Exam 5—COVID and Staphylococcus Flashcards
SARS & MERS mortality
10%
35%
— COVID protein binds ——-
S1
ACE-2 receptor
first covid gene translated
replicase
negative strand copy of ssRNA is used to make…
(1) more positive strand copies
(2) small RNAs for spike + membrane + envelope + nucleocapsid proteins (S + M + E + N)
2 cytokine related COVID syndromes
cytokine storm (IL6)
cytokine release syndrome
cytokine release syndrom sx
fever and organ dysfunction - may have hemoptysis, renal failure, diarrhea
Lopinavir, ritonavir, molnupiravir, paxlovid
covid protease inhibitors
Hydroxychloroquine, ivermectin
no value
Alpha-interferon
covid viral inhibitor
remdesivir
inhibits covid RNA polymerases
Regeneron, strovimab
covid monoclonal antibody against spikes
Tolicizumab
covid monoclonal antibody against IL-6 receptor
dexamethasone
steroid to reduce covid inflammation
covid surface disinfectants
Metal surfaces antimicrobial (especially copper)
2% bleach
70% ethanol/rubbing alcohol
0.5% H2O2
staph are Cat —
Pos
coag-pos staph (5)
S. aureus
S. hyicus
S. intermedius
S. pseudintermedius
S. lutrae
purpose of coagulase
Blood clots protect organisms from phagocytosis, antibody binding, and complement activation
core genome
genome shared by 80-90% of species
paragenome
complete set of genes found in species; core genome + strain specific genes
MSCRAMM
microbial surface components recognizing adhesive factors
MSCRAMM tropisms (5)
fibronectin binding, collagen binding, laminin binding, vibronectin binding, elastin binding
clumping factor function
binds fibrinogen, causing clumps of plasma
also binds factor I, which degrades C3Bb
abscess progression
Microbe associated molecular patterns (MAMPs) elicit cytokine response via TLRs
Coagulase builds a “cage” around the infection, creating a hard local infection
Toxin expression occurs
tst gene
TSST-1
TSST-1
Causes nonspecific T-cell activation, which causes release of large amounts of IL-1 and TNF-𝛼
sx of TSS
fever, hypotension, n/v/d; multiple organs involved
TSS mortality
65%
responsible for food poisoning
staphylococcal enterotoxins (SEA and SEB)
entA and entB
SEA and SEB
enterotoxins made by —-% of S. aureus
30-50%
Exfoliative toxin (Ets)
cleaves desmoglein-1 which is a cadherin that holds keratinized skin layer to basal layer of epidermis
scalded skin syndrome
bullous impetigo
Ets toxin (scalded skin)
Panton-Valentine Leukocidin
LukF and LukS
polymerize and form pores in membranes of WBCs
Staphylokinase (Sak)
binds plasminogen and activates it to cleave fibrin in an uncontrolled way
Bacteria are allowed to escape clot and spread to blood stream
Sak causes circumvention of…
Regulation by PAI-1 and antiplasmin
Staphylococcal alpha toxin
Hla
Integrates into membranes of host cells, causing pores
Causes alpha hemolysis
MSCRAMM attachment
C-terminus has a conserved ——- amino sequence
this binds to the ——-, which then passes it off to amide of one of the ——–
this forms a peptide bond between the (above) and the MSCRAMM
LPXTG
sortase
glycine
housekeeping sortase
sortase A
iron acquisition sortase
sortase B
pilus sortase
sortase C
spore formation sortase
sortase D
Fibronectin-binding protein (FnBP)
species
Covering bacterial cell with fibronectin makes it “look” like the host
S. aureus
Protein A
Binds Fc of IgG, preventing opsonization
Can also bind Fc of membrane-bound antibody, like IgD or IgM, which triggers apoptosis in the B-cell
alternative lactamase used in some staph, which usually have no such activity
BlaZ lactamase
main virulence mechanism of S. epidermidis
biofilms
opportunity for S. epidermidis to infect
Catheters, prosthetics, pacemakers, microscopic tears in surgical gloves
S. epidermidis capsule production of ——- leads evasion of immune system
action
poly-γ-glutamic acid
Protects from osmotic stress
Contributes to biofilm formation
Blocks phagocyte action
Prevents action of antimicrobial peptides
Combines with liberated DNA to form biofilm
Phenol-soluble modulins (PSMs)
δ-toxin
species, action
Made by S. aureus, S. epidermidis, S. haemolyticus
Cause inflammation
Detergent like action disrupts cell membranes
Can allow for phagosome escape
only produces phenol-soluble toxins
S. epidermidis