Questions and Answers
What is the typical size range of Mycobacteria?
What characteristic is used to identify acid-fast bacteria?
What type of media is recommended for the primary culture of mycobacteria?
Which component helps neutralize the toxic effects of fatty acids in semisynthetic agar media?
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Which of the following staining techniques demonstrates mycobacteria using fluorescence?
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What is a common limitation of staining mycobacteria with common aniline dyes?
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What is the role of selective media in culturing mycobacteria?
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Which of the following is NOT a characteristic of mycobacteria?
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Study Notes
Morphology and Identification
- Mycobacteria are slender, straight rods approximately 0.4 x 3 µm in size.
- Exhibit variable morphology, including coccoid and filamentous forms, depending on the species.
- Do not efficiently stain with standard aniline dyes; appear as "Gram-invisible" or clear zones (often referred to as "ghosts").
- Certain mycobacteria may be identified as beaded Gram-positive rods, though branching is usually absent.
- Other bacteria with acid-fast staining characteristics include Nocardia, Rhodococcus, Gordonia, and Tsukamurella.
Ziehl-Neelsen Technique
- A staining method specifically for detecting acid-fast bacteria, crucial in identifying Mycobacterium species.
- Mycobacteria exhibit yellow-orange fluorescence when treated with fluorochrome stains, enhancing visibility.
- Fluorochrome stains are preferred for clinical specimens due to their efficacious detection of acid-fast bacteria.
- Advanced fluorescence microscopy, utilizing ultrabright LED microscopes, has improved the provision of diagnostics in resource-limited settings.
Culture
- Primary culture of mycobacteria requires both nonselective and selective media to ensure appropriate growth conditions.
- Selective media incorporate antibiotics to inhibit the proliferation of contaminating bacteria and fungi.
- Various formulations can be deployed for both nonselective and selective media applications.
Semisynthetic Agar Media
- Middlebrook 7H10 and 7H11 are examples of semisynthetic agar media enriched with essential nutrients.
- These media contain defined salts, vitamins, cofactors, oleic acid, albumin, catalase, and glycerol.
- Casein hydrolysate is included in the 7H11 medium, providing additional nutrients.
- Albumin acts to neutralize the toxic effects of fatty acids present in the media, promoting mycobacterial growth.
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Description
Explore the fascinating morphology and identification characteristics of Mycobacterium tuberculosis. This quiz covers the typical organisms, their unique staining properties, and variations in morphology. Test your knowledge of the significant features that define these bacteria.
