Sputum Culture

Aka: Sputum Culture, Sputum Microscopy, Sputum Cytology, Sputum Gram Stain

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II. Indications: Sputum Examination in Community Acquired Pneumonia

  1. IDSA/ATS recommends Sputum sample obtained for inpatients before Antibiotic therapy
    1. Absence of Gram Negative Rods and Staphylococcus aureus on a good quality Sputum Culture is reassuring
    2. Sputum Culture can help direct subsequent Antibiotic therapy narrowing
  2. IDSA/ATS 2007 indications for Sputum Culture
    1. ICU Admission
    2. Failed outpatient Antibiotic therapy
    3. Cavitary infiltrates
    4. Active Alcohol Abuse
    5. Severe COPD
    6. Pleural Effusion
    7. Positive Legionella urine Antigen (Legionella culture requires special media)
    8. Positive Pneumococcal urine Antigen
    9. Mandell (2007) Clin Infect Dis 44:S27–72 [PubMed]

III. Efficacy

  1. Sputum has low diagnostic yield in Community Acquired Pneumonia
    1. Not recommended in outpatient Community Acquired Pneumonia
    2. Ewig (2002) Chest 121:1486-92 [PubMed]

IV. Technique: Assessing Sputum Sample Quality

  1. Ideal Sputum Sample for Culture
    1. Under 10 squamous epithelial cell per low power field
    2. Many Neutrophils present (>5 per high power field)
    3. Bronchial epithelial cells present
    4. Alveolar Macrophages may be present
  2. Inadequate Sputum Sample
    1. Over 25 squamous epithelial cells/LPM

V. Technique: Sputum Sample Preparation

  1. Pull strand or plug of Sputum onto slide
  2. Consider buffered crystal violet to stain cells
  3. Apply cover slip
  4. View under oil immersion

VI. Approach: Cytology Stains

  1. No Stain
    1. Blastomycosis
    2. Cryptococcosis
  2. Gram Stain
    1. Gram Positive Bacteria
    2. Candida
    3. Tuberculosis (weakly Gram Positive)
    4. Nocardia (weakly Gram Positive)
  3. Direct Fluorescent Antibody Staining
    1. Legionella
  4. Wright stain or Giemsa Stain
    1. Intracellular organisms

VII. Approach: Special Staining Circumstances

  1. Acid-fast Mycobacteria (Tuberculosis)
    1. Ziehl-Neelsen Stain (Red against blue background)
    2. Kinyoun stain
      1. Less reliable than Ziehl-Neelsen stain
      2. Results in quickly stained sample
    3. Fluorochrome dyes (auramine, rhodamine)
      1. Higher False Positive Rate than Ziehl-Neelsen stain
      2. Assist greatly in identifying organisms
  2. Fungal Organisms
    1. PAS staining or Methenamine silver staining
      1. Histoplasmosis
      2. Coccidioidomycosis
      3. Aspergillus
      4. Mucor
    2. KOH Preparation

VIII. Findings: Microscopic

  1. Caseous masses
  2. Dittrich's plugs
  3. Curschmann's spirals (Asthma)
  4. Charcot-Leyden Crystals (Asthma)
  5. Bronchial casts
  6. Concretions
  7. Broncholith
    1. Calcified particles as seen in Broncholithiasis
  8. Lung Cancer cells
    1. Central Bronchus tumors
    2. May require 4 samples to detect
  9. Eosinophils (>5%): identified with Wright's Stain
    1. Allergy
    2. Asthma

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