,Lecture 2: Antibiotics with cell
wall and membrane as their
target
Penicillin G:
Target
Bacterial infections
only active against fast dividing bacteria
Mechanism
It inhibits peptidoglycan synthesis (cell wall synthesis) using β-lactam
fast excretion via kidney, non-toxic,
Side effects
Unstable at acidic conditions, sensitive to all known β-lactamases, less active against gram - frequently
allergic reactions
Penicillin V:
Target
Bacterial infections
only active against fast dividing bacteria
Mechanism
Same as Penicillin G, but electronegative O-atom added so less unstable in acidic conditions, can bypass the
stomach
It inhibits peptidoglycan synthesis (cell wall synthesis) using β-lactam
fast excretion via kidney, non-toxic,
Side effects
It will stick to many things in the body, so you have to give 4 doses a day.
Ampicillin:
Penicillin with the addition of an NH2 group and phenyl group
Bacterial infections
Good bioavailablity
Amoxicillin:
Penicillin with the addition of an NH2 group and phenol group, also against
gram –
Bacterial infections
Excellent bioavailability
Then instead of an amino group, a carboxyl group is placed on that position. These
are called carboxypenicillins called carbenicillin and carfecillin. These can also be
administered orally and have a better activity against G- bacteria. However, if the R
group is polar it has a poor adsorption.
, What are common examples regarding lactamase inhibitors (this is called suicide inhibitor)?
Clavulanic acid: given with amoxicillin
How does clavulanic acid work?
Clavulanic acid fits in the bucket of the lactamase forming a complex which is IRRIVERSIBLE
Sultamicilline: (prodrug) it is a structure that contain the antibacterial and
lactamase inhibitor. When it is in the stomach, due to the low acidity it
cleaves off forming those building block
Tazobactam
lactamase inhibitors
In combination with piperacillin, back-up antibiotic, intensive care
medicine
Bacterial infections, diabetes-related food infections, febrile neutropenia
Cephalosporin C
Inhibition of the transpeptidase enzyme, has a less reactive βlactam ring, good leaving group
Cefalexin
1st generation, good against gram+, bad against gram
Airway infections, skin infections, bladder infections
Cefoxitin
2nd generation, urethane group functionality is more stable than ester group, better lactamase stability (steric
hindrance by methoxy group), variable activity against gram+, improved activity against gram
Infections, very βlactamase resistant
Ceftobiprole
ack-up cephalosporin, ‘5th’ generation, anti-MRSA, resistant against Staphylococcus βlactamase, inhibits
Staphylococcus PBP2
Skin and soft tissue infections, IV, Canada, Switzerland and EU
Vancomycin
This is a not beta lactam it is a back up treatment only in hospital pharmacy
It interferes with the cell wall at diffent place
It inhibits the cross linking
inhibits the synthesis of the cell wall by binding to peptide chains and preventing cross linking.
Against which type of bacteria is vancomycin used?
It is used against gram+ bacilli, often as back-up antibiotic in serious infections.
Bacitracin
inhibits the export of building blocks
Against which type of bacteria is Bacitracin used?
against gram+ bacilli and is nephrotoxic
why is it noly used on skin and eyes
because it is nefrotoxic
There is poor bioavailability, so often use of cream for skin and eyes.
Cycloserine
It is a D-alanine-mimic
inhibits the attachment of D-alanine amino acids to the peptide chain of NAM.
Phosphomycin
inhibits the precursor of peptidoglycan
Against which type of bacteria is Fosfomycin used?
