16 - Anti- infective drugs Flashcards
(46 cards)
why/how are bacterial cells different to human cells
- unique cell wall
- diff cell membrane
- differences in DNA and protein synthesis
differences form the basis for selective toxicity of anti bacterial drugs
which drugs affect cell wall synthesis
- penicllins
- cephalosporins
which drugs affect bacterial cell membrane
- polymyxin B
- propamidine
which drugs affect bacterial protein synthesis
- aminoglycosides
- tetracyclines
- chloramphenicol
- fusidic acid
which drugs affect bacterial DNA synthesis
- fluoroquinolones
which drugs affect bacterial metabolism
- sulphonamides
what are some general considerations of antibiotics
- spectrum of cover
- narrrow vs broad
- single vs combo - penetrations into the appropriate tissue
- superficial - route of administration
- side effects
- tolerability
- pregnancy/lactation
why do we do antibiotic sensitivty testing
- if bacterial infection isnt responding to antibiotic
how is a kirby-bauer A.S test conducted
when the bacteria is isolated
steps of KB antibiotic testing
- take sample of bacteria (biopsy or swab)
- put on agar plate emulsified in saline
- spread on plate
- paper disc impregnanted with antibiotics placed on top of culture
- incubated 37C for 18 hrs
bacteria starting to grow across agar plate
- zone of antibiotic around each plate
anti infectives availible to optoms
- chloramphenicol
- fusidic acid
- propamidine
Chloramphenicol POM
P for acute bacterial conjunctivitis
- bacteriostaic
- broad spectrum (not effective against pseudomanas - can cause severe BK)
-resistence low - good safety profile
formulations available of chloramphenicol
- CPL 0.5% eye drops
- CPL 1% ointment
- CPL minims 0.5%
dose drops - 1 drop every 2 hours for 48 days then every 4 hours or 5 days
what is the mode of action of chloramphenicol
inhibition of bacterial protein synthesis
- CPL binds to peptidyl transferase on the 50s ribosomal subunit
- this prevents the incorporation of new amino acids ot the growing peptide chin
what isolates are associated withh bacterial conjunctivitis
- stapha
- stephe
- haemop
- pseudo
- strep
most common isolates associated with bacterial conjunctivitis ?
staph
least common: strep
Fusidic acid POM - what is it effective against
- gram +ve organisms
particularly staph A
what is fusidic acid lisenced for the treatment of
bacterial conjunctivitis
is fusidic acid an appropriate agent for acute bacterial conjunctivits in children>
why or why not
- ineffective against gram - H influenza
-most common causative pathogen in kids
formulations of fusidic acid
only 1
Fusidic acid 1% modified release eye drops POM
- twice daily
Concentration of fusidic acid in tears
Overtime, the concentration of fusidic acid in tears decline. the decline is relatively low after instillation
It is an antibiotic that doesnt really penentrate ocular tissues very readily
Comparison between chloramphenicol and fusidic acid
fusidic acid not really recommended these days BUT advantage is safe for pregancy
expensive
Polymyxin B (POM) - what does it do
- PB attatches to and interferes with the functioning of the cell membrane of aerobic gram -ve bacteria
- bacitracin inhibits synthesis of cell wal in gram +ve bacteria
OTC propamidine
not an antibiotic! disinfectant
- active against gram +ve,
- less active against gram -ve
antifungal properties
- may be used topically for minor eye conditions such as conj and bleph
