Antimicrobials

Question 1

Antibiotics

Answer 1

substances produced by microbes that can destroy or inhibit growth of other microbes

Question 2

Selective toxicity

Answer 2

-the ability to harm the microbial pathogen without causing significant harm to the host

Question 3

Therapeutic index

Answer 3

-ratio of the toxic dose to the therapeutic dose
-toxic dose: the median dose at which the drug is lethal to the host
-therapeutic dose: the median dose to effectively treat an infection

Question 4

true or false: the higher the therapeutic index the more specifically the drug harms the pathogen but not the host

Answer 4

True

Question 5

inhibitors of cell wall

Answer 5

-penicillin and cephalosporin inhibit the enzyme that catalyzes the cross linking of the murrain
-inhibition of cell wall synthesis triggers the lysis of actively growing bacteria in hypotonic conditions

Question 6

Drugs that disrupt cell membrane function

Answer 6

Polymyxins

Question 7

Inhibitors of protein synthesis

Answer 7

tetracycline, streptomycin, erythromycin, chloramphenicol

Question 8

Inhibitors of nucleic acid synthesis

Answer 8

-quinolones and rifampin

Question 9

Antimetabolites

Answer 9

Sulfa drugs—> competitive inhibitors of a bacterial enzyme involved in folic acid synthesis

Question 10

What happens if a patient does not finish a course of antibiotics?

Answer 10

-if a course of antibiotics is not finished then the bacteria that remain and multiply are the ones that are naturally more resistant to

Question 11

what are two broad categories of genetic changes that confer resistance

Answer 11

-spontaneous chromosomal mutation: alters the target enzymes binding site for the drug
–>usually confers resistance to a single type of antibiotic

-extrachromosomal Resistance :
R plasmids or R factors carry 6 or 7 genes for resistance to different antibiotics

Question 12

Outer membrane vesicles

Answer 12

-are derived from gram negative outer membranes
-can compete for binding antibiotics or phage
-can transfer antibiotic resistance genes or harbor enzymes that degrade antibiotics

Question 13

Antifungal Drugs

Answer 13

-mode of action: many anti fungal drugs exploit differences between human and fungal cell membranes

Question 14

What is the difference between a human cell membrane and fungal membrane?

Answer 14

-human cell membrane have cholesterol
-fungal cell membranes contain ergosterol

Question 15

what are examples of antifungal drugs?

Answer 15

imidazole inhibit ergosterol synthesis
-nystatin binds to ergosterol in the cell membrane and disrupt the cell membrane

Question 16

Antiviral Drugs

Answer 16

Mode of action: many antiviral are nucleotide analogs that inhibit viral nucleic acid synthesizing enzymes

Question 17

what is the function of monoclonal antibodies?

Answer 17

-binds to the spike protein and prevent the virus from attaching to human cells and tag it for destruction

Question 18

Modes of actions of chemical antimicrobial agents

Answer 18

-react with macromolecules of microbes or change the local environment around microbes to
–> denature and inactivate proteins
–> disrupt cell membrane
–>disrupt nucleic acids

Question 19

Phenolics and alcohols

Answer 19

-denature proteins and disrupt membranes

Question 20

CHEMICAL ANTIMICROBIAL AGENTS: HALOGENS, ALDEHYDES, AND HEAVY METALS

Answer 20

-halogens: react with proteins, membranes, and nucleic acids
-aldehydes: react with proteins and nucleic acids
-heavy metals: react with proteins

Question 21

Name three antiviral drugs against SARS-CoV2 and describe their mode of action

Answer 21

1. Molnupiravir: causes many mutations in the genome of SARS-CoV2
2. Remdesivir: inhibits the RNA replicase of coronaviruses
   3.AZT: inhibits reverse transcriptase

Question 22

How is sterilization different than disinfection?

Answer 22

Sterilization decreases the number of microbes to levels that meet public health standards
-Disinfection–> is used to kill or inhibit microbes on objects

Question 23

Bactericidal vs Bacteriostatic

Answer 23

-kills bacteria; minimum concentration of antibacterial needed to kill the bacteria

-inhibits bacterial growth; minimum concentration of antibacterial needed to inhibit bacterial growth

Question 24

Ways in which bacteria become resistant to antibiotics

Answer 24

-spontaneous chromosomal mutation
(altering target enzyme’s ending site for the drug)
-extrachromosomal mutations
(R plasmid)
-mutation of the target enzyme or protein so antibiotic can no longer bind
(point mutation)
-inactivation of antibiotic by chemical modification (via point mutation)
–> ex: beta lactamase
-preventing antibiotic entry into the cell by decreasing cell permeability
(via point mutation)
-by passing the target enzyme
(need the acquisition of new genes)
-pumping the drug out of the cell immediately
(via point mutation)