Mycobacterium Flashcards
Classify mycobacterium
It is a gram positive bacilli and it is slow growing and an obligated aerobe
What is the difference between the gram stain reaction of bacteria
The gram pos stains blue or purple and the gram neg stains red
t/f . Can all bacteria be stained by gram staining
False, not all bacteria can be stained by gram staining .
t/f. Mycobacterium are not classified as either gram pos or neg but rather acid fast bacilli
false., the mycobacterium is a gram pos bacteria based on dna based molecular taxonomy groups but it does not stain with the gram stain because there is a a difference between the mycobacterium cell wall and other gram pos bacteria
Which stain can be used on mycobacterium
Acid fast stain - Ziehl-neelsen /auramin o stain
Discuss the mycobacterium classification
1.Mycobacterium Tuberculosis
It is an obligated pathogen , it requires human to human contact to be transmitted and to spread and
Disease; Tuberculosis
how is it diagosed : Through diagnostic assays M.tuberculosis complex
- Mycobacterium leprae
Obligated pathogen
disease : leprosy
3.Non tuberculosis mycobacterium
disease ; May mimic TB /wound infection /bloodstream infections
It is an opportunistic pathogen /colonizer/pathogen
can cause respiratory disease in immunocompromised patients
Transmission ;Environment to human
not human to human
discuss the cell wall of mycobacterium
- rod shaped bacilli
- Specialized cell wall containing high lipid content ,mycolic acid and it confers an acid fast staining property hence it is refered to as acid fast bacilli
*It is slow growing in culture thus it requires a special media .
Mycobacterium replicated once a day
Discuss the mycolic acid as a virulence factor
- The mycolic acid makes up 60% of the cell wall
- Mycolicacid are a virulence factor which prevents phagocytic vacuole(phagolysosome )
AFB stain primary stain binds irreversiably to the mycolic acid
*
Discuss the principles of acid fastness staining
- Application of carbolfuchsin
- alcohol wash
- Application of methylene blue
the pick/red colour absored by the mycobacteria will stand out in the blue
list the two types of acid fast stains
1.Zichl neelsen stain (carbolfuchsin stain- bright pink) with blue background
- Auramine o stain (florescence type of stain)
* it is easy for the eye to see
* it is sued to stain clinical specimen eg sputum specimen
What happens when you are exposed to mycotubecuosis
- When you are exposed to M.TB you are either
* Infected or not infected
- If you are infected ,it is either
- there will be an immune response and 90% of the population can contain the TB infection
-This will result in latent TB infection meaning
*No symptoms
*NON infectious
*replication is controlled by immune system and thus the low load of organisms
and it is not culturable
*Can be re-activated
or ,what will happen is:
10% o the time ,it will result in an active TB disease meaning :
you will be symptomatic
*Infectious
*bacilli are replicating
thus a high load of organisms and it is culturable
*10% , lifetime risk and 10% per year infected with HIV
What are clinical manifestations of TB
Adults;
- Persistent cough and sputum
- Loss of weight
- Loss of appetite
- Night sweats and fever
- chest x ray changes
Children:
- chronic cough
- pneumonia
- failure to thrive
- chest x ray changes
What are the clinical manifestations extra pulmonary TB
1.TB meningitis: TB of meninges
2.Tuberculoma :TB of brain
*TB lymphadenitis: TB of lymph odes
*Osteomyelitis
Renal TB
*Genitourinary TB; TB of reproductive system
*Vertebral TB
*TB of the pleura
* Cutaneous TB :TB of the skin
Discuss the non-tuberculous mycobacteria ( NTM/MOTT)
- Does not belong to the tuberculosis complex
- It is found in the environment reservoir: soil /water
- It can be aquired from inhalation of infectious aerosols/ through ingestion
- Is not transmitted from person to person
- Isolation from clinical specimen does not mean they are assoiciated with disease
- Can colinize human without getting infection or developing disease
- If isolated from respiratory specimen ,-send a repeat specimen ,if isolated more than 2 times it may indicate NTM disease
- If isolated from a sterile specimen, probably a disease
What are the common NTM species associated with human disease
- m.avium
- m.intracellulare
- .m.kansasii
