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64 Cards in this Set
- Front
- Back
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what are the three major medically important staphylococci?
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S. aureus, S. epidermidids, S. saprophyticus
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where is S. aureus carried in 30% of the population?
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anterior nares
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If someone contracts S. aureus in the hospital, what is the most likely source?
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medical personnel
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which staphylococcus is sensitive to novobiocin? which is resistant?
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sensitive: epidermidis
resistant: saprophyticus |
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which member of the staph family is more likely to cause prosthetic infections? UTI's in young sexually active females? Osteomyelitis?
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prosthetic: epidermidis
UTI: saprophyticus osteomyelitis: Aureus |
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what two pathogens create biofilms? what can they cause due to their ability to create biofilms?
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strep viridans and staph epidermidis. Both can cause subacute endocarditis.
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what is the function of teichoic acid?
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mediator of attachment and mediator of cytokines
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what is antigenic and relatively specific for S. aureus?
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ribitol-Teichoic acid
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what is S. aureus's virulence factor that binds to the Fc portion of IgG molecules?
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Protein A
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what is the pathogenesis of osteomyelitis via staph aureus?
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1) colonization via adhesins
2) invasion: via staphylokinase, hyaluronidase, and other extracellular enzymes 3) resistance to phagocytosis: coagulase and it produces catalase. 4)resistance to immune responses: coagulase, protein A 5) Toxins: release of toxins--- hemolysins, leukocidin |
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How does coagulase work?
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it breaks down fibrinogen to fibrin making a mechanical barrier around it which allows it to evade phagocytosis.
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what is the function of exfoliatin?
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works between stratum spinosum and stratum granulosum causing intracellular splitting of the epidermis (detaching) causing global denutation.
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what pathogen releases exfoliatin?
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s. aureus
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why are superantigens called superantigens?
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because the superantigen binds outside the MHC molecule and outside of the v-beta region of the T cell. Therefore the specificity is loss they can bind to anything. This will cause a mass proliferation of inflammatory cells- IL-1, TNF-alpha.
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what is the difference between the triggering points of gram negative shock and toxic shock syndrome?
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gram negative shock is triggered by LPS (ie all the inflammatory cytokines are induced by the LPS).
toxic shock syndrome: all of the inflammatory cytokines are triggered by TCR. |
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staph aureus ferments on what medium? what color does this medium turn?
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mannitol salt agar. Turns from red to yellow.
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what are the coagulase negative staphylococci?
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s. epidermidis and s. saprophyticus
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what are the three ways in which bacteria can acquire new genes? how do they work
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1) bacteriophage,
2) conjugation (attach to eat other by sex pilli and 1-- the donor will donate the F factor and once the F is incorporated to DNA then they are called HFR cells.) 3) transduction- phage infects.. specialized and generalized transduction |
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what is the F factor?
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is the fertility factor that is owned by the donating sex pilli.
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what is the DOC for tx of MRSA? what problem is arising?
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vancomycin; vancomycin resistat MRSA.
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what is the function of transpeptidase?
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catalyze the crosslinking of peptidoglycans
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how does penicillin inhibit cell wall synthesis?
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by binding to transpeptidases (penicillin binding protein)
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what does vancomycin directly bind to? what does it inhibit?
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AA side chain and it inhibits the crosslinking of peptidoglycans.
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how did penicillin resistance develop?
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transpeptidase was attacked by beta lactamase which was coated by chomosomal G. That beta lactamase opens up the beta lactam ring of the antibiotics inactivating them.
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what is the mechanism of penicillin resistance?
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chromosome mediated- coating of beta lactamase enzymes
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what is the mechanism of MRSA?
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plasmid mediated transduction
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T/F
if penicillin can reach the transpeptidase, it can still inactivate it. |
true
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what is vancomycin resistance?
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when the terminal chain of the AA is changed and vancomycin can't bind.
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how is multidrug resistance acquired?
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via plasmid mediated transposition which involves the trsnposon
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what do you give a patient who is methicillin sensitive?
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nafcillin or oxacillin
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what do you give a pt who is methicillin resistant?
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vancomycin or levofloxacin + rifampin
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what do you give a pt who is vancomycin resistant?
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streptogramin (dalfopristin and guinupristin in combo).. must be in combo.
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what pathogen causes osteomyelitis after trauma or surgery?
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Group strept A
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what causes osteomyelitis in neonates?
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S agalaciae
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what causes osteomyelitis in older infants, children and adults?
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S. viridans
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what causes osteomyelitis in pts with hemolytic disorders?
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S. Viridans
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what are the three types of streptococci that are lancefield antigens?
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S. pyogens, S. agalactiae, S. pneumoniae
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what is the only gram positive diplococci?
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S. Pneumoniae
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what virulence factors of streptococcus binds to surface molecules like fibronectin?
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Protein F, M protein and Lipoteichoic acid
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what is the essential virulent factor for streptococcus pyogenes? what does it do?
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M protein; it degrades C3b and allows evasion of phagocytosis.
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what is detecting in serotyping? what protein is essential for this serotyping to occur?
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difference between pyogenes and pneumoniae (streptococcal). M protein
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what strain of M protein causes post streptococcal glomerulonephritis?
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M12
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what is targeted for serotyping for streptococcal pneumonia?
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capsular polysaccharide
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Which streptococcus is bacitracin sensitive?
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Group A Streptococcus
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what is the confirmatory test for group B streptococcus?
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CAMP test
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how do you differentiate s. viridans from s. pneumonia?
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optochin disc. Pneumonia is sensitive to optochin.
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how do you confirm the diagnosis of rheumatic fever?
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if the pt has either 2 major criteria conditions or one major and 2 minor criteria.
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what is included under the major criteria for Rheumatic Fever?
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carditis, arthritis, chorea, subcutaneous nodules, erythema marginatum
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what is included under the minor criteria for Rheumatic Fever?
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fever, joint pain, electrical changes in the heart, presence of certain proteins in the blood.
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which pathogen is a normal intestinal flora that is able to withstand high bile and salt?
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enterococci
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T/F
Enterococci species do not contain lancefield group D antigen |
FALSE
they do contain lancefield group D antigen |
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what is the medium of choice for enterococcus growth?
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bile esculin
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where do you usually encounter enterococcal infections?
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hospital settings
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three pathogens can cause subacute endocarditis, what are they?
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strept viridans, staph aureus, and enterococcus
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T/F
enterococci can be txed with B-lactams. |
FALSE.
they are relatively resistant to B-lactams and aminoglycosides. |
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what are the agents of choice for minor enterococcus infections?
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penicillin and ampicillin
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what pathogen can cause osteomyelitis following a dog or cat bite? what about human bites?
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Pastruella multicolor; kingella kingae
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what type of selective media is helpful for recovering kingella kingae?
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a selective media containing clindamycin or vancomycin
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what makes Kingella kingae different from all the other kingella's?
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it's beta-hemolytic
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what population is generally effected by bone and joint infections caused kingella kingae? what population is generally affected by endocarditis, septicaemia, keratitis, diskitis and CNS infections caused by kingella kingae?
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1) infants and children
2) adults |
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what does a mature colony of Eikenella corrodens smell like? what color will it be?
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smells like bleach and it will be yellow.
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how do you differentiate kingella kingae from einkella corrodens?
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einkella corrodens has lysine decarboxylase and ornithin decarboxylase. Kingella kingae does not.
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when ornithine is present in the medium, what color does the solution change? what if they can ferment glucose, what color does it change? what happens if they can do neither?
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ornithine: purple
glucose: yellow neither: not changed |
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both Einkella corrodens and Kingella Kingae are susceptible to what?
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B-lactam antibiotics, tetracycline and quinolones
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