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Comorbidities Flashcards

(75 cards)

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1
Q

What are the 3 diagnostic techniques used in TB?

A

Clinical history

Imaging - x-ray, CT

Microbiological investigations

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2
Q

What are examples of microbiological investigations used in TB?

A

Smear

Nucleic acid amplification tests

Culture

Antimicrobial susceptibilities of isolated mycobacterium tuberculosis

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3
Q

Why can samples for diagnosing TB be taken from many parts of the body?

A

TB can infect virtually anywhere, so samples received in the laboratory are varied

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4
Q

What are examples of sample types that can be taken to diagnose TB?

A

Pulmonary samples

Lymph nodes

Renal/Bladder

CSF

Biopsy or fluid aspiration from bone, joints, liver and other organs

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5
Q

When are pulmonary samples taken?

A

In cases of pulmonary TB

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6
Q

What are examples of pulmonary samples?

A

Sputum

Bronchoalveolar lavage/ washing

Pleural fluid

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7
Q

What are ways to obtain samples from the lymph nodes?

A

Lymph node dissection - excised entirely

Lymph node biopsy - fine needle aspirate

Imaging-guided biopsy

EBUS - endobronchial ultrasound biopsy of medisastinal nodes

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8
Q

Where are the mediastinal lymph nodes?

A

Center of the chest

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9
Q

What sample is taken from the renal/bladder?

A

Early morning urine samples

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10
Q

Why is CSF taken?

A

TB can cause meningitis and brain abcesses

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11
Q

Why are bone, joints and liver biopsies/aspirations taken?

A

As TB can go anywhere

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12
Q

M. tuberculosis is notoriously difficult to isolate and grow

TRUE or FALSE

A

TRUE

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13
Q

What are the difficulties in isolating M. tuberculosis?

A

Samples are often contaminated with other organisms

Some patients will not be able to produce sputum

Slow-growing organism

Samples are often paucibacillary

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14
Q

What happens if the patients are unable to produce sputum?

A

Bronchoscopy

Induced sputum

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15
Q

How can you induce sputum?

A

Inhale nebulised saline

Irritates the lung

Induces the production of sputum

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16
Q

How much time is needed for the M. tuberculosis to divide?

A

16-20 hours

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17
Q

What does paucibacillary mean?

A

Having or made up of few bacilli

Low number of organisms to start with

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18
Q

What type of organism is M.tuberculosis?

A

Hazard group 3

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19
Q

Which laboratory handles M. tuberculosis?

A

Containment level 3 laboratory

  • Special airflow
  • Equipment
  • Filters
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20
Q

What does a hazard group 3 organism mean?

A

Has potential to cause severe disease

Poses risk to people handling it
Potential to spread to people

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21
Q

How is the sample prepared for investigation?

A

Samples received have low numbers of bacteria

Need to concentrate by centrifugation to maximise yield

Non-sterile specimens are decontaminated to lyse other organisms

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22
Q

What is a smear?

A

Small proportion of concentrated sample

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23
Q

How is the smear prepared to be investigated?

A

Sample heat-fixed to microscope slides

Stained with a fluorescent stain such as auramine-O

Decolourise with 0.5-1% acid alcohol

Examine with a fluorescent microscope at x200-400 magnification

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24
Q

What is the purpose of decolorising the smear with acid alcohol?

A

Mycobacteria have lipid-rich walls

Pick up stain and retain them

If you see a fluorescent bacteria with microscope = definitely mycobacteria

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25
What are the advantages of fluorescent microscopy?
Easy to screen Better sensitivity than routine microscopy
26
All TB patients are smear-positive TRUE or FALSE
FALSE Around 90% are
27
What indications do smear-positive smears indicate about TB?
More likely to be infectious
28
What is done after a smear test comes back positive?
Get patient to treatment Make sure not pass to other people Quantify how positive a sputum slide is
29
What are the two procedures in which NAAT can be used to determine the antimicrobial susceptibility of the bacteria?
Genexpert Genotype MTBDRplus
30
What does Genexpert consist of?
Mini PCR laboratory inside a blue box
31
How is the sample added to the Genexpert machine?
Take out concentrated decontaminated sample Put in front of machine within 24 hours
32
What two things does the Genexpert machine determine?
Determines whether M. tuberculosis is present Tells us by looking at specific gene sequences if the organism is susceptible to a specific antibody
33
How is the sample added to the Genotype MTBDRplus machine?
Concentrated and decontaminated sample is amplified using PCR Nitrocellulose membrane with small sections of DNA bound to it
34
What does Genotype MTBDRplus test for?
Look for 3 specific genes involved in antibiotic resistance Those genes are amplified
35
What is the positive result for the presence of resistance genes in Genotype MTBDRplus?
Blue line
36
What is the gold-standard for diagnosing M.tuberculosis?
Culture
37
What is the main disadvantage of culture?
Slow process Takes 8 weeks
38
What is a culture method used to grow TV?
Lowenstein Jensen media Egg-based medium Concentrated decontaminated sample is inoculated onto the medium
39
What is a modern culture method?
Mycobacteria growth indicator tube system Fluorescent indicator flags when something grows in the tube
40
How does Mycobacteria growth indicator tube system work?
Fluorescent is bound to oxygen As bacteria grows and divides, uses the oxygen and disassociates it from the fluorescent molecule Sensor detects when something is growing Analyser flags when something grows in the tube
41
What type of growth medium is used in the Mycobacteria growth indicator tube system?
Liquid culture
42
What are the advantage of Mycobacteria growth indicator tube system?
Machine reads the growth automatically Less input from a scientist Growth time is faster in liquid media
43
What is another method of detecting the presence of M. tuberculosis?
Colour indicator on bottom CO2 produced by bacteria that divide and respire Drops the pH of the tube Every 10 minutes - pH is detected The colour of the indicator changes accordingly
44
What proportion of TB cases are multi-drug resistant?
5% of cases
45
What two drugs indicate MDR-TB?
Rifampicin Isoniazid
46
What if TB is only resistant to Isoniazid?
It is not considered MDR-TB
47
What are four ways in which patients acquire MDR-TB?
Infected with a resistant strain Poor compliance Poor absorption Interactions with other drugs causing subtherapeutic levels
48
What is the amount of time patients with TB have to take medication?
6 months
49
Why may patients not comply with the drug schedule?
Side-effects may make them stop taking the drugs since they feel better
50
What are the two ways to detect resistance?
Phenotypically Genotypically
51
Why is it important to detect resistance in the population?
Make sure the patient is on correct treatment Make sure the drug resistant strains don't spread
52
What is the phenotypic method for detecting resistance?
Isolates of M. tuberculosis are incubates in the presence of anti-TB drugs Gives absolute definite idea whether strain is susceptible
53
What are the pros of phenotypic testing for detecting resistance?
Gold-standard result Know that organism growing is categorically susceptible or resistant to antimicrobial agent
54
What are the cons of phenotypic testing for detecting resistance?
Takes time - weeks needed to know if the patient is on the correct treatment Need to isolate - 1/3 of cases can't Need laboratory facilities
55
What does the genotypic testing for detecting resistance entail?
Detect mutations on genes that may confer resistance
56
What are the pros of genotypic testing?
Speed - hours Can be performed on samples - no need to grow
57
What are the the cons of genotypic testing?
Less accurate than phenotypic methods Many gene mutations may not cause resistance Phenotypically can confer resistance whilst genotypically can be susceptible
58
What is the most sensitive method of diagnosing TB?
Culture > NAAT > smear
59
Why is NAAT less sensitive in diagnosing TB?
Lipid wall is very thick Difficult to obtain the RNA PCR not as effective
60
Why is it important to test for Mycobacteria TB specifically?
Over 130 species of mycobacteria Downstream tests needed to confirm it is tuberculosis
61
Why is TB called the great imitator?
A lot of symptoms overlap with other diseases
62
What are methods of monitoring TB after diagnosis and treatment?
Smear conversion Culture conversion Detection of acquired resistance
63
What is the process of smear conversion?
Look for the reduction of bacteria in smear Gives an idea of how the treatment is going If the sputum that is coughed up contains less bacteria = antibiotics are effective
64
What is the main disadvantage of smear conversion?
Arbitrary system Quantifying the number of bacteria is difficult Quality of sample differs between periods of taking the samples Not absolute
65
What is culture conversion?
Look for not being able to grow the bacteria in the sputum of the patient
66
How can we detect acquired resistance?
Need to find out why bacteria are resistant Sensitive stains may have acquired resistance due to - poor compliance - poor absorption of antibiotics
67
How are the patients managed following TB diagnosis?
Anti-tuberculosis treatment Clinical and microbiological improvement
68
What anti-tuberculosis treatment is used?
Empirical first Modified based on drug susceptibility tests
69
How is clinical and microbiological improvement tested for?
Smear and culture conversion Improvement in clinical well-being Look for - improvement of inflammatory markers - weight gain - improvement of imaging
70
What inflammatory markers are used to look for clinical and microbiological improvement?
White cell count C-reactive protein levels
71
What is seen when patients improve in CXR?
Consolidations or cavities improve
72
What are other important infections in HIV?
Oral candidiasis Mycobacterium avium PCP
73
What is PCP?
Pneumocystitis jiroveci pneumonia Fungal disease
74
What is oral candidiasis?
Yeast that can grow abundantly in the mouth
75
What is Mycobacterium avium?
Severe intestinal disease Disseminated disease like sepsis in advanced HIV

PPS - infections (8 decks)

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