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IDMM > IDMM Week 2 PBL > Flashcards

IDMM Week 2 PBL Flashcards

1
Q

List the etiologic agents for pneumonia (bacterial)

A
  1. Step. pneumoniae
  2. Haemophilus influenzae
  3. Moraxella catarrhalis
  4. Klebsiella pneumoniae
  5. Chlamydia pneumoniae
  6. Mycoplasma pneumoniae
  7. Legionella pneumoniae
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2
Q

Transmission of step. pneumo

A

person to person

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3
Q

Strep. pneumo disease in humans

A
  1. Typical pneumonia–rusty-colored sputum, fever, chest pain, SOB, abrupt onset, invasive with lobar extension

other diseases include: meningitis, sepsis, otitis media in kids, sinusitis

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4
Q

Strep. pneumo virulence mechanism

A
  1. capsule–resists phagocytosis but is antigenic (encapsulated organism)
  2. toxins–secretes many toxins including pneumolysin (binds to cholesterol in host-cell membrane)

colonized in oropharynx

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5
Q

What is the most common cause of pneumonia?

A

Strep. pneumoniae

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6
Q

Describe strep. pneumoniae:

  1. gram stain
  2. aerobic or anaerobic?
  3. catalase?
  4. other
A
  1. Gram + cocci
  2. facultatively anaerobic
  3. catalase +
  4. alpha-hemolytic, requires host for survival, activates complement–>inflammation
    * *IgA protease
    * *Teichoic acid: mimics human protein so may not be recognized as foreign–> DIC
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7
Q

Describe haemophilus influenzae

A

Gram - rod
facultative anaerobe
reservoir in humans only (blood loving)

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8
Q

What type of pneumonia is associated with H. influenzae?

A

ASPIRATION pneumonia

TYPICAL pneumonia

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9
Q

transmission of H. influenzae

A
  • respiratory

- (opportunistic infections when have influenza viral infection)

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10
Q

H. Influenzae disease in humans

A
  • *encapsulated**
  • HiB is most common cause of MENINGITIS in infants
  • acute epiglottitis
  • septic arthritis (infants)
  • sepsis (asplenic patients)
  • TYPICAL pneumonia
  • *nonencapsulated**
  • otitis media
  • sinusitis
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11
Q

What are the symptoms of typical pneumonia

A 
cough
chest pain
fever
dyspnea
productive (even bloody) sputum
increased WBC
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12
Q

H. influenzae virulence mechanism

A
  • Capsule: 6 types (b is most virulent)
  • attachment pili
  • IgA protease
  • LPS
  • binds to sialic acid
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13
Q

Describe characteristics of moraxella catarrhalis

A
  • gram - rods
  • oxidase -
  • aerobic
  • needs host for survival
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14
Q

Type of pneumonia seen with M. catarrhalis

A

Aspiration pneumonia (Typical_

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15
Q

Transmission of M. catarrhalis

A

respiratory

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16
Q

Disease in humans: M. catarrhalis

A

-Typical pneumonia (aspiration)
especially in elderly and those with COPD
-otitis media
-sinusitis, bronchitis

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17
Q

M. Catarrhalis virulence factors

A
  • thin CAPSULE
  • virulent strains are serum resistant
  • beta-lactamase producing strain hemagglutinates RBCs
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18
Q

Klebsiella pneumoniae characteristics

A
  • enteric
  • gram - rods
  • lactose fermenter
  • non motile
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19
Q

type of pneumonia seen with K. pneumoniae

A

typical/aspiration pneumonia

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20
Q

K. pneumoniae transmission

A

water borne

GI tract

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21
Q

K. pneumoniae disease in humans

A 
Typical pneumonia (aspiration) with signs of lung necrosis and BLOODY SPUTUM, especially in alcoholics and IC
--nosocomial UTIs and sepsis as well
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22
Q

K. pneumoniae virulence factors

A
  • CAPSULE: phagocytosis resistant
  • LPS
  • serum resistant
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23
Q

Chlamydia pneumoniae characteristics

A

-gram indifferent intracellular pathogen
-OBLIGATE intracellular bacteria
(steals ATP from host with ATP/ADP translocator)

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24
Q

Chlamydia pneumoniae transmission

A
  • respiratory

- human to human

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25
Q

Chlamydia pneumoniae disease in humans

A

ATYPICAL pneumonia, especially in young adults

  • strongly associated with atherosclerosis
  • arthritis
26
Q

Describe the symptoms of atypical pneumonia

A

differs from typical in that it is:

  • dry
  • no fever
  • “not as sick”
  • DECREASED WBC
27
Q

Chlamydia pneumoniae virulence factors

A
  • “elementary body” (EB) infects cells–converts to “initial body” (IB)
  • IB can reproduce (uses ATP from host)–IB transforms back into EB–>leaves and infects other cells
  • attaches to columnar epithelial cells
  • binds to sialic acid
28
Q

Mycoplasma pneumoniae transmission

A

respiratory (droplet)

human, enviro and animal carries

29
Q

characteristics of M. pneumoniae

A
  • NO CELL WALL
  • amorphous shape
  • needs host for survival
  • needs CHOLESTEROL in membrane
  • facultative anaerobe
30
Q

M. pneumoniae disease in humans

A
  • “walking pneumonia”/Atypycal pneumonia—fever with dry, nonproductive couch, chills common
  • tracheobronchitis
  • sputum–monnuclear cells, fewer PNMs than bact pneumo
31
Q

Legionella pneumonia characteristics

A
  • gram - bacilli
  • anaerobia
  • facultative intracellulat parasite–inside alveolar macrophages
32
Q

Leigionella pneumonia transmission

A

humans and natural WATER environment

AC systems!!

33
Q

Legionella pneumoiae disease in humans

A
  1. PONTIAC fever: in healthy hosts, allergy like reaction; self limiting within one week
  2. Legionnaires disease: starts with non-respiratory and progresses to respiratory (es in 50 yo males and smokers)
  3. Atypical pneumonia
34
Q

Legionella pneumoniae virulence factors

A
  1. inhibits phagolysosomal fusion after being eated alive by macrophages
    - CAPSULE
    - motile
    - hemolysin
35
Q

Which causes of pneumonia are atypical?

A

Chlamydia/mycoplasma/leigionella pneumo

36
Q

Describe facultative intracellular growth in primary TB

A
  • inhaled bacteria causes local infiltration of neutrophil and macrophages–no acquired immunity
  • SULFATIDES (virulence factor) prevent phagosomes from fusing to lysosomes and thus allows phagocytosed bacteria to replicated in the macrophage
  • bacteria travel through the lymphatics and blood to spread to distant sites
37
Q

What is the virulence factor that allows primary TB to replicate in the macrophage

A

sulfatides

38
Q

Describe the role of cell mediated immunity in primary TB infection

A
  • some macrophages are able to cause destruction of phagocytosed bacteria and present antigens to helper T cells to establish acquired immunity
  • sensitized T cells enter the circulation in search of bacteria: LYMPHOKINES, which serve to attract and activate macrophages, are released upon antigen encounter
  • activated macrophages destroy the bacteria, but also cause local destruction and damage to lung tissue–CASEOUS NECROSIS (granular creamy cheese)
  • sites of caseous necrosis are surrounded by macrophages, fibroblasts and collagens and frequently calcify–bacteria are essentially “walled off” but remain viable
39
Q

Is primary TB usually symptomatic or asymptomatic

A

asymptomatic

40
Q

In which populations does symptomatic primary TB occur

A

often occurs in children, the elderly or the immunocompromised

41
Q

What are overt symptoms of primary TB

A

large CASEOUS GRANULOMAS developed in the lungs or other organs

in the lungs, the caseous material eventually liquifies, is extruded out via the bronchi and leaves behind cavitary lesions

42
Q

How is TB spread

A

via aerosolized droplets which land in areas of the lung that receive the highest air flow–middle and lower zones

43
Q

What is another name for a TB granuloma

A

tubercle

44
Q

What are calcified TB tubercles called

A

Ghon foci

45
Q

What is a Ghon complex

A

a Ghon focus accompanied by a perihilar lymph node calcified granulomas

46
Q

What leads to reactivation TB (secondary TB)

A

depression of the immune systm–infection can occur in any of the organ systems seeded during primary infection

47
Q

List possible sites of TB reactivation

A
  • pulmonary TB
  • pleural and pericardial infection
  • lymph node involvement
  • kidney
  • skeletal
  • joints
  • CNS
  • miliary TB (disseminated—like a shotgun blast)
48
Q

How does reactivation TB present clinically

A 
chronic low grade fever
night sweats
weight loss 
productive cough 
hemoptysis
49
Q

Where does TB get its historical name “consumption”

A

from the weight loss associated with reactivation TB

50
Q

Where is the most likely site of TB reactivation

A

Upper Right lobe of Lung due to higher O2 concentration

51
Q

What is the risk of reactivation in all people? in HIV+?

A

10 % in all people for lifetime; in HIV + its 10% per year

52
Q

What is the basis for the tuberculin skin test?

A

requires a T cell mediated delayed type hypersensitivity reaction–becomes positive approximately 2-10 weeks post-infection

53
Q

What is the procedure for a tuberculin skin test

A

inject tuberculin under the skin–if a red welt with diameter of 10 mm or more forms around the injection site within 72 hours, the patient MAY have been previously exposed to TB

54
Q

Does a positive tuberculin skin test mean the person has active disease?

A

No. A positive test could mean:

  1. the patient was previously exposed to TB
  2. exposed to a related bacteria
  3. previously vaccinated with the BCG vaccine
  4. the patient has latent (not active) disease
  5. the patient has active disease
55
Q

Does a negative tuberculin skin test rule out active disease?

A

No–some patients may simply have fewer T cells to respond to the injected antigen

56
Q

Should a definitive diagnosis of TB rely on the tuberculin skin test?

A

No

57
Q

How useful is the BDG vaccine?

A

around 50%

used in developing countries but not in Canada

58
Q

What tests may be performed in the investigation of pneumonia?

A
  1. CXR: not able to diagnose specific organism with radio patterns
  2. Gram stain and culture of sputum
  3. antigen tests: 2 commercially available tests for pneumococcal and certain Legionella Ags; rapid test for influenza; direct fluorescent antibody test for influenza and RSV
  4. PCR: available for L. pneumophila and mycobacteria
  5. Serology
  6. Blood cultures: not used rigorously anymore for hospitalized patients with CAP
59
Q

What tests may be ordered in the diagnosis of TB?

A
  1. PPD skin test: reveals if person has been INFECTED with M. mycobacterium tuberculosis
  2. Quantiferon-TB: bloos test that measured IFN gamma levels produced in whole blood in response to addition of specific TB antigens; specific for M. tuberculosis, not positive in people with BDG vaccine
  3. CXR: pick up isolated granuloma, Ghon focus, Ghon complex, old scarring in upper lobes, or active TB pneumonia
  4. Sputum acid fast stain and culture: when acid fast stain or culture is positive you have an active pulmonary infection
60
Q

What is the mechanism of the PPD skin test for TB

A
  • after induction of cell mediated immunity against M. TB, any additional exposure will result in localized delayed type hypersensitivity reaction
  • inject intradermally purified protein derivative (PPD) which contains antigenic particles from killed M. TV–if positive, results in localized skin welling and redness
  • macrophages in skin take up antigen, carry it to T cells, T cells move to skin site, release cytokines to activate macrophages

IDMM (29 decks)

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