What is the use of drugs to treat a disease?
Chemotherapy
What interferes with the growth of microbes within a host?
antimicrobial drugs
What is a substance produced by a microbe that, in small amounts, inhibits another microbe?
antibiotic
What is it called when a drug that kills harmful microbes without damaging the host?
selective toxicity
What is the source of more than half of the antibiotics?
Streptomyces, a filamentous soil bacterium, other from Bacillus and molds (fungi)
According to Table 20.1, which group microorganisms are most antibiotics derived from?
Actinomycetes
Which spectrum have the least side effects?
Narrow spectrum - it only impacts certain types of pathogens (penicillin affects primarily Gram positive)
Antibiotics only work to destroy...
bacteria
Which spectrum antibiotics have a small range of pathogens they are effective against?
Narrow
Which spectrum antibiotics have a broad range of pathogens they are effective against?
Broad (effect Gram negative or Gram positive)
What is the danger of broad spectrum antibiotics?
Normal microbial flora will also be destroyed and can lead to a superinfection (when a surviving organism overgrows like fungus)
What are the criteria for ideal antibiotics?
Selective toxicity
soluble in body fluid in (blood brain barrier)
Resists excretion (stays in the body long enough)
Shelf life
Doesn't lead to resistance
Cost not excessive
Hypoallergenic (natural or synthetic)
What are the actions of antimicrobial drugs?
Inhibition of cell wall synthesis (penicillins)
Inhibition of protein synthesis (erythromycin, tetracycline)
Inhibition of synthesis of essential metabolites *this makes an antimicrobial a "magic bullet" since bacteria has folic acid and we (humans) do not
Inhibition of nucleic acid replication and transcription (quinolones)
If an antimicrobial drug inhibits organelles that are 70s why is it not a "magic bullet" or in other words, why is it not an effective antimicrobial drug for humans?
In order for a drug to be a "magic bullet" it has to kill the pathogen but not hurt the host. Drugs that target organelles with 70s cannot be a magic bullet because mitochondria are also 70s and would be impacted by the drug.
Which drug is an example of an antibacterial antibiotic cell wall inhibitor?
Penicillin
What is the common core of penicillins?
B-lactam ring which is CH-CH-N-C and this prevents cell wall formation
What breaks the b-lactam ring?
Penicillinase
What is natural penicillin?
Natural from mold
Best use for streptococcus spp and most staphylococcus
What is semisynthetic penicillin?
More resistant to penicillinase
Methicillin-resistant - Staphylococcus aureus (MRSA)
The administration of penicillin: Penicillin G requires...
Injection because stomach acid destroys it
The administration of penicillin: Penicillin Y requires...
Either injection or orally
What are cephalosporins?
Narrow spectrum
Inhibits cell wall formation in gram positive pathogens
2nd generation- extended spectrum includes gram negative
3rd generation - includes pseudonomads, injected
4th generation - oral
What are some polypeptide antibiotics?
Bacitracin - topical application (less risk since not injected or consumed); works against gram positive
Vancomycin - glycopeptide, "last line" against antibiotic resistant S. aureus
What is the last line against antibiotic resistant S. aureus?
Vancomycin
Patient must be hospitalized
Drug will affect kidneys
Where is all antibiotic resistance?
In the plasmid
What are antimycobacterium antibiotics?
Isoniazid (INH) - inhibits mycolic acid synthesis
Ethambutol - inhibits incorporation of mycolic acid
Which antibacterial antibiotics inhibit protein synthesis?
chloramphenicol, erythromycin,streptomycin, tetracyclines
What are the side effects of streptomycin?
Can cause auditory nerve damage and possibly kidney damage
What are the side effects of tetracyclines?
Suppression of normal flora and cause superinfections; brownish discoloration of teeth in children; possible kidney damage in pregnant women
What is chloramphenicol?
simple structure, easily manufactured; broad spectrum and penetrates body well, but has some serious side effects. Used only when no suitable alternatives are available
What are macrolides?
Contain macrocyclic lactone ring (i.e. erythromycin - not able to penetrate most Gram negative cell walls, so limited spectrum - often alternative to penicillin)
Which drug is a broad spectrum drug that binds 50S subunit, inhibits peptide bond formation?
Chloramphenicol
Which drug is a broad spectrum drug that changes the shape of 30S subunit?
Aminoglycosides (streptomycin, neomycin, gentamycin)
Which drug is a broad spectrum drug that interferes with tRNA attachment?
Tetracyclines
Which drug affects Gram-positive; binds 50S, prevents translocation?
Erythromycin and macrolides
Which drug affects Gram positives, binds 50S, prevents translocation?
Erythromycin and macrolides
Which drug affects Gram positives, binds 50S subunit, inhibits translation?
Streptogramins and synercid
Which drug affects Gram positives, binds 50S subunit, prevents formation of 70S ribosome?
Oxazolidinones (Linezolid)
Occurs when the effect of two drugs together is greater than the effect of either alone. When combination of drugs provides the same effect at a fraction of the concentration of either alone
Synergism
Occurs when the effect of two drugs together is less than the effect of either alone.
Antagonism
List ways in which antibiotics are misused
Using outdated, weakened antibiotics
Using antibiotics for the common cold and other inappropriate conditions
Use of antibiotics in animal feed
Failure to complete the prescribed regimen
Using someone else's leftover prescription
Can determine MIC and also minimal bactericidal concentration (MBC)
broth dilution
What percentage of Americans get a viral disease per year?
90%
Are very limited in which groups they are effective against and most have been developed in response to HIV (AIDS)
anitviral drugs
synthetic nucleosides which interfere with DNA and RNA synthesis
Nucleosides analogs
Inactivates reverse transcriptase (needed to make DNA from RNA viral genome)
enzyme inhibitors
Any drug ending -zole is which type of drug?
Antifungal drug
Interferes with sterol synthesis
imidazoles and triazoles
interferes with mitosis and thus inhibits fungal reproduction. Useful against infections of fungi in hair and nails
griseofulvin
Produced by Streptomyces, combine with sterols in the fungal plasma membrane and make the membrane excessively permeable which kills the cell
polyenes
Why are fungi harder to attack?
Because fungi are also eukaryotic
What is a broad spectrum drug that binds to 50S subunit, inhibits peptide bond formation
Chloramphenicol
Contain macrocyclic lactone ring (ex. erythromycin) and not able to penetrate most Gram negative cell walls, so limited spectrum - often alternative to penicillin
Macrolides
Which drug has a simple structure, easily manufactured (more cheaply than isolating from Streptomyces). Broad spectrum and penetrates body well, but has some serious side effects. Used only when no suitable alternatives are available
Chloramphenicol
Which bactericidal can cause auditory nerve damage and possibly kidney damage?
Streptomycin
What broad spectrum drug produced by Streptomyces penetrates body tissues well and are effective against intracellular rickettsias and chlamydias
Tetracyclines
Can suppress the normal flora and cause superinfections. Not advised for children due to brownish discoloration of teeth or for pregnant women (possible liver damage)
Tetracyclines
What glycopeptide is the important "last line" against antibiotic resistant S. aureus
Vancomycin
All antibiotic resistance is though the ______
Plasmid - double stranded DNA in the plasma
Which type of penicillin can only be injected because it is destroyed by stomach acid?
Penicillin G
Which type of penicillin can be administered orally or by injection?
Penicillin V
Which are the natural penicillin?
Penicillin G and V
What advantage does semisynthetic penicillin have over natural penicillin?
It is resistant to penicillinase and has an extended spectrum
Which is natural from mold and is the choice for Streptococcus and Staphylococcus spp?
Natural penicillin
Which is more resistant to penicillinase and Methicillin resistant - Staphylococcus aureus (MRSA)
Semisynthetic penicillin
What does the b lactam ring do?
prevents cell wall making
What does penicillinase do?
breaks the ring and makes penicillin inactive
What is the common core of penicillin
b lactam ring
What are the same as b lactinase inhibitors?
carbapenems and monobactam
what are the inhibitors of cell wall synthesis?
Penicillin - penicillinase-resistant penicillins
extended spectrum penicillins
penicillins - b lactamase inhibitors
carbapenems
monobactam