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4.1 Medical Microbiology > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Write a note on the frequency of TB according to the WHO Global TB Report 2020
(7)

A

TB is the leading cause of death from a single infectious agent

In 2020 there were 10 million cases and 1.4 million deaths

8.2% of cases were in people with HIV

500,000 people developed rifampicin-resistant TB (RR-TB)

78% of (RR-TB?) people had multidrug-resistant TB (MDR-TB)

3.3% of new TB cases and 17.7% of previously treated cases had MDR/RR-TB

Covid-19 pandemic threatens to reverse recent progress in reducing the global burden of TB

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2
Q

What is the most recent worldwide study on TB?

A

WHO Global TB Report 2020

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3
Q

How many cases of TB were there in 2020 and how many deaths?

A

10 million cases and 1.4 million deaths

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4
Q

How many cases of TB were there in 2020 and how many deaths?

A

10 million cases and 1.4 million deaths

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5
Q

Of the 10 million cases of TB in 2020, what percentage of these patients had HIV?

A

8.2% of cases were in HIV patients

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6
Q

Out of the 10 million cases of TB in 2020, how many developed rifampicin-resistant TB

A

500,000 people developed RR-TB

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7
Q

Out of the 500,000 cases of RR-TB in 2020, what percentage had multidrug-resistant TB

A

78% had MDR-TB

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8
Q

What is defined as multi-drug resistant TB?

A

Resistance to at least both isoniazid and rifampicin

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9
Q

What percentage of the 10 million cases of TB in 2020 were MDR TB?

A

3.3% of newly diagnosed cases were MDR

17.7% of previously treated cases were MDR -> rate of multi-drug resistance increases with failure to complete antiboitic course etc etc

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10
Q

According to the WHO 2020 report, how many estimated patients never get diagnosed or treated with TB?
Why is this significant?

A

WHO estimates that over 4 million cases of TB are not diagnosed or treated a year

Suggests there could by potentially 4 million infectious patients acting as a reservoire for potential spread

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11
Q

According to the WHO report of 2020, what percentage of resistant TB cases are detected?

A

Less than 25% of resistant cases are detected

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12
Q

Where in the world is there a significant burden of TB

A

Mostly Africa
Other third world countries where there is overcrowding etc e.g. India

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13
Q

What are the 6 main reasons why TB has not gone away?

A

HIV epidemic
Immigration
Increased poverty
Non compliant drug-therapy
Overcrowding
Latent tuberculosis

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14
Q

How has the HIV epidemic affected TB rates?

A

The HIV epidemic resulted in a large population of immunodeficient patients which were more susceptible to picking up TB

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15
Q

How has immigration affected TB rates?

A

There has been an increase in immigration from countries such as Africa and India where there is a much higher prevalence of TB

People from other countries entering Ireland with TB, increasing our stats as well as causing spread of disease to Irish population

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16
Q

How has an increase in poverty affected TB stats?

A

Increased poverty -> increase in homelessness -> increase in intraveous drug use

Think of homeless in Mater getting TB from rats and pigeons due to living conditions etc

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17
Q

How does non-compliant drug therapy affect TB stats?

A

Course of antibiotics between 6 and 9 months
Very difficult for patients to finish
Not finishing course of antibiotics results in TB returning or multi-drug resistant TB -> patient remains reservoire -> spread to others etc

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18
Q

How does overcrowding affect TB stats?

A

Overcrowding in prisons -> low socioeconomic inmates -> only need 1 with TB to spread to a lot of other prisoners etc
Overcrowding in hospitals -> spread to nearby patients etc -> immunocompromised patients etc

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19
Q

How does latent TB affect TB stats?

A

Latent TB stays in the lung as a granuloma
Latent TB can become reactive at any point in life
Potentially infectious individuals

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20
Q

What countries are most affected by TB?
(according to WHO)

A

India
Indonesia
China
Philippines
Pakistan
Nigeria
Bangladesh
Democratic republic of congo

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21
Q

Out of the 10 million TB cases in 2020, 8.2% were in HIV patients, where was the burden of these cases?

A

Over 50% of these 8.2% of cases were in Southern Africa

=> Over 4% of worlwide cases of TB were in HIV patients in southern Africa

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22
Q

Write a note on TB in Ireland based on the most recent study in 2019
(9 points of information)

A

267 TB cases
Incidence rate of 6.7 per 100,000
Incidence rate of 10.2 in those over 65 years old
40% are Irish born
44% are foreign born cases
Only 196 (73%) cases are culture positive
~10%/27 cases were resistant (5 MDR and 5 mono RF)
1 meningitis case caused by M.bovis
6 TB outbreaks

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23
Q

What was the total number of TB cases in ireland in 2019?

A

267 TB cases

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24
Q

What is the incidence rate of TB in Ireland?

A

Incidence of 6.7 per 100,000

This increases to 10.2 in those over 65 years old

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25
Out of the 267 TB cases in ireland in 2019, what percentage were irish orn vs foreign born?
40% were irhs and 44% were foreign born
26
Out of the 267 TB cases in Ireland in 2019 what percentage of these were culture positive?
196/267 were culture positive = 73% were culture positive Could have potentially missed 71 cases if only traditional culture used
27
Out of the 276 cases of TB in ireland in 2019, how many of these were resistant
27 of these cases were resistant 5 of these were MDR 5 of these were mono Rf
28
How many TB outbreaks were there in 2019 in ireland
6 outbreaks
29
Comment on the rates of TB over the years in Ireland
TB numbers have been steadily decreasing e.g. from nearly 400 in 2013 to justo ver 200 in 2021 There was a slight increas in 2022 but not above pre-pandemic levels i.e. downward trend in TB cases in Ireland
30
Talk about the trends in drug resistant TB in Ireland over the years
Numbers always small but resistance is definitely increasing e.g. only 4 MDR-TB and 1 XDR-TB in 2013 vs 8 MDR-TB, 4 mono Rf-TB and 2 pre-XDR cases in 2022 Doubled
31
List and explain the different kinds of resistance in TB (Got these online, american version, who guidelines in layer flashcard)
mono RR-TB: TB resistance against rifampicin only MDR-TB: Multi-drug resistant TB (rifampicin and isoniazid) Pre-XDR TB: isoniazid, rifampicin and a fluoroquinolone OR a second line injectable (amikacin, capreomycin and kanamycin) XDR-TB: extensively drug resistant TB -> isoniazid, rifampicin, a fluoroquinolone AND a second line injectible OR isoniazid, rifampicin, a fluoroquinolone and bedaquiline or linezolid
32
Explain what is Pre-XDR TB
Resistance against isoniazid, rifampicin and a fluoroquinolone OR a second line injectable (amikacin, capreomycin and kanamycin)
33
Explain what is Pre-XDR TB
Resistance against isoniazid, rifampicin and a fluoroquinolone OR a second line injectable (amikacin, capreomycin and kanamycin)
34
What are the second line injectables used to treat TB? (3)
Amikacin Capreomycin Kanamycin
35
What is meant by XDR TB?
extensively drug resistant TB Resistance against isoniazid, rifampicin, a fluoroquinolone AND a second line injectible OR resistance against isoniazid, rifampicin, a fluoroquinolone and bedaquiline or linezolid
36
Write a short note on the Mycobacterium species
Acid-fast characteristic feature Over 90 species identified Characteristic cell wall
37
What is mean by acid-fast
When Mycobacterium is stained with a basic dye it cannot be decolourised subsequently with dilute acids
38
Write a note on the mycobacterium cell wall
Acid fast Major determinant of virulence Unique stucture Unique lipid fraction (lipid section of wall) Role in resistance
39
Write a note on the mycobacterium cell wall
Acid fast Major determinant of virulence Unique stucture Unique lipid fraction (lipid section of wall) Role in resistance
40
What makes the cell wall of mycobacterium unique?
Presence of peptidoglycan and complex lipids High lipid content - can be up to 60% of wall Hydrophobic and waxy This waxy wall takes a lot of nutrients to develop and is one of the reasons why mycobacterium takes so long to grow
41
What are the three main components of the mycobacterium lipid fraction of the cell wall
Mycolic acids Cord factor Wax-D
42
What is the role of mycolic acids in the lipid fraction of the mycobacterium cell wall?
These allow the bacterium to grow inside macrophages -> immune evasion Essential for the pathogenisis of tuberculosis and leprae These are also whats resposible for the acid-fast property of the wall
43
What is the role of mycobacterium waxy cell wall in resistance?
Makes organism resistant against antibitoics Resistance against phagocytosis
44
What is the role of cord factor in the cell wall of mycobacterium?
Cord factor is a major component of the cell wall It is toxic to mammalian cells It inhibits phagocytosis Cord factor induces the formation of granulomas Major virulence factors -> M. TB without cord factor are avirulent and virulent strains which loose their ability to produce cord factor loses its virulence
45
How does Cord factor prevent phagocytosis?
Cord factor prevents the fusion between phagosomal vesicles containing the M, tubercuosis cells and the lysosomes that would destroy them This allows M.TB to survive within immune cells
46
What is the role of Wax-D in the waxy cell wall of Mycobacterium?
Role in resisting phagocytosis
47
How does Wax-D prevent phagocytosis?
Regulates internal acidity by preventing hydrogen ion entering the phagosome -> ensures bacterial DNA replication Prevents oxidation burst inside the phagosome (i have no idea what this means)
48
What does MTC stand for?
Mycobacterium tuberculosis Complex
49
What does NTM stand for?
Non Tuberculous mycobacteria
50
What does NTM stand for?
Non Tuberculous mycobacteria
51
Give some examples of mycobacterium that are part of the mycobacterium tueberculosis complex
M. tuberculosis M. bovis subspecies bovis M. bovis subspecies caprae M. bovis BCG
52
Write a note on M tuberculosis (5)
An acid fast bacillus Highly contagious Aerosolised droplets Mainly affects lungs but can affect any organ 1/3 people carry latent infection worldwide (1 in 4 irish) -> 10 percent may develop an active infection
53
Write a note on M tuberculosis (5)
An acid fast bacillus Highly contagious Aerosolised droplets Mainly affects lungs but can affect any organ 1/3 people carry latent infection worldwide (1 in 4 irish) -> 10 percent may develop an active infection
54
It is estimated that what percentage of people carry latent M. tuberculosis?
1 in 3 carry latent M TB infection worldwide 1 in 4 in Ireland (Cant find stats for this)
55
It is estimated that what percentage of people carry latent M. tuberculosis?
1 in 3 carry latent M TB infection worldwide 1 in 4 in Ireland (Cant find stats for this)
56
What percentage of latent MTB will become active at some point in life?
10% will become active
57
What percentage of latent MTB will become active at some point in life?
10% will become active
58
what are the five main symptoms of M. TB
Chronic cough Haemoptysis -> blood in sputa Drenching night sweats Weight loss Pyrexia
59
What marks the formation of latent TB
Formation of granulomas in the lung This happens when immune system is unable to clear infection -> TB resides in these granulomas -> can be reactivated at any point
60
How long will a person have latent TB for?
Latent TB is lifelong
61
How long will a person have latent TB for?
Latent TB is lifelong
62
How can you test to see if a person has TB?
TST Skin test Chest X ray Interferon gamma
63
What is the skin test for TB?
Mantoux tuberculin skin test (TST) Involves injecting purified protein derivative (PPD) solution and measuring the size of the welt/swelling
64
What is the interferon test for M. TB?
Interferon Gamma Release Assay (IGRA) A blood test used to see if person infected with M TB Measures bodys immun response to TB
65
After exposure to M TB, how would you prove a person TB negative?
Negative TST or IGRA Patient does not develop latent TB (X ray clear of granulomas) Patient does not devlop TB disease Patient not infectious
66
After exposure to M TB, how would you prove a person TB negative?
Negative TST or IGRA Patient does not develop latent TB (X ray clear of granulomas) Patient does not devlop TB disease Patient not infectious
67
After exposure to MTB how would you prove a person has latent TB
Positive TST or IGRA Normal chest radiograph -> no TB Disease Latent TB -> might develop symptoms later in life but not currently infectious
68
After exposure to TB, how would you prove a person has a MTB infection?
Positive TST or IGRA Abnormal chest radiograph - evidence of TB disease Symptomatic patient Positive culture -> might have to wait a few weeks Patient has TB disease and is infectious
69
What would be a good sign a TB patient will be culture positive?
If interferon gamma positive
70
In general what is active TB?
Positive skin test/interferon gamma, positive sputum, positive xray
71
What are the different stages of TB
Primary tuberculosis (infection beginning usually STS and xray negative) Progressive primary (active) infection (STS, xray and sputum positive) Latent-dormant tuberculosis (sts positive but xray neg) Secondary (reactivation) tuberculosis (sts, xay and sputum positive)
72
What are the different stages of TB
Primary tuberculosis (infection beginning usually STS and xray negative) Progressive primary (active) infection (STS, xray and sputum positive) Latent-dormant tuberculosis (sts positive but xray neg) Secondary (reactivation) tuberculosis (sts, xay and sputum positive)
73
What are some risk factors for TB?
Exposure to an individual with active TB Large infecting dose Age and gender Health conditions Malnutrition Smoking, silicosis Occupation Immune condition Stress
74
How is infectious dose a risk factor for TB?
A large infectious dose means you are more likely to be infectious
75
How is infectious dose a risk factor for TB?
A large infectious dose means you are more likely to be infectious
76
What health conditions are risk factors for TB
Leukaemia Hodgkins Disease Diabetes Mellitus Alcoholism IV drug abuse
77
What aspects of malnutrition are risk factors or TB
Low body weight Vitamin D deficiency
78
What aspects of malnutrition are risk factors or TB
Low body weight Vitamin D deficiency
79
What immune conditions are risk factors for TB?
Immunosuppression Corticosteroid treatment
80
What are the requirements for a TB diagnosis? (5)
Cough for 3+ weeks with at least one additional symptom Any patient at high risk of TB with unexplained illness including respiratory symptoms of 3+ weeks Any HIV patient with unexplained cough and fever Any high risk patient with a diagnosis of CA pneumonia who has not improved after seven days of treatment Any high risk patient with incidental findings on chest X ray suggestive of TB even if symptoms are minimal or absent
81
Talk about the microbial investigation of MTB
Microscopy -> cheap and fast but limit of detection not great, negative microscopy doesnt always mean negative patient, positive miroscopy is definitely positive NAAY -> nucleic acid amplification test -> best method Culture -> very slow, takes about 8 weeks (clinicians usually start treatment while awaiting culture)
82
What are three extra pulmonary forms of TB?
Lymphadenitis Miliary TB Tuberculosis Meningitis
83
What are three extra pulmonary forms of TB?
Lymphadenitis Miliary TB Tuberculosis Meningitis
84
What is lymphadenitis in TB?
This is where TB has spread to the cervical lymph nodes
85
What is miliary TB?
This is where TB has spread to the blood Will see infected lesions on X ray Millet seeds (tiny tubercles) Progressive Disseminated Haematogenous TB
86
What is miliary TB?
This is where TB has spread to the blood Will see infected lesions on X ray Millet seeds (tiny tubercles) Progressive Disseminated Haematogenous TB
87
What is tuberculosis meningitis
This is where TB crosses the blood/brain barrier Not really seen in Ireland -> 1 case in 2019 -> more of a problem in other countries
88
What are the first line anti tuberculosis drugs?
Isoniazid Rifampicin Pyrazinamide Ethambutol
89
What are the main side effects of rifampicin?
Many drug interactions, check for any other medication Discoloration of urine and contact lenses Hepatotoxic
90
What are the main side effects of isoniazid?
Pyridoxine (Vit B6) must be given to prevent INH (isoniazid) induced neuropathy Hepatotoxic
91
What is the main side effect of pyrazinamide?
Hepatotoxic
92
What is the main side effect of pyrazinamide?
Hepatotoxic
93
What are the main side effects of ethambutol
Risk of ocular toxicity Must check baseline renal function Regular visual acuity and colour discrimination
94
What are the main side effects of ethambutol
Risk of ocular toxicity Must check baseline renal function Regular visual acuity and colour discrimination
95
What are the two main concerns with antimicrobial treatment for MTB
Patients have to take medications for 6 to 9 months -> problems with compliance Long course -> hepatic toxicity
96
What is the work-around if there is concerns over anti-microbial compliance?
DOTS -> direct obsrved therapy Done either inpatient or over video call -> clinician has to watch patient take medication Much shorter course
97
What is the WHO definition of RR-TB
TB resistant to rifampicin detected using phenotypic or genotypic methods with or without resistance to other anti-TB drugs
98
What is the WHO definition of XDR TB
TB which are MDR-TB and also resistat to any fluoroquinalone and at least one additional group A drug (loveofloxacin, moxifloxacin, bedaquilline and linezolid)
99
What does WHO class as group A drugs? (4)
Levofloxacin Moxifloxacin Bedaquiline Linezolid

4.1 Medical Microbiology (30 decks)

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