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medical microbiology > TUBERCULOSIS > Flashcards

TUBERCULOSIS Flashcards

1
Q

Which three species cause TB?

A

M.tuberculosis

M.bovis

M. africanum

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2
Q

Which genus are these species belong to?

A

mycobacterium

Greek Myco: fungus (or wax) grow in a mold-like manner on the surface of cultures

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3
Q

characteristics of this genus?

A

Obligate aerobe, rod-shaped, non-motile, AFB

(ZN/auramine not Gram due to lipid-rich wall and no phospholipid outer membrane)

> 190 species ubiquitous in the environment (most are not usually pathogenic to humans)

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4
Q

What are Non-tuberculous mycobacteria (NTM)?

A

Umbrella term for all other mycobacteria than the three that cause TB

Mycobacteria don’t cause TB,

they can cause opportunistic mycobacterial infection particularly in immunocompromised people (e.g. HIV)

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5
Q

Other Various terminology used?

A

Environmental mycobacteria
Atypical mycobacteria
Opportunistic mycobacteria

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6
Q

How do you get TB?

A

Inhale bacteria in respiratory droplets from an infectious person

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7
Q

Timeline of bacteria once inhaled?

A

Bacteria reach the lung and slowly multiply over several weeks

(divide every ~24H. V slow compared to other bacteria, measured in mins)

Can spread to other parts of body via blood or lymphatic system

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8
Q

How does the immune system attempt to minimize infection?

A

macrophages wall off the bacteria (granuloma)

Walled-off bacteria prevented from multiplying.

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9
Q

What is a Latent TB infection?

A

Present but dormant (survival niche).

No further problem in most cases

Latent state with granuloma

Not infectious

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10
Q

How is TB infectious tested?

A

if Immune system stimulated,

TST or IGRA positive after 6-10/52 weeks

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11
Q

How can LTBI become TB?

A

If immunocompromised,

break out and cause disease.

become infectious

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12
Q

What is Caseous necrosis?

A

or caseous degeneration isa unique form of cell death in which the tissue maintains a cheese-like appearance.

It is also a distinctive form of coagulative necrosis.

The dead tissue appears as a soft and white proteinaceous dead cell mass.

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13
Q

Where is caseous necrosis common found in TB?

A

Picture was in lung, but can be anywhere in body

Lungs, brain, spine, lymph node TB is common

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14
Q

What likely happens after exposure to TB?

A
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15
Q

Why do people still have active disease if treated?

A

Treatment TB if for 6 months but many do not complete course as feel better then relapse
Reason for active disease

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16
Q

Who’s most likely to get TB from contagious person?

A

not the most contagious

Close contacts (usually household) of infectious cases

Pebble in the pond, start with those live with if they test positive, then you move to people less close and so on if continue positive

17
Q

Who is vulnerable to TB?

A

People with weakened immune systems (e.g. HIV)

Those with chronic poor health/nutrition/access to healthcare (homelessness, drugs, alcohol, prison)

18
Q

Who is more likely to come into contact with TB?

A

Those living in communities of people originating from high incidence countries

People from/who live in/travel to/receive visitors from countries where TB is common

19
Q

What is classed as HIGH INCIDENCE COUNTRIES?

A

Countries with an annual incidence rate of ≥40/100,000 population are

20
Q

Main symptoms of TB?

A

Fever
Massive weight loss (once called consumption as consumed the body)
Night sweats
Loss of appetite
If in lungs - shortness of breath and cough

21
Q

what is the incidence of pulmonary TB?

A

73% of cases in 2019 had pulmonary TB

22
Q

what is Hemoptysis?

A

refers to coughing up blood from some part of the lungs (respiratory tract).

Advanced TB – if been misdiagnosed

23
Q

What happened in 1993?

A

“TB IS A GLOBAL PUBLIC HEALTH EMERGENCY”

~10 MILLION NEW CASES IN 2018

~10 MILLION CHILDREN ORPHANED BY TB

~1.5 MILLION PEOPLE DIED OF TB IN 2019

~2.6 BILLION PEOPLE WITH LTBI

24
Q

Are Bacilli present in LTBI vs active TB?

A

LTBI - Bacilli are present in the body but immune system prevents them multiplying rendering them INACTIVE

Bacilli are present in the body but immune system cannot prevent them multiplying rendering them ACTIVE

25
Q

Symptoms in LTBI vs TB?

A

People with LTBI do NOT have any symptoms - People with LTBI do NOT know they have TB infection in their body

Patients with TB disease will develop symptoms

26
Q

Are people with LTBI infectious?

A

People with LTBI are NOT infectious

They CANNOT pass TB to others

TB disease is infectious if the lungs or larynx are affected

27
Q

Is LTBI a notifiable disease?

A

NO

People with LTBI are NOT classed as cases of TB

Active TB disease is a statutorily notifiable disease in many countries, including the UK

28
Q

what is DRTB?

A

Resistance to one of the 4 first-line drugs (RIPE)

29
Q

What is MDRTB?

A

Resistance to at least 2 of the first-line drugs (I and R)

30
Q

What is XDRTB?

A

MDRTB plus resistance to fluoroquinolones (cipro etc) and any of the 3 second-line injectable drugs (amikacin, capreomycin, kanamycin)

31
Q

what is TDRTB?

A

Totally drug-resistant TB (relatively new and little understood phenomenon, not accepted by WHO as insufficient broad range testing in most countries, but Iran, India, Italy)

32
Q

Drug-resistant strains are not more virulent or infectious, but consequences are grave

A

Resistance prolongs the infectious period

Effectiveness of treatment is compromised

Loss of main bacteriostatic and bactericidal drugs

Second-line drugs are more toxic

Mortality rate is higher

Management more difficult and costly (5K v 50K*)

33
Q

Changing epidemiology of TB?

A

TB was declining in this country long before medical interventions.

Social changes underlie this control.

Chemotherapy – antibiotics (any chemical medicine)

First one effective against TB

34
Q

What happened in 1950s?

A

50,000 cases of TB each year in the UK

Usually in white, UK-born adolescents/young adults

Across all sectors of society

Hence universal BCG vaccine programme (schools)

35
Q

What happened in 1960s?

A

Increasing immigration to UK from high incidence countries

More TB seen in these groups after they arrived in UK

36
Q

The situation 1980s onwards?

A

Trend in immigration continued

TB changed from being a disease of the general population to one predominantly affecting certain sub-groups of the population

Number of cases in UK-born population has fallen and remains low

Number of cases in people born outside UK is increasing AND is high (15x that of UK-born: 74%*)

37
Q

What does an Early diagnosis depend on?

A

Symptom recognition (patient and health professional)

Access to health care

Appropriate assessments

38
Q

The many drugs used for treatment on TB?

A 
Streptomycin (1943)
Isoniazid (1952)
Pyrazinamide (1952)
Ethambutol (1961)
Rifampicin (1966)
Newer drugs:
Bedaquiline (2012)
Delamanid (2014)
Benzothiazinones (2009)
Amidazopyridine Amide (2012)
Meropenem (1996)
39
Q

Previous wrong treatments for TB?

A

Sunlamps for heliotherapy
Patient receives pneumothorax treatment. Canada 1940s.
Beds outside for fresh air, to improve breathing

medical microbiology (29 decks)

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