Mycobacterium L13 Flashcards
(84 cards)
1
Q
what bacteria are mycobacteria
A
gram-positive
2
Q
is mycobacteria motile
A
non-motile
3
Q
is mycobacteria sporing
A
non-sporing
4
Q
does mycobacteria have a capsule
A
non-capsulate
5
Q
what is mycobacteria respiration
A
aerobic
6
Q
what shape are mycobacteria
A
rods
7
Q
how many mycobacteria are there
A
more than 85
8
Q
where are mycobacteria found
A
mostly found in soil and fresh water
9
Q
what are mycobacteria like in liquid culture
A
often appear to grow as filaments due to the mycolic acid in cell wall
10
Q
when are mycobacteria visible
A
upon disturbance rods or cocci are visible
11
Q
what are the environmental stresses that mycobacteria are resistant to
A
- disinfectants
- host defences
- antibiotics
12
Q
what is on top of the peptidoglycan layer
A
mycolic acid layer
13
Q
why are mycobacteria resistant to staining
A
mycolic acid layer
14
Q
why are mycobacteria difficult to see
A
resistant to stain
15
Q
what are mycobacterium spp. characterised by
A
thick, lipid-rich cell walls that are resistant to decolorisation after staining with carbol fuschin (Ziehl-Nielsen Acid Fast)
16
Q
what test is used to characterise mycobacterium
A
Ziehl-Nielsen Acid Fast
17
Q
what does the mycolic acid bind to
A
carboxylic acid group of mycolic acid binds to red fuschin dye and isn’t removed by acid-alcohol wash
18
Q
can mycolic acid be removed
A
binds irreversibly to mycolic acid
19
Q
what is the counterstain for mycolic acid
A
methylene blue counter stain
20
Q
what can stained sputum samples show
A
examined by microscopy and diagnosis may be confirmed in an hour
21
Q
what dye is seen, using what
A
phenol auramine fluorescent dye visualised with a UV microscope
22
Q
what does mycobacterium tuberculosis
A
main cause of primary and post-primary human tuberculosis
23
Q
what does mycobacterium leprae cause
A
leprosy
24
Q
what does mycobacterium leprae infect
A
only humans
and 7-banded armadillo
25
what is mycobacterium tuberculosis complex
```
four closely related species:
M. tuberculosis
M. bovis
M. microti
M. africanum
```
26
what is mycobacterium tuberculosis
a chronic granulomatous disease
27
what does mycobacterium tuberculosis cause
Granuloma-accumulation of macrophage
28
what is mycobacterium tuberculosis cultured on
3 to 8 weeks to culture on Lowenstein-Jensen agar slopes
29
how long does it take to detect mycobacterium tuberculosis
10 days to detect presence using 14CO2 production
30
where is 14C from in mycobacterium detection
palmitate in broth
31
how long does PCR detection usually take
<24hrs
32
how is mycobacteria usually spread
inhalation of infected respiratory droplets
33
how can mycobacterium survive
in alveoli, phagocytosed by macrophage
| bacteria prevent lysosomes fusing with phagosomes and therefore survive
34
how does mycobacterium spread from alveoli
Other cells such as those lining the alveoli become infected with Mycobacterium
35
what is primary tuberculosis
mycobacterium infected in alveoli
36
what will mycobacterium cause in body
Inside body will trigger an immune response this can be done through phagocytosis
37
what does mycobacterium do during replication
kill the host cells during replication, triggering recruitment of more macrophage
38
what does mycobacterium do when emerging from dead macrophage
re-infect new macrophage
39
how long does primary tuberculosis cycle last
cycle may only last a short while and is normally asymptomatic or presents as mild fever
40
what happens when macrophage present mycobacterium to lymphocytes
- more lymphokines are released
- more macrophage are therefore activated (macrophage flood to infection site)
- inflammation begins (will trigger more immune response)
- macrophage surround infection site forming a tubercle
41
what causes inflammation in primary tuberculosis
a lot of macrophage infected, get a ball in the centre and this causes inflammation
42
what are the mycobacterium surrounded by in primary tuberculosis
cells of the tubercle containing the Mycobacterium are surrounded by collagen, wrap it up to keep out of the way
characteristic about TB
43
how long does the tubercle last
in some cases, over time the interior of tubercle dies
44
what causes the tubercle to die
incomplete proteolytic digestion of tissue results caseous necrosis
45
what causes a tuberculous cavity
centre of the tubercle may liquefy, rupture and fill with air tubercle rupture, contents ooze out, tissue damage and hole in the lung tissue where the tubercle was
46
what is the immune system like in the Ghon complex
Often the immune system and bacteria exist in equilibrium at this point
47
what are the possibilities in the Ghon complex
immune system may clear the bacteria
| Mycobacterium may remain dormant but are capable of infecting other tissues
48
what happens if bacteria are cleared in Ghon complex
calcium will be deposited around the tubercle over time resulting in the formation of a Ghon complex
49
what is Ghon complex a good marker for
TB when Xray done, dark spots of calcium
50
what is the effect of primary tuberculosis - Ghon complex
Lung function can be significantly reduced
51
when does another infection cycle begin
if the bacteria succeed over the immune system the tubercle is ruptured and the infection cycle begins once more
52
post primary tuberculosis it is possible for infected macrophage to migrate through the blood and lymph to key organs such as:
- spleen
- kidney
- bone marrow
- spinal cord
- brain
53
what happens to the tissues that become infected
slowly degenerate
54
why are many common antibiotics ineffective
because mycobacterium grow so slowly the drugs are cleared before affecting the bacterial load
55
what are the drugs of choice for mycobacterium tuberculosis treatment
Isoniazid for 6 months
Rifampin for 6 months
Pyrazinamide for first 2 months
Ethambutol for first 2 months
56
what does isoniazid do
micolic acid synthesis inhibition
57
what does rifampin do
polymerase inhibiton
58
what does pyrazinamide do
unclear
59
what does ethambutol do
micolic acid synthesis inhibition
60
what is MDR
multi drug resistance
61
what is RR-TB
rifampicin-resistant TB
62
what is MDR-TB
Multi-drug resistant TB, defined as resistance to rifampicin and isoniazid
63
what is BCG
bacille Calmette-Guérin
64
how is mycobacterium tuberculosis preventing infection
immunisation with BCG live attenuated vaccine
65
what does BCG vaccination do
does not prevent infection but limits proliferation of the organisms
66
what are individuals that have had close contact with a case of tuberculosis
treated prophylactically with isoniazid
67
what is a challenge for TB control programs
HIV and AIDS
| many AIDS-related deaths are due to TB
68
what are the two leprosy forms
progressive or non progressive
69
what is TT
Tuberculoid leprosy (TT) strong immune response, small numbers of bacilli
70
what is LL
Lepromatous leprosy (LL) poor immune response but large numbers of bacilli
71
what is tuberculoid leprosy characterised by
- blotchy red regions on the skin
| - anaesthetic regions on the face, body and extremities
72
what type of leprosy is tuberculoid leprosy
non progressive
73
what is tuberculoid leprosy
localised tissue damage, but it non progressive, immune system will kill it
74
how is tuberculoid leprosy equivalent to post-primary tuberculosis
vigorous cell mediated immune response leads to phagocytic destruction of bacteria and sometimes an exaggerated allergic responses
75
what leads to lepromatous leprosy
Large numbers of bacteria accumulate in the infected areas
76
what does lepromatous leprosy cause
- palpable thickening of peripheral nerves, as bacteria multiply in nerve sheaths
- progressive destruction of nasomaxillary facial structures
- nasal mucosa is usually loaded with bacteria
77
what does palpable thickening of peripheral nerves cause
thickening of nostrils, ears and cheeks, loss of eyebrows
78
what is the problem with dapsone
resistance
79
what is used to overcome dapsone resistance
used in conjunction with
- rifampicin
- clofazimine (binds to guanine in DNA)
- normally given for two years, often longer, sometimes for life
80
what can destruction of organisms cause
a severe inflammatory response which is sometimes fatal
81
what can cure leprosy
effective multi-drug treatment for all types of leprosy
82
where are more mycobacterium cases emerging
emerging mycobacterium infection of HIV patients
83
what mycobacteria can infect skin
marinum
tuberculosis
ulcerans
84
what skin infections can be caused
fish tank granuloma
| buruli granuloma
