Antibiotics Flashcards
What is the goal of antimicrobial therapy
to destroy pathogenic microorganisms (cidcl) or inhibit their growth sufficiently (static) to allow the host immune response to fight off the infection
The cure should not be worse than the ____
disease
What is the good therapeutic index
effective conc/ toxic concentration
What are antimicrobials
any substance or drug that can kill or inhibit the growth of microbes
What are the three main types of antimicrobials
disinfectants
antiseptics
antibiotics
What are disinfectants and what are examples
used to sterilize formites
formaldehyde, phenol, bleach
What are antiseptics and what are examples
applied to skin/mouthwash
iodine, rubbing alcohol, 3% H2O2, triclosan
What are antibiotics and what are examples
used on the outside/inside of the body
penicillin, tetracycline, erythromycin
What does bactericidal mean
kills bacteria
What does bacteriostatic mean
inhibits bacteria growth, must synergize with the intact immune system
What is the efficacy of antibiotics dependent on
dependent on the metabolic state of the bacteria
cell wall active antibiotics are only effective against actively dividing cells
What is MIC
Minimal Inhibitory Concentration
lowest concentration to inhibit growth
What is MCB
Minimal Bactericidal Concentration
lowest concentration to kill all the bacteria
What is the lowest concentration to kill all the bacteria called
Minimal Bactericidal concentration MBC
What is the lowest concentration to inhibit growth
Minimal Inhibitory Concentration MIC
What is MBEC
the MBEC value is the lowest dilution that prevents regrowth of bacteria from the treated biofilm
based on 96-well ELISA platform
allows the simultaneous determination of MBEC values of eight different antibiotics
assay involves the formation of 96 identical biofilms on plastic pegs on the lid of the MBEC device
biofilms are then exposed to test antibiotics for a defined time period then place in fresh bacteriologic medium in a second 96-well plate and incubated overnight
What are the four things that make a good antibiotic
- good therapeutic index: they must target the cellular machinery of the pathogen, but not the host. must have low side effects
- broad spectrum of activity: this is helpful when you need to treat a patient and don’t have time to confirm causative agent, think of sepsis onset
- generally target a single molecule
- good pharmacokinetics or bioavailability
What does it mean if an antibiotic has a good therapeutic index
it means the antibiotic targets the cellular machinery of the pathogen but not the host
you want it to have low side effects
What does it mean if an antibiotic has broad spectrum of activity
it means the antibiotic is used to treat a patient and the doctor doesn’t have time to determine the exact causative agent
means the antibiotic can treat various different types of bacteria
What are benefits of broad spectrum therapy
can treat various different types of bacteria
What are problems of broad spectrum therapy
…
What are the six mechanisms of antibiotic action
- Cell Wall Synthesis Inhibitors
- Cell Membrane Disruptors
- Protein Synthesis Inhibitors
- DNA Synthesis Inhibitors
- RNA Synthesis Inhibitors
- Unique Metabolic Pathways
What do beta-lactam antibiotics do
inhibit the formation of peptidoglycan cross-links by targeting transpeptidases
What are common members of beta-lactam antibiotics
more than half of all antimicrobial drugs are beta-lactams
most common members are penicillins and cephalosporins
How does penicillin work
targets cell wall synthesis
it has a beta-lactam ring
the ring inhibits the formation of peptidoglycan cross-links by targeting transpeptidases
What does Vanomycin target and how does it work
targets cell wall synthesis
binds to end of stem peptides (D-ala-D-ala) and prevents crosslink formation by targeting transpeptidase substrate
same as penicillin, but a different activity
What does Cycloserine target and how does it work
targets cell wall synthesis
blocks formation of peptide for crosslink
What does Bacitracin target and how does it work
targets cell wall synthesis
blocks movement across the membrane
the disaccharide subunits don’t reach the periplasm
the lipid carrier bactoprenol can’t be recelcyed
component of neosporin ointment which is topical only
What type of antibiotic is neosporin
its a type of bacitracin
What are the role of translation inhibitors antibiotics
antibiotics that target the bacterial ribosome
generally they target the ribosomal RNA scaffold
What do Chloramphenicol target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Macrolides target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Lincosamides target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Streptogramins target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Everninomycins target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Oxazolidinones target and how does it work
targets the 23S rRNA scaffolds of the 50S subunit
inhibits translation
What do Aminoglycosides target and how does it work
targets the 16S rRNA scaffolds of the 30S subunit
inhibits translation
What do Tetracyclines target and how does it work
targets the 16S rRNA scaffolds of the 30S subunit
inhibits translation
What are the antibiotics that are translation inhibitors and specifically target the 23S rRNA scaffolds the 50S subunit (6)
Chloramphenicol Macrolides Lincosamides Streptogramins Everninomycins Oxazolidinones
What are the antibiotics that are translation inhibitors and specifically target the 16S rRNA scaffolds the 30S subunit (2)
Aminoglycosides
Tetracyclines
What antibiotics interfere with DNA/RNA synthesis (5)
Metronidazole
Ciprofloxacin
Novobiocin
Rifampin
sulfa drugs are given in combination therapy
What does Metronidazole target and how does it work
targets and damages DNA by causing strand nicks/breaks
interferes with DNA/RNA synthesis
What does Ciprofloxacin target and how does it work
targets the DNA gyrase
interferes with DNA/RNA synthesis
What does Novobiocin target and how does it work
targets the DNA gyrase
interferes with DNA/RNA synthesis
What does Rifampin target and how does it work
targets the RNA polymerase
interferes with DNA/RNA synthesis
What are sulfa drug and how do they work
sulfa drugs are given as combination therapy
prevent the formation of nucleic acids by inhibiting the synthesis of folic acid
folic acid is an important precursor in purine biosynthesis
What does Linezolid (Zyvox) target and how does it work
targets the 50S subunit
resistance appeared soon after introduction
What does Daptomycin target and how does it work
Acyl tail targets the membrane
disrupts the membrane
VRE/MRSA resistance
What are new ideas for treating bacterial infections
- phage therapy holds promise
- do we need to kill the bacteria or can be tame them by anti-infective strategies or by disarming virulence factors
- can we outcompete them with probiotics and prebiotics and by fecal transplants curing patients with C. difficile
- can we target the resistance mechanism
like beta-lactamases with Clavulanic acid (augmentin)
What does Mupirocin target and how does it work
targets tRNA
inhibits protein synthesis of tRNA
What does Puromycin target and how does it work
targets tRNA
inhibits protein synthesis of tRNA
What are the antibiotics that target protein synthesis by specifically targeting tRNA (2)
Mupirocin
Puromycin
