Beta-Lactams

Question 1

what structural component is essential for biological activity of penicillins?

Answer 1

beta-lactam ring

Question 2

how is the problem of gastric acid sensitivity solved?

Answer 2

EWG at the alpha-carbon

Question 3

oxacillin, dicloxacilin, and nafcillin are exceptions to the elimination process of most penicillins (excreted unchanged through the kidneys)
how are these drugs eliminated?

Answer 3

hepatobiliary system

Question 4

explain the mechanism of penicillins

Answer 4

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

Question 5

how do autolysins assist in the antimicrobial mechanism of penicillins?

Answer 5

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

Question 6

penicillins are ineffective against which types of organisms (lifecycle)

Answer 6

cells with formed cell walls or microbes without cell walls

-must be actively multipying or growing

Question 7

describe the four mechanisms of bacterial resistance to penicillin

Answer 7

beta lactamase - antibiotic is inactivated
mutations - target is altered
pumps - antibiotics pumped out
porins - antibiotic cannot get in

Question 8

what are porins?

Answer 8

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

Question 9

which drugs are part of the penicillins

Answer 9

pen G (natural penicillin)
penicilin V (oral)

Question 10

the penicillins are effective against what species?

Answer 10

gram + and gram - cocci
gram + bacilli
spirochetes
anaerobes

Question 11

what species do the penicillins not cover

Answer 11

gram - bacilli and staph aureus

-beta-lactamase production

Question 12

which penicillin is more stable in an acidic environment

Answer 12

penicillin V

Question 13

which drugs are the beta-lactamase resistant penicillins

anti-staph penicillins

Answer 13

methicillin
cloxacillin
dicloxacillin
oxacillin 
flucoxacillin (newest, reserved for severe infection)

Question 14

what species do the beta-lactamase resistant penicillins cover?

Answer 14

staphylococcal infections that are resistant to pen G

not useful for gram - bacteria

Question 15

which drugs are the aminopenicillins?

Answer 15

ampicillin

amoxicillin

Question 16

what is the spectrum of the aminopenicillins?

Answer 16

gram + and gram - cocci, gram + and gram - bacilli, spirochetes, anaerobes

(similar to pen G plus gram - bacilli coverage)

Question 17

ampicillin is used for:

Answer 17

acute bacterial meningitis due to listeria

Question 18

the aminopenicillins are often used in combination drug with:

Answer 18

beta-lactamase inhibitors

Ampcillin/amoxicillin + clavulanic acid

Question 19

aminopenicillins are useful for:

Answer 19

H influenzas, ear infections, respiratory infections in children

Question 20

which drugs are antipseudomonal penicillins

Answer 20

carbenicillin
ticarcillin
piperacillin

Question 21

carbenicillin is used for:

Answer 21

UTIs resistant to other antibiotics

only in oral form

Question 22

ticarcillin is almost always given with:

Answer 22

clavulanic acid

Question 23

piperacillin is almost always given with

Answer 23

tazobactam

Question 24

antipseudomonal penicillins are used to treat infections caused by organisms not covered by penicillins including:

Answer 24

pseudomonas aeruginosa, proteus, enterobacter

Question 25

penicillins are sometims given with aminoglycosides (gentamicin, etc). why?

Answer 25

increases the bactiericidal activity and shortens length of treatment because
- penicillins alter cell wall synthesis, increases permeability to other antibiotics

Question 26

beta lactamase inhibitors include

Answer 26

clavulanic acid
sulbactam
tazobactam