Antibaterials Flashcards
What is the unique proptery of antimicrobials
Antimicrobials target microbial biochemistry
The ideal antimicrobial would have no direct impact on patient biochemistry or physiology
How do antibiotics work?
Antibiotics work by sticking to specific bacterial molecules, interfering with their shape and consequently their function
- For example, penicillin binds to DD- transpeptidase, a bacterial protein that is vital for making the outer cell wall of bacteria.
- As a result of penicillin’s action, the cell wall is weakened and the bacteria burst
Which antibiotics act on dna synthesis
Quinolones ciprofloxacin
Folic acid
antagonists trimethoprim
sulphonamides
Which antibiotics act on protein synthesis
Ere witht ribosome and hence rotein synthesis.- downstream affects metabolic pathwaysInternet
Aminoglycosides gentamicin
Macrolides erythromicin
Tetracyclines
Which antibiotics act on cell wall synthesis
Beta-lactams
penicillins cephalosporins carbapenems
Glycopeptides vancomycin
What a re the. Reasons for antibiotics
Prevention of infections, therapy of significant bacterial infections
Who is at risk of nection
People at increased risk of infection • Peri-operative – Prevention of surgical site infections Dont need repeat coursed for prophylaxis in surgical site. Except cardiac. But vast majority - usually single dose. Don’t need more once wound closed up. OR if very prolonged srgery also may need repeat courses • Short term – Meningitis contacts • Long term – Asplenia – Immunodeficiency
Describe therapy o significant bacterial infections
- Empirical treatment of suspected infection
* Treatment of culture proven infection
How can antibiotics be used empirically
1) follow the local guidelines
2) what is the cause? Which antibiotics are likely to be effective?
Which is the best choice?
What does the likely cause depend on?
Duration of illness, pmh, occupational history, travel history, time of year, age, personal big, anatomical site
What does the antibiotic that is likely o be effective depend on
Community or hathcare onset? Severity of infection? Baseline rate of resistance? Immune status of patient
What are factors whicheffect which antibiotic is the bets choice
Cost, efficacy, age, toxicity, ddis, allergies, pregnancy, breast feedin, organ function, administration route
How is susceptiby of bacteria tested
Disc testing
What is mic
MIC measurements are for a specific organism and antibacterial combination
e.g.
MIC of Streptococcus sanguinis to benzylpen
What is judicious antibiotic therapy
S
What is i time dependent killing
– Succesful treatment requires prolonged antibiotic presence at site of infection
– But not high concentration
– fT>MIC fraction of time concentration of unbound drug is greater than MIc
What is pharmacodynamics
Concentration dependent killing
– Succesful treatment requires high antibiotic concentration at site of infection
– But not for long
– [Cmax]/MIC ratio of maximum unbound drug concentration to MIC
What is therapeutic drug monitoring
• To ensure
– Adequate dose – Non-toxic dose
• Aminoglycosides • Vancomycin
What is innate vs acquired resistance
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
INNATE RESISTANCE
• When this has never been the case for a specific bacteria- antibiotic combination, then the bacteria is innately resistant
ACQUIRED RESISTANCE
• If a bacteria was previously sensitive to an antibiotic but is now resistant, then the bacteria has acquired resistance
What are the 2 main ways in which bacteria become reisisnct
Bacteria develop resistance to antibiotics in two main ways:
• mutation of their DNA
• acquisition of pre-formed resistance genes
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Wat are the diverse effects of antibiotics
- Organ toxicity
- Allergicreactions
- Idiosyncratic reactions
