Staphylococcus Flashcards
what are the main characteristics of staphylococcus
gram positive, facultative anaerobic
is staphylococcus motile ? does it form spores ?
non motile and nonspore forming
what is the result of the catalase test for staph
catalase positive
a positive coagulase test would mean the sample is what species
staphyloccus aureus
what is the causative agent of staph that infects humans ?
staphylococcus aureus
what are the potential infections caused by staph aureus
integument wounds (falliculitis) bacteremia
how do humans encounter staph ?
30-40% of humans carry it in nares and only causes a problem if the right oppurtunity arises
how does staph gain entry into the host
damage to skin, hair follicles, or mucosal surfaces
the spread/multiplication of staph in the host is variable with ?
- innoculum size
- immunocompetance
- how close to vascularization
what populations are at elevated risks for severe staph infection
young children, elderly, diabetics, people with bad immune system
what are MSCRAMMs
microbial surface components recognizing adhesive matrix molecules
-help staph stick to and colonize on host tissue
what are the 3 main MSCRAMMs of staph
- Fibronectin binding proteins
- collagen binding proteins
- clumping factors that bind fibrinogen
how does staph cause damage to the host
acute suppurative inflammation (accumulation of puss)
the pus accumulation of staph is actually an accumulation of what ?
neutrophils
what are PMNs
polymorphonuclear WBCs
what specific PMNs is involved with the damage caused by staph
neutrophils
what role do PMNs play when staph pathogens enter the host
-first responders (US Marines)
perform phagocytosis, release toxic ROS, release signalling cytokines
what are the virulence factors of S. aureus
- polysaccaride capsule
- protein A (blocks host Ab)
- pore forming toxins
what pore forming toxin does S. aureus produce that destroys PMNs
Panton-Valentine Leukocidin
Staphylocaccal Scaled Skin Syndrome (SSSS) is a result from ?
exfoliative toxins from S. aureus causing layers of epidermis to seperate
how do exfoliative toxins of S. aureus work ?
they are proteases that destroy desmosomes of the epidermis, thus separating epidermis
What is toxic shock syndrome caused by ?
S. Aureus producing toxic shock syndrome toxin (TSST-1)
what is TSST-1
superantigen
what is a superantigen
it is an antigen that causes unregulated activation of helper T cells, which causes a “cytokine storm”
what does the cytokine storm of toxic shock syndrome cause
- fever
- capillary leakage
- rash
Food poisoning is caused by ?
Staphylococcus aureos in unrefridgerated food causing an intoxication
what is the mechanism of food poisoning caused by S.. aureus
causes release of enterotoxin A which is a superantigen
what makes the crosslinks in gram positive peptidoglycan cell walls
Penicilan Binding proteins
- transpeptidases
- transglycosylases
how do Beta lactam antimicrobial agents work ?
they inhibit Penicilan binding proteins so inhibit formation of peptidoglycan cell walls in gram + bacteria
what is the aquired allele/protein in Methicillan resistent S. aureus (MRSA)
PBP2a
what drug is used to treat methicillan resistant S. aureus (MRSA) ?
Vancomycin
what is the most effective tool to prevent spread of staph
wash hands
