Gray-white Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Gray-white and links to relevant pages within the course.
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| Match each hyaline mold from the drop-down list to its corresponding microscopic and colony description. The microscopic appearance of the molds are illustrated in the image on the right. | View Page |
| Match each hyaline mold from the drop-down list to its corresponding colony and microscopic description. The mold colonies are illustrated in the image on the right. | View Page |
| The infrequently encountered mold that is represented by the photomicrograph begins as a gray-white colony that blackens with maturity as the hyphae become darkened and single, globose, black conidia are produced. This fungus can be identified as: | View Page |
| The dimorphic fungus that may produce black, yeast-like colonies after prolonged incubation at 37°C is: | View Page |
| The colonies shown in the upper image were obtained on blood agar from a sputum specimen after 10 days incubation at 30°C. The lower image is a photomicrograph of a lactophenol blue mount made from a portion of the colony. The diagnosis is: | View Page |
| The growth of the colonies shown in the upper image was obtained on blood agar from a sputum specimen after 8 days of incubation at 30°C. The lower image is a photomicrograph of a lactophenol blue mount made from a portion of the colony. The diagnosis is: | View Page |
| Yersinia pestis Culture Characteristics: Growth at 22-25oC and at 35oC Organism prefers 25oC, so the colonies will grow faster at this temperature Growth occurs on most routine media, including sheep blood agar (SBA), chocolate agar (CHOC), MacConkey (MAC) agar, and routine blood culture media Non-lactose fermenter on MAC agar Growth is slower than other EnterobacteriaceaeColony Morphology on SBA at 35oC: At 24 hours, colonies are pinpoint and translucent with a gray-white color Colonies take on a yellow tint as they age, after 48-72 hours, referred to as a "hammered copper" appearance An irregular or "fried egg" appearance, shown in the lower image, can also be seen at 48-72 hours Characeristic Features: Growth at 22-25oC is a hallmark feature of this organism | View Page |
| Francisella tularensis Culture Characteristics: Slow growing and fastidious Growth of visible colonies on agar may require two to five days Growth is stimulated by CO2 Will grow initially on sheep's blood agar (SBA), but growth is poor or absent on subculture Prefers cystein-enriched media such as chocolate (CHOC), Thayer-Martin (TM), buffered charcoal-yeast extract (BCYE), and thioglycollate (THIO) Growth is slow in broth, so blood cultures should be held up to three weeks if F. tularensis is suspectedColony Morphology on SBA at 35oC: Can grow poorly or not at all on SBA Tiny, pin-point, translucent colonies after 18-24 hours Difficult to see individual colonies in growth that is less than 24 hours Gray-white, opaque colonies less than 1 mm after 48 hours No hemolysisColony Morphology on CHOC at 35oC: Pin-point, gray-white, opaque growth after 24 hours 1-2 mm, gray-white, smooth, shiny growth after 48 hours Individual colonies exhibit mature growth at 3 days in CO2 environment and have a greenish appearance | View Page |
| Which of the following organisms display the characteristic "Medusa head" on sheep blood agar (SBA) after 18 hours of incubation at 35°C? | View Page |
| Yersinia pestis Any isolate with the following features should be immediately referred to your LRN reference laboratory: Gram stain shows fat, gram-negative rods in single or short chains that may demonstrate bipolar staining Faster growth at 25oC Gray-white, translucent colonies on sheep blood agar (SBA) at 24 hours that turn slightly yellow and opaque at 48 hours Irregular colonies that have a "fried egg" and/or "hammered copper" appearance after 48-72 hours Catalase positive Oxidase negative Urea negative Indole negative | View Page |
| Francisella tularensis Any isolate with the following features should be immediately referred to your LRN reference laboratory: Gram stain shows tiny, weak staining, gram-negative coccobacilli Gray-white, opaque colonies on sheep blood agar (SBA) and chocolate (CHOC) agar a at 48 hours Slow growth in broth (up to three weeks) Oxidase negative Urea negative | View Page |
