M6 L5 Antibiotics Flashcards
what is an antimicrobial agent
substances that kill or inhibit growth of microorganisms
classes of antimicrobial agents
- antibacterials
- antivirals
-antifungals - antiprotozoals
- anthelmintics (anthelmintics)
what is a bacterial cell
- prokaryotes
- some with have capsule, cell wall, cell membrane, or plasma membrane
- not a proper nucleus, but has genetic tiny materials floating (plasmids)
- can b gram +’ve or -‘ve
what does gram +’ve look under stain
purple, thick
what colour does gram -‘ve look under stain
pink, thin
what are cocci
circle bacteria
what are bacilli
rod-like bacteria
what are spirals
wavy/squiggly bacteria
classes of antibiotics
- according to action
- according to spectrum
- according to effect
what could antibiotics target (this is how we can differentiate them)
- cell wall
- cell membrane
- folic acid synthesis
- DNA
- Protein synthesis
what antibiotics target the cell wall
-penicillin
-cephalosporins
-vancomycin
what antibiotics target the folic acid synthesis
- sulfonamides
- trimethoprim
- co-trimoxasole
what antibiotics target the DNA
- quinolones
what antibiotics target the protein synthesis
-macrolides
- lincomasides
- tetracyclines
- aminolycosides
narrow spectrum antibiotics
- gram +’ve cocci: penicillin G
- gram -‘ve bacilli: aminoglycosides
broad spectrum antibiotics
- gram +’ve and -‘ve: tetracyclines
what are bacteriostatic antibiotics
inhibit growth and reproduction of bacteria without killing them
ex: tetracyclines -sulfonamides
what are bactericidal antibiotics
- kill the bacteria
- ex: penicillins - cephalosporins
addition antibiotic combo
1+1=2
synergism antibiotic combo
1+1=3
this is good u want this
- activity of combined agents is greater than sum of agents if given separately
ex:
- drug acting at sequential steps in metabolic pathway: sulfonamides + trimethoprim
- 1 drug prevents inactivation of 2nd: amoxicillin + clavulanate and imipenem + cilastatin
antagonism antibiotic combo
1+1=0
bad
what do bacteria do that causes antibiotics resistance
- altered receptors and enzymes
- altered rates of entry or removal
- enhanced inactivation
- synthesis of resistant pathways
- failure to metabolize drug
penicillin structure
- derived from penicillium fungus
- core of 6-aminopenicillanic acid
- beta-lactam ring: active part, destroyed by beta-lactamase enzyme
- side (R) group: determines type of penicillin
mech of action of penicillin
- inhibit the formation of peptidoglycan cross-links in bacterial cell wall
- spectrum: G +’ve +/- G-‘ve can do both
- bactericidal
absorption/excretion/ROA for penicillin
absorption: variable w half life = 30-60 min
excretion: thru kidney (90% tubular secretion), delayed by probenecid
ROA: oral, IV, IM
what is penicillin G (benzylpenicillin)
- mainly gram +’ve
- acid labile - only parenteral
- short acting
- can b broken down by acid in stomach so cannot b taken orally
- narrow spectrum
what is penicillin V (phenoxymethylpenicillin)
similar to penicillin G (relative)
but… can survive stomach acid! acid stable, can be taken orally
what is benzathine benzylpenicillin
long acting penicillin (2-4 weeks) - IM injection
what is beta-lactamase resistant penicillin examples
cloxacillin, dicloxacillin, methicillin
broad spectrum penicillin examples
ampicillin and amoxicillin (does not resist staph aureus)
adverse effects of penicillin
- hypersensitivity (anaphylaxis)
- GI sympt: nausea, diarrhea
- superinfection: candidiasis
- drug resistance
penicillin resistance
- destruction by beta-lactamase enzyme
- synthesized by staphylococci
- avoided by: clavulanic acid (potent-b-lactamase inhibitor, combined w some penicillins ex: amoxicillin), beta-lactamase resistant penicillins (ex: cloxacillin, dicloxacillin, methicillin
cephalosporins
- beta-lactam antibiotic
- derived from cephalosporium fungus
- action/adverse effects/resistance}similar to penicillins
1st generation of cephalosporins
- mainly gram +’ve
ex: cefadroxil, cephalexin
2nd generation cephalosporins
gram -‘ve > gram +’ve
ex: cefaclor, cefuroxime
3rd generation cephalosporins
broad spectrum w more gram -‘ve
ex: cefotaxime, ceftriaxone
4th generation cephalosporins
broad spectrum
ex: cefepime, cefpirome
5th generation cephalosporins
broad spectrum + MRSA
ex: ceftaroline
tetracyclines
mech of action:
effect:
spectrum:
Ca2+ chelation:
oral absorption:
administration:
adverse effects:
ex:
mech of action: reversible, inhibition of protein synthesis thru binding to 30S ribosomal subunit
effect: bacteriostatic
spectrum: broad
Ca2+ chelation: ->insoluble complex -> inactivation
oral absorption: variable
administration: oral, topical
adverse effects: delayed bone growth, tooth discoloration, photosensitivity
ex: tetracycline, doxycycline
aminoglycosides
mech of action:
effect:
spectrum:
Ca2+ chelation:
oral absorption:
administration:
adverse effects:
ex:
mech of action: irreversible, inhibition of protein synthesis thru binding to 30S ribosomal subunit
effect: bactericidal
spectrum: gram -‘ve
Ca2+ chelation: n/a
oral absorption: poor
administration: IV, IM, topical
adverse effects: nephrotoxic, ototoxic
ex: gentamicin, streptomycin
sulfonamides
- 1st antimicrobial drug discovered
- bacteriostatic
- spectrum: gram +’ve and -‘ve
structure of sulfonamides
- derivatives of p-aminobenzoic acid (PABA)
- diff “R” groups -> diff types
sulfonamides mech of action
reversible competitive
- decreased dihydropteroate synthetase enzyme
- decreased conversion of PABA to dihydropteroate
decrease folic acid synthesis
trimethroprim mech of action
- decreased DHFR
(dihydrofolic acid -> tetrahydrofolic acid)
co-trimoxzole
sulfamethoxazole +trimethoprim
useful for UTI’s??
sulfonamides pharmakinetics
- absorption: variable
- carried by albumin
- metabolized in liver
- excreted thru kidney
sulfonamides adverse effects
- hypersensitivity
- urinary tract obstruction
- hemolytic anemia
route of admin for sulfonamides
oral, topical
quinolones mechinism
- synthetic antibiotics
- inhibit bacterial topoisomerase 2 (DNA gyrase) enzyme (required for transcription and DNA replication)
quinolones spectrum, indications, administration
spectrum: broad
indications: complicated UTI - serious G -‘ve infections
administration: oral
ex: ciprofloxacin
