L17: Tuberculosis Flashcards
Def of Tuberculosis
- Tuberculosis (TB) is an airborne bacterial infection caused by Mycobacterium tuberculosis
TB is a major global cause of disability & death especially in …… countries
developing
TB morbidity and mortality rates were decreased but started to re-emerge again due to:
Global epidemeology of TB
National Epidemeology of TB
- Egypt is ranked among the mid-level incidence countries.
- TB in Egypt is considered an important public health problem.
Suspected Case of TB
any patient with cough & expectoration more than 3 weeks associated with fever, loss of weight& night sweating
Probable Case of TB
None
Confirmed Case of TB
positive lab results and positive chest radiography
CA of TB
Mycobacterium tuberculosis: highly resistant outside the body
Reservoir of TB
Human open cases of TB (TB lesion open into a bronchus).
IP of TB
to 10 w (from infection till +ve tuberculin test of appearance of a 1ry lesion)
MOT of TB
Air-borne infection
Infectivity Period of TB
- As long as viable bacilli are discharged in the sputum
- Risk of transmission is significantly reduced within days to 2 weeks after starting appropriate chemotherapy
Susceptible age for TB
(Golden age: the safe period 5-15 years due to less exposure & stress)
Susceptible sex for TB
More in males than females (ratio 3-1 to 5-1)
Immunity in TB
- Immunity after primary infection or vaccination (cell mediated).
- No maternally acquired immunity.
Dx of TB
Screening tests for detection of TB (IGRA and Tuberculin test)
Principle of Tuberculin test
An intradermal test for delayed cell mediated
hypersensitivity caused by exposure to TB antigen
whether by infection or vaccination.
Non-vaccinated positive child < 5 years …….
needs further investigations to exclude infection
what does a Positive tuberculin means?
❶ TB infection (recent or past)
❷ vaccination
Results of Tuberculin test
Steps of Tuberculin test
The test material (purified protein derivative) is injected of as 5 IU (one IU for children & persons likely to react strongly)
Recent conversion of a person who was previously negative is ……
suggestive of TB
Negative tubercelin test
Advantaes of Interferon gamma release assays (IGRA)
Disadvantages of Interferon gamma release assays (IGRA)
General Prevention of TB
(as mentioned in general preventive measures of droplet inf)
Specific Prevention of TB
- Active Vx
- Chemoprophylaxis
- Combined
Active Vx for TB
BCG
Nature of BCG
Live-attenuated bovine strain of mycobacterium TB
Dose of BCG
0.1 ml I.D, in the left upper arm
Indications of BCG
❶ In Egypt, it is compulsory in the first three months of life without tuberculin
❷ Older children & adult if only tuberculin negative
❸ At risk groups: health workers, military recruits, & food handlers
Indication of success of BCG
Indication of failure of BCG
If there is no scar formation, repeat vaccination after 3 months
Protective value of BCG
Type of immunity of BCG
It gives cellular immunity.
Does BCG give cross immunity?
yes
Chemoprophylaxis in TB
INH is the drug of choice
❶ Given to high risk groups such as contacts of cases.
❷ Effective in prevention of progression of latent to clinical infection.
Study CI VIP
Combined Vx & Chemoprophylaxis in TB
in non-vaccinated high-risk contacts
Case Control Measures of TB
Isolation of TB
chest hospital or at home
TTT of TB
DOTS
Release of TB
after complete cure with 3 negative sputum smears
Criteria of DOTS (Direct Observation Therapy with Short course chemotherapy)
Advantages of DOTS (Direct Observation Therapy with Short course chemotherapy)
Disadvantages of DOTS (Direct Observation Therapy with Short course chemotherapy)
High cost
Measures for the contacts of TB
