CHAPTER 15 LEARNING OBJECTIVES

IDENTIFY THE PRINCIPLE PORTALS OF ENTRY

Mucous membranes

respiratory tract, gastrointestional tract, genitourinary tract

Skin

parenteral route

direct deposition beneath the skin or membranes

largest organ on body

DIFFERENTIATE PORTAL OF ENTRY AND PORTAL OF EXIT

Portal of entry: how microbes enter the body

Portal of exit: Microbes leave in secretions, excretions, discharges, or shed tissue

commonly through respiratory and gastrointestinal tracts

DEFINE ID50 AND LD50

ID50: infectious dose for 50% of sample population

LD50: Lethal dose for 50% of the population

USING EXAMPLES, EXPLAIN HOW MICROBES ADHERE TO HOST CELLS

The majority of adhesions are glycoproteins or lipoproteins

ex: pili, fimbriae, flagella

Also can adhere using biofilms: biofilms are masses of microbes and extracellular products. They cause 65% of human bacterial infections

EXPLAIN HOW CAPSULES AND CELL WALL COMPONENTS CONTRIBUTE TO PATHOGENICITY

Capsules

Cell wall components

Formed by glycocalyx material, resists hosts defenses and prevents phagocytosis

chemical substances contribute to virulence

M protein is heat and acid resistant/mediates attatchment; waxy lipid resists phagocytosis

COMPARE THE EFFECTS OF COAGULASES, KINASES, HYALURONIDASE AND COLLAGENASE

Coagulases: Bacterial enzymes that clot the fibrinogen in blood (fibrinogen is converted to fibrin)

Kinases: enzymes that break down fibrin and digest clots

Hyaluronidase: Hydrolyzes hyaluronic acid (polysaccharide that holds together cells in connective tissue; destroyed by lgA proteases)

Collagenase: Facillitates the spread of gas gangrene (breaks down collagen, which forms the connective tissues of muscles and other organs)

DEFINE AND GIVE AN EXAMPLE OF ANTIGENIC VARIATION

Definition: Ability of pathogens to alter their surface antigens

ex: gonorrhea, African sleeping sickness

By the time the body mounts an immune response, the pathogen has already altered its antigens

DESCRIBE HOW BACTERIA USE THE HOST CELL'S CYTOSKELETON TO ENTER THE CELL

Microbes produce surface proteins called invasins that rearrange nearby actin filaments (can cause ruffling)

DESCRIBE HOW SALMONELLA COMPETES WITH NATIVE BACTERIA IN THE INTESTINE

Salmonella uses type 3 secretion system (T3SS) to inject proteins that hijack the host

T3SS is used again to pump out proteins into cell from vacuole for survival and replication

DESCRIBE THE FUNCTION OF SIDEROPHORES

They gather iron for bacteria by taking away the iron from iron transport proteins of the cell

IDENTIFY SIX MECHANISMS OF AVOIDING DESTRUCTION BY PHAGOCYTOSIS