tb Flashcards
TUBERCULOSIS
Tuberculosis is a chronic infectious disease caused by Mycobacterium
tuberculosis
ETIOLOGY
M. tuberculosis, (the most important cause in
humans), M. bovis, M. africanum, M. microti and M.Canetti
MODE OF TRANSMISSION
4
- Inhalation: - pulmonary tuberculosis
o Infectious droplet nuclei can be spread into the air by:
▪ Coughing (single coughing Can produce 3000 droplet nuclei)
▪ Talking
▪ Sneezing
▪ Spitting and singing
o Most important source is smear positive coughing adult - Ingestion (raw milk): - intestinal Tuberculosis
- Wound contamination: - cutaneous tuberculosis
- Hematological spread form primary Tuberculosis focus
tb classification based on timr of infectionn
- Primary infection occurs in persons without previous exposure to tubercle
bacilli
A localized granulomatous inflammatory process occurs within the lung and this
is called
the PRIMARY (GHON) FOCUS
The Ghon focus with associated tuberculous lymphangitis and involvement of
the regional lymph nodes is called
the primary (Ghon) complex
…………… percent of persons infected with M. Tuberculosis, the immune system either
kills the bacilli or perhaps more often, keeps them suppressed (silent focus)
resulting in a latent TB infection (LTBI).
90-95
Active TB disease may arise from
o progression of the primary lesion after infection
o from endogenous reactivation of latent foci, which remained dormant
since the initial infection
o from exogenous re-infection
CLINICAL STAGES
exposure, infection, and disease
EXPOSURE MEANS
- A child has had significant contact with an adult or adolescent with infectious
tuberculosis but lacks proof of infection - In this stage, the tuberculin skin test (TST) or interferon-γ release assay (IGRA)
result is negative - The chest radiograph and physical examination is normal
- The child lacks signs or symptoms of disease
- However, the child may be infected and develop TB disease rapidly, since there
may not have been enough time for the TST or IGRA to turn positive
TUBERCULOSIS INFECTION (TBI):
- It occurs when the individual inhales droplet nuclei containing M. tuberculosis,
which survive intracellularly within the lung and associated lymphoid tissue - The hallmark of TBI is a positive TST or IGRA result
- In this stage the child has no signs or symptoms
- A normal physical examination, and the chest radiograph is either normal or
reveals only granuloma or calcifications in the lung parenchyma
DISEASE
- occurs when signs or symptoms or radiographic manifestations caused by M.
tuberculosis become apparent - Not all infected individuals have the same risk of developing disease
- An immunocompetent adult with untreated TBI has approximately a 5–10%
lifetime risk of developing disease An infected child <1 yr old has a 40% chance
of developing TB disease within 9 months
RISK FACTORS FOR TUBERCULOSIS INFECTION
- Children exposed to high-risk adults
- Foreign-born persons from high-prevalence countries
- Homeless persons
- Persons who inject drugs
- Present and former residents or employees of correctional institutions,
homeless shelters, and nursing homes - Healthcare workers caring for high-risk patients (if infection control is not
adequate
RISK FACTORS FOR PROGRESSION OF TUBERCULOSIS INFECTION TO
TUBERCULOSIS DISEASE
- Infants and children ≤4 yr old, especially those <2 yr old
- Adolescents and young adults
- Persons co-infected with human immunodeficiency virus
- Persons with skin test conversion in the past 1-2 yr
- Persons who are immunocompromised, especially in cases of malignancy and
solid-organ transplantation, - Immunosuppressive medical treatments including anti–tumor necrosis factor
therapies, diabetes mellitus, chronic renal failure, silicosis, and malnutrition
RISK FACTORS FOR DRUG-RESISTANT TUBERCULOSIS
- Personal or contact history of treatment for tuberculosis
- Contacts of patients with drug-resistant tuberculosis
- Birth or residence in a country with a high rate of drug resistance
- Poor response to standard therapy
- Positive sputum smears (acid-fast bacilli) or culture ≥2 months after initiating
appropriate therapy.
Time between initial infection and clinically apparent disease:
in every system
renal bone pulm. LN cns
- Disseminated and meningeal tuberculosis are early manifestations (2–6 months)
- Significant lymph node or endobronchial tuberculosis (within 3–9 months)
- Lesions of the bones and joints take several years to develop
- Renal lesions (decades after infection)
CLINICAL MANIFESTATIONS of primary pulm tb
Nonproductive cough and mild dyspnea are the most common symptom
pathophysiology of the clinical manifestations
As delayed-type hypersensitivity develops, the hilar lymph nodes continue to
enlarge in some children, especially infants, compressing the regional bronchus
and causing obstruction.
clinical manifestation of PROGRESSIVE PRIMARY PULMONARY DISEASE
(High fever, severe cough with sputum
production, weight loss, and night sweat )
- A rare but serious complication of tuberculosis in a child occurs when the
primary focus enlarges steadily and develops a large caseous center - Liquefaction can cause formation of a primary cavity associated with large
numbers of tubercle bacilli.
REACTIVATION TUBERCULOSIS types based in site
pulmonary
non pulmonary
REACTIVATION TUBERCULOSIS clinical mani
fever, anorexia,
malaise, weight loss, night sweats, productive cough, hemoptysis, and chest pain
PULMONARY TUBERCULOSIS define and symptoms
o Persistent cough for two or more weeks, (cough of any duration for HIV positives)
o Fever for more than 2 weeks
o Night sweats
o Unexplained weight loss
to any bacteriologically confirmed or clinically diagnosed case of TB
involving the lung parenchyma or the tracheobronchial tree.
