1.6 Introduction To Antibiotics Flashcards
Define: Broad-Spectrum
A drug that is active on a wide range of bacteria, viruses, fungi or parasites
Define: Narrow-Spectrum
A drug that is active on a limited number of bacteria, viruses, fungi or parasites
Define: Bactericidal
An antibacterial that will kill the bacteria
Define: Bacteriostatic
An antibacterial that inhibits the growth of bacteria
What is meant by “selective toxicity”?
The antibacterials have specific targets in the bacterial cell so won’t have an effect on human cells.
What five features of bacteria does the selective toxicity of antibiotics target?
Cell Wall synthesis Protein synthesis DNA synthesis RNA synthesis Folic acid synthesis
What two classes of drugs target cell wall synthesis? Give examples of each
Beta-lactam antibiotics: Penicillin, Flucloxacillin, Amoxycillin, Cephalosporins
Glycopeptides: Vancomycin
What is the mechanism of action of beta-lactam antibiotics?
They prevent the formation of peptide bridges between adjacent strands of peptidoglycan by inhibiting the transpeptidase activity of Penicillin Binding Proteins (PBPs)
What changes does chemical modification of antibiotics result in?
Spectrum of activity
Toxicity
Stability
Describe Cephalosporins and provide some examples
Broader spectrum. Often given to patients with penicillin allergies. Cephalexin, Cefepine
What mechanisms of resistance do bacterium have to beta-lactams?
They acquire a gene encoding beta-lactam inactivating enzyme called beta-lactamase
What solution do we have to bacterial resistance through beta-lactamase?
Co-administer beta-lactams with beta-lactamase inhibitors such as clavulanate.
What is the mechanism of action of Glycopeptide antibiotics? And what group of bacteria do they work on? Provide examples
Bind to “D-Ala D-Ala” of the peptide NAM complex in peptidoglycan which prevents cell wall synthesis. Is only effective in gram positive bacteria. Vancomycin.
Name the 7 classes of drugs that inhibit bacterial protein synthesis.
Aminoglycosides Tetracyclines Streptogramins Macrolides Chloramphenicol Lincosamides Oxazolidinones
Describe and provide examples of Aminoglycosides.
Bind to 30S subunit of ribosome and block the initiation of translation and causes the misreading of mRNA Broad spectrum Aerobic, gram negative bacteria IV only Gentamycin
Describe and provide examples of Macrolides
Bind to 50S subunit of ribosome and prevent the continuation of protein synthesis. Gram positive bacteria Good oral bioavailability Erythromycin Clarithromycin Azithromycin
Describe and provide examples of Tetracyclines
Bind to 30S ribosomal subunit and block the attachment of tRNA to the ribosome Good oral bioavailability Gram positive bacteria Tetracycline Doxycycline
Name the Two classes of DNA synthesis inhibitors and provide examples.
Quinolones: Ciprofloxacin, Norfloxacin
Nitromidazoles: Metronidazole & Tinidazole
Describe and provide examples of Quinolones
Inhibit bacterial DNA replication by binding to and inhibiting DNA gyrase as DNA gyrase relieves stress on DNA during replication.
Good oral bioavailability
Broad spectrum, gram negative, aerobic bacteraemia
Ciprofloxacin
Norfloxacin
Name and describe the class of drugs that prevent RNA synthesis and provide examples.
Rifamycins
Bind to and inhibit bacterial RNA polymerase.
Rifampin
Name the two classes of drugs that inhibit folic acid synthesis and how they work.
Trimethoprim (bind to and inhibit bacterial dihydrofolate reductase, a key component of folic acid synthesis)
Sulfonamides (bind to and inhibit dihydropteroate synthesase, a component of folic acid synthesis)
Name and describe the four methods of antibiotic drug resistance.
Increased elimination: drug enters bacteria but efflux pump ejects it
Drug-inactivating enzyme: Enzymes modifies drug –> inactivating it
Alteration in target molecule: drug cannot bind target but leaves target still functional
Decreased uptake: Porin proteins prevent entry in to the cell.
