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81 Cards in this Set
- Front
- Back
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Define selectivity |
The ability to kill microbes without harming the host |
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What does an agent that has absolute selectivity do?
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Targets a structure that we absolutely do not have in our bodies
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Are antiviral treatments very selective?
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No
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Are fungi and parasites eukaryotic or prokaryotic? What kind of selectivity will animicrobials to them have?
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Eukaryotic. It will be relative selective.
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What are the two classes of antibiotics? What do they do?
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Bactericidal (kill bacteria) and bacteriostatic (stop growth)
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How do bacteriostatic drug usually work?
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Binds revesibly with the bacteria and doesn't let it work.
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What is the goal of bacteriostatic drugs?
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You limit the growth enough so that the host can use their immune system to do the rest. This is limited in immunocompromised people.
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How does sulfanilamide work? How does it make bacteria static?
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Inhibits the synthesis of folate. Once the existing folate is used up, the bacteria start plateauing in growth.
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How do aminoglycosides get into bacteria?
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It is cotransported with oxygen in the electron transport chian.
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What are the three main targets of antibiotics?
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1. Cell wall synthesis
2. DNA synthesis 3. Protein synthesis (ribosomes) |
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How do beta-lactams work? What class are they?
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They bind to transpeptidase preventing protein crosslinkages in the peptidoglygcan wall. It is bacteriocidal.
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How do glycopeptide antibiotics work?
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They bind to the terminal AA of the 4/5 peptide chain and inhibit cell wall synthesis that way.
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What are the 4 types of beta-lactam antibiotics?
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1. Penicillin
2. Cephalosporin 3. Carbapenem 4. Monobactam |
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What type of bacteria can traditional penicillin be used for? Why?
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Only gram positive because it can't pass through the capsule.
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WHat is another drawback to penicillin?
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It is susceptible to betalactamase.
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Where does betalactamase come from?
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bacteria like staph aureus
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What is ampicillin?
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A variation of penicllin that has an added amino group so it can penetrate gram negative.
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What is amoxicillin.
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A variation of penicllin that can penetrate gram negative and can also be absorbed orally.
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What is methicillin (nafcillin, oxacillin)
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A variation of penicllin that is resistant to beta lactamase, but has lost it's ability to penetrate gram negative.
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WHat's so special about cephalosporins?
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They are resistant to beta lactamase.
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How are cephalosporins classified?
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By generation. These are additional modifications that have been made to increase their effectiveness.
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Describe the pros carbapenems.
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These have the broadest spectrum of all the beta lactams and are resistant to betalactamase.
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Describe the drawbacks of carbapenems.
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They are not absorbed well so can only be given by IV as a last resort
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Describe monolactams/
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They have been modified so heavily that they can no longer kill gram positive. They are beta lactamase resistant though.
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What are the two types of glycopeptide antimicrobials?
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Vancomycin and teichoplanin
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What are the hydrophilic/hydrophobic properties of glycopeptides?
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large and lipophilic
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What does this mean for what it can affect?
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Can only do gram positive because the capsule layer of gram negative are both hydrophilic and phobic in areas.
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What are the 6 classes of antibiotics that work by inhibiting protein synthesis?
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1. Aminoglycosides
2. Tetracycline 3. Macrolides 4. Clindamycin 5. Chloramphenicol 6. Oxazolidonones |
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Where will aminoglycosides bind?
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Mainly to the 30S of ribosomes to prevent tRNA from forming the inititation complex
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Where will newer aminoglycosides bind? Why?
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to the 50 S to increase the sopectrum.
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How are aminoglycosides traported into the cell?
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Through oxidative phosphorylation.
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What are some examples of aminoglycosdies?
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streptomycin
gentamycin (usually of choice) neomycin |
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How do resistance mechanisms to aminoglycosides work?
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Enzymes which would phosphorylate, adelylae, or acetylate the drugs to inactivate them.
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Describe how tetracyclines work.
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They bind reversibly to the 30S and do what the aminoglycosides do except they are bacteriostatic.
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What can tetracyclines get into that aminoglycosides cannot? WHat does this result in in cildren?
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It gets into teeth and bones. It used to stain them in children so we don't use them anymore for them.
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What is the main example of a tetracycline?
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Doxycycline.
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How do macrlides work?
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they bind to the 50S ribosome to block translocation.
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What are two examples of macrolides?
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Erythromycin and Azithromycin (Z-oack)
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Describe chloramphenicol.
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Binds to 50S ribosome
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Why don't we use it in the US?
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It is kind of toxic and inhibits the synthesis of all sorts of blood cells (WBC and RBC). However, it is cheap to make and is prevalent in 3rd world countries.
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What is a special propoerty of the penetrance of chloraphenicol?
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It can penetrate our cells and get to intracellular microbes like rickettsiae.
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Describe how clindamycin works.
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Binds to 50S subunit similar to the macrolides, but has extended spectrum to the gram negaive anaerobes.
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What is a negative side effect of clindamycin?
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The proliferation of C. difficile, leading to diarrhea
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Describe Oxazolidonones.
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It is the most recently approve antibiotic which binds the 50S reversibly. It is active against gram positives that are resistant to other agents.
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What is an efflux pump?
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A pump that bacteria develop to pump out the antibiotics.
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What are the 4 classes of antibiotics that inhibit nucleic acid synthesis?
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Quinolones
Metronidozole Rifampin Folate inhibitors |
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How do quinolones work?
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They inhibit DNA gyrase through topoisomerase II
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How do bacteria resist quinolones?
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mutations in the gyrase
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What does the addition of flouride to quinolone to made fluoroquinolone do?
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It increases their absorption, but it also has many negative side effects
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What are two examples of fluoroquinolones?
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Ciprofloxacin and Levoquin
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What does metronidozole do?
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It introduces SS breaks in the DNA
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How is metronidozole delivered and what happens to it to become active?
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It is delivered as a prodrug and will ponly be redyuced to be active in the presence of anerobes and protzoans.
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Describe rifampin function
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Binds to the b-subunit of RNA polymerate to inhibit transcription
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What is the only organism that rifampin is used for? Why?
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mycobacterium tuberculosis because it has a very slow replication rate and needs to have antibiotics given over a long period of time for it to die out. (doesn't really make sense)
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Describe folate inhibitors. Why is it an absolute antibiotic?
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Folate is necessary for the synthesis of DNA nucleotides for bacteria. We get all our folate from dietary sources so we aren't affected.
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What is an example of an antibiotic that is a cell membrane disrupter? Why don't we use it in the US?
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Polymixins. They are toxic to our cell membranes as well.
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When does penicillin work the best?
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WHen the cell is growing.
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When is it not good to use penicillin then?
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When you are inhibiting protein synthesis because there is little growth
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Do you ever use antagonistic antibiotics?
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Yes. When you need to overcome resistance.
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What is intrinsic drug resistance?
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When the drug is not toxic due to some intrinsic characteristic of the bacteria.
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What is the intrinsic resistance of mycoplasma?
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They don't have a cell wall which means that they are intrinsically resistant to all cell wall antibiotics.
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What is the intrinsic resistance of anerobes?
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They do not have oxidative phosphorylation so are resistant to aminoglocosides.
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Where do intrinsic resistances from from?
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The chromosome of the bacteria
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What is the intrinsic resistance of staphylococcus?
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They produce betalactamase from their chromosomes
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WHat are the two types of acquired resistance?
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1. Mutational change
2. Plasmid tranmitted from another organism |
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How is the fidelity of DNA polymerase in bacteria? What ceonsequence does this have?
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Not that welll. This means that they can mutate quickly.
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What are R plasmids?
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Plasmids that transmit resistance genes.
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What is conjugation?
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When you transfer a plasmid from one bacteria to another
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What is transposition?
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When a gene from a plasmid jumps onto the chromosome
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What are three mechanisms for reisstance?
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1. Altered transport (exclusion)
2. Altered target 3. ENzymatic inactivation of the antibiotic |
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What is included in altered transport?
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Efflux pumps and also barriers to entry
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What does clavulanic acid do? What does it look like?
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It is also a beta lactam and will take the hits from the beta lactamase while binding with it to inactivate it.
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What is the best example of a combination with a beta lactam drug with calvulanic acid?
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Augmentin- amoxicilin with clavulanic acid?
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What kind of resistance did MRSA develop?
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It altered the target. It has an altered penicillin binding protein that no longer binds penicillin.
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What kind of resistance did vancomycin resistant enterococcus develop?
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It adds an extra lysine AA to the end of the peptide so that vancomycin cannot bind.
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How is resistance to ribosomal antibiotics created commonly> |
Production of new enzymes that methylate an adenine in the 23s rRNA preventing antibiotic binding. |
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why is it so important to study antibiotics above the other drugs (anti viral, anti fungal, anti parasitic, anti cancer)? |
they have been responsible for the most improvement in human survival
viral- hides in human cells, hard to target fungal- eukaryotic so kills us as well parasite- we don't have much of them? cancer- can't selectively target our own cells |
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what is the idea behind bacteristatic drugs? |
stop the growth and let the bacteria die or the immune system handle the rest |
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what kinds of drugs to give immunocompromised pt? can you always do this? |
bacteriocidal- no because a lot are resistant and must have bacteristatic |
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explain |
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where can drug resistance arise? 3 |
1. bacteria hides in place not accessible (biofilm) 2. covers up transporter to bring it in 3. mutates binding targets |
