Mycobacteium Tuberculosis Flashcards
Mycobacterium
Filamentous
Aerobic
Non-sporulating
Bacilli
“Beaded gram positive rods”
High mycolic acid content in the cell wall (resistance to detergent, antibiotics)
Acid fast
Slower growth
Mycobacterium tuberculosis complex (MTb)
Comprised of M tuberculosis and seven closely related species (M bovis, M africanum, M microti, M pinnipedii, M canetti, M mungi, M caprae
Transmission is person to person
M bovis
Transmitted to human from infected cows or contaminated milk
Pyrazinimide resistant
M bovis bacillus Calmette-Guerin (BCG) is a strain used as a vaccine for TB
Tuberculosis
Caused by mycobacterium tuberculosis
Human to human spread
Bacilli are transmitted an infectious aerosols produced by coughing talking or singing
Risk of infection depends on bacterial load, exposure time, and environmental factors
MTb pathogenesis
Watch is an alveoli and is engulfed by macrophages
Prevents fusion of phago lysosome
Attracts monocytes and lymphocytes
Developes granule a (dependent on CD4 T cell and TNF)
Causes caseous necrosis
Infected macrophages carried to lymph nodes
MTb is a type _ hypersensitivity reaction that can be measured using
IV
TST/PPD or IGRA
Risk factors for Tb infection
Exposure to TB case
from TB endemic area
homeless
incarcerated
work in healthcare
Tb with symptoms=
Active TB disease
TB infection without symptoms=
Latent TB
TB risk for deactivation
Recently infected
Children <5
Immunosuppressed (HIV, TNF inhibitor, leukemia, diabetes, end stage renal disease)
Malnourished
smokers
alcoholics
Symptoms of TB
Pulmonary disease
Prolonged cough, hemoptysis, chest pain, weight loss, loss of appetite, night sweats, fever, fatigue, upper lung lesions, pleural infection
Extrapulmonary disease (meningitis, tuberculoma, lymph node enlargement
Bone infection (spine)
Genitourinary
Peritoneal
Disseminated
Diagnosis of symptomatic TB infection
AFB smear
AFB culture
molecular assay
Diagnosis of asymptomatic TB infection
Immune Assay-PPD/TST test, interferon gamma release assays
_ staining of TB can be performed
Acid fast using Ziehl-Nielsen
Requires high bacterial burden
Cannot distinguish between Mycobacterium species
_ is the gold standard for TB diagnosis
Culture
MGIT or solid media (requires weeks)
Molecular detection of TB
Rapid
Specific
Fastest way to rule out infectious TB
Latent TB diagnosis
tuberculin hypersensitivity (requires effect of CD4 TH1 cells, IL-12, INF gamma, TNF)
Tuberculin skin testing and IGRA
IGRA
better specificity for detecting TB (fewer false positives
Does not rule out active TB
Treatment of latent TB
Prevent development of active disease
Rifampin + INH
Treatment of active TB
4 drug therapy (RIPE)
Rifampin, Isoniazid, Pyrainamide, Ethambutol
Drug resistance TB
Resistant to 1 in 4 first line antibiotics
MDR TB
Resistant to 2 of 4 first line antibiotics
XDR TB
Resistant to at least 1 of 3 second line antibiotics
Multi drug resistant TB
Risk associated with exposure to MDR-TB, residence in high risk area, failure to respond to therapy
Treat with multiple agents
High toxicity and high mortality
Prevent TB by
Treating those infected
Testing these who meet exposure definition
