Antibiotics symposium 1: principles of antibiotics

Question 1

what is an antibiotic?

Answer 1

an agent produced by microorganisms that kill or inhibit the growth of other microorganisms

Question 2

What is the definition of a target site of an antibiotic?

Answer 2

points of biochemical reaction crucial to the survival of the bacterium

Question 3

which gram staining of bacteria has more peptidoglycan?

Answer 3

G+

Question 4

what is the name of the protein that penicillin works on?

Answer 4

penicillin binding protein

Question 5

what drug classes come under beta lactams?

Answer 5

penicillins, cephalosporins and carbapenems

Question 6

Which class is also active against penicillin binding proteins but is not a beta lactams?

Answer 6

glycopeptides

Question 7

which antibiotics interfere with nucleic acid synthesis and function?

Answer 7

metronidazole

rifampicin

Question 8

what type of bacteria can metronidazole kill?

Answer 8

anaerobes

Question 9

which class of antibiotics works on inhibiting DNA gyrase?

Answer 9

fluoroquinilones

Question 10

which antibiotic classes work on inhibition of ribosomal activity?

Answer 10

aminoglycosides
tetracyclines
lincosamides 
macrolides 
chloramphenicol

Question 11

which drug classes inhibit folate synthesis?

Answer 11

sulphonamides

trimethoprim

Question 12

what does bacteriostatic mean?

Answer 12

inhibitory to growth

Question 13

in what ways can antibiotics inhibit growth?

Answer 13

inhibit protein synthesis
inhibit DNA replication
interfere with metabolism

Question 14

in what additional way do bacteriostatic antibiotics work?

Answer 14

they reduce production of toxins

Question 15

what is the main mechanism of bactericidal antibiotics?

Answer 15

inhibition of cell wall synthesis

Question 16

when are bactericidal drugs particularly useful?

Answer 16

when there is poor tissue penetration by blood vessels
difficult to treat infections
need to eradicate infection quickly

Question 17

what are the two major determinants of antibacterial effects?

Answer 17

concentration

time

Question 18

which drugs have concentration dependent killing?

Answer 18

aminoglycosides

quinolones

Question 19

which drugs have time dependent killing?

Answer 19

beta lactams
clindamycin
macrolides
oxazolidinones

Question 20

which type of bacteria is flucloxacillin mainly for?

Answer 20

staphylococcus

Question 21

which antibiotic is used for MRSA?

Answer 21

vancomycin

Question 22

how does the half life/ elimination of the drug affect treatment?

Answer 22

affects the dosage intervals and duration of treatment

Question 23

what are the pt considerations before prescribing antibiotics?

Answer 23

allergy or intolerance 
side effects
age 
liver and kidney function
pregnancy/breastfeeding 
drug interactions 
C. diff

Question 24

what are the 4 key ways that antibiotics confer resistance?

Answer 24

change the antibiotic target
destroy the antibiotic
prevent antibiotic access
remove antibiotic from bacteria

Question 25

describe how bacteria can change the antibiotic target

Answer 25

mutation in the gene for a protein to which the antibiotic binds causes the antibiotic to be unable to bind, or a gene mutates so that it produces a protein that binds to and blocks the antibiotic binding site

Question 26

give examples of antibiotics that are not sensitive due to change in antibiotic target

Answer 26

flucloxacillin no longer able to bind PBP of staph (MRSA) wall components change in enterococci so reduce vancomycin binding rifampicin activity reduced by RNA polymerase in myco. TB

Question 27

how do bacteria destroy an antibiotic

Answer 27

bacterial enzyme produced

Question 28

give examples of bacteria that can destroy antibiotics

Answer 28

- beta lactamases hydrolyse beta lactam ring of penicillins and cephalosporins - staphylococci produce penicillinase so penicillin but not but not flucloxacillin is inactivated - G- bacteria phosphorylate aminoglycosides (gentamycin)

Question 29

How do bacteria prevent antibiotic access?

Answer 29

modify the porin channel size, numbers and selectivity

Question 30

give examples of bacteria that can prevent antibiotic access

Answer 30

pseudomonas aerguinosa against imipenem | G- bacteria against aminoglycosides

Question 31

how do bacteria remove antibiotic?

Answer 31

develop export or efflux proteins

Question 32

Give examples of bacteria that remove antibiotic

Answer 32

S. aureus or S. pneumoniae develop resistanance to fluoroquinolones enterobacteriaceae get resistant to tetracyclins

Question 33

what are the methods of development of bacterial resistance?

Answer 33

intrinsic | acquired - conjugation, transduction, transformation

Question 34

give examples of intrinsic resistance (ie naturally resistant)

Answer 34

aerobic bacteria cant reduce metronidazole to its active form vancomycin cannot penetrate the outer membrane of G- bacteria

Question 35

what is the definition of acquired resistance?

Answer 35

a bacterium that was previously susceptible obtains the ability to resist the activity of a particular antibiotic

Question 36

what is conjugation?

Answer 36

sex pilus forms through which a plasmid is transferred 'bacterial sex'

Question 37

what is transduction?

Answer 37

bacteriophages that have donor bacterial DNA in them infect an bacterium and transfer the DNA to the recipient bacterium

Question 38

what is transformation?

Answer 38

bacteria can take up free DNA from the environment and incorporate it into their genome

Question 39

what are the important resistant G+ organisms?

Answer 39

MRSA | VRE - vancomycin resistant enterococci

Question 40

what does mecA do?

Answer 40

changes the binding site of penicillins as it encodes for a low affinity penicillin binding protein - resistance to all beta lactams

Question 41

which antibiotic class promotes VRE?

Answer 41

cephalosporins

Question 42

by what means do VRE gain their resistance?

Answer 42

aqcuisition of a plasmid - gene prevents vancomycin binding

Question 43

how are gram - bacteria resistant to antibiotics?

Answer 43

they can produce beta-lactamases eg E. col, H. influenzae, N. gonorrhoea, Klebsiella pneumoniae ESBL - more extended beta lactam inhibition ampC beta-lactamase resistance - broad spectrum penicillin, cephalosporin, monobactam resistance, beta lactamase inhibitor resistant with inducible expression

Question 44

what type of antibiotics were developed to combat G- resistance?

Answer 44

carbapenems

Question 45

give examples of carbapenems

Answer 45

ertapenem, imipenem, meropenem, doripenem

Question 46

what is the advantage of carbapenems over other beta lactams?

Answer 46

highly resistant to degradation by beta lactamases or cephalosporinases

Question 47

is there resistance to carbapenems?

Answer 47

Yes - carbapenemases