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MCIM 224 > 22 Bacterial Pathogens I - Respiratory Infections > Flashcards

22 Bacterial Pathogens I - Respiratory Infections Flashcards

1
Q

Most commonly affected body sites by bacterial pathogens?

A
  1. Respiratory tract
  2. Skin and soft tissues
  3. GI tract
  4. Genitourinary tract
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2
Q

T or F: Upper respiratory tract infections are more severe than lower resp. tract. infections

A

F

Upper respiratory tract infections are LESS severe than lower resp. tract. infections

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3
Q

T or F: Most bacteria have a preference wrt whether they infect either the upper or lower resp tract

A

T

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4
Q

How are resp tract infections transmitted? (2)

A
  1. Droplet transmission

2. Airborne transmission

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5
Q

What does Streptococcus pyogenes (“Group A Strep”) cause?

A

Streptococcal pharyngitis (aka “Strep throat”)

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6
Q

Streptococcal pharyngitis (aka “Strep throat”) is caused by what kind of bacteria (Gram stain? Shape?)

A

Gram positive cocci

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7
Q

How is Streptococcal pharyngitis (aka “Strep throat”) transmitted?

A

Respiratory droplet transmission

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8
Q

Most common age range affected by Strep throat?

A

5-15 yrs

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9
Q

Go through the pathogenesis of Strep throat.

A
  1. Strep enters upper resp tract (throat)
  2. It attaches to epithelial cells
  3. It multiplies in throat and uses anti-phagocytic capsule to evade host defenses
  4. It secretes hemolysin and other exotoxins (but doesn’t penetrate into deeper tissues)
  5. Symptoms appear (inflammation and sore throat, pus, swollen lymph nodes)
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10
Q

T or F: Strep throat often requires medical intervention

A

F

Strep throat is self-limiting

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11
Q

Why’re antibiotics usually used for strep throat despite it being a self-limiting illness? (2)

A
  1. prevent pt from becoming an asymptomatic carrier

2. prevent more severe complications from arising

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12
Q

List possible complications from untreated strep throat. (3)

A
  1. Scarlet fever
  2. Glomerulonephritis
  3. Rheumatic Fever
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13
Q

Symptoms of scarlet fever?

A
  1. Strep throat symptoms (sore throat, pus, swollen lymph nodes)
  2. Skin rash
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14
Q

The skin rash of scarlet fever is caused by…

A

certain strains of Strep that produce “Erythrogenic Exotoxin”

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15
Q

What does the erythrogenic exotoxin associated w/ certain strains of Strep specifically damage in the body? What occurs as a result?

A

Small blood vessels > high fever, red rash on face, trunk, and arms, as well as an inflamed “strawberry” tongue

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16
Q

A “strawberry tongue” is associated w/…

A

scarlet fever (a potential complication of Strep throat)

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17
Q

What occurs during glomerulonephritis?

A

Immune complexes made of Strep antigens + anti-Strep antibodies accumulate in the glomeruli (blood vessels) of the kidneys > fever, blood in urine, increased bp

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18
Q

When does glomerulonephritis occur?

A

During the RECOVERY stage of UNTREATED Strep throat

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19
Q

How is glomerulonephritis similar to scarlet fever?

A

Aside from both being complications of untreated Strep throat, they’re also both caused by only SOME strains of Strep pyogenes.

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20
Q

What is rheumatic fever?

A
  1. A complication of Strep infection
  2. An autoimmune disease where antibodies formed against Strep proteins CROSS-REACT w/ antigens found in the heart and joint tissues
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21
Q

Strep pyogenes can also cause necrotizing fasciitis. What is this?

A

“Flesh-eating disease” > a destructive tissue infection caused by various bacterial species, including Strep pyogenes

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22
Q

In order for Strep pyogenes to cause necrotizing fasciitis, how must it be transmitted?

A

Entry into skin via cuts (NOT by resp droplets)

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23
Q

In necrotizing fasciitis, what type of tissue is initially degraded by bacterial enzymes? What occurs afterwards?

A

Connective tissue is degraded first.

After tissue separation, the bacteria invade into deeper muscle tissues > tissue necrosis, high fever, rapidly-spreading inflammation occur

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24
Q

T or F: Streptococcus pyogenes is v. common, relatively mild, and easily treated.

A

T

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25
Q

When do serious complications of Strep infections tend to occur?

A

When the infection is left untreated

26
Q

T or F: Sore throats are always caused Strep throat.

A

F

Sore throats can be due to viral infections too

27
Q

How can Strep throat be diagnosed?

A

Throat swab > look for hemolytic colonies on blood agar media

28
Q

Streptococcal pharyngitis (aka “Strep throat”) is a(n) ______ resp. tract infection.

A

upper

29
Q

Bacterial pneumonias are infections of the _____ resp. tract, and include: (2)

A

lower

Lobar and bronchial pneumonia

30
Q

What does lobar pneumonia affect?

A

a section of the lung

31
Q

What does bronchial pneumonia affect?

A

patches of lung around bronchial tubes that convey air into lungs

32
Q

Pneumonia in general leads to what? (2)

A
  1. Inflammation of lungs

2. Filling of air-spaces w/ fluids

33
Q

~80% of bacterial pneumonias are caused by these 3 bacteria:

A
  1. Streptococcus pneumoniae
  2. Mycoplasma pneumoniae
  3. Haemophilus influenzae
34
Q

Risk factors for pneumonia? (5)

A
  1. Elderly
  2. Immunocompromised
  3. Smoking
  4. Chronic resp diseases (e.g asthma, emphysema, etc.)
  5. Being on a ventilator
35
Q

What structural feature of pneumonia-causing bacteria allow them to evade phagocytosis (and hence, are virulence factors in pneumonia)?

A

Bacterial capsules

36
Q

What does a bacterial pneumonia require for treatment?

A
  1. Aggressive antibiotic treatment
  2. Fever suppression
  3. +/- breathing assistance in severe cases
37
Q

What causes tuberculosis?

A

Mycobacterium tuberculosis

38
Q

Tuberculosis is an infection of the ____ respiratory tract

A

lower

39
Q

Name the three respiratory tract bacterial infections, and which part of the tract (upper or lower) ea affect.

A
  1. Strep throat (upper)
  2. Bacterial pneumonia (lower)
  3. Tuberculosis (lower)
40
Q

What staining technique can be used to detect mycobacterium tuberculosis? Why should this stain be used?

A

Acid-fast stain

This bacterium has mycolic acid in its cell wall

41
Q

T or F: Mycobacterium contains most of the usual virulence factors seen in other bacteria, such as exotoxins, pili, and capsules (hence why it’s particularly dangerous)

A

F

Mycobacterium tuberculosis actually LACKS most of the usual virulence factors seen in other bacteria

42
Q

Tuberculosis disease symptoms are due to…

A

the HOST’S immune response to M. tb, not to the bacterium itself.

43
Q

Two forms of TB:

A
  1. Primary tuberculosis

2. Secondary tuberculosis

44
Q

Describe a primary tuberculosis infection sequence.

A
  1. Airborne and/or droplet transmission from infected host
  2. Phagocytes ingest M. tb in lungs > M. tb survives and multiply INSIDE phagocytes
  3. Phagocytes die > break open > release live M. tb > cycle repeats
  4. After ~3 weeks, helper T cells activated > macrophages are stimulated
  5. Stimulated macrophages kill M.tb or create a Ghon complex (aka “tubercle”) > M.tb is enclosed in tubercle structure and prevents further spread
45
Q

What happens w/ the tubercles in 95% of primary cases of tuberculosis?

What is the health state of these pts?

A

The tubercules HEAL by fibrosis and calcification

Pts are usually asymptomatic and NOT infectious (no free bacteria in the lungs)

46
Q

What occurs in 5% of primary tuberculosis cases?

How many die if left untreated?

Who’s most likely to suffer from primary TB complications?

A
  1. Cell-mediated immune response fails due to a lack of Th cell activation
  2. M.tb spreads to other organs (“extrapulmonary TB”)
  3. Various organ tissues get damaged due to by-products of macrophage attacks (necrotic cavities containing M.tb in lungs and other organs)

Up to 50% die if left untreated

Kids and immunocompromised are most likely to suffer from primary TB complications

47
Q

What is secondary tuberculosis?

A

REACTIVATION of dormant Mycobacterium tuberculosis via rupture of Ghon complexes (“tubercules”)

48
Q

How long after a primary TB infection may a secondary TB infection occur?

Reactivation is dependent on what?

A

May occur years after primary infection

Reactivation is dependent on overall health and any underlying conditions

49
Q

What types of tests are used to diagnose TB?

A
  1. Direct tests
    a. acid-fast staining + microscopy
    b. growth of M.tb in lab culture
    c. NAATs (PCR)
  2. Indirect tests
    a. Tuberculin skin test (Mantoux test)
    b. Interferon Gamma Release Assay (IGRA) > detects presence of Th cells due to M.tb
50
Q

What are direct tests used for in diagnosing TB?

A

They’re used for looking for M.tb bacteria in resp tract specimens (i.e. they’re looking for an ACTIVE infection)

51
Q

What are indirect tests used for in diagnosing TB?

A

They’re used to measure EXPOSURE to M.tb bacteria (i.e. they can only tell you if you’ve been exposed to M.tb; they can’t be used to indicate an active infection)

52
Q

You have a

  1. negative PCR and culture
  2. positive IGRA/skin test

What can this say about your disease status? (2 possibilities)

A

The bacteria have been cleared by the immune sys > no symptoms and no transmission

OR

The bacteria are being ctrled by the immune sys via Ghon complexes (“tubercules”) > reactivation can occur (which would make the PCR and culture positive)

53
Q

You have a

  1. positive PCR and culture
  2. positive IGRA/skin test

What does this say about your disease status?

A

Tuberculosis is ACTIVE (M.tb is growing inside you) > symptomatic and transmissible infection

54
Q

How was TB treated pre-1950s?

A

Long-term care in sanatorium/clinic

55
Q

How is TB treated now?

A

Anti-Mycobacterial drugs that must be given continuously for 6-9 months of daily treatment

56
Q

Minimum infectious dose of M.tb?

A

~10 bacterial cells (= VERY HIGH infectious potential)

57
Q

T or F: The TB vaccine is highly effective at preventing TB

A

F

58
Q

Despite their low effectiveness, in what types of settings are TB vaccines usually used?

A

Settings where the incidence of TB is high

59
Q

What kinds of ppl are at higher risks for TB (re)infection? (3)

A
  1. Immunocompromised (esp HIV/AIDS)
  2. Lower SES
  3. Those routinely in contact w/ inds who have TB
60
Q

Since patient compliance is s.times a problem with proper drug treatment for TB, what is usually done?

A

Directly observed treatment

MCIM 224 (25 decks)

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