2. • The genus Mycobacterium consists of numerous species some of which are highly
infectious.
Generally, they are slender, slightly curved rods, non motile, poorly Gram stained
positive, acid fast and aerobic
Classification
• Classification into 2 major groups is based on rate and temperature of growth, and
pigmentation:
3. 1. Rapid growers and slow growers
2. Pigmented(chromogenic) and non-pigmented (non chromogenic).
The pigment is yellowish.
Rate of growth:
Most grow between 6 – 8 weeks. M.ulcerans is the slowest grower
4. Temp. of growth:
• Most species will grow at 35 – 370C,
• others may grow at lower or higher temperature e.g. M. chlonei and M. fortitum
grow at 30-32°C while M. xenopi can grow at 44°C.
5. Characteristics
• - Large, very weakly gram positive rods
• - Obligate aerobes, related to Actinomycetes
• - Catalase positive
• - Non spore forming
• - Non motile
• - very slow growing- slow generation time (14-15 hours), colonies appears by (2-
8 wks)
6.
7. Human Tuberculosis
• - Tuberculosis (TB) is the leading cause of death in the world.
• - Most people with TB infection have a positive reaction to the tuberculin skin
test (purified protein derivative).
• - Incubation period: 4-6 weeks.
The disease manifests with:
• low fever
• night sweating,
• headache,
8. • cough with expectoration,
• significant weight loss,
• fatigue and weakness).
• Source of infection: Tuberculous patients
9.
10. Route of infection:
• Respiratory TB; transmitted via Inhalation of airborne droplets.
• Extra-pulmonary TB; Ingestion of contaminated milk
Cell Wall Structure of M. tuberculosis:
• - It is unique among prokaryotes, and it is a major determinant of virulence for the
bacterium
11. The cell wall complex contains:
• - Peptidoglycan
• - Complex lipids (consists of three major components, mycolic acids, cord factor
& wax-D)
12. Stages of the Tuberculosis Disease
Exposure stage:
• The exposure stage of Tuberculosis (TB) is when a person is first infected with the
bacteria that cause the illness
Latent stage:
• The Latent stage of tuberculosis is a period when a person has been infected with
the bacteria Mycobacterium tuberculosis but has not yet developed any clinical
symptoms of the disease.
13. Last stage:
• In the last stage of TB, the patient will often experience symptoms such as chest
pain, a persistent cough, loss of appetite, night sweats, fatigue, and fever.
Recovery stage:
• The recovery stage of tuberculosis (TB) is the period of disease treatment during
which a patient’s symptoms decrease, and the infection is under control. During
this stage, the patient begins to feel better and may stop taking medication
