Exam 1 study guide

Question 1

1. There are 6 steps in the infectious disease process

Answer 1

encounter, 2. entry, 3. spread, 4. multiplication, 5. damage and 6. outcome. (You should know what each step is).

Question 2

1. Entry into a host can be thought of as two different processes

Answer 2

1) ingress of microorganisms into body cavities that are contiguous with the outside (inhalation or ingestion) 2) penetration of microorganisms into deeper tissues after crossing an epithelial barrier (insect bites, cuts and wounds, organ transplants, blood transfusions)

Question 3

1. The nose, mouth, respiratory tract, alimentary canal, anus, female genital tract and urinary tract are all in

Answer 3

direct contact with the exterior and are therefore generally not considered inside the body

Question 4

1. Penetration of bacteria into epithelial cells usually involves two steps

Answer 4

attachment to specific receptors followed by internalization

Question 5

1. The spread of infection can have two meanings

Answer 5

the lateral propagation (or movement) to contiguous tissues or dissemination to distant sites.

Question 6

1. Microbes must overcome host defenses in order to

Answer 6

multiply and spread

Question 7

1. Inoculum size is important in establishing an

Answer 7

infection (it varies with different organisms).

Question 8

1. There are 4 possible outcomes of a host-parasite interaction

Answer 8

: 1) the host wins out and clears the infection. 2) the parasite overcomes the host. 3) the host and parasite adapt to each other. 4) neither host or parasite win. This chronic infection can continue indefinitely.

Question 9

1. Damage to the host can be caused by the

Answer 9

infectious agent or by the host response (immune system) or both.

Question 10

1. The great majority of microorganisms are

Answer 10

commensal. They coexist without causing harm. It can be difficult to identify a bacterium as a commensal.

Question 11

1. Gram positive bacteria have

Answer 11

a thick cell wall made up of murein (peptidoglycan). Murein is made up of long chains of N-acetylmuramic acid and N-acetylglucosamine linked together by short polypeptides.

Question 12

1. Gram negative bacteria have a thin

Answer 12

layer of murein between two membranes (lipid bilayers).

Question 13

1. The outside of the outer membrane of gram negative bacteria is made up of

Answer 13

lipopolysaccharide (LPS) that is different for different bacteria.

Question 14

LPS

Answer 14

toxic (endotoxin) even in its purified form. LPS is made up of a lipid region (fatty acids attached to a phosphorylated disaccharide) that faces into the membrane and a polysaccharide region face out. The outer (O-antigen) region in highly variable and antigenic.

Question 15

1. Bactericidal agents kill

Answer 15

baceteria - bacteriostatic do not.

Question 16

1. Penicillins and other beta-lactams are

Answer 16

antibiotics that affect the cell wall. They are bactericidal.

Question 17

1. Antibiotics often work by targeting

Answer 17

bacterial ribosomes

Question 18

1. There are 2 subunits to bacterial ribosomes

Answer 18

the 30S and 50S subunit

Question 19

1. The 30S subunit is primarily responsible for

Answer 19

translation of mRNA

Question 20

1. The 50S subunit is primarily responsible for

Answer 20

joining amino acids together and moving the complex along the mRNA molecule.

Question 21

1. Antibiotics can target either the

Answer 21

30S or 50S subunit.

Question 22

1. Sulfonamides and trimethoprim inhibit

Answer 22

folic acid metabolism

Question 23

1. Aminoglycosides (streptomycin, kanamycin etc.) tetracyclines and erythromycin inhibit

Answer 23

protein synth

Question 24

1. Metronidazole inhibits

Answer 24

DNA synthesis.

Question 25

1. Pili (or fimbriae) are specialized structures on the surface of bacteria that are involved in

Answer 25

adhesion to cells or other surfaces

Question 26

1. Sex pili are specialized pili that

Answer 26

link a donor cell to a recipient cell during transfer of DNA.

Question 27

1. Flagella are surface structures used for

Answer 27

locomotion. They cause movement when they rotate counterclockwise and tumbling when they rotate clockwise

Question 28

1. Flagellar movement is used by bacteria for

Answer 28

chemotaxis - the movement towards substances that attract and away from substances that repel

Question 29

1. Obligate intracellular parasites can only grow

Answer 29

inside host cells

Question 30

1. The therapeutic index is the

Answer 30

1. ratio between the effective and toxic dose of an antibiotic

Question 31

1. Antibiotics tend to target structures that are

Answer 31

“unique” in bacteria compared to structures found in host cells. You should know what those targets are.

Question 32

1. The sulfa drugs interact with an

Answer 32

enzyme to prevent the production of a metabolite. You should know what that metabolite is, why it’s important, and why this competition is damaging to the host.

Question 33

1. Bacteria can become resistant to antibiotics by

Answer 33

synthesizing enzymes that inactivate the drug, inhibiting uptake of the drug, increasing secretion of the drug (pumping it out of the cell), modifying the target of the drug

Question 34

1. Drug resistant genes are often found on

Answer 34

plasmids that can be transferred readily from one bacteria to another.

Question 35

1. In order to survive as an infectious agent, bacteria must:

Answer 35

1) avoid being washed away, 2) find a nutritionally compatible niche, 3) survive host defenses, 4) transfer to a new host.

Question 36

1. Damage to a host as a result of infection can be caused by

Answer 36

cell death, pharmacological alterations of metabolism, mechanical causes, host responses, or bacterial toxins.

Question 37

1. Many structures on the microbial surface consists of repeated molecules---

Answer 37

referred to as pathogen associated molecular patterns

Question 38

1. Pattern recognition receptors recognize

Answer 38

pathogen associated molecular patterns.

Question 39

1. Bacteria are often classified via their

Answer 39

surface antigens (referred to as the serotype). In this scheme, O refers to LPS, H refers to flagella, and K refers to a capsule.