-7 of the infection.
4. Resolution:The final stage of pneumonia is aided by productive cough and/or increased lymphatic drainage in an attempt to “drain” the bacteria and help the lung lobe resolve. Presents around day 8 of the infection.

Complications

• Common Complications:

1. Acute respiratory distress
2. Pleural effusion (unilateral or bilateral)
3. Heart Failure due to Pneumonia
4. Sepsis
5. Septic shock

• Other Complications:

1. Bronchiectasis
2. Pleurisy
3. Empyema
4. Arrhythmias
5. Acute coronary syndrome
6. Endocarditis
7. Encephalitis
8. Meningitis

Prognosis

• There is a relatively good prognosis in patients that are younger with fewer comorbidities and considered generally healthy. As a patients age increases, so does the likelihood of an unfavourable outcome. Antibiotic resistance poses difficulty in adequately treating patients and may affect failure rates.
• The CURB 65 Score is used as a standard score to predict mortality rates following pneumonia infections. A score of 0 -1 is considered low risk and has a minimal risk of death, 2 is generally an intermediate risk requiring a short inpatient hospital stay with an increased risk of 30 - day mortality. A score of 3 or more requires a prolonged hospital duration and has a higher risk of mortality.

Each of the following categories is 1 point:

1. Confusion (new onset)
2. Blood urea nitrogen >7 mmol/L
3. Respiratory rate ≥ 30 breaths/ minute
4. Systolic blood pressure < 90 mm Hg or Diastolic blood pressure ≤ 60 mm Hg
5. Age ≥ 65 years

If patients are non-responsive to antibiotics, a non-resolving pneumonia may develop after a period of approximately 72 hours. In such cases, the mortality increases 5 fold. This subtype of non-resolving pneumonia may appear in two conditions:

1. progressively resolving pneumonia followed by a rapid clinical deterioration or
2. persistent pneumonia that has not displayed clinical stability

Some underlying conditions may prove to exacerbate the development of non-resolving pneumonia. These include (BAD OMEN):

Bronchiolitis obliterans, Bronchiectasis, Influenza B

Age > 60, Aspiration, Abscess, Atypical pathogens eg, Legionella, Mycoplasma, Chlamydia

Drug resistant pneumonia

Opportunistic pathogens

Misdiagnosis (fungal infections, sarcoidosis, Tuberculosis)

Embolism, Empyema

Nosocomial pneumonia, Neoplasm