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| Question | Answer |
| What toxins and other virulence factors does Mycobacterium have? | It doesn't. It lacks classical virulence factors. |
| What samples do we use for testing? | lung tissue, lymph gland, liquid from lungs, milk, feces. |
| What is the staining method we use? | acid-fast staining: Ziehl-Neelson. -No Gram |
| What are cultivation methods for Mycobacterium? | Tissue homogenization with HCl,NaOH 37°C, aerobic, 2-8 weeks. On selective medium with egg yolk. Dry, creamy colonies |
| Name 3 selective mediums for Mycobacterium. Which is the most common? | 1) Harold's 2) Sonenbring 3) Jensen - most common |
| Is Mycobacterium sensitive or resistant usually? | Resistant to all Abs that disrupt cell wall biosynthesis-penicilin. Can be sensitive to Clarithromycin and rifamycin, streptomycin. |
| What is the microscopic appearance? | Gram +, rod shaped and non-motile cells (Marinum is motile) |
| Is it resistant to acid or alcohol? If yes WHY? | It is resistant to both due to the thick outer membrane with lipids, cholesterol and mycolic acids. |
| What are the 2 types of colonies? | Fast- 7 days or less to develop Slow- more then 7 days Most pathogenic are slow. |
| What kind of animals does it affect? | Almost all including humans, fish, ungulates.... |
| Which strain is not pathogenic? | M.smegmatis- saprophytic on lettuce |
| Which strain is motile? What are other different characteristics? | M.marinum- also needs 32°C for 2-4 days! |
| What happened in 1952? | Nobel price (Waksman)- streptomycin. Discovery of Ab’ for disease with professor Waksman |
| 1892? | 1892 Robert Koch identification of the pathogens (M. tuberculosis) |
| Describe the tubercles created by Mycobacterium | Tubercles (granulom) is the place where it replicates in the tissue (e.g lungs)- contains living bacteria covered by epithelia, leukocytes and it replicates creating new tubercles. Once infected lost tissue cant be recovered- or it takes a lot of years |
| Can M.marinum affect the lungs? | No it only stays on skin. |
| What tissue does M.bovis affect? | Lungs and mammary gland |
| Which species infect humans? | M.bovis, M.africanum, M.leprae, M.tuberculosis. |
| Which species infect only animals? | M.avium sbsp paratuberculosis, M.avium sbsp avium |
| Which species infects animals and can spread to humans? | M.bovis, M.marinum |
| Which strain causes Hansen's disease? | Mycobacterium Leprae- leprosy aka Hansen's |
| What is Leprosy? | long term infection by M.leprae that causes granulomas on nerves, skin, eyes and respiratory tract. It results in lack of ability to feel pain with high amount of injuries and wounds that go unnoticed, discoloration and lumps on skin and, in severe cases, disfigurement and deformities. It is spread by cough and fluid from nose of infected person. NOT highly contagious!! |
| What are the methods for detecting and differentiating the mycobacterium strains? | ELISA, PCR |
| Is leprosy treatable? | Most of the times, with multidrug therapy and using of leprostatic agents which affect the proliferation of the bacteria. |
| What does M.avium sbsp paratuberculosis cause? | Paratuberculosis- Johne's disease in CATTLE. Causes weight loss, reduced milk production, diarrhea and death. |
| Which strain affects ONLY ruminants mainly cows (sheep and goats as well)? | M. avium sbsp paratuberculosis |
| Which strain can break the interspecies barrier and be transmitted between almost all species? | M. bovis. Can get to human and other mammals - cattle, deer, pig, cat, fox, omnivores. Rarely horse and sheep. |
| What does M.bovis cause? How is it transmitted? | Tuberculosis in cattle. Transmitted by RAW milk, exhaled air, urine, feces, pus, sputum. |
| Who are more susceptible to TB? | people who smoke and those infected with HIV/AIDS |
| Which strain causes TB? | M. tuberculosis |
| Can TB be treated? | Possible with multiple Abs over long period of time but the resistance is constantly growing with increasing rates of MDR-TB: Multi Drug Resistant-TB |
| What are typical symptoms of TB? | Chronic cough with blood, chest pains, fever, chills, night sweats, decreased appetite, weakness, fatigue, weight loss. Can be asymptomatic- 25% aka Latent TB. |
| If you are infected with TB you can always spread the infection through the air. | Only active TB patients can infect others. LATENT TB patients will not spread the disease. |
| What test do we perform on Mycobacterium? Results? | Cat + Ox - Gram + Motility - & + M.marinum AST- mostly resistant Niacin test + Nitrate reduction test + |
| Why is Gram staining not very helpful for Mycobacterium? | It has a coating of mycolic acid which makes it appear both +/- when stained with Gram. |
| Which strain causes only skin infections? | M. marinum |
| Mycobacterium is known for not producing any toxins or enzymes. What does it produce however to facilitate its growth and replication in the cell? | Mycobactin- attracts extracellular Fe ions into the cytoplasm of the mycobacterial cell. Fe2+ is the food of bacteria. |
| Which test is important for identification of Mycobacteria at species level? | Niacin test. Redox reactions happening in Mycobacterium species produce niacin as a part of energy metabolism. The test detects niacin (nicotinic acid) in aqueous extracts of a culture. M. tuberculosis. Strains that test negative for the niacin test are very rare |
| Which strain can be transmitted to humans through water and contact with fish? | M. marinum |
| Which mycobacterium also has effects on GIT? | M. avium sbsp paratuberculosis |
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