Staphylococci Flashcards
catalase-producing, gram-positive
cocci.
Staphylococci
catalase-producing, coagulase negative, gram-positive cocci found in the environment and as members of the indigenous
skin microbiota
Micrococci
What color of pigment does micrococci produce?
yellow pigment
Other gram-positive cocci that are occasionally recovered with staphylococci include
Rothia mucilaginosa, Aerococcus, and Alloiococcus
otitis
staphylococci are nonmotile, non–spore-forming, and
aerobic or facultatively anaerobic except for?
S. Sacchorolyticus
colonies of staph are produced after how many hours?
18-24 hours
what is the appearance of staph?
white or gold and buttery looking
what is the most clinically significant species of staph?
S. aureus
staphylococci that are coagulase positives are?
s. aureus s. intermedius, s. delphinin, and s. lutrae
staphylococcus can grow in what medium?
MSA, BAP, and CNA
what test is used to differentiate staphylococcus spp. to streptococcus spp.
catalase test
principle of catalase:
catalase + _____ - H2O + O
H2O2
used to differentiate S. aureus from other Staphylococci; definitive and most reliable method for
detection of the species
coagulase test
it detects bound coagulase/clumping factor?
slide coagulase
what kind of plasma is used in slid coagulase?
rabbit’s plasma
detects free coagulase/ coagulase reacting factor
tube coagulase
latex particles are coated with sheep red cells or human plasma fibrinogen and IgG which will react with clumping factor cells and protein A of S. aureus
latex agglutination
what is the inhibitor of MSA
7.5%-10% NaCl
What is the indicator of MSA
phenol red
s. aureus in MSA (appearance)
yellow zone around colonies
s. epidermis in MSA (appearance)
red zone around colonies
causes various cutaneous infections and purulent
abscesses that can progress to deeper abscesses
and produce bacteremia and septicemia
s. aureus
Staphylococci that do not produce coagulase are
referred to as?
CoNS
known to cause various health care-acquired or nosocomial infections
s. epidermis
associated mainly with urinary tract infections (UTIs), predominately in adolescent girls and young women
s. saprophyticus
is a CoNS occasionally recovered in wounds, septicemia, UTIs, and native valve infection
s. haemolyticus
is also a CoNS, but it can
occasionally be confused with S. aureus if
performing only a traditional slide coagulase
method using plasma
s. lugdunensis
– interferes with opsonization and phagocytosis from neutrophils and activation of complement;
immunogenic; binds to Fc fraction of most IgG
protein a
resist phagocytosis by neutrophils; enhance organism’s ability to bind to host cells and prosthetic
capsular polysaccharide
activate complement, enhance neutrophils, chemotaxis, and formation of opsonin; has clumping factor adhesins & collagen-binding protein
peptidoglycan & teichoic acid
are heat-stable exotoxins that cause various
symptoms, including diarrhea and vomiting
enterotoxins
enterotoxins are stable at
100°C for 30
minutes
Staphylococcal food poisoning: most
commonly caused by enterotoxins?
A B D
linked to staphylococcal
pseudomembranous enterocolitis
Enterotoxin B
causes nearly all cases of menstruating associated TS
Toxic shock syndrome toxic 1
known to cause staphylococcal SSS,
sometimes referred to as Ritter disease.
▪ also been implicated in bullous impetigo
Exfoliative toxin
coats neutrophils with fibrin which protects organism from phagocytosis.
bound coagulase
– lyses and inactivate penicillin through breakdown of B-lactam; resistance to
ampicillin and other antibiotics
penincillinase
lyses RBC; responsible to B-hemolysis
hemolysin
– exotoxin which destroys WBC; contributes to the invasiveness of
the organism by suppressing phagocytosis; involved in community acquired MRSA
panton-valentine leukocidin
CoNS that are hospital acquired and most common cause of UTI and prosthetic valve endocarditis and other prosthetic devices
S. epidermis
key component that are responsible in pathogenesis and promote adhesion in surfaces
biofilm production
what CoNS have creamy and white colonies and prose gamma hemolytic which produce slime and adheres to the agar surface
S. epidermis
cause UTU such as pyelonephritis and cystitis especially in sexually active young women and cause of catheter associated UTI in men and women
s. saprophyticus
they have the ability to adhere epithelial cells in urinary tract and urethral cells
s. saprophyticus
white colonies, gamma hemolytic, and resistant to novobiocin
s. saprophyticus
can be more virulent and can mimic the infections of s. aureus
s. lugdunensis
s. lugdenensis have the ability to resists oxacillin. what gene does this CoNS have
meCA gene
pathogen that cause endocarditis, septicemia, and soft tissue infections
s. lugdunensis
CoNS that have white to large. smooth, glossy edge with slight domes center, unpigmented or cream to yellow orange columns
s. lugdunensis
enumerate the penicillin resistance of MRSA
nafcillin, oxacillin, methicillin, and amoxicillin
what is the treatment of choice for MRSA
vancomycin
MRSA detection that are commercially available and mauve color as their end product
chromogenic
latest CLSI M100 detection test for MRSA
cefoxitin disk screen test
what is the gold standard and most sensitive for detection mecA or PBP2a
PCR
used to differentiate from staphylococcus to micrococcus
modified oxidase test
if the test result came out in a dark blue color. what is the interpretation?
positive and micrococcus
if there is no color change in modified oxidase test. what is the interpretation
negative and staphylococcus
what is the next course of action is the organism is positive and catalase test?
coagulase test
what is the next course of action if the organism is negative in coagulase test?
oxidase test
what staph spp. is resistant to novobiocin?
s. saprophyticus
what is the best inducer of mecA mediated resistance?
cefoxitin
what is the frequently used in staphylococcal skin infections?
Clindamycin
most clinically significant and commonly recovered species in the CoNS?
s. epidermis and s. saprophyticus
s. epidermis is known to cause what kind of infections?
nosocomial infections
