Flashcards in Microbiology 5 - Antibiotic therapy Deck (80)
What is the difference between bactericidal and bacteriostatic antibiotics?
Bactericidal = kill bacteriaBcteriostatic = inhibit bacterial growth
Why must antibiotics be selectively toxic?
In order to kill the bacteria without damaging the host
How are antibiotics usually administered?
Usually orally or IV (rarely intramuscularly)
When antibiotics are given orally, when will they reach peak serum levels?When given IV?
Approx. 1 hour laterWithin 15 minutes
Where are antibiotics excreted?
Unchanged antibiotic = in the faecesAbsorbed antibiotic = either in the urine or via the liver, binary tract and into the faeces
Why are antibiotics sometimes given in combination? (3)
To cover a broad range of possible infecting organismsTo prevent the development of resistance e.g. in the treatment of TBFor the synergistic effect of the combination (i.e. 1 + 1 = 3) e.g. in the treatment of some cases of endocarditis
What are the 3 main ways in which antibiotics can work?
Acting on bacterial cell wallAffecting the bacterial ribosomeActing on bacterial DNA directly(all of these structures differ in bacteria and mammalian cells)
What are the 3 groups of antibiotics that act on the bacterial cell wall?
The penicillinsThe cephalosporinsThe glycopeptides
Name the 6 penicillins?
PenicillinFlucloxacillinAmoxicillinTemocillinCo-amoxiclavPiperacillin/ tazobactam = Tazocin
Name a cephalosporin?
Name 2 glycopeptides?
How do the penicillins work?
They inhibit cell wall synthesis by preventing the cross-linking of peptidoglycan subunits
Are the penicillins bactericidal or bacteriostatic?
Amount of side effects of penicillins?Narrow or broad spectrum?Excreted by?
Very fewRange from narrow to broad spectrumRapidly via the kidneys
Are the penicillins safe in pregnancy?
What are the 2 main drawbacks of the penicillins?
-some patients are hypersensitive to the penicillins. An allergy to one penicillin means allergy to all penicillins (and sometimes also the cephalosporins)-rapid excretion via the kidney means frequent dosing (usually 4-6 times daily) is necessary
What are the 3 forms of penicillin available? How is each given?
Benzylpenicillin (penicillin G, IV)Phenoxymethyl penicillin (penicillin V, oral)Benzathine penicillin (long actin, IM)
Do organisms that are sensitive to penicillin itself tend to be sensitive to most of the penicillin group of antibiotics?
What does the penicillin nucleus look like?
A house and a garage
What penicillin is given to gram positive organisms? How can this be given?
Flucloxacillin (IV, oral)
What penicillins are given to both gram positive and gram negative organisms? How re these given?
Amoxicillin (IV, oral)Co-amoxiclav (IV, oral)"Tazocin" - IV only (piperacillin/ tazobactam)
What penicillin is given to gram negative organisms?
Temocillin (IV only)
How is flucloxacillin given?
IV and oral
Spectrum of flucloaxicillin?
Very narrow Useful only for staphylococci and streptococci)
What is flucloxacillin used to treat?
Staphylococci and streptococci infections only e.g.Skin and soft tissue infectionWound infectionCellulitis
How can amoxicillin be given?
Why has amoxicillin become less effective over the years?
Many organisms produce beta-lactamse (an enzyme that destroys amoxicillin)
What is co-amoxiclav?When is it used?
Amoxicillin plus clavulanic acid which is a beta-lactadase inhibitor Used when there is an antibiotic resistance to amoxicillin
How can co-amoxiclav be given?
oral and IV