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Flashcards in BacT lecture 4 Deck (49):
1

What is an antibiotic?
(eg. gentamicin, streptomycin)

A chemical substance produced by a *microorganism that inhibits the growth of or kills other microorganism

2

A chemical substance derived form a biological source or produced by chemical synthesis that kills or inhibits the growth of microorganisms

Antimicrobial agent
(eg sulfonamide, enrofloxacin)

3

When do we use antibiotics or antimicrobial agents?

When body's normal defenses cannot prevent or overcome disease
Must act with in the host without damaging the host
Disinfectants and antiseptics act outside the body of the host

4

Who and how was penicillin discovered?

Alexander Fleming- It was an accident

5

Sources of Chemotherapeutic Antimicrobial Agents

Natural (true antibiotics)
Semi-synthetic
Synthetic

6

Where do Natural Antimicrobial Agents come from?

Fungal and bacterial
benzyl penicillin, gentamicin, streptomycin, chlortetracycline
Streptomyces, Bacillus, Penicillium

7

What are Semi-synthetic Antimicrobial Agents?

Chemically-altered natural compound
ampicillin, amikacin

8

What are Synthetic Antimicrobial Agents?

Chemically designed in the lab
sulfonamide, enrofloxacin, marbofloxacin

9

What are the classification of antimicrobial agents?

Chemical family structure
Mode of action
Type of antimicrobial activity
Spectrum of antibacterial activity

10

Draw the distinguishing characteristic of Beta Lactams

Refer to slide 8 of lecture 4 BacT

11

Mode of action (functional groups)

Inhibitors of cell was synthesis
Inhibitors of protein synthesis
Inhibitors of nucleic acid synthesis
Inhibitors of membrane function
Anti-metabolites

12

Cell wall synthesis inhibitors

Beta lactam antibiotics
Penicillin, ampicillin, cephalosporins, carbapenem, monobactam

13

What do cell wall synthesis inhibitors beta lactam antibiotics work?

Inhibit peptidoglycan synthesis
Bind and inhibit a group of proteins called penicillin binding proteins

14

What is an enzyme present in bacteria which can cleave beta lactam ring and inactivate penicillin and contribute to resistance?

Beta Lactamase

15

Clauvulanic acid does what?

(suicide substrate) prevent degradation of penicillin by beta lactamase

16

Cell wall synthesis inhibitors Glycopeptides

Vancromycin, daptomycin
Last drugs of choice for some gram-pos bacteria
V resistance - increasing

17

Protein Synthesis inhibitors

Aminoglycosides
Tetracyclins
Macrolides
Phenocols
Lincosamides

18

Antibiotic examples of Aminoglycosides and which protein subunit do they inhibit?

Gentamicin, amikacin, kanamycin, streptpmycin
30s subunit

19

Antibiotic examples of Tetracyclins and which protein subunit do they inhibit?

Oxytetracycline, chlortetracycline
30s subunit

20

Antibiotic examples of Macrolides and which protein subunit do they inhibit?

Erythromycin, azithromycin
50s subunit

21

Antibiotic examples of Phenocols and which protein subunit do they inhibit?

Chloramphenicol
50s subunit

22

Antibiotic examples of Lincosamides and which protein subunit do they inhibit?

Clindamycin
50s subunit

23

DNA synthesis inhibitors

Quinolones
Metronidazole

24

Examples if quinolone and what do they do?

Nalidixic acid, ciprofloxacin
*Inhibit enzyme DNA gyrase

25

What is the resistance of quinolones due to?

A mutation in the gene for enzyme DNA gyrase

26

What does metronidazole?

Makes breaks in the DNA

27

What are the RNA synthesis inhibitors?

Rifampin
Mupirocin

28

What does rifampin do?

Inhibit RNA polmerase (transcription)
Active against Mycobacterium tuberculosis
Extremely multidrug resistance TB

29

What does mupirocin do?

Inhibit tRNA synthetase (translation)
Commonly used for MRSA

30

What are the folic acid synthesis inhibitors and what do they do?

(antimetabolites)
Sulfonomides
Trimethoprim
Competitive inhibitors of dihydrofolate reductase

31

Types of antimicrobial activity. What is Bacteriostatic Activity?

Inhibition of bacterial multiplication/growth
Visual inhibition of bacterial growth is the basis of routine susceptibility testing

32

In a drug dilution series, the lowest drug concentration that completely *inhibits bacterial growth is?

Minimal Inhibitory Concentration (MIC)

33

In a drug dilution series, the lowest drug concentration that *kills the bacterial population is?

Minimal Bactericidal Concentration (MIB)

34

Broad vs Narrow spectrum antibiotics

Broad spectrum active against a wide variety of bacteria (Tetracycline)
Narrow spectrum only work on a select few bacteria (Penicillin)

35

How do you know certain bacteria is susceptible to a particular antibacterial?

Antibacterial Susceptibility Testing; either Dilution or Diffusion

36

Disk Diffusion (Kirby Bauer testing)

Single- concentration disk
Growth inhibition zone diameter measured
Use published reference break points to interpret results

37

Broth Dilution

One to multiple dilutions of antibiotic
Measure and report growth inhibition endpoint (MIC)
Use published references breakpoints to interpret
Susceptible, Intermediate, Resistant

38

Susceptibility Results

S- High likelihood of therapeutic success
I- Uncertain therapeutic outcome
R- High likelihood of therapeutic failure

39

In MRSA and Pseudomonas aeruginosa, targeting quorum sensing provides for

Regulatory control over genes

40

4 types of horizontal gene transfer

Lysogenic conversion (transduction)
Transduction (generalized transduction)
Conjugation
Transformation

41

Lysogenic conversion (transduction)

Bacterphage DNA into a bacteria cell

42

Transduction (generalized transduction)

bacterial DNA into another bacteria via virus

43

Conjugation

Plasmids

44

Transformation

Uptake of exogenous DNA

45

Mobile genetic elements

Insertion sequences
Transposons

46

Types of resistance

Innate - preexisting genomic property
Acquired - new genetically encoded trait not representative of the species (acquired by mutation or horizontal gene transfer

47

Mechanisms of resistance

Enzymatic destruction or inactivation of drug
Prevention of penetration to target sites within microbe
Alteration of drugs target site
Rapid efflux of antibiotics

48

Consequences of antimicrobial resistance

Increased mortality to infectious disease
Increased nosocomial infections
High treatment costs
Decreased development of new drugs

49

Almost all bacterial are acquiring resistance to antibacterial because

Widespread antimicrobial use
Microbial adaptation and change
Change in demographics
Medical advances
Change in ecosystems
Cutbacks in public health systems and surveillance