Booklet 6: Antimicrobial Drugs and Resistance Flashcards
List 3 important points about antimicrobial drugs
- They are compounds that kill or control the growth of microorganisms in the host
- Selective toxicity
- Two broad categories: synthetic and natural
What are growth factor analogs?
- Structurally similar to growth factors but do not function in the cell
- Analogs similar to vitamins, amino acids, and other compounds
Who were sulfa drugs discovered by and when?
Gerhard Domagk in the 1930’s
Are sulfa drugs fully synthetic?
Yes
How do sulfa drugs work?
-Inhibit growth of bacteria (ex. sulfanilamide) by inhibiting folic acid synthesis and thus nucleic acid synthesis.
How do quinolones work?
- They inhibit DNA gyrase (ex. ciprofloxacin) and prevent DNA supercoiling.
- They are active against both Gram-negative and Gram-positive bacteria
Are quinolones synthetic or natural?
Synthetic
What are natural antimicrobial drugs produced by?
Bacteria and Fungi
What percentage of known natural antibiotics are clinically useful?
Less than 1%
Antibiotics can be split up into synthetic or natural. They can also be split up into what two categories?
Broad spectrum vs narrow spectrum
Explain the difference between broad and narrow spectrum antibiotics.
Broad - targets most bacteria, has no preference for gram positive or gram negative
Narrow - targets specific bacteria, has a preference for either gram positive or gram negative
List 2 points about B-lactam antibiotics.
- Cell wall synthesis inhibitors
- Compromise over 50% of antibiotics used around the world.
What are 2 popular examples of B-lactam antibiotics?
- Cephalosporins
- Penicillins
Describe penicillin antibiotics.
- Discovered by Alexander Fleming
- Target cell wall (specifically peptidoglycan synthesis)
Are penicillins effective against gram positive or gram negative bacteria?
Gram positive. (Some synthetic forms are active against gram negative bacteria).
What are cephalosporin antibiotics made from?
The fungus: Cephalospyrium sp.
Are cephalosporins more broad than penicillins?
Yes (They not only cover gram positives but have some gram negative coverage as well).
List 2 points about cephalosporins
- Resistant to B-lactamases
- Commonly used to treat gonorrhoea
List 4 types of antibiotics created from bacteria.
- Aminoglycosides
- Macrolides
- Tetracyclines
- Novel Antibiotics
Describe aminoglycosides
- Amino sugars bonded by glycosidic linkage
- Examples include: streptomycin, kanamycin, neomycin, gentamicin.
- Target 30S subunit of the ribosome
- Useful against gram-negative bacteria
- Not commonly used, known as “last resort” antibiotics
Describe macrolides
- Lactone rings bonded to sugars
- Example: erythromycin (streptomycin erythreus)
- Broad spectrum
- Target 50S subunit of the ribosome (partial inhibition of protein synthesis - preferential translation of some proteins)
Describe tetracyclines
- Produced by several species of Streptomycin
- Broad spectrum
- Natural and semisynthetic
- Inhibit 30S subunit of ribosome
- Most widely used antibiotic along with penicillins
- Veterinary and as growth promoters (resistance)
List 2 types of novel antibiotics
- Daptomycin
- Platensimycin
Describe daptomycin
- Cyclic lipopeptide
- Active against gram positives
- Forms pores in cell membrane (depolarization)
Describe platensimycin
- New class of antibiotic
- Fatty acid biosynthesis inhibitor
- No host toxicity - Broad spectrum including MRSA and VRE
What does MRSA stand for?
methicillin-resistant staph aureus
Define: antimicrobial drug resistance
The ability of a microorganism to resist the effects of an antimicrobial agent to which it is normally sensitive
What two types of antimicrobial drug resistance are there?
Chromosomal vs plasmid-encoded
List some mechanisms of resistance and provide examples
- Reduced permeability - penicillin
- Inactivation of antibiotic - penicillins, chloramphenicol, aminoglycerides
- Alteration of target - erythromycin, streptomycin, norfloxacin
- Development of resistant biochemical pathway
- sulfonamides
- Efflux - tetracyclines, chloramphenicol, fluoroquinolones
What creates antibiotic resistance?
Widespread antibiotic usage in medicine, veterinary, and agriculture selects for resistance
What % of all antibiotics produced are used for agricultural practises?
80%
What does VRE stand for?
vancomycin-resistant enterococci
What are the two most commonly known resistant bacteria?
MRSA and VRE
List 4 points that would contribute to preventing antimicrobial resistance
- Prevention of infections
- Rapid, conclusive diagnosis
- Prudent use of antimicrobials (not using unnecessarily)
- Prevention of transmission
