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Clinical Pathology > Intro to Antibacterial Agents > Flashcards

Intro to Antibacterial Agents Flashcards

1
Q

Definition of Antibiotics

A

Chemical products of microbes that kill or inhibit other organisms.

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2
Q

Definition of Antimicrobials agents

A

(usually) synthetic compounds that kill or inhibit organisms - includes, antibiotics, antifungal, antiviral ect…
* *Antimicrobial and Antibiotic are terms used interchangeably

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3
Q

Definition of Bacteriostatic

A

Inhibit bacterial growth (protein synthesis inhibitors)

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4
Q

Definition of Bactericidal

A

Kill Bacteria (Cell wall active agents)

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5
Q

Definition of Minimum Inhibitory Concentration (MIC)

A

The minimum conc of antibiotic at which visible growth is inhibited.

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6
Q

Definition if Synergism

A

Activity of two antimicrobials given together is greater than the sum of their activity if given separately.

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7
Q

Definition of Antagonism

A

One agent that diminishes the activity of another

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8
Q

Definition of Indifference

A

Activity unaffected by the addition of another agent

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9
Q

The combination of which 2 drugs is used in the treatment of streptococcal endocarditis?

A

Synergism of:

  • beta lactam
  • aminoglycoside

*Streptococcal endocarditis is the infection of the endocardial surface of the heart.

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10
Q

Name 5 targets of antibacterial agents

A
  • Cell wall (only present in bacteria not in eukaryotes so ideak for selective toxicity)
  • Protein Synthesis
  • DNA synthesis
  • RNA Synthesis
  • Plasma Membrane
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11
Q

What is the major component of a bacterial cell wall?

A

Peptidoglycan :
- it is present in both Gram positive and Gram negative bacteria
- it is a polymer of glucose derivatives.
(N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG) )

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12
Q

What makes up peptidoglycan?

A

N-acetyl muramic acid (NAM)

N-acetyl glucosamine (NAG)

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13
Q

what drugs inhibit cell wall synthesis?

A
  • beta-Lactams

- Glycopeptides

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14
Q

what type of drug is Benzylpenicillin?

A

beta-lactam antibiotic

*was the first true antibiotic in clinical practice

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15
Q

How do beta-lactam antibiotics work?

A

The are characterised by the beta-lactam ring.

They interfere with the function of “penicillin binding proteins”.

(inhibit with transpeptidase enzymes involved in peptidoglycan cross linking)

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16
Q

Name 4 types of beta-lactam antibiotics

A
  • Penicillins (narrow spectrum)
  • Cephalosporins (broad spectrum)
  • Carbapenems (extremely broad spectrum)
  • Monobactams (gram negative bacteria only)
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17
Q

Give an example of a penicillin

A
  • Benzylpencillin (PEN)
  • Amoxicillin
  • Flucloxacillin

(penicillin is a relatively narrow spectrum beta-lactam antibiotic)

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18
Q

Give an example of a cephalosporin

A
  • Cefuroxime (CXM)
  • ceftazidime

(cephalosporin is a relatively broad spectrum beta-lactam)

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19
Q

give an example of a carbapenem

A
  • Meropenem (MER)
  • Imipenem

(Carbapenem is an extremely broad spec beta-lactam antibiotic)

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20
Q

give an example of a Monobactam

A

-Aztreonam (AZT)

Monobactams are a beta-lactam that are effective only on gram negative bacteria

21
Q

How do glycopeptides work?

A

they are large molecules that inhibit the binding of transpeptidades and therefore prevents peptideoglycan cross-linking

*effective on gram positive bacteria (can’t penetrate gram negative bacteria)

22
Q

give an example of glycopeptides

A
  • Vancomycin

- Teicoplanin

23
Q

describe how protein synthesis takes place in bacteria

A

Translation of RNA takes place on a ribosome.

Ribosome complexes catalyse peptide bond formation and synthesise polypeptides in 4 stages:
-INITIATION (ribosome attaches to mRNA)

  • ELONGATION (amino acids join to form polypeptide chain)
  • TERMINATION (stop codon reached and ribosome releases polypeptide)
  • RIBOSOME RECYCLING (70S ribosome splits into 50S and 30S subunits)
24
Q

Name 4 Protein synthesis inhibitors

A
  • Aminoglycosides
  • Macrolides, Lincosamides, Streptogramins (MLS)
  • Tetracyclines
  • Oxazolidinones
25
Q

Give an example of an aminoglycoside

A
  • Gentamicin

- amikacin

26
Q

how to aminoglycosides inhibit protein synthesis?

A

bind to 30S ribosomal subunit

27
Q

Give an example of a MLS (macrolides, Lincosamides, Steptogramins)

A
  • Erythromycin, clarithromycin (macrolides)

- Clindamycin (lincosamide)

28
Q

How to MLS drugs inhibit protein synthesis?

A
  • Bind to 50S ribosomal subunit

- inhibit protein elongation

29
Q

How do tetracyclines inhibit protein synthesis?

A
  • bind to 30S ribosomal subunit.

- Inhibit RNA translation by interfering with the binding of tRNA to rRNA.

30
Q

Give a example of an Oxazolidinone

A

Linezolid

31
Q

How to Oxazolidinone inhibit protien synthesis?

A

Bind to 50S ribosomal subunit

-inhibits assembly of initiation complex therfore inhibits initiation of protein synthesis

32
Q

How do trimethoprim and sulfonomides work?

A
  • They inhibit DNA synthesis.
  • Inhibit folate synthesis. (folic acid is a purine synthesis precursor)
  • Trimethoprim inhibits Dihydrofolate reductase
  • Sulfonamides inhibit Dihydropteroate synthetase.
33
Q

How do quinolones and fluoroquinolones work?

A

inhibit DNA synthesis :

  • inhibit DNA gyrase
  • inhibit topoisomerase IV

(these enzymes are involved in remodelling DNA during replication ie supercoiling and strand separation)

34
Q

give an example of a Quinolone / fluoroquinolone

A

Ciprofloxacin

35
Q

How does Rifampicin work

A

Rifampicin works as an RNA synthesis inhibitor:

  • inhibits RNA polymerase
  • prevents synthesis of mRNA
36
Q

How does Daptomycin work?

A

Daptomycin is a plasma membrane agent.

only effective on gra positive bac

37
Q

What are the adverse effects specific to aminoglycosides?

A

-Reversibel renal impairment

38
Q

what are the adverse effects specific to beta lactams

A

Allergic reactions

Nausea / rash / anaphylaxis

39
Q

what are the adverse effects of linezolids?

A

Bone marrow depression

40
Q

What beta-lactam drugs are safe to use on a patient with a non-severe penicilin allergy?

A
  • cephalosporins
  • carbapenems

-AZTREONAM is safe to use with ANY penicillin allergy

41
Q

what type of bacteria is Vancomycin used to treat?

A

Gram positive

42
Q

What type of bacteria is Metronidazole used to treat?

A

Anaerobes

43
Q

what type of bacteria is cephalosporins used to treat?

A

Gram negative bacilli

44
Q

what is Flucloxacillin used to treat?

A

Staphylococcus aureus (not MRSA)

45
Q

what is used to treat streptococcus pyogenes?

A

benzylpenicillin

46
Q

what are cephalosporins used to treat?

A

Gram positive and negative bacteria

47
Q

What is metronidazole used to treat?

A

Anaerobes

48
Q

What is vancomycin used to treat?

A

Gram-positive bacteria

MRSA

49
Q

What are the 3 reasons for combination antibiotics therapy?

A
  • To increase efficacy
  • To provide adequately broad spectrum
  • To reduce resistance

Clinical Pathology (9 decks)

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