Staphloccoci Flashcards
Staph. Aureus is coagulase _____
Positive.
Staph aureus is the only coagulase POSITIVE staph (that we have to know)
Coagulase positive = will clot plasma by activating fibrinogen
All three important groups of staphloccoci are GM ____ with _____ morphology
GM + cocci in grape clusters
Staph epidermidis is coagulase _____
Negative; it will not clot plasma
Staph saprophyticus is coagulase _____
negative. it will not clot plasma
All staphloccoci are Catalase ______, allowing us to differentiate them from ______ species
Staph are catalase POSITIVE; this allows us to distinguish them from catalase negative STREPTOCOCCI
Staphlococci are _________ an/aerobes
FACULATIVE ANAEROBES
Colony colors:
S. Aureus
S. Epidermidis
S. Saprophyticus
yellow
white
white
Of the 3 major staph species, which is RESISTANT TO NOVOBIOCIN?
S. Saprophyticus
Which staph species(s) is positive for PROTEIN A?
S. Aureus
Which staph species(s) is positive for teichoic acid
ALL 3
T/F: S. Aureus is a toxin producer, and an invasive opportunistic pathogen
TRUE
Which staph species(s) is DNAse positive
Just S. Aureus
Which staph species(s) is hemolytic on blood agar?
Just staph aureus
T/F: S. Aureus is more likely to colonize the hospitalized and those with foreign bodies
True
Name 3 toxin-mediated diseases by S. Aureus:
- food borne diarrhea - enterotoxin contamination, bacteria not present
- toxic shock syndrome - toxin production after bacterial colonization via fibrinogen receptor-ligand interacctions
- Staphlococcal scalded skin syndrome - caused by exfolatins
What toxins and enzymes are responsble for cell lysis by S. Aureus? (there are 7, but 2 important ones)
ALPHA TOXIN - lyse cell membrane COAGULASE - forms clots in plasma leukocidins proteases hyalaronidase lipase staphlokinase
What is the function of S. Aureus’ ‘Protein A’?
PROTEIN A is a cell wall protein that binds hist IgG via FcR, which results in less complement mediated killing. Also, it is a B cell superantigen leading to defective IgM production. OVERALL, IT AIDS IN IMMUNE EVASION
What are the functions of S. Aureus enterotoxins A-E, G, H, and I?
These are T cell superantigens allowing S AUREUS TO BLUNT THE HOST T CELL IMMUNE RESPONSE
Function of S. Aureus capsular polysaccharides?
Anti-phagocytic
T/F: S. Aureus enterotoxin is HEAT STABLE
TRUE; boiling will not destroy this toxin. (thus you get food poinsining)
T/F: S. Aureus enterotoxins can act as superantigens
True, types A and C are superantigens
T//F: S. Aurues toxic shock syndrome does not require colonization
False - Colonization must occur for TSS
TSST-1 is a _____________ associated with ______ syndrome which can result from _____ use or _______
TSST-1 is a superantigen
it is produced during toxic shock syndrome
TSS can occur from tampon use or wound infection
SSSS is caused by:
Staphlococcal scalded skin syndrome is cause by toxins called EXFOLIATINS A and B
T/F: the genes for exofolitins A and B are encoded on all S. Aureus DNA.
False, these toxins are encoded only in certain strains (PHAGE GROUP II) and are located on the ETA PLASMID
T/F: exofolitins are superantigens
TRUE
T/F: the sites of peeling in SSSS are indicative of local exofoliatin production
FALSE. the site of exfoliation may not be the site where the toxin is being produced
Invasive diseases caused by Staph Aureus, unlike toxin mediated diseases, are characterized by :
Suppuration and ABSCESS formation
What is the last resort drug for Staph Aureus strains that are resistant to _____ and _____
The last resort drug is VANCOMYCIN, used for strains that are resistant to synthetic penicillins like DICLOXACIN and OXACILLIN
Staphlococcus epidermidis is a coagulase ____, GM ____ coccus.
Coagulase negative, GM +
Staphylococcus epidermidis is catalase ______
Catalase positive, this enables it to be differentiated from Group A Streptococci.
T/F: Staph Epidermidis is sensitive to Novobiocin
True
Staph epidermidis is part of the normal skin flora yet is an opportunistic pathogen. What is its major mechanism of invasion, and who is most at risk?
Staph epidermidis infections are primarily transmitted by ahderence to FOREIGN BODIES such as catheters, lines, prostheses, etc; thus it is most common in neonates, renal failure pts, immunocompromised.
T/F: Staph Epidermidis cannot form biofilms
False, S. Epidermidis CAN form biofilms, an does so on prosthetic surfaces efficiently.
T/F: Staph Aureus bacteremia is more toxic than Staph Epidermidis bacteremia
TRUE
Staphylococcus Saprophyticus is coagulase _____
Negative
Staph Saprophyticus is ______ to Novobiocin
RESISTANT (unlike S. Epidermidis)
T/F: Staph Saprophyticus is a skin commensal
TRUE
A common clincal syndrome of staph saprophytics is:
Female UTI w/ polyuria + dysuria
How do you treat a female with a S. Saprophyticus UTI?
Trimethoprim sulfamethoxazol (bactrim) norfloxacin (a quinolone)
These durgs have good bladder penetration
