Microbiology - Mycobacteria

Front 1

Truly acid fast vs partial

Back 1

Acid fast organisms retain their stain & resist decolorization with HCl

Partially acid fast (nocardia) resist decolorization by H2SO4 but lose it after HCl

Front 2

Why is it bad to spit in public

Back 2

mycobacteria! have lots of lipid in their cell walls and can live forever in spit

and it's gross

Front 3

media?

Back 3

Lowenstein-Jensen agar

for mycobacteria

Front 4

Back 4

Tb

"Buff-colored and heaped"

Front 5

What is MOTT

Back 5

Mycobacteria other than TB

(used to be called atypical mycobacteria)

Front 6

How do we classify mycobacteria

Back 6

Runyon system
4 groups based on pigment in light, dark, and growth rate
(not TB)

Front 7

Runyon system

Back 7

I: Photochromogens. turn yellow after light exposure.

II: Scotochromogens. Always yellow.

III: Non-photochromogens. Always beige.

IV: Rapid growers: Grow within 7 days

Front 8

Examples in each Runyon class?

Back 8

I: Photochromogens: M kansasii, M. marinarum, M. simiae, M szulgai

II: Scotochromogen: M. gordonae, M. scrofulaceum

III: Non-photo: MAI, M. haemophilum

IV: M. fortuitum, M. abscessus, M. chelonei

Front 9

Which mycobacteria is scotochromogen (always yellow) at 37C but photochromogen (yellow only after light) at 25C?

Back 9

M. szulgai

Front 10

T/F: Some strains of MAI can be pigmented.

T/F: M. kansasii can be I, II, or III.

Back 10

True, most often in AIDS patients.
(MAI is normally considered a Runyon III NON-PIGMENTED)

True. though it is usually I.

Front 11

Proper specimen type for sputum or urine for mycobacteria?

Back 11

3-5 early morning specimens

Front 12

What is the problem with gastric samples for mycobacteria?

Back 12

Acidic. Must neutralize the pH in the lab.

fyi these samples are mostly in kids

Front 13

Steps of specimen processing in mycobacteria

Back 13

1. Decontamination (must kill contaminating bacteria, by raising pH to 8.6)
2. Buffer (Return to pH 7)
3. Centrifugation
4. Slide prep
5. Agar choice

Front 14

How are specimens decontaminated? What is different in CF patients?

Back 14

15 minutes only:
NaOH: raises the pH
+ NACL (n-acetylcystein) breaks up the mucus

in CF: oxalic acid is used due to pseudomonas

Front 15

What speed do you centrifuge mycobacteria to make the pellet?

Back 15

3000 x

Front 16

2 main agar types for mycobacteria?

Back 16

Lowenstein-Jensen (green) egg based
STERILIZE BY INSPISIDATION

Middlebrook agar: clear, synthetic, can do susceptibilities

Front 17

What 2 stains could this be?

Back 17

Zeehl-Nielsen (old method - used heat)
Kinyoun: cold stain, uses phenol to drive stain into AFB.

Both stain RED

Front 18

What stain is this?

Back 18

Auramine rhodamine stain. Fluorescent. stains orange-y.

Front 19

T/F: PCR amplification of mycobacteria can be used for both diganosis of disease and monitoring treatment effect.

Back 19

False. Used for diagnosis. NOT for treatment - dead DNA can hang around and a patient can be cured but have a + PCR for up to 6 months

Front 20

What temperature do we incubate mycobacteria?

Bacteria?

Fungi?

Back 20

37C

bacteria @ 35

fungi at 30, or 25 (room temp)

Front 21

How long do we have to keep mycobacteria cultures?

Back 21

6-8 weeks

Front 22

What are the classic tests to ID TB?

Back 22

Niacin accumulation + (must be taken from LJ agar! due to eggs)

Nitrate reduction +

Front 23

How to ID M Tb vs M bovis?

Back 23

TCH (T2H) growth seen in M tb but not M bovis

M bovis is Niacin + but nitrate - (tb is +/+)

Front 24

What is the name of the type of growth that Tb shows in colonies?

Back 24

Cording factor
Forms rope-like colonies on Middlebrook
Due to very high lipid content in Tb

Front 25

Does Tb grow in NAP?

Back 25

NO. all mycobacteria grow in NAP except TB (this is a silly question on an automated test, but has been asked on boards)

Front 26

Back 26

Barnsdale ulcer
M. ulcerans

painless boil --> ulcer --> avasc coag necrosis

Front 27

Cavitary lesion in the lung
Positive AFB smear
Niacin -, nitrate +

Back 27

M. kansasii!

Photochromogen (yellow > light)
Clinically mimics Tb

Tb is Niacin+ and nitrate +, and not a chromogen

Front 28

Swimming pool granuloma
No growth at 37C; growth at 30C

Back 28

M. marinum

(skin lesions like colder temps - grows at 30C)
PHOTOCHROMOGEN

Traumatized skin exposed to water (pools, fish tanks) and can mimic sporotrichosis with spread up the arm in lymphatics

Front 29

Original cause of scrofula (Mycobacterial cervical lymphadenitis)

Back 29

M scrofulaceum
SCOTOCHROMOGEN

(now scrofula is usually caused by TB)

Front 30

Egg nest colony on Middlebrook agar?

Back 30

M. xenopi
scotochromogen
grows in hot water

Front 31

Positive AFB in stool

Back 31

MAC (avium * intracellulare complex)
AIDS and old ladies that smoke
Disseminated
Dx wtih DNA probe

**usually a non-photochromogen but in AIDS it can have yellow color

Front 32

Rapid growing AFB (3-5d) that is arylsulfatase positive

Back 32

M. fortuitum/chelonea complex

Found in environment

Front 33

Sporotrichoid spread

Back 33

M. marinarum (swimming pool granuloma)

M. fortuitum/chelonae complex (rapid growers)

Front 34

Mycobacteria that is always a laboratory water contaminant

Back 34

M. gordonae

Front 35

Mycobacteria that is weakly associated with Crohn's disease

Back 35

M. paratuberculosis

Front 36

Subcutanous painful nodules in AIDS patients; organism requires heme to grow

Back 36

M. haemophilum

Front 37

Mycobacteria that can grow at 52C

Back 37

M. thermoresistible

Front 38

Back 38

M. leprae
acid fast
"cigar packets"

Front 39

Stain classically used for M. leprae and rhodococcus?

Back 39

Fite stain

Front 40

Animal reservoir of M. leprae

Back 40

Armadillos

(colder body temperatures; M. leprae likes 27-30C, which is why it commonly involves the extremities)