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Exam 1
Mycobacterium
49
Microbiology
Graduate
02/15/2013

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Term
How is Tuberculosis transmitted?
Definition
Droplet Nuclei via coughing, highly communicable
Term
How is the tuberculosis primary infection acquired?
Definition
the person inhales the organisms and they multiply in the alveolar macrophages unaffected by the immune system
Hypersensitivity and cell-mediated immunity develop in 2-6 weeks
Term
What are the typical symptoms of tuberculosis?
Definition
development of a tuberule (microscopic granuloma) in the lung
Term
What is reactive tuberculosis?
Definition
occurs in the lung apex via formation of pulmonary cavities
Term
What is the pathogenesis of tuberculosis
Definition
chronic fever, weight loss, night sweats, blood cough along with an extra-pulmonary disease (dissemination to bones and CNS)
Term
How is tuberculosis diagnosed?
Definition
skin test (PPD) which measured delayed-type hypersensitivity to tuberculoprotein. Tuberculosis can also be diagnosed by serodiagnosis in which the cell-mediated immune response is measured in whole blood samples inoculated with mycobacterial antigens
Term
What is the treatment for tuberculosis?
Definition
combined prolonged drug therapy to prevent resistance (Isoniazid, Rifampin, Ethamtubol and Pyrazinamide), treatment must be directly observed therapy (watch the patient take his drugs)
Term
What is the clinical significance of NTM?
Definition
bacteria can cause non-communicable chronic pulmonary diseases, disseminated diseases and cutaneous infections.
Term
What are the unique characteristics of mycobacteria
Definition
growth rate and recovery time and pigment production in relation to light
Term
What are the 7 safety precautions to be followed while working in a mycobacteria laboratory?
Definition
(1) negative pressure room (2) biological safety cabinet (3) face mask (4) safety cups for centrifugation (5) splash-proof discard containers (6) disposable loops/needles and (7) proper disposal of waste
Term
What is used to digest mycobacteria for processing?
Definition
NALC- N-acetyl-L-cysteine
Term
What is used to decontaminate mycobacteria for processing?
Definition
Sodium hydroxide or benzalkonium chloride and oxalic acid
Term
What is used to concentrate mycobacteria for processing?
Definition
centrifuge
Term
What is used to stop the decontaminate process?
Definition
phosphate buffer
Term
Why do you need to digest, decontaminate and concentrate mycobacteria specimens?
Definition
specimen when plated with be overgrown with normal flora.
Term
What is the procedure of the auramine-rhodamine fluorochrome stain?
Definition
heat fix the slides then flood with auramine-rhodamine fir 15-20 minutes, rinse with DI water, decolorized with 0.5% acid-alcohol for 2-3 minutes, rinse with DI water, flood with potassium permanganate for 2-4 minutes, rinse and allow to dry
Term
What are the advantages to the auramine-rhodamine stain?
Definition
Detection is enhanced against a dark background and the slide can be viewed at a lower magnification allowing for visualization of more fields at one time. Another advantage is that you can re-stain with ziehl-nelson to confirm right on the same slide, you do not need a fresh slide
Term
What are the disadvantages to the auramine-rhodamine stain?
Definition
rapid growers do not always appear fluorescent and you need to confirm with a ziehl- nelson stain. The stained bacteria can also float into the oil and off the slide yielding a false negative
Term
What is the procedure for the Ziehl-neelsen stain?
Definition
heat fix the smear to the slide, flood the slide with carbol fuchsin stain and steam the slides for 1 minute, keep stain on slides for 4-5 minutes, rinse, decolorize with 3% acid-alcohol, rinse, flood with methylene blue for 1 minute, rinse, and let dry. Red is positive for ziehl-neelsen
Term
What is the procedure for the kinyoun stain?
Definition
The procedure is heat fix the slide, flood with carbol fuchsin for 5 minutes, rinse, decolorize with 3% acid- alcohol, rinse, and flood with methylene blue for 1-3 minutes, rinse, let dry.
Term
What is the Runyon classification?
Definition
based on growth and pigment production and is used for NTM
Term
What are schotochromogens?
Definition
develop pigment in the dark or the light
Term
Examples of schotochromogens
Definition
M. scrofulaceum and M. gordonae
Term
What are photochromogens?
Definition
form pigment following exposure to light after being grown in the dark
Term
examples of photochromogens?
Definition
M. kansasii, and M. marinum
Term
What are nonphotochromogens?
Definition
nonpigmented whether grown in light or dark
Term
examples of nonphotochromogens?
Definition
M. avium-intracellulare (MAC, MAI)
Term
Egg-based solid medias
Definition
Lowenstein-Jensen (inhibits normal flora), Lowenstein-Jensen Gruft modification (added antibiotics) or mycobactosel (antibiotics)
Term
Serum/agar based solid medias
Definition
middlebrook 7H10/7H11
Term
liquid media
Definition
Middlebrook
Term
The arylsulfatase test principle
Definition
used to identify potentially pathogenic rapid growers, The enzyme arylsulfatase is present in some mycobacteria and the test is used to determine how fast the bacteria can break down phenolphthaliein disulfate into phenolphthalein which forms a pink color in the presence of sodium bicarbonate.
Term
Which bacteria are arylsulfatase positive?
Definition
M. fortuitum and M. chelonae and slow-growing M. marinum and M. szulgai (14 days)
Term
The catalase test principle
Definition
Most mycobacteria produce catalase which can split hydrogen peroxide into water and oxygen. The test can be used semi-quantitatively in that if the bacteria can produce 45 mm of bubbles in a test tube is in one group of mycobacteria and if it cannot it is another group. The ability of the catalase enzyme to remain active after heating also separates mycobacteria
Term
Which bacteria are catalase negative?
Definition
M. tuberculosis, M. bovis, M. gastri and M. haemophilum
Term
The iron uptake test principle
Definition
utilized to identify rapidly growing mycobacteria capable of converting ferric ammonium citrate to an iron oxide. An LJ slant is inoculated with the organism incubated until visible growth develops, aqueous ferric ammonium citrate added, and the slant incubated for up to 21 days at 37°C. Positive is reddish brown color in the colonies indicates production of iron oxide and Negative shows no color change.
Term
The niacin accumulation test
Definition
bacterium lacks the enzyme necessary to convert niacin to another metabolite in the coenzyme pathway. A positive test is yellow, a negative is clear liquid.
Term
Which bacteria is niacin accumulation positive?
Definition
M. tuberculosis
Term
The nitrate reduction test principle
Definition
The presence of nitrate is detected by production of a red colored product on the addition of several reagents. Development of a pink-red color indicates the presence of nitrite, demonstrating the ability of the organism to reduce nitrate to nitrite. If there is no color then the organism cannot reduce nitrite
Term
Which bacteria is nitrate reduction positive?
Definition
M. tuberculosis, M. kansasii, M. szulgai and M. fortuitum
Term
Tween 80 hydrolysis test principle
Definition
detect lipase that is able to hydrolyze Tween 80 into oleic acid and polyoxyethyated sorbitol
Term
Which bacteria are tween 80 hydrolysis positive?
Definition
Mycobacteria that are positive for Tween 80 hydrolysis are non-pathogenic, slow-growing scotochromogens and nonphotochromogens
Term
Tellurite reduction test principle
Definition
detect species that can reduce potassium tellurite at variable rates. If the bacteria can reduce potassium tellurite in 3-4 days, it is M. avium complex. All rapid-growers reduce tellurite in 3 days.
Term
Inhibition of TCH test principle
Definition
used to distinguish M. bovis from M. tuberculosis because M. bovis cannot grow in the presence of TCH.
Term
The molecular methods used to identify mycobacteria
Definition
DNA hybridization, amplification with reserve hybridization, amplification and restriction enzyme analysis or DNA sequencing and DNA microarrays.
Term
Susceptibility testing methods for M. tuberculosis
Definition
The proportion method uses standardized inoculums (100-300 colonies) to inoculate the agar-based media which contains antibiotics. It is incubated for 3 weeks and if more than 1% of the inoculums survive it indicated resistance. There is broth based susceptibility testing which take 5 days and probes for resistance genes
Term
Susceptibility testing methods for NTM
Definition
MIC methods with aminoglycosides and sulfonamides.
Term
How do you process a sterile specimen?
Definition
centrifuge and use sediment, screen by AFB smear and inoculate one liquid media and one solid media.
Term
How do you process a non-sterile specimen?
Definition
Liquefaction (NALC), decontamination (NaOH), neutralization (buffer or water), centrifugation, screen by AFB smear and inoculate one liquid media and one solid media.
Term
What is the tuberculin skin test?
Definition
used to measure delayed-type hypersensitivity to tuberculoprotein (PPD). A positive test indicates that the person was once infected at some time with M. tuberculosis or cross-reacting strain. The value of the test depends on the incidence of primary infections.
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