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Microorganisms + Disease > Mycobacterium L13 > Flashcards

Mycobacterium L13 Flashcards

1
Q

what bacteria are mycobacteria

A

gram-positive

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2
Q

is mycobacteria motile

A

non-motile

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3
Q

is mycobacteria sporing

A

non-sporing

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4
Q

does mycobacteria have a capsule

A

non-capsulate

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5
Q

what is mycobacteria respiration

A

aerobic

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6
Q

what shape are mycobacteria

A

rods

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7
Q

how many mycobacteria are there

A

more than 85

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8
Q

where are mycobacteria found

A

mostly found in soil and fresh water

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9
Q

what are mycobacteria like in liquid culture

A

often appear to grow as filaments due to the mycolic acid in cell wall

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10
Q

when are mycobacteria visible

A

upon disturbance rods or cocci are visible

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11
Q

what are the environmental stresses that mycobacteria are resistant to

A
  • disinfectants
  • host defences
  • antibiotics
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12
Q

what is on top of the peptidoglycan layer

A

mycolic acid layer

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13
Q

why are mycobacteria resistant to staining

A

mycolic acid layer

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14
Q

why are mycobacteria difficult to see

A

resistant to stain

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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)

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16
Q

what test is used to characterise mycobacterium

A

Ziehl-Nielsen Acid Fast

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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

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18
Q

can mycolic acid be removed

A

binds irreversibly to mycolic acid

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19
Q

what is the counterstain for mycolic acid

A

methylene blue counter stain

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20
Q

what can stained sputum samples show

A

examined by microscopy and diagnosis may be confirmed in an hour

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21
Q

what dye is seen, using what

A

phenol auramine fluorescent dye visualised with a UV microscope

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22
Q

what does mycobacterium tuberculosis

A

main cause of primary and post-primary human tuberculosis

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23
Q

what does mycobacterium leprae cause

A

leprosy

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24
Q

what does mycobacterium leprae infect

A

only humans

and 7-banded armadillo

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25
Q

what is mycobacterium tuberculosis complex

A 
four closely related species:
M. tuberculosis
M. bovis
M. microti
M. africanum
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26
Q

what is mycobacterium tuberculosis

A

a chronic granulomatous disease

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27
Q

what does mycobacterium tuberculosis cause

A

Granuloma-accumulation of macrophage

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28
Q

what is mycobacterium tuberculosis cultured on

A

3 to 8 weeks to culture on Lowenstein-Jensen agar slopes

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29
Q

how long does it take to detect mycobacterium tuberculosis

A

10 days to detect presence using 14CO2 production

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30
Q

where is 14C from in mycobacterium detection

A

palmitate in broth

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31
Q

how long does PCR detection usually take

A

<24hrs

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32
Q

how is mycobacteria usually spread

A

inhalation of infected respiratory droplets

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33
Q

how can mycobacterium survive

A

in alveoli, phagocytosed by macrophage

bacteria prevent lysosomes fusing with phagosomes and therefore survive

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34
Q

how does mycobacterium spread from alveoli

A

Other cells such as those lining the alveoli become infected with Mycobacterium

35
Q

what is primary tuberculosis

A

mycobacterium infected in alveoli

36
Q

what will mycobacterium cause in body

A

Inside body will trigger an immune response this can be done through phagocytosis

37
Q

what does mycobacterium do during replication

A

kill the host cells during replication, triggering recruitment of more macrophage

38
Q

what does mycobacterium do when emerging from dead macrophage

A

re-infect new macrophage

39
Q

how long does primary tuberculosis cycle last

A

cycle may only last a short while and is normally asymptomatic or presents as mild fever

40
Q

what happens when macrophage present mycobacterium to lymphocytes

A
  • 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
Q

what causes inflammation in primary tuberculosis

A

a lot of macrophage infected, get a ball in the centre and this causes inflammation

42
Q

what are the mycobacterium surrounded by in primary tuberculosis

A

cells of the tubercle containing the Mycobacterium are surrounded by collagen, wrap it up to keep out of the way
characteristic about TB

43
Q

how long does the tubercle last

A

in some cases, over time the interior of tubercle dies

44
Q

what causes the tubercle to die

A

incomplete proteolytic digestion of tissue results caseous necrosis

45
Q

what causes a tuberculous cavity

A

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
Q

what is the immune system like in the Ghon complex

A

Often the immune system and bacteria exist in equilibrium at this point

47
Q

what are the possibilities in the Ghon complex

A

immune system may clear the bacteria

Mycobacterium may remain dormant but are capable of infecting other tissues

48
Q

what happens if bacteria are cleared in Ghon complex

A

calcium will be deposited around the tubercle over time resulting in the formation of a Ghon complex

49
Q

what is Ghon complex a good marker for

A

TB when Xray done, dark spots of calcium

50
Q

what is the effect of primary tuberculosis - Ghon complex

A

Lung function can be significantly reduced

51
Q

when does another infection cycle begin

A

if the bacteria succeed over the immune system the tubercle is ruptured and the infection cycle begins once more

52
Q

post primary tuberculosis it is possible for infected macrophage to migrate through the blood and lymph to key organs such as:

A
  • spleen
  • kidney
  • bone marrow
  • spinal cord
  • brain
53
Q

what happens to the tissues that become infected

A

slowly degenerate

54
Q

why are many common antibiotics ineffective

A

because mycobacterium grow so slowly the drugs are cleared before affecting the bacterial load

55
Q

what are the drugs of choice for mycobacterium tuberculosis treatment

A

Isoniazid for 6 months
Rifampin for 6 months
Pyrazinamide for first 2 months
Ethambutol for first 2 months

56
Q

what does isoniazid do

A

micolic acid synthesis inhibition

57
Q

what does rifampin do

A

polymerase inhibiton

58
Q

what does pyrazinamide do

A

unclear

59
Q

what does ethambutol do

A

micolic acid synthesis inhibition

60
Q

what is MDR

A

multi drug resistance

61
Q

what is RR-TB

A

rifampicin-resistant TB

62
Q

what is MDR-TB

A

Multi-drug resistant TB, defined as resistance to rifampicin and isoniazid

63
Q

what is BCG

A

bacille Calmette-Guérin

64
Q

how is mycobacterium tuberculosis preventing infection

A

immunisation with BCG live attenuated vaccine

65
Q

what does BCG vaccination do

A

does not prevent infection but limits proliferation of the organisms

66
Q

what are individuals that have had close contact with a case of tuberculosis

A

treated prophylactically with isoniazid

67
Q

what is a challenge for TB control programs

A

HIV and AIDS

many AIDS-related deaths are due to TB

68
Q

what are the two leprosy forms

A

progressive or non progressive

69
Q

what is TT

A

Tuberculoid leprosy (TT) strong immune response, small numbers of bacilli

70
Q

what is LL

A

Lepromatous leprosy (LL) poor immune response but large numbers of bacilli

71
Q

what is tuberculoid leprosy characterised by

A
  • blotchy red regions on the skin

- anaesthetic regions on the face, body and extremities

72
Q

what type of leprosy is tuberculoid leprosy

A

non progressive

73
Q

what is tuberculoid leprosy

A

localised tissue damage, but it non progressive, immune system will kill it

74
Q

how is tuberculoid leprosy equivalent to post-primary tuberculosis

A

vigorous cell mediated immune response leads to phagocytic destruction of bacteria and sometimes an exaggerated allergic responses

75
Q

what leads to lepromatous leprosy

A

Large numbers of bacteria accumulate in the infected areas

76
Q

what does lepromatous leprosy cause

A
  • 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
Q

what does palpable thickening of peripheral nerves cause

A

thickening of nostrils, ears and cheeks, loss of eyebrows

78
Q

what is the problem with dapsone

A

resistance

79
Q

what is used to overcome dapsone resistance

A

used in conjunction with

  • rifampicin
  • clofazimine (binds to guanine in DNA)
  • normally given for two years, often longer, sometimes for life
80
Q

what can destruction of organisms cause

A

a severe inflammatory response which is sometimes fatal

81
Q

what can cure leprosy

A

effective multi-drug treatment for all types of leprosy

82
Q

where are more mycobacterium cases emerging

A

emerging mycobacterium infection of HIV patients

83
Q

what mycobacteria can infect skin

A

marinum
tuberculosis
ulcerans

84
Q

what skin infections can be caused

A

fish tank granuloma

buruli granuloma

Microorganisms + Disease (16 decks)

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