TUBERCULOSIS

Question 1

Which three species cause TB?

Answer 1

M.tuberculosis

M.bovis

M. africanum

Question 2

Which genus are these species belong to?

Answer 2

mycobacterium

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

Question 3

characteristics of this genus?

Answer 3

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)

Question 4

What are Non-tuberculous mycobacteria (NTM)?

Answer 4

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)

Question 5

Other Various terminology used?

Answer 5

Environmental mycobacteria
Atypical mycobacteria
Opportunistic mycobacteria

Question 6

How do you get TB?

Answer 6

Inhale bacteria in respiratory droplets from an infectious person

Question 7

Timeline of bacteria once inhaled?

Answer 7

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

Question 8

How does the immune system attempt to minimize infection?

Answer 8

macrophages wall off the bacteria (granuloma)

Walled-off bacteria prevented from multiplying.

Question 9

What is a Latent TB infection?

Answer 9

Present but dormant (survival niche).

No further problem in most cases

Latent state with granuloma

Not infectious

Question 10

How is TB infectious tested?

Answer 10

if Immune system stimulated,

TST or IGRA positive after 6-10/52 weeks

Question 11

How can LTBI become TB?

Answer 11

If immunocompromised,

break out and cause disease.

become infectious

Question 12

What is Caseous necrosis?

Answer 12

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.

Question 13

Where is caseous necrosis common found in TB?

Answer 13

Picture was in lung, but can be anywhere in body

Lungs, brain, spine, lymph node TB is common

Question 14

What likely happens after exposure to TB?

Answer 14

Question 15

Why do people still have active disease if treated?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Who is vulnerable to TB?

Answer 17

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

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

Question 18

Who is more likely to come into contact with TB?

Answer 18

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

Question 19

What is classed as HIGH INCIDENCE COUNTRIES?

Answer 19

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

Question 20

Main symptoms of TB?

Answer 20

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

Question 21

what is the incidence of pulmonary TB?

Answer 21

73% of cases in 2019 had pulmonary TB

Question 22

what is Hemoptysis?

Answer 22

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

Advanced TB – if been misdiagnosed

Question 23

What happened in 1993?

Answer 23

“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

Question 24

Are Bacilli present in LTBI vs active TB?

Answer 24

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

Question 25

Symptoms in LTBI vs TB?

Answer 25

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

Question 26

Are people with LTBI infectious?

Answer 26

People with LTBI are NOT infectious

They CANNOT pass TB to others

TB disease is infectious if the lungs or larynx are affected

Question 27

Is LTBI a notifiable disease?

Answer 27

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

Question 28

what is DRTB?

Answer 28

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

Question 29

What is MDRTB?

Answer 29

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

Question 30

What is XDRTB?

Answer 30

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

Question 31

what is TDRTB?

Answer 31

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)

Question 32

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

Answer 32

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*)

Question 33

Changing epidemiology of TB?

Answer 33

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

Question 34

What happened in 1950s?

Answer 34

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)

Question 35

What happened in 1960s?

Answer 35

Increasing immigration to UK from high incidence countries

More TB seen in these groups after they arrived in UK

Question 36

The situation 1980s onwards?

Answer 36

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%*)

Question 37

What does an Early diagnosis depend on?

Answer 37

Symptom recognition (patient and health professional)

Access to health care

Appropriate assessments

Question 38

The many drugs used for treatment on TB?

Answer 38

Streptomycin (1943)
Isoniazid (1952)
Pyrazinamide (1952)
Ethambutol (1961)
Rifampicin (1966)

Newer drugs:
Bedaquiline (2012)
Delamanid (2014)
Benzothiazinones (2009)
Amidazopyridine Amide (2012)
Meropenem (1996)

Question 39

Previous wrong treatments for TB?

Answer 39

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