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Microbiology (1)
| Question | Answer |
|---|---|
| Antibacterial agents are produced by? | Fungi (mold), Bacteria (Streptomyces), or synthetic means (manipulation of existing antimicrobics) |
| What is the MIC (minimal inhibitory concentration)? | A term in micrograms/mL that gives the minimal amount of antimicrobic needed to inhibit growth of an organism |
| Which major groups of antimicrobial agents are considered to be Narrow-Spectrum agents? | Benzyl penicillin, Penicillinase-Resistant Penicillins, Erythromycin, Clindamycin, Vancomycin |
| What antimicrobics act on CELL WALL SYNTHESIS? | (1) BETA LACTAMS (penicillin, cephalosporin, carbapenem, monobactam) & GLYCOPEPTIDES (vancomycin and teicoplanin) |
| What drugs belong in the group GLYCOPEPTIDES, and what do they do? | CELL WALL SYNTHESIS inhibitors--vancomycin and teicoplanin |
| What drugs are included in the BETA LACTAMS? | penicillin, cephalosporins, carbapenems, monobactams |
| B-lactams function by doing what? | inhibiting the transpeptidation reactions that seal peptide crosslinks between glycan chains in peptidoglcan, which cause the cell to become susceptible to osmotic lysis |
| B-Lactams target what? | PBP's--> penicillin-binding proteins |
| What is one important EXCEPTION about B-LACTAMS? | they only affect bacteria that are synthesizing new cells walls. Prexisting are not affected bc their peptidoglycan is mature. |
| B-LACTAMS can MOST definitely not be used to treat what classes of organisms? | WALL-LESS (Mycoplasma) and INTRACELLULAR (Chlamydia and Rickettsia) |
| How do penicillins basically differ? | They differ in the way they affect gram negatives or their susceptibility to penicillinases (beta-lactamases) produced by Staphylococcal species |
| Which drugs are in the penicillinase-resistant penicillins? | methicillin, nafcillin, oxacillin |
| methicillin, nafcillin, and oxacillin are in what category of drugs? | they are penicillinase-resistant penicillins (B-lactams) |
| What is active against penicillinase-producing S. aureus? | methicillin, nafcillin, oxacillin |
| What drugs are in the category Penicillin? | penicillin (G, benzyl penicillin), Ampicillin, Amoxicillin |
| As a physician, you get syphillus from all your promiscus sex with your nurses. What should you primarily give yourself? You then find out you also got gonorrhea. What now? | penicillin G, penicillin G should be enough, assuming that it isn't B-lactamase positive. |
| You have 12 yo old girl with a sore throat that cultures positive for B-hemolytic strep? What should be your primary treatment? | penicillin G/benzyl penicillin |
| You have a 10yo boy who has meningitis. You isolate Neisseria meningiditis in culture. What is your primary treatment? | penicillin G/benzyl penicillin |
| You have 2 patients with N. gonorrhoaea and only enough Penicillin for 1 person. Is there a scientific way you could decide who should get it? | You could do a sensitivity to see if 1 of the patients has B-lactamase negative N. gonorrheae, which would be the recipient. |
| You have are told that 4 unidentified cultures before you are susceptible to Penicillin G, primarily. You are also told that they are all different. What are they most likely if they are primarily susceptible to Penicillin G? | Treponema pallidum (syphilis), B-hemolytic strep (or other streptococcal species), Neisseria meningitidis, and B-lactamase negative strains of Neisseria gonorrhoeae |
| How do ampicillin and amoxicillin differ from Penicillin G? | Ampicillin and amoxicillin have a slightly more expanded G- spectrum, and they are active against some wimpy members of Enterobacteriaceae. |
| You are told by an attending physician to give a patient with an Enterobacteriaceae infection a drug from a member of the Penicillins? Which to give? | Amoxicillin or Ampicillin (Penicillin G will not work), and ampicillin and amoxicillin will really only work of the Enterobacteriaceae strain is wimpy. |
| what are the anti-staphylococcal penicillins? | Methicillin, Nafcillin, Oxacillin (bc they are B-lactamase stable) |
| Staphylococci are immune to what Penicillins? | penicillin G, amoxicillin, ampicillin |
| If you give a patient Nafcillin, then what other orgs will you probably cover? what will you definitely not cover? | streptococci; gram negatives |
| Which B-lactam antibiotics can be used for MRSA (penicillin, cephalosporins, carbapenems, monobactam)? | none of these will work |
| MRSA gains resistance to B-lactamse stable antibiotics by what mechanism? | they have altered PBP-2 (altered penicillin-binding protein 2), involved in PG synthesis |
| MRSA is treated most likely with what? | vancomycin, a glycopeptide |
| Vancomycin resistant SA can be treated with what? and how do they work? | Synercid (quinipristin/dalfopristin) or Linezolid--these are both agents that inhibit protein synthesis |
| What are the extended spectrum penicillins, and what are they used for? | ticarcillin, piperacillin, carbenicillin; used as ANTI-PSEUDOMONAL (against gram- bacilli) but they've also developed resistance. |
| You have a patient who you've isolated Gram Negative Bacilli from. What penicillin would you use? | extended release penicillins |
| What are clavulanate, sulbactam, and tazobactam? | penicillinase inhibitors |
| what is augmentin? | ampicillin/sulbactam or amoxicillin/clavulanate |
| what is ampicillin with sulbactam? | augmentin |
| what is amoxicillin with clavulanate? | augmentin |
| what is timentin? | ticarcillin/cavulanate--an extended release penicillin with a B-lactamase inhibitor |
| what is ticarcillin with clavulanate? | timentin |
| B-lactamase inhibitors are commonly added to B-lactams to add extra strength. Which two drugs commonly contain these? | augmentin and timentin |
| What is the advantage of using a B-lactamase inhibitor? | B-lactamase inhibitors can be used to target gram-negative bacteria when used with a B-lactam, bc many gram- bacteria produce beta-lactamase (which accumulates in the periplasm) |
| When would you use augmentin? | with organisms that are resistant to ampicillin or amoxicillin |
| You have a patient with Neisseria gonhorrea. You treat with penicillin, as it is the primary trx, but he doesn't seem to be getting better. Why? and what would be your new treatment? | he's probably got B-lactamase (+) N. gonorrhea, so you should give him AUGMENTIN (which has amoxicillin/clavulonate or ampicillin/sulbactam a B-lactamase inhibitor) |
| What B-lactamase positive organisms would you commonly treat with AUGMENTIN (ampicillin/sulbactam or amoxicillin/clavulonate)? | Moraxella catarrhalis; H. influenzae, Neisseria gonhorrhea, S. aureus, and a bunch of anerobic coverage |
| when would you use Timentin? | when you have a B-lactamase (+) organism that is more likely gram- bacilli and anerobes |
| carbapenems (B-lactams) include what? | imipenem and meopenem |
| Why can imipenem affect gram- if it functions much like other B-lactams? | it is the smalled B-lactam and it's a zwitterion so it can fit through the porin channels in the OM of g- bacteria |
| Why did enterococci become a more common nosocomial pathogen? | first generation cephalosporins came out which at first worked for B-lactamse + SA, but it wasn't active against enterobacteria so they were selected |
| what are the first generation cephalosporins? | cephalexin and cefazolin |
| when are first generation cephalosporins generally used? | as prophylaxis for many surgical procedures to treat wound infections is most likely SA or Strep pyogenes |
| What happens as the generations go up in cephalosporins? | their gram negative coverage goes up |
| which cephalosporins have the least gram negative coverage? | first generation |
| second generation cephalosporins include what? | cefurxime and cefotetan |
| which cephalosporin is more active against enterobacteriae? | second generation |
| Third generation cephaolsporins include? | ceftazidime, cefoperazone, cefotaxime, and ceftriaxone |
| Third generation cephalosporins have a reasonably broad spectrum of activity against what? | gram-negative bacilli |
| Which cephalosporins are more active against Pseudomonas aeruginosa? (be specific) | THIRD GENERATION: ceftazidime and cefoperazone; FOURTH GENERATION: cefepime |
| what is vancomycin's spectrum? | almost all gram positives (aerobes/anaerobes), but NO gram- coverage |
| Which gram positives normally become resistant to Vancomycin? | E. faecium |
| You have a patient that has gram positive meningitis. A medical student suggests Vancomycin, knowing it has good coverage. WHy is the attending extremely pissed. | Vancomycin does treat G+'s well, but it does not cross the BBB, you idiot. |
| Which protein syntheisis inhibitors act on the 50s ribosomal subunit? | MACROLIDES (erythromycin, azithromycin, clarithromycin); CLINDAMYCIN; LINEZOLID; STREPTOGRAMINS [Synercid (quinupristin/dalfopristin)] |
| Which protein synthesis inhibitors work on the 30s ribosomal subunit? | Tetracyclines, Aminoglycosides, |
| Macrolides...what do they target, and what is the result? | 50s, inhibit chain elongation |
| You have a patient with Streptococci, and you see on her chart she is allergic to penicillin. What is a logical choice. | erythromycin |
| Erythromycin is also effective against what? | mycoplasma, legionelle, and chlamydia |
| What is the difference between azithromycin and erythromycin? | azithromycin has a larger spectrum (B-lactamase+ H influenzae, M catarrhalis, and N. gon) |
| What is a good agent for empiric treatment of sinusitis, otitis media, and pneumonia? | azithromycin |
| ONLY _________ and _________ can be treated with a 1st generation penicillin without being concerned about resistance | Strep throat, syphilis |
| The drug of choice to treat Rocky Mountain Spotted Fever is? | Doxycycline. |
Created by:
crfnr5
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