DIAGNOSTIC MEDICAL MICROBIOLOGY
For diagnostic bacteriology , it is necessary to use several types of media for routine culture, particularly when the possible organisms include aerobic, facultatively anaerobic, and obligately anaerobic bacteria. The specimens and culture media used to diagnose the more common bacterial infections.
The standard medium for specimens is blood agar , usually made with 5% sheep blood. Most aerobic and
facultatively anaerobic organisms will grow on blood agar . Chocolate agar , a medium containing heated blood with or without supplements, is a second necessary medium; some organisms that do not grow on blood agar,including pathogenic Neisseria and Haemophilus, will grow on chocolate agar. A selective medium for enteric gram-negative rods (either MacConkey agar or eosin-methylene blue [EMB] agar) is a third type of medium used routinely. Specimens to be cultured for obligate anaerobes must be plated on at least two additional types of media, including a highly supplemented agar such as brucella agar with hemin and vitamin K and a selective medium containing substances that inhibit the growth of enteric gram-negative rods and facultatively anaerobic or anaerobic gram-positive cocci.