Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 2 Clinical Pathology > Mycobacterial diseases > Flashcards

Mycobacterial diseases Flashcards

1
Q

What shape are mycobacteria?

A

Slender bacillus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

In which 2 ways are mycobacteria different to other bacterial genera?

A

1) Unusual waxy cell wall - high lipid content

2) Slow growing - different media requirements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Mycobacteria are ‘acid fast bacilli’ which have poor take up of gram’s stains, which 2 stains are used to identify mycobacteria?

A

1) Ziehl neelsen

2) Phenol auramine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What kind of pathogens are mycobacteria?

A

Intracellular pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What kind of infections do mycobacteria tend to cause?

A

Chronic infections often with a latent phase of infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How are mycobacteria treated compared to other bacterial genera?

A

Different antimicrobial agents
Much longer courses of therapy
Combination of agents to prevent resistance emergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What mycobacteria causes TB?

A

Mycobacteria tuberculosis complex:
M. tuberculosis
M. bovis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What mycobacteria causes leprosy?

A

M. leprae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Name 3 atypical mycobacteria, which is associated with HIV and which is associated with fish tank granuloma?

A

1) M. avium complex - associated with HIV
2) M. kansasii
3) M. marinum - fish tank granuloma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What fraction of the world population is affected by TB, how many deaths does it cause each year and what other condition is it associated with?

A

1/3 of the world population infected
2 million deaths per years
Co-infection with HIV - sub-Saharan Africa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

For what 4 reasons has TB infection become more common in the ‘developed world’?

A

1) HIV infection
2) Breakdown of control programmes
3) Increased migration from endemic areas
4) Increased travel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What percentage of TB infected people in the UK were born abroad and 60% are from what age group?

A

70% born abroad

60% are young adults aged 15-44

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is TB spread?

A

Person to person - inhalation of infected respiratory droplets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the rough course of TB, at which stages are patients symptomatic?

A

1)Primary infection (usually pulmonary disease)
- Some patients will be symptomatic (flu like) and some completely asymptomatic
2) Latent infection period
3) Reactivation of TB (does not occur in all people some people it will remain latent forever)
4) Dissemination (doesn’t disseminate to affect other organs in all people who get reactivation)
NB. Primary infection may disseminate completely skipping the latent phase (this can happen in children)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the most common site of primary TB infection?

A

Periphery of lung midzone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens once TB is inhaled?

A

1) Inhaled bacilli is phagocytosed by macrophages and carried to the hilar lymph nodes - ghon focus (primary lesion caused by TB)
2) Get intracellular multiplication
3) In some patients can get dissemination at this point via the lymph system/ blood stream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the bodies response to TB infection?

A

Tubercle formation (granuloma formation) via a cell mediated response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the structure of the tubercles formed in TB, what happens to them and what is their function?

A

1) Central area of epitheloid cells and giant cells
2) Have a surrounding lymphocytic cell infiltration
3) Central area of necrosis
Eventually get fibrosis and calcification of the lesions
The tubercles aim to contain the infection
The bacilli slowly die but may remain viable for 20 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

In what 2 ways could a primary TB infection be identified in a patient with some clinical symptoms?

A

1) CXR

2) Tuberculin skin test conversion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

In which 6 groups of people is reactivation of TB infection most likely to occur?

A

1) Lowered immunity
2) In western countries, males over 50
3) Malnutrition
4) Alcoholism
5) Debilitating illness
6) HIV infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

People taking what drug are more likely to get a reactivation of TB and why?

A

Anti TNFa blockade

Role of TNFa is to maintain the granuloma thus harder to maintain in the presence of this drug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Patients with what 3 conditions are more likely to get reactivation of TB?

A

1) Silicosis
2) Chronic renal failure
3) Gastrectomy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where does the pathogen tend to reside in reactivation of TB and why?

A

Lung apices: its an anaerobe and this is where the oxygen tension is highest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens to the tubercles in reactivation of TB?

A

Tubercles coalesce and get caseous necrosis

Can also get cavitation - leading to a higher organism load so greater risk of transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the 5 main symptoms in reactivation of TB?

A

1) Chronic productive cough
2) Haemoptysis
3) Weight loss
4) Fever
5) Night sweats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the name for disseminated TB?

A

Miliary TB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What 2 groups does disseminated TB tend to occur in (whether that be following primary infection or reactivation)?

A

1) Very young/very old

2) Immunocompromised

28
Q

How does dissemination occur in secondary disease?

A

Erosion of necrotic tubercle into blood vessel

29
Q

What are the 8 common extra-pulmonary sights in military TB?

A

1) Pleura
2) Lymph nodes
3) Kidneys
4) Epididymis
5) Bone
6) Intestines
7) Brain/meninges (meningitis)
8) Pericardium

30
Q

What are the 5 main signs of TB meningitis?

A

1) Often insidious onset
2) Unidentified fever
3) Personality change
4) Focal neurological defect (basilar inflammation)
5) Mild headache/ meningism
(May lack constitutional quartet - fever, anorexia, night sweats, weight loss)

31
Q

Other than microbiology what 4 other procedures lead to a diagnosis of TB?

A

1) CXR
2) Histology
3) Skin testing
4) Blood test: interfere gamma release assay: IGRA

32
Q

For what 3 reasons is microbiology necessary in a diagnosis of TB and what kind of sample is needed?

A

1) Confirmation of diagnosis
2) Drug sensitivities
3) Molecular typing profile:’MIRUs’
Fresh sample - normally of sputum, 3 early morning specimens taken >8 hours apart

33
Q

How is a sample for TB used?

A

Direct microscopy for AFBs (acid fast bacilli)

>5000 organisms per ml of sputum is considered smear positive

34
Q

In which 2 ways can TB be cultured from a sample, how long does each take?

A

1) Lowenstein-Jensen solid media - 3-4 weeks

2) Broth culture: automated - usually

35
Q

What 4 processes are carried out if a sputum sample is found to be AFB positive?

A

1) Referred to regional reference laboratory
2) Species identification
3) Sensitivites: within 2 weeks
4) Strain typing

36
Q

In children a sputum sample can be hard to obtain, what 3 procedures may be used to obtain one?

A

1) Induced sputa - nebulised saline
2) Bronchial aspirates
3) Gastric aspirates

37
Q

In suspected renal TB what sample would be needed?

A

Early morning urines x3

38
Q

How would CSF be analysed in suspected TB meningitis?

A

Cell count, protein, glucose, microscopy/culture

NB need an adequate volume - >6mls

39
Q

Other than culturing what other method can be used to identify TB, what are the 3 disadvantages and 1 advantage?

A

Nucleic acid amplification by PCR
Advantage: rapid
Disadvantage: less sensitive than culture, expensive and not 100% specific (false positives)

40
Q

The XPERT MTB/RIF test is a different method of testing for TB how? and where is it often used?

A

Direct to sputum test which is clinic based with a result in 2 hours
Used in developing world where there is less access to cultures

41
Q

What are the 2 main difficulties with TB treatment?

A

Lengthy and involves combined tablets - can mean poor adherence

42
Q

What is the standard treatment for pulmonary TB?

A

2 months: Isoniazid, rifampicin, pyrazinamide, ethambutol

4 months: isoniazid, rifampicin

43
Q

Why is combined therapy needed to treat TB?

A

Less chance of resistance, low chance of obtaining combined mutations

44
Q

How is TB in other sights (except meningeal) treated?

A

Standard 6 month regime used to treat TB

45
Q

How long does treatment for TB meningitis take?

A

12 months

46
Q

Other than length how does treatment for TB meningitis and pericarditis differ from treatment at other sights?

A

Initial treatment also with corticosteroids

47
Q

What are the 4 second line agents for drug resistant TB?

A

1) Amikacin
2) Ethionamide/prothionamide
3) Cycloserine
4) Fluoroquinolones: ciprofloxacin, moxifloxacin

48
Q

What are the 3 new drugs being used to treat TB?

A

1) Bedaloquine
2) Delamanid
3) Pa-824

49
Q

Why is it thought that shorter regimes for standard Rx would be good?

A

As it would improve completion rates

50
Q

What 5 things are put in place to try and control TB (ie. identify people with latent infection and prevent transmission)?

A

1) It is a notifiable disease
2) Contact tracing
3) Tuberculin skin test
4) Blood test: interferon gamma release assay
5) CXR

51
Q

How does the mantoux test work?

A

Inject purified protein derivative (MTB extract) subcutaneously
Read at 48-72 hours observing skin reaction

52
Q

What do interferon gamma release assays measure?

A

Specific T cells: IFN gamma production

TB specific Ag (ESAT6, CFP10) - don’t cross react with M bovis

53
Q

When can interferon gamma release assays be used to identify TB?

A

Both in latent TB (in new entrants, contacts, immunosuppressed people) and active disease

54
Q

What does the BCG vaccine contains?

A

Attenuated stain of mycobacteria bovis

55
Q

When is the BCG vaccine given in the UK?

A

Neonatal or occupational exposure risk

56
Q

What chemoprophylaxis can be used for TB?

A

1) 3 months of rifampicin/isoniazid or 6 months isoniazid

57
Q

Can the atypical mycobacteria ‘non tuberculous mycobacteria’ be transmitted from person to person?

A

No its an environmental organism

58
Q

What mycobacterium tends to cause disseminated disease in HIV infected people?

A

Mycobacterium avium complex

59
Q

What kind of disease does mycobacterium avium complex cause in non HIV infected adults and what in young children?

A

Non HIV infected: pulmonary TB like disease

Young children: cervical lymphadenitis

60
Q

How is mycobacterium avium diagnosed?

A

In a similar way, cultured, they are acid fast bacilli so can be stained in a similar way

61
Q

What is the treatment for mycobacterium avium complex?

A

Combined treatment, like TB is prolonged

Use a macrolide - clarithromycin or azithromycin

62
Q

What are the 2 possible immune responses to mycobacterium leprosy infection?

A

1) Tuberculoid - macules/plaques, can cluster around nerves (ulnar and common peroneal) - not severe
2) Lepromatous - subcutaneous tissue accumulation (disfiguring lesions), ear lobes , face - leonine facies - severe

63
Q

What are the 3 drugs used to treat leprosy?

A

1) Dapsone
2) Rifampicin
3) Clofazimine

64
Q

How does mycobacterium leprosy have to be identified, why?

A

Genomic analysis as non culturable in vitro

65
Q

What is the specific microbiology request for TB?

A

AFBs

Year 2 Clinical Pathology (64 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions