MycobacteriuMycobacteriumm

The only genus of Mycobacteriaceae under Actinomycetales.

Systematics

属放线菌目分枝杆菌科的菌属

classificationclassification groupsgroups

M. tuberculosis complexM. tuberculosis complex

Non-tuberculous mycobacteria group Non-tuberculous mycobacteria group II

Non-tuberculous mycobacteria group ⅡNon-tuberculous mycobacteria group Ⅱ

Non-tuberculoustuberculous mycobacteria Non-tuberculoustuberculous mycobacteria

group Ⅲgroup Ⅲ

Rapidly growingRapidly growing Non-tuberculous mycobacteria group ⅣNon-tuberculous mycobacteria group Ⅳ

unknownunknown Mycobacterium leprae

Classification

According to the Classification program of International Working Group on Mycobacterial Taxonomy[tæk'sɑːnəmi]

Slow

ly grow

ing

1 ． Slender or slightly curved bacilli ， Branch-like

arrangement or gathered in small clumps.

2 ． G+ ， but difficult to stain, enlongation the dyeing time or

Improve the dyeing temperature, they can be stained, and

once stained they cannot decolorized by acid-alcohol.

3 ． The cell wall contains large amount of lipid, which is highly

related to their staining characterisctics, resistance and

pathogenesis

4 ． Except capsule, no other special structure, no endotoxin and

exotoxin.

Common characters

Mycobacterium tuberculosis Mycobacterium tuberculosis

(Tubercle ['tuːbəkl] (Tubercle ['tuːbəkl] Bacilli)Bacilli)

☆ Koch discovered the tuberculosis

pathogen in 1882

☆ In 1886, tuberculosis pathogen was

named Mycobacterium tuberculosis by

Lenmann and Nenmann.

1. an ancient infectous disease, and it is also an important

infectious diseases in developing countries nowadays.

2. 1/3 of the worldwide population are infected with the

tubercle bacillitubercle bacilli, and 70% of these infected persons are in

Asia.

In China before liberation, the mortality rate in TB

patients ranks first in the various cause of death

3. WHO reported that sixty-five million people are infected

with mycobacterium tuberculosis every year. The global TB

incidence rate has an average annual increase of 0.4%.

Prevalence of TB

▲ AIDS, drug abuse, alcoholism, poverty.

▲ The flow of high-risk groups, the increase of immigrants

and refugees.

▲ Drug-resistant strains, especially the emergence and

prevalence of multi-resistant strains.

▲ Not standardized in Prophylaxis [ˌprɑːfɪ'læksɪs] and

treatment.

▲ The administration of immunosuppressive agents.

Reasons for recovery of TB Incidence:

In April 1993, the World Health Organization promote

the "global TB state of emergency Declaration"

March, 24 of each year was determined as “World TB

Day” in 1995

Acid-fast bacilli

Morphology

■ pink in a contrasting

background.

■ slim and pleomorphic

rods.

■ non-motile

■ capsulate

■ arranged singly or in

small clumps in clinical

specimens, but it form

“serpentine ['sɜːrpəntiːn]cords” in

pure culture.

Cultural characters

Obligate, high nutritional requirement, grow slowly,

rough colony

Greedy: can only grow in medium containing serum, egg yolk,

potato flour, glycerol ['glɪsəˌroʊl] , asparagine

[ə'spærəˌdʒiːn] 天门冬酰胺 and some inorganic salt

(lowenstein-jensen medium) (Malachite ['mæləkaɪt]green is

added to inhibit the growth of gram positive bacteria)

Reasons for slow growth:

▲ Strong hydrophobic of the lipid-enriched cell wall, the

permeability of nutrients into the cell is inhibited.

▲ Deficiency of DNA-dependent RNA polymerase

▲ Lack of oxygen

Lazy: grow slowly. The double time is about 15 ～ 18 hours.

The dry, rough, buff-colored colonies usually appear

after 3-6 weeks of incubation.

Colonies of M.tuberculosis on Lowenstein-Jensen medium

Ugly: dry, rough, small and buff colored colonies after 4 ～ 6

weeks of incubation.

Cauliflower

Eight Week Growth of Mycobacterium tuberculosis on

Lowenstein-Jensen Agar

●Resistant to

※ Dry: it can survive for long period in dried sputum.

※ Acid and alkali ['ælkəlaɪ]: they can be used to eliminate

contaminating organisms and for the “concentration”of M.

tuberculosis in clinical specimens.

※ Basic dyestuff: they can be used as a selective substance in

Lowenstein-Jensen medium.

※ Routine used antibiotics, such as penicillin

Resistance

● Sensitive to

※ Liposoluble disinfectant such as ethanol

※ Humid heat, so pasteurization can kill them.

※ Ultraviolet light, Bedclothes can be Disinfected by solarization

or ultraviolet radiation.

※ Antituberculotics such as streptomycin, isoniazid 异烟肼 ,

rifampicin [raɪ'fæmpəsɪn], etc.

Variability

13y230gspecial medium

Morphology variation

Virulence variation

Resistence variation drugs

Bacterial L-form( 29.9％ -45.5%)

Chronic patient(poor prognosis)

Routine examination (-)

Endogenous infection

Poisonous

attenuated

PathogenesisPathogenesis

Lipid

mycolic acid phospholipid Wax D sulfatide [sʌlfeɪ'taɪd]

chemotaxis to monocytes granuloma destroy membrane of mitochondria

hyperplasia of monocytes

macrophages are tranformed into epithelioid cell

adjuvant （Type IV hypersensitivity ）

inhibit phagocytes

Protein PPD （ Type IV hypersensitivity ）

polysachride help entry ;Anti-Phagocytic effects

Lipid-Rich Cell Wall of MycobacteriumMycolic acids

CMN Group: Unusual cell wall lipids (mycolic acids,etc.)

(Purified Protein Derivative)

[æræbɪnɒɡəlæk'tæn]阿拉伯半乳聚糖

[maɪkə'leɪt]霉菌酸酯

Diagram of a Granuloma

NOTE: ultimately a fibrin layer develops around granuloma (fibrosis), further “walling off” the lesion.

Typical progression in pulmonary TB involves caseation[ˌkeɪsiː'eɪʃən] 酪化作用 , calcification and cavity formation.

TransmissionTransmission

※ ※ Through Through respiratory tract, alimentary [ælɪ'mentərɪ] respiratory tract, alimentary [ælɪ'mentərɪ] 消消

化的化的 tract, injured skin.tract, injured skin.

※ ※ TB in the lungs or throat can be infectious. This means TB in the lungs or throat can be infectious. This means

that the bacteria can be spread to other people. TB in that the bacteria can be spread to other people. TB in

other parts of the body, such as the kidney or spine, is other parts of the body, such as the kidney or spine, is

usually not infectious.usually not infectious.

※※ Spread by droplet nuclei (coughs, sneezes, speaks, or

sings).

PathogenesisPathogenesis

10% of infected persons with normal immune

systems develop TB at some point in life

HIV is the strongest risk factor for development

of TB if infected

Certain medical conditions increase risk that

TB infection will progress to TB disease

Pathogenesis

Conditions That Increase the Risk of Progression to TB Disease

※ HIV infection

※ Substance abuse

※ Recent infection

※ Chest radiograph findings suggestive of previous TB

※ Diabetes mellitus

※ Silicosis

※ Prolonged corticosteriod therapy

※ Other immunosuppressive therapy

Conditions That Increase the Risk of Progression to TB Disease

※ Cancer of the head and neck

※ End-stage renal disease

※ Intestinal bypass or gastrectomy [gæs'trektəmɪ] 胃切除术

※ Chronic malabsorption syndromes

※ Low body weight (10% or more below)

1) Lung infection1) Lung infection

2) Out lung infection2) Out lung infection

primary infectionprimary infection

secondary infectionsecondary infection

Pathogenesis

Common Sites of TB Disease

•Lung （ the most common site ）•Pleura

•Central nervous system

•Lymphatic system

•Genitourinary systems

•Bones and joints

•Disseminated or miliary['mɪlɪˌerɪ] 栗粒状的 TB

Mycobacterium tuberculosisMycobacterium tuberculosis can infect (disseminate) and

cause disease in many different body locations such as:

Symptoms of Pulmonary TB

※ Productive, prolonged cough (duration of >=3 weeks)

※ Chest pain

※ Hemoptysis [hɪ'mɒptəsɪs] 咳血

Systemic Symptoms of TB

※ Fever

※ Chills

※ Night sweats

※ Appetite loss

※ Weight loss

※ Easy

※ fatigability[fætɪgə'bɪlətɪ]

Primary TuberculosisPrimary Tuberculosis

TB alveolus [æl'vi l s]ːə ə

engulf

multiplication porta pulmonis lymph nodes

destroy macrophages

inflammation

lymph

lymphangitis[l mf n'd a t s]ɪ ə ʒ ɪ ɪlymphadenitis[l m fæd 'na t s]ɪ ɪ ɪ ɪˌ

primary malignant syndrome

tubercle /caseous necrosis

recovery dissemination

Sencondary TuberculosisSencondary Tuberculosis

endogenous TB

Multiplication

low immunity

exogenous TB

Caseous necrosis

Open pulmonary tuberculosis

Macrophages containing TB bacilli clump together and begin to form tubercles. (granulomatousresponse)

With time, the centers of the tubercles become necrotic and form cheesy acellular masses of caseous materials. (caseous lesion)

Activation of macrophages -> cytokine secretion, IL-1: fever;tNF: lipid metabolism, weight loss, tissue necrosis;Oxygen radicals: tissue damagesTissue necrosis -> inflammation -> mucous secretion, destruction of blood vessels -> frequent cough and bloody sputum

PULMONARY TUBERCULOSISPULMONARY TUBERCULOSIS

Large caseating tubercle Miliary tubercles

HUMAN LUNGHUMAN LUNG HUMAN LUNGHUMAN LUNG

TUBERCULOSISTUBERCULOSIS

immunity

1 ． Infection immunity.

2 ． Cellular immunity plays an important role in Anti-TB

immunity .

3 ． Specific antibody can only kill extracellular tubercle

bacillus, specific antibody has no killing effect on the

intracellular bacteria

4 ． Immunity and hypersensitivity is co-exit.

Previous infection with TBor immunized Guinea pigs

Guinea pigs

24-48 hrs10-14d

Local swelling, shadow ulceration

Local swelling, ulceration

Recovery

necrosis

Toxic TB

Dissemination

subcutaneous injection

Koch's postulate ['pɑ st le t]ː ʃə ɪ

Tuberculin Skin TestTuberculin Skin Test Testing for TB Disease and Infection

※ ※ Tuberculin is a mixture known as purified protein derivatives Tuberculin is a mixture known as purified protein derivatives

(PPD) from TB bacilli. (PPD) from TB bacilli.

※ ※ It is a test for delayed type hypersensitivity. Positive reaction, It is a test for delayed type hypersensitivity. Positive reaction,

reddening and thickening (> 5mm) at the site of injection after reddening and thickening (> 5mm) at the site of injection after

2-3 days2-3 days, indicates cellular immunity to tubercle bacilli., indicates cellular immunity to tubercle bacilli.

Tuberculin skin test

Intradermal injection of PPD

Reading the Tuberculin Skin Test

•Read reaction 48-72 hours after injection

•Measure the induration only

•Record the reaction in millimeters

The lesion is The lesion is

characterized by characterized by

erythema erythema

(redness) , (redness) ,

swelling and swelling and

induration (raised induration (raised

and hard).and hard).

＜＜ 5 mm5 mm negativenegative

5-15 mm5-15 mm positivepositive

≥≥15 mm15 mm Strong positiveStrong positive

Interpretive standard of Tuberculin Skin Test

Classifying the Tuberculin Reaction

>=5 mm is classified as positive in

※ HIV-positive persons

※ Recent contacts of TB case

※ Persons with fibrotic changes on chest radiograph consistent

with old healed TB

※ Patients with organ transplants and other immunosuppressed

patients

Classifying the Tuberculin Reaction

>=10 mm is classified as positive in

※ Recent arrivals from high-prevalence countries

※ Injection drug users

※ Residents and employees of high-risk congregate settings

※ Mycobacteriology laboratory personnel

※ Persons with clinical conditions that place them at high risk

※ Children and adolescents exposed to adults in high-risk

categories

Factors that May Affect the Skin Test Reaction

Type of Reaction Possible Cause

False-positive Infected with Nontuberculous mycobacteria

BCG vaccination

Anergy

False-negative Recent TB infection

Very young age (< 6 months)

Live-virus vaccination

Overwhelming TB disease

※ Do not rule out diagnosis based on negative skin test result

※ Consider anergy in persons with no reaction if

—HIV infected

—Overwhelming TB disease

—Severe or febrile illness

—Viral infections

—Live-virus vaccinations

—Immunosuppressive therapy.

※ Anergy skin testing no longer routinely recommended

Anergy

TreatmentTreatment

※ ※ multiple drugsmultiple drugs

※ ※ usually lasts from 6-9 months. usually lasts from 6-9 months.

△ △ rifampin (RIF) rifampin (RIF)

△ △ isoniazid (INH), isoniazid (INH),

△ △ pyrazinamide (PZA,pyrazinamide (PZA, 吡嗪酰胺 ) [pɪrə'zɪnəmaɪd]) [pɪrə'zɪnəmaɪd]

△ △ ethambutol (EMB,ethambutol (EMB, 乙胺丁醇 ) [eθ'æmbjʊtɒl) [eθ'æmbjʊtɒl

△ △ streptomycin (SM)streptomycin (SM)

※ Provide safest, most effective therapy in shortest time

※ Multiple drugs to which the organisms are susceptible

※ Never add single drug to failing regimen

※ Ensure adherence to therapy

Basic Principles of Treatment

Infectiousness

Patients should be considered infectious if they

▲ Are coughing

▲ Are undergoing cough-inducing or aerosol-generating

procedures

▲ Have sputum smears positive for acid-fast bacilli and they

▲ Are not receiving therapy, or

▲ Have just started therapy, or

▲ Have poor clinical response to therapy.

※ ※ vaccine against M.TB. :vaccine against M.TB. :

BCGBCG ( (Bacillus Calmette–Guérin ))

※ ※ BCG consists of a live attenuated strain derived from BCG consists of a live attenuated strain derived from

Mycobacterium bovisMycobacterium bovis. This strain of . This strain of MycobacteriumMycobacterium

has remained avirulent for over 60 years.has remained avirulent for over 60 years.

PreventionPrevention

BCG is not adapt to anyone, contraindicated in persons with impaired immune response from

BCG Contraindications

※ HIV infection

※ Congenital immunodeficiency

※ Leukemia

※ Lymphoma [lɪm'foʊmə]

※ Generalized malignancy

※ Receiving high-dose steroid therapy

※ Receiving alkylating ['ælkəˌleɪt] agents

※ Receiving antimetabolites [æn'tɪmtæbəlaɪts]

※ Receiving radiation therapy

Exercises

BCG BCG Tuberculin Skin TestTuberculin Skin Test Mycobacterium Mycobacterium

1.The biological characteristics and pathogeni1.The biological characteristics and pathogenicity of M. tuberculosis?city of M. tuberculosis?

2.The immunity of M. tuberculosis?2.The immunity of M. tuberculosis?