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Flashcards in Bacteriology 4 Deck (46)
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1
Q

What are methods used to limit microbial growth?

A

Refrigerate, freeze, boil, pasteurization, acidification, increase osmotic pressure, oxygen removal, drying, gamma irradiation, hydrostatic pressure, chemical additives

2
Q

What are some sterilization methods?

A

Autoclave (moist heat), dry heat, incineration, alcohol flame, gamma irradiation, UV light, membrane filtration, or chemicals

3
Q

What are drugs that destroy microbes, prevent their multiplication or growth or prevent their pathogenic effect?

A

Antimicrobials

4
Q

Who discovered penicillin?

A

Alexander Fleming

5
Q

What is an antibiotic?

A

A low molecular substance produced by a

microorganism that at a low concentration inhibits or kills other microorganisms.

6
Q

What is an antimicrobial?

A

Any substance of natural, semisynthetic
or synthetic origin that kills or inhibits the growth of
microorganisms but causes little or no damage to the host.

7
Q

T/F: All antibiotics are antimicrobials, but not all antimicrobials are antibiotics.

A

True

8
Q

What are natural antimicrobials?

A

Produced by bacteria or fungus- Streptomycin, penicillin, tetracycline

9
Q

What are semi-synthetic antimicrobials?

A

Chemically altered natural compounds- ampicillin, amikacin

10
Q

What are synthetic antimicrobials?

A

Chemically designed in the lab- sulfonamide, enrofloxacin, marbofloxacin

11
Q

How are antimicrobial agents classified?

A
  • Chemical structure
  • Mode of action
  • Type of antimicrobial activity
  • Spectrum of antimicrobial activity
12
Q

What are the different chemical structure families of antimicrobials?

A

Macrolide, Aminoglycoside, Tetracycline, Beta Lactams, Sulfonamides

13
Q

Examples of β lactam antibiotics?

A

Penicillin, ampicillin, cephalosporins

14
Q

What do β lactam antibiotics do?

A
Inhibit peptidoglycan (cell wall) synthesis.
Also bind and inhibit penicillin binding proteins.
15
Q

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

A

β lactamase

16
Q

What prevents degradation of penicillin by β lactamase?

A

Clavulanic acid

17
Q

What do Aminoglycosides do?

A

Inhibit protein synthesis (30s subunit of bacterial ribosome)

18
Q

Give some examples of 30S protein synthesis inhibitors?

A

Tetracyclines, Streptomycin, Gentamicin, Amikacin

19
Q

Give some examples of 50S protein synthesis inhibitors.

A

Erythromycin, Azithromycin, Chloramphenicol, Clindamycin, Lincomycin

20
Q

Which antibiotic aids in inhibition of DNA synthesis?

A

Quinolones- Ciprofloxacin, Enroflaxacin, Metronidazole

21
Q

With respect to DNA synthesis inhibition, what is resistance due to?

A

Mutations in the gene for DNA gyrase

22
Q

What does Metronidazole do?

A

Makes breaks in the DNA

23
Q

What are 2 RNA Synthesis Inhibitors?

A

Rifampin and Mupirocin

24
Q

What antibiotic inhibits tRNA synthetase (Translation)?

A

Mupirocin

25
Q

What antibiotic inhibits RNA polymerase (Transcription) and is active against Mycobacterium tuberculosis?

A

Rifampin

26
Q

What are Sulfonamides and Trimethoprim responsible for?

A

Competitive inhibitors of dihydrofolate reductase. –> Folic acid synthesis inhibitors

27
Q

What are broad spectrum antibiotics? Give 1 example.

A

Active against gram (+) and (-) bacteria

Tetracycline

28
Q

What are narrow spectrum antibiotics? Give 1 example.

A

Limited activity, useful against a particular species of either gram (+) or gram (-) bacteria.
Tobramycin

29
Q

What is the difference between Bactericidal and Bacteriostatic activity?

A

Bactericidal- kills bacteria

Bacteriostatic- inhibits bacterial growth

30
Q

Give some examples of Bactericidal antibiotics.

A

Aminoglycosides, β lactams, Fluoroquinolones, Metronidazole (narrow spectrum)

31
Q

Give some examples of Bacteriostatic antibiotics.

A

Tetracyclines, Clindamycin, Macrolides, Sulfonamides, Trimethoprim (broad spectrum)

32
Q

Antimicrobial Susceptibility Testing (AST)

A

A lab test to determine whether a bacteria is

susceptible to a particular antimicrobial agent.

33
Q

What are two types of AST?

A
  1. Disk diffusion test( Kirby Bauer test)

2. Broth/Agar Dilution Test

34
Q

What is Minimum inhibitory concentration (MIC)?

A

Minimum amount of drug required to inhibit bacterial

growth

35
Q

Are higher or lower MIC values better for treatment?

A

Lower

36
Q

What is a Susceptibility break point?

A

A drug concentration above which an organism is

considered resistant and at or below this value organism is susceptible to that drug.

37
Q

What are the three break point values are set at?

A

Susceptible, Intermediate, or Resistant

38
Q

Briefly discuss how the Kirby Bauer test works.

A

Agar is cultivated with bacteria, small paper disks with antibiotic contained is placed on the agar, incubate, measure zone of inhibition

39
Q

What is MBC?

A

The minimal concentration of a drug that kills the bacteria.

40
Q

What is the Gradient Diffusion Test?

A

Uses diffusion and dilution

41
Q

What are the possible results of susceptibility?

A

Susceptible- High likelihood of therapeutic success
Intermediate- Uncertain therapeutic outcome
Resistant- High likelihood of therapeutic failure

42
Q

When does Antibiotic Resistance happen?

A

When bacteria change and become resistant to the antibiotic used to treat the infections they cause

43
Q

What are 2 types of antimicrobial resistance?

A

Innate resistance, Acquired resistance

44
Q

What type of resistance has preexisting genomic properties?

A

Innate resistance

45
Q

What type of resistance is acquired by mutation or horizontal gene transfer?

A

Acquired resistance

46
Q

How do you prevent infectious diseases?

A

Vaccines, management, hygiene practices