Urethritis

This is a photomicrograph of a Gram-stained urethral exudate sample from a male who presented with a case of urethritis. In this particular view, what turned out to be numerous intracellular Gram-negative Neisseria gonorrhoeae diplococci bacteria were evident. Gram-stain is a histochemical technique used by microbiologists to differentiate microorganisms into two large groups, that of Gram-negative, or Gram-positive bacteria. Gram-positive bacteria stain a dark violet-blue, for the crystal-violet stain binds to the exterior cell wall of these organisms. On the other hand, Gram-negative bacteria bind with the counterstain, in this case, the safranin or fuchsin stain. This technique is yet another method by which the trained laboratorian identifies pathogens, in order to come to a diagnostic conclusion. Image courtesy CDC/Dr. Norman Jacobs, 1974. (Photo by Smith Collection/Gado/Getty Images).