Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
|
MOA of cell wall synthesis inhibitors + Examples |
Inhabit some step in bacterial peptidoglycan synthesis. (Selective toxicity bc human cells have no cell wall) Penicillins - penicillin G, amp, amox, clox Cephalosporins - ceftazidime Glycopeptides - van |
|
|
Beta lactam antibiotics |
Products of 2 fungi molds (penicillium and cephalosporium) |
|
|
Semi synthetic antibiotics |
Amox + amp + meth (against gram -) |
|
|
MOA of cell membrane inhibitors & examples |
Disorganize the membranes which rapidly kills the cells Polymyxin Polyene Azoles eg Imidazole (inhabits ergosterol synthesis) |
|
|
MOA of protein synthesis inhibitors & examples |
Inhibit some step of protein synthesis Tetracycline - tetra, doxy Chloramphenicol Macrolides - erythromycin Aminoglycosides - strep, genta, kana |
|
|
MOA of drugs ch act on Nucleic Acids & Examples |
Blocks cell growth by affecting DNA/RNA synthesis or binding to it so theirs msgs cannot be read Quinolones - ciprofloxacin, naldic acid Sulfonamides + Trimethoprim - co trimoxazole, trimethoprim Metronidazole |
|
|
MOA of sulfonamides (competitive inhibitor/anti metabolite) |
Sulfonamides are structural analogs of PABA and compete w it for the enzyme that combines PABA and pteridine (dihydropteroate synthetase) in the initial stage of folate synthesis |
|
|
Mechanisms of Antimicrobial Resistance (list 3) |
1. Produce enzymes to inactivate antibiotics eg beta-lactamase destroys penicillins + cephalosporins 2. Alter membrane to prevent antibiotic uptake eg changing permeability in tetra res 3. Modifies target to prevent interaction w antibiotic eg mutations to change receptor |
|
|
Mechanisms of Antimicrobial Resistance (list 3) |
4. Dev of metabolic pathways that by pass site of action of antibiotic eg sulfonamides + trimeth resistance 5. Increasing production of metabolites which overcomes “tying up” of bacterial enzymes wrt drugs that resemble substrates 6. Efflux pump - channels that actively export antibiotics out of the cell as soon as it enters |
|
|
Control of Resistance (list 9) |
Conservative + specific use Enough amt + long enough to eliminate Select according to known susceptibility Narrow spectrum when etiology is known Use combinations Prophylaxis only if proven valuable + short T Avoid envi contamination Aseptic handling to prevent spread of resist Don’t use therapeutically valuable antibiotics for non medical purposes |
|
|
When is Antimicrobial Sensitivity/Susceptibility testing performed? |
Organisms w variable sensitivity eg Shigella Patients not responding to adequate therapy Patients w depressed IS Relapsing cases |
|
|
When is Antimicrobial Sensitivity testing NOT performed? |
If bacteria is a normal flora contaminant If culture is mixed ie not pure For organisms w predicable sensitivity (S pyogens + N meningitis sensitive to penicillin while Proteus spp resistant to tetracyclines) |
|
|
Principle of Dilution Technique for sensitivity |
1. Graded amts of antibiotic is added to agar or broth 2. Inoculated w test bacteria 🧫 3. Turbidity indicates growth MIC (min inhibitory conc) - smallest amt of agent needed to inhibit growth of test bacteria MBC (min bactericidal conc) - “ “ to kill “ “ |
|
|
Principle of Disk Diffusion in Sensitivity Testing |
1. Impregnate disk of blotting paper with known vol + conc of agent 2. Place on plate of agar 🧫 uniformly inoculated w test organism 3. Agent diffuses from disk to medium and the growth of the test 🦠 is inhibited @ a distance related to its sensitivity Resistant - smaller zones of inhibition |
|
|
External Factors influencing Zone size in Disk Diffusion Test (list 5) |
Inoculum density (McFarland’s Std) - too heavy -> size falsely reduced -> false resistance Time of disk app (3-5m) - longer -> size falsely reduced -> false resistance Temp - too 🥶 -> inhibits growth -> size falsely increased -> false sensitivity Agar depth (4mm) - less -> size falsely increased -> false sensitivity Disk potency - deteriorated potency -> size falsely reduced -> false resistance |
|
|
Interpretation of Zone Size |
Resistant - will NOT respond to r/x regardless of dose or site Intermediate- likely to respond to larger doses than normal or conc @ infection site (consider other drugs) Sensitive - will reposed to r/x @ normal doses |
|
|
WHO recommends the Kirby-Bauer NCCLS Modified Disk Diffusion techniques for standardization... what does this entail? |
1. Reliable Muller Hinton agar - prepare medium (ph 7.2-7.4), pour 25ml of MHA per plate on level surface, use control strain + stored @ 2-8oC for up to 2w 2. Discs of correct Antimicrobial content 3. Turbidity std = McFarland’s 0.5 - barium sulfate std against ch the turbidity of the test and control inocula can be compared |
