Micro 2- antimicrobial drugs Flashcards Preview

ABS > Micro 2- antimicrobial drugs > Flashcards

Flashcards in Micro 2- antimicrobial drugs Deck (35):
1

chemotherapy

the use of chemicals to treat a disease

2

antibiotic

a substance produced by a microbe that, in small amounts, inhibits another microbe
(example: streptomyces)

3

antimicrobial drug

synthetic substances that interfere with the growth of microbes

4

selective toxicity

selectively finding and destroying pathogens without damaging the host

5

narrow spectrum of microbial activity

drugs that affect a narrow range of microbial types

6

broad-spectrum antibiotics

affect a broad range of gram positive and gram negative bacteria

7

bactericidal

kills microbes directly

8

bacteriostatic

prevent microbes from growing

9

what is a superinfection and how is it caused

overgrowth of normal microbiota that is not sensitive to antibiotics (candida albicans)
-growth of target pathogen that has developed resistance to antibiotics

10

superinfection is a disadvantage of

broad spectrum drugs

11

5 ways antimicrobial drugs target essential functions of the microbe

1. inhibition of cell wall synthesis
2. inhibition of protein synthesis
3. inhibition of nucleic acid replication and transcription
4. injury to plasma membrane
5. inhibition of essential metabolite synthesis

12

example of cell wall synthesis inhibitor and how it works

penicillin, contains beta-lactam ring and prevents the cross-linking of peptidoglycan, interfering with cell wall construction (primarily gram-positives)

13

natural penicillins are

-extracted from penicillium cultures, G (injected) and V (oral)
-narrow spectrum of activity
-susceptible to penicillinases (Beta-lactamases)

14

semisynthetic penicillins

contain chemically added side chains, making them resistant to penicillinases

15

list of inhibitors of protein synthesis

1. aminoglycosides (including streptomycin)
2. chloramphenicol
3. tetracyclines

16

aminoglycosides

-amino sugars linked by glycoside bonds
-change the shape of the 30S subunit of the 70S ribosome
-can cause auditory damage
-streptomycin, neomycin, gentamicin

17

chloramphenicol

-inhibits peptide bond formation
-binds to 50S subunit of the 70S ribosome
-synthesized chemically, broad spectrum
-can suppress bone marrow and affect blood cell formation

18

tetracyclines

-produced by streptomyces spp.
-interfere with the tRNA attachment to the ribosome
-broad spectrum, penetrate tissues, making them valuble against rickettsias and chlamydias
-can suppress normal intestinal microbiota

19

what substances injury the plasma membrane

1. lipopeptide
-includes daptomycin and polymixin B

20

daptomycin
(type of lipopeptide)

-produced by streptomycetes, used for skin infections
-attacks the bacterial cell membrane

21

polymixin B
(type of lipopeptide)

-topical, bacteriocidal, effective against gram negatives
-combined with bacitracin and neomycin in nonprescription ointments

22

how do "inhibiting synthesis of essential metabolites" work

-antimetabolites compete with normal substrate for enzyme
-sulfonamides compete with para-aminobenzoic acid (PABA), stopping the synthesis of folic acid
-folic acid needed for nucleic acid and protein synthesis

23

types of inhibitors of nucleic acid synthesis

-rifamycin
-quinolone and fluoroquinolones
(nalidixic acid, norfloxacin and ciprofloxacin)

24

rifamycin

inhibits mRNA synthesis
-penetrates tissues, antitubercular activity

25

quinolone-
nalidixic acid

synthetic, inhibits DNA gyrase

26

quinolone-
norfloxacin and ciprofloxacin

broad spectrum, relatively nontoxic

27

list 2 types of diffusion methods

1. disk-diffusion method (Kirby-Bauer)
2. E test

28

disk diffusion method (Kirby Bauer)

-tests the effectiveness of chemotherapeutic agents
-paper disks with chemotherapeutic agent are placed on agar containing the test organism
-zone of inhibition around the disk determines the sensitivity of the organism to the antibiotic

29

E test

determines the minimal inhibitory concentration (MIC)
-lowest antibiotic concentration preventing bacterial growth

30

broth dilution tests

-determine the MIC and minimal bacterial concentration (MBC) of an antimicrobial drug
-test organism is placed into the wells of a tray containing dilutions of a drug, growth is determined

31

what are antibiograms

reports that record the susceptibility of organisms encountered clinically

32

what are persister cells

microbes with genetic characteristics allowing for their survival when exposed to an antibiotic

33

superbugs

bacteria that are resistant to large numbers of antibiotics

34

how are resistance genes spread

often spread horizontally among bacteria on plasmids or transposons via conjugation or transduction

35

list of mechanisms of resistance

-enzymatic destruction or inactivation of the drug
-prevention of penetration to the target site within the microbe
-alteration of the drug's target site
-rapid efflux (ejection) of the antibiotic
-variations of mechanisms of resistance