infectious heart disease Flashcards
Infectious endocarditis
Uniformly fatal if untreated
Predisposing factors: vlavulat heart disease (congenitial defects rheumatic disease
Prosthetic valves damage
IV drug use
Properties of successful IE pathogens
able to survive antimicrobial components of Serum
Able to adhere to endocardium
Dextran (exopolysaccharide)- viridans streptococci
Adhesins (surface proteins) that mediate attachment to platelets and fibrin–viridans streptococci
Fibrinogen-binding adhesins- S aureus
Most common etiologic agents
NORMAL MICROBIOTA
Staphylococcus aureus- colonizer of anterior nares, manifests as acute IE often with complications
Coagulase-negative Staphylococci (S epidermdis) colonizes of skin, prostheic valve endocarditis
Viridans streptococci (S sanguis, S mutans, S mitis) (oral cavity colonizer, S gallolyticus bovis --colonic lesions Nutritionally variant strep
Rare agents: HACEK (haemophilus, actinobacillus, cardiobacterium, eikenella, kingella)- gram neg bacteria
Brucella, coxiella burnetti
Vegitation
Heterogenous matrix of deposited bacteria, platelets, fibrin, matrix ligands, protection from immune cells, bacteria can achieve high densities (limitations on nutrient exchange high cell density-bacteria are not growing rapidly), embolic phenomena
Implications for antibiotic therapy: bactericidal activity, parental admin for sustained activity, prolonged therapy required
2 requirements for ineffective endocarditis
A bug that sticks: majority of infections related to Staphylococcus aureus (bacteria which is very capable of attaching to and colonizing abnormal valve tissue)
Something to stick to: Abnormal heart valves or prosthetic device (suitible site for bacterial attachement and colonization)
Fatal if left untreated- evn with treatment mortality 20%, one year mortality 40%
Bugs that cause IE
Staphylococci and streptococci account for 80 percent of IE cases: Staph aureus can cause endocarditis in normal heart valves, Staph epidermidis in prosthesis, Viridans in oral health
HACEK group-
IV drugs: staph aureus, pseudomonas, candida
Culture neg: Coxiella, bartonella, brucella
Risk factors IE
common denominators: abnormal heart valves and risk of bacteremia (prosthetic valves, CIEDs, mitral valve prolapse, rheumatic heart disease, complex congenital, mitral regurgitation, aortic stenosis,
Aberrant flow results in platelet-fibrin thrombus on injured endothelium
Bacteria enter bloodstream through skin or mucosal surfaces and adhere to thrombus
Once inside growing thrombus, bacteria resistant to host defenses
Clinical presentation of IE
Acute or subacute onset, fever, heart murmur, chills, sweats, anorexia, malaise, weight loss, noncardiac manifestations,
Noncardiac manifestation- embolic events, splenomegaly, clubbing, petechiae, splinter hemorrhage, oslers nodes (ouch ouch oslers), janeway lesions, roths spots
Anemia, leukocytosis, microscopic heaturia, elevated ESR and CRP
Duke criteria
Major: Typical organism from 2 separate blood cultures, organism from persistently positive blood cultures, positive for serology (C, burnetti)
Evident of endocardial involvement (new valvular regurgitation, positive echocardiogram)
Minor: predisposition, fevre, vascular phenomena, immunologic phenomenoa,
Therapy for native valve endocarditis (6 wks)
Organisms are inaccessible to host defenses, metabolically inactive, must kill every bacterium in vegitation
Therapy must be bactericidal, prolonged weeks,
Oxacillin sensitive (staph aureus or CoNS), MSSA- no penicillin allergy or intolerance, IV nafcillin or cefazolin (if allergic vanco or dapto)
Oxacillin resistant MRSA IV vanco or daptomycin
Prosthetic valve endocarditis therapy
Oxacillin sensitive: MSSA: IV nafcillin or oxacillin for 6 weeks with IV Rifampin for 6 weeks, IV gentamicin for 2 weeks
Oxacillin resistant MRSA: IV vancomycin for 6 weeks with IV rifampin 6 weeks, IV gentamicin for 2 weeks
Viridans or enterococcus
Viridans: Penicillin susceptible (MIC
HACEK endocarditis treatment
Ceftriaxone 4-6 wks or ciprofloxacin 4-6 wks