Exam 4 Staphylococcus Flashcards
Is staphylococci catalase negative or positive
catalase positive
Which staphylococci produce B-hemolysis
Staph aureus
What is the important test to classify staph species
coagulase test
What are the coagulase positive staphylococci
Staph aureus and S. Delphini, S. Intermedius, S. Lutrae, S. Hyicus: animal pathogens
What are the coagulase-negative staphylococci
S. Epidermis and S. Saprophyticus, Staph Lugdunesis
Which plates do staphylococcus grow easily on
SBA and thioglycolate plates
If staphylococcus is plated on SBA and is heavily contaminated, which selective media would be used and what would it indicate
Mannitol salt agar (MSA) would be used, Staph Aureus on MSA would be yellow, it is selective for staphylococcus and differential for S. aureus
Where does Staph aureus grow, live, and multiply (primary reservoir)?
The nares, it also grows on the axillae, vagina, pharynx, and other skin surfaces
What are hospital outbreaks called
nosocomial infections
What are the virulence factors associated with Staph aureus
Toxins, Structural cellular components , and enzymes
What releases cytokines that result in fever and hypotensive shock
superantigens
What are the toxins virulence factor of Staph aureus
Enterotoxins (superantigen), cytolytic toxins, exfoliative toxins (superantigen), and TSST-1 (superantigen)
What are the structural cellular components virulence factor of Staph aureus
Protein A, Capsules, and Slime layer
What are the enzymes virulence factor of Staph aureus
Coagulase, and Hyaluronidase
What are the enterotoxins
Enterotoxin A, C, D and B
A- associated with food poisoning
C & B- associated with contaminated milk products
B- associated with pseudomembranous enterocolitis
What is TSST-1
a superantigen that is toxic shock syndrome toxin-1, associated with super absorbent tampons on sterile packaging after surgical procedures
it is absorbed through vaginal mucosa, permitting the systemic effects seen in TSS
What is exfoliative toxin
it is responsible for (SSS) Scalded Skin Syndrome or Ritters Disease- causes the epidermal layer of the skin to slough off
What is cytolytic toxins
Alpha-toxin (a-toxin) -creates pores in host cell membranes esp red blood cells and immune cells
Beta toxin (b-toxin) -breaks down membrane lipids
Delta toxin- small peptides that disrupt membranes & contributes to inflammation
Gamma toxin (y-toxin) -target white blood cells and destroy them
& Panton- Valentine Leukocidin (PVL) -associated with severe skin infections and necrotizing pneumonia
What are the enzymes of Staph aureus
coagulase enzyme, hyaluronidase enzyme, lipase enzyme, and penicillinase enzyme (B-Lactamase specific for penicillin)
What is protein A
binds the fc portion of antibodies to avoid phagocytosis (assists in blocking phagocytosis)
What are the infections associated with Staph aureus
SSS “Ritter’s Disease), impetigo, boils, carbuncles. acute endocarditis, pneumonia, osteomyelitis, food poisoning, and TSS
When do symptoms appear if someone ingested toxins within food (Food poisoning)
2-8 hours after ingesting food (rapid)
What are the culture characteristics of Staph aureus
they can produce beta-hemolytic zones, and exhibit a yellow pigment (Au- aureus element symbol for Gold= golden color)
Is staphylococcus epidermis coagulase negative or positive
coagulase negative
What infections is Staph epi associated with
it is the common cause of hospital-acquired UTIs and a common contaminant of blood cultures (due to improper sterile techniques)
What does Staph epi get introduced to
catheters, heart valves, cerebrospinal fluid shunts, and PROSTHETIC devices, organisms produce a slime layer (BIOFILM) that helps adherence to prosthetics and avoid phagocytosis
What is Staphylococcus saprophyticus
the cause of UTIS in young, sexually active women, it is novobiocin resistant
What is the novobiocin test
it is used for only urine isolates, it differentiates s. sapro from other CoNS, Staph sapro is RESISTANT and other CoNS are susceptible
What does Staph lugdunensis mimic
staph lugdunesis mimics a positive coagulase test because of a clumping factor so it is often mistaken for S. Aureus
What is the culture characteristics of staph. epi
small- to medium sized nonhemolytic gray to white colonies
What is the culture characteristic of staph. sapro
slightly larger colonies with 50% producing yellow pigment, 50% very white pigment
What is the culture characteristic of staph. haemolyticus
medium-sized colonies with weak or moderate hemolysis and variable pigment production
Why are all the Staphylococcus catalase positive
because staphylococcus produces the enzyme catalase
What is the coagulase test
A hallmark for Staph. Aureus, it tests for cell-bound coagulase
if the coagulase test is positive it is
Staph aureus
To test for CoNS what is used
novobiocin
If a staphylococcus is resistant to novobiocin it is
Staphylococcus Sapro
If a staphylococcus is sensitive to novobiocin it is
Staph. Epidermis
What does micrococcus look like plated
bright, lemon yellow colonies
Is micrococcus catalase positive or negative
positive
Is micrococcus coagulase negative or positive
coagulase negative
If the coagulase is negative what tests is ran next
Oxidase/bacitracin
If the oxidase test is positive and susceptible to bacitracin it is
micrococcus
If the oxidase test is negative and not susceptible to novobiocin it is
coagulase-negative staphylococcus spp.
Which test is ran if oxidase-negative staphylococcus is present
the novobiocin susceptibility test
If the CoNS is sensitive to novobiocin it is
Coagulase-negative staphylococcus spp
If the CoNS is resistant to novobiocin it is
Staphylococcus saprophyticus
Is staphylococcus sensitive or resistant to furazolidone
it is sensitive
Is micrococcus sensitive or resistant to furazolidone
it is resistant
What are the rapid methods of ID for staphylococcus
The PCR (polymerase chain reaction) and MALDI-TOF
Why are most staph aureus resistant to penicillin
because they produce the B-Lactamase enzyme
If the staphylococcus spp is resistant to methicillin it should be treated with
vancomycin
What is used to detect methicillin resistance in in staph aureus
oxacillin
What is used to detect methicillin resistance in CoNS
cefoxitin
What is the mecA gene responsible for and what is the mecA gene detected by
the mecA gene is responsible for methicillin resistance and the gold standard test is used to detect the mecA gene
Erythromycin and clindamycin
should have the same resistance patterns
If the erythromycin and clindamycin don’t have the same resistance patterns what should be tested
The D-zone test
What is the D-zone test
when erythromycin and clindamycin disks are placed on a plate and there is growth between the disks but not on the side of the clindamycin (inducible clindamycin resistance)
