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Principles of disease > Antimicrobial chemotherapy > Flashcards

Antimicrobial chemotherapy Flashcards

1
Q

Define ‘bactericidal’

A

antimicrobial that kills bacteria (eg penicillins)

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2
Q

Define bacteriostatic

A

antimicrobial that inhibits growth of bacteria (eg. erythromycin)

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3
Q

Define a ‘sensitive’ organism

A

Organism that is inhibited or killed by levels of antimicrobial at site of infection

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4
Q

Define a ‘resistant’

A

An organism is considered resistant if it is not killed or inhibited by levels of the antimicrobial that are available at the site of infection

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5
Q

Define ‘MIC’

A

Minimal inhibitory concentration - The minimum conc. of an antimicrobial needed to inhibit visible growth of a given organism

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6
Q

Define ‘MBC’

A

Minimal bactericidal conc. - The minimum conc. of the antimicrobial needed to kill a given organism

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7
Q

What are the 3 routes of administration

A

Systemic - taken internally, orally or parenterally
Topical - Applied to surface, skin or mucous membranes e.g. conjunctiva
Parenteral - intra-venously (iv), intra-muscularly (im), subcutaneously

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8
Q

What are the 3 mechanisms of action of antimicrobial agents

A

Inhibition of:

cell wall synthesis
protein synthesis
nucleic acid synthesis

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9
Q

What two types of drugs are β-lactams

A

Penicillins and cephalosporins

β-lactam antibiotics disrupt peptidoglycan synthesis by inhibiting enzymes responsible for cross-linking carbohydrate chains

(Peptidoglycan is important structural component of bacterial cell wall and enzymes involved in its synthesis)

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10
Q

What are the two types of antimicrobials which inhibit cell wall synthesis

A

Glycopeptides and β-lactams

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11
Q

What are two common glycopeptides

A

Vancomycin and teicoplanin

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12
Q

Describe the mechanism and range of action of glycopeptides

A

Inhibit cell wall synthesis - at a prior stage than B-lactams
only act on gram positive organisms

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13
Q

What route of administration must glycopeptides take (unless special circumstances)

A

Parenterally

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14
Q

What is one side effect of vancomycin

A

Toxic

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15
Q

What are the 4 types of antimicrobial which inhibit protein syntehsis

A
  • Aminoglycosides
  • Macrolides and tetracyclines
  • Oxazolidinones
  • Cyclic lipopeptides
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16
Q

What type of bacteria are aminoglycosides useful for?

A

Serious gram negative Infection

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17
Q

What type of drug is getamicin and what is a common side effect of adminsitration

A

Aminoglycoside, toxic - requires careful dosing regime and motoring of levels

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18
Q

What are the uses of macrolides and tatracyclines

A

Treatment of gram positive infections in patients with penicillin allergy
Cannot be used without lab testing

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19
Q

What class of drug is linezolid and what is it commonly used for?

A

Oxazolidonones (protein synthesis inhibitor)
Good activity against MRSA
Typically in reserve for treatment of serious infection

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20
Q

What class of drug is daptomycin and what it is commonly used for?

A

Cylic lipopeptide (protein synthesis inhibitor)
Activity against gram positives in general and MRSA in particular

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21
Q

What are the 2 classes of drug which inhibit nucleic acid synthesis

A
  • Trimethoprim and sulphamethoxazole
  • Fluoroquinolone’s
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22
Q

What type of drug is ciprofloxacin?
What it is commonly used for?
What are some drawbacks?

A

Fluoroquinolone (nucleic acid inhibitor)
Against gram negative organisms
Can be taken orally
Not used in children

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23
Q

Describe inherent/intrinsic resistance

A

Some cases all strains of a species are naturally resistant to antibiotic
Inability of drug to penetrate bacterial cell wall to exert its action

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24
Q

What is the first way in which acquired resistance can be acquired in bacteria

A
  1. Spontaneous mutation during multiplication of bacterial DNA can result in change in structure or function which no longer allows antibiotic to act, target may have changed
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25
Q

What is the second way in which acquired resistance may be acquired?

A
  1. resistance genes can spread from organism to organism or species to species
    Most common mode by plasmids (extra chromosomal packages for DNA) or on transposons (packets of DNA which insert themselves into chromosome)
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26
Q

What are the 2 mechanisms of resistance to β–lactam antibiotics?

A

β-lactamase production - bacterial enzymes cleave β–lactam ring of antibiotic and inactive it

Alteration of penicillin binding protein (PBP) target site - Mutations in PBP genes modifies target site and β–lactams will no longer bind

27
Q

What drug is β-lactamase resistant

A

Flucloxacillin - can be used to treat β-lactamase producing staph. aureus

(staph.aureus produce β-lactamase)

28
Q

What are ESBL’s and what are the implications of their existence

A

Extended spectrum β–lactamases (ESBLs) - increasing problem in hospitals

Produced by some Gram negative organisms and can break down third generation cephalosporins and penicillins

Render organism resistant to all β–lactam
antibiotics

29
Q

What glycopeptide resistant bacteria has appeared recently and what are the implications of this mutation?

A

Vancomycin resistant enterococci (VREs)
Mechanism of resistance might spread from enterococci to Staph aureus, producing
vancomycin resistant Staph aureus
Staph aureus more significant pathogen than enterococci

30
Q

Describe the spectrum of Benzyl penicillin (penicillin G)

A

Best choice for IV treatment of serious pneumococcal, meningococcal and strep pyogenes
Gram +ve

31
Q

Describe the spectrum of amoxicillin/ampicillin

A

Streptococci and coliforms
Gram -ve

32
Q

Describe the spectrum of co-amoxiclov

A

Effective against B-lactamase producing coliforms

33
Q

Describe the spectrum of flucloxacillin

A

Effective against staph infections

34
Q

Describe the spectrum of piperacillin

A

Enterococcus faecalis
Pseudomonas species
Extended Gram -ve cover

35
Q

Describe the spectrum of cephalosporins

A

Activity against Gram -‘ve organisms increases from 1st through 3rd generation
Activity against Gram +’ve organisms decreases from 1st through 3rd generation
Not used as much now, may encourage Ciff D infections

36
Q

How must cephalosporins be taken?

A

Parenteral use only

37
Q

Describe the specrum of aminoglycocides

A

Gram -‘ve organisms
Effective against staphlococci but not streptococci
Gentamicin cheapest and most common aminoglycocide

38
Q

Describe the spectrum of glycopeptides

A

Only gram +’ve organisms - anaerobic + aerobic
Vancomycin most common example

39
Q

Describe the spectrum of action of macrolides

A

Mainly against gram +’ve organisms
Alternative to penicillin for patients with penicillin allergy

40
Q

Describe the spectrum of action of Quinolones

A

Active against nearly all gram -‘ve organisms
Mainly used in treatment of community acquired pneumonia

41
Q

Describe the spectrum of action of metronidazole

A

Gram +’ve and -‘ve anaerobes

42
Q

Describe the spectrum of action of fusidic acid

A

Disrupts bacterial protein synthesis
Anti-Staphyloccocal
In combo with flucloxacillin

43
Q

Describe the spectrum of action of trimethoprim

A

Used in urinary infections

44
Q

Describe the spectrum of action of tetracyclines

A

Used in genital tract and urinary tract infections

45
Q

Describe the spectrum of action of clindamycin

A

Gram +’ve organisms

46
Q

What infection is linezolid used against

A

MRSA

47
Q

What infection is fidaxomicin used against

A

C. diff

48
Q

What infection is daptomycin used against?

A

MRSA
Vancomycin Resistant Enterococci

49
Q

What are the 4 classes of anti-fungal drugs?

A

Polyenes
Echinocandins
Allyamines
Azoles

50
Q

Describe the mechanism of polyenes

A

Bind to ergosterol
Present in fungal cell wall but not bacterial
Increases permeability of cell wall
Binds to mammalian sterols making polyenes toxic

51
Q

Describe the use of amphotericin B and Nystatin

A

Amphotericin B - IV for serious yeast infections and other fungal infections
Very toxic

Nystatin - topically or in oral suspension for serious fungal infection
Not intra-venous agent

52
Q

Describe the mechanism of Azoles

A

Inhibit ergesterol synthesis

53
Q

What is fluconazole used to treat?

A

Yeast infections

54
Q

What are voriconazole and intraconazole used to treat?

A

Aspergillosis

(fungal infection caused by aspergillus, affects airways)

55
Q

Describe the mechanism of allylamines

A

Suppress ergosterol synthesis but act at different stage of synthetic pathway from azoles

56
Q

Describe the use of Terbinafine

A

Fungal infections of skin and nails

57
Q

Describe the mechanism of echinocandins

A

Inhibit synthesis of glucan polysaccharide in several types of fungi

58
Q

What are echinocandins used for?

A

Serious candida and aspergillus infections

59
Q

Describe anti-herpes virus drugs

A

All become latent and include:

Herpes simplex virus (HSV)
Epstein-barr virus (EBV)
Cytomegalovirus (CMV)
Varicella-Zoster Virus (VZV).

60
Q

Describe the mechanism and function of Aciclovir

A

Nucleotide analogue
Converted into active form by enzyme
Specific for virus-infected cells
Not very toxic
Extremely active against HSV and VZV
IV used for serious, Oral for less serious

61
Q

Describe the use of valaciclovir and famciclovir

A

Related to aciclovir - Used in oral treatment of HSV and shingles

62
Q

Describe the use of valganciclovir

A

Prodrug of ganciclovir -> alternative treatment for CMV
High levels of bone marrow toxicity

(prodrug is a medication or compound that, after intake, is metabolised into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be used to improve how the drug is absorbed, distributed, metabolised, and excreted)

63
Q

Describe the use of foscarnet (Foscavir)

A

Used for HSV, VZV and CMV
Highly nephrotoxic (toxic to kidneys)

64
Q

Describe the use of Cidofovir

A

Used for CMV retinitis (retinal eye disease)

Principles of disease (47 decks)

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