Mycobacterium

Mycobacterium

Acid –fast bacilli:

Mycobacterium  are aerobic acid –fast bacilli. They are neither gram –positive nor gram negative.

Classification  of Mycobacterium:

Mycobacteria  two types:

1. Pathogenic                                     2. Non pathogenic

     ↓                                                                 ↓

       Example:                                                    Example:

    M.tuberclosis                                            M. smegmatis

       M.leprae.                                                M. butyricum.

Mycobacterium  tuberculosis:

Habitat : they usually found in lung ,tonsil, intestine, genital tract.

Morphology of Mycobacterium  tuberculosis:

Shape                 : Straight or curved rods.

Size                    : 1.2.to 4 µm

Flagella              : Absent

Spore                 : Absent

Capsule             : Absent

Motility             : Non –motile.

Staining     : They are acid –fast bacilli (AFB) and resist decolourization .

Cultural character of Mycobacterium  tuberculosis:

1. The organisms are aerobic.
2. Optimum Ph : 7-7.6
3. Optimum temperature varies according to types e.g. human & bovine types:37°C,cold –blooded type : 25 °C ,M. unlearns & M. balnei: 30°C.

4. Cold –blooded type behaves as saprophytes . Human and bovine types require special media for growth.
5. Growth:
   
   -  Tissue culture media: tubercle bacilli grow around nuclei in the form of cord.-  Dubos media : Organism grow rapidly.- Lowenstein –Jensen media ; Colonies are dry, wrinkled and tenacious, at first colonies are white color & later on buff –colored.

Biochemical character:

1. They form acid but no gas.
2. It produces peroxides.
3. They can produce niacin

Diseases caused by M.tuberculosis:

TB of various site-

(a)    Pulmonary TB.

(b)   Intestine TB.

(c)    Bone TB.

(d)   Urogenital TB.