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Veterinary Bacteriology and Mycology > Antibacterial Agents > Flashcards

Antibacterial Agents Flashcards

(49 cards)

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1
Q

define antibiotic

A

a substance produced by one type of microorganism, which then can be used to inhibit another microorganism

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2
Q

define antimicrobial

A

substance that kills or inhibits the growth of microbes

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3
Q

define anti-infective

A

medicines that work to prevent or treat infections

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4
Q

define selective toxicity

A

the ability of an antimicrobial agent to kill or harm the microorganism cells without harming the cells of the host

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5
Q

define MIC

A

minimum inhibitory concentrations; the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation; needed to prevent visible bacterial growth

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6
Q

define MBC

A

minimum bacteriocidal concentration; the minimum concentration of a drug which kills 99.9% of the test microorganism in the original inoculum; needed to kill the bacteria

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7
Q

define bacteriostatic

A

a biological or chemical agent that stops bacteria from reproducing

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8
Q

define bacteriocidal

A

a biological or chemical agent used for killing bacteria

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9
Q

what are the two components of anti-infectives

A
  1. antimicrobials
    - antibacterials
    - antifungals
    - antivirals
  2. antiparasitics
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10
Q

what is the difference between microbistatic and microbicidal

A

static: prevents growth

cidal: kills

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11
Q

the antimicrobial drug must match the _______ and the therapy can be ___________ or ____________

A

bug, empiric, targeted

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12
Q

what is empiric therapy

A

lab results not yet done, clinician suspects a bacterial infection, broad-spectrum antibiotic therapy given initially to the patient

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13
Q

what is targeted therapy

A

known as ā€˜C & Sā€™; a therapy is given based on a bacterial culture and antibiotic susceptibility test

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14
Q

in general, if a bug is not resistant to a drug, then as the concentration of the drug decreases, the growth of the bug _______________

A

increases

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15
Q

how was penicillin discovered

A

antibiotic secreted by the fungus Penicillium notatum inhibited the growth of S. aureus

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16
Q

how are antibiotics used clinically for human and animal companion

A
  • therapeutic
  • occasionally prophylactic
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17
Q

what are the clinical uses of antibiotics for production animals

A
  • therapeutic
  • metaphylactic
  • prophylactic
  • virtually eliminated for growth promotion
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18
Q

what are the different mechanisms of action of antimicrobial drugs

A
  • cell wall synthesis
  • antimetabolites
  • DNA replication
  • RNA synthesis
  • Protein synthesis (either 30S or 50S)
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19
Q

what are examples of antimicrobials that utilize cell wall synthesis as their mechanism of action

A

penicillin and penicillin-like drugs
- beta-lactams
- glycopeptides

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20
Q

what are examples of antimicrobials that utilize protein synthesis (30S or 50S ribosome) as their mechanism of action

Study These Flashcards
A
  • aminoglycosides, tetracycliines (30S)
  • chloramphenicol macrolides (50S)
21
Q

what are examples of antimicrobials that utilize RNA synthesis as their mechanism of action

Study These Flashcards
A

rifampin or rifabutin

22
Q

what are examples of antimicrobials that utilize inhibition of nucleic acid synthesis as their mechanism of action

Study These Flashcards
A
  • sulphonamides and trimethoprim (folic acid metabolism)
  • quinolones (inhibit DNA supercoiling)
  • imidazoles
23
Q

what are examples of antimicrobials that utilize inhibition of membrane function as their mechanism of action

Study These Flashcards
A

polymixins (polypeptides)

24
Q

what is the difference between a prokaryotic and eukaryotic ribosome

Study These Flashcards
A

prokaryotic: 50S and 30S

eukaryotic: 60S and 40S

25
how does chloramphenicol prevent protein synthesis
binds to 50S protein and inhibits formation of peptide bond
26
how does erythromycin inhibit protein synthesis
binds to 50S portion, prevents translocation-movement of ribosome along mRNA
27
how do tetracyclines inhibit protein synthesis
interfere with attachment of tRNA to mRNA-ribosome complex
28
how does streptomycin inhibit protein synthesis
changes the shape of the 30S portion, causes code on mRNA to be read incorrectly
29
how do bacteria get their folic acid
synthesize their own, cannot get it from the environment
30
how do sulfonamides work to inhibit nucleic acid synthesis
compete with PABA (p-aminobenzoic-acid) at the first step of folic acid synthesis
31
what is the normal pathways for the formation of metabolites/AA precursors, and how do antimetabolites interfere
PABA -> dihydrofolic acid --> tetrahydrofolic acid -> precursors of DNA, RNA, proteins Sulfa drugs interfere with the formation of dihydrofolic acid and tetrahydrofolic acid
32
what are 3 examples of antimycobacterials
- isoniazid - rifampin - ethambutol
33
what does isoniazid do and how is it used
- inhibits synthesis of mycolic acids - primarily used in treatment or prophylaxis of TB
34
what does rifampin do and how is it used
- inhibits bacterial RNA polymerase - used to treat TB, also prophylaxis for some gram neg and gram pos bacterial infections - oral contraceptive efficacy may be lessened
35
what does ethambutol do and how is it used
- inhibits incorporation of mycolic acid into cell wall - relatively weak drug; only used in conjunction with antimycobacterials
36
how are antibacterials classified according to spectrum of activity
can be classified as broad-spectrum, intermediate spectrum, or narrow-spectrum depending on the range of bacterial species susceptible to these agents
37
describe broad spectrum antibacterials and give examples
active against both Gram-positive and Gram-negative organisms. Examples include: tetracyclines, phenicols, fluoroquinolones, 'third-generation' and 'fourth-generation' cephalosporins
38
what are narrow spectrum antibacterials
have limited activity and are primarily only useful against particular species of microorganisms
39
glycopeptides and bacitracin are only effective against what type of bacteria
gram +
40
polymixins are usually only effective against what type of bacteria
gram -
41
aminoglycosides and sulfonamides are only effective against what type of organism
aerobic organisms
42
nitroimidazoles are generally only effective for what organisms
anaerobes
43
antimicrobial resistance is due to alteration is the ______ or the ______________
drug or the drug target
44
what are the mechanisms of drug resistance
- genetic alteration of the drug's target site - spontaneous mutations in DNA and DNA transfer of drug resistance - decreased accumulation due to decreased influx of the drug and increased efflux of the drug - destruction of the drug enzymatically by beta-lactamase, acetyltransferase, or esterase
45
what is cross-resistance
resistance to a particular antibiotic that often results in resistance to other antibiotics, usually from a similar chemical class, to which the bacteria may not have been exposed
46
give two examples of drugs with which cross-resistance can occur
1. colistin and polymixin B 2. Penicillin and cephalexin
47
pathogens that are resistant to multiple antibiotics are considered to be what
multidrug resistant (MDR)
48
what are the 3 genetic basis's for drug resistance
- chromosomally-mediated resistance: mutant selection - plasmid-mediated resistance: spread of resistance plasmid - plasmid-mediated resistance on a transposon: spread of resistance gene
49
What is the disk diffusion test kit
equipment that is used in the lab to determine the susceptibility of clinical isolates of bacteria to different antibiotics

Veterinary Bacteriology and Mycology (8 decks)

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