Editing Broad-spectrum antibiotic (section)

== Bacterial targets ==
Antibiotics are often grouped by their ability to act on different bacterial groups. Although bacteria are biologically classified using [[Bacterial taxonomy|taxonomy]], disease-causing bacteria have historically been classified by their microscopic appearance and chemical function. The morphology of the organism may be classified as [[Coccus|cocci]], [[Diplococcus|diplococci]], [[bacilli]] (also known as "rods"), spiral-shaped or pleomorphic. Additional classification occurs through the organism's ability to take up the [[Gram stain|Gram stain and counter-stain]]; bacteria that take up the crystal violet dye stain are referred to as "gram-positive," those that take up the counterstain only are "gram-negative," and those that remain unstained are referred to as "atypical."  Further classification includes their requirement for oxygen (i.e., aerobic or anaerobic), [[Hemolysis (microbiology)|patterns of hemolysis]], or other chemical properties. The most commonly encountered groupings of bacteria include gram-positive cocci, gram-negative bacilli, atypical bacteria, and anaerobic bacteria.<ref name=":1">{{Cite book|title=Harrison's principles of internal medicine. |isbn=9780071802154|edition=19th |location=New York|oclc=893557976|last1 = Kasper|first1 = Dennis L.|last2=Larry Jameson|first2=J.|last3=Hauser|first3=Stephen L.|last4=Loscalzo|first4=Joseph|last5=Fauci|first5=Anthony S.|last6=Longo|first6=Dan L. | name-list-style = vanc |date=2015-04-08}}</ref>