Flashcards in Beta-Lactams Deck (26):
what structural component is essential for biological activity of penicillins?
how is the problem of gastric acid sensitivity solved?
EWG at the alpha-carbon
oxacillin, dicloxacilin, and nafcillin are exceptions to the elimination process of most penicillins (excreted unchanged through the kidneys)
how are these drugs eliminated?
explain the mechanism of penicillins
impair develoment of bacterial cell wall
- by inhibited transpeptidase enzymes (Penicillin binding proteins PBP) (covalent, irreversible) required for formation of cross-links between peptidoglycan strands
-normal bacterial growth depends on balance between cell wall deposition and autolysis
how do autolysins assist in the antimicrobial mechanism of penicillins?
autolysins are enzymes needed for normal remodeling of cell wall
-they continue to work in the presence of penicillin (ie absence of PBPs)
-cell wall is weakened even further
penicillins are ineffective against which types of organisms (lifecycle)
cells with formed cell walls or microbes without cell walls
-must be actively multipying or growing
describe the four mechanisms of bacterial resistance to penicillin
beta lactamase - antibiotic is inactivated
mutations - target is altered
pumps - antibiotics pumped out
porins - antibiotic cannot get in
what are porins?
gram negative rods
beta-lactam antibiotics enter cells via porins
mutations can alter porins, which makes it more difficult for beta-lactam to enter cell
which drugs are part of the penicillins
pen G (natural penicillin)
penicilin V (oral)
the penicillins are effective against what species?
gram + and gram - cocci
gram + bacilli
what species do the penicillins not cover
gram - bacilli and staph aureus
which penicillin is more stable in an acidic environment
which drugs are the beta-lactamase resistant penicillins
flucoxacillin (newest, reserved for severe infection)
what species do the beta-lactamase resistant penicillins cover?
staphylococcal infections that are resistant to pen G
not useful for gram - bacteria
which drugs are the aminopenicillins?
what is the spectrum of the aminopenicillins?
gram + and gram - cocci, gram + and gram - bacilli, spirochetes, anaerobes
(similar to pen G plus gram - bacilli coverage)
ampicillin is used for:
acute bacterial meningitis due to listeria
the aminopenicillins are often used in combination drug with:
Ampcillin/amoxicillin + clavulanic acid
aminopenicillins are useful for:
H influenzas, ear infections, respiratory infections in children
which drugs are antipseudomonal penicillins
carbenicillin is used for:
UTIs resistant to other antibiotics
only in oral form
ticarcillin is almost always given with:
piperacillin is almost always given with
antipseudomonal penicillins are used to treat infections caused by organisms not covered by penicillins including:
pseudomonas aeruginosa, proteus, enterobacter
penicillins are sometims given with aminoglycosides (gentamicin, etc). why?
increases the bactiericidal activity and shortens length of treatment because
- penicillins alter cell wall synthesis, increases permeability to other antibiotics