Antimicrobial Agents Flashcards

1
Q

define antibiotic.

A

products of microbes that, in dilute solution, inhibit or kill other organisms

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2
Q

describe antimicrobial agents

A

man made agents which include antibiotics and synthetic compounds that have the same effect - to inhibit or kill other organisms

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3
Q

what is the difference between agents being static or cidal

A

static - inhibits microbes
cidal - kills microbes

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4
Q

why may you use a static antimicrobial agent rather than cidal?

A

gives time for the immune system to eliminate the bacteria
- in case cidal can be more harmful

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5
Q

what test can you use to test the susceptibility of bacteria to drugs? describe it.

A

disc diffusion test
- grow bacteria on agar plate
- place antimicrobial onto them
- incubate
- observe the zones of clearing around the disc where bacteria has been killed

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6
Q

what is the MIC?

A

minimum inhibitory concentration

the lowest conc of antibiotic that prevents visible growth

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7
Q

what is the MBC?

A

minimum bactericidal concentration

the lowest concentration of antibiotic that kills particular bacterium

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8
Q

what is an accurate way of determining the MIC and MBC of a bacteriostatic drug?

A

using test tubes
- control with only bacteria
- control with only antibiotics
- test tubes with varying concentrations of antibiotics

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9
Q

state the concentration levels of test tubes if the concentration halves every time.

A

1
1/2
1/4
1/8
1/16
1/32
1/64
1/128

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10
Q

give an example of a bacteriostatic drug

A

erythromycin

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11
Q

give an example of a bactericidal drug

A

penicillin

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12
Q

why is selective toxicity important?

A

to not affect the human host, but just the bacteria

but acting upon bacterial reactions not found in human cells

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13
Q

how can you have problems with selective toxicity? give an example.

A

can develop allergies

penicillin allergy comes from presence of thiazolidine ring in penicillin

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14
Q

why can antiviral, antifungal and anti protist drugs be more toxic to humans?

A

closer cell structure to human cells
- can cause damage

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15
Q

how do antiviral drugs work?

A

inhibit transcription factors

ribozymes
- RNA molecules
- tertiary structure confers enzymatic activity

antisense RNA
- short sequence of RNA, complement of mRNA
- binds to specific mRNA
- prevents translation

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16
Q

give 10 examples of antiviral drugs.

AGARONZZLR

A

Acyclovir
- treat herpes
Gancyclovir
- treat cytomegalovirus

Amantadine and Rimantadine
- treatment and prevention of influenza A
- target viral entry and uncoating

Oseltamavir (Tamiflu) and Zanamivir (Relenza)
- inhibit neuraminidases
- prevent release of influenza virus from infected cells
Nelfinavir
- inhibits proteases

Zidovudine (AZT)
- inhibits reverse transcriptase
- slows down HIV when patient has developed AIDS
Lamivudine
- inhibits reverse transcripta

Ribavirin
- treat respiratory syncytial virus

17
Q

heavy use of which drug during the influenza pandemic lead to resistant strains of this virus?

A

Oseltamivir

18
Q

give 5 examples of antifungal agents.

NITTA - nitty having mushroom drugs

A

Nystatin
- a polyene
- treat oral and genital candida infection

Imidazoles and Triazoles
- the Azoles family
- inhibit ergosterol synthesis
= membrane leakage
- imidazole = too toxic for systemic infection but used topically
- triazoles - moulds and yeasts

Terbinafine
- treat skin and nail infections
- inhibits ergosterol biosynthesis

Amphotericin B
- treat systemic mycoses
- potentially toxic to humans

19
Q

what drug is part of the Triazoles which some yeast species are devloping resistance against? give a fungi which IS resistant to it.

A

fluconazole

candida krusei

20
Q

what is Amphotericin B (antifungal drug) also given with, to reduce the potential toxicity to humans?

A

5-flucytosine (5-FC)

21
Q

describe 5-FC

A

5-Flucytosine
- synthetic pyrimidine
- metabolised in fungi to 5-flurouracil
- active against pathogenic yeasts

  • how it works
  • interfere with nucleic acid synthesis
22
Q

describe a polyene?

A

bind with sterols in fungal eukaryotic membranes = destabilisation

23
Q

what are protists?

A

unicellular eukaryotes

24
Q

give examples of antiprotist drugs. (4) queens, pyramid and M

A
  1. chloroquine
  2. mefloquine
  3. pryimethamine
  4. metronidazole
25
what is metronidazole and how does it work? what does it treat?
an antiprotist agent - induces strand breaks in DNA - disrupts membrane integrity treats anaerobic bacteria - Trichomonas vaginalis - Entamoeba histolytica
26
what antibacterial antibiotics target in bacteria? (6)
1. cell wall 2. membrane integrity 3. protein synthesis 4. DNA metabolism 5. DNA packaging 6. RNA polymerase
27
with antibacterial antibiotics, how do cell wall inhibitors work? give 4 antibacterial antibiotics that interfere with cell wall. which is a antibiotic that interferes with the cell wall but is also toxic to humans?
- bacterial cell wall has peptidoglycan - with L and D amino acids = targets for selective toxicity antibiotics: - cycloserine - fosfomycin - glycopeptides - b-lactams - has a b-lactam ring toxic antibiotic = bacitracin
28
what was the first antibiotic in clinical practise?
benzyl penicillin
29
give 3 types of b-lactam antibacterial antibiotics.
cephalosporins monobactams - mainly against gram-negative bacteria carbapenems
30
give 3 antibacterial antibiotics that affect membrane integrity.
polymyxins - against gram negative metronidazole - anaerobic bacterial infections gramicidins - topically, against gram positive bacteria
31
what antibacterial antibiotics affect DNA metabolism?
para-aminobenzoic acid sulphamethoxazole trimethoprim folic acid
32
what antibacterial antibiotics affect DNA?
nalidixic acid metronidazole ciprofloxacin moxifloxacin levofloxacin
33
what antibacterial antibiotics affect protein synthesis?
ahminoglycosides tetracyclines chloramphenicol macrolides fusidic acid lincosamides mupirocin linezoid