Pulmonary Tuberculosis

Pulmonary Tuberculosis Cheng Zhang ， Respiratory Medicine ， Affiliated Hospital of Jining Medicine college 23,Feb

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Tuberculosis(TB), a chronic bacterial infection(infectious) causes more deaths worldwide than any other infectious disease.TB is spread through the air and usually infects the lung(other organs are sometimes involved.some 2 billion people-one-third of the worlds population— are infected with the TB organism, Mycobacterium tuberculosis.

Epidemiology  Global 

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Worldwide ， tuberculosis is second only to HIV in causes of death by infectious disease among adults Many developng countries are suffering dual epidemics of TB and HIV 1/3 （ 2 billion ） have been infected 5% of infacted develop active disease during the the first years following exposure.

 Eight

million new cases each year and three million deaths  TB aptly bears the name“The Captain of all these Men of Death”

Epidemiology        

CHINA a. High infection rate(nearly half) b. High mobility rate c. High resistance rate(primary 18.6%,acquired 46.5%) d. A big death population(130 thousans cases died per year) e. More younger and middle-age population f. A big different mobility in different areas g. A low mobility

 Mycobacteria

belong to the family Mycobacteriaceae and the order Actinomycetales.The pathogenic species are the M. tuberculosis complex,the most frequent and important agent of human disease is M. tuberculosis,the others are M.bovis,M.africanum, and M. microti

Etiology the bionomics of mycobacterium tuberculosis (tubercle bacillus)

1. polymorphism 2. acid résistance 3. Grow slowly: 14~20h 4. Resistance: dry 、 cold 、 acid 、 base 5. constitution complicated ： adipoid 、 protein 、 polycose

 M.

tuberculosis is a rod-shaped ,non-sporeforming,thin aerobic bacterium measuring 0.5 μm by 3 μm.  Fast-acid stain can not decolorized with acid alcohol.

INTERPERSONAL SPREAD OF TUBERCULOSIS  SOURCE

OF INFECTION  The patient is the major source of infection.Tubercle bacilli are expelled into the air through respiratory secretion of patients with pulmonary tuberculosis.

Transmitting Routes  M.tuberculosis

is transmitted by airborne from person to person via the respiratory route.Inhalation of droplet nuclei contaning tubercle bacillus may cause infection.Transmitting by other ways such as digestive or skin is rare currently

Susceptible Population  The

factors that affect susceptibility to pulmonary tuberculosis include natural resistance and acquired specific resistance  The former:heritance ,poor life overcrowded living accommodations,malnutritious status,infants,old ages HIV infection,persons who take immunological suppressors are susceptible to tuberculosis.

Influential Factors Number of organisms in the expectorated sputum  extent of pulmonary disease,  frequency of cough,  duration of exposure,  Density of infected droplet nuclei,  adequate air ventilation,  Individural immunity status 

 About

one-third of the worlds population is infected with tuberculosis.However,most do not show signs of disease,bacteria are inactive (latent ) and can not transmitted to others.about 10 percent of people with the inactive form of the disease eventually will develop active tuberculosis.

PROGRESSION AND DEVELOPMENT  

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PRIMARY INFECTION In about 5 percent of people,the immune system can’t stop the initial tuberculosis infection These people develop active tuberculosis within one year of exposure to the bacteria This type of active tuberculosis is most common in infants and chidren

PROGRESSION AND DEVELOPMENT  

Primary pulmonary tuberculosis results from an initial infection with tubercle bacilli Infection ,primary infection presented as an infiltration lesion,follows if the inoculum escapes alveolar macrophage microbicidal activity,with the spreading of tubercle bacilli along intrapulmonary lymphatic ducts to hilar lymph node,the lymph nodes enlarged

PROGRESSION AND DEVELOPMENT 

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The lesion of primary infiltration,enlargement of tracheobronchial lymph node is called primary syndrome or primary tuberculosis Cell-mediated specific immunity plays a role in human body when invasive initially Primary infection represent the most common processes:(1) primary infection rapidly absorbed;(2)enlarged lymph nodes gradually smaller;(3)tubercle bacilli spreading to other organs killed

PROGRESSION AND DEVELOPMENT 

IMMUNITY AND DELAYED-TYPE HYPERSENSITIVITY

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Koch phenomenon:

Infection and reinfection: two experiment The first experiment: Inoculation some Bacillus tuberculosis at first

reaction

10~14 days later local flare

ulcer ， disunion regional nodes intumesce

Have no obvious

Bacillus tuberculosis multiplicity

to follow lymph node and blood circulation Spreading all over the body

cavia cobaya died (none

immunity ）

The second experiment: Inoculation the same dose Bacillus tuberculosis to the cavia cobaya (which have been inoculated 4-6weeks ago) Occurrence high fever ， 2-3days later ， local site: red swelling 、 ulcer 、 necrosis do not Spreading all over the body

Have some different reaction regional nodes have none intumesce Koch phenomenon

Secondary Tuberculosis  Tubercle

bacilli have the capacity to remain dormant,but viable,for long periods in health subjects.Where primary infection has healed spontaneously,a proportion of patients will continue to harbor (hide) organisms capable of causing disease in the future.

 Such

reactivation to cause secondary (postprimary) tuberculosis may occur in any organ,but it is most common in the lung.  Reactivation is more likely ito occur in patients with chronic disease causing general debility,such as alcoholism,malnutrition and diabetes mellitus,or with cellular imunodeficiency

 Secondary

TB results from endogenous recrudescence and exogenous reinfection.  ~presents obvious clinical symptoms, cavities and bacilli expelled ,and are infectious.A bad prognosis without treatment occurs in positive bacilli,which showa a half death rate will appear in 5 years

Pthology     

Basic pathological fingdings Inflammtory exdative response Proliferative response Caseous necrosis The lesions sometimes change from one type to another or are a composite of several.which depens on tuberculin sensitivity of the host and on the number of tubercle bacilli.

A

exudative mainly present local infiltration of neutrophils,and subsequently transformed to macrophages and lymphocytes.  B proliferation shows typically tubercle  ~ occurred with strong resistance and recover stage

C

caseous necrosis is described as caseous because it resembles cheese ,being rather homogeneous, yellow-white ,and rich in lips.~appear in the condition of presence of strong toxic tuberculous bacilli in a large number and of hypersensitivity with weak resistance

（二）

turnover

1 absorption 2 fibrosis 3 calcification 4 aggrevation

Clinical manifestation

Symptom:

1. general symptom(nonspecific,insidious) low-grade fever 、 debilitation 、 nightsweat 、 anorexia 、 emaciation(weight loss),general malaise,fatigue,headache

2.respiratory

system symptom

cough 、 expectoration Hemoptysis(mild,masssive) chest pain dyspnea(extensive disease)

Sign: quality and circumscription Inspection: respiratory movement attenuated Palpitation :increased fremitus(consolidation) percussion : dullness Auscultation: breath sound degrade Allergic manifestation:erythema nodosum rhochi,moist rales,effusion

Assistant examinations  Bacteriological

examinations(gold standard)  It also helps make regimen and check efficacy of chemotherapy

Collection of specimens  Freshly

expectorated sputum  Three consecutive morning sputum specimen  Sputum induction  Others(pleural effusion,bronchial brushings/biopsy/BAL

Direct examination  Confirmation

of tubercle bacilli  Demonstration of acid-fast bacilli on smear can illustrate the presence of anti-acid bacilli but can not identify M. tuberculosis and saprophytic nontuberculous mycobacteria

Culture and susceptibility test  Confirmation

of M.TB  Determination of susceptibility

Imaging   

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Diagnosis and evaluation Favour location:upper lobe (apical ,posterio segements),lower lobe (superior segement) Natures:small homogenous infiltrates,multinodular infiltration,cavity,satellite nodular lesions,fibrotic scarring more-foci,more-morphology,more-calcification Fewer-mass,fewer-cumulation,fewer-intensification

 CT

scan offer the evidence of fine or latent lesions,and detect the infected area and other confused disorders

PPD （ purified protein derivative ）： 　 0.1ml(5IU) ih

left forearm

48~72h measure induration (transverse diameter+ length wise diameter)/ ２

negative

≦ 4mm

weakly positive

5~9mm

positive

10~19mm

powerful positive≧20mm or <20mm blister and angiolymphitis

 The

tuberculin skin test identifies individuals who have been infected with M.tuberculosis but does not distinguish between M tuberculous infection and tuberculosis.  Both false-positive and false-negative tuberculin reactions occur

Types of pulmonary tuberculosis  A.

primary pulmonary tuberculosis(primary syndrome,intrathoracic lymphatic tuberculosis)  B hematogenous pulmonary tuberculosis(acute,subcute,chronic)  C postprimary or secondary pulmonary tuberculosis (infiltrative, chronic fibrocavitative and caseous pneumonitis)

D

tuberculous pleuritis(dry,exudative andtuberculous empyema)  E other extrapulmonary(genitourinary tract, bones,and joints, meninges, peritoneum,and pericardium)

diagnosis  Diagnostic      

methods exposing history clinical manifestations imagiological presentations bacteriologic findings pathological results tuberculin skin test and other methods

Differential diagnosis 1

pneumonia  2 bronchogenic carcinoma  3 lung abcess  4 bronchiectasis

chemotherapy  Principle:early,regular,full-

termed,adequate,and combined therapy  enhance cure rate,lessen recurrent rate ,provide safer ,avoid resistance

Biological mechanisms of chenmotherapy  Differences

in mycobacteria metabolic rate are associated with differences in susceptibility to anti tuberculosis. only actively replicating organism are killed by chenmotherapy.

 Group

A living extracellularly, metabolically very active, rapidly, continuously growing in a hyperoxic and neutral-pH environment. susceptible to SM,INH,EMB  Group B living extracellularly metabolically less or intermittently active in a hyoxic and neutral-pH environment. susceptible to RFP,INH

 Group

C living in the acid ,hypoxic environment of macrophages ,slow,intermittent growth.PZA and RPF are uniquely effective against these organisms and INH is less effective.  Group completely dormant unaffected by both antimicrobial and cellular immune mechanisms.

Antituberculous drugs A

isoniazid(INH)  Intra and extra cellular bacilli  INH should be used in all regimens except when a high proportion of INH-resiastant organisms are present  Intravenouslly,intramuscular nasogastric,oral

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Side effects (toxic manifestations) Peripheral neuritis(reversible,treated with pyridoxine toxic hepatitis(including allergic ) If enzymelevels rise above three times normal values Monthly monitoring of liver enzyme is recommended.

 Rifampin

(RFP)  Bactericidal against intra-extra cellular  Dose not pass the blood-brain barrier under normal conditions  Distributing well (urine, tears, sweat,and other body fluids,coloring them to redorange

 Major

side effects  gastrointestinal upset  heptic toxicity  Appearance pg jaundice is the signal og cessation of RFP,rifapentin is also available  INH and RFP together produce heptotoxicity more frequently than either drug alone

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C pyrazinamide (PZA) Nictinic acid derivative similar to isonazid,no cross-resistance with INH Effective against slowly metabolically intracellular bacilli, important one of short-course regimen Adverse reaction heptotoxicity ,hyperurecemia, rare side effects skin rash,gastrointestinal intolerance

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D ethambutol (EMB) Bacteriostatic agent(limited to M.TB) Active against both intra and extra cellular bacilli Main toxicity: optic neuritis Children are forbidden to administer EMB because of disbility to identify the visual symptom

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E streptomycin (SM) Effective only against extracellular bacterial First major antituberculous drug released SM must be administered parenterally ,because it is not absorbed from gut( usually intramuscular) Major toxicity irreversible eighth nerve damage leading to vestibular dysfunction and ,less frequently ,nephrotoxic

Dosage of common antituberculous drugs          

Isoniazid daily (INH) Rifapin RFP Pyrazinamide PZA Ethambutol EMB Streptomycin SM

dosage(g/d) 0.3 q.d 0.4 -0.6 q.d

intermittent 0.6-0.8 ,2-3/w 0.6-0.8 ,2-3/w

1.5-2.0 tid/qid

2.0-3.0,2-3/w

0.75-1.0 q.d

1.5-2.0,2-3/W

0.75-1.0 q.d im

0.75-1.02-3/w