Mycobacterium

Front 1

What characterizes Mycobacterium tuberculosis?

Back 1

- Long, slender, straight or curved
- Acid fast bacilli
- Slow grower
- Obligate aerobes
- Intracellular bacterium

Front 2

What is unique about the cell wall of Mycobacterium?

Back 2

It is composed of high molecular weight acidic waxes; mycolic acid, Wax D, cord factor, and sulfatides.

Front 3

What is the purpose of the complex cell wall of Mycobacterium?

Back 3

- Resists phagocytosis, disinfectants, dessication, and antibiotics.

Front 4

What are the virulence factors associated with Mycobacterium tuberculosis?

Back 4

- Complex Cell Wall
- Intracellular (hidden from humoral response)
- Siderophores - iron acquisition
- Antibiotic Resistance (via chromosomal mutations and genges
- Inhibits phagolysosome formation

Front 5

What proteins are responsible for inhibition of phagosome-lysosome fusion in macrophages?

Back 5

ESAT-6 and CFP-10 (Both are found encoded RD1 region of the chromosome).

Front 6

How does transmission of TB occur?

Back 6

Inhalation of respiratory mucus droplets in the air (inoculum size is high, repeated exposures are typically required except in susceptible individuals).

Front 7

What is the pathogenesis of primary course of TB?

Back 7

Inhalation of bacteria --> bacteria are small enough to proceed to the alveoli where they invade alveolar macrophages ---> migrate to the lymph nodes where they initiate immune response --> in the lungs, lesions form and granulomas develop --> activate macrophages fight the infection --> bacteria stop growing, and calcification of the lesion occurs.

Front 8

What is meant by a secondary TB infection?

Back 8

Reactivation of bacteria already present in the host (more common) or re-infection with M. tuberculosis (in endemic areas; less common).

Front 9

What characterizes the tubercles seen in TB?

Back 9

They are granulomas with a central core of M. tuberculosis surrounded by macrophages and T-cells (bacilli cause caseous necrosis); the granulomas can calcify at which point they are known as Ghon complex.

Front 10

What describes the immune response regarding TB?

Back 10

CD4+ T-cell response --> they secrete INF-gamma and TNF which activate macrophages --> macrophages secrete inflammatory cytokines (TNF, IL-1, IL-6, IL-8, and GM-CSF) which cause inflammation and granuloma formation.

Front 11

What signs/symptoms are associated with active TB infection?

Back 11

- Fever
- Night Sweats
- Weight Loss
- Cough
- Hemoptysis
- < appetite
- Abnormal CXR

Front 12

What damage is seen in disseminated tubercuolosis (miliary and extrapulmonary)?

Back 12

- Renal Necrosis and scarring
- Degeneration of spine (Potts' Disease)
- Damage to reproductive organs
- Meningitis

Front 13

What stain is used for the direct identification of acid-fast bacilli from bronchoalveolar lavage (BAL) or sputum?

Back 13

Ziehl-Neelsen Stain (Acid Fast) or Fluorescent Dye

Front 14

What method of detection is now used for the cultivation of Mycobacterium tuberculosis in the laboratory?

Back 14

Fluorometric Dectection (4-8 days), isolation of bacteria (3-6 days), drug susceptibility (2-3 days) - total time 10-14 days.

Front 15

What is the old method of cultivation of Mycobacterium tuberculosis in the laboratory?

Back 15

Lowenstein-Jensen Media (4-8 weeks)

Front 16

How is the diagnosis of latent TB made?

Back 16

Tuberculin Skin Testing (PPD) - measure the induration, not the erythema. A positive PPD means there is a current or prior infection.

Front 17

For which group of individuals is a 5 mm induration with a PPD interpreted as positive for TB?

Back 17

- HIV patients
- Close contact to case of infectious TB
- Patient with abnormal CXR
- Immunosuppressed
- Organ transplant recipients

Front 18

For which group of individuals is a 10 mm induration with a PPD interpreted as positive for TB?

Back 18

- Person with clinical conditions that place them at high risk.
- Children < 4 yrs of age
- Adolescents exposed to adults at high risk

Front 19

For which group of individuals is a 15 mm induration with a PPD interpreted as positive for TB?

Back 19

- Individuals with no known risk factors for TB.

Front 20

What type of reaction is the response to a PPD?

Back 20

Type IV, delayed-type hypersensitivity

Front 21

How does QuantiFERON (TB Gold) work?

Back 21

In vitro assay that uses whole blood from a patient to measure cell-mediated immune response to ESAT-6 and CFP-10 antigens by looking for IFN-gamma production through ELISA. If you possess antigen specific T-cells they will respond to ESAT-6 and CFP-10 producing IFN-gamma.

Front 22

What are the advantages of using QuantiFERON (TB Gold)?

Back 22

- Single Patient visit
- Only response to M. tuberculosis
- No "booster phenomena"
- Eliminates subjectivity
- Safe, uses whole blood and results w/in 24 hrs

Front 23

What is the treatment for active TB infection?

Back 23

Four Drug Treatment Until known susceptibilities:
- Isoniazid
- Rifampin
- Pyrazinamide
- Ethambutol
Length of Treatment 6-24 months

Front 24

What is the meaning of the mnemonic DOTS?

Back 24

Directly Observed Treatment, Short-Course - means that a health care worker directly observe the patient take their anti-TB drugs.

Front 25

What characterizes M. avium complex (MAC)?

Back 25

- Major cause of death in AIDS patients
- Can colonize the GI and respiratory tract and then disseminate
- Very drug resistent

Front 26

What characterizes M. kansasii?

Back 26

- Causes pulmonary infection
- Non-communicable
- Treat with Isoniazid and Rifampin

Front 27

What characterizes M. marinum?

Back 27

- "Swimming pool granuloma," ulcer
- Non-communicable
- Treat with Rifampin and Ethambutol

Front 28

What type of mycobacteria is considered to be a rapidly growing mycobacteria?

Back 28

Mycobacterium fortuitum

Front 29

What characterizes the Runyon Group IV mycobacteria?

Back 29

Rapidly growing mycobacteria such as M. fortuitum; they are ubiquitous in the environment and opportunistic pathogens (skin lesions, abscesses) - can be a problem following plastic surgery.

Front 30

What bacteria is the causative agent of leprosy (Hansen's Disease)?

Back 30

Mycobacterium leprae - intracellular bacterium that grows in macrophages and Schwann Cells (long incubation period).

Front 31

What is the transmission associated with M. leprae?

Back 31

Transmitted via aerosolized droplets

Front 32

What are the two major forms of leprosy?

Back 32

- Tuberculoid
- Lepromatous

Front 33

Describe the Tuberculoid form of M. leprae?

Back 33

- Less Severe
- Cell-mediated Immunity (TH1)

Front 34

Describe the Lepromatous form of M. leprae?

Back 34

- More Severe
- Poor cell-mediated immunity (TH2)
- Damage to sensory nerve; loss of feeling leads to injury and secondary infections.

Front 35

What is the treatment for the Tuberculoid form of M. leprae?

Back 35

- Rifampin
- Dapsone

Front 36

What is the treatment for the lepromatous form of M. leprae?

Back 36

- Dapsone
- Rifampin
- Clofazimine