Lecture 8 - STAPHYLOCOCCUS Flashcards
are staphylococci gram (+) or gram (-)?
gram (+)
are staphylococci catalase (+) or (-)
catalase (+)
what does catalase do?
breaks down hydrogen peroxide into water and oxygen (also breaks down other superoxide products of respiratory burst).
inactivates the reactive species that the immune system produces to destroy in it order for the staphylococci to protect itself
is staphylococci aerobic or anaerobic?
aerobic (facultative), meaning that it is aerobic but CAN survive in an anaerobic environment
how does staphylococci grow?
does it have flagella?
staphylococci grows in CLUSTERS and does NOT have flagella
does staphylococci form spores? explain
NO, but it can still survive in harsh conditions
what type of harsh conditions can staphylococci survive in?
HIGH SALT and WIDE TEMPERATURE RANGE
is staphylococci part of our endogenous flora or is it always pathogenic?
it’s part of our endogenous flora on skin and mucosal surfaces.
how is staphylococci transmitted?
through direct contact or exposure to fomites
what is a fomite?
an inanimate object that can transfer infection
is staphylococci dangerous?
it’s part of our endogenous flora so usually not.
even if we are infected, immune system can handle most of the time
BUT if it does infect us and the immune system is overwhelmed it causes tissue damage and quickly becomes systemic and deadly. it can get into the blood stream
give an example of a specific staphylococci species
staphylococcus aureus
what is unique about staphylococcus aureus bacteria?
it produces important enzymes (coagulase), toxins (alpha-toxin), and superantigens (SAgs)
where does staphylococcus aureus habitate?
in the nostrils and perineum
what infections does staphylococcus aureus cause?
DEEP INFECTIONS – pneumonia, osteomyelitis, abcesess, TSS (toxic shock syndrome)
does staphylococcus aureus cause:
-biofilm?
-boils?
-UTI?
creates biofilm and boils but NOT UTI
Staphylococcus aureus production of superantigen correlates with……
SEVERE DISEASE
If staphylococcus colonizes in the vaginal area, what happens?
TOXIC SHOCK SYNDROME
Does staphylococcus aureus cause abcesses?
YES.
these can aid in the spreading. spread through direct contact
staphylococci primarily replicates where?
in nasopharynx – very moist there (mucosal membranes)
why is staphylococcus so prominent in hospitals?
they can easily colonize medical devices.
also, spread through direct contact
what is responsible for TSS?
production of superantigens by staph aureus
how many different serotypes are there of staphylococcus aureus?
11 serotypes
what are the structural components of staphylococcus aureus that are classic for a gram positive bacteria?
what are the surface proteins on staphylococcus aureus that are relatively unique?
classic to gram(+): highly cross linked peptidoglycan and teichoic acid
UNIQUE: SpA (surface protein A) and Clf (clumping factor)
what is the function of teichoic acid?
spans the peptidoglycan layer to give rigidity
what is the function of surface protein A?
binds the Fc region of antibodies (immunoglobulins)
what is the function of Clf?
clumping factor.
binds fibrinogen and FnBP (Fibronectin-binding proteins) together
–fibrinogen is crucial to the host cell function. thus, Clf aids in bacterial function by binding to these. fibrinogen acts as a host attachment protein for the bacteria
name the layers of staphylococcus aureus
has a capsule layer and a polysaccharide slime layer, also peptidoglycan layer that is crosslinked by teichoic acid
name 4 enzymes produced by staphylococcus aureus and state their function
-coagulase – converts fibrinogen to fibrin which creates a physical barrier between the bacteria and the immune cells trying to destroy it
-hyaluronidase – breaks down hyaluronic acid present on host cell membrane
-lipases – hydrolyzes lipids to help break down host cell membrane
-Nucleases – digests the DNA of host cell to destroy the cell completely
the cytotoxins produced by staphylococcus aureas are cytolytic for which 3 cells?
erythrocytes (RBC)
keratinocytes
fibroblasts
name the cytotoxins produced by staph aureus
alpha, beta, delta, gamma, and PVL (panton-valentine leukocidin)
name the functions of alpha toxin and PVL (panton-valentine leukocidin) produced by staph aureus
alpha toxin — pore forming cytotoxin NOT EFFECTIVE AGAINST NEUTROPHILS
PVL – targets neutrophils (since alpha toxin cant) and platelets
name all of the toxins produced by staphylococcus aureus
- cytotoxins (alpha, beta, delta, gamma, PVL)
- Exfoliatin
- SUPERANTIGENS (enterotoxins)
what is the function of exfoliatin toxin
a protease that disrupts the stratum granulosum (layer of the skin) that prepares the skin for a productive infection
go into more detail about staph aureus superantigens
the enterotoxins (A-V) are superantigens. there are over 20 of them produced by staph aureus. they cause food poisoning
ex: SEA (Staph enterotoxin A_, SEB, SEC, etc
other superantigen toxins produced by staph aureus produce TSS (toxic shock syndrome) due to a massive cytokine release. causes leaking and destruction of endothelial cells
explain how staph aureus works to cause cell death
FNBP binds to fibrinogen sheath on the host cell membrane.
staph A secretes alpha cytotoxin which is a PORIN. as more and more pores devleop the cell begins to be destroyed. (the bacteria can move through a porin between cells and infect many adjacent cells by moving through the porins produced by alpha toxin) COAGULASE forms a fibrin wall from fibrinogen that prevents the neutrophils from attacking the staph Aureus that is now invading the cell
staph A gets into bloodstream through the destroyed epithelial cells and causes major tissue damage and infection
name 3 toxin-mediated diseases from staphylococcus aureus
-scalded skin syndrome (due to exfoliatin)
-food poisoning (through ingestion of superantigen enteroxin)
-toxic shock syndrome (through toxic shock syndrome toxin-1)
what does pyogenic mean?
causes fever
what cutaneous infections does staph A cause?
causes pyogenic, pus-forming abcesses
impetigo
folliculitis
farbuncles (BOILS)
cabuncles (MULTIPLE boils)
wound infections
why is staph aureus commonly associated with wound infections?
easy entry for it go get in
spread via direct contact
if staph a gets into the blood, what dangerous conditions can it cause?
can spread anywhere and cause:
-endocarditis
-pneumonia
-septic arthritis at large joints
how does septic arthritis occur?
the antigen-antibody complex is insoluble and depositis in joints.
RESULT OF OUR OWN IMMUNE RESPONSE
Does staph A have pathogenicity islands?
yes – extrachromosomal.
how the virulence genes are controlled
boils are _____ infections
cutaneous (skiN)
explain how boils develop in a staphylococcus aureus infection
staph A can get into the skin through a hair follicle via direct contact with the bacteria.
the bacteria can spread to the subcutaneous tissue and white blood cells are continually recruited to help fight the infection. this buildup creates an abcess and is plugged by necrotic material (dead white blood cells)
where does staphylococcus aureus shed?
nasal
explain how TSS develops due to staphylococcus aureus
staph A is normally commensal in the vaginal area. there is normally a free flow of fluids.
however, when a tampon is inserted the free flow of fluids is blocked which propagates the replication of staphylococcus aureus. superantigen is expressed producing a cytokine storm activating a large number of T cells anf generating an overwhelming immune response
is staphylococcal resistant to antibiotics?
explain
has 2 means of antibiotic resistance
has penicillinase to open the beta lactam ring of penicillin to break down any penicillin antibiotic
the target of penicillin is a non-self (altered) petidoglycan transpeptidase. staph aureus contains a gene on its pathogenicity island that expresses an altered PBP (called penicillin binding protein 2 – PBP2) that penicillin cannot recognize
WHY is peptidoglycan transpeptidases the target of penicillin?
if penicillin inhibits this enzyme, the bacteria cannot produce their protective cell wall
as mentioned, staphylococci aureus has 2 major ways of resisting penicillin antibiotics.
what other antibiotic is it capable of resisting which poses a major concern?
there are some vancomycin-resistant staph aureus strains which is a MAJOR concern since vancomycin is a last resort antibiotic.
what does MRSA stand for and mean
methylcillin resistant staphylococcus aureus
staph aureus that is resistant to penicillin
