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Year 1- Principles of Disease (FOM) > Antimicrobial Chemotherapy > Flashcards

Antimicrobial Chemotherapy Flashcards

1
Q

What is meant if an organism is termed sensitive?

A

organism is sensitive if it is inhibited or killed by the antimicrobial

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2
Q

What is meant if an organism is termed resistat?

A

organism is resistant if it is not killed or inhibited by the antimicrobial available at the site of infection.

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3
Q

What are antibiotics active against?

A

Bacteria

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4
Q

What is meant by a Bactericidal?

A

antimicrobial that kills bacteria.

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5
Q

What is mean by a Bacteriostatic?

A

Antimicrobial that inhibits growth of bacteria.

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6
Q

what is meant by MIC?

A

Minimal inhibitory concentration minimum concentration of antimicrobial needed to inhibit growth of a given

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7
Q

How can antiobiotics be administrated?

A

Topical
Systemic
Parenteral

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8
Q

How is an antibiotic administered topically?

A

Applied to a surface (skin or to mucous membranes )

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9
Q

How is an antibiotic administrated systematically?

A

Taken internally, (orally or parenterally)

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10
Q

Hpw is an antibiotic administered Parenterally?

A

Administered intra-venously (i.v.) or intra-muscularly (i.m.), occasionally subcutaneously.

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11
Q

What do antibiotics do to bacteria?

A

By inhibiting or killing bacteria.

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12
Q

Name the three areas of metabolic activity of antibiotics.

A

Inhibition of cell wall synthesis
Inhibition of protein synthesis
Inhibition of nucleic acid aynthesis.

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13
Q

Why are human cells not affacted by antibiotics?

A

Human cells do not have cell walls, so they are not affected by antibiotics that inhibit cell wall synthesis

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14
Q

Name two Bactericidal antibiotics which are effective against gram positive bacteria.

A

Penicillins and Cephalosporins (β-lactams).

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15
Q

Macrolides are considered either bactericidal orbacteriostatic antibiotics. depending on what?

A

Depending on concentration and bacterial species,

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16
Q

Oxazolidinones are considered either bactericidal orbacteriostatic antibiotics. depending on what?

A

Depedning on the bacteria being treated.

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17
Q

Measurement of the antibiotic sensitivity of an organism in the laboratory is designed to do what?

A

Predict whether an infection will respond to treatment with that antibiotic.

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18
Q

In some cases, all strains of a given species are naturally resistant to an antibiotic.

What are streptococci always resitant to?

A

aminoglycosides

19
Q

Gram negative organims are always resistant to??

Why?

A

Vancomycin

Usually due to inability of the drug
to penetrate the bacterial cell wall to exert its action)

20
Q

If a bacertia is known to be resitant, what becomes irrelevant.

A

Laboratory Sensitivity Testing

21
Q

What is aquired resistance?

A

Resistance may be present in some strains of bacteria but not in others.

22
Q

Laboratory sensitivity testing is ued to?

A

Esablish the sensitivity of any bacteria isolate from a patient

23
Q

What does the widespread use of antibiotics encourage and cause?

A

causes selective pressure and encourages new resistant organisms to outgrow sensitive strains.

24
Q

How is resistance aquired?

A

Spontaneous mutation
Spread of resistance.

25
Q

Describe how spontaneous mutaion relate to resistance.

A

Change in structure or function which no longer allows the antibiotic to act
(target may have changed).

26
Q

How is spread of resistance related to resistance?

A

the gene/s that code for resistance can spread from organism to organism or from species to species.

27
Q

How can genes be carried?

A

Genes can be carried on plasmids (extra chromosomal packages of DNA)
or on transposons (packets of DNA which insert themselves into the chromosome).

28
Q

How can new genes be aquired?

A

Horizontal gene transfer

29
Q

What happens in conjuguation relating to bacteria?

A

DNA transfer bacteria cells.

30
Q

What happens in trandsuction relating to bacteria?

A

Bacterial DNA transferred by viruses.

31
Q

What happens in transformation relating to bacteria?

A

naked DNA upttake by bacteria.

32
Q

What are some issues with antibiotic resistance?

A

For virtually every antibiotic or antibiotic class,
micro-organisms have evolved a resistance mechanism.

β-lactamase production.

33
Q

How does β-lactamase production cause issues with antibiotic resistance?

A

β−lactamases are bacterial enzymes which cleave the
β–lactam ring of the antibiotic and thus render it inactive.

β-lactamases are also common in Gram-negative bacilli.

34
Q

How can we combat β-lactamase?

A

1:

To modify the antibiotic side chain producing
new antibiotic resistant to the actions of β-lactamase.
-> for example, co-amoxiclav:
amoxicillin plus the β-lactamase inhibitor clavulanic acid.

To introduce a second component to the antibiotic
(β-lactamase inhibitor) protecting the antibiotic from enzymatic degradation.
-> for example, Flucloxacillin:
(antistaphylococcal) which is a modified form of penicillin.

35
Q

What are ESBLs?

A

enzymes that mediate resistance to extended-spectrum
(third generation) cephalosporins.

36
Q

What is Antibiotic resistance transferred by?

A

Conjugation (plasmids0.

37
Q

Name some gram positive cocci.

A

Streptococcus
Pneumococcus
Enterococcus

38
Q

Name some gram negative cocci

A

Neisseria
Morasella

39
Q

Name a gram positive bacilli.

A

Corynebacterium
Clostridium

40
Q

Name some gram negative bacilli.

A

Escherichia coli
Shingella
Salmonella

41
Q

Name some gram negative spirals.

A

Vibrio cholerae
Helicobacter pylori

42
Q

What antibiotic are most gram negative organisms resistant to?

A

Benzyl penicillin

43
Q

How can you disrupt peptidoglycan synthesis

A

Inhibiting the enzymes (penicillin-binding proteins, PBPs) responsible for cross-linking the carbohydrate chains.

44
Q

Most hospital strains of which kind of bacteria produce β-lactamase?

A

Staphylococcus aureus

Year 1- Principles of Disease (FOM) (40 decks)

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