Cell Wall Inhibitors Flashcards
Are β-Lactams bactericidal or bacteriostatic?
Bactericidal
What is the mechanism of action of β-Lactams?
Inhibit cell wall synthesis
What is the generic structure of cephalosporins comprised of?
A = dihydrothiazine ring B = β-lactam ring R = acyl side chain adaptations
What is the mechanism of action of cephalosporins?
Interfere with cell wall synthesis by binding to penicillin-binding proteins (PBPs) located in bacterial cell walls. Inhibition of PBPs leads to inhibition of the final transpeptidation step of peptidoglycan synthesis.
What are the 3 mechanisms of resistance to cephalosporins?
- Production of ß-lactamase
- Alteration of PBPs
- Alteration of outer membrane permeability that interferes with PBP access by the drug
What is the general action of 1st generation cephalosporins?
Best activity against gram-positive aerobes, with good activity against a few gram-negative aerobes
What Gram (+) do 1st Gen cephalosporins hit?
Meth-susc S. aureus*
Pen-susc S. pneumoniae
Group streptococci
Viridans streptococci
What Gram (-) do 1st Gen cephalosporins hit?
PEK
P. mirabilis
E. coli
K. pneumoniae
What are the main examples of 1st Gen cephalosporins?
Cefazolin
Cephalexin
What is the general action of 2nd generation cephalosporins?
In general, slightly less active against gram-positive aerobes, but more active against gram-negative aerobes
Do 2nd generation cephalosporins have action against anaerobes?
The cephamycins of the second generation agents have activity against anaerobes.
What Gram (+) do 2nd Gen cephalosporins hit?
Meth-susc S. aureus*
Pen-susc S. pneumoniae
Group streptococci
Viridans streptococci
What Gram (-) do 2nd Gen cephalosporins hit?
HENPEK H. influenzae Enterobacter spp. (some) Neisseria spp. P. mirabilis E. coli K. pneumoniae
What are examples of 2nd Gen cephalosporins?
Cefuroxime
Cefprozil
Cefoxitin
Cefotetan
What are the cephamycins (2nd Gen)?
Cefoxitin
Cefotetan
Cefmetazole
What are the cephamycins useful for?
Anaerobes. They are the only cephalosporins that have activity against anaerobes
Bacteroides fragilis
What is the general action of 3rd generation cephalosporins?
In general, are less active against gram- positive aerobes, but have greater activity against gram-negative aerobes, including some β-lactamase-producing strains
What Gram (+) do 3rd Gen cephalosporins hit?
Less Gram (+) action