MYCOBACTERIUM Flashcards
Mycobacterium tuberculosis
Characteristics
• In tissue, thin, straight rods,
_____in tissue;
_____in length
_____in width
0.4 x 3 um
2-4 um
0.2-0.5 um
Mtb
On media,_____,_____,______; CSF
form small & (color) colonies
coccoid, filamentous, serpentine cord forms
buff colored or colorless
MTB
•______bacilli;
_______(macrophages) bacteria;
has a slow generation time,
_____- prevents immune recognition
Obligate aerobic
facultative intracellular
18H
MTB
Either GP or GN; very weakly Gram-positive or not at all _______
ghost cells
MTB
• strongly ________due to the____
acid-fast (Ziehl-Neelsen stain)
mycolic acid
MTB
•Resistant to…
dyes, antibacterial agents, acids, alkalies, quats; drying
T or F
•Survive in milk, organic materials, on pasture land
True
MTB
•Sensitive to UPFAG
UV light
pasteurization
formaldehyde
alcohol
glutaraldehyde
Strongly acid fast
Slightly acid fast
Non acid fast
Mycobacteria
Nocardia
Corynebacteria
Peptidoglycan Layer:
This is the basic part of the bacterial cell wall. It contains:
• N-acetylglucosamine (sugar)
• D-glutamic acid, m diaminopimelic acid, D- and L-alanine (amino acids)
Arabinogalactan Mycolate Layer:
This layer contains sugars:
• Connected to mycolic acids.
D-arabinose and D-galactose (sugars)
These are long fatty acids (C78-C90) that make the cell wall lipid-rich.
Mycolic Acids:
These lipids help make the bacteria acid-fast, meaning it doesn’t lose color in certain stains (like Ziehl-Neelsen). This makes it easy to identify under the microscope.
Mycolic acid
Proteins like ______ cause an immune response (the tuberculin reaction).
PPD (Purified Protein Derivative)
“Arabs & Myco Love Long Chains”
Arabinogalactan (D-arabinose & D-galactose)
Mycolic acids (C78-C90, long fatty acids)
Lipid-rich (acid-fast)
Layers (peptidoglycan, arabinogalactan)
prevent intracellular killing and digestion, inhibit phago-lysosome fusion
Mycolic acids, mycosides, sulfatides
complexed with mycolic acids cause granuloma formation
• Muramyl dipeptide (peptidoglycan)
- major virulence, inactivate macrophages and scavenge oxidative radicals (catalase, superoxide dismutase)
• Lipoarabinomannan (LAM)
serves as adjuvant;
with heat shock protein/tuberculin proteins cause hypersensitivity and form tubercle
Wax D
• cause caseous necrosis
Phospholipids
virulent strains form serpentine cords; inhibit phagocyte chemotaxis, activation, phagosome-lysosome fusions and digestion
Cord factor (trehalose-6,6”-dimycolate)
TUBERCULOSIS:
Predisposing factors
• Close contact with large populations of people, i.e., schools, nursing homes, dormitories, prisons, etc.
• Poor nutrition
• Pregnancy
• HIV infection
• IV drug use
• Alcoholism
In most cases, your body’s immune system controls the infection, leading to presumed sterilizing immunity. This means the bacteria are eliminated before they cause any symptoms.
In about____of people, the infection progresses quickly and leads to active, primary TB, causing symptoms like coughing, fever, and weight loss.
Self-Cure (90%)
Early Progression (5%)
In most cases (95%), the immune system contains the bacteria, but doesn’t kill them. This results in latent TB —you’re infected, but have no symptoms and can’t spread TB.
Later in life, 5% of people with latent TB may experience reactivation (the bacteria become active again) or get reinfected, leading to active TB symptoms.
Initial Containment (95%)
Reactivation or Reinfection
Pathogenesis os TB
Stage I: Inhalation
You inhale tiny droplet nuclei (SIZE) containing Mycobacterium tuberculosis (Mtb).
These droplets are expelled by someone with_____ tuberculosis through coughing, sneezing, or even talking.
Stage II: Primary Infection
Once inhaled, the Mtb bacteria reach the lungs and infect______ (cells in the lungs that normally destroy invaders).
Inside these macrophages, the bacteria start to multiply freely, as the macrophages are not yet able to stop them.
less than 25 micrometers
cavitary TB
non-immune alveolar macrophages
Pathogenesis of TB
Stage III: T-Cell Response
_______(a type of immune cell) recognize the Mtb antigens (MTB Ag) and begin to move into the infected area.
These T-cells release______, which activates macrophages and helps destroy the Mtb bacteria.
Stage IV: Unactivated Macrophages
Despite some macrophages being activated by the T-cells, many other macrophages remain unactivated or poorly activated.
Because of this, Mtb bacteria continue to replicate, and the infected area (???) grows larger.
Stage V: Caseation and Cavity Formation
The infected tubercles become______ and start to liquefy.
This liquefaction creates an ideal environment for Mtb to grow rapidly.
Eventually, this leads to_____ formation, which allows the bacteria to spread into the airways and potentially infect other parts of the lungs, or be coughed out, further spreading the infection.
T lymphocytes
gamma interferon (IFN)
tubercles
caseous (cheese-like in appearance)
cavity
In this form, the body’s immune response causes exudation, or the release of fluid, similar to pneumonia.
The ______will be positive, meaning the person has been exposed to TB, but the infection doesn’t progress.
This type resembles an early, non-specific immune response to Mtb.
tuberculin skin test (TST)
This type leads to the formation of chronic granulomas—clusters of immune cells that wall off the bacteria.
These granulomas contain the infection, but the bacteria may remain dormant inside.
The immune system produces these to control the infection and prevent it from spreading, resulting in a chronic, contained state
Productive Type (chronic granuloma)
________
Seen in primary tuberculosis (PTB).
It involves the initial lung lesion and affected lymph nodes.
If untreated, the lesion may become fibrotic (scar tissue forms) as the body tries to heal.
_________
This is the calcified version of a Ghon lesion.
It indicates that the body has controlled the TB infection by hardening (calcifying) the Ghon lesion and the nearby mediastinal lymph nodes.
_______
Occurs when TB spreads to the upper part (apex) of the lung.
It forms a small nodule (focus) at the lung’s apex, typically seen in reactivated TB or secondary TB.
- Ghon Complex
- Ranke Complex
- Simon Focus
[primary lesion]
- granuloma + draining lymph nodes
Ghon complex
A granuloma in tuberculosis is a structured immune response designed to contain the infection. It has three distinct zones:
_____
Contains multinucleated giant cells, which are large immune cells formed by the fusion of several macrophages.
These cells attempt to trap and destroy the TB bacteria at the core.
_________
Filled with pale epithelioid cells , which are activated macrophages that look like epithelial cells.
They form a barrier around the central area to further contain the infection.
_________
The outermost layer, which includes lymphocytes (a type of white blood cell) and other immune cells like fibroblasts.
These cells coordinate the immune response and help maintain the structure of the granuloma.
Central Area
Mid Zone
Peripheral Zone:
Clinical Features of Tuberculosis
- Chronic cough, dyspnea, fever, hemoptysis, night sweats, weight loss
• Two patterns:
Primary - childhood, disseminated (poor CMI response);
Secondary - hypersensitive tissue destructive response
Pulmonary infection
Extrapulmonary TB affects areas outside the lungs.
1. \_\_\_\_\_\_\_\_: • TB infection in the lining of the lungs (pleura) causing fluid buildup (effusion). • Symptoms may include chest pain, shortness of breath, and fever. 2. \_\_\_\_\_\_\_\_\_: • TB infects the lining of the brain and spinal cord (meninges). • Symptoms include severe headache, fever, stiff neck, and neurological symptoms (confusion, seizures). 3. \_\_\_\_\_\_\_\_: • A rare form where TB bacteria spread through the bloodstream, affecting multiple organs. • Symptoms are non-specific and may include fever, weakness, weight loss, and difficulty breathing. 4. \_\_\_\_\_\_\_: • TB infection in the kidneys and urinary tract. • Symptoms can include blood in the urine, frequent urination, or lower back pain. 5. \_\_\_\_\_\_\_: • TB infects the bones and joints, commonly the spine (called Pott’s disease). • Symptoms include pain, swelling, and difficulty moving affected joints. 6. \_\_\_\_\_\_\_\_\_: • TB infection of the intestinal tract. • Symptoms may include abdominal pain, diarrhea, weight loss, and fever.
Extrapulmonary TB can affect different parts of the body and may not always have typical lung-related symptoms.
TB Pleural Effusion
Tuberculous Meningitis
Miliary TB
Renal and Urogenital TB
Bone and Joint TB
TB Enteritis
