Lecture 10

Question 1

What is the goal of antimicrobial chemotherapy?

Answer 1

administer a drug to an infected person that destroys the infective agent without harming the host’s cells (selective toxicity)

Question 2

Chemotherapeutic drug

Answer 2

any chemical used in the treatment, relief, or prophylaxis of a diease

Question 3

Prophylaxis

Answer 3

the use of a drug to prevent imminent infection of a person at risk

Question 4

Antimicrobials

Answer 4

all inclusive term for any antimicrobial drug no matter its origin

Question 5

Antibiotics

Answer 5

substances produced by the natural metabolic processes of some microorganisms that can inhibit or destroy other microorganisms

Question 6

semisynthetic durgs

Answer 6

natural resources that are chemically modified in the lab

Question 7

synthetic drugs

Answer 7

drugs produced by chemical reactions

Question 8

Why are antibiotics produced and what are they derived from?

Answer 8

• are common metabolic products of aerobic bacteria and fungi
• produced to inhibit the growth of competing microbes in the same habitat

Derived from
bacteria in the genera Streptomyces and Bacillus

molds in the genera Penicillium and Cephalosporium

Question 9

What is the kirby-baurer techinque testing for drug susceptibility?

Answer 9

surface of an agar plate is spread with bacteria

small discs containing a prepared amount of antibiotic are placed on the plate

zone of inhibition surrounding the discs is measured and compared with a standard for each drug

antibiogram provides data for drug selection

this method is less effective for anaerobic, fastidious, or slow-growing bacteria

Question 10

What is the tube dilution test for testing for drug susceptibility?

Answer 10

more sensitive and quantitative than the Kirby- Bauer test

antimicrobial is diluted serially in tubes of broth

each tube is inoculated with a small uniform sample of pure culture

useful in determining the effective dosage and providing a comparative index against other antimicrobials

Question 11

What is the therapeutic index?

Answer 11

-the ratio of the dose of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose

-the smaller the ratio, the greater the potential for drug reactions
Toxic dose ÷ MIC
The closer this is to 1, the more toxic it is.

Question 12

What are the goals of antimicrobial drugs?

Answer 12

disrupt cell processes or structures of bacteria, fungi, or protozoa

inhibit virus replication

interfere with the function of enzymes required to synthesize or assemble macromolecules

destroy structures already formed in the cell

Question 13

What is selectively toxic?

Answer 13

kill or inhibit the actions or synthesis of molecules in microorganisms but not vertebrate cells

Question 14

What do drugs with excellent selective toxicity do?

Answer 14

block the synthesis of the bacterial cell wall (penicillins)

Question 15

What drugs are most toxic to humans?

Answer 15

drugs that act upon a structure common to both the infective agent and the host cell (cell membrane)

Question 16

What is minimum inhibitory concentration (MIC)?

Answer 16

the smallest concentration (highest dilution) of drug that visibly inhibits growth

Question 17

What are the goals of chemotherapy?

Answer 17

identifying structural and metabolic needs of a living cell and removing, disrupting, or interfering with these requirements

Question 18

What are the antimicrobial drug categories?

Answer 18

inhibition of cell wall synthesis

inhibition of nucleic acid structure and function

inhibition of protein synthesis

interference with cell membrane structure and function

inhibition of folic acid synthesis

Question 19

facts about penicilins

Answer 19

original penicillin was narrow-spectrum and susceptible to microbial counterattacks

molecule has been altered and improved upon over the years

later penicillins overcome the limitations of the original molecule

Question 20

Are Biofilms unaffected or affected by the same antimicrobials that work against them when they are free living?

Answer 20

unaffected

Question 21

What are the stragies for treating biofilm infections?

Answer 21

interrupting quorum sensing signals

adding DNase to antibiotics helps with penetration

impregnating devices with antibiotics

Question 22

What is quinine?

Answer 22

principal treatment of malaria for hundreds of years

has been replaced by synthesized quinolones, chloroquine and primaquine

several species of Plasmodium and many stages in its life cycle means that no drug is universally effective

Question 23

What is metronidazole?

Answer 23

widely used amoebicide
treats intestinal infections and hepatic disease caused by Entamoeba histolytica

also treats Giardia lamblia and
Trichomonas vaginalis

Question 24

What are the challenges of antihelminthic drug therapy?

Answer 24

flukes, tapeworms, and roundworms are larger parasites

their physiology is much more similar to humans

blocking reproduction does not affect adult worms

most effective drugs immobilize, disintegrate, or inhibit the metabolism of all stages of the life cycle

Question 25

What are the unique challenges of antiviral chemotherapeutic agents?

Answer 25

infectious agent relies on a host cell for the vast majority of its metabolic functions

disrupting viral metabolism requires disruption of cellular metabolism

measles, mumps, and hepatitis are prevented through the use of vaccines

AIDS, influenza, and the common cold attest to the need for more effective medications for the treatment of viral infection

Question 26

What are the modes of action of antiviral agents?

Answer 26

barring penetration of the virus into the host cell

blocking transcription and translation of viral molecules

preventing maturation of viral particles

Question 27

What is drug resistance?

Answer 27

an adaptive response in which microorganisms begin to tolerate an amount of drug that would normally be inhibitory

due to the genetic versatility and adaptability of microbial populations

can be intrinsic as well as acquired

Question 28

When do microbes become newly resistant to a drug?

Answer 28

pontaneous mutations in critical chromosomal genes

acquisition of entire new genes or sets of genes via horizontal transfer from another species

Question 29

What was the original wonder drug and how was it formed?

Answer 29

pencilin and by fungus

Question 30

What is chromosomal drug resistance and what does it result from?

Answer 30

usually results from spontaneous random mutation

slight changes in drug sensitivity can be overcome with larger doses of drug

can be the result of a phenotypic, rather than a genotypic change; slowing or stopping of metabolism so that the microbe can’t be harmed by the antibiotic