Antimicrobial chemotherapy (better cue cards

Question 1

Define ‘bactericidal’

Answer 1

An antimicrobial that kills bacteria (eg the penicillins)

Question 2

Define bacteriostatic

Answer 2

An antimicrobial that inhibits growth of bacteria (eg. erythromycin)

Question 3

Define ‘sensitive’

Answer 3

An organism is considered sensitive if it inhibited or killed by levels of the antimicrobial that are available at the site of infection

Question 4

Define ‘resistant’

Answer 4

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

Question 5

Define ‘MIC’

Answer 5

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

Question 6

Define ‘MBC’

Answer 6

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

Question 7

What are the 3 routes of administration

Answer 7

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

Question 8

What are the 3 mechanisms of action of antimicrobial agents

Answer 8

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

Question 9

what two types of drugs are β-lactams

Answer 9

Penicillins and cephalosporins
β-lactam antibiotics disrupt peptidoglycan synthesis
by inhibiting the enzymes which are responsible for cross-linking the carbohydrate chains.
(Peptidoglycan is an important structural component of the bacterial cell wall and the enzymes
involved in its synthesis_

Question 10

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

Answer 10

Glycopeptides and β-lactams

Question 11

What are two common glycopeptides

Answer 11

Vancomycin and teicoplanin

Question 12

Describe the mechanism and range of action of glycopeptides

Answer 12

They inhibit cell wall synthesis - but at a prior stage than B-lactams
they act only on gram positive organisms

Question 13

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

Answer 13

Parenterally

Question 14

What is one side effect of vancomycin

Answer 14

It is toxic

Question 15

What are the 4 types of antimicrobial which inhibit protein syntehsis

Answer 15

• Aminoglycosides
• Macrolides and tetracyclines
• Oxazolidinones
• Cyclic lipopeptides

Question 16

What type of bacteria are aninoglycosides useful for?

Answer 16

Serious gram negative Infection

Question 17

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

Answer 17

It is an Aminoglycoside and is toxic - requiring a careful dosing regime and motoring of levels

Question 18

What are the uses of macrolides and tatracyclines

Answer 18

Useful in treatment of gram positive infections in patients who are penicillin allergic - however CANNOT BE USED WITHOUT LABORATORY TESTING

Question 19

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

Answer 19

It is an oxazolidonones (protein synthesis inhibitor). It has good activity against MRSA - Typically held in reserve for the treatment of serious infection

Question 20

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

Answer 20

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

Question 21

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

Answer 21

• Trimethoprim and sulphamethoxazole
• Fluoroquinolone’s

Question 22

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

Answer 22

Ciprofloxacin is a fluoroquinolone (nucleic acid inhibitor). commonly used against gram negative organisms. Can be taken orally
Not to be used in children

Question 23

Describe inherent or intrinsic resistance

Answer 23

In some cases all strains of a given species are naturally resistant to an antibiotic. This is usually due to inability of drug to penetrate the bacterial cell wall to exert its action

Question 24

What are the 2 ways in which acquired resistance may be acquired?

Answer 24

1. A spontaneous mutation during multiplication or bacterial DNA can result in a change in structure or function which no longer allows the antibiotic to act as its target may have changed
2. The gene or genes that code for resistance can spread from organism to organism or indeed from species to species. This is by far the most common mode of the spread of resistance and genes can be carried on by plasmids (extra chromosomal packages for DNA) or on transposons (packets of DNA which insert themselves into the chromosome

Question 25

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

Answer 25

β-lactamase production - β-lactamases are bacterial enzymes which cleave the β–lactam ring of the antibiotic and thus render it inactive Alteration of penicillin binding protein (PBP) target site - Mutations in PBP genes result in a modified target site to which β–lactams will no longer bind

Question 26

What drug is β-lactamase resistant

Answer 26

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

Question 27

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

Answer 27

Extended spectrum β–lactamases (ESBLs) are an increasing problem in hospitals and are produced by some Gram negative organisms. These β–lactamases can break down third generation cephalosporins as well as penicillins and therefore render the organism resistant to all β–lactam antibiotics

Question 28

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

Answer 28

Vancomycin resistant enterococci (VREs) have appeared recently. The major concern among microbiologists is that this mechanism of resistance might spread from enterococci to Staph aureus, producing vancomycin resistant Staph aureus. Staph aureus is a more significant pathogen than enterococci and this prospect is viewed with alarm

Question 29

Describe the spectrum of Benzyl penicillin (penicillin G)

Answer 29

Best choice for intra-venous treatment of serious pneumococcal, meningococcal and step pyogens

Question 30

Describe the spectrum of amoxicillin/ampicillin

Answer 30

Effective against streptococci and coliforms

Question 31

Describe the spectrum of co-amoxiclov

Answer 31

Effective against B-lactamase producing coliforms

Question 32

Describe the spectrum of flucloxacillin

Answer 32

Effective against staph infections

Question 33

Describe the spectrum of peperacillin

Answer 33

Effective against Enterococcus faecalis and pseudomonas species

Question 34

Describe the spectrum of cephalosporins

Answer 34

Activity against Gram -'ve organisms increases from 1st through 3rd generation Activity against Gram +'ve organisms decreases from 1st through 3rd generation Generally not used as much anymore as they seem to encourage Ciff D infections

Question 35

How must cephalosporins be taken?

Answer 35

Parenteral use only

Question 36

Describe the specrum of aminoglycocides

Answer 36

Noted for action against Gram -'ve organisms Effective against staphlococci but not streptococci Gentamicin cheapest and most common aminoglycocide

Question 37

Describe the spectrum of glycopeptides

Answer 37

Only gram +'ve organisms are affected (anaerobic +aerobic) Vancomycin most common example

Question 38

Describe the spectrum of action of macrolides

Answer 38

Mainly used against gram +'ve organisms - Used as an alternative to penicillin for patients with a penicillin allergy

Question 39

Describe the spectrum of action of Quinolones

Answer 39

Nearly all gram -'ve organisms are sensitive Mainly used in treatment of community acquired pneumonia

Question 40

Describe the spectrum of action of metronidazole

Answer 40

Effective against Gram +'ve and -'ve anaerobes

Question 41

Describe the spectrum of action of fusidic acid

Answer 41

Only used as staphylococcal drug

Question 42

Describe the spectrum of action of trimethoprim

Answer 42

Used in urinary infections

Question 43

Describe the spectrum of action of tetracyclines

Answer 43

Used in genital tract and urinary tract infections

Question 44

Describe the spectrum of action of clindamycin

Answer 44

Effective against Gram +'ve organisms

Question 45

What infection is linezolid used against

Answer 45

MRSA

Question 46

What infection is fidoxmicin used against

Answer 46

C. diff

Question 47

What infection is daptomycin used against?

Answer 47

MRSA

Question 48

What are the 4 classes of anti-fungal drugs?

Answer 48

Polyenes Echinocandins Allymines Azoles

Question 49

Describe the mechanism of polyenes

Answer 49

They bind to the ergosterol which is present in the fungal cell wall but not in the bacterial cell wall resulting increased permeability of the cell wall. HOWEVER this also binds to mammalian sterols making polyenes TOXIC

Question 50

Describe the use of amphotericin B and Nystatin (Hint: they are Polyenes)

Answer 50

Amphotericin B is used intra-venously for serious yeast infections and other fungal infections. Very toxic. Nystatin is used topically or in oral suspension and is not an intra-venous agent for serious fungal infection

Question 51

Describe the mechanism of Azoles

Answer 51

Inhibit ergesterol synthesis

Question 52

What is fluconazole used to treat?

Answer 52

Yeast infections

Question 53

What are voriconazole and intraconazole used to treat?

Answer 53

Aspergillosis

Question 54

Describe the mechanism of allylamines

Answer 54

They suppress the ergosterol synthesis but act at a different stage of the synthetic pathway from azoles

Question 55

Describe the use of Terbinafine

Answer 55

Used for fungal infections of the skin and nails

Question 56

Describe the mechanism of echinocandinds

Answer 56

They inhibit the synthesis of glucan polysaccharide in several types of fungi

Question 57

What are echinocandins used for?

Answer 57

Serious candida and aspergillus infections

Question 58

Describe anti-herpes virus drugs

Answer 58

All become latent and include: Herpes simplex virus (HSV), eptein-barr virus (HBV), cytomegalovirus (CMV) and Varicella-Zoster Virus (VZV).

Question 59

Describe the mechanism and function of Aciclovir

Answer 59

Nucleotide anologue. Converted inot active form by an enzyme. It is specific for virus - infected cells meaning it is not very toxic Extremely active againstHSV and active against VZV IV used for serious, Oral for less serious

Question 60

Describe the use of valaciclovir and famciclovir

Answer 60

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

Question 61

Describe the use of valganciclovir

Answer 61

Pro drug of ganciclovir -> alternative treatment for CMV. High levels of bone marrow toxicity

Question 62

Describe the use of foscarnet

Answer 62

Used for HSV, VSV and CMV Highly nephrotoxic

Question 63

Describe the use of Cidofovir

Answer 63

Used for CMV retinitis