Mycobateriacae- Part I

Question 1

Where is mycobacteriacae found?

Answer 1

water, soil, and animals.

Question 2

Describe mycobac

Answer 2

they are aerobic, non spore forming
slow growing
gram stain= beaded gram positive rod
It has a high lipid content (difficult to pick up on aniline dyes and will NOT be seen on a gram stain)

Question 3

What is “Acid fast”?

Answer 3

organisms resist decolorization by acid alcohol. It distinguhes other mycobateria from each other.

Question 4

What do mycobacteria require for growth?

Answer 4

prefer CO2 for cell growth, optimal temp is 35-37, and range = 2 days to 8 weeks to grow

Question 5

Why is safety so important to handling mycobacteria?

Answer 5

Serious nature of mycobacterial disease (particularly TB), health care workers are at risk fit for contracting TB, MINIMAL CHANCE OF INFECTIONS WHEN PROPER PRECAUTIONS ARE USED.

Question 6

Describe specimen collection?

Answer 6

sterile disposable container, collect before antibiotic therapy, deliver promptly to lab, refrigerate if delay in delivery, SWABS NOT ACCEPTABLE IN MOST LABS

Question 7

What can you use for specimen types for mycobacteria?

Answer 7

Respiratory, Urine, Gastric Lavage, Feces (not acceptable), Wound drainage, Blood, Body fluids, Tissues

Question 8

How much sputum needs to be collected for a sample?

Answer 8

recommend minimum of 3 to 5 EARLY MORNING specimens on consecutive days because there is irregular and intermittent release of mycobacteria into bronchial lumen. THERE SHOULD BE NO POOLED SPECIMENS

Question 9

Describe urine specimens

Answer 9

3-5 early morning midstream or catheterized specimens. Centrifuge to concentrate specimen.

Question 10

When do you get a gastric lavage specimen?

Answer 10

When you are unable to obtain a sputum sample. Preferred specimen for children. However, you need to neutrilize the acid in the specimen.

Question 11

What specimen is unacceptable for mycobacteria

Answer 11

Feces

Question 12

For specimens from aspirated wound cultures…

Answer 12

swabs NOT acceptable

Question 13

What is the method for collecting specimens for blood cultures?

Answer 13

lysis centrifugation or inoculating directly to broth media

Question 14

For sterile body fluids…

Answer 14

STERILITY MUST BE STRICTLY MAINTAINED! For CSF, large volumes are needed. (tissues must stay sterile too!)

Question 15

What is added to tissue specimans?

Answer 15

saline–helps avoid dehydration. You grind up the tissue to help release the organisms

Question 16

What is a fluorochrome stain? (auramine O)

Answer 16

primary stain: fluorescent dyes

counter stain: potassium permanganate. It will appear gold against a black background.

Question 17

What are the +/- of using a flurochrome stain?

Answer 17

+: more sensitive than carbolfuchsin stains, examine on lower magnification.

-: rapid growing mycobacteria do not stain, less specific

Question 18

What are Carbolfuschins tains?

Answer 18

primary stain: carbolfuschin
counter stain: methylene blue
AFB will appear red and backround will be blue

Question 19

What are the +/- of using a Carbolfuschin stain?

Answer 19

+: more specific than fluroescent stain, stains all mycobacteria

-: longer exam time, less sensitive

Question 20

How do you interpret smears?

Answer 20

observe over 300 oil immersion fields. Look for mycobacteria, other organisms will stain partially acid fast.

Question 21

Microscopic eval: correlation with culture results

Answer 21

Extensive disease: good correlation

minimal/less advanced: less correlation

Question 22

What are the causative agents of tuberculosis?

Answer 22

myobacterium tuberculosis (humans)
myobacterium bovis (cattle)
mybacterium africanum 

they have an increase rate of infections, and multidrug resistance

Question 23

What is the most common cause of tuberculosis?

Answer 23

myobacterium tuberculosis, it is primarily a lung disease.

Question 24

What is a myobacterium tuberculosis active disease dependent on?

Answer 24

cellular immunity, amount of exposure, virulence of strain

Question 25

How does infection of myobacterium tuberculosis take place?

Answer 25

1. inhalation of organisms 2. reach aveoli 3. immune response is initiated (organism can be walled-off)

Question 26

myobacterium tuberculosis: Active vs Inactive

Answer 26

Inactive disease: - organism is walled off - patient is symptom free and not infectious - screening tests will be positive (once a test is pos, it will always be pos) Active: - organism multiples - patient is symptomatic AND infectious

Question 27

What are the symptoms of myobacterium tuberculosis: Active?

Answer 27

fever, SOB, night sweats, chills, fatigue, anorexia and weight loss.

Question 28

Where are the most common places for a disseminated disease to go to?

Answer 28

spleen, liver, bone marrow, kidney

Question 29

Three basic strategies are critical to prevention and control of TB:

Answer 29

1. ID and completely treat person with active TB 2. Finding and evaluating persons who have had contact with TB patients, possibly treatment. (contact investigations) 3. screening populations at high risk for TB to locate persons infected with TB and giving therapy.

Question 30

What are myobacterium tuberculosis screen tests?

Answer 30

PPD or TST: in vivo, delayed hypersensitivity | QFT-G: in vitro, performed on blood collected from the patient. its cell-mediated response with blood.

Question 31

How many patient visits does QFT-G vs TST take?

Answer 31

1 vs 2

Question 32

What happens if someone recently screen positive for myobacterium tuberculosis?

Answer 32

1.Perform CXR for active disease (if no active, then still treat. 2. Active TB suspected sputum: smear and culture X3 Nucleic Acid Probes performed on: culture growth, direct respiratory specimens

Question 33

TB-> What is the lab diagnosis?

Answer 33

Acid-fast stain, nucleic acid probes, sputum culture--> susceptiblity testing. PCP is verbally informed at any stage of the process when smear/culture is positive.

Question 34

How should a patient be isolated?

Answer 34

patient isolated in a negative-pressure room until... - M. tuberculosis is ruled out - 2 weeks of successful treatment - smear negative specimens on 3 successive days - determined to be non-infectious by appropriate individual

Question 35

Active TB drug therapy:

Answer 35

Isoniazid, Rifampin, Ethambuton, Prazinamide. Length of therapy is around 6-9 months.

Question 36

Multidrug resistant TB:

Answer 36

resistant to at least 2 drugs including INH and RIF

Question 37

Extensively resistant TB:

Answer 37

- resistant to at least 2 drugs including INH and RIF - a FQ - at least one of 1 of the 3 second-line - Ethambutol - Pyrazinamide

Question 38

What do you give for latent TB?

Answer 38

Isoniazid (and B6--but thats from med!!)