Aspiration pneumonia bacterial infection

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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]

Overview

Aspiration pneumonia caused by bacterial infection is the commonest subtype of aspiration pneumonia. The other subtypes being chemical pneumonia, and airway obstructions.

Causes

• Normal flora of upper airways, gingival cavity or stomach.
• Caused by less virulent bacteria, such as aerobic or microaerophilic streptococci (commonest) and anaerobes (second common cause) such as
  • Peptostreptococcus
  • Fusobacterium nucleatum
  • Prevotella
  • Bacteroides

History and symptoms

The manifestation depends on:

• The bacteria involved
• Time since aspiration to diagnosis
• Immune status of the host

Symptoms in aerobic microbes

• Abrupt or Indolent course
• Productive cough
• Fever
• Absence of chills and rigors
• Dyspnea
• Anorexia, weight loss
• Anemia

Lab diagnosis

Sputum culture

• Expectorated sputum is not used as an diagnostic tools as contamination by the normal flora of the mouth and airways is inevitable.
• Specimen obtained via bronchoscopy may be suitable but limited studies are available to prove this.

Symptoms in anaerobic microbes

Clinical features, which are characteristic of aspiration pneumonia involving anaerobic bacteria, include:

• Indolent course
• Presence of risk factors: altered sensorium (anesthesia, alcohol, drug, trauma, dysphagia, dental caries)
• Putrid sputum
• Absence of chills and rigors

Chest X Ray

• Lung abscess
• Empyema
• Involvement of dependent pulmonary lobes i.e., upright position lower lobe, superior segment of lower lobes or posterior segment of upper lobes in recumbent position

Natural History, Complications and Prognosis

• Lung abscess
• Necrotizing pneumonia
• Empyema
• Bronchopleural fistula

Risk factors

• Poor dental hygiene is a risk factor
• Patients with good dental hygiene and edentulous are less predisposed