"For the microbiologic diagnosis of pneumonia, by definition, an infiltrate must be present on a chest x-ray.

A deeply expectorated sputum sample will yield the causitive organism from 20-80% of the time, depending on the study.

Sputum specimens will be rejected by the laboratory if they have >10 epithelial cells per high power field.

The reason is that epithelial cells are usually from the upper airway, and have many adherent bacteria (see photomicrograph).

These bacteria constitute the normal flora of the upper airway, and confuse interpretation of the culture."

Ó 1999- KUMC Pathology and the University of Kansas, used with permission; courtesy of Dr. James Fishback, Department of Pathology, University of Kansas Medical Center.

"Here is the Gram stain of your dreams. Lots of polys, <10 epithlial cells per high power field, and lots of Gram-positive cocci (lancet-shaped, even) that make this most likely a pneumococcal pneumonia."

Ó 1999- KUMC Pathology and the University of Kansas, used with permission; courtesy of Dr. James Fishback, Department of Pathology, University of Kansas Medical Center.