3.8

Question 1

skipped

The Parasite’s Way of Life - Chapter 8 (6)

Answer 1

1. Surface colonization
2. Finding a nutritionally compatible niche
3. Surviving host defenses
4. Intracellular life
5. Subverting host immune responses
6. Transmission to a new host

Question 2

1. Surface colonization (3)

Answer 2

Preference of bacteria for particular locations in body
bacteria vary in specificity
tissue tropism
Adhesins on bacterium
Receptors on host cell

Question 3

bacterial proteins on the tips of fimbriae and/or

pili often interact with

Answer 3

glycolipids and/or

glycoproteins of host epithelial cells

Question 4

2. intimins (bacterial
   proteins at the the cell
   surface) interact with

Answer 4

their
own translocated intimin
receptor (TIR)

Question 5

Surface colonization (continued)
Examples:
gram-positive bacteria (e.g. Staphylococcus aureus)
often bind host — (epithelial cells), which binds to
—

Answer 5

fibronectin

integrins

Question 6

fibronectin binding proteins =

Answer 6

subclass of a large
family of bacterial adhesins referred to as Microbial
Surface Components Recognizing Adhesive Matrix
Molecules or MSCRAMMS

Question 7

Other MSCRAMM targets:

Answer 7

fibrinogen and collagen

Question 8

many individuals in poor health are —deficient

Answer 8

fibronectin

• balance shifts in favors of gram negatives
  e. g. greater incidence of pneumonias caused by gramnegative bacteria

Question 9

1. Surface colonization (continued)
   Examples:
   gram-positive bacteria
   serine rich repeat proteins (SRRPs) (= bacterial adhesins)
   contain a domain of hundreds of alternating serine residues
   Extend a unique non-repeat (NR) domain that mediates adhesion
   NR domain binds

Answer 9

sialic acid moieties, keratin, and other NR domains

of a similar SRRP

Question 10

sialic acid binding adhesins =

Answer 10

serine rich repeat proteins (SRRPs)

Question 11

Finding a nutritionally compatible niche (2)

Answer 11

Intermittent availability of food for some bacteria
e.g. intestinal bacteria
Adaptation to particular location

Question 12

Surviving host defenses

Answer 12

Defending against complement

masking and inhibition

Question 13

Defending against complement

masking and inhibition: Activation of complement Figure 6-1 (3)

Answer 13

C3a is an anaphylatoxin
(inducer of acute inflammation)

C3b is an opsonin and part of
C3 convertase (alt. pathway)
and C5 convertase

C5a is a chemotactic protein
for neutrophils and an
anaphylatoxin

Question 14

Microbial mechanisms to defend
against complement (4)

Answer 14

long chain smooth LPS limits access of MAC to the organisms surface
polysaccharide capsule masks surface compenents that can activate complement via the alternative pathway
addition of sialic acid to lipooligosaccaride inhibits complement fixation
c3b peptidase cleaves the component into inactive fragments

Question 15

3. Surviving host defenses

Subverting phagocytosis

Answer 15

inhibiting phagocyte recruitment and function
C5a peptidase production (see figure)
Increasing cAMP to inhibitory levels

Question 16

killing phagocytes:

Answer 16

leukocidins

Question 17

escaping ingestion:

Answer 17

protein A (Staphylococci and Streptococci)
expressed on bacterial cell surface
binds Fc portion of IgG (wrong end)
these bound antibodies cannot act as opsonins

Question 18

surviving inside phagocytes (4)

Answer 18

inhibit lysosomal fusion with
phagosome
escape into the cytoplasm
(form pores in phagosome)
resist lysosomal enzymes
inhibit phagocyte’s oxidative
pathway (respiratory burst)

Question 19

Penetration of nonphagocytic host cells:

Answer 19

Some bacteria enter host cells by stimulating host cell membrane protrusion

Question 20

internalins

Answer 20

(bacterial
proteins at the the cell
surface) interact with
host E-cadherin

Question 21

invasins

Answer 21

(bacterial
proteins at the the cell
surface) interact with
host integrins

Question 22

. Transmission to other cells (2)

Answer 22

tissue damage

cell-to-cell transmission

Question 23

Subverting immune responses (4)

Answer 23

immunosuppression
superantigens (diverting lymphocyte function)
changing antigenic coats
proteolysis of antibodies

Question 24

Transmission to a new host

Answer 24

judgment of transmission as passive or active can be arbitrary
consider effects on host