L7 - antibiotics and resistance Flashcards
What’s the difference between a bactericidal and a bacteriostatic antibacterial?
Bactericidal agents kill the bacteria directly the other stops them from replicating
Antibacterial can have a ‘broad’ spectrum, what is meant by this?
Affects a wide range of bacteria for example many gram positive and negative bacteria
Give some considerations to take into account when selecting an antibiotic
Active at target site? Will it reach site of infection? Formulation? What dosing regime will be required? Cross interactions with other meds?toxicity to organ? Does it require monitoring? Does the patient have allergies to it?
Give a way of testing effectiveness of antibiotics in the lab
Disc testing
Minimum inhibitory concentration (MIC) broth microdiluton
MICE test
See slides
Antibacterials can be categorised based on their target site (mechanism of action. One example is inhibition of protein synthesis, give the other three ways and give an example of a class of drug in each
-cell wall synthesis inhibition Beta-lactams (penicillins and ceohalosporins)/ glycopeptides -protein synthesis inhibition Tetracyclines/aminoglycosides/macrolides -cell membrane function Polymixins -Nucleic acid synthesis Quinolones/trimethoprim/rifampicin
Describe the mechanism of action of penicillin in detail
Penicillin binds the penicillin binding protein in peptidoglycan cell walls and prevents the cross linkage in the cell walls - this leads to weaker cell walls and subsequent degradation
What are the three types of antimicrobial resistance?
Intrinsic - microbe simply lacks the target of the drug
Acquired - microbe acquires new or mutates genetic materials so that the drug no longer works
Adaptive - genes for resistance are switched on by the organism during times of stress
One way in which microbes can cause resistance is to mutate their target sites (of the antibiotics), name another way
Enzymatically alter the target site
Enzymatically destroy or alter antibiotics
Antibiotic resistance is spread in two ways, one is through chromosomal gene mutation, explain this way and the other
Chromosomal gene mutation - the bacterium with the resistance survives the antibiotic stress and multiplies so whole population have resistance
Horizontal gene transfer - Bacteria swap resistant DNA via plasmids via pilli
What 4 subgroups make up the beta-lactams?
Penicillins/cephalosporins/carbapenems/glycopeptides
Penicillins are mainly active against what kind of bacteria?
Streptococci (mainly) and staphylococci
Co-amoxiclav is a penicillin which has a very broad spectrum, as well as affecting many gram positive and some gram -ve’s what specifically else does it affect?
Anaerobes
What kind of microbes do cephalosporins not affect and what side effect do they have which causes concern?
Anaerobes
Associated with c. Difficile growth which ncauses diarrhoea, likely the result of stripping the normal gif flora
Which member of the penicillins is normally still able to be used in patients with a penicillin allergy?
Carbapenems although patients need monitoring
Glycopeptides like vancomycin are not absorbed so not really given orally apart from for ?
C. Difficile
