Darkfieldmicroscopy

Dark-Field Microscopy. Examined under a dark-field microscope at ×40 or ×100 power, spirochetes appear as motile, bright corkscrews against a black background. (Reproduced with permission, from Morse SA, Holmes KK, Ballard RC, Moreland AA (eds). Atlas of Sexually Transmitted Diseases and AIDS. 4th ed. Saunders Elsevier; 2010. Copyright © 2010 Elsevier, Ltd.)

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Köhlerillumination

Brightfield illumination has been one of the most widely used observation modes in optical microscopy for the past 300 years. The technique is best suited for utilization with fixed, stained specimens or other kinds of samples that naturally absorb significant amounts of visible light. Images produced with brightfield illumination appear dark and/or highly colored against a bright, often light gray or white, background. This digital image gallery explores a variety of stained specimens captured with an Olympus BX51 microscope coupled to a 12-bit QImaging Retiga camera system and a three-color liquid crystal tunable filter.

Compound microscope with dark-field condenser (dark-field microscope), glass microscope slide, coverslip, and physiologic saline.

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From chancre or condyloma lata: Gently abrade the lesion with a dry gauze. Dab away any bleeding. Touch slide to exudative fluid in base of lesion. Overlay coverslip and view immediately under dark-field microscope using ×40 and ×100 objectives. From mucous patch: Touch slide to mucous patch. Overlay coverslip and view immediately under dark-field microscope using ×40 and ×100 objectives. From skin lesion: Gently scrape surface of skin lesion with edge of a number 15 scalpel blade. Dab away any bleeding. Touch slide to exudative fluid rising from skin lesion. Overlay coverslip and view immediately under dark-field microscope using ×40 and ×100 objectives.