Histologic-type stains are used daily in the microbiology laboratory; most often Gram stain and acid-fast stain (Ziehl-Neelsen or its modifications). Both of these stains detect certain bacteria and to some extent help identify them. Other histologic stains perform the same purpose in tissue slide examination; the most common are paraaminosalycylic acid (PAS) and silver stains for fungi. Immunohistologic stains containing antibody against organism antigen can be used on smears or histologic slides to identify organisms, although this is not frequently done.