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Microbiology COPY > Exam #7: Bacterial Infections of the Circulatory System > Flashcards

Exam #7: Bacterial Infections of the Circulatory System Flashcards

1
Q

What is bacteremia?

A

Bacteria in the blood

*Note that this is NOT uncommon & can occur with minor things like brushing your teeth

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2
Q

What are the most common sources of bacteremia?

A

1) UTI
2) Respiratory Tract Infection
3) Soft tissue trauma

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3
Q

What causes transient bacteremia?

A

Dental extraction; this is when there is a high concentration of bacteria over a short period of time

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4
Q

What causes intermittent bacteremia?

A
  • Pneumococcal pneumonia
  • Gram-negative sepsis
  • Intra-abdominal abscess

This is when bacteremia occurs with irregular patterns i.e. there are waves of bacteremia

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5
Q

What causes continuious bacteremia?

A
  • Infective endocarditis (low level bacteremia)

- Catheter bacteremia (high level bacteremia)

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6
Q

What is sepsis?

A

Systemic inflammatory response syndrome (SIRS) that has a proven or suspected microbial etiology

*Bacteremia can lead to sepsis, but it is NOT required for sepsis

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7
Q

What is the definition of SIRS?

A

Two or more of the following:

  • Fever or hypothermia
  • Tachypnea
  • Tachycardia
  • Abnormal WBC count (i.e. leukocytosis, leukopenia, or >10% bands)
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8
Q

What is severe sepsis?

A

Sepsis PLUS one or more signs of organ dysfunction:

  • Reduction in urine output
  • Mental status change
  • Systemic acidosis
  • Hypoxemia
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9
Q

What is septic shock?

A

Severe sepsis + hypotension

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10
Q

What is refractory septic shock?

A

Septic shock that last for more than an hours & does NOT respond to fluid & pharmacologic treatment

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11
Q

What is multiorgan failure?

A

Dysfunction of >1 organ & the development of disseminated intravascular coagualtion (DIC)

*IL-6–>TNF-a–>DIC

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12
Q

What causes the majority of severe sepsis cases?

A

Bacterial infection

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13
Q

Is bacteremia required for sepsis?

A

No

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14
Q

What are the risk factors for sepsis?

A
  • Indwelling catheters
  • Mechanical devices
  • Immunsuppression
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15
Q

Outline the pathophysiology of classic sepsis.

A
  • Classically, sepsis is induced by Gram (-) bacteria that release LPS/ Lipid A into the circulation
  • Binds CD14 & TLR4 that activates the immune system
  • Causes inflammation & can induce septic shock via TNF-a, IL-1, & IL-6
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16
Q

How do Gram (+) bacteria induce sepsis?

A
  • Peptidoglycan

- Exotoxins

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17
Q

How does S. aureus lead to the development of sepsis?

A

TSST-1= superantigen that stimulates T-cell activation & release of cytokines

  • Previously most commonly seen with tampons
  • Now most commonly seen with wound infection
18
Q

How are staphylococcus & streptococcus differentiated in the lab?

A

Catalase

19
Q

How does streptococcal toxic shock sydrome differ from S. aureus?

A

Bacteremia is present in strep.

20
Q

How does Strep produce toxic shock syndrome?

A
  • GAS (s. pyogenes) releases pyogenic exotoxins (Spe A, B & C) that are superantigens
  • Stimulates T-cell activation & release of cytokines
21
Q

How is sepsis diagnosed?

A

1) Symptoms
2) Blood cultures– 40-70% will be positive for bacteria
3) 95% of cases of infective endocarditis will yield positive cultures

*Note that in bacteremic patients without endocarditis, it is important to take multiple blood cultures over time

22
Q

Will patients undergoing antibiotic therapy have positive blood cultures?

A

No

23
Q

How is sepsis treated?

A 
Hypotension= IV fluid 
Hypoxia= ventilator 
DIC= transfusion or heparin

*Bacterial infection= antibiotics

24
Q

What antibiotics are used to treat sepsis with an unknown bacterial etiology?

A

Vancomycin & gentamicin

25
Q

What is infective endocarditis?

A

Inflammation of the innermost layer of tissue that lines the chambers of the heart

26
Q

What is acute endocarditis? List the characteristics of acute endocarditis. What organism typically causes acute endocarditis?

A

S. Aureus causes Acute endocarditis

  • High fever
  • Rapid damage to cardiac structures

*If left untreated, acute endocarditis can lead to death within weeks

27
Q

What is subacute endocarditis? List the characteristics of subacute endocarditis. What organism typically causes subacute endocarditis?

A

S. viridans causes subacute endocarditis

  • Low grade fever
  • Night sweats
  • Weight loss
  • Vague constitutional symptoms
  • Slower damage to the heart

*If left untreated, it can progress to dead in weeks to months

28
Q

What are the clinical manifestations or signs of endocarditis?

A
  • New heart murmur
  • Splenomegaly
  • Various skin lesions
  • Retinal lesions
29
Q

What are splinter hemorrhages?

A

1-2mm brown linear streaks in the nail bed associated with endocarditis

30
Q

What are roth spots?

A

Retinal hemorrhages associated with endocarditis

31
Q

What are Janeway lesions?

A

Painless lesions on palms or soles of feet associated with endocarditis

32
Q

What are Osler nodes?

A

Painful subcutaneous nodules in the pads of the digits associated with endocarditis

*Thought to be caused by vasculitis or septic embolization

33
Q

What bacteria are associated with infective endocarditis?

A

S. viridans= less virulent & associated with subacute endocarditis

S. aureus= more virulent & associated with acute

34
Q

List the characteristics of S. aureus.

A

Gram + cocci in clusters
Catalase +
Coagulase +

35
Q

List the characteristics of S. viridans.

A

Gram + cocci in chains
a-hemolytic
Optochin resistant
No Lancefield group

36
Q

Specifically, what 2 S. aureus species are most associated with subacute endocarditis?

A

S. mitis

S. salivarius

37
Q

What are the risk factors for infective endocarditis?

A

1) Susceptible cardiovascular substrate i.e. patient with prosthetic heart valve or previous damage to heart valve
2) Source of bacteremia
3) IV drug use
4) HIV (esp. HIV + IV drug use)
5) Immunosuppressed with central venous catheter
6) Hemodialysis

38
Q

Describe the pathophysiology of endocarditis.

A
  • Cardiac abnormalities create sites for bacterial attachment
  • Vegetations are formed at attachment sites & are composed of platelets, fibrin, bacteria, & inflammatory cells
  • These vegetations can break off an become “septic emboli” that damage brain, kidney, & spleen
39
Q

How is bacterial endocarditis diagnosed?

A

Major criteria:

  • History & physical examination
  • 95% have bacteremia that will test positive with blood culture
  • Imaging evidence of endocardial involvement

*Minor criteria involve identifying risk factors, fever, and skin lesions

40
Q

How is endocarditis treated?

A

1) Aggressive initial antimicrobidal therapy

2) Prolonged antimicrobial therapy

Microbiology COPY (49 decks)

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