Slide 004 Clinical Presentation and Diagnosis of Tuberculosis
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Patients with cavitary disease usually excrete such large numbers of tubercle bacilli that they can be readily seen with a microscopic examination of a sputum smear. In this case, the Ziehl-Neelsen staining method was used, showing the red carbolfuchsin-stained bacilli against the methylene blue background.

For the tecnologically astute, it may be noted that the staining of this slide is sub-optimal: too high a concentration of methylene blue for the background and too low a concentration of carbol-fuchsin solution to stain acid-fast bacilli was used. We thus get a "weak red on strong blue" instead of the desired "strong red on weak blue".

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Last update: October 1, 2010