L7 - introduction to antibiotics and resistance Flashcards
There are 8 factors you need to take into consideration when choosing an antibiotic, name 3.
Active - is it active against the target organism?
Site of infection - Will it reach the site of infection (e.g. cross the BBB?)
Formulation Is it available in the right formulation? (oral/IV)
Consider cross-interactions with other medication
Toxicity to other organs/tissues
Monitoring - Does the drug require close monitoring?
Allergies
Dosing
What is meant by an organism being ‘suceptible’ to an antibiotic?
Growth of the organism is inhibited at a reasonable concentration
Give a method of testing microbial susceptibility
Broth microdilution - Containers with doubling concentrations of antibiotic First one to have no growth is the minimum inhibitory concentration/
Disc senstivity testing - Each disc in a petri dish contains a different antibiotic, one that gives the biggest zonar clearance is the most effective
Antibacterials work in one of four major ways - inhibition of cell wall synthesis inhibition of protein synthesis inhibition of cell membrane function inhibition of nucleic acid synthesis Which category do the following fall into? beta-lactams aminoglycosides quinolones polymixins
beta - lactams - inhibition of cell wall synthesis (also glycopeptides)
Aminoglycosides - inhibition of protein synthesis (also tetracyclines and macrolides)
Cell membrane function inhibition - polymixins
Nucleic acid synthesis inhibition - quinolons (also trimethoprim and rifampicin)
How do beta-lactams work?
Bind penicillin binding protein and thus prevent cross-linking of the cell wall in the bacteria thus making it weaker.
Give one gram +ve and one gram -ve bacteria that beta-lactams (penicillins) are effective against
Gram +ve - Streptococcus pyogenes/streptococcus pneumoniae
Gram -ve - Nisseria meningitidis
How do bacteria transfer resistance?
Interaction of pili alllows the transfer of plasmids containing the resistance genes
Ceftriaxone is a cephalosporin which is a beta lactam, T/F?
T
Ceftriaxone has good activity in the CSF, what complication is commonly caused by it though and why is this?
Diarrhoea - because gut flora is wiped out allowing accumulation of C. difficile
What is the most common glycopeptide and give a common use?
Vancomycin - C. dif/MRSA
Doxycycline is often alternative to penicillin in penicillin resistance. What however is it commonly used for first line? Why shouldn’t this be given to young children?
Chlamydia/community acquired pneumonia
Because it stains developing teeth
When is gentamicin (an aminoglycoside) used?
Severe gram -ve sepsis
What is the main use of trimethoprim?
UTI’s (also useful against MRSA, however Vancomycin is first line)
What is used for topical treatment of thrush?
Nystatin
When would we use aciclovir and when would we use tamiflu?
aciclovir - Herpes/chicken pox/shingles
Tamiflu - influenza A and B
