Antibiotics Flashcards
What are some problems with antibiotic use?
- Resistance
- C.dif
How does antibiotic resistance come about?
Antibiotics are mostly derived from micro-organisms. Therefore resistance mechanisms already exist in nature as bacteria and have been encountering antibiotics for billions of years.
Selection pressure from repeated exposure to antibiotics has greatly increased resistance.
What does emergence of resistance almost inevitably follow?
A novel agent
Why is C.dif a problem for antibiotic use?
When you kill lots of bacteria, you leave space for other bacteria, usually resistant and harder to kill.
C.dif is an eg of this, it lives harmlessly in the guts until we get rid of other bacteria, then it may cause bowel inflammation.
What does antibiotic stewardship aim to do?
- Reduce antibiotic consumption
- Restrict worst offender agents
- Promotes logical antibiotic choices
- Limits ‘co-lateral’ damage
In what ways can antibiotics be used?
- Guided therapy
- Empirical therapy
- Prophylactic therapy
Describe guided therapy?
Depends on identifying cause of infection and selecting agent based on sensitivity testing.
Used for mild infection that can wait a few days to be treated.
Can also be used to rationalise therapy for patients previously on empirical therapy.
Describe empirical therapy?
Educated guess based on clinical/epidemiological acumen.
Used when patient has more serious infection and can’t wait for culture. As delay in therapy would result in worsening of condition, this therapy is used to cover all likely causes.
Describe prophylactic therapy?
Used for healthy people exposed to surgery, injury or infected material.
Also used for immunocompromised individuals eg HIV, transplantation or splenectomy patients
This is used to prevent infection before they start
Describe some more differences between empirical and guided therapy?
Guided:-Antibiotics have narrow spectrum
- If possible they limit penetration to site of infection
- Acheive clinical cure with as little impact on colonisation and resistance as possible.
Empirical:-Antibiotics have broad spectrum
- Need to penetrate broadly throughout body
- Impact on colonisation and resistance may be greater
What are the target effects of antibiotics?
- Highly toxic to bacteria causing infection
- Penetrate body area affected by infection
- Limit release of toxins from bacteria
- Convenient administration
What do we want to achieve with an antibiotic in terms of co-lateral damage?
- Non-toxic to patient
- Limited effect on colonising bacteria to reduce resistance and c.dif issues
- Low potential for bacteria to escape treatment through developing resistance.
Can acheiving target effects and avoiding co-lateral damage be done together?
Yes, but they are often mutually exclusive so it becomes a balancing act.
In which ways can antibiotics act?
- Bactericidal
- Bacteriostatic
Describe bactericidal action of antibiotics?
Achieve sterilisation of infected site by directly killing bacteria. Also prevents growth of bacteria.
Lysis of bacteria can lead to release of toxins and inflammatory material.
