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Module 3: CPR > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is the #1 circulatory system infection?

A

Infective Endocarditis - infection of endothelial sites in the heart

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2
Q

What is the two highest causes of Infective Endocarditis?

A
  1. Bacteria
  2. Yeast
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3
Q

What are the ways of increasing risk of infective endocarditis?

A

Bacterial Source + Susceptible Host

  • Bacterial Source*s:
  • Breach of barriers taht separate us from normal flora (gut, mouth)
  • Infection elsewhere in body that seeds the blood (indwelling vascular devices, abscessess, pyelonephritis)
  • Organisms introduced during surgery or through IV drug use
  • *Causes of Susceptible Host_ _Risk:**
  • Preexisting valve damage (congenital defects, scar tissue)
  • Native, healthy valves attached by aggressive microbe
  • Prosthetic replacement valves
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4
Q

What populations are most at risk for Infective Endocarditis?

A
  1. IV drug users
  2. Prosthetic valve replacement (immediately after surgery; after some time their risk is same as native valve)
  3. Native valve infection
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5
Q

What are risk factors for infective endocarditis?

A

IV drug use
Mitral valve prolapse
Congenital or Degenerative valve disease
Poor dentition and oral hygiene
Genitourinary manipulations or bowel surgery
Prosthetic heart valves
HIV (reflects association with IV drug use AND invasive therapeutics)
Long-term hemodialysis
Rheumatic heart disease (#1 predisposing risk factor in developing world)

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6
Q

What are characteristics of Group A Strep?

A

Gram + Cocci

Beta-hemolytic

Catalase negative

Bacitracin sensitive

Causes impetigo, Strep Throat, and rheumatic fever

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7
Q

What is rheumatic heart disease?

A

Caused by untreated infection of Group A Strep

M-Protein (helical anti-phagocytic protein) on surface of Group A Strep is anti-phagocytic due to molecular mimicry

Engenders anti-cardiac antibody responsible for deposits and thickening of leaflets and RHD

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8
Q

What is the pathology of infective endocarditis?

A

Primary lesion = vegetation

  • A collection of patelets, fibrin, microorganisms and inflammatory cells
  • Generally occurs on valves, may also occur at site of septal defect, on chordae tendinae, or mural endocardium
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9
Q

What are the three types of bacteremia?

A

Transient: bacteria introduced into blood stream and readily cleard w/o evoking a detectable inflammatory response

Intermittent: spread of infection from some extra-vascular site; results in fever, inflammatory response

Continuous: seeded into blood streem from site of infection within circulatory system

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10
Q

What is Acute Endocarditis?

A

Fulminant Disease
(occuring suddenly, rapidly, and with great severity or intensity)

  • Fever, chills
  • Pronounced heart murmur
  • Symptoms of stroke
  • Clinical signs of embolic infection
  • Frequently healthy valves are affected

–Often seen in IV drug users–

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11
Q

What is sub-acute endocarditis?

A

Gradual onset

  • Fatigue, malaise
  • fever
  • night sweats, weight loss
  • cough
  • symptoms of congestive heart failure
  • usually assoc. with preexisting valve disease
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12
Q

What are clinical signs of endocarditis?

A

- Splinter hemorrhages under fingernails or toenails (result of infection disseminating to extremeties)

- Conjunctival petechiae

- Osler’s nodes: tender, subcutaneous nodules, oftten in pulp of digits or thenar eminence

- Janeway’s Lesions: nontender erythematous, hemorrhagic, or pustular lesions, often on palms or soles of feet

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13
Q

Why does IE predominantly affect the LEFT side of the heart?

A
  1. Relatively higher pressures on L side produce more turbulent flow across mitral and aortic valves; predisposing them to endothelial damage
  2. Relatively higher O2 content of L side circulation more supportive of bacterial growth
  3. More common congenital and acquired lesions of L heart valves
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14
Q

What increases chances of right sided endocarditis?

A

Associated with IV Drug use
(Staph Aureus, usually)

Occurs in tricuspid valve defects as well

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15
Q

What are complications of IE

A

Intracardiac Damage:
Permanent valvular damage
Perivalvular damage
Congestive Heart failure

Extracardiac Damage:
Seeding of other organs with infective agent
Splenic, renal abscesses
Meningeal or brain abscesses

Vascular Damage:
“Septic Emboli”
Stroke-like symptoms
“Mycotic” aneurysm

Immune Complex Disease (Type III):
Glomerulonephritis

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16
Q

What are major bacterial causes of endocarditis?

A 
Native Valve Endocarditis:
**Oral flora or GI flora (subacute)
 Staph aureus (acute)**

Prosthetic Valve endocarditis:
Early = Staph epidermidis, Staph aureus
Late - endogenous oral or GI flora

Intravenous drug abuse endocarditis:
Staph aureus
Candida Albicans

17
Q

What are the three hemolytic patterns and how do they appear in a gel?

A

Alpha = green

Beta = clear/yellow (complete hemolysis)

Gamma = none

18
Q

What are characteristics and examples of oral streptococal species?

A
  • Mostly alpha hemolytic
  • Termed “viridans” group strep (green)
  • Cause dental caries, biofilms on the teeth (plaque)
  • Not highly pathogenic
  • Major species:
    Strep sanguis
    Strep mitis
  • Strep mutans
19
Q

What oral flora (associated with peridontitis) are also common in IE?

A

Gram Negative Bacilli

HACEK:

Haemophilus parainfluenze

Aggregatibacter acetomyecetecomitans and aphophilus

Cardiobacterium hominis

Eikenella corrodens

Kingella kingae

20
Q

What are characteristics of Staph epidermidis?

A
  • Ubiquitous on skin, surfaces, hospital settings
  • Not as virulent as S. aureus
  • Coagulase negative
  • White colonies, non-hemolytic
  • Often multiple drug resistance
  • Common in nosocomial post-surgical infections (esp. prosthetics)
21
Q

What are characteristics of Staph aureus?

A
  • Gram + cocci in clusters
  • Beta hemolytic
  • Catalase +
  • Coagulase +
  • Common on skin (often carried in nose)
  • Causative agent of boils, folliculitis, impetigo, severe soft tissue and bone infections, TSS, as well as bacterial endocarditis
22
Q

What are Endocarditis bacteria associated with GI cancers, urogenital infections?

A
  • Enterococcus
  • Strep bovis
  • E. coli
  • Yeast
  • Other gram - bacilli
  • often gamma hemolytic
23
Q

What are characteristics of Enterococcus?

A
  • Group D bacteria
  • Tolerant of bile salts (hence gut niche; “entero”)
  • Gamma Hemolytic
  • Resistant to 6.5% NaCl
  • Hydrolize bile exculin (BE+)
  • Lead Species:
    E. faecium
    E. faecalis
24
Q

What is required to make a diagnosis of infectous endocarditis?

A
  • Lab data (esp. repeat + blood cultures)
  • Positive echocardiogram
  • Risk factors
  • Fever
  • Vascular and immunologic signs (Splinter hemorrhages, petechiae, Oslar’s nodes, etc)
25
Q

Why are repeat positive blood cultures essential in infectious endocarditis diagnosis?

A

It is easy to get false positives from skin contaminated samples

  • repeat blood collections reduce risk of false +
26
Q

How is blood collected for endocarditis blood culture samples?

A
  • Decontaminate skin with iodine-based antiseptic
  • palpate vein with sterile gloved finger
  • collect adequate volume (1:10 dilution in broth culture medium)
  • decontaminate bottle tops and transfer sample to broth

–> all done to prevent skin or environmental bacteria from contaminating sample

27
Q

What is the treatment for Infective Endocarditis?

A
  1. Determine antimicrobial susceptibility pattern of agent
  2. Select bactericidal drug (or combo of drugs)
  3. Administer IV antibiotics for 4-6 weeks (peripherally inserted central cath) PICC line for at home treatment
  4. Surgical replacement of damaged valve or infected prosthetic
28
Q

What are two causes of non-infective endocarditis?

A

- Marantic - “wasting”
(nonbacterial thrombotic endocarditis)
Mucin secreting tumors cause sticky deposits and platelet aggregates on valves

- Libman-Sacks Endocarditis
associated with Lupus (SLE)
autoantibody depositions on valves

Module 3: CPR (10 decks)

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