chapter 20: antimicrobial chemotherapy

Question 1

what are the major action modes of antibacterial drugs / antibacterial drug targets? (5)

Answer 1

1) inhibition of cell wall synthesis (penicillin)
2) inhibition of protein synthesis (erythromycin, tetracyclines, streptomycin)
3) inhibition of nucleic acid replication and transcription (quinolones, rifampin)
4) injury to plasma membrane (polymyxin B)
5) inhibition of essential metabolite synthesis (sulfanilamide, trimethoprim)

Question 2

mechanisms of antimicrobial resistance (4)

Answer 2

1) blocking of entry of the drug into the cell
2) inactivation / destruction of the antibiotic of enzymes
3) alteration of the target molecule so that the enzyme cannot affect it
4) efflux (pumping out) of the antibiotic

Question 3

antimicrobial resistance (AMR)

Answer 3

development by a disease-causing microbe (through maturation or gene transfer) w/ ability to survive exposure to an antimicrobial agent that was previously an effective treatment

Question 4

selective toxicity

Answer 4

selectively finding & destroying pathogens w/o damaging the host

Question 5

superbug

Answer 5

bacteria that are resistant to large numbers of antibiotics

- ex) methicillin-resistant staphylococcus aureus (MRSA), ESKAPE (nosocomial infections)

Question 6

mycoplasma

Answer 6

genus of bacteria that lack a cell wall around the cell membrane; naturally resistant to antibiotics that target cell wall synthesis
- ex) not being affected by penicillin

Question 7

beta lactamase

Answer 7

enzyme that targets beta lactam ring (part of chemical structure of many antibiotics)
- ex) allows microbes to destroy penicillin

Question 8

vertical gene transfer (for resistance)

Answer 8

through reproduction

Question 9

horizontal gene transfer (for resistance)

Answer 9

through sharing of plasmids or through viral action in transduction

Question 10

antimicrobial spectrum

Answer 10

range of microorganisms an antibiotic can kill or inhibit

Question 11

narrow spectrum of microbial activity

Answer 11

drugs that affect a narrow range of microbial types

- ex) penicillin G affects gram positive bacteria but very few gram negative bacteria

Question 12

broad spectrum antibitotics

Answer 12

affect a broad range of gram positive or gram negative bacteria
- ex) ciprofloxacin affects a wide variety of bacteria

Question 13

antibiotic

Answer 13

substance produced by a microbe that, in small amounts, inhibits another microbe

Question 14

allergy

Answer 14

condition in which the immune system reacts abnormally to a foreign substance
- ex) allergic to penicillin

Question 15

toxicity

Answer 15

toxins produced by microorganisms; organs getting damaged

- ex) drug-induced liver injury

Question 16

therapeutic index (TI)

Answer 16

quantitative measurement of the relative safety of a drug; comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity

Question 17

antifungals

Answer 17

agents affecting fungal sterols; interrupt synthesis of ergosterol making membrane excessively permeable
- ex) ergosterol inhibitors: amphotericin B= serious side effects; reserved for serious systemic infections
clotrimazole= safe; available over-the-counter; used orally or topically

Question 18

antivirals

Answer 18

entry & fusion inhibitors; block receptors on host cell that bind to virus; block fusion of virus & cell; very specific to one virus

Question 19

antiretrovirals

Answer 19

treat HIV/AIDS infections (recall HIV is an RNA virus)

Question 20

nucleoside reverse transcriptase inhibitors

Answer 20

category of antiretrovirals that inhibits the ability of HIV to use reverse transcriptase

Question 21

neuraminidase inhibitors

Answer 21

category of drugs that targets the ability of flu viruses to bud off from host cell

Question 22

antiprotozoan drugs

Answer 22

quinine (and derivatives) used to treat malaria; traces of this drug in tonic water

Question 23

antihelminthic drugs

Answer 23

drug treatment alone does not stop re-infection; best course in eradicating these diseases is implementation of effective sanitary systems (toilets & water treatment plants)

Question 24

synergism

Answer 24

effect of two drugs together is greater than effect of either alone; allows o lower doses of either drug; also inhibit development of resistance; two drugs inhibit same microbial pathway at different steps on pathway

Question 25

antagonism

Answer 25

effect of two drugs together is less than effect of either alone; one drug cancels effect of other drug;
- ex) bacteriostatic drugs stop growth which makes bactericidal drugs drugs which depend on rapid growth for their activity useless

Question 26

penicillin (importance)

Answer 26

• molecules produced by molds in the penicillium family (discovered by fleming)
• kills bacteria by inhibiting proteins which cross-link peptidoglycans in the cell wall

Question 27

isoniazid

Answer 27

antibiotic used to treat / prevent tuberculosis; inhibits formation of mycolic acid / mycobacterial cell wall; bactericidal to rapidly dividing mycobacteria & bacteriostatic if mycobacteria are slow growing

Question 28

tetracycline

Answer 28

growth inhibitors (bacteriostatic); broad spectrum agents; produced by streptomyes; interfere w/ tRNA attachment to ribosome; penetrate tissues making them vulnerable against rickettsias & chlamydias
- ex) used to treat pneumonia & other respiratory infections