Antibiotics Flashcards
What is meant by a semi-synthetic antibiotic?
An antibiotic that has been modified to increase efficacy
What is meant by a broad spectrum antibiotic?
One that works against gram positive and gram negative bacteria
Penicillins, cephalosporins and cephamycins are what class of antibiotics?
B-lactam antibiotics
Penicillium chrysogenum is a fungus that produces which type of antibiotic?
Penicillin
What is the mechanism of action of B-lactam antibiotics?
They inhibit cell wall synthesis
In bacteria, transpeptidation reaction is essential in the crosslinking of the cell wall.
Transpeptidase can also bind to B-lactam ring - the cell wall is still formed but no cross linking takes place making it weak and prone to cell lysis due to osmotic pressure
Which group of antibiotics has a 6 membered dihyrothiazine ring?
Cephalosporins
Cephalosporins have a different mode of action to penicillins. True or false?
False - same mode of action
Are cephalosporins naturally produced or semi-synthetic?
Semi synthetic giving them a broader spectrum of activity
What are B-lactamases?
Enzymes produced by bacteria that provide multi-resistance to B-lactam antibiotics
Cephalosporins are often less resistant to B-lactamases. True or false?
False - they are more resistant
Streptomycin, kanamycin, neomycin and gentamycin are examples of which group of antibiotics?
Aminoglycosides
How do aminoglycosides work?
They inhibit the protein synthesis of the 30S ribosomal subunit in bacteria
Are aminoglycosides active against gram negative or gram positive bacteria?
Gram negative
Which group of antibiotics contain sugars bonded by glycosidic bonds?
Aminoglycosides
Which group of antibiotics contain large lactone rings connected to sugar moieties?
Macrolides
Erythromycin is an example of an aminoglycoside. True or false?
False - it is a macrolide
How do macrolides work?
They inhibit protein synthesis at the 50S ribosomal subunit
Macrolides are used in patients allergic to penicillin. True or false?
True
Which group of antibiotics is useful in the treatment of Legionella pneumophila?
Macrolides
Are tetracyclines broad spectrum or narrow spectrum antibiotics?
Broad spectrum
Which group of antibiotics has a basic structure which consists of a napthacene ring system?
Tetracyclines
Tetracyclines interfere with the 50S ribosomal subunit in bacterial. True or false?
False - interfere with the 30S subunit
Why do microbes require growth factors?
Because they cannot synthesise them
What are growth factor analogues?
It is a synthetic compound that blocks the utilisation of growth factors. It has a similar structure to the growth factor, however, cannot duplicate the growth factor’s function in the cell
Sulfanilamide is an analogue of ______ ; a component of folic acid
PABA (P-aminobenzoic acid)
The synthesis of folic acid is blocked by which sulfa drug?
Sulfanilamide
Do bacteria get their folic acid in the same way that eukaryotes do?
No - they synthesise their own whereas eukaryotes get theirs from their diet
What makes Isoniazid a narrow spectrum drug?
It works against Mycobacterium only and interferes with the synthesis of mycolic acid
Quinolones are antibacterial compounds that interfere with DNA _____
gyrase
Most antibacterial drugs also target host structures, resulting in toxicity. True or false?
False - antiviral drugs do that not antibacterial
The least successful antivirals are the nucleoside analogues. True or false?
False - they are the most successful
How do nucleoside analogues work?
They block reverse transciptase (by binding directly to it) and the production of viral DNA
What do protease inhibitors do?
Inhibit the processing of large viral proteins into individual components
What do fusion inhibitors do?
Prevent viruses from successfully fusing with the host cell
What are interferons?
Small proteins that prevent the viral multiplication by stimulating antiviral proteins in uninfected cells
Why do fungi pose special problems for chemotherapy?
Because they are eukaryotic
What do ergosterol inhibitors do?
Target the unique fungal plasma membrane component ergosterol
1,3 B-D glucan synthase is inhibited by _______
echinocandins - used to treat Candida infections
