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Microbiology > mycobacteria???!!!! > Flashcards

mycobacteria???!!!! Flashcards

1
Q

mycobacteria gram stain poorly why? what is the consequence of this on a gram stain?

A

the mycolic acid / lipids in their cell walls don’t hold/pick up the crystal violet / and safranin

  • ghost cells: faint unstained images
  • gram neutral
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2
Q

what are threee names given to mycobacteria that are nor M leprae or M. tuberculosis?

A

nontuberculous mycobacteria (NTM), mycobacteria other than tuberculosis (MOTT), or atypical mycobacteria

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3
Q

how is primary tuberculosis transmitted, and where does it go to in the body? What can latent organisms lead to?

A

spread via droplet nuclei

latent organisms can reemerge and cause
- secondary/reactivation tuberculosis

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4
Q

what does M. tuberculosis cause that are tumor like, inflammatory lesions? What else are these called?

MTB cells are sometimes called ______? What do they look like?

A

cause granulomas, also called tubercles

MTB cells are sometimes called tubercle bacilli: necrotic centers with a soft, cheesy appearance. caseous

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5
Q

active tuberculosis can cause what disease of the bones? What are symptoms of TB?

A

TB bone disease = Pott’s disease

symptoms of TB: coughing, hemoptysis (coughing up blood), weight loss, and low-grade fever

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6
Q

what is used for the tuberculin skin test? What do positive results look like?

A

Purified protein derivative (PPD), a MTB antigen that MTB people have antibodies to

pos: red, hard area at the injection site within 48 - 72 hrs

pos results do not distinguish between latent and active infections

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7
Q

M. avium complex (M. avium and M. introcellulare) is associated with what disease?

M. avium complex is the most common cause of ______ infections and is resistant to many __________ ______

A

associated with AIDS (GI or disseminated disease)

MAC most common cause of NTM infections and resistant to antimicrobial drugs

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8
Q

the M. fortuitum complex includes what three species of mycobacteria? What kind of infections are these common to see in?

A

M. fortuitum, M chelonae, and M. abscessus

seen in wound infections

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9
Q

M. haemophilum cases what three things, and needs what three things to grow?

A

causes
- skin ulcers
- lymphadenitis
- disseminated disease

needs:
- hemin
-hemoglobin
- ferric ammonium
only grows on chocolate agar

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10
Q

M. kansasii causes NTM pulmonary disease in what areas?

A

Southern/western states (eg Texas, Louisiana, Florida, Missouri, California)

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11
Q

M. leprae causes ________, also known as __________ disease, a disease of the skin, mucus membranes, and peripheral nerves. What animals is it found in?

A

leprosy; Hansen’s disease; foot pads of mice and armadillos

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12
Q

M. marinum causes _________-______ granulomas. Likes to grow in ____ or _______ water

A

swimming-pool granulomas

grows in salt or fresh water

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13
Q

M. scrofulaceum causes what?

A

cervical lymphadenitis

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14
Q

what mycobacteria is the “tap-water bacillus/contaminants”?

A

M. gordonae

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15
Q

what are the parameters of respiratory tract specimens?

A

sputum/bronch washes:
- 3 - 5 cultures on different days
- 5-10 mL
- collected in early morning

sputum must be decontaminated

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16
Q

what are inappropriate AFB specimens?

A

swabs, 24 hr pooled sputum (are more contaminated than non-pooled specimens), 24 hr pooled urine specimens

17
Q

what are the three specimen processing steps for AFBs, and what is done during each?

A

concentration: centrifugation for 15 minutes at 1500 RPMs

decontamination: mycobacteria resist alkaline or acidic chemical agents that kill of normal bacteria due to their high lipid content
- contamination rate of 2 - 5% recommended

digestion: frees the mycobacteria from clumps of protein and allows mycobacteria to sediment during centrifugation

18
Q

What are digestion reagents?

A

NALC + 2% NaOH used within 24 hrs of preparation
- NALC = mucolytic agent
- NaOH = decontaminates specimen

phosphate buffer added: lowers sg of specimens to enhance sedimentation

albumin = helps specimen sediments adhere to solid culture media/microscope slides

19
Q

digestions steps

A

10 mL specimen and 10 mL of NALC-NAOH in conical and vortexed. Left at RT for 15 mins. for the NaOH to decontaminate. Add phosphate buffer, centrifuge for 15 min at 3000g and supernatant decanted. Albumin added to sediment. Acid fast stain.

20
Q

What must be used in conjunction with acid fast smears, and why? How many organisms per milliliter in a culture must be present to be considered positive?

A

cultures must be used in conjunction to acid fast smears because even though they take longer to show AFB growth, they are more sensitive than smears

needs 5000 - 50000 organisms per milliliter in culture to be pos

21
Q

what are the two types of acid fast stains, and what are the two staining procedures for each?

A
  1. carbolfuchsin (contain phenol and fuchsin)
    - Ziehl-Neelson (hot method): pos organisms are red, neg are blue
    - Kinyoun (cold method)
  2. fluorochrome
    - auramine O / auramine-rhodamine: has phenol to penetrate AFB walls
22
Q

auramine-rhodamine stain must sit for ___ minutes and then decolorized with ____ for 2 minutes. Acid fast organisms are ______ color. The slide is counterstained with _______ or ________

A

15 minutes

decolorized with acid-alcohol for 2 minutes

AFBs are yellow - yellow-orange

counterstain with potassium permanganate or acridine orange

23
Q

Carbolfuchsin-stained smears should be looked at how many fields / how many passes? What about for Fluorochrome stained smears?

A

C smears: 300 fields, 3 long passes and 9 short passes

F stain: 30 fields, 3 long passes

24
Q

what are five egg-based media, and what do they all have that inhibit contaminating organisms?

A

nonselective:
1. petragnami (very high conc. of malachite green)
2. ATS (low malachite green)
3. Lowenstein-Jensen medium: most commonly used egg medium

selective:
1. LJ-Gruft
2. mycobactosel-LJ

all have malachite green

25
Q

agar based media for AFBs have a variety of nutrients and little malachite green. What are the selective and nonselective types?

A

nonselective:
1. middlebrook 7H10 and 7H11

selective:
1. mitchison’s 7H11
2. Mycobactosel-middleblrook 7H11

26
Q

liquid media for ABFs contain what? What does this do? What are the kinds of liquid media?

A

has tween 80: surfactant that breaks up clumps of AFB so the organisms can disperse throughout media. Mycobacteria grow faster in liquid media

types:
- dubos tween albumin broth
- middlebrook 7H9, 7H12, 7H13

27
Q

most mycobacteria grow at what temps? Which ones have a lower optimal temp? What do we do when we suspect these organisms?

A

most grow at 35 - 37º C

lower temp: M. marinum, M. haemophilium, M. fortuitum complex, and M. ulcerans

two sets of media:
- one at normal AFB temp
- one at 24 - 35º C for the AFBs above minus M. fortuitum

28
Q

middlebrook media must be incubated in ____

A

CO2

29
Q

what are the three kinds of chromogens (photoreactivity test where AFBs produce carotenoid pigments)

A

photochromogens: produce yellow to orange pigments in the light only

scotochromogens: make deep yellow to orange pigments in the light and dark

nonphotochromogens: make no pigment at all. (look buff, tan, pale yellow colonies)

30
Q

nearly all mycobacteria are ________ positive, but what are the three tests that can help differentiate the kinds of mycobacteria?

A

catalase pos

  1. heat stable 68ºC catalase: some mycobacteria can be heated to 68ºC while other cat pos ABFs will be inactivated
    - uses Tween 80 H2O2
    - bubbles in heated or non heated tube is pos result
  2. semi-quantitative catalase:
    - tween 80 H2O2 added to LJ slant and height of bubbles made is measured
  3. drop method:
    - some isoniazid resistant MTB are cat neg, where no bubble means INH resistance
31
Q

iron uptake: some mycobacteria can convert _______ _________ _____ to ______ _____. What do pos results look like?

A

some mycobacteria can convert ferric ammonium citrate to iron oxide

pos results: rusty to red-brown color on a tan medium

32
Q

all mycobacteria can produce _________ (nicotinic acid), but only some can turn it into _______ (precursor to NAD).

Steps: grow AFB on LJ slant for many weeks, add water, wait ____ minutes, add ______ ______ and ________. What color is a pos result?

A

niacin to nicotinic acid mononucleotide

Steps: grow AFB on LJ slant for many weeks, add water, wait 15 minutes, add cyanogen bromide and aniline.

Yellow pos result

33
Q

Nitrite reduction test reagents are what three things (that are added to mycobacterial isolate with nitrite substrate for 2 hrs)?

A
  1. dilute HCl to acidify the medium
  2. sulfanilamide
  3. N-naphthylethlenediamine hydrochloride

add zinc if red color doesn’t appear

34
Q

pyrazinamidase (PZA) is an enzyme that deaminates pyrazinamide to form what two things? How is a pos pink color made?

A

pyrazinamide to
1. pyrazinoic acid
2. ammonia

the pyrazinoic acid with ferrous ammonium sulfate makes a pink color

35
Q

what are the MTB complex AFBs?

A
  • M. tuberculosis
  • M. bovis
  • M. africanum
36
Q

what are the two photochromogens?

A

M kansasii
M. marinum

37
Q

what are the three scotochromogens?

A

M. gordonae
M. scrofulaceum
some M. xenopi

38
Q

what are the four nonphotochromogens?

A

M. avium complex
M. haemophilum
M. ulderans
most M. xenopi

39
Q

what are the fast grower AFBs?

A

M fortuitum complex
- M. fortuitum
- M. chelonae
- M. abscessus

Microbiology (9 decks)

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