TUBERCULOSIS Flashcards
WHAT WAS TUBERCULOSIS REFERRED TO AS IN THE 1700’S?
‘THE WHITE PLAGUE’
THE TUBERCULOSIS BACTERIUM IS ESTIMATED TO BE HOW OLD?
70 000
SINCE WHEN IS TUBERCULOSIS KNOWN?
THE ANCIENT EGYPTIAN TIMES
TUBERCULOSIS IN HUMANS CAN BE TRACED BACK HOW MANY YEARS (DATA OBTAINED BY SEQUENCING ANCIENT DNA)
6 000
WHO ISOLATED THE TUBERCLE BACILLUS AND WHEN?
ROBERT KOCH, 1882
INCIDENCE OF TB OVERALL IS INCREASING OR DECREASING?
DECREASING
RISK FACTORS FOR TB?
MAIN 5: - HIV - MALNUTRITION - DIABETES - ALCOHOL USE - ACTIVE SMOKING OTHERS: - CROWDING
WHICH RISK FACTOR IS ATTRIBUTABLE TO MOST TB CASES?
UNDERNOURISHMENT
INFECTIOUS DOSE OF TB?
3-10 BACILLI (VERY LOW)
HOW IS TB TRANSMITTED?
- THROUGH AEROSOLS CONTAINING M. TUBERCULOSIS
- DOESN’T SPREAD THROUGH CONTACT OR FOOD
STAGES OF TB?
EXPOSURE (BEING IN CONTACT WITH SOMEONE WHO HAS TB)
LATENT TB INFECTION (PERSON HAS TB BACTERIA IN THEIR BODY BUT NO SYMPTOMS)
ACTIVE TB DISEASE (PERSON WITH SIGNS AND SYMPTOMS OF AN ACTIVE TB INFECTION)
REACTIVATION (OF LATENT INFECTIONS)
DESCRIBE THE M. TUBERCULOSIS PATHOGEN:
- GRAM POSITIVE
- LONG RODS
- WAXY COAT OR ‘OUTER MEMBRANE’
- HIGHLY AEROBIC
- INTRACELLULAR PATHOGEN
- REPLICATES SLOWLY
HOW LONG DOES IT TAKE FOR M. TUBERCULOSIS TO GROW IN THE LABORATORY?
3 WEEKS (SLOW REPLICATION)
DESCRIBE THE TB CELL WALL:
- IT RESEMBLES BOTH GRAM POSITIVE AND GRAM NEGATIVE CELL ENVELOPE
- CONTAINS PEPTIDOGLYCAN AND ARABINOGALACTAN
- OUTER, WAXY LAYER MADE OUT OF MYCOLIC ACIDS MADE OF LONG CHAIN FATTY ACIDS
- HYDROPHOBIC MEMBRANE SERVES AS A PERMEABILITY BARRIER (ANTIBIOTIC RESISTANCE!)
- CELL WALL IS KEY FOR VIRULENCE
WHAT ARE MYCOLIC ACIDS?
LONG CHAIN FATTY ACIDS THAT ARE FOUND IN CELL WALLY OF CERTAIN BACTERIA, LIKE M. TUBERCULOSIS
THE HYDROPHOBIC MEMBRANE OF M. TUBERCULOSIS ACTS AS A PERMEABILITY BARRIER AND COMPLICATES TREATMENT AS IT CONTRIBUTES TO:
ANTIBIOTIC RESISTANCE
WHAT ARE GRANULOMAS?
SMALL AREAS OF INFLAMMATION, FREQUENTLY OCCURING IN THE LUNGS
TB BACTERIA PRIMARILY REPLICATES AND SURVIVES WITHIN WHICH HOST CELLS?
MACROPHAGES
APART FROM MACROPHAGES, WHICH OTHER CELLS CAN TB BACTERIA BE FOUND IN?
NEUTROPHILS, DENDRITIC CELLS, ALVEOLAR EPITHELIAL CELLS ETC.
DESCRIBE M. TUBERCULOSIS PROGRESSION AFTER ENTERING THE HOST:
- MULTIPLICATION IN A UNIQUE NICHE
- INFECTION OF INDIVIDUAL MACROPHAGES
- EXPANSION IN INNATE GRANULOMAS
- GRANULOMA MATURATION
- GRANULOMA NECROSIS WITH EXTRACELLULAR REPLICATION
- FURTHER TRANSMISSION
WHAT IS ‘MYCOBACTERIUM’?
- IMMOBILE, SLOW-GROWING, ROD-SHAPED, GRAM-POSITIVE BACTERIUM
- GENUS OF ACTINOBACTERIA, INCLUDES M. TUBERCULOSIS AND M. LEPRAE ETC.
- DUE TO THEIR SPECIAL STAINING UNDER THE MICROSCOPE, WHICH IS MEDIATED BY MYCOLIC ACID IN THE CELL WALL, THEY ARE CALLED ‘ACID-FAST’
DESCRIBE THE M. TUBERCULOSIS AND MACROPHAGE INTERACTIONS:
- MTB ENTERS THROUGH RECEPTOR MEDIATED ENDOCYTOSIS IN A PHAGOSOME (A VESICLE FORMED AROUND A PARTICLE ENGULFED BY A CELL)
- MTB BLOCKS MATURATION OF THE PHAGOSOME AND PREVENTS IT FROM FUSING WITH A LYSOSOME (THROUGH THE ACTION OF PROTEIN CALLED PtpA)
- MTB PREVENTS ACIDIFICATION OF THE PHAGOSOMES
- PRODUCES SEVERAL PROTEINS WHICH INTERFERE IN DIFFERENT ANTIMICROBIAL PATHWAYS (E.G. SapM, KatG)
- MTB ALSO EVENTUALLY INDUCES CELL DEATH IN MACROPHAGES, WHICH THEN DISSEMINATE AND INFECT OTHER MACROPHAGES
EXTRAPULMONARY TB (EPTB):
- HARD TO DIAGNOSE (VAGUE SYMPTOMS) AND TREAT
- OCCURS OUTSIDE LUNGS
- CAN AFFECT ALMOST ALL ORGANS, MOST COMMON ORGANS DEPEND ON THE COUNTRY
RATES OF EPTB AMONG ALL TB CASES?
8-24%
