Exam 2: Staphylococci Flashcards
enzymes that can lyse red blood cells
hemolysins
for bacteria that can secrete hyemolysins
Blood hemolysis plating
inhibits fungal growth
cycloheximide
inhibits peptidoglycan synthesis
LB
mimic D-ala-D-ala
LB+penicillin+cycloheximide
what happens when we are infected with the flu?
- flu penetrates airway epithelium
- “send help” –> CD8+ T cell
- cytotoxic response (killing infected cells)
- decrease phagocytes antimicrobial function
- decrease phagocytosis
- decrease ROS production
- increase susceptibility to bacterial infection
what happened during the 1918 spanish flu H1N1?
- 50% of the world was infected
- 40-50 million died
- even healthy young adults died
- 95% actually died from bacterial pneumonia (secondary ico-infection)
how does the flu infect humans and how does it work?
- endocytosis
- membrane engulfs flu cell
- forms endosome (has H+, hydrolytic enzymes, flu cell)
- virus RNA replicate and go into host cell
- help degrade H and N proteins
* help with viral-endosomal membrane fusion
staph proteases
what does the epidermis consist of?
- keratinocytes
- hair
- basal layer
- Dendritic cells
- CD8+
what does the dermis consist of?
- SALT
- lymph blood vessels
where does bacteria most likely grow in the skin?
most likely grow by hair follicle
what defenses does the skin provide against bacteria?
- hard to penetrate
- slough off; hard to adhere
- dry, low pH
- antimicrobial fatty acids
- dendritic cells
- CD8 T cells
- SALT
what kind of dendritic cells are on the skin?
Langerhans cells (antigen presentation)
skin associated lymphoid tissue
SALT
how do we also prevent bacterial penetration on our skin?
- handwashing
- skin microbiota
how do our skin microbiota protect us?
occupy a nutrient niche and secrete antimicrobial compounds
how can bacteria be classified?
- gram staining (+/-. shape/size)
- O2 requirement
- salt
- temperature
- pH
- nutritional (autotroph/heterotroph, etc)
what are the two types of positive bacteria from gram staining?
rod shape and cocci
what are the rod shape bacteria?
- Listeria
- clostridium bacillus
what are the divisions of cocci bacteria?
*they can either be catalase + (bubbles) or catalase - (H2O2–> O2 + H2O)
if a coccus bacteria is catalase +, what kind of bacteria is it?
Staphyloccocus
if a coccus bacteria is catalase -, what kind of bacteria is it?
streptococcus
what are the divisions of staphylococcus?
coagulase + (clot) and coagulase -
If a staphylococcus bacteria is coagulase +, what specific bacteria is it?
staphylococcus aureus (usually beta hemolysis)
if a staphyloccous bacteria is coagulase -, what specific bacteria is it?
staphylococcus epidermis
what can streptococcus bacteria perform?
hemolysis
can perform beta hemolysis
Group A and B streptococcus
can perform alpha hemolysis (partial clearing)
streptococcus pneumonia
perform gamma hemolysis, which is no hemolysis
enterococcus
what is an example of technology being developed without consulting microbiologists?
double absorbing action tampons
what did double absorbing action tampons?
toxic shock syndrome
what is toxic shock syndrome caused by?
release of poisonous substances from an overgrowth of bacteria called Staphylococcus aureus
what are the characteristics of s. aureus?
- gram +
- catalase activity +
- coagulase +
- very well human adapted pathogen
what are the requirements for infection of s. aureus?
- adhesion and survival
- invasion and damage
- secrete other toxins (virulence factors)
What is involved in adhesion and survival for s. aureus? In other words, how does s.aureus adapt the the challenges of the skin?
- s. aureus can survive on dry inanimate objects
- has wide ranges of pH survival (4-10)
- expresses lipases which cleave fatty acids and use smaller parts for carbon source
- express MSCRAMMs (adhesion molecules)
- adheres to our collagen
microbial surface components recognizing adhesive matrix molecules
MSCRAMMs
what does bacteria add to the membrane of the host and how does it change it?
- *antimicrobial peptides are +
- bacteria adds D alanine to modify the charge
- adds L-lysine
- results in negative charges at surface
what does s. aureus do to invade and damage a host?
- Hydrolytic enzymes
- lipases
- proteases (degrade host proteins + antimicrobial peptides)
- DNases (degrade DNA; effective against NETs)
- cuts, burns, insect bites, or wounds make it easier for invasion
- pore forming toxin
- alpha toxin—> Beta hemolysis
- leukocidins—> form pores on leukocytes
what toxins do s. aureus secrete?
- exfoliative toxins
- enterotoxins
- super antigens
what is the exfoliative toxin that s. aureus secretes?
serine proteases
cleave keratinocyte proteins, which hold the skin together
serine proteases
who are more susceptible to serine proteases?
infants/newborns and immunocomprimised adults
what do newborns often develop because of serine proteases?
staphylococcal scalded skin syndrome
- found in GI
- causes food poisoning in gut
- emetic and diarrheal symptoms
- causes toxic shock syndrome in blood
- acts as superantigen
enterotoxins
what is an example of a superantigen?
toxic shock syndrome toxin-1
what are the effects of superantigens?
- polyclonal expansion (non-specific)
* massive T cell activation –> systemic inflammatory responses)
how do superantigens achieve polyclonal expansion?
the superantigens are present when the antigen on the antigen presenting cell, with the MHC II, binds with the toll like receptors on the T cell
how does Staphyloccus deal with the immune system?
- it is a well adapted human pathogen
- opportunisitic pathogen - always comes down to neutrophils vs staph
- LD50
how do the levels of LD 50 compare in a healthy and weak host?
- takes more LD50 to kill a healthy host
* takes less LD50 to kill a weak host
how do the levels of LD50 compare in a virulent staph and an attenuated host?
- less LD50 in a virulent staph
* more LD50 in an attenuated staph
How does staph react to the host immune response?
*staph has proteins that bind to Fc
what are staphs proteins that bind to Fc?
- protein A
- protein Sbi
- SSL7
- SSL10
binds to IgG
protein A
second binding protein of immunoglobulin
protein Sbi
staphyloccocal superantigen like protein 7
SSL7
binds to IgG
SSL10
what happens when staph proteins bind to Fc?
the cell is not available for phagocytosis
what happens in the complement system?
C3——-> C3a + C3b
chemoattractant
C3a
acts as a label for opsonization
C3b
- enzyme that cleaves C3
* pathogen activates this enzyme
C3 convertase
**refers to an immune process where particles such as bacteria are targeted for destruction by an immune cell known as a phagocyte
a means of identifying the invading particle to the phagocyte
opsonization
how does staph react to the complement system?
- SCIN
- staphylokinase
- Efb
- staphylococcal complement inhibitor
* inhibits C3 convertase
SCIN
*activates human protease—>degradation of C3b
staphylokinase
- extracellular fibrinogen binding protein
* binds C3 to prevent cleavage
Efb
what are the receptors of chemoattractants?
- **chemokines
1. C3a
2. CXC#
3. CXCL #
What does Staph do to inhibit chemoattractants?
- CHIPS
- FLIPr
- Staphopain A
- chemotaxis inhibitory proteins of S. aureus
* binds to receptor of chemoattractants
CHIPS
binds to receptors of chemoattractants
FLIPr
cleaves CXCR2 (protease)
staphopain A
needed to bind to adhesion molecules on endothelium for chemotaxis
neutrophils
What does staph do to inhibit adhesion molecules on the endothelium to prevent chemotaxis of neutrophils?
- SEIX
2. SSL5
- staphyloccocal enterotoxin like toxin X
* bind to neutrophils receptors for adhesion molecules
SEIX
bind to neutrophills receptors for adhesion molecules
SSL5
recognizes lipoproteins—->inflammation
TLR2
what does staph do to inhibit TLR2?
- staphylococcal iron transporter C (SITC)
2. SSL3
binds to TLR2 and blocks it from TLR2 signaling
SSL3
what does staph do to inhibit antimicrobial peptides (AMP+)?
- DLT
- MprF
- staphylokinase
- aureolysin
- forms biofilm
add D-alanine + to teichoic acid -, which increases electrostatic repulsion
DLT
add L-lysine + to phospholipid -, which increases electrostatic repulsion
MprF
binds AMP
staphylokinase
degrades AMP
aureolysin
secretes hydrolytic enzymes (degrade) and NETs (trap)
neutrophils
what does staph do to inhibit neutrophils?
- DNase
2. Eap
deal with NETs
DNase
- extracellular adherence protein
* inhibit proteases from neutrophils
Eap
what does staph do to inhibit neutrophils and ROS?
- superoxide dismutase
- catalase
- staphyloxanthin
- methionine sulfoxide
OH—> H2O2 + O2
superoxide dismutase
H2O2—-> O2 + H2O
catalase
- yellow pigment/cartenoid
* acts as antioxidant for staph
staphyloxanthin
reductase
methionine sulfoxide
- transmitted without awareness
- is everywhere
- multiple drug resistance
antibiotic resistance (Abx^R)
what was the earliest antibiotic?
tetracycline 350-500 BC
what was tetracylcine made by?
bacteria streptomyces in soil
enzyme that can cleave penicillin
B-lactamase
developed because B-lactamase cant cleave it
methicillin
where is MRSA commonly found?
- hospitals
* pigs/farms
what is B-lactamase encoded by?
gene blaZ
how many types of B-lactamase are there?
more than 100
resistance mechanism encoded by gene MecA
methicillin
encodes penicillin binding protein 2a (PBP2a)
gene MecA
has poor methicillin binding
transpeptidase
normal PBP vs. MecA PBP2a
- if you put two cultures together, normal PBP will grow faster
- If there is methicillin, normal PBP will be inhibited and MecA will grow faster
why can MRSA spread fast?
because MecA is found in the mobile genetic element
mobile genetic element of MRSA
staphyloccocal casette chromosome (SCC)
when does SCC have a higher expression?
if it is close to the origin of replication
allow multiple casettes to come together—-> resistance to multiple drugs
direct repeats
- binds to transpeptidase substrate— binds D-ala-D-ala
* no transpeptidation
vancomycin
- came from enterococcus
* resistance is on plasmid that can facilitate conjugation
Van^R
transfer plasmid to another bacteria
conjugation
- plasmid DNA
* jump to recipient and integrate to host DNA
transposon
what are the multiple gene products of Vancomycin?
- Van^R
- Van^x
- VanH
- VanA
cleaves D-ala-D-ala
Van^x
pyruvate—->D-lactate
VanH
synthesize D-ala-D-lactate
VanA
what are the antibiotic resistance mechanisms?
- alter Abx
- alter abx target
- decrease intracellular abx accumulation
- form biofilm
what does decreasing the intracellular abx accumulation involve?
- decrease porin (channels on outer membrane) expression
* increase eflux pump expression (transfer intracellular stuff to the outside)
How is antibiotic resistance being combatted?
- drug repurposing
- combination drug
- making derivatives of exhisting drugs/antibiotics
- rethinking antibiotic susceptibility testing
- discover new drugs
- random chemical sensing (targeted screening) microbiota
B lactam drug and B lactamase inhibitors
combination drug
what does rethinking antibiotic susceptibility testing?
MIC in artificial media
ihibits s.aureus and types of gram + bacteria
lugdunin
what happened when a human survey on lugdunin was conducted?
people positive for lugdunin have less s. aureus
Which of the following terms is most related/similar to “virulence”?
pathogenicity
Which of the following surface features of microbes can be used as tools for adhesion?
flagella
pili
capsule
True or False: Infection refers to a situation where foreign organisms have cause damages inside a host.
false
True or false: An opportunistic pathogen causes diseases when the host resistance is compromised.
true
A pathogen is more virulent if the LD50 is a larger number.
false
true or false: Dental plaque contains multiple species of microbes.
true
If you get rid of both of the pathogenicity islands in Salmonella, would the resulting mutant be less or more virulent than the wildtype bacteria?
less virulent
Pathogenicity islands can be mobile genetic elements and be transffered to a non-pathogen to make it become a pathogen.
true
True or false: Attenuated bacteria are dead bacteria
false
True or false: Pathogens may have a very specific host target that they bind to during infections.
true
true or false: Staphylococcus can cause infections in multiple sites of our bodies.
true
- a virulence factor produced by Staphylococcus aureus
- a bacterial enzyme with a human substrate
- the cause of fibrin accumulation around Staphylococcus aureus cells during infections
coagulase
true or false: Toxic shock syndrome is only caused by Staphylococcus aureus.
false
what is the purpose for including phenol red in mannitol-salt agar?
to indicate a reduction in pH
true or false: If a patient sample is positive for the presence of mecA gene, then methicillin should not be prescribed to that patient.
true
which of the following is NOT a function of neutrophils?
A. Chemotaxis
B. Secretion of antibodies
C. Phagocytosis
D. Production of reactive oxygen species
B secretion of antibodies
true or false: Macrophages are involved in cleaning up after neutrophils.
true
A Staphylococcus aureus mutant lacking catalase will not be able to?
survive through reactive oxygen species
true or false: Adding alanine to cell wall teichoic acids makes the bacteria have more negative charges at the surface.
false
**Staphyloccocus aureus also produces DNase to help evade immune defense mechanisms. Which of the following immune responses is most likely to be rendered ineffective by DNase?
A. Neutrophil extracellular traps
B. Antigen presentation
C. Production of reactive oxygen species
D. Phagocytosis
A. neutrophil extracellular traps
What evidence did the authors show to suggest that the genes encoding the synthesis of lugdunin are likely from other organisms?
GC content
How did the authors manage to purify lugdunin for in-depth chemical analysis?
Over-express the genes with a strong, inducible promoter
How did the authors test whether or not lugdunin has a toxic effect on mammalian cells
Lactate dehydrogenase release assay
True or false: An antibiotic is more potent if it has a high MIC
false
What is the specific molecular target of lugdunin?
it is unknown
Consider the fact that lugdunin is not produced when the bacteria are grown in liquid culture, what is the most likely outcome if you co-culture S. lugdunesis and S. aureus in liquid culture?
S. aureus growth is not inhibited
