Mycobacteria: Overview and Characteristics

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Questions and Answers

Which Mycobacterium species is primarily transmitted through unpasteurized milk?

  • M.africanum
  • M.canettii
  • M.bovis (correct)
  • M.tuberculosis

What distinguishes photochromogens from other types of Mycobacterium?

  • They produce pigment only when exposed to light. (correct)
  • They are rapid growers and non-pigmented.
  • They develop pigment only in the dark.
  • They develop pigment without any light exposure.

Which Mycobacterium is known as the 'tap water bacillus'?

  • M.gordonae (correct)
  • M.scrofulaceum
  • M.malmoense
  • M.fortuitum

What is a characteristic feature of rapid growers among Mycobacterium species?

<p>They are all non-pigmented and grow within seven days. (C)</p> Signup and view all the answers

Which Mycobacterium species is specifically associated with causing Buruli ulcers?

<p>M.ulcerans (B)</p> Signup and view all the answers

M.kansasii is known for causing what kind of infection?

<p>Chronic pulmonary infections (D)</p> Signup and view all the answers

Which of the following Mycobacterium species requires hemin for growth?

<p>M.haemophilium (A)</p> Signup and view all the answers

What method is required for the Ziehl-Neelsen stain?

<p>Heating (B)</p> Signup and view all the answers

Which species is classified as a non-photochromogen?

<p>M.avium (B)</p> Signup and view all the answers

Which Mycobacterium species cannot be cultured in vitro?

<p>M.leprae (D)</p> Signup and view all the answers

Which Mycobacterium species is primarily known for its rapid growth and is commonly associated with postoperative skin infections?

<p>M.fortuitum (D)</p> Signup and view all the answers

What type of Mycobacterium produces pigment only under light exposure?

<p>Photochromogen (D)</p> Signup and view all the answers

Which Mycobacterium species is primarily associated with chronic pulmonary infections and is resistant to tuberculosis drugs?

<p>M.avium (C)</p> Signup and view all the answers

Which of the following statements about M.szulgai is true?

<p>It exhibits characteristics of both photochromogens and scotochromogens. (D)</p> Signup and view all the answers

Which Mycobacterium species is primarily found in East Africa?

<p>M.canettii (B)</p> Signup and view all the answers

What is the primary method of transmission for M.tuberculosis?

<p>Respiratory droplets (B)</p> Signup and view all the answers

Which Mycobacterium species is associated with cardiovascular infections after surgery due to heater-cooler contamination?

<p>M.chimaera (A)</p> Signup and view all the answers

Which of the following characteristics describes M.ulcerans?

<p>Leads to Buruli ulcers (A)</p> Signup and view all the answers

Which staining method does not require heating and uses a high concentration of phenol?

<p>Kinyoun Stain (A)</p> Signup and view all the answers

M.gastri, known to be nonpathogenic, is primarily isolated from which source?

<p>Gastric washings (D)</p> Signup and view all the answers

Which Mycobacterium species is predominantly associated with chronic respiratory infections and is known for its yellow pigmentation?

<p>M.kansasii (C)</p> Signup and view all the answers

Which Mycobacterium species primarily affects cattle but can also infect humans, particularly through dairy products?

<p>M.bovis (D)</p> Signup and view all the answers

Identify the Mycobacterium species known for causing inflammation of lymph nodes.

<p>M.scrofulaceum (B)</p> Signup and view all the answers

Which statement is true regarding M.szulgai's pigmentation characteristics?

<p>Its pigmentation varies with temperature, functioning as both a photochromogen and scotochromogen. (A)</p> Signup and view all the answers

Which bacterium is characterized as a skin pathogen that requires hemin for its growth?

<p>M.haemophilium (A)</p> Signup and view all the answers

Which of the following Mycobacterium species is associated with opportunistic infections and typically occurs in individuals with pre-existing lung disease?

<p>M.abscessus (D)</p> Signup and view all the answers

Which Mycobacterium species is part of the M.avium complex and is linked to cardiovascular complications after surgery?

<p>M.chimaera (D)</p> Signup and view all the answers

Which of the following Mycobacterium species is known for causing specific cutaneous conditions in tropical regions?

<p>M.ulcerans (C)</p> Signup and view all the answers

Which Mycobacterium species is classified as a rapid grower and does not produce pigment?

<p>M.chelonae (C)</p> Signup and view all the answers

What is the common feature of obligate aerobes like Mycobacterium species?

<p>They require oxygen for their metabolic processes. (C)</p> Signup and view all the answers

Flashcards

Acid-Fast Bacilli

Bacteria with a unique cell wall structure resistant to standard staining methods.

Lowenstein-Jensen media

Egg-based media used for growing slow-growth mycobacteria, often with malachite green.

Ziehl-Neelsen stain

A staining method for mycobacteria that requires heating.

Mycobacterium tuberculosis

Causes tuberculosis in humans; spread via respiratory droplets.

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Photochromogens

Mycobacteria that produce pigment when exposed to light.

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M. kansasii

Causes chronic pulmonary infections, yellow colour.

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Scotochromogens

Mycobacteria that produce pigment in both light and dark conditions.

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M. scrofulaceum

Causes inflammation of lymph nodes.

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Non-Photochromogens

Mycobacteria that don't produce pigment in either light or dark.

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M. avium

Causes infections, often in AIDS patients; resistant to TB drugs

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Rapid Growers

Mycobacteria that grow within seven days.

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M. fortuitum

Common in postoperative skin infections; found in contaminated water.

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M. leprae

Causes Hansen's disease, (leprosy); cannot be cultured in the lab.

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Acid-fast bacilli

Bacteria with a unique cell wall structure resistant to regular staining methods, requiring special acid-fast stains.

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Lowenstein-Jensen media

Egg-based, slow-growing mycobacteria support media which are often used with malachite green.

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Mycobacterium tuberculosis

Causes tuberculosis in humans via air droplets.

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Photochromogens

Mycobacteria that turn colourful when exposed to light.

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M. kansasii

Causes chronic lung infections, yellow-colored colonies.

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Scotochromogens

Mycobacteria that produce pigment in both light and dark.

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M. scrofulaceum

Causes inflammation of lymph nodes.

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Non-Photochromogens

Mycobacteria that do not produce pigment in any light condition.

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M. avium

Causes infections, often in AIDS patients, resistant to TB treatments.

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Rapid Growers

Mycobacteria that develop colonies within 7 days.

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M. fortuitum

Post-operative skin infection, commonly found in contaminated water.

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M. leprae

Causes leprosy, cannot be grown in the lab.

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Acid-Fast Bacilli

Bacteria with unique cell walls that resist ordinary staining, requiring special acid-fast stains.

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Lowenstein-Jensen Media

Egg-based media used to grow slow-growing mycobacteria, often with malachite green.

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Mycobacterium Tuberculosis

Causes tuberculosis transmitted by respiratory droplets.

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Photochromogens

Mycobacteria that produce pigment only in light.

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M. kansasii

Chronic pulmonary infection with yellow colonies.

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Scotochromogens

Mycobacteria that produce pigment in the dark and light.

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M. scrofulaceum

Inflammation of lymph nodes (often in the neck).

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Non-Photochromogens

Mycobacteria that don't produce pigment in any light condition.

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M. avium

Infections, often in AIDS patients, resistant to TB treatments.

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Rapid Growers

Mycobacteria that develop colonies within 7 days.

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M. fortuitum

Common in post-operative skin infections, contaminated water.

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M. leprae

Causes leprosy (Hansen's disease), cannot be grown.

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Study Notes

Mycobacteria Overview

  • Acid-fast bacilli with unique cell walls. Obligate aerobes, requiring biosafety level 3 containment.

Growth Media and Stains

  • Lowenstein-Jensen medium: Egg-based, uses malachite green, suitable for slow-growing mycobacteria.
  • Middlebrook agar: Faster colony growth detection than Lowenstein-Jensen.
  • Ziehl-Neelsen stain: Requires heat during staining.
  • Kinyoun stain: Uses a high phenol concentration, avoids heating.

Mycobacterium Tuberculosis Complex

  • M. tuberculosis: Causes human tuberculosis, transmitted through respiratory droplets.
  • M. bovis: Primarily infects cattle; humans can contract it from unpasteurized milk.
  • M. africanum: Found in West Africa.
  • M. canettii: Found in East Africa.
  • M. caprae/microti: Primarily infects other animals.

Photochromogens

  • Develop pigment when exposed to light.
  • M. kansasii: Chronic pulmonary infections, creates a yellow bacillus.
  • M. marinum: Skin infections, linked to aquatic environments.
  • M. simiae: Rare respiratory infections.
  • M. asiaticum: Rare pulmonary infections.

Scotochromogens

  • Produce pigment regardless of light exposure.
  • M. scrofulaceum: Causes lymph node inflammation.
  • M. szulgai: Pulmonary infection, pigment production varies with temperature.
  • M. gordonae: Often called "tap water bacillus".

Non-Photochromogens

  • Do not produce pigment in either light or dark.
  • M. avium: Causes infections in immunocompromised patients (e.g., AIDS); resistant to TB drugs.
  • M. ulcerans: Causes Buruli ulcers in tropical regions.
  • M. malmoense: Chronic pulmonary infections.
  • M. haemophilium: Skin and subcutaneous infections; requires hemin for growth.
  • M. gastri: Nonpathogenic; found in gastric washings.

Rapid Growers

  • Non-pigmented, grow within 7 days.
  • M. fortuitum: Postoperative skin infections often from contaminated water sources.
  • M. chelonae: Wound infections, especially post-cosmetic procedures; lacks iron uptake.
  • M. abscessus: Opportunistic in individuals with underlying lung disease.

Other Species

  • M. leprae: Causes leprosy (Hansen's disease); cannot be cultured in vitro.
  • M. chimaera: Part of the M. avium complex; linked to cardiovascular infections post-surgery from heater-cooler contamination.

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