Antibiotics Flashcards
What do antiboitics treat?
- bacterial infections
They are widely used and misused drugs
They are made by taking natural products, fermenting them and modifiying them to chemically increase pharmalogical properties and increase antimicrobial effects
What are the princples of using antiboitics as therapeutic agents?
- Selective toxicity
- Harm microorganisms and not the host
- Driven due to the differences in structure and metabolic pathways between host and pathogen
- There is vast variation between microbes which needs to be considered
- Therapeutic margin
- Difference between active dose to treat the infection and the toxic effect
- Narrow for toxic drugs
What is microbial antagonism?
- loss of flora due to the use of antibiotics
- bacterial or pathogen overgrowth that the normal flora usually limits
eg. clostridium difficile is overproduced causing inflammation, diarrhaoea and cross-infection risks
How do you achieve bacterial clearance?
antibiotic + immunity –> bacterial clearance
If you are immunosuppressed, it requires a different route to reach bacterial clearance as you would have a weakened immune system
How do you classify antibiotics?
- target site for activity
- type of activity
- bactericidal vs bacteriostatic
- bactericidal - kill bacteria and used when the host defence mechanisms are imparied - eg. kidney infection
- bacteriostatic - inhibit bacteria and used when the host defense mechanisms are intact - infectious diseases
- spectrum of activity - broad is effective against many types vice versa
- bactericidal vs bacteriostatic
- structure
- B-lactams include penicillin and cephalosporoins
- both share B-lactam ring which is needed for the effects
- many targets within the bacterial structure for selective toxicity
- B-lactams include penicillin and cephalosporoins
Describe the B-lactam ring
B-lactams = penicillins and cephalosproins
- Both share B-lactam ring which is needed for the effects
What are the modes of action for bacterial targets for common antibodies?
What are cell wall inhibitors?
= antibiotics to treat gram positive organisms by inhibiting the bacteria cell wall
**can’t be used on gram negative organisms as the drug has to get across the peptidogylcan layer and through the pores in the periplasmic space before it can begin to inhibit the enzymes that make the peptidoglycan**
What is the action of beta-lactams of PBP in gram negative bacteria?
Beta-lactam antibotics are bactericidal and they inhibit the synthesis of peptidoglycan layer of bacterial cell walls
Beta-lactam crosses the membrane, binds to the penicillin binding proteins and then blocks peptidoglycan structure
What are the different types of penicillins?
Why do we use antibiotics?
Treatment of bacterial infections
Prophylaxis - close contacts of transmissible infections
- Prevention of infection
- Peri-operative cover for gut surgery
- People with increase susceptibility to infection
Inappropriate use - viral sore throats and patient pressure
What is the route of administration of antibiotics?
- Orally by GP
- For serious infections, in hospital, systemic treatment rapid delivery by i/v
- Topical - conjunctivitis, skin infections, burns
How do you work out the dose of antibacterial?
Concentration to achieve to get bacterial clearance
MIC = minimum inhibitory concentration
- Depends on age, weight, severity of infection and susceptibility of the organism to that antibiotic that you’ve chosen
- Make sure you achieve MIC at the site of infection
