Mycobacterium tuberculosis-importance of TB day,classification of Mycobacterium species,Details on Mycobacterium tuberculosis-morphology,culture,resistance,biochemical reactions,antigenic characters,mode of transmission,pathogenesis,complications,lab diagnosis,treatment,DOTS Strategy and prophylaxis
2. IMPORTANCE OF TB DAY
Tuberculosis is a bacterial disease caused by the
bacteria MYCOBACTERIUM TUBERCULOSIS
TB day is celebrated to raise the common public health
awareness about the epidemic disease of tuberculosis
its causes,prevention ,and cure ,as well as the efforts
done inorder to totally eradicate this disease.
As around world 1.7 million of the people are dying of
this disease every year.
Timely TB identification and treatment are essential
for succesful recovery
3. MYCOBACTERIA
Mycobacteria are acid fast bacilli
They do not stain readly,but once stained they resist
decolorisation due to the presence of mycolic acid in
the cell wall.so they are called as acid fast bacilli
They appear in filamentous form like fungi,hence
called as Mycobacteria
They are Obligate aerobes growing most successfully
in tissues with a high oxygen content, mainly in the
lungs
5. Classification of Mycobacteria
1.Obligate pathogen
Mycobacterium
tuberculosis complex
a. M.tuberculosis
b. M.bovis
c. M.africanum
d. M.leprae
2.Oppertunistic
pathogens
a. Atypical mycobacteria
-M.kansai
-M.avium
6.
7. MORPHOLOGY
Straight, slightly curved
Acid fast Rod shaped 3 x
0.3microns size
Gram reaction is positive
May be single, in pairs or
in small clumps
Non motile
Non sporing,Non
capsulated
8. MTB : Cultural characters
MTB - Obligate aerobe
Grow slowly. Generation
time 14-15 hrs
Colonies appear after 2
weeks or at 6-8 weeks
Grows at 370c
Ph between 6.4 to 7.0
Addition of 0.5%glycerol
improves its growth.
9. Nature of Media Used
Helps the growth needs
Solid Medium is
commonly used.
SOLID MEDIA
1. Lowenstein Jensen’s
medium,Petrangini,Do
rset[contain egg]
2. Tarshis media [blood]
3. Loeffler[serum]
4. Pawlosky[potato]
Most commonly used
is
Lowenstein Jensen’s
Medium
Contain coagulated egg
Mineral salt solution
Asparagine's
Malachite
green[selective agent]
11. On L J Medium
M.tuberculosis appear
dry, rough raised
irregular colonies
Appear wrinkled
They appear creamy
white
Become yellowish
12. ON LIQUID MEDIA
Growth begins at the
bottom,creeps up sides
and forms
prominantsurface
pellicle formation
13. Resistance of Mycobacterium
Mycobacterium are
killed at 600c in 15 – 20
mt
In sputum they survive
for 20 – 30hours
Relatively resistant to
several chemicals
including Phenol 5 %
Sensitive to
Glutaraldehyde and
Formaldehyde
Bacilli survive in
Droplets for 8 – 10 days
14. Biochemical Tests on
Mycobacterium spp
Niacin test – positive for Mycobacterium
Aryl sulphatase test – Negative
Neutral red test-Positive
Catalase and peroxidase test – Differentiates Atypical
from Typical
Most Atypical are strongly Catalase positive
Tubercle bacilli are weakly positive
Tubercle bacilli are peroxidase positive – not atypical
• Nitrate reduction test-Positive
15. Antigenic Characters
Group specificity due to Polysaccharides
Type specificity to protein antigens
Delayed hypersensitivity to proteins
16. How tuberculosisspreads
Tuberculosis (TB) is a contagious disease.
Source of Infection – Open case of Pulmonary
Tuberculosis.
Coughing , Sneezing, or Talking.
Each act can spill 3000 infective nuclei in the air,
Infective particles are engulfed by Alveolar
Macrophages.
19. Generation of Droplet Nuclei
One cough produces 500
droplets
The average TB patient
generates 75,000
droplets per day before
therapy
This falls to 25 infectious
droplets per day within
two weeks of effective
therapy
26. Mechanisms of Infection
Mycobacterium do not produce toxins.
Allergy and Immunity plays the major role.
Only 1/10 of the infected will get disease.
Cell Mediated Immunity plays a crucial role.
Humoral Immunity – not Important.
CD4 Cell plays role in Immune Mechanisms.
27. Lesion –known as Tubercle
Tubercle is a Avascular granuloma Contain central
zone of giant cells with or without caseation and
peripheral zone of Lymphocytes and Fibroblasts.
Produce lesions may be
Exudative or Productive
32. Clinical Illness with Tuberculosis
Pulmonary Disease – Major manifestation with
involvement of Lungs
Hemoptysis, Chest pain Fever sweets
Anorexia
Cavity formation in Lungs
33. Complication of Tuberculosis.
1. Meningitis.
2. Pleurisy,
3. Involvement of Kidney,
4. Spine ( Potts spine )
5. Bone Joints,
6. Miliary tuberculosis
38. Concentration of specimens
When AFB not concentrated by direct microscopy
then specimens are concentrated by different
techniques.2methods are there
1.petroff’s method 2.modified petroff’s
1.petroff’s method-- equal volumes of sputum sample
and 4%sodium hydroxide are mixed incubated at 370c
for 20-30 minutes and sediment used for microscopy
and culture.
39. MICROSCOPY
1- Sputum smears stained by Z-N stain
Three morning successive mucopurulent
sputum samples are needed to diagnose
pulmonary TB.
Advantage: - cheap – rapid
- Easy to perform
- High predictive value > 90%
- Specificity of 98%
Disadvantages:
- sputum ( need to contain 5000-10000 AFB/ ml.)
- Young children, elderly & HIV infected persons
may not produce cavities & sputum containing AFB.
40. GRADING BY RNTCP
Number of bacilli observed Grade
ZERO --
1-2bacilli/300fields --
1-9bacilli/100field --
1-9bacilli/10field --
-
1-9bacilli/field --
>9bacilli/field --
Negative
Positive
1+
2+
• 3+
• 4+
41. 2- Detecting AFB by
fluorochrome stain using
fluorescence microscopy
:
The smear may be stained by aura mine-O dye. In this method the
TB bacilli are stained yellow against dark background & easily
visualized using florescent microscope.
Advantages:
- More sensitive
- Rapid
Disadvantages:
- Hazards of dye toxicity
- more expensive
- must be confirmed by Z-N stain
44. Tuberculin Test[mantoux test]
It is typeIV hypersensitivity reaction
Purified protein derivative is inoculated intradermally
on forearm
Site observed after 72hrs for appearance of area of
erythema and induration
About 10mm indicate positive test
Below 5mm indicate negative
Between 5&9 mm indicates doubtful test
45. Recent Methods for Diagnosis
I – BACTEC 460 ( rapid radiometric culture
system )
specimens are cultured in a liquid medium (Middle brook7H9
broth base )containing C14 – labeled palmitic acid & PANTA
antibiotic mixture.
Growing mycobacteria utilize the acid, releasing radioactive
CO2 which is measured as growth index (GI) in the BACTEC
instrument.
The daily increase in GI output is directly proportional to the
rate & amount of growth in the medium.
54. ANIMAL INOCULATION
The conc.sample is inoculated intra muscularily into
the thigh of 2 healthy Guinea pigs about 12 wks old.
The animals are weighed b4 inoculation and intervels
thereafter
Progressive loss of weight is an indication of the
infection
Positive animal will show a caseous lesion at the site of
inoculation.
55. Treatment
Drugs used :
1- First line drugs :
- Isoniazid - Rifampicin - Pyrazinamide
- Ethambutol - Streptomycin
2- Second line drugs (more toxic and less effective):
- Kanamycin - capreomycin - Cycloserin
- ethionamide - ciprofloxacin - Ofloxacin
Mycobacteria develops drug resistance.Reason for this is –
improper prescription,delayed initiation of effective
therapy.and HIV infections
56. So as a control measure DOTS
strategy becomes important
DOTS-Directly Observed
Treatment Short course
‘This ensures that,the patient takes
medicines regularly untill they are
cured’-during the intensive phase a
health worker watches the patient
taking drug in his or her presence.
57. 5 ELEMENTS OF DOTS ARE
1. Government commitment
2. Case detection through quality assured bacteriology
3. Standardised treatment with patient support and
supervision
4. An effective drug supply and management system
5. Monitoring and evaluation system
58. Immuno-prophylaxis
BCG
Intradermal injection of live attenuated vaccine Bacille
Calmette-Guerin (BCG).
The strain causes self limited lesion and induces
hypersensitivity & immunity.
Immunity lasts for 10-15 years. Immunity 60-80%
Some studies proved BCG is doubtful value in
prevention of Tuberculosis