7.2: Pathogenesis and Virulence 2 Flashcards
MRSA stands for
methicillin resistant stapphylococcus aureas
MRSA is a gram ___ bacteria
positive
MRSA colonizes what areas of the body?
moist squamous epithelium of skin and anterior nares (nasal)
___% of people are colonized by MRSA, ___% are intermittent carriers and ____% dont have it
20; 60; 20
MRSA can infect through (4)
skin abrasions, abscesses, burns, surgical sites
MRSA is generally a ___ cause of pneumonia in the public
limited
what type of MRSA is most associated with pneumonia?
HA-MRSA
MRSA is a misnomer because
it was not always methicillin resistant, but developed over time
CA-MRSA is associated with ___ infections
skin and soft tissue
CA-MRSA is commonly acquired in what sort of settings/activities?
lots of people (prisons); contact sports such as wrestling, rugby etc
CA-MRSA has a strong resistance to what type of anti-biotic?
beta lactamases
why is CA-MRSA resistant to beta lactamases?
SCC mec cassettes
SCCmec stands for
staphylococcal cassettes on chromosome
what is a cassette?
group of genes
SCCmec cassettes are ___ genetic elements that can move through cells by ____ transfer of genetic information
mobile; lateral
there are ___ different types of SCCmec cassettes
5
most MRSA strains have ___ type SCC mec
1-3
CA-MRSA typically has ___ type SCC mec
4
SCC mec carries ___ gene that codes for PBP 2a
mecA
PBP 2a is a ___that prevents the action of which anti-biotic?
penicillin binding protein; penicillin
SCC mec can be used as marker for a strain’s ___
history
MRSA is slowly gaining resistance to what anti-biotic?
vancomycin
VISA means ____ and VRSA means ___
vancomycin (Intermediate/Resistant) staph. aureus
what drug can be used against VISA / VRSA strains?
Linezolid
what is good about Linezolid? (3)
- good activity against SA bacteria
- good serum levels
- active against MRSA, VISA, VRSA
what are 2 drawbacks to Linezolid?
- very expensive
2. toxic to mitochondria and patient must be monitored
what are 3 mechanisms leading to infection and disease by MRSA?
- capsule
- surface associated proteins and secreted toxin
- immunodulatory features to promote colonization
what is a capsule?
extra polysaccharide layer outside cell wall
the capsule displays anti___ activity
opsonic
the capsule prevents ____
opsonization (phagocytosis)
what typically phagocytosizes bacteria?
neutrophils (immune system)
MRSA strains are known to be able to survive within __-
neutrophils
MRSA contains surface associated proteins and toxins that help ___ and ___ of host
adhesion to host and cell/tissue damage
what enzyme mediates anchoring of bacterial proteins to the host cell wall?
sortase
protein A binds to
IgG
ClFA binds is a ___ factor that binds to ___
clumping; fibronectin
what is fibronectin?
host cell surface protein
immunodulatory features promote___
colonization
Group A streptococci are a ___ relevant type of gram ___ bacteria
clinaically; gram +
GA strept infects only
humans
what is the major group of GA strept?
streptococcus pyogens
what does streptococcus pyogens cause?
rheumatic heart disease (RHD)
why does GAS cause rheumatic heart disease?
Cd4+ T cells recogize it, but the same antibodies react with heart tissue, causing lesions
rheumatic heart disease is a type of ___ disease
auto-immune
sore throat / stept throat
pharyngitis (non-invasive)
Toxic shock syndrome
blood infection
bacteremia can causes ___ borne infections such as :
blood; meningitis, septic arthritis, surgical site
what can be caused by GAS?
- phayngitis
- toxic shock syndrome
- respiratory and soft tissue infection
- necrotizing fascitis
- bacteremia and associated infections
GAS is transmissible through
people in close contact
genes within pathogenicity islands are upgraded during infection to promote ___
colonization and disease
upgrading of genes in PAI is done by dedicated __
transcription regulators
what 2 transcription regulating systems are involved in promoting upgrading?
Mga and 2 component regulatory systems
what is mga? How do they affect virulence?
multigene activators. activate multiple genes during infection, leading to disease
how do 2 component regulatory systems affect virulence?
allows bacteria to sense environment with 1 and regulate with the other. actiavtes virulence factors
GAS has a variety of ___ that are produced to degrade tissues of host
toxins
surface proteins allow for ___ destruction
targeted
ScpA degrades ___ (specifically ___)
peptides; C5A peptidases
SIC is a surface protein ____
streptococcal inhibitor of complement
what is the complement pathway?
part of immune resposne (one of 1st responders against bacteria)
surface proteins reduces host immune response by reducing ___ recruitment
neurtriphil
Protein A binds to antibodies for the purpose of __
preventing them from binding to targeted antigen
the clumping promoted by the ClFA/fibronectin complex produces __
biofilms
