S. Aureus - S.capitus Flashcards
S. Aureus is gram (__), faculative ____, and is shaped like ____
+; coccus; grapes
S. Aureus is catalase __ and coagulase ___
+; +
S. Aureus is the 2nd leading nosocomial infection. True or false?
true
S. aureus can be resistant to ___ and ___ and also cause _____
ph; heat/cold; desiccation (dryness)
In order to ID s. aureus, what do you need to do for the following: abcess bacteremia SSS bullous impetigo TSS food poisoning
abcess: scrape and do a gram stain
bacteremia: culture blood
SSS: culture nasopharyngeal samples
bullous impetigo: culture blister fluid
TSS: vaginal secretions have cocci, blood (-)
food poisoning: check food, not poop
What color does S. Aureus grow on a manitol-salt agar plate?
yellow
What color does S. Aureus grow on tellurite-glycine agar plate?
black
In regards to color and hemolysis, what do S. Aureus colonies look like on blood agar plate?
hemolytic yellow colonies
S. Aureus is typically found in the ___
nares
What is USA300?
MRSA in US
In regards to diseases causes by S. Aureus, who is at risk for SSS and TSS
SSS: newborns, kids with bad hygiene
TSS: women (from catheters)
S. Aureus is the #1 cause of this disease. It presents as macule and becomes a pustule with a honey brown crusting. It is acute and contagious.
Impetigo
S. Aureus is the #1 cause of this disease. It is superficial, pyogenic infection of a hair follicle, and a result of poor hygiene.
Folliculitis and Furuncle (if several)
This disease caused by s. aureus is similar but more serious than Folliculitis/Furuncle. The boils are located on the back of the neck, back, and buttocks and the patient may also have signs of septicemia (chills, fever).
carbuncle
How does S. aureus present in a wound infection?
edema, redness, pain, purulent fluid
In regards to wound infections, S. Aureus can cause Mastitis, bacteremia, and endocarditis. Describe each situation.
mastitis: ductal system, creaked nipples, tenderness, fatigue
bacteremia: after surgery of contaminated IV/Cath
endocarditis: life threatening, increased freq. of embolization
This disease in the lungs is caused by S. Aureus is mostly nosocomial. It is serious in those who are already ill and may be due to aspiration of oral secretions. P-V leukocidins may be a big cause of this disease in the community. Toxins involved can cause tissue destruction, massive hemoptysis, and septic shock.
pneumonia
S. aureus is the most common cause of the acute form of this disease. In this disease there is a hematogenous spread or extension from a S/C infection. In kids it occurs in metaphyseal areas of long bones and in adults it occurs in vertebra (rare in long bones). There is a sudden onset of localized pain and fever associated.
osteomyelitis
S. Aureus is the most common cause of this disease, except those who are sexually active. With this disease, there is painful movement, red swollen joints, pus in aspirated joint fluid, and occurs commonly in the knee.
septic arthritis
This disease caused by S. aureus is associated with an abrupt onset of perioral erythema and covers the entire body in 24 hours. There are large blisters with fluid but no organism. Deescalation also occurs. The nikolsky’s sign is positive for this disease (pressure displaces skin).
Scalded skin syndrome (Ritter’s disease)
This disease caused by s. aureus is a localized form of SSSS. The erythema does not extend beyond the borders of blisters and unlike SSSS, organism is in the blister fluid
bullous impetigo
This disease caused by S. aureus is associated with an abrupt onset of fever, erythematous rash over the entire skin. The palms and soles desquamate. Patients also have a marked red tongue. More than 90% of the cases of this disease are in menstruating women. The pathology of this disease is associated with massive release of cytokines.
TSS
S. aureus is the most common cause of this disease. It produces 8 distinct enterotoxins that are heat stable. There is severe vomiting associated with this disease. In the vomit, there is only toxin.
staphylococcal food poisoning
note: toxin impacts CNS
S. aureus is the #2 cause of this disease which causes watery diarrhea, abdominal cramps. The mucous in the stool has bacteria. Strains of s. aureus causing this disease make enterotoxin A and leukotoxin
antibiotic associated enterocolitis
In regards to virulence, what is the purpose of s. aureus’ capsule?
inhibits chemotaxis and phagocytosis, allows adherence to foreign bodies
In regards to virulence, what is the purpose of s. aureus’ PG?
inhibits phagocytosis, endotoxin-like acitivity
In regards to virulence, what is the purpose of s. aureus’ teichoic acid
regulates cationic concentration at cell membrane, binds Fn.
In regards to virulence, what is the purpose of s. aureus’ protein A?
binds IgG, inhibits opsonization, complement activation
In regards to virulence, what is the purpose of s. aureus’ coagulase enzyme?
converts FB to fibrin = clot
In regards to virulence, what is the purpose of s. aureus’ catalase enzyme?
removes hydrogen peroxide
In regards to virulence, what is the purpose of s. aureus’ hyalurinidase enzyme?
spreading factor
In regards to virulence, what is the purpose of s. aureus’ nucleases?
pus -> spreading factor
In regards to virulence, what is the purpose of s. aureus’ lipases?
allows colonization of skin
In regards to virulence, what is the purpose of s. aureus’ ETA/ETB serine proteases?
digest anchors holding epidermis to dermis
In regards to virulence, what is the purpose of s. aureus’ alpha, beta, and gamma leukocidins?
toxic for WBCs, RBCs, platelets, macrophages, and fibroblasts
In regards to virulence, what is the purpose of s. aureus’ enterotoxins (A-R) and TSST-1?
superantigens (act on T-cells/MHC class II, releases TNF-alpha and IL 1 and 2)
S. epidermidis is gram (__) and is in purple ____
+; clusters
S. epidermidis is catalase ___ and coagulase ___
+ ; -
What do S. epidermidis colonies look like on blood agar plate, in regards to hemolysis and color?
white, non-hemolytic colonies
What does S. epidermidis look like on a MSA plate?
doesn’t ferment - purple
What does S. epidermidis look like on a tellurite plate?
doesn’t ferment - white
S. epidermidis and S. saprophyticus are ___ resistant (antibiotic)
novobiocin
S. epidermidis is found in ___ and on ___
nares; skin
note: may also be in URT, GIT, UGT
S. epidermidis is highly nosocomial and has a carriage rate of ___
100%
Disease caused by S. epidermidis is highly associated with ____ ____
intravascular devices (prosthetic heart valves, artificial joints, shunts)
S. epidermidis can also cause ____- induced UTIs and bacteremias
catheter
With this disease, caused by s. epidermidis, there is sepsis, embolizaiton, CHF, cardiac rupture, and a 60% mortality rate.
prosthetic valve endocarditis
S. epidermidis lacks protein ___, ___-toxin, and coagulase
A; alpha
S. epidermidis is hardly ever drug resistant. True or false?
false; often drug resistant
What is the main source of virulence in s. epidermidis?
slime - biofilm that allows adherence to catheters and interferes with phagocytosis
S. saprophyticus is catalase __ and coagulase __
+ ; _
What does S. saprophyticus look like on a blood agar plate, in regards to hemolysis and color?
white, non-hemolytic colonies
What does S. saprophyticus look like on a MSA plate?
doesn’t ferment - purple
Where is S. saprophyticus infection usually found?
skin and UGT mucosa; endogenous spread to UT in women
This S. saprophyticus disease is the 2nd most common cause of UTI in sexually active women.
cystitis
note: cystitis, peylonephritis; dysuria, pyruria are common and frequently drug resistant
S. haemolyticus and s. captious are both found in normal skin flora in axilla and perineum. What disease do they cause?
endocarditis, UTI, wound infections, opportunistic infections
