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Path - Microbiology > Mycobacterial disease : TB > Flashcards

Mycobacterial disease : TB Flashcards

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1
Q

name 2 mycobacterium in; Mycobacterium Tuberculosis Complex

A

○ Mycobacterium tuberculosis

○ Mycobacterium bovis (BCG)

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2
Q

how are non-tuberculous mb different from tuberculous ones?

A

also known as environmental mycobacteria

do not cause tuberculosis or leprosy

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3
Q

M. abseccuss is a mycobacterium that has which growth speed?

A

fast

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4
Q

why can’t TB be gram stained?

A

large amounts of lipid substances within their cell walls called mycolic acids.

These acids resist staining by ordinary methods such as a Gram stain.

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5
Q

2 ways to detect tb in sample?

caveats?

A

Auramine - greater false positives

Zhiel-Neelson stain - less sensitive

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6
Q

auramine and ZN stain are examples of which tests?

A

acid alcohol test

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7
Q

Non-tuberculous mycobacteria are found where?

A

water and soil

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8
Q

route of transmission of NTM?

A

NO person to person

rare animal to people

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9
Q

who are high risk of NTM?

A

Immunocompromised:
HIV
transplant
Malignancy

lung disease - i.e. a1 antritypsin
post menopausal + Underlying lung disease

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10
Q

which NTM causes:

Skin lesions e.g. Bairnsdale ulcer, Buruli ulcer
Chronic progressive painless ulcer

A

M. ulcerans

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11
Q

which NTM causes:

Swimming pool granuloma

what is this?

A

M. Marinum

remember Marine

localized nodular skin inflammation (small reddish raised areas of skin)

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12
Q

how does mycobacterium avium present in

a. immunocompetent
b. immunosuppressed

A

immunocompetent;
lung disease ; pre-existing cavities or bronchiectasis

immunosuppressed:
disseminated disease

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13
Q

list 3 examples of slow growing tb

A

M Tuberculosis
M Bovis

M Avium

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14
Q

M. abscessus, M. chelonae, M. fortuitum are rapid growing NTM.

they are usually found where?

A

Tattoos

In hospital settings;
Vascular catheters & other devices

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15
Q

name the 3 microbiological diagnostic criteria for TB?

A

Positive culture >1 sputum samples

OR +ve BAL - bronchoaveolar lavage
OR +ve biopsy with granulomata

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16
Q

Name some risk factors for NTM?

A

○ Age

○ Underlying lung disease

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17
Q

how to treat rapid growing NTM?

A

Based on susceptibility testing, usually macrolide-based

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18
Q

name 2 forms of Mycobacterium leprae?

difference?

A

○ Paucibacillary tuberculoid
§ Few skin lesions
§ Robust T cell response

○ Multibacillary lepromatous
§ Abundance of bacilli
§ Multiple lesions - v. deforming
§ Poor T cell response

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19
Q

which is the 2nd most common cause of death by infectious agent ?

which is first?

A

1st - HIV

2nd - TB

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20
Q

TB is the Most common opportunistic infection in which disease?

A

HIV

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21
Q

3 possibilities post contact with TB infected person?

A

After contact with a person with TB, you could become
infected,

become latently infected or

not become infected at all

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22
Q

which is 2nd most common Mycobacterial infection after MTB?

A

After m tb, m bovis most common infection in humans, others are rare

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23
Q

MTB complex consists of how many closely related species?

A

7

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24
Q

what is the Infectious dose of mtb?

A

1-10 bacilli

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25
Q

who receives bcg vaccine? why?

A

babies
protects from severe infection - but protection wanes

little use in adults

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26
Q

3 Stages of TB?

A

Primary
Latent
Reactivation

27
Q

Describe presentation of primary TB?

A 
Usually asymptomatic
Ghon focus/complex - granuloma
Limited by CMI - cell mediated immunity
Rare allergic reactions include Erythema nodosum
Occasionally disseminated/miliary
28
Q

post-primary tb occur in which 2 forms?

A

reactivation

reinfection

29
Q

Risk factors for reactivation of tb?

A

Immunosuppression
Chronic alcohol excess
Malnutrition
Ageing

30
Q

which will have a better immune response;

localised pulmonary tb OR
lymph node tb?

A

LN TB

31
Q

how does Bone TB present?

A

Potts disease:

  • affects spine
  • caseous necrosis leads to disc damage and collapse causing spinal damage:

Kyphosis
possible paraplegia

32
Q

most affected nodes in LN tb?

A

cervial nodes;
scrofula - leaks pus

aka Lymphadenitis

33
Q

presentation of TB?

A 
○ Fever 
		○ Weight loss - "wasting disease"
		○ Night sweats 
		○ Pulmonary (cough, haemoptysis) 
		○ Malaise
Anorexia
34
Q

gold standrad in tb diagnosis?

A

culture

takes weeks to return - slow growing

35
Q

ivx for latent tb?

A

Tuberculin skin test

IGRAs : interferon gamma release tests

36
Q

how many sputum samples needed in tb?

A

3

37
Q

maximum sensitivity of sputum samples for tb?

A

72%

38
Q

Role of NAAT for primary mtb samples?

A

Rapid diagnosis of smear +ve

Drug resistance mutations

39
Q

what does a tuberculin skin test tell you?

A

Previous exposure to Mycobacteria

40
Q

what should you look out for on histology of tb?

A

caseating granuloma

41
Q

what does induration size tell you in tuberculin test?

A

The reaction is read by measuring the diameter of induration .

a low-risk patient must have a larger induration for a positive result than a high-risk patient. example:

no risk factors: induration >15mm
HIV + : induration >5mm

42
Q

issues with IGRAs?

A

Cannot distinguish latent & active TB

43
Q

treatment for NTM?

A

RA/CE instead of RIPE

Rifampicin
Azithromycin/Clarithromycin
Ethambutol

44
Q

what is used (2nd line med) in isoniazid resistance?

A

Moxifloxacin

45
Q

side effects of Rifampicin?

A

Hepatotoxicity - raised transaminases

Induces cytochrome P450 - interaction with COCPs and anti-epileptics

Orange secretions - tell patients to watch out for this

46
Q

side effects of Isoniazid?

A

Peripheral neuropathy !!
Hepatotoxicity

SLE
Psychosis

47
Q

Why monitor LFTs closely in patient treated for TB?

A

RIP - causes hepatotoxicity

48
Q

Side effects of Pyrizinamide?

A

P for Painful joints - gout

Hepatotoxicity

49
Q

Side effects of Ethambutol?

A

E for Eyes:

Optic neuritis - Visual disturbance

50
Q

List FULL wholistic treatment components for tb

A

Multidrug therapy
Vitamin D - important in host defence

Nutrition
Surgery

51
Q

how does one take RIPE

A

Normal TB
RIPE for 2, RI for 4

CNS TB
RIPE for 2, RI for 8 (10 months total)

52
Q

which type of tb is resistant to fluoroquinolones (moxifloxacin) & at least 1 injectable

A

Extremely drug-resistant TB (XDR)

53
Q

how does Multidrug resistant TB present?

A

Resistance to rifampicin & isoniazid

both equally common

54
Q

reasons for multi drug resistant tb?

A

Previous TB Rx
HIV+
Known contact of MDR TB
Failure to respond to conventional Rx

55
Q

what is the WHO recommendation on MDR TB treatment?

A

Use 7 drugs

for 9-12 months

56
Q

challenges of a tb and hiv co-infection?

A

Clinical history Less likely to be classical
often absent in low CD4 count

More likely extrapulmonary disease

Smear CMS less sensitive

57
Q

what is the drug regimen for MDR TB?

A

QAPCE

○ Quinolones + aminoglycosides + para-aminosalicylic acid (PAS) + cycloserine + ethionamide

4/5 drug regimen with a longer duration

qap- key

58
Q

also check out GUM/HIV placement notes

A

black notebook

v useful

59
Q

name 3 slow growing NTM?

A

M. avium complex or avium Intracellulare

M. marinum

M. ulcerans

60
Q

name 3 fast growing NTM?

A

M. abscessus, M. chelonae, M. fortuitum

61
Q

name the first and second most common cause of death by infectious agent

A
  1. HIV

2. TB

62
Q

What percentage if world has tb

A

1/3rd

63
Q

how do we prevent peripheral neuropathy iwith isoniazid rx?

A

vitamin b6 - Pyridoxine

64
Q

out of RIP, which causes the most serious cases of hepatotoxicity?

A

isoniazid

Path - Microbiology (27 decks)

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