9.2 Antibiotics Flashcards
Compare Bactericidal vs Bactericidal
Bactericidal: kill target organisms.
Bactericidal: inhibit/delay bacterial growth and replication.
Give an example of a Quinolones and what does this inhibit?
Ciprofloxacin ➞ targets DNA girase which interferes with separation/reannealing of dsDNA ➞ Inhibits nucleic acid synthesis
What is Trimethoprim?
Give an other drug with the same MoA
Folic acid antagonists ➞ blocks nucleotide synthesis
Sulphonamides (but rarely used)
What is Rifampicin
Inhibits nucleic acid synthesis ➞ binds β-subunit of bacterial RNA polymerase
Give an example of an aminoglycoside and what does this inhibit?
Gentamicin ➞ binds the 30s ribosomal subunit causing misreading of mRNA thus inhibiting protein synthesis
Give an example of a Macrolide and what does this inhibit?
Erythromycin ➞ binds to the 50s ribosomal subunit, prevents movement of ribosome along mRNA, inhibiting translocation ➞ inhibits Protein Synthesis
What do tetracylines inhibit?
binds to the 30s ribosomal subunit, preventing attachment of tRNA to ribosome complex, preventing additon of amino acids ➞ inhibiting protein synthesis
Give 4 drugs that target cell wall synthesis and specifically explain how
1) Penicillin – binds and blocks peptidases involved in cross-linking the glycan molecules
2) Cephalosporins – same as penicillin
3) Vancomycin – hinders peptidoglycan elongation
4) Cycloserine – inhibits the formation of the basic peptidoglycan subunits
What is the disk diffusion test + what would the results indicate
Measures antibacterial activity- effectivness of antibacterial
Confluent growth of bacteria “bacterial lawn” will be seen where growth is NOT inhibited
“Zones of inhibition” (no growth) will be seen when strain is susceptible to that antibiotic concentration in agar
What is the E-test, how is it done and what can it help us determine?
Another way to determine antimicrobial sensitivity
Place a strip with antimicrobials onto agar plate ➞ strain of bacterium will not grow near a conc of antibioticif it is sensitive
Results can be used to determine a “Minimum inhibitory concentration (MIC)”.
Define Minimum Inhibitory Concentration
Minimum concentration of antibiotic required to inhibit growth of a bacterium in vitro
Define what is meant by “Breakpoint” and its relationship to MIC
A breakpoint is a chosen concentration of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic
If MIC is less than or equal to the susceptibility breakpoint the bacteria is considered susceptible to the antibiotic
What are the 2 types of killing by antimicrobials, pharmacokinetically speaking
Compare these with drug examples
1) Time dependent killing
- requires prolonged antibiotic presence at site of infection but NOT high concentration
- pencillins, cephalosporins, glycopeptides
2) Concentration dependent killing
- requires high antibiotic concentration at site of infection but not for long
- aminoglycosides, quinolones
Give some common antibiotics associated with the following side effects
- Hypersensitivity
- Liver problems
- Ototoxicity
- Ototoxicity
Hypersensitivity ➞ penicillans and cephalosporins
Liver problems ➞ penicillans and cephalosporins
Ototoxicity ➞ amino-glyocsides
OtotoxicityOtotoxicity➞ tetracyclines and macrolides
Give 2 purposes of therapeutic drug monitoring
To ensure adequate dose and non-toxic dose
Give 3 antibiotics which require therapeutic drug monitoring
Aminoglycosides, glycopeptides, vancomycin
What 3 things can be used to monitor potential toxicity of aminoglycosides?
renal function, auditory function and stool chart
What 3 things can be used to monitor potential toxicity of daptomycin?
creatine kinase, eosinophils and stool chart
What can we use to monitor potential toxicity of chloramphenicol?
FBC
Give 4 antibacterial-drug interactions
- Penicillans and anti-coagulants
- Sulphonureas and chloramphenicol
- Bisphosphonates and amino-glyocsides
- Cylosporin and macrolides
What are the 3 classes of antimicrobial resistance and define each
What is antimicrobial stewardship?
Healthcare system wide approach to promoting and monitoring appropriate use of antimicrobial drugs to preserve their future effectiveness.
List 4 principles of antimicrobial stewardship (DR DO)
1) Don’t start antibiotics without clinical evidence of a bacterial infection
2) Review clinical diagnosis and need for antibiotics within 48 hours from first dose and make a clear plan of action
3) Document on medical chart and in patients medical notes the clinical indication, duration or review date, route and dose
4) Obtain cultures to go from broad to narrow spectrum
Give 4 factors we must consider when choosing an antibiotic (SOSO)
- site of infection
- organisms involved
- severity of infection and/or risk of rapid progression
- spectrum of different antibiotics
- organ dysfunction- renal, hepatic
- allergies
Give 3 current hospital superbugs
1) MRSA
2) Clostridium difficile
3) Multi-resistant gram-negatives eg. Multi-resistant Pseudomonas
Give 3 current community superbugs
1) CA-MRSA
2) ESBL gram negatives
3) PVL staphloccus aures
