Lecture | Antimicrobial & Resistance Flashcards
the capacity to kill or suppress the growth of microorganisms
ANTIMICROBIAL AGENTS
Sources of Antibiotics :
1. Streptomyces spp.
2. Bacitracin and polymyxin - Bacillus species
Microorganisms (natural)
Sources of Antibiotics : Chloramphenicol
Synthetic
Sources of Antibiotics : produced by the fermentation process
Semi-synthetic
Sources of Antibiotics : penicillins and cephalosporin
Semi-synthetic
Inhibit bacterial growth but generally do not kill the organism
Bacteriostatic Agents
kill target organism
Bactericidal
Classification of antimicrobial agent : penicillins & cephalosporins
β-Lactam antibiotics
Act by binding PBPs (penicillin-binding
proteins)
β-Lactam antibiotics
Inhibit cell wall synthesis
β-Lactam antibiotics
enzymes anchored in the cell membrane and necessary in the production and maintenance of the peptidoglycan layer
PBPs
core of the structure of our beta lactam antibiotics is
Beta-lactam ring
Classification of antimicrobial agent : Vancomycin
Glycopeptides
Also inhibit bacterial cell wall synthesis and Binds to the end of peptidoglycan
Glycopeptides
directly binds to the terminal D-Ala of the pentapeptidyl-glycosyl peptidoglycan intermediates
Vancomycin
blocks the transpeptidation
Glycopeptides/vancomycin
binds to the substrate of the enzyme
glycopeptides
drawback of glycopeptide
cannot penetrate to the outer membrane of most of gram negatives due to large size
Binds to and disrupts the cell membrane and inserts its hydrophobic tail into the membrane, disrupting the cell membrane and increasing its permeability, which results in cell death
Lipopeptide
Daptomycin - gram “?”
gram+
Polymyxins - Gram “?”
Gram -
are cyclic lipopeptide agents that disrupt bacterial cell membranes.
Polymyxins (polymyxin B and colistin)
act as detergents, interacting with phospholipids in the cell membranes to increase permeability.
Polymyxins
drawback about polymyxin
toxic to human cells
simultaneously attack two targets in the same folic acid metabolic pathway
Sulfamethoxazole (trimethoprim + sulfonamide)
fluoroquinolones target “?” in gram-negative organisms
topoisomerases II /DNA gyrase
fluoroquinolones target “?” in gram-positive organisms
topoisomerase IV
potent bactericidal agents and have a broad spectrum of activity
fluoroquinolones
Ciprofloxacin is under the classification of antimicrobial agent?
Quinolones
A semisynthetic antibiotics that bind to the enzyme DNA-dependent RNA polymerase and inhibit synthesis of RNA
Rifampin
Targets DNA transcription and With isoniazid and pyrazinamide for treatment of Mycobacterium tuberculosis
Rifamycins
Gentamicin, streptomycin, kanamycin are under the classification of antimicrobial agent?
Aminoglycosides
Inhibit protein synthesis:
binding to protein receptors on the organism’s 30S ribosomal subunit
Aminoglycosides
requires oxygen for it to be effective
Aminoglycosides
effective in aerobic gram negative and staphylococcus aereus(gram+), but ineffective against anaerobic bacteria
Aminoglycosides
bacterial uptake is accomplished by using combination cell wall active antibiotics such as b-lactams /vancomycin
Aminoglycosides
Doxycycline or minocycline are under the classification of antimicrobial agent?
Tetracyclines
Inhibit protein synthesis:
interfere with the binding of the tRNA-amino acid complexes to the ribosome
Tetracyclines
Broad spectrum of activity-bacteriostatic
Tetracyclines
prevents peptide chain elongation
Tetracyclines
Neiserria gonorrhoeae, mycoplasma, & spirochetes can be successfully treated with
Tetracyclines
Inhibit protein synthesis:
drug binding to the 23S ribosomal RNA (rRNA) on the bacterial 50S ribosomal subunit
Macrolide-Lincosamide-Streptogramin group
subsequent disruption of the growing peptide chain by blocking of translocation.
Macrolide-Lincosamide-Streptogramin group
Macrolides (erythromycin, clarithromycin, and azithromycin)
Gram positive bacteria, mycoplasmas, treponemes, and rickettsiae
Lincosamides (clindamycin and lincomycin)
Anaerobic gram-positive bacteria
Streptogramins (Quinupristin-dalfopristin)
Gram positive and some gram negative organisms
Chemical derivatives of erythromycin A and Telithromycin
Ketolides
Inhibit protein synthesis:
Bind to the 50S subunit of the bacterial ribosome
Ketolides
key difference between the only currently available ketolide, telithromycin, and the macrolides
Telithromycin maintains activity against most macrolide- resistant gram-positive organisms
Linezolid and tedizolid is under the classification of antimicrobial agent?
Oxazolidinones
Inhibit protein synthesis:
blocking the initiation step and translocation of peptidyl-tRNA from the A site to the P site
Oxazolidinones
prevent protein synthesis from initiation
Oxazolidinones
inhibits the addition of amino acids to the growing peptide chain by reversibly binding to the 50S ribosomal subunit –> inhibiting transpeptidation
Chloramphenicol
Bone marrow toxicity–> aplastic anemia
Chloramphenicol
Resistance resulting from the normal genetic, structural, or physiologic state of microorganisms
Intrinsic resistance
Resistance resulting from altered cellular physiology and structure caused by changes in a microorganism’s genetic makeup
Acquired resistance
record the result of our antimicrobial susceptibility test to detect resistance patterns in our clinical isolates
antimicrobial susceptibility profiles
vancomycin are effective against gram negative or positive
gram-positive
interfere with DNA replicatiin
Quinolones
