TB Flashcards
TB MO
Mycobacterium tuberculosis
Mode of transmission of TB
spread by the inhalation of
aerosolised droplet nuclei from other infected patients
Pathophysio of TB
1.inhaled MOs enter the alveoli
2.Recruitment of macrophages and lymphocytes
3.macrophages transform into epitheliod and langerhans cells
4.they accumulate with lymphocytes and from granuloma.
Ghon focus
Numerous granulomas aggregate to
form a primary lesion
color of the ghon focus
pale yellow, caseous granuloma
location of the ghon focus
characteristically situated in the periphery of the lung
Ghon focus
combination of the primary lesion
and regional lymph nodes
why are most ABx ineffective against TB
1.intrinsic resistance
2.slow growth and dormancy
3.lipid rich cell wall is impermeable to ABx
4.can survive within macrophages and resist phagocytic killing
function of catalase in MTB
resist oxidative injury
function of lipoarabinomannan
induce cytokines and resist oxidative injury
Primary pulmonary TB
infection in individuals lacking previous sensitization
location of MTB deposition in lungs
inhaled bacilli implant in the distal air spaces .lower part of upper lobe or upper part of lower lobe
Reparative processes of the body against MTB
encase the primary complex in a fibrous capsule, limiting the spread of bacilli
manifestations of primary TB infection
Usually asymptomatic , but small transient pleural effusion or erythema nodosum – both are
representative of hypersensitivity manifestations
main complication of primary TB
can erode into bronchial tree lead to acute
TB bronchopneumonia. And also erode into blood vessels leads to miliary TB
Primary TB disease Sx
- Lymphadenopathy: hilar (often
unilateral), paratracheal or
mediastinal - Collapse (especially right
middle lobe) - Consolidation (especially right
middle lobe) - Obstructive emphysema
- Cavitation (rare)
- Pleural effusion
- Miliary
- Meningitis
- Pericarditis
HSR in Primary TB
Erythema nodosum
Dactylitis
Conjunctivitis
Risk factors of TB
1.Extremes of age
2. 1st Gen immigrants of high- prevalence countries
3.Close contact
4.CXR evidence of self-healed TB
5.Smoking
6.Immunosuppression
7.Malignancy
8.DM
9.CKD
Cryptic TB
- Age over 60 years
- Intermittent low-grade pyrexia of unknown origin
- Unexplained weight loss, general debility (hepatosplenomegaly in
25–50%) - Normal chest X-ray
- Blood dyscrasias; leukaemoid reaction, pancytopenia
- Negative tuberculin skin test
- Confirmation by biopsy with granulomas and/or acid-fast bacilli in
liver or bone marrow
Auscultation findings of miliary TB
normal
Bone marrow involvement of miliary TB
Anemia, leucopenia
TB meningitis in miliary TB
headache
Post- primary TB
Due to reactivation of previous asymptomatic disease
MC location of post-primary TB
Apex of the upper lobe - oxygen tension favors the survival of aerobes
post- primary TB can occur in
when defenses are weakened
Old age
Pregnancy
Malnutrition
Steroids,immunosuppressive agents
DM, HIV
Lymphoma
clinical presentation of post- primary TB
- Cough
- Prolonged fever
- Haemoptysis
- Poorly resolving pneumonia
- Unexplained fever , night sweats
- Nonspecific symptoms - weight loss, anorexia
- Pleuritic pain
- Incidental finding on CXR
- Others – breathlessness, wheeze
Physical examination of Post-primary TB
- may be normal
- RS - pleural effusion, apical cavitation, consolidation
- General - fever, wasting, pallor
Extrapulmonary TB forms
Lymph node TB
TB pleural effusion
TB of upper airways
Skeletal TB- Pott’s disease
GUT TB
GI TB
TB meningitis
Miliary TB
Routine tests of TB
ESR
CRP
FBC
CXR
AFB
Mantoux
Gene XPert/TB- PCR
Gold- Quantiferon TB gold test
findings of Post- primary TB Ix
high ESR
High CRP
CXR- not confirmatory
Why is CXR not confirmatory in TB
cannot differentiate from healed and active lesions
normal CXR in TB excludes?
endobronchial tuberculosis, military
tuberculosis, HIV positive patients
sputum examination for AFB
D1- supervised sample, D2 -
patient brings an early morning sample, D3 – supervised second sample when the patient
returns
Dx TB
- Bacteriologically confirmed tuberculosis
o 2 sputum DS positive for AFB
o 1 sputum DS positive with CXR suggestive of pulmonary TB
o Culture positive TB
o WHO recommended Rapid diagnostic test positive- X Pert MTB/RIF+ - Clinically diagnosed tuberculosis
o Diagnosis on clinical features/ radiology/histology without bacteriological
confirmation
Mantoux Test
0.1ml of PPD solution is injected in the flexor aspect of the forearm, reading taken
after 48-72 hours .induration >10mm will confirm the disease
when to suspect TB
Suspect in a person who is having a persistent cough for > 3 weeks
Treatment category I in TB
New sputum positive TB
New smear- negative PTB w extensive pulmonary involvement
New cases of severe extra- pulmonary TB
Category I TB Intensive phase
2HRZE – Isoniazid(H), Rifampicin(R), Pyrazinamide(Z),
Ethambutol(E)
Category I TB continuation phase
4HR – Isoniazid(H), rifampicin(R)
What is given to reduce the risk of isoniazid induced neuropathy
Pyridoxine 10mg daily
Category II TB
Relapses
Treatment failure
Return after default treatment
Category II TB Intensive phase
2SHRZE + 1HRZE
Category II TB continuation phase
5HRE
Category III TB
Sputum negative pulmonary TB with limited parenchymal involvement
Extra-pulmonary TB
Category III Intensive Phase
2HRZ
Category III Continuation Phase
4HR
Category IV TB
chronic cases
Category IV TB intesive phase
Treatment w at least 3 new drugs which were not previously used
Category IV TB continuation phase
Treatment continued for 24 months
all patients should be referred to the
National TB program of the respiratory disease control program of the MOH for follow-up
patients of anti-TB treatment should be isolated for
two weeks
Patients for two months can be treated in
Welisara
what should be employed in the community
DOTS - direct observed treatment strategy
Isoniazid ADRS
Liver toxicity
Peripheral neuropathy
Mental Retardation
Incordination
Drug interaction-enzyme
inhibitor
Rifampicin ADRS
Liver toxicity
Orange discolouration of body
fluids
Skin rashes, thrombocytopenia
Oral contraceptive failure
Pyrazinamide ADRS
Liver toxicity,
Hyperuricaemia
Ethambutol ADRS
Optic neuritis
Doses of Anti- TB drugs
Isoniazid- 5mg/kg
Rifampicin - 10mg/kg
Pyrazinamide- 25mg/kg
Ethambutol - 15mg/kg
how to decide if it’s active or inactive TB
- Radiology not reliable
- High ESR alone does not suggest activity
- Clinical and microbiological
o Sputum smear +ve for AFB
o Symptoms
o Progression of CXR lesions
o New cavitations or fluid levels
o Response to therapeutic trial
ADRS of Streptomycin
Ototoxicity
Nephrotoxicity
miliary TB spreads by
blood
Symptoms of miliary TB
Nonspecific symptoms – fever, malaise, weight loss, cough, headache
Signs of miliary TB
Normal chest, hepatosplenomegaly, choroid tubercles
Ix findings of miliary TB
High ESR, pancytopenia, hyponatraemia, military mottling on CXR
Mantoux can be negative on miliary TB
True
Sputum DS is always positive in miliary TB
False (10% can be positive)
additional tests done on miliary TB
BM, CSF cultures
Mx of miliary TB
Treat on suspicion. Category I Drugs
besides category I drugs what else can be given for acutely ill miliary TB patients
steroids
atypical features are seen in …..HIV patients with TB
late HIV
atypical features seen in HIV patients with TB
o Extra-pulmonary involvement common
o Unusual or absent radiological features
o TST positive in <40%, often mildly (<5 mm)
Rx challenge in HIV patients with TB
drug resistance
Sx of Pleural effusion in TB
Insidious onset – low grade fever, general ill health, night sweats, pleuritic pain, dyspnoea
Ix findings in PE due to TB
High ESR, normal WCC, positive mantoux
Pleural fluid analysis in TB
o Straw coloured
o High protein content
o High lymphocyte count
o AFB is often negative
o M. tuberculosis culture positive in 30%
o ADA (Adenosine deaminase) may be positive
pleural biopsy in TB
caseating granuloma
Mx on PE due to TB
standard category 1 treatment, a short course of steroids may be given
Drug- resistant TB is most commonly seen in
More in HIV, Health care workers
MDR TB
resistant to both Isoniazid and Rifampicin
Extensive Drug Resistance(XDR) TB
-resistant to both isoniazid and Rifampicin with resistance to any
of the quinolones(such as levofloxacin or moxifloxacin) and atleast one of the second line injectable
drug- Kanamycin, Capreomycin, Amikacin
second line drugs used in TB
Quinolone-ofloxacin,ciprofloxacin
Aminoglycoside- Kanamycin, Amikacin, Capreomycin
Para amino salicylic acid-cicloserine, Ethiopromide
Macrolide- Clarithromycin, Azithromycin
