Table 220.3Diagnostic Significance of Findings on Sputum Gram Stain

Stain findingsInterpretation
Gram-positive diplococci & PMNsPneumococcal pneumonia
Gram-positive cocci in clusters & PMNsStaphylococcal pneumonia
Gram-negative coccobacilli & PMNsHemophilus influenzae pneumonia
Gram-negative fat rods with bipolar staining & PMNsKlebsiella pneumonia
Gram-negative slender rods & PMNsEnterobacteriacea, pseudomonas pneumonia
Gram-negative diplococci & PMNsBranhamella catarrhalis pneumonia (rarely, meningococcal)
Mixed gram-positive and -negative cocci and rods & PMNsAspiration pneumonia
Few bacteria seen; many PMNs or mononuclear cellsInfluenza, mycoplasma, or legionella pneumonia
Mixed organisms with squamous cellsSpecimen contaminated with saliva

PMNs = polymorphonuclear leukocytes.

From: Chapter 220, Laboratory Evaluation of Infectious Disease Emergencies

Cover of Clinical Methods
Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.
Walker HK, Hall WD, Hurst JW, editors.
Boston: Butterworths; 1990.
Copyright © 1990, Butterworth Publishers, a division of Reed Publishing.

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