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Module 10 > Infectious Aetiologies of Heart (Bacterial + Viral) > Flashcards

Infectious Aetiologies of Heart (Bacterial + Viral) Flashcards

1
Q

what is the pathogenesis of infective endocarditis

A

need two things to happen:

  1. endothelial damage to valve (trauma, turbulence, metabolic change)
  2. mucous membrane trauma

platelets + fibrin aggregates try to repair the damage –> non-bacterial thrombotic vegetation (NBTV) forms and bacteria colonize and stick to this

  • bactiera multiply –> becuase of fibrin deposition the bacteria is protected by neutrophil destruction
  • bacteremia: constantly shed from vegetation –> positive blood cultures as vegetation gets larger –> embolize and break off and go to vital organs (brain –> stroke)
  • heart valve becomes dysfunctional and destroyed
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2
Q

what is acute endocarditis

A

major pathogens

rapid course and onset

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3
Q

what is chronic endocarditis

A

(sub-acute)

less virulent pathogens

indolent course and onset

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4
Q

what is seen in endocarditis

A
  1. bacteria in blood and bacteremia continuous
  2. cardiac pre-disposition often –> congential damage/diseased valves –> subvalvular aortic stenosis –> mitral and aortic most affected
  3. new heart murmur
  4. fatal if not treated (antibiotics) or valve replacement in humans
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5
Q

what valve is this and identify the anatomy

A

the valve leaflets are smooth

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6
Q

what is MSCRAMM

A

microbial surface components recognizing adhesive matrix molecules

adhesin proteins mediate the initial attachment of bacteria to host tissue

fibronectin binding proteins of staphylococci (trauma from skin) and streptococci (mouth or gut)

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7
Q

list the steps that lead to bacterial deposition on the mitral valve

A
  1. endothelial injury
  2. platelet deposition
  3. microbials with MSCRAMMs –> bacterial adhesion to platelet fibronectin and fibrin matrix
  4. adhesion and incorperation of microbials into vegetation –> aggregates that build up on smooth valve and interfere with the mechanical function of the valve (heart murmur)
  5. vegetative lesion, ruptured chordea tendinae
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8
Q

what are the common bacterial causes of IE in dogs

A

>50% of cases caused by streptococci and coagulase positive staphylococci (staphylococcus pseudointermedius adn staph. aureus)

streptococci originate in mouth or gut

rarely due to gram negatives

bartonella

fungi rare in dogs and cats

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9
Q

what bacteria cause endocarditis in cattle

A

Streptococcus bovis

arcanobacteria (trueperella)

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10
Q

what bacteria cause endocarditis in pigs

A

erysipelothrix

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11
Q

what is the pathogenesis of endocarditis

A
  1. normal vascular endothelium resistant to microbial infection and few potentially at risk actually develop infective endocarditis
  2. since low-grade bacteremia occurs freq. a defence mechanism must exist that can eradicate microbes adherent to vegetation
  3. plalelets play a pivotal role in the antimicrobial host defence mechanism (thrombocidins)
  4. damage to the endothelial surface of the heart or blood vessel induces platelet and fibrin deposition, producing a sterile thrombotic vegetation
  5. infective endocarditis is initiated by binding of microbes, discharged in the general circulation from a peripheral site to these vegetations
  6. these microbes become encased further in depositions of platelets and fibrin and multiply
  7. extremely high concentrations of bacteria in the vegetation (10^9-10^11/gram tissue)
  8. hinders antibiotic penetration
  9. organisms may stop multiplying –> making them less susceptible to beta lactams (works on cell wall)
  10. bacterial enzymes destroy valve tissue (holes), rupture chordae tendinae and produce aortic root abscess
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12
Q

what are jet lesions

A

endocarditis is classically associated with jet lesions where blood flowing from ahigh pressure area through an orifice to an area of lower pressure produces a high velocity jet

vegetations are usually found in lower pressure area (atrial surface of mitral valve or the ventricular surface of the aortic valve)

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13
Q

what are the four basic processes once a vegetation is established

A
  1. bacteremia
  2. local tissue destruction
  3. embolization
  4. formation of circulating immune complexes
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14
Q

what pathology is shown here

A

emboli from aortic endocarditis causing infarcts in various organs

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15
Q

what are the pathogenesis of clinical signs of IE (9)

A
  1. valvular insufficiency and congestive heart failure
  2. bacteremia
  3. septic embolization and organ infarction
  4. metastatic infection and myocarditis
  5. immunopathologic sequelae and immune complex deposition
  6. glomerulonephritis
  7. uveitis
  8. polyarthritis
  9. meningitis
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16
Q

how is IE diagnosed (without echocardiogram, with echogardiogram, clinical findings)

A

without echocardiogram all criteria should be met:

  • murmur of recent onset
  • positive blood culture results (preferably with more than one of the same microbe)
  • clinical findings and laboratory data consistent with bacteremia and endocarditis

with echocardiogram:

-aortic or mitral valve

supportive clinical findings:

  • signalment
  • murmur of recent onset
  • weak or hyperdynamic pulse
  • fever
  • limb edema
  • joint swelling
  • lameness
  • limb ischemia
  • limber hyperesthesia
  • inflammatory leukogram
  • positive blood culture
17
Q

what is the suggestive criteria for IE diagnosis

A
18
Q

how is bacteremia identified

A

blood cultures

at least 3 cultures should be obtained from seperate sites within 24 hours

19
Q

what class of antibiotics are used to treat

A

bactericidal

need to sterilize the vegetation

20
Q

what is myocarditis

A

inflammation of heart muscle

21
Q

what is the cause of myocarditis

A

infectious myocarditis in dogs and cats usually results from hematogenous spread of microorganisms to the myocardium or extension of endocarditis lesions to myocardium

viruses, bacteria, protozoa, fungi may be involed

some organisms have tropism for the myocardium

rare in cats

22
Q

what are the bacterial, viral causes for myocarditis in dogs

A

canine distemper virus

canine parvo virus

borrelia burgdorferi

rickettsia rickettsii

23
Q

what are the causes of myocarditis in cattle

A

clostridium chauvoei

listeria

24
Q

what are the causes of myocarditis in pigs

A

encephalomyelitis virus

porcine circovirus 2

25
Q

what are the causes of myocarditis in poultry

A
26
Q

what are the causes of myocarditis in cats

A

bartonella

27
Q

what causes pericarditis

A

infectious pericarditis may result from direct inoculation of organisms into pericardium (penetrating wounds)

extension of infection from adjacent organs such as pleural space or lungs

hematogenous dissemination of viral, bacteria, fungal pathogens to the pericardium

28
Q

how is pericarditis diagnosed

A

sample pericardial fluid for bacterial culture/viral PCR, blood culture for bacteria

29
Q

what are the bacterial, viruses that cause of pericarditis

A
30
Q

what is immune complex glomerulonephritis

A

protein losing nephropathy

immune complex deposition on basement membrane –> antigen antibody reaction activates complement pathway –> damage to glomerular basement membrane

damage sufficient to allow albumin loss –> protein in urine

31
Q

how long is antibiotics given

A

until its bettwe

6 weeks +++ (8-12)

enfrofloxacin/amoxicillin-clavulanate

32
Q

what are acute phase proteins

A

part of innate immune system

raised in inflammation

most sensitive blood test available for detecting inflammation –> much more than WBC

go down as animal gets better

33
Q
A

Module 10 (27 decks)

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