I. STAPHYLOCOCCI Flashcards
Greek word meaning “bunches of grapes”:
“staphle”
Are catalase- producing bacteria; facultative anaerobic:
staphylococci
The only obligate anaerobe of the staphylococci spp.:
S. saccharolyticus
Are non-motile, non-spore forming and glucose fermenter:
staphylococci
Microscopy of staphylococci:
spherical cells that appear singly, in pairs and in clusters
Culture of staphylococci:
cream, white or light gold, and “buttery looking”
The most virulent specie:
S. aureus
Aureus means:
“gold”
Culture of S. aureus:
golden yellow pigment (lipochrome), B-hemolytic (BAP)
Cultivated with added 7.5-10% NaCl:
halophilic microorganism
Chiefly responsible for the various skin, wound, and deep tissue infection:
S. aureus
Toxin-induced diseases:
food poisoning, SSS, TSS
Extensive exfoliative dermatitis that occur primarily in newborns and previously healthy children:
scalded skin syndrome (SSS)
Rare but potentially fatal. multisystem disease characterized by a sudden onset of fever, chills, vomiting, diarrhea, muscles aches and rash, which can quickly progress to hypotension and shock:
toxic shock syndrome (TSS)
Mild inflammation of hair follicle or sebaceous gland:
folliculitis
Large, raised, superficial abscesses; can be an extension of folliculitis:
furuncles/boils
Develop from multiple furuncles which may progress to deeper tissues; patients may have fever and chills (systemic infection):
carbuncles
Superficial cutaneous infection characterized by crusty lesions and vesicles surrounded by a red border’ common in children:
impetigo
Is a contaminant of medical instruments- catheters, CSF shunts and prosthetic heart valve implants:
S. epidermidis
Helps S. epidermidis in the adherence to devices:
poly-gamma-DL-glutamic acid
Culture of S. epidermidis:
non-hemolytic, non-pigmented, white opaque, pinhead colonies (BAP)
Virulence factor of S. epidermidis:
slime layer/biofilm
Antimicrobial test of S. epidermidis:
susceptible to 5ug Novobiocin
Zone of inhibition of S. epidermidis:
16-27mm
Is associated with community-acquired UTI in young, sexually active females:
S. saprophyticus
Culture of S. saprophyticus:
nonhemolytic, (50% of strains) yellow pigmented, white opaque, pinhead colonies (BAP)
Significant findings in urine culture for S. saprophyticus:
10,000 CFU/mL
Antimicrobial test of S. saprophyticus:
resistant to 5ug Novobiocin
Zone of inhibition of S. saprophyticus:
6-12mm
More aggressive than the other CoNS in its ability to be infective- associated with catheter-related bacteremia and endocarditis:
S. lugdunensis
Clinically mimic S. aureus:
S. lugdunensis
Acquired after prolonged hospital stay; proximity to patients with MRSA; after receiving broad spectrum antibiotics; nasal carriage:
Methicillin-resistant Staphylococcus aureus (MRSA)
Chromogenic test of MRSA:
(+) mauve-colored colonies within 24 hours and confirmed within 48 hours
Resistance to penicillinase-resistant penicillin is due to an altered penicillin binding protein known as:
PBP2a or PBP’2
PBP2a has low affinity to:
B-lactam drugs
All cells have genetic element for oxacillin resistance, but not all cells express resistance by virtue of PBP2a production:
hetero-resistant strains
These isolates generally have MICs right above the breakpoint for oxacillin-susceptibility:
borderline-oxacillin-resistant isolates
Resistant gene that codes for oxacillin resistance:
mecA gene
Resistant gene that codes for methylation of 23s rRNA, which results to resistance to erythromycin:
erm gene
erm gene has cross resistance to:
macrolides (erythromycin) and streptogramins (quinupristin)
erm means:
Erythromycin Ribosomal Methylase
Resistant gene that codes for an efflux mechanism, which results in resistance to erythromycin but susceptible to clindamycin:
msr A gene
msr A means:
Methionine Sulfoxide Reductase A
Harbors a single strain for an extended period of time:
persistent carriers
Harbors different strains over time:
intermittent carriers
Do not harbor any organisms:
noncarriers
Causes skin infections in immunocompromised patients:
micrococci
Microscopy of Micrococci:
gram-positive cocci in tetrads