A content writing Blog is covering topic Mycobacterium tuberculosis, it includes general features, pathogenesis, lab diagnosis and treatment of tuberculosis. You will also aware about the facts about Mycobacterium tuberculosis.

1. FACTS ABOUT MYCOBACTERIUM
TUBERCULOSIS 17 MAY 2022
1. According to Global Tuberculosis report of world health organization (WHO)
estimated 1.5 million people died from tuberculosis (TB) globally in 2020, latest
global TB report 2021 released on 14 Octaccording to this report India accounted
for 41% of total global drop of 1.3 million cases.
- In 2019 7.1 million cases globally reported
- In 2020 5.8 million cases globally reported by WHO
2. You can imagine how one breath can make you sick like we all have faced fear
of Corona Virus ,tuberculosis is also a infectious disease spread by air transmission
from people with active pulmonary TB.
3. Need to be conscious about your Immune system, because people with
weakened immune system have a much greater risk of falling ill from TB.

2. 4. A personliving with HIV is about 20 times more likely to develop active TB.
5. About 1/3 population of the world is infected with tuberculosis but latently, they
have no symptoms.
6. Only small proportionof those infected will become sick with TB have
symptoms of severe cough, fever, night sweat, weight loss, fatigue and loss of
appetite.

3. 7. This is also one of the reasons why HIV is severe having TB ,which induced the
immune system it leads to the activation of T cells, in turn produce more
HIV virions than quiescent T cells.
8. Few little efforts can stop the spread of TB like -
- Always cover the mouth and nose when sneezing or coughing.
- Do not spit on the ground.
- Maintain personal hygiene.
- Avoid smoking.
- If you have symptoms, tell your doctorso it can be tested and treated if
required.
9. Pulmonary TB can spread from lungs to different bodyorgans through
hematogenous route.
10. TB is a curable disease which can be treated with a standard 6 month courseof
4 antitubercular drugs which are provided by health care workers under Revised
National Tuberculosis Control Programme (RNTCP),currently RNTCP name
changed into NTEP ( National tuberculosis Eliminating programme) that uses the

4. DOTS (Directly Observed Treatment, Short coursechemotherapy ) strategy
of Indian Government.
Lab diagnosis-
Specimencollection-
-In pulmonary tuberculosis, sputum is collected in a clean mouthed container.
-Two sputum samples are recommended under NTEP , spotsample and early
morning sample.
-In children, gastric aspirate may be collected.
DirectMicroscopy-
- Sputum smear microscopyis the most commonly used for diagnosis of
pulmonary TB.
- ZN staining technique is used to observe red coloredlong Acid fast bacilli
againstthe blue background.
- In 2009 the WHO recommended that the conventional Bright field microscopy
using ZN stain should be replaced by the more sensitive fluorescent light emitting
diode (LED) microscopy. Mostly it is using in high burden countries, it is
expensive, even today it is not used in every laboratories.
-Thus at the present time, ZN microscopymostwidely used in the diagnosis of
TB.

5. Grading of the AFB smear-
- If no bacilli seen in 100 fields so it gives result Negative
- If 1-9 Bacilli seen in 100 fields, it gives result Scanty.
- If 10-99 Bacilli seen in 100 fields, it gives result (1+).
- If 1-10 Bacilli seen per fields and 50field to be examined, it gives result (2+).
-If Greater than 10 Bacilli seen per field and 20field to be examined, it gives
result (3+).
Culture-
Solid media-
It can be also culture on LowensteinJensenmedia (LJ media ) ,incubate it
at 37°C and observe every 7th day . Decontamination procedureof sputum with
adding 5% NaOH solution is important to do before inoculation of sample on
culture media (LJ media). Observeat least for 4-6 weeks for result declaration
negative or positive. Culture positive appears rough, tough and buff white
coloredcolonies.

6. Automated Culture Methods-Several automated culture have been developed in
last decade. They have many advantages over the conventional LJ culture.
CBNAAT, BACTEC MGIT 960 system, True- NAT, Gene-
Xpert/RIF and BACTEC Alert etc.
BACTEC MGIT 960 system:- Digested and decontaminated sputum samples
were inoculated into a mycobacteria growth indicator tube (MGIT) with
modified Middle brook 7H9 broth (liquid media) supplemented
with OADC (Oleic acid, Albumin, Dextrose and Catalase) enrichment
and PANTA (Polymyxin B, amphotericin B, Nalidixic acid, trimethoprim, and
Azlocillin ) antibiotic mixture.
Positive-tube contains approximately 105 - 106
colony-forming units per
milliliter (CFU/mL), detected by fluorescence analysis.
Negative-Culture declared negative with no visible signs of positivity, removed
after 45 days from the instrument.

7. Advantages-
1. Detects growth faster (2-3 weeks),
2. Automated and continuous monitoring of growth,
3. Less contamination issues.
Disadvantages-
It is expensive.
CBNAAT-(cartridge basednucleic acidamplification):-
- A semiautomated molecular assay Gene-Xpert in India is known as CBNAAT
which detects MTB ribosomal RNA or DNA directly from sputum specimens, both
the acid-fast bacilli (AFB) smear-positive and AFB smear-negative.
- In July it was announced that as a new test which could detect resistance to both
first line and second line drugs.
- Clinicians can find out in 90 minutes which drugs a patient is resistant to and
prescribe the correcttreatment, It's very helpful to detect MDR/XDR-TB.
- True-Natwas recommended by the WHO in January 2020 as a alternative to
Gene-Xpert.

8. Advantages-
Its Reliable in comparison of conventional sputum microscopyand speed to getting
a result when compared with the culture test.
Disadvantages-
1. The shelf life of the cartridges is 18 months only,
2. Continuous electricity supply is required,
3. Costly test,
BACTEC Alert-
Based on principle of colorimetric detection of pH change in the medium which
occurs due to CO2 liberated by the growth of Mycobacterium tuberculosis.
Treatment-
In case of active TB disease you will be treated with anti-tubercular medication for
a period of 6-12 months. Most common treatment for active TB is Isoniazid,
Rifampin, Pyrazinamide and Ethmbutol, these are first line drugs of TB.
Secondline drugs- Kanamycin, Capreomycin, and Amikacin are
injectable Bedaquiline and Delamanid are new drugs.
Third line drugs- Rifabutin, Mcarolides, Linozolid.
In case of tuberculosis co-infection with HIV, need to treat tuberculosis first,
because TB disease is spreads by airborne respiratory droplets (coughs and
sneezes) and saliva from one person to other person and HIV is transmitted
through hematogenous route.