Antibiotics and antimicrobial resistence Flashcards
Who is Paul Ehrlich?
-Came up with precursor to gram stain
-First treatment for syphilis - Treponema pallidum - first example of chemo
What is a growth factor analogue?
A substance related to a growth factor but blocks the utilisation of the growth factor e.g the sulfa drugs
Who is Sir Alexander Fleming?
-Prof of bacteriology at st Marys Hospitak in London
-1922 discovered lysozyme
-While growing staphylococcus aureus, found penicillium notam (penecillin) would prevent may bacterial growth
Who then worked on purification of penicillin after Fleming?
Howard Florey and Ernest Chain
-found penicillium chrysogenum would give much more penicillin
Who isolated streptomycin from streptomyces griseus and proposed the term antibiotic?
Selman Waksman
How can prokaryotes become resistant to antibiotics?
-natural resistance
-acquisition of resistance genes
-mutation of antibiotic target
Look at targets of antibiotics diagram
Example of narrow spectrum antibiotic?
Penicillin - gram neg usually resistant
Example of broad spectrum antibiotic?
Tetracycline - effective against gram neg and pos bacteria
Bacteriocidal vs bacteriostatic vs bacteriolytic
Bacteriocidal - kill bacteria
Bacteriostatic - stop them from ngrowing
Bacteriolytic - lyse the cells entirely
What do the majority of antibacterial drugs target?
The cell wall
What are ß-lactam antibiotics and what do they do and examples?
-Inhibit cell wall synthesis
-Targets transpeptidation - rxn that crosslinks 2 glycan linked peptide chains in peptidoglycan
-2/3 of antibiotics produced
-Penicillins, cephalosporins
-Have a ß-lactam ring
Are Gram pos or gram neg for susceptible to ß-lactam antibiotics?
Gram Positive cells
-Newly formed peptidoglycan layer has 2 D-Ala- one of which is cleaved to allow lining (transpeptidation)
What does Penicillin G act against?
Gram pos bacteria
Example of semi-synthetic penicillins? How are they formed?
-Ampicillin
-Carbenicillin
By a n-acetyl group modification
Bacterial resistence to penicillin enzyme?
What has to be used to prevent this?
Penicillinase (ß Lactamase)
ß lactamase inhibitors must be used e.g augmentin or clavamox which is clavulanic acid and amoxycillin
Semisynthetic penicillin - Methicillin?
Oxacillin?
Both - acid-stable, ß-lactamase-resistant
Semisynthetic penicillins - Ampicillin and Carbenicillin?
Both - broadened spectrum of activity, acid-stable, ß-lactamase-sensitive
Ampicillin - esp effective against gram neg bacteria
Carbenicillin - esp effective against Pseudomonas aeruginosa, ineffective orally
What are cephalosporins, what do they do?
-Fungus species Cephalosporium
-Beta-lactam ring
-Func same as penicillins - bond irreversibly to transpeptidases and prevent cross-linking of peptidoglycan
-Semi- synthetic
-Broader spectrum that penicillins
-Usually more resistant to beta- lactamases
What kind of antibiotic is vancomycin and what does it inhibit?
Glycopeptide antibiotic
Inhibits cell wall synthesis
How do bacteria respond to antibiotics that inhibit cell wall synthesis?
Have a thicker cell wall
What eaxctly do ß-lactams do to inhibit cell wall synthesis?
Inhibit transpeptidase directly
What exactly does vancomycin do to inhibit cell wall synthesis?
Inhibits transpeptidation reaction
What does cycloserine do exactly to inhibit cell wall synthesis?
Inhibits synthesis of building blocks
What does bacitracin do exactly to inhibit cell wall synthesis?
Inhibits the transport of building blocks
Example of cell membrane inhibitor?
Polymyxins - produced by some Bacillus spp
-Bind tightly to lipid A component of LPS (outer membrane of g neg)
How is daptomycin affective?
-Active in gram-pos bacteria
-Disruption of bacterial membrane through formation of transmembrane channels
Examples of antibiotics that are inhibitors of protein synthesis?
-Chloramphenicol
-Aminoglycosides : streptomycin, neomycin, gentamycin
-Tetracyclines (Rickettsias and chlamydia)
-Macrolides: Erythromycin (gram pos, used in children)
Macrolides - what does clarithromycin do?
-Binds to 50S ribosome
-Proetin synthesis inhibitor
-Respoiratory infections
Example of inhibitor of nucleic acid synthesis 1?
Rifamycin / rifampin
-inhibits RNA synthesis
-antituberculosis
-source: streptomyces mediterranei
Example of inhibitor of nucleic acid synthesis 2?
Quinolones and fluoroquinolones
-Ciproflaxacin
-Inhibits DNA gyrase
-UTIs
