Cardiovascular Infections 2 MICRO Flashcards
Staph aureus is coagulase ______
Positive
Optotchin test is useful to differentiate between ________
Streptococcus
Patient with prosthetic valve endocarditis and the bacteria is coagulates negative. What is the most likely microorganism ?
Staph epidermidis
How to differentiate between staph epidermidis and staph aureus:
- coagulase test
- MSA (mannitol salt agar)
What does coagulase do? (Seen in staph ______ )
Clots plasma by intiating fibrin polymerization;
Staph aureus = coagulase positive
How does being catalase positive add to a microorganism’s pathogenicity?
Catalase breaks down hydrogen peroxide to water and oxygen so it helps them survive the respiratory burst
If the color of the mannitol salt agar changes from red to yellow, what organism could it be and why?
Staph aureus because it ferments mannitol and thus ↓ pH by producing acid
What pathogen causes rheumatic fever/ heart disease
Step pyogenes
What is an example of group A strep?
Strep pyogenes;
What which group strep is responsible for impetigo, strep through or skin infections?
Group A (strep pyogenes)
What is grouping criteria of the viridans streptococci
- whatever remains after the β hemolytic streptococci, enterococci and pneumococci are excluded from the streptococci
- have a green color; α hemolysis
what are some organisms in the viridans streptococci group?
S. Mutans (dental carries)
S. Sanguinis (most common cause of infective endocarditis due to strep)
S. Mitis
What specific organism is the most common streptococcus cause of IE?
Strep sanguinis
__________ is how you differentiate between staph and strep.
Staph:
Strep:
Catalase test
Staph: catalase positive
Strep: catalase negative
If you have a gram postive cocci that are catalase negative and alpha hemolytic, how do you differentiation between the two potential ones: ___________ and _________
Options would be: strep pneumonia and most viridans strep
Do a optochin test to differentiate between these two.
Strep pneumonia is optochin SENSITIVE while viridans strep group is optochin RESISTANT
How do you differentiate between catalase negative and β hemolytic organisms: ________ and _______
Use a bacitracin test to differentiate between: strep pyogenes and strep agalactiae
Pyogenes: bacitracin sensitive
Agalactiae: bacitracin resistant
Catalase negative and gamma hemolytic (no hemolysis) is most likely ________
Enterococcus
_______ hemolysis will have green color around colonies due to ________
Alpha; incomplete lysis of RBC
Methicillin resistance is seen mostly in __________ and ________ staph organisms and the genes for resistance is carried on _________
Staph aureus and staph epidermidis;
SCCmec (staphylococcal cassette chromosome) which condo does for mecA
What doe mecA encode for in methicillin resistant bacteria?
Produces an altered PBP2a → ↓ affinity for methicillin which is a β lactate antibiotic that interferes with bacterial transpeptidation
Methicillin blocks __________
Cross linking of peptidoglycan cell wall
Methicillin resistance is an example of _______________ form of resistance
Altered target form of resistance
Rheumatic heart disease/rheumatic fever is caused by ___________ (pathogen)
Strep pyogenes
__________ → type _____ HS. → rheumatic fever → rheumatic heart disease
Step throat/pharyngitis → type II HS (M protein)
