A 32-year-old female prostitute is seen at the public health clinic with fever, night sweats, and reports coughing up blood. Her medical history reveals that she is HIV positive and has lost 20 lbs over the past month. Acid-fast bacilli are observed in the sputum. After digestion of the sputum, isolation of the suspected organism is best accomplished by using which one of the following media?
Correct Answer: Lowenstein-Jensen medium
Description: The medium of choice for the isolation of pathogenic Neisseriae is TM agar. TM agar is both a selective and an enriched medium; it contains hemoglobin, the supplement Isovitalex, and the antibiotics vancomycin, colistin, nystatin, and trimethoprim. Vibrio cholerae as well as other vibrios, including V. parahaemolyticus and V. alginolyticus, are isolated best on thiosulfate citrate bile salts sucrose medium, although media such as mannitol salt agar also support the growth of vibrios. Maxi mal growth occurs at a pH of 8.5 to 9.5 and at 98.6degF (37degC) incubation. Lowenstein-Jensen slants or plates, which are composed of a nutrient base and egg yolk, are used routinely for the initial isolation of mycobacteria. Small inocula of M. tuberculosis can also be grown in oleic acid albumin media; large inocula can be cultured on simple synthetic media.Loeffler medium is an enriched nonselective medium used for the cultivation of corynebacteria, especially C. diphtheriae. Horse serum and egg coagulate during sterilization and provide nutrients. This medium enhances the production of metachromatic granules (observed with methylene blue stain). Columbia agar with 5% sheep blood is a general-purpose medium for isolation of a variety of organisms, including fastidious organisms. Along with nutrition, blood agar allows the observation of alpha (incomplete) and beta (complete lysis) hemolysis caused by bacteria.
Category:
Microbiology
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