Antibacterials Flashcards
What do bactericidal drugs do?
Kill bacteria by disrupting cell wall synthesis, do not rely on host defenses.
What do bacteriostatic drugs do?
Stop the growth of bacteria by interfering with DNA synthesis, protein production or metabolism. The host defense then removes the static bacteria.
Give to inhibitors of folic acid synthesis
Sulphonamide
Trimethoprim
What does sulphonamide resemble?
p-aminobenzoic acid (essential precursr of folic acid)
What does trimethoprim resemble?
pteridine ring
Are folic acid inhibitors bacteriostatic or bactericidal?
Bacteriostatic.
What is the drug of sulphonamide combined with trimethoprim called?
Co-trimaxzole
What is trimethoprim chemically related to?
Anti-malarial drug pyrimethamine
What can trimethoprim be used for?
Many bacterial infections including UTIs and respiratory infections.
Which type of bacteria are harder for antibiotics to penetrate?
Gram-negative, because it has a more complex cell wall and cell membrane.
What does B-lactamase do?
Inactivated B-lactam which kills bacteria
What does clavulanic acid do?
Inhibits many B-lactamases so the B-lactam can kill the bacteria
What do B-lactams do?
Break oligopeptide linkages between chains of GlcNAc and MurNAc
Give 4 examples of semi-synthetic penicillins
- Amoxicillin
- Ampicillin
- Flucloxacilin
- Carbenicillin
What are penicillins?
Effective widely used antibiotics with a narrow to a broad spectrum of uses. Destroyed by bacterial amidases and B-lactamases. Interfere with cell wall peptidoglycan synthesis.
Give 3 uses of penicillins
- Bacterial meningitis
- Pneumonia
- Bone and joint infections
What are cephalosporins?
Naturally occuring with the same mechanism of action to penicillins. They are the 2nd choice for many infections. Lipid soluble. Vary in susceptibility to B-lactamases.
Give to examples of B-lactamase resistant B-lactam antibiotics.
Carbapenem.
Monolactam
GIve 3 antibiotics which inhibit bacterial wall synthesis but don’t target B-lactamase.
- Bacitracin
- Cycloserine
- Vancomycin
What are tetracyclines?
Competes with aminoacyl-tRNA for the A site on ribosoems. Oral or parenteral routes, some aren’t absorbed with Ca2+
What are tetracyclines the first choice for?
Rickettsial, mycoplasma, chlamydial infections, cholera and plague.
What does chloramphenicol do?
Blocks peptidyl transferase which binds to the 50S ribosome subunit. Lipid soluble. Can cause idiosyncratic depression of bone marrow.
What do aminoglycosides do?
Generates an abnormal codon, anti-codon recognition leading to misreading of the message. Bacteriacidal. `
What are macrolides?
Many membrered lactone ring with sugars attached. Bacteriostatic.
What does rifampicin do?
Blocks DNA-dependent RNA polymerase. Bacteriacidal.
What do quinolones do?
Inhibit DNA replication. Bacteriacidal. Treating tuberculosis and leptosy.
