Antimicrobials and Antimicrobial Stewardship Flashcards
What are the potential systems that could be used to classify antimicrobials?
- Bactericidal vs. Bacteriostatic
- Broad vs. Narrow Spectrum
- Target site/ Mechanism of action
- Chemical structure “Class”
Why is classification by bactericidal/bacteriostatic activity not the best way to classify antibmicrobials?
Depending on the dose, the same antimicrobial can act either of these ways
Why is the spectrum of antibiotic not the best way to classify such drugs?
“Spectrum” is not an absolute term
What are the four targets for antimicrobials to destroy pathogens?
- Block cell wall synthesis
- Block protein synthesis
- Block nucleic acid synthesis
- Block/disrupt cell membrane function
Name four classes of antimicrobial that inhibit cell wall synthesis and some examples
Beta- Lactams:
Penicillins e.g. Penicillin, Amoxicillin, Flucloxacillin
Cephalosporins e.g. Cetriaxone
Carbapenems e.g. Meropenem
Glycopeptides e.g. Vancomycin
Name three classes of antimicrobial that inhibit protein synthesis in order to destroy the pathogen.
Give some examples
Tetracyclines - Tetracycline, doxycycline
Aminoglycosides - Gentamicin
Macrolides - Erythromycin
Name a class of antimicrobials that destroy pathogens by preventing nucleic acid synthesis Give an some examples
Quinolones - Trimethaprim, Ciprofloxacin
Name a class of antimicrobials that kill the target cell through inhibiting or disrupting cell membrane function Give an example
Polymixins e.g. Colistin
Penicillin is particularly effective against which microorganism?
Streptococci
Amoxicillin is particularly effective against which type of bacteria?
Gram positive (also some action against gram negative)
Flucloxacillin is particularly active against what microorganism/s?
Staphylococcus and Streptococci
What is an advantage and a disadvantage of Cephalosporins?
Advantage: Active in CSF
Disadvantage: Associated with C. Diff infection
Tetracyclines are particularly effective against what type of bacteria?
Gram positive
Tetracyclines cannot be given to patients under what age?
12years
Gentamicin has good activity against what type of bacteria and where?
Gram positive bacteria
In blood and urine
What are the mechanisms by which Ciprofloxacin and Trimethoprim inhibit nucleic acid synthesis?
Ciprofloxacin: inhits DNS gyrase
Trimethoprim: inhibits folic acid
Name two classes of antifungals and their mechanism of action
Azoles- inhibit cell membrane synthesis e.g. Fluconazole
Polyenes- inhibit cells membrane function e.g. Nystatin, Amphotericin
How does aciclovir act as an antiviral?
Inhibits viral DNA polymerase
Name three types of antibiotic resistance and what this means in respect to these methods of antimicrobial resistance
Intrinsic- has never worked, usually permanent
Acquired- did work but doesn’t now(new genetic material, mutation), usually permanent
Adaptive- organism responds to a stress and some are able to survive and have the potential to withstand some conditions, usually reversible
What are the three mechanisms that antimicrobials use to avoid killing by antimicrobials and infer resistance?
Drug inactivating enzymes e.g. Beta-lactamase
Altered target e.g. MRSA
Altered uptake- decreased permeability or efflux if antibiotic e.g.tetracyclines
What are the two stages to the mechanisms by which antibiotics acquire resistance?
- Chromosomal gene mutation - mutation by chance, if beneficial this dominant strain will persist in the population
- Horizontal gene transfer - genetic material from the mutant strain transmitted to other bacteria
What are the 3 methods of horizontal gene transfer?
- Conjugation - genetic material exchanged during temporary union between two cells
- Transduction - transmission of genetic material via a bacteriophage
- Transformation - prokaryotes take up fragments of DNA (often as plasmids) from environment
How can antibiotic activity be measured?
- Disc Sensitivity
2. Minimum Inhibitory Concentration
True or False: all exposure of bacteria to antimicrobials infers antimicrobial resistance
True
