Brainscape's Knowledge GenomeTM

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


See full index

Clinical pathology > Mycobacteria > Flashcards

Mycobacteria Flashcards

1
Q

Mycobacteria

A

waxy cell wall
high lipid content
Growth is slow
slender bacili

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

Staining of mycobacteria

A

Does not take up normal stains (Gram Ghost cells)
Instead uses:
Ziehl-neelson
Pheno Auramine

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

Phases of Mycobateria in the body

A

Intracellular –> host responds via immune system –> Latent phase (not active for long periods) –> immunocompromised/Under stress leads to reactivation and chronic infection

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

Pathogenesis

A

Inhaled droplets

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

Primary tuberculosis pathogenesis

A

Primary acquisition (periphery of lung mid zone) –> phagocytosed by macrophages –> hilar lymph nodes (Ghon focus- lesion in mid/low zone of lungs, small area of granulotomous inflammation) –> multiplies inside –> disseminates via lymphatic system/ blood stream

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

Host response to Tubercle formation

A

Granuloma
Cell mediated Immune response
Epitheliod cells (activated macrophages that resemble epithelial cells)
Giant cells (Multinucleate fused from multiple cells e.g macrophage+monocyte)
leading to central area caseous (cheesy like) necrosis
Fibrosis/calcification of lesion

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

Features…what to do

A

Influenza like syndrome
Chest X-ray
Mantoux test (skin test)

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

Reactivated TB

A

Lowered immunity
Malnutrition
Alcoholism
Debilitating illness

HIV infection (more susceptible)

Silicosis, chronic renal failure, gastrectomy..
Anti TNFα blockade - needed for systemic inflammation (e.g. infliximab blocks it)

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

Clinical Features

A

Coalescing tubercles, central caseous necrosis
Cavitation: High organism load - risk of transmission.

Lung apices: highest oxygen tension.

Symptomatic:
Chronic productive cough
Haemoptysis
Weight loss, fever, night sweats

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

Extra-Pulmonary TB

A 
Miliary TB
Disseminated (miliary tuberculosis)
Very young / old; immunocompromised
1o - disease
2o - erosion of necrotic tubercle into blood vessel

Widespread infection, including meningitis.

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

Extra-Pulmonary sites

A 
Pleura
Lymph nodes
Kidneys , epididymis
Bone
Intestines
Brain / meninges
Pericardium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

TB meningitis

A 
Often insidious onset
Unidentified fever
Personality change
Focal neurological deficit
Basilar inflammation.
Mild headache / meningism.

May lack constitutional quartet
(fever, night sweats, anorexia, weight loss)

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

Diagnosis of TB

A 
Index of suspicion
Clinical
Radiology:	Chest X - ray.
Histology
Skin testing
(Blood test: Interferon- γ release assay: IGRA)

Microbiology.
Confirmation of diagnosis
Drug sensitivities.
Molecular typing profile: “MIRUs”.

“Fresh” samples / tissue: i.e. NOT formalin fixed

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

Microbiology:

A

Sputum: 3 “Early Morning” specimens.
(3 taken > 8 hours apart, with > one early morning) - when they wake up (first sputum’s)

Direct microscopy for AFBs
> 5000 organisms per ml sputum: “smear positive”
Risk of transmission

Culture:
Lowenstein - Jensen solid media: 3 - 4 weeks
Broth culture: automated, usually

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

What happens if it is a Positive AFB culture:

A

Referred to regional reference laboratory

Species identification

Sensitivities:
within two weeks

Strain typing

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

What other parameters to check

A

Lack of sputa:

  • Induced sputa: nebulised saline.
  • Bronchial aspirates
    - Environmental mycobacteria
  • Gastric aspirates

Renal -
“Sterile” pyuria
Early Morning Urines x3

CSF:
Cell count, protein, glucose
Microscopy / culture.
“Adequate” volume: > 6mls - increased yield

17
Q

How else to diagnose

A 
Nucleic acid amplification
Polymerase chain reaction (PCR)
Rapid
Less sensitive than culture
Expensive
Not 100 % specific - false positives.

Direct to clinical specimens
(including if only formalin fixed)
Speciation
Positive MGIT culture: TBcID® test:..TB or not TB
Resistance mutations: “known”, whole genome

18
Q

Treatment

A

Lengthy
Protocols - combined tablets
Resistance development:
DOTS: Directly Observed Therapy,Short - course

Standard 6 month regime:

Initiation phase:
Standard - pulmonary:
2 months Isoniazid, rifampicin, pyrazinamide ethambutol / (streptomycin)

Continuation Phase:
4 months: Isoniazid, rifampicin

Meningitis is 12 months

19
Q

Second line agents against TB

A

Amikacin (aminoglycoside)
Ethionamide / prothionamide
Cycloserine
Fluoroquinolones: ciprofloxacin, moxifloxacin

20
Q

Last line (MDR-TB)

A

Isoniazid and rifampicin resistant

Extensive drug resistant (XDR)

21
Q

Extensive drug resistant (XDR)

A

MDR +

Fluoroquinolone + injectable (amikacin or capreomycin)

22
Q

TB control

A

Notifiable disease
Contact tracing (who else might have got it)
Tuberculin Heaf test
Mantoux test (purified TB protein)
Blood test IGRA (Interferon gamma release assay)
Chest X-ray

Quarantine in air controlled room for 2 weeks
Identify patients with latent infection

23
Q

BCG vaccine

A

Attenuated strain of M BOVIS

24
Q

Mycobacterium Avium Complex

A

Patients who have had AIDS (low CD4 count)

Non HIV infected -
pulmonary: tuberculosis - like.
Young children: cervical lymphadenitis

25
Q

Diagnosis of NTM

A

Similar to TB

Microscopy / culture: AFBs

26
Q

Treatment of NTM

A

Combination
Prolonged
Macrolide – clarithromycin or azithromycin

27
Q

Leprosy

A

M.(mycobacterium) leprae

Non culturable in vitro

28
Q

Immune response to Leprosy

A

If the immune system can deal with it then….
Tuberculoid:
-Macules / plaques
-Nerve: ulnar, common perineal

If the immune system cannot deal with it then...
Lepromatous: 
-Multiplies in cooler areas of body
-Subcutaneous tissue accumulation.
-Ear lobes, face - leonine facies.
29
Q

Treatment of Leprosy

A

Dapsone, rifampicin, clofazimine

30
Q

Suspect TB

A

fever, weight loss, night sweats
Pulmonary – chronic cough; CXR changes.
Specific Microbiology request: AFBs

NOTIFIABLE DISEASE

Clinical pathology (5 decks)

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