PMNs = polymorphonuclear leukocytes.
 |
| Stain findings | Interpretation |
|---|---|
| Gram-positive diplococci & PMNs | Pneumococcal pneumonia |
| Gram-positive cocci in clusters & PMNs | Staphylococcal pneumonia |
| Gram-negative coccobacilli & PMNs | Hemophilus influenzae pneumonia |
| Gram-negative fat rods with bipolar staining & PMNs | Klebsiella pneumonia |
| Gram-negative slender rods & PMNs | Enterobacteriacea, pseudomonas pneumonia |
| Gram-negative diplococci & PMNs | Branhamella catarrhalis pneumonia (rarely, meningococcal) |
| Mixed gram-positive and -negative cocci and rods & PMNs | Aspiration pneumonia |
| Few bacteria seen; many PMNs or mononuclear cells | Influenza, mycoplasma, or legionella pneumonia |
| Mixed organisms with squamous cells | Specimen contaminated with saliva |
PMNs = polymorphonuclear leukocytes.