Tuberculosis Flashcards
Which country has the highest incidence of new cases?
India, 2 million new cases a year
What characteristics describe patient populations with high incidence of TB infections?
Immunocompromised Elderly Chronically malnourished Alcoholics Poor
What is the most significant factor for TB infections in the US?
HIV/AIDS infection
In the US, the homeless population is _____ more likely to be infected with TB…
…and racial minorities are __ more likely than whites.
In the US, the homeless population is 300X more likely to be infected with TB…
…and racial minorities are 5X more likely than whites.
This is the reaction that happens if a person that has been exposed to TB gets a PPD Skin test.
Delayed Type IV hypersensitivity reaction
After 48 hours (takes this long to respond): redness, swelling and hardness at site of injection.
Why is performing PPD skin test important?
It can help identify asymptomatic infections and allow patients to be treated before lung damage occurs.
The area of induration can be patient specific. Identify which patients will have the following areas of induration:
>5mm
>10 mm
>15 mm
> 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)
When is a false positive possible for PPD Skin tests?
Vaccination with bacillus-Calmette-Guerin Vaccine
has questionable efficacy, but it is widely used in countries with high TB rates
Name the pathogen that causes TB and describe its morphology
Mycobacterium tuberculosis
curved rods morphology
M. tuberculosis is an obligate ________ and is transmitted via __________.
OBLIGATE AEROBE; airborne transmission
What are the 2 most common locations for TB bacteria to proliferate? and WHY?
Apex of the lungs and Perihilar lymph nodes
Due to higher O2 concentrations.
What are the characteristic symptoms of TB?
LOWER respiratory infection
chronic productive cough (sputum, blood)
night sweats
weightloss
What is facultative intracellular growth?
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.
List the 3 types of Primary TB.
Asymptomatic, Symptomatic and Progressive.
Describe Primary Asymptomatic TB.
- 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
Describe Primary Symptomatic TB.
- common in elderly, children and the immunocompromised
- host eventually mounts response (delayed)
- mild symptoms (low grade fever, cough, etc)
Describe Primary Progressive TB.
- in subset population of immunocompromised
- Overt symptoms
- fluid-filled lung necrosis visible in chest xray and CT scan
Describe Secondary TB.
- most clinical cases
- any organ system can be affected after seeding from primary infection
- symptomatic: low-grade fever, productive cough, night sweats, weight loss.
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?
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.
What are the different sites of a 2ry TB infection?
Pulmonary, Pleural/Pericardial, Lymph Node, Renal, Skeletal, Nervous, Milliary
Describe the progression of a 2ry TB infection.
- bacteria grows and multiplies
- necrosis (caseous, encapsulation)
- liquefaction
4, cavitations
What is scrofula?
TB infection on the lymph nodes
most common site after lungs
What happens in a Pleural/Pericardial TB Infection?
fluid accumulates around lungs/heart
can cause issues with electrical conduction, infarct
What is Pott’s Disease?
TB in the Skeletal system: thoracic and lumbar spine.
Affects the intervertebral discs, causing destruction of the vertebral bodies, leads to fractures.
What is caseous necrosis?
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.
What is encapsulation?
A calcium barrier forms around necrotic tissue, containing the infection. Bacteria is not destroyed and may reactivate at a later time.
4 major Epidemiology Facts
- 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.
