lectures-5-6-mycobacterium tuberculosis, m. leprae, actinomycetes
TRANSCRIPT
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بسم الله الرحمن الرحيمبسم الله الرحمن الرحيم
GENUS: MYCOBACTERIUMProf. Khalifa Sifaw Ghenghesh
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Obligate aerobe, Gram-positive rods Acid fast Complex cell wall lipids
– include mycolic acids– protects vs. phagolysosomal components
Peptidoglycan, glycolipids – acid-fastness
Two major groups: – Slow growers:– Rapid growers:
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Mycrobacterium tuberculosis Mycrobacterium tuberculosis
Non-motile, Non-sporing, non-capsulate rods
Grows on several enriched culture media:– Lowenstein-Jensen medium:
Whole egg, Glycerol, Asparagine, Mineral salts, Malachite green
Mycobacterium bovis:
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Lowenstein-Jensen Plate Culture Inoculated with 15 Strains of Mycobacterium Species
Lowenstein-Jensen Plate Culture Inoculated with 15 Strains of Mycobacterium Species
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CULTURE CHARACTERISTICS CULTURE CHARACTERISTICS
On primary isolation: – visible growth after up to 8 weeks
Colonies: – Buff colour, dry bread crumb-like appearance – Growth is eugonic (M. bovis = dysgonic)
Growth temperature:– 35-37oC
Obligate aerobe--------------------------------------------------------------------------- Heat-sensitive Susceptible to alcohol, glutaraldehyde and
formaldehyde.
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Some differential characteristics of tuberculle bacilli causing human disease
Some differential characteristics of tuberculle bacilli causing human disease____________________________________________________
Species Atmospheric
preference Nitratase TCH Pyrazinamide
---------------------------------------------------------------------------------------
M. tuberculosis Aerobic + S S
M. bovis Microaerophilic -- R R
_______________________________________TCH = thiophen-2-carboxylic acid hydrazide
S = sensitive, R = resistant
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THE DISEASE THE DISEASE
Not highly contagious:– transmission with prolonged contact
between susceptible and active case–usually transmitted by airborne droplets,
must penetrate deep into respiratory tree
– infection can be via other routes:ingestion => infection through cervical
or mesenteric LN
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Virulence– Ability to Survive within Macrophages
Primary TuberculosisPost-Primary Tuberculosis
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Stages of Primary Tuberculosis in Childhood
----------------------------------------------------------------------------------------
Stage Time (from onset) Characteristics
----------------------------------------------------------------------------------------
1. 3-8 weeks Primary complex (PC) develops and tuberculin conversion occurs
2. 2-6 months Progressive healing of PC, possibility of pleural
effusion
3 6-12 months Possibility of miliary or meningeal tuberculosis
4 1-3 years Possibility of bone or joint tuberculosis
5 3-5 years Possibilty of genito-urinary or chronic skin tuberculosis
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Main differences between primary and post-primary
tuberculosis in the non-immunocompromised patients---------------------------------------------------------------------------------
Characteristics Primary Post-primary
---------------------------------------------------------------------------------Local lesion Small Large
Lymphatic involvement Yes Minimal
Cavity formation Rare Frequent
Tuberculin reactivity Negative (initially) Positive
Infectivity Uncommon Usual
(pulmonary cases)
Site Any part of lung Apical region
Local spread Uncommon Frequent
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TUBERCULIN TESTTUBERCULIN TEST
Tuberculin: a heat-concentrated filtrate of a broth in which tubercle bacilli had been grown.
Injection of tuberculin into the skin >>– Large, indurated reactions >>Post-Primary
Tuberculosis.– No induration >> Protective immunity
Purified Protein Derivatives (PPD):– Mantoux Method (Intracutaneous)– Heaf Method (Spring-loaded gun)– Tine Tests (Disposable single tests)
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Mycobacteria-Positive PPDMycobacteria-Positive PPD
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LABORATOY DIAGNOSIS LABORATOY DIAGNOSIS
1. Specimen:– Pulmonary tuberculosis: > Sputum, Bronchial
washings, Laryngeal swabs, and Early-morning gastric aspirates.
– Homogenized tissue biopsies.
– Examine after centrifugation: Deposits of CSF, Pleural fluid, Urine and other fluids
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2. Microscopy:– Ziehl-Neelsen Stain– Fluorescent dyes
3. Culture:– Decontamination: – Lowenstein Jensen medium
4. Nucleic Acid Methods:
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Mycobacterium tuberculosis sputum smear (Ziehl-Neelsen
stain)
Mycobacterium tuberculosis sputum smear (Ziehl-Neelsen
stain)
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Mycobacterium tuberculosis in a sputum smear (Ziehl-
Neelsen stain)
Mycobacterium tuberculosis in a sputum smear (Ziehl-
Neelsen stain)
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Mycobacteria - Auramine Stained and Viewed with Fluorescence Microscopy.
Acid Fast Bacilli Appear as Glowing Yellow Rods.
Mycobacteria - Auramine Stained and Viewed with Fluorescence Microscopy.
Acid Fast Bacilli Appear as Glowing Yellow Rods.
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Histopathology of Tuberculosis, Endometrium. Ziehl-Neelsen Stain.
Histopathology of Tuberculosis, Endometrium. Ziehl-Neelsen Stain.
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An anteroposterior X-ray of a patient diagnosed with advanced bilateral pulmonary
tuberculosis.
An anteroposterior X-ray of a patient diagnosed with advanced bilateral pulmonary
tuberculosis.
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TREATMENT TREATMENT
Chemotherapy Recommended by International Union againstTuberculosis and Lung Disease (examples)----------------------------------------------------------------------------------------------------------Intial phase Continuation Regimen(2 months) phase (4 months)Drug Drug----------------------------------------------------------------------------------------------------------HRZ HR StandardHRZ H3R3 Intermittent/ whenHRZ H2R2 supervision is indicatedHRZE HR When there is a highHRZS HR incidence of initial drug
resistance----------------------------------------------------------------------------------------------------------H=isoniazid, R=rifampicin, Z=pyrazinamide, E=ethambutol, S=streptomycin -
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EPIDEMIOLOGY EPIDEMIOLOGYTransmission:
– Open Pulmonary Tuberculosis
– Crowdness in homes and workplaces
Tuberculosis and AIDS
Tuberculosis in Developing Countries:
–Africa
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CONTROL CONTROL
Early Detection and Treatment of Open Cases
Reducing Overcrowding
Vaccination:– Bacille Calmette-Guerin (BCG)
– Not effective as control measure
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Mycobacterium leprae Mycobacterium lepraeLeprosy (Hansen's disease)
– A chronic intracellular infectious disease unique to man (with few exceptions). Usually not fatal.
Never been cultivated in vitroArmadillos:
– 1010 bacilli/gram of diseased tissue
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M. leprae can be grown in mouse foot pads or the nine-banded armadillo (picture).
M. leprae can be grown in mouse foot pads or the nine-banded armadillo (picture).
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PATHOGENESIS PATHOGENESIS
Schwan cell >> Nerve damage >> Anaesthesia and Muscle paralysis >> Gradual destruction of extremities
> Nasal bones and eyes
Immune reactions >>
–Severe and permanent nerve damage
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THE DISEASETHE DISEASE Manifestations of the disease depend on the
resistance of the host.
1. Tuberculoid: host is highly resistant, clinical abnormalities limited to a few peripheral nerves and adjacent skin areas, tuberculoid granuloma
2. Lepromatous: host lacks resistance, all tissues affected, foam cell granuloma
3. Borderline:
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The feet become subject to bone damage and deformity through
unnoticed wounds and infection. Serious infections can lead to
amputations.
The feet become subject to bone damage and deformity through
unnoticed wounds and infection. Serious infections can lead to
amputations.
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Victims of leprosy often suffer amputations of fingertips and toes due to unfelt trauma.
X-rays of different stages.
Victims of leprosy often suffer amputations of fingertips and toes due to unfelt trauma.
X-rays of different stages.
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Leprosy affects facial nerves > loss of blinking reflex of the eye > dryness, ulceration, and
blindness.
Leprosy affects facial nerves > loss of blinking reflex of the eye > dryness, ulceration, and
blindness.
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Lepromatous lesions on human backLepromatous lesions on human back
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LABORATORY DIAGNOSISLABORATORY DIAGNOSIS Histological Examination of Skin Biopsies Detection of Acid-Fast Bacilli:
– In Nasal Discharges
– Scrapings from Nasal Mucosa
– Slit-Skin SmearsSuperficial incisions in skin >>
Bacillary Index (BI):
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Bacillary Index (BI) 1+ 1-10 bacilli/100 fields 2+ 1-10 bacilli/10 fields 3+ 1-10 bacilli/ field 4+ 10-100 bacilli/ field 5+ 100-1000 bacilli/ field 6+ >1000 bacilli/ field
Morphological Index (MI):
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TREATMENTTREATMENT
WHO Recommendations for Multidrug Therapy-----------------------------------------------------------------------------------------------Type of Drug Dose Frequency TotalLeprosy (mg) Duration-----------------------------------------------------------------------------------------------Paucibacillary Rifampicin 600 Monthly, Superv. 6 months
Dapsone 100 Daily, unsuperv.
Multibacillary Rifampicin 600 Monthly, Superv. >2 yearsDapsone 100 Daily, Unsuperv.
300 Mothly, Superv.
Clofazimine {+50 Daily, Unsuperv.
-----------------------------------------------------------------------------------------------
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EPIDEMIOLOGYEPIDEMIOLOGY Transmission:
– Nasal secretions of patients with lepromatous leprosy.
Skin Test: Limited diagnostic value– Lepromins > boiled-bacilli rich lepromatous lesions– Leprosins > ultrasonicates of tissue-free bacilli from
lesions.
Two Types of Reaction:– Fernandez Reaction: sensitized individuals > 48h
(leprosin)
– Mitsuda Reaction: granulomatous swelling > ~3 weeks (lepromin)
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بسم الله الرحمن الرحيمبسم الله الرحمن الرحيمبسم الله الرحمن الرحيمبسم الله الرحمن الرحيم
ACTINOMYCETESACTINOMYCETES
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Gram +ve, Filaments that Break Up Into Bacillary and Coccoid Forms.
Non-Motile, Non-Sporing, Non-Capsulated.
Free Living >> Soil
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1. ACTINOMYCES SPECIES 1. ACTINOMYCES SPECIES
A. israelii– Actinomycosis >>
Chronic Granulomatous Infection.– Formation of Sulphur granules:
3 Forms: i. Cervicofacialii. Thoraciciii. Abdominal
Predisposing Factors: Trauma, Poor Oral Hygiene.
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A. israeliiGram stain showing diphtheroidal
rods and short branching filaments.
A. israeliiGram stain showing diphtheroidal
rods and short branching filaments.
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Actinomycosis-organisms aspirated from the lung. Long, tortuous and branching organisms can easily be visualized using silver stain. Sulfur granules not seen in aspirations.
Actinomycosis-organisms aspirated from the lung. Long, tortuous and branching organisms can easily be visualized using silver stain. Sulfur granules not seen in aspirations.
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LABORATORY DIAGNOSISLABORATORY DIAGNOSIS
i. Direct Examination:
Sputum, Pus, etc.. >> Examined for Granules
ii. Culture: Brain Heart Infusion Agar
TREATMENT– Penicillin >> Several Weeks
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Sulfur granule from human actinomycosis tissue section (hematoxylin and eosin stain).
Sulfur granule from human actinomycosis tissue section (hematoxylin and eosin stain).
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2. NOCARDIA SPECIES2. NOCARDIA SPECIES
N. asteroides– Nocardiosis.
Aerobic. Disease Begins as Pulmonary Infection > > 50% of Patients are Immunocompromised. Fatality Rate >>
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LABORATORY DIAGNOSISLABORATORY DIAGNOSIS
i. Direct Examination: Sputum, Skin Lesions, Tissue Biopsies or Surgical Material
>> Microscopically. Observe: G+ve, Multiple Branched and Beaded Filaments. > Partially Acid-Fast. ii. Culture: iii. Identification: Biochemically.
TREATMENT Sulphonamides, NA, TMP-SMX.
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Nocardia asteroidesSilver stain showing the twisted
masses of long filamentous organisms
Nocardia asteroidesSilver stain showing the twisted
masses of long filamentous organisms
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Nocardia asteroidesAcid fast stain shows the pale red staining organisms in an area of
necrosis
Nocardia asteroidesAcid fast stain shows the pale red staining organisms in an area of
necrosis
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Differences between the genera
Actinomyces and Nocardia
------------------------------------------------------------------Actinomyces species Nocardia species
------------------------------------------------------------------Facultative anaerobes Strict aerobes
Grow at 35-37oC Wide temp range of growth
Oral commensals Environmental saprophytes
Non-acid-fast mycelia Usually weakly acid-fast
Endogenous cause of Exogenous cause of disease
Disease
------------------------------------------------------------------