Myobacteria

Question 1

describe mycobacteria

Answer 1

• unicellular and branched rods
• G+ve
• complex cell wall (cont sugars, proteins and LOT OF LIPID)

Question 2

how can mycobacteria be stained and identified?

Answer 2

Acid fast staining-Ziehl Neelson stain:
-stain carbol fuchsin
-destain acid alcohol
-counterstain methylene blue 
mycobacteria= RED (everything else=blue)

Question 3

what is found in cell walls of Mycobacteria?

Answer 3

mycolic acid (protective, waxy coat) outside peptidoglycan layer

Question 4

what are the two groups of Mycobacteria?

which group is pathogenic?

Answer 4

1) fast growers (1-2 days on plates)

2) slow growers (several weeks)- PATHOGENIC group

Question 5

M.bovis causes?

Answer 5

bovine TB

Question 6

M.avium is what type of pathogen?

where is it found?

Answer 6

• opportunistic pathogen

- ub in env

Question 7

M.paratuberculosis affects what?

Answer 7

ruminants

Question 8

M.ulcerans affects who?

causes what?

Answer 8

humans

causes ulcers

Question 9

M.leprae affects who?

Answer 9

humans

Question 10

M.marinum affects who?

Answer 10

fish, frogs and humans

Question 11

significance of TB

Answer 11

• global emergency
• 35000 deaths a week
• high incidence in HIV individuals

Question 12

outcomes after TB exposure

Answer 12

1) EXPOSURE, NO INF
- TB cleared before it gets past INNATE immune defences
2) EXPOSURE, INF, NEVER DISEASE
- if immunocompetent, 90% DON’T get disease
3) EXPOSURE, INF, DISEASE, +/- DEATH
- asymptomatic latent period

Question 13

how do you test for TB?

Answer 13

Heaf/Mantoux test- antigen is placed on skin, punch is used to punch it into skin
may form INFLAMMATORY response

Question 14

how does TB exit the host?

Answer 14

by causing TB infection/disease

Question 15

describe the pathogenesis of TB

Answer 15

• aerosol travels to alveoli of lungs
• M.tuberculosis engulfed by alveolar macrophages
• if activated due to an acquired immune response host clears bacteria or contains infection
• if unactivated (child or immunocompromised), bac survive and replicate in macrophages—> attracts more PMN & T cells—> damage tissue, form granulomatous tubercle

Question 16

what can be used to diagnose TB?

Answer 16

1) X ray
2) microscopy of sputum looking for acid fast rods
3) culture sputum samples(media con egg or oleic acid or albumin)
4) PCR

Question 17

what happens when the granuloma (tubercle) grows?

Answer 17

it eventually breaks into the airway of lung, is coughed up and O bacteria are released-
TRANSMISSION

Question 18

how is the granuloma formation capable of stopping TB progressing?

Answer 18

may contain the infection and stop TB development BUT can also aid transmission (granuloma coughed up—>transmitted)

Question 19

what HOST FACTORS determine how someone responds to TB infection?

Answer 19

• HIV status
• immunodeficiency
• genetic immunodeficiency
• substance abuse
• malnutrition

Question 20

what BACTERIAL FACTORS determine how someone responds to TB infection?

Answer 20

• small differences in STRAIN VIRULENCE

Question 21

TB symptoms?

Answer 21

• fever
• weight loss
• weakness
• PERSISTENT COUGH (due to inflammatory response)

Question 22

where can TB spread (15% of cases)?

Answer 22

CNS, lymphatic system, genitourinary systems, bones etc

Question 23

TB prevention?

Answer 23

BCG Vaccine

Question 24

TB treatment?

Answer 24

MULTI DRUG AB treatment (~6 months)

4 main ABs are 1st line

Question 25

how effective is the BGC vaccine?

Answer 25

efficacy varies by geographic location and population - works well in children - protects against leprosy

Question 26

describe AB resistance for TB

Answer 26

resistance = inc common | some strains are resistant to ALL 4 FRONTLINE DRUGS called EXTENSIVELY DRUG RESISTANT TB

Question 27

what causes resistance in TB?

Answer 27

- failure to take all medications | - failure to be provided w/ steady supply of medication

Question 28

what causes leprosy?

Answer 28

M. leprae

Question 29

how can we grow M.leprae?

Answer 29

cannot be cultivatable, but can be grwon in armadillos, squirrel ears & mouse footpads

Question 30

what type of parasite is it?

Answer 30

intracellular, grows in macrophages and Schwann cells (---> nerve damage)

Question 31

how is M.leprae transmitted?

Answer 31

- little known - most who come into contact are NOT infected - those w/ leprosy have high counts in nasal discharge

Question 32

what % of infected individuals get the leprosy?

Answer 32

5%

Question 33

what are the 2 clinical manifestations of leprosy?

Answer 33

1) TUBERCULOID -few bacilli in tissue, mild disease, few skin lesions Host response: strong immune response, low antibody, tuberculoid GRANULOMA forms to CONTAIN the infection 2) LEPROMATOUS - severe, huge nos of bacilli in tissue, multiple lesions, skin nodules packed with bacteria. Nerve damage, loss of extremities, DEATH Host response: poor immune response, high antibody, FOAM CELL GRANULOMA

Question 34

how is leprosy prevented?

Answer 34

BCG vaccine

Question 35

how is leprosy treated?

Answer 35

ABs (Dapsone), treatment may be for life

Question 36

describe resistance to M.leprae

Answer 36

increasing O need multi drug therapy