Tuberculosis

Question 1

Which country has the highest incidence of new cases?

Answer 1

India, 2 million new cases a year

Question 2

What characteristics describe patient populations with high incidence of TB infections?

Answer 2

Immunocompromised
Elderly
Chronically malnourished
Alcoholics
Poor

Question 3

What is the most significant factor for TB infections in the US?

Answer 3

HIV/AIDS infection

Question 4

In the US, the homeless population is _____ more likely to be infected with TB…
…and racial minorities are __ more likely than whites.

Answer 4

In the US, the homeless population is 300X more likely to be infected with TB…
…and racial minorities are 5X more likely than whites.

Question 5

This is the reaction that happens if a person that has been exposed to TB gets a PPD Skin test.

Answer 5

Delayed Type IV hypersensitivity reaction

After 48 hours (takes this long to respond): redness, swelling and hardness at site of injection.

Question 6

Why is performing PPD skin test important?

Answer 6

It can help identify asymptomatic infections and allow patients to be treated before lung damage occurs.

Question 7

The area of induration can be patient specific. Identify which patients will have the following areas of induration:
>5mm
>10 mm
>15 mm

Answer 7

> 5mm : HIV/AIDS or immunosuppressed patients
10mm : healthcare workers, high incidence country, high risk conditions (diabetes, renal failure)
15mm : all others (healthy, do not fit any of the above criteria)

Question 8

When is a false positive possible for PPD Skin tests?

Answer 8

Vaccination with bacillus-Calmette-Guerin Vaccine

has questionable efficacy, but it is widely used in countries with high TB rates

Question 9

Name the pathogen that causes TB and describe its morphology

Answer 9

Mycobacterium tuberculosis

curved rods morphology

Question 10

M. tuberculosis is an obligate ________ and is transmitted via __________.

Answer 10

OBLIGATE AEROBE; airborne transmission

Question 11

What are the 2 most common locations for TB bacteria to proliferate? and WHY?

Answer 11

Apex of the lungs and Perihilar lymph nodes

Due to higher O2 concentrations.

Question 12

What are the characteristic symptoms of TB?

Answer 12

LOWER respiratory infection
chronic productive cough (sputum, blood)
night sweats
weightloss

Question 13

What is facultative intracellular growth?

Answer 13

It is the mechanism by which the TB bacteria evades the host defenses and can survive phagocytosis my the macrophage, multiply and invade other tissues.

Question 14

List the 3 types of Primary TB.

Answer 14

Asymptomatic, Symptomatic and Progressive.

Question 15

Describe Primary Asymptomatic TB.

Answer 15

• host shows no clinical symptoms of infection
• the host acquires cell-mediated immunity upon exposure
• necrosis, encapsulation and cavitations in lungs WILL be present
• often goes undiagnosed unless PPD Skin Test performed

Question 16

Describe Primary Symptomatic TB.

Answer 16

• common in elderly, children and the immunocompromised
• host eventually mounts response (delayed)
• mild symptoms (low grade fever, cough, etc)

Question 17

Describe Primary Progressive TB.

Answer 17

• in subset population of immunocompromised
• Overt symptoms
• fluid-filled lung necrosis visible in chest xray and CT scan

Question 18

Describe Secondary TB.

Answer 18

• most clinical cases
• any organ system can be affected after seeding from primary infection
• symptomatic: low-grade fever, productive cough, night sweats, weight loss.

Question 19

What is the likelihood that a patient with HIV/AIDS with a primary exposure will develop 2ndary TB? How does this compare to a healthy patient?

Answer 19

There is a 10% yearly chance of TB reactivation in a pt with HIV/AIDS.
In a healthy patient there is a 10% of TB reactivation in a LIFETIME.

Question 20

What are the different sites of a 2ry TB infection?

Answer 20

Pulmonary, Pleural/Pericardial, Lymph Node, Renal, Skeletal, Nervous, Milliary

Question 21

Describe the progression of a 2ry TB infection.

Answer 21

1. bacteria grows and multiplies
2. necrosis (caseous, encapsulation)
3. liquefaction
   4, cavitations

Question 22

What is scrofula?

Answer 22

TB infection on the lymph nodes

most common site after lungs

Question 23

What happens in a Pleural/Pericardial TB Infection?

Answer 23

fluid accumulates around lungs/heart

can cause issues with electrical conduction, infarct

Question 24

What is Pott’s Disease?

Answer 24

TB in the Skeletal system: thoracic and lumbar spine.

Affects the intervertebral discs, causing destruction of the vertebral bodies, leads to fractures.

Question 25

What is caseous necrosis?

Answer 25

Tissues infected with TB are targeted and killed during the cell-mediated immune response. The necrosis that ensues is granular with a creamy, cheese-like appearance.

Question 26

What is encapsulation?

Answer 26

A calcium barrier forms around necrotic tissue, containing the infection. Bacteria is not destroyed and may reactivate at a later time.

Question 27

4 major Epidemiology Facts

Answer 27

• TB kills 9 million people a year
• India is the country with the most new cases (2 mill)
• Sub-Saharan Africa and South-East Asia have the most incidence of new cases.
• South-East Africa has the highest incidence rate of co-infections with HIV/AIDS.