Antibiotic Therapies Flashcards
What are bacteriostatic antibiotics
inhibit the growth of bacteria
what are bacteriocidal antibiotics
kill bacteria
What gives an antibiotic a broad spectrum
act against many gram negative and gram positive bacteria
What are the qualities of an ideal antibiotic
selective toxicity
long half-life (no constant administering)
appropriate tissue distribution
what is selective toxicity
antibiotic targets the bacteria and not the host
is 100% of an oral antibiotic absorbed
no
how are oral antibiotics excreted
urine
liver/ biliary tract into faeces
What processes are targeted by antibiotics
peptidoglycan synthesis
protein synthesis
nucleic acid synthesis
What are common cell wall anti-microbials
penicillins
cephalosporins
glycopeptides
which common cell wall antimicrobials are beta-lactam sensitive
penicillin
cephalosporins
what are the targets of B-lactams
penicillin binding proteins (PBP)
How do B-lactam antimicrobials work
antimicrobials contain B-lactam ring
recognised by cell wall synthesising enzyme
synthesis halted
What dipeptide is mistook for B-lactam by enzyme
D-alanine D-alanine terminal
How are the penicillins excreted
rapidly via kidneys
What are the limitations of the penicillins
patients can be hypersensitive (allergic)
rapid excretion
resistance
How have microbes developed a penicillin resistance
clinical overuse
penicillin was exposed to many microbes
resistant strains naturally selected for
Which type of organism is flucloxacillin used on
gram positive organisms
Which type of penicillin is used on gram negative and gram positive microbes
amoxicillin
Which type of penicillin is used on gram negative organisms only
temocillin
Why is co-amoxiclav used
contains clavulanic acid which inhibits B-lactamases
Why are the benefits of amoxicillin
well absorbed orally
good tissue distribution
What are B-lactamases
microbial enzymes that destroy the B-lactam ring
What penicillin is prescribed for staphylococci and streptococci only
flucloxacillin
What are the properties of cephalosporins
long half life
few side effects
more resistance to B-lactamases
broad range
How are cephalosporins excreted
kidneys/urine
what is the downside of an antibiotic with a broad range
can have an impact on the host (flora)
How do glycopeptides work
binds to end of peptide side chains
inhibits peptidoglycan synthesis
How are glycopeptides excreted
kidneys/urine
why do glycopeptides only work on gram positive organisms
outer membrane in gram negative organisms stops use of glycopeptides
How do antibiotics target metabolic pathways
microbes contain pathways unique to them
How do protein synthesis inhibitors target prokaryotes
prokaryotic ribosomes differ to eukaryotic ribosomes
How do protein synthesis inhibitors work
attach to bacterial ribosomes blocking steps in protein synthesis
what type of protein synthesis inhibitor has transient ribosome binding
bacteriostatic - protein synthesis resumed once antibiotic is removed
what type of protein synthesis inhibit has permanent ribosome binding
bacteriocidal
What are the 3 main classes of protein synthesis inhibitors prescribed
aminoglycosides
tetracyclines
macroslides
What is a common aminoglycoside prescribed
gentamicin
What are the properties of gentamicin
given IV (not gut absorbed)
mainly used for gm -ve aerobic
What is the risk associated with gentamicin
causes damage to kidneys
what are the properties of tetracyclines
stops peptide chain elongation
broad spectrum
what are the risks associated with tetracyclines
increasing resistance
destruction to normal gut flora
what happens if gut flora is damaged
results in increasing risk to secondary infections to C.diff
How do macro slides inhibit protein synthesis
bind to 50s subunit
block translocation/release of peptide
what antibiotics target nucleic acids
fluoroquinolones
metronidazole
How do quinolones kill bacteria
bind to DNA subunit and prevent supercoiling - new dna cannot be synthesised
What is metronidazole prescribed for
anaerobes
Protozoa
What intermediate metabolism can be blocked by antibiotics
folic acid synthesis
why should bactericidal and bacteriostatic antibiotics never be combined
cancel each other out
block protein synthesis - need lytic enzymes
why are some antibiotics given in combination
cover broad range of possible infections
prevent development of resistance
which 4 antibiotics increase the risk of a C.diff infection
Cephalosporins
co-amoxiclav
ciprofloxacin
clindamycin
What type of bacteria are tetracyclines used against
intracellular
