Antibiotic Agents Targeting Bacterial Cell Wall Synthesis Flashcards
Clavulanic acid, tazobactam, and avibactam are all
b-lactamase inhibitors
Cefazolin (1stgen), cefuroxime axetil (2ndgen), ceftazidime (3rdgen), cefepime (4thgen), and ceftolozane (the latest) are all?
Cephalosporins
Ceftaroline is a
Cephalosporin for MRSA
Aztreonam is a
Monobactam
Imipenem is a
Carbapenem
Vancomycin, oritavancin, and dalbavancin are classified as
Glycopeptides
Daptomycin (pore former) and polymyxins (membrane disruptors) are examples of
Lipopeptides
Fosfomycin, bacitracin, and D-cycloserine are inhibitors of
Peptidoglycan precursors
Life-threatening infections require the immediate use of broad-spectrum agents or
Combination therapy
A microorganism is said to be resistant to a drug if therapeutic levels of the drug at a particular site cannot be
Safely or effectively achieved
Exposure to harmful agents such as antibiotics increases the selective pressure to maintain
Acquired resistance
Many drugs work selectively against Gram(+) bacteria. Fewer work selectively against Gram(-) bacteria. Drugs that work against both classes of bacteria are said to be
Broad spectrum
A drug whose selectivity is broadened by chemical modification is said to have an
Extended spectrum
The outer membrane of Gram(-) bacteria is relatively
Impermeable
Cell wall agents block proper assembly of the
Peptidoglycan layer
Join the sugars that make polysaccharide chains
Transglycolase enzymes
Join the sugar-linked peptides to x-link polysaccharide chains
Transpeptidase enzymes
Mimics D-Ala-D-Ala, the last two amino acids of the peptide-bridge precursor
Penicillin
Similar to transpeptidases. However, they use H2O to hydrolyze serine-lactam linkage
Serine B-lactamases
A distinct class that hydrolyze lactams by a different mechanism
Metallo B-lactamases
Possess no antibacterial activity. They are combined with blactam antibiotics to extend their half-lives
B-lactamase inhibitors
These inhibitors bind b-lactamases covalently and inactivate irreversibly
Beta-lctamase inhibitors
Initially, b-lactamases were encoded by chromosomal genes of some bacteria. Amplification of the genes led to increased
Activity
Later, lactamases were found on plasmids that could transfer from
Organism to organism
Most active against plasmid encoded b-lactamases in staphylococci, H. influenza, N. gonorrhoeae, salmonella, shigella, E. coli, K. pneumoniae
Clavulanic Acid
Least active against chromosomally-encoded b-lactamases in enterobacter, citrobacter, serratia, pseudomonas
Clavulanic acid
Serine β-lactamases come in which three classes
A, C, and D
Traditional B-lactamase inhibitors work primarily on
Class A enzymes
A broader spectrum β-lactamases inhibitor that works on class A and C enzymes, as well as some D enzymes.
Avibactam
The inhibitor is coformulated with 3rd generation cephalosporin, ceftazidime
-Note: The inhibitor does not contain a β-lactam core
Avibactam
How many classes of penicillins are there, defined by core structure plus substituents
Common penicillins, anti-staphylococcal penicillins, and extended-spectrum penicillins
Acid labile. b-lactamase susceptible. Suitable for Gram(+), Gram(-) cocciand non blactamase-producing anaerobes
Common penicillins
Acid stable. b-lactamase resistant. Suitable for b-lactamase producing strains of staph, as well as penicillin-susceptible strains of streptococci and pneumonococci
Anti-staphylococcal penicillins
Not suitable for enterococci, anaerobic bacteria, and Gram(-) cocciand rods
Anti-staphylococcal penicillins
Acid stable. Greater activity against Gram(-) because of their ability to penetrate outer membrane. Suitable for UTIs, sinusitis, otitis, lower respiratory tract infections
Extended-spectrum penicillins
Extended-spectrum penicillins are inactivated by
Lactamases
Inactivated by lactamases. Thus, available in combination with b-lactamase inhibitors (eg. amoxicillin + clavulanate = Augmentin)
Extended-spectrum penicillins
Routes of administration-oral, IV and IM (if combined with anesthetic). When taken orally, ingest one hour before or after meal to avoid binding to food proteins
Penicillins
Penicillins are eliminated by
Rapid active secretion
80% of a dose of penicillin can be cleared in
3-4 hours after administration