lecture 5 (12) paracites, normal biota, infetions

Question 1

what two things does the word niche include

Answer 1

food and shelter for an organism

Question 2

staphyloccocous epidermis

Answer 2

• normal biota that lives on skin, nose and ears
• gram + cocci in clusters
• associated with infections with prosthetic devices and intravenous catheters
• common contaminant of blood cultures

Question 3

Group A genes (GAS) streptococcus pyogenes

Answer 3

• pyo sounds like pyro-and it feels like your throat is on fire!
• causative agent of strep throat
• a normally transient microbiota
• gram +, chain
• colonize oropharynx of kids and young adults in absence of clinical disease

Question 4

what are four examples of opportunistic infections

Answer 4

1) contamination of intravenous catheters- staphylococcus epidermis, staphylococcus aureus (MRSA)
2) wound surgical site- staphylococcus aureus, lebsiella pneumonia, pseudomonas aeruginosa
3) bacterial endocarditis- damage to inner lining of heart via streptococci viridians group
4) aspiration pneumonia- inhalation of fluid into lungs gives bacterial growth and is a polymicrobial disease

Question 5

what are urinary tract infections caused by? psuedomembrane colitis, otitis media?

Answer 5

UTI- Escherichia coli
Pdeudomembrane colitis- Clostridium difficile (c.Diff)- dur to antibiotic therapy that disrupts microbiota of the colon and c diff spores survive and over grow causing disease
otitis media- middle ear infection mainliy in kids over 5- streptococcus pneumonia, nontypeable Haemophilus influenza and Moraxella catarrhalis

Question 6

pathogenicity vs virulence

Answer 6

pathogenicity- ability to cause disease

virulence - measure of pathogenicity

Question 7

virulence factors

Answer 7

factors produced by pathogens that enable them to infect and cause disease or kill

Question 8

Carrier state-

ex-

Answer 8

-means that you can carry a disease but not show any symptoms but you can transmit disease to others-may be transient or semi permanent
ex- GAS- group A streptococcus pyogenes (strep throat) and salmonella Typhi (Typhoid Mary-cook)

Question 9

define adhesion of bacteria and state how it’s done most of the time

Answer 9

adhesion is the binding of the bacteria to the host cell surface (receptor)
usually, adhesion or attachment proteins associated with bacterial pili

Question 10

Biofilms

Answer 10

• most bacteria are sessile (stationary)- adherent to a surface as part of a BIOFILM
• most bacteria do not live planktonically (freely moving in solution)
• they are encased in exopolymeric substance like polysaccardide, DNA and protein of their own making
• usually found in moist/wet environments

Question 11

what’s important to note about biofilms

Answer 11

• they are harder to treat with antibiotics than planktonic (free flowing) cells because they have slowed metabolism and a decreased diffusion of things in and out of the bacterium (thus no antibiotics in)
• they have an increased genetic exchange with can lead to antibiotic resistance being prevalent
• Have resistance to disinfection- less traffic in and out and have have increased organic matter

Question 12

what is a notable characteristic of bacterial infections that are chronic? ex?

Answer 12

they have biofilm
examples include catheter infections, intubation tubes and artificial joints, wound infections, otitis media, CF lung infections, dental plaque, gingivitis, endocarditis

Question 13

what is significant to note about the byproducts of bacteria

Answer 13

they often cause tissue destruction b/c they are acids and gas etc so they are often toxic to host cells

Question 14

what’s important to note about secretion of degradive enzymes by bacteria

Answer 14

they are secreted so bacteria can further embed theselves into host but causes lysis of cells that release nutrients that support growth of the bacteria

Question 15

exotoxin

Answer 15

• bacterial pdts that DIRECTLY harms tissue or leads to destructive biologic activities. have:
• cytosolic enzymes- hemolysins, pore forming toxins
• receptor binding proteins that initiate toxic reactions- have A and B subunit toxins- A=active, B=binding
• b binds and a acts on cell causing increase in cAMP leading to mass efflux of electrolytes and diarrhea

Question 16

what are three main effects of exotoxin

Answer 16

• inhibit protein synth
• hyperactivation
• effects muscle nerve-muscle transmission= paralysis or intense contraction

Question 17

C. diptherae

Answer 17

exotoxin that inhibits protein translation by using subunit B to bind, and A to actively inhibit elongation factor two and prevent translation

Question 18

v. cholerae

Answer 18

• exotoxin
• causes cholera when b binds and a actively upregulates cAMP and causes mass efflux of electrolytes out of cell and diarrhea

Question 19

c tetani

Answer 19

• exotoxin

- that causes overstimulation and massive fire of muscles =muscle spasms

Question 20

c. botulism

Answer 20

• exotoxin

- bocks acytl choline release causing flaccid muscles

Question 21

superantigen

Answer 21

• bind both T cell receptor and MHCII without requiring antigen
• activate large number of T cells causing a cytokine storm that is deadly
• ex s aureus, staphylococcal enterotoxin, s. pyogenes

Question 22

encapsulation

Answer 22

encapsulation is when a bacteria has a capsule that prevent antibody from biding via masking

Question 23

antigenic mimicry

2 ex

Answer 23

• when a bacteria coats itself with things that look like host “self” material or produces compounds itself that have the same effect.
  ex: s. pyogenes- coats itself in hyaluronic acid (found in human connective tissue)
  ex: s. aureus- has protein A that bind Fc portion of antibody thus coating bacteria in host protein

Question 24

antigenic variation/shift

ex

Answer 24

• bacteria change there cell surface proteins
• make for moving target for immune system
• ex: N. gonorrhoeae type IV pili- silent copies of pilin gene in genome

Question 25

what are six ways that bacteria escape phagocytic clearance

Answer 25

inhibit the lysosome fusion
inhibit chemotaxis (mvmt)
escape form lysosome
resistant to antibacterial lysosomal action
kill phagocyte 
inhibit opsonization