Antibiotics Flashcards
(32 cards)
How do antibiotics work
Stick to specific bacterial molecules
Interfere with shape and consequently their function
How does penicillin work - what does it bind to ?
DD-transpeptidase (bacterial protein vital for making the outer cell wall of bacteria )
= cell wall weakens, bacteria burst
Label parts of bacterium
IPAD IMAGE
Which class of antibiotics affect DNA synthesis
- Quinolones
- Folic acid antagonists
Give an example of a quinolone
Ciprofloxacin
Give 2 examples of folic acid antagonists
- trimethoprim
- sulphonamides
(E.g Co-trimoxazole = sulfamethoxazole which is a sulphonamide plus trimethoprim )
Give 3 classes of antibiotics that affect protein synthesis
- aminoglycosides
- macrolides
- tetracyclines
Give an example of an aminoglycoside
Gentamicin
Give an example of a macrolide
Erythromicin
Give an example of a tetracycline
Doxycycline
Give 2 classes of antibiotics that affect cell wall synthesis
- Beta-lactams
- Glycopeptides
Give 3 examples of Beta-lactams
- penicillins
- cephalosporins
- carbapenems
Give 2 examples of a glycopeptides
- vancomycin
- teicoplanin
What are 2 reasons for giving antibiotics
- prophylaxis of bacterial infections
- therapy of significant bacterial infections
Give 3 examples of people at increased risk of infection
• Peri-operative
– Prevention of surgical site infections
• Short term
– Meningitis contacts
• Long term
– Asplenia
– Immunodeficiency
Factors to consider when thinking of the likely organism
- anatomical site
- duration of illness
- personal background
- age
- time of year
- past medical history
- occupational history
- travel history
What to consider when thinking which antibiotics are likely to be effective
- community or healthcare onset ?
- severity ?
- immune status of patient
- baseline rate of resistance
What to consider when thinking which antibiotics is best choice
- efficacy
- safety
- age
- toxicity
- drug interactions
- allergies
- administration route
- organ function
- pregnancy, breast feeding
- cost
A way of measuring antibiotics activity
Disc sensitivity testing
- antibacterial disc
- agar plate is seeded with test bacterium
- antibacterial diffuses though agar
- overnight intubation… zone of inhibition of bacteria growth
- bigger zone of inhibition means bacteria is more susceptible to the antibiotic
What is minimum inhibitory concentrations
Lowest concentration of an antimicrobial that will inhibit visible growth of microbe
Pharmacodynamics
Time dependent killing
- successful treatment requires prolonged antibiotic presence at site of infection
- not high conc
- fT>MIC : fraction of time concentration of unbound drug is greater than MIC
What is concentration dependent killing
- successful treatment requires high antibiotic conc at site of infection
- but not for long
- [Cmax] / MIC ratio of unbound drug conc to MIC
What is bacterial resistance
Antibiotics can only work if the antibiotic can bind to the bacterial
target molecule.
The bacterial molecule must be present, accessible and a fit for
the antibiotic
What is innate resistance
When this has never been the case for a specific bacteria- antibiotic combination, then the bacteria is innately resistant
