Micro Acid Fast Bacteria

Front 1

What two bacteria that are important in the acid-fast category?

Back 1

Mycobacterium tuberculosis and leprae

Front 2

Mycobacterium are what kind of bacteria?

Back 2

Obligate aerobe, that are thin rods with lipid-laden cell walls, making them acid-fast on staining.

They are also facultative intracellular that seek refuge in macrophages.

Front 3

Since acid fast bacillus is an obligate aerobe, where does it commonly infect?

Back 3

The lungs, where oxygen is abundant--in the upper lobes.

Front 4

What is the one class of lipids involved in mycobacterial virulence?

Back 4

Mycosides, a mycolic acid (large fatty acid) bound to a carbohydrate, forming a glycolipid.

Front 5

What is cord factor, where is it found, and what does it result in?

Back 5

It is a mycoside formed by the union of 2 mycolic acids with a disaccharide. It is only the virulent strains of Mycobacterium tuberculosis. It results in parallel growth of the bacteria, making them appear as cords.

Front 6

Cord factor may cause what?

Back 6

Inhibits neutrophil migration and damages mitochondria. Injection into mice, results in the release of TNF (or cachectin), resulting in rapid weight loss (which occurs with TB).

It also stimulates formation of granulomas.

Front 7

What are sulfatides?

Back 7

Mycosides resembling cord factors with sulfates attached to the disaccharide. They inhibit phagosome from fusing with the lysosome that contains bactericidal enzymes.

Front 8

What is wax D?

Back 8

A mycoside that acts as an adjuvant (enhances AB formation to an antigen) and may activate the protective cellular immune system.

Front 9

When M. TB enters, what occurs?

Back 9

The host has no specific immunity initially. TB survives in the neutrophils and macrophages due to virulence factors. The host the acquires its prime defense against the TB, cell-mediated immunity. Some of the macrophage succeed in breaking up the bacteria, and they then can present the antigens on their cell surface in the lymph node to helper T-cells. When T-cells then secrete lymphokines upon encountering their antigenic target; therefore, macrophages are activated and can now destroy the bacteria.

Front 10

When the macrophages are activated against TB, what results?

Back 10

Caseous necrosis results. This is when the macrophage attack and cause necrosis of lung tissue. This soft caseous center is surrounded by macrophages, multi-nucleated giant cells, fibroblasts, and collagen deposits and frequently calcifies. This granuloma keeps the bacteria at bay but it remains viable.

Front 11

What type of hypersensitivity is the PPD (Purified Protein Derivative) test?

Back 11

Type IV

Front 12

A person with a positive PPD test, is considered to have?

Back 12

Latent tuberculosis

Front 13

What can give a false positive test for PPD?

Back 13

BCG (Bacillus Calmette-Guerin) vaccine for TB. This vaccine is debatably effective in preventing TB, but may result in positive PPD.

Front 14

What can give a false-negative test?

Back 14

PTs who are usually anergic, which means that they lack a normal immune response due to steroid use, malnutrition, AIDS, etc.

Front 15

What is primary TB?

Back 15

The bacteria is transmitted from aerosolized droplet nuclei form infected individuals. It lands in the area of greatest air flow in the lungs: middle and lower lobes. The bacteria then enters macrophages, multiply and spread to regional lymph nodes.

Front 16

Cell-mediated immunity can result in asymptomatic primary infection or systematic primary infection. Explain both.

Back 16

With asymptomatic infection, the bacteria is walled off in caseous granulomas, which heal with fibrosis, calcification, and scar formation. The bacteria decrease in numbers, but remain viable.

Symptomatic occurs less frequently, but in children, elderly, and immunocompromised individuals. Organisms are not suppressed.

Front 17

A calcified tubercle is called?

Back 17

A Ghon focus.

Front 18

A Ghon focus accompanied by perihilar lymph node calcified granulomas is called?

Back 18

A Ghon or Ranke, complex.

Front 19

What is secondary or reactivation TB?

Back 19

Most adult cases of TB occurs as latent TB after the bacteria have been dormant for some time. It is presumed that a temporary weakening of the immune system may precipitate reactivation.

Sometime after reactivation, the material within the granulomas becomes caseous. The central area of the granulomas undergoes necrosis, and may break into a bronchus discharging M. tuberculosis into exhaled air.

Front 20

What organs are involved in TB?

Back 20

Lung, pleural and pericardial infection; lymph nodes (mainly cervical; kidney (sterile pyuria); skeletal (chronic arthritis of 1 joint typically); CNS (subacute meningitis and granulomas in the brain); and miliary tuberculosis.

Front 21

What is scrofula?

Back 21

Lymph node tuberculosis: swollen, matted together, and drain.

Front 22

What is sterile pyuria?

Back 22

PTs will have RBC and WBC in urine, but no TB will be seen on Gram stain or grow in culture (M. TB takes weeks to grow).

Front 23

What is Pott's disease?

Back 23

Disseminated TB that invades skeletal tissues, resulting in IV discs and adjacent vertebral bodies being destroyed, causing osteomyelitis.

Front 24

What is miliary tuberculosis?

Back 24

Tiny millet-seed-sized granulomas (tubercles) disseminated all over the body like a shotgun blast: kidneys, lungs, liver, and other organs.

Front 25

How do you diagnosis TB?

Back 25

PPD skin test, chest x-ray, and sputum acid-fast stain and culture.

Culture: Lowenstein-Jensen agar

+ PPD: >15 mm; with AIDS >5 mm.

Front 26

How do you treat Mycobacterium tuberculosis?

Back 26

Treat with RIPES (multiple drugs to avoid resistance): rifampin, isoniazid (INH), pyrazinamide, ethambutol, streptomycin.

Prophylaxis (for PPD +), INH

Front 27

What is a major pathogen of AIDS PTs, resistant to multiple drugs, results in chronic wasting illness, bacteria dissemination, and chronic watery diarrhea?

Back 27

Mycobacterium avium-intracellulare

Front 28

What causes leprosy?

Back 28

Mycobacterium leprae

Front 29

Can M. leprae grow on artificial media?

Back 29

No, only on footpads of mice, armadillos, and in monkeys.

Front 30

Who can catch leprosy?

Back 30

Only those who are susceptible, with exposed skin lesions from an infected individual or respiratory secretions (more likely).

Front 31

What is dependent for leprosy to result in an infection?

Back 31

1) The bacteria grows better in cooler body temperatures closer to the skin surface; 2) Severity of disease is dependent on host's cell-mediate immune response to the bacilli.

Front 32

What does leprosy affect?

Back 32

Damages skin (sparing warmer areas, such as the armpit, groin, and perineum) and superficial nerves, eyes, nose, and testes.

Front 33

What is the severest form of leprosy, because the PT cannot mount a cell-mediated immune response.

Back 33

Lepromatous leprosy

Front 34

What occurs with Lepromatous leprosy?

Back 34

Leonine facies (facial skin becomes thinkened, like a lion); saddlenose deformity (nasal cartilage destroyed); internal testicular damage (infertility); anterior segment of eyes damaged (blindness); peripheral nerves are thickened (loss of sensation in glove and stocking distribution); inability to feel fingers and toes (leading to trauma and secondary infections); contraction and resorption of fingers and toes.

Front 35

What is tuberculoid leprosy?

Back 35

PTs can mount an immune response, so skin damage is not excessive, and sometimes results in a self-limiting disease.

Localized superficial, unilateral skin and nerve involvement. 1 - 2 skin lesions. Well-defined, elevated blotches. Enlarged nerves can be palpated that are close to the skin (greater auricular, ulnar, posterior tibial, and peroneal)

Front 36

Who would have a true positive result from a lepromin skin test, and who would have a false negative, and why?

Back 36

PTs with tuberculoid leprosy would have a true positive since they have a cell-mediated immune response. PTs with lepromatous leprosy would have a false negative, since they cannot mount a cell-mediated immune response.

Front 37

How do you treat leprosy?

Back 37

Dapsone, rifampin, clofazamine. Used in combination to prevent resistance.

Front 38

What contributes to enhance virulence of Mycobacterium tuberculosis?

Back 38

LAM, which is recognized by macrophage mannose receptor.

Front 39

What is a tubercle?

Back 39

Fibrotic, calcified scars, OR:

Chronic granuloma encapsulated with fibrin. It has a central area of large, multinucleated giant cells containing tubercle bacilli, midzone of epithelioid cells, and a peripheral zone of fibroblasts, lymphocytes, and monocytes.