Page 1 of 3
Systematic Bacteriology
Lec.(5)
Genus: Mycobacterium
Mycobacterium is slender, straight or slightly curved non motile rods non
capsulated, none sporing and is aerobic bacilli. They don’t stain easily but
once stain they resist decolorization with mineral acids. They are therefore
referred to as acid fast bacilli (AFB). They are comprised obligate pathogens,
opportunistic and saprophytes.
Mycobacterium of clinical importance




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M. tuberculosis
M. africanum
M. bovis
M. leprae
M. ulcerance
Habitat and mode of transmission
 M. bovis is found mainly as pathogenic in cattle human become
infected by close contact with infected cattle
 M. tuberculosis is found in human transmitted to other person by
inhaling cough droplets or dust particle contain tubercle bacilli and
transmitted to animal that in close association with man also being
reported.
Pathogenicity:
 Tuberculosis:
After inhaling infected droplets the tubercle bacilli become lodged in the lung
forming small inflammatory lesion.
Activated macrophage form granuloma around the site of primary
infection which usually limits it (self- healing).
Pulmonary Tuberculosis

:
This occurs when the primary infection does not heal completely and
there is continued multiplication or reactivation of organism in the lung
several months or years later due to poor health, malnutrition or defective
immune response.
An inflammatory reaction leads to a liquefied destruction of lung tissue
(formation of a cavity).
DR.YAGOUB HAMADT ALLAH
1
ALBAH UNIVERSITY
Page 2 of 3
Systematic Bacteriology
Lec.(5)
Bacilli multiply in the wall of the cavity and can be found in the sputum
(infectious stage)
Patients with advanced infection have difficulty in breathing due to
cavities in their lungs.
Symptoms are include chronic cough, production of mucopurulent sputum
which may contain blood in the late stages of the disease there is loss of
weight, fever, night sweats, fatigue, chest pain and anemia later lung
collapse.
Tuberculosis meningitis:

Occur more frequently in non-immune infants and young children as a
complication of primary tuberculosis
The condition is often fatal unless treated at an early stage
Renal & urogenital Tuberculosis:
 Bone & joint Tuberculosis:
 Miliary Tuberculosis:
Diagnosis:
Caution:

 M. tuberculosis is a highly infectious pathogen (hazard group 3) we
can safety cabinet
 Minimize the creation of aerosols
 Lab must be well ventilated
 Smear made by wooden stick which can be easily discarded and
incinerated after use.
Specimens:
Sputum in screw-cap leak proof specimen container (must be sputum
not a saliva), or urine and pus.
Microscopy:
By Ziehl Neelsen staining. Concentrating of AFB in sputum by
centrifugation significantly increases the sensitivity of direct microscopy
Fluorescence microscopy (fluoro-chrome stain)
Culture:
DR.YAGOUB HAMADT ALLAH
2
ALBAH UNIVERSITY
Page 3 of 3
Systematic Bacteriology
Lec.(5)
Specimens such as sputum, urine and pus which are contain commensals
require decontamination before being cultured (for routine purpose sodium
hydroxide has been found to be an effective decontamination.
M. tuberculosis will grow aerobically on a protein enriched media e.g
Lowenstein – Jensen egg media (slow growing produce raised, dry cream
colored colonies 2-3 weeks but culture should be incubated for up to 6
weeks before being discarded
Identification based on
 Z N stain
 Rate of growth
 Temperature of growth
 Production of pigments
 Tuberculin test
 Mantoux test
Antibiotics:
Antibiotic effective for treatment of tuberculosis include isonizid,
streptomycin, p-aminosalicylic acid and rifampcin
Control:
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Adequate nutrition
Well ventilated house
General health education
Immunoprophylaxis is achieved by BCG vaccination
DR.YAGOUB HAMADT ALLAH
3
ALBAH UNIVERSITY