Microbiology for Midterm Flashcards
What are the normal biota of the CV system?
Nothing - privileged site
What valves does IE most often occur with?
Mitral or Aortic
What are the signs and symptoms associated with IE?
Fever, anemia, abnormal heartbeat, abdominal/side pain, looks ill, petechiae, septic emboli, Roth’s spots, splinter hemorrhages
Subacute - enlarged spleen
How can dental procedures lead to infectious endocarditis?
Strep. viridian’s usually resides in the normal flora of the mouth so a dental procedure could give them a good area to enter the bloodstream
What does viridians do on blood agar plates?
Alpha-hemolytic (green)
-Common among normal flora, particularly in the oral cavity
What organisms typically cause acute endocarditis?
Staph aureus
Sometimes: Strep pyogenes
What is the clinical course of acute endocarditis?
- Hectically febrile (fever comes and goes)
- Rapidly damages cardiac structures
- Seeds infection in distal sites through sepsis
- If untreated, progresses to death within weeks
What organisms typically cause subacute endocarditis?
Strep viridans, Enterococcus
What is the clinical course of acute endocarditis?
- Indolent (slow, little pain) course
- Causes structural damage slowly
- Rarely seeds infection at distal sites
- Gradually progressive
Gamma hemolysis?
Doesn’t damage RBC, no color change, but growth
Alpha hemolysis?
- Strep. viridans.
- Partial degradation of RBC
- Color change/oxidation and green
Beta hemolysis?
- Group A strep (streptoccus pyogenes)
- Completely destroys RBCs
What are the portals of entry for IE?
- Oral cavity
- Skin
- Upper respiratory tract
What are the areas of local infection for IE?
- Mitral valve
- Tricuspid valve (injection drug use)
- Prosthetic valves
What groups have the highest rates of IE?
IV drug users
How to make initial IE diagnosis?
Patient presenting with fever and valvular abnormalities
How do you make further IE diagnosis?
- Screen blood cultures
- Look for otherwise-unexplained arterial emboli & cardiac valvular incompetence
What is the fever usually in subacute infectious endocarditis?
Less than 103F
What is the fever usually in acute infectious endocarditis?
Between 103-104F
How do you know you have a positive result with the Duke Criteria?
- 2 major criteria are met
- 1 major and 3 minor criteria are met
- 5 minor criteria are met
What are the two Duke major criteria?
- Positive blood culture (contamination issues) All must have same organism
- Evidence of endocardial involvement
What are the 5 Duke Minor Criteria?
- Predisposition (heart condition or injection drug use)
- Fever above 38C (100.3F)
- Vascular phenomena (arterial emobli, Janeway lesions - nontender, erythematous lesions on hands and soles)
- Immunological phenomena (Osler node - painful, red raised lesions on hands and feet, Roth;s spots, rheumatic fever, etc.)
What drugs should you use to treat Acute IE?
Gear treatment toward staph infection with concern for MRSA or coat-neg. staph
- Nafcillin or Oxacillin +/- Gentamicin or Tobramycin
- Vancomycin + Gentamicin
What drugs should you use to treat Subacute IE?
Gear treatment toward strep infection.
- Ampicillin/Sublactam + Gentamicin or Tobramycin
- Vancomycin + Ceftriazone or Gentamicin/Tobramycin
What drugs should you use to treat IE with penicillin allergy patients?
- Cephalosporins (3rd to 5th generation) or carbapenems
2. Vancomycin
What is the most common cause of IE?
Staph. aureus
- Majority of IE in drug abusers
- Usually preceded by bacteremia
What are two traits of Staph aureus?
Gram +, facultative anaerobe
What are the virulence factors of Staph. aureus?
- Biofilm formation
- Capsule
- Adhesins
- Secreted enzymes
- Hemolysins
- Pathogenicity islands (contain info. for methacililn resistance)
What is the most common infectious agent of the skin and surgical wounds? What can it cause?
- Staph. aureus
- Impetigo, cellulitis, folliculitis, furuncles, carbuncles
How does Staph aureus colonize the skin and evade host defenses?
- Protein A (binds Fc portion of IgG)
- Coagulase (forms fibrin coat around the organism)
- Hemolysins and leukocidins (destroy RBCs and WBCs)
Fact tree for Staph aureus?
Bacteria Gram + Cocci Coagulase + Catalase +
What virulence factors does Staph. aureus have for deep tissue invasion?
- Hyaluronidase (breaks down C.T.)
- Staphylokinase (lyses formed clots)
- Lipase (breaks down fat)
What is the 2nd major cause of endocarditis?
Streptococcal species (viridian’s)
What does Step Viridans infection usually involve?
Underlying mitral valve damage (rheumatic fever, etc.) which provides the site for bacterial colonization
What is Strep. Viridan’s most important virulence factor?
-It can produce dextran for glycocalyx formation and surface adhesion proteins that assist colonization
Fact tree for Strep. mutans?
(viridans) Gram + Cocci Catalase - Alpha-hemolytic Bacitracin resistant
What is the third major cause of IE?
Enterococcus species
When do people usually get Enterococcus IE?
Genitourinary procedures in older men or obstetric procedures in younger women
What is enterococci usually resistant to?
penicillins and carbepenems
What are the virulence factors of Enterococci?
Pili
Surface proteins
Extracellular enzymes (like proteases and hyaluronidases)
What different infections does Strep. pyogenes cause?
Impetigo, Erysipelas, Cellulitis, Toxic-shock syndrome, Necrotizing fasciitis
Fact tree for Strep. pyogenes?
Gram + Cocci Catalase - Beta-hemolytic Bacitracin sensitive
What are important virulence factors for spread of Strep. pyogenes?
- Streptokinase (converts plasminogen to plasmin)
- M protein (resists phagocytosis)
- Hyaluronidase (breaks down connective tissue)
- DNase (digests DNA)
- Streptolysin O (destroys RBCs)
- Streptolysin S (destroys WBCs)
- -Streptokinase and hyaluronidase are encoded by a lysogenized prophage
What exotoxins does strep. progenies release in TSS and necrotizing fasciitis?
TSS - Exotoxin A (superantigen)
Nec. fasciitis - Exotoxin B (protease)
What does RHD usually follow?
Strep. pyogenes pharyngitis in genetically predisposed individuals
What is Rheumatic Heart Disease?
Type II hypersensitivity
-Damage to hear muscle and valves is attributed to autoantibodies (antibodies to bacterial antigens that cross-react with meromycin in the heart)
What is a usual clinical indicator of RHD?
Mitral stenosis following pharyngitis with a rash
What are three risks for RHD?
- Strep throat infection (prolonged/untreated)
- Prior case of rheumatic fever
- Age 5 to 15 yrs old
What are the most common symptoms of RHD?
- 2-4 wks after strep infection
- Pain, swelling in large joints
- Fever
- Weakness
- Muscle aches
- SOB
- Chest pain
- Nausea and vomiting
- Hacking cough
- Circular rash
- Lumps under the skin
How do you treat rheumatic heart disease?
- Penicillin Abx
- Aspirin
- Corticosteroids
- Rest
How do you prevent RHD?
- Treat strep right away with Abx.
- Sore throat more than 24 hours = consult physician
What is myocarditis? What organisms usually cause it?
- Inflammation of the myocardium (middle layer of heart wall)
- Usually viral (Cox B & Adenovirus (children))
- Chest pain, heart failure, abnormal heart rhythms possible
What are the traits of Coxsackievirus B?
Virus ssRNA (+) Group IV Nonsegmented Icosahedral Nucleocapsid Nonenveloped Picornaviridae Enterovirus Coxsackievirus A & B
What is pericarditis usually caused by ?
Acute infection
- Viral infection (Coxsackievirus A & B, Echoviruses and Influenza)
- Summer months
- Chest pain associated with irritated layers of pericardium rubbing against each other
What are typical RMSF symptoms?
Fever, headache, abdominal pain, vomiting, muscle pain, rash may develop but is often absent first few days, never develops in some patients
What is used to teat RMSF? Where is it most prevalent?
Doxycyline
Lower midwest to the east coast
What are the three hallmark signs of RMSF?
Rash, fever, headache
How is RMSF transmitted?
- Carried in dogs/rodents
- Dermcentor wood or dog tick
- Infects endothelial cells
- Inflammation of endothelial lining of small blood vessels
- Maculopapular rash on palms and soles SPREADING TO THE TRUNK
- Widespread vasculitis –> headache –> CNS changes, renal damage –> may lead to death
What are two obligate intracellular parasites that need ATP?
Chlamydiae & Rickettsiae
