Antibiotics Flashcards
What was the first AB discovered and how?
Penicillin was the first AB discovered when Alexander Fleming had his S.Aureus culture contaminated with Penicillium Notatum. Penicillin in the agar caused lysis of S.Aureus.
Why may immunosuppressed not respond to ABs? Give examples of people considered immunosuppressed
Antibiotic + Immunity → Bacterial Clearance
- Due to this immunosuppressed individuals may not respond to AB treatment
- This includes Babies, Elderly, HIV+, Cancer Treatment, Transplant Recipient and Diabetics
- Also neutropenia, asplenia, renal disease, diabetes, alcoholism
What are ABs made of?
Natural products of fungi and bacteria - natural antagonism and selective advantage, kills or inhibits growth of other microbes.
Most are semi synthetic as they are derived from the products but chemically modified to increase their pharm properties and effect.
Some are completely synthetic e.g. sulphonamides.
When do we use ABs?
Treatment of bac infections. Prophylaxis for close contacts of transmissible disease e.g. in peri operative cover for gut surgery, also given to those with increased susceptibility for infection
List the factors that make a good antibiotic
Selective toxicity, good killing activity, slow emergence of resistance, narrow spec of activity, non toxic to host (TI), long plasma half life, multiple dosing forms (IV, IM, PO, topical), no interaction with other drugs
What determines the dosage for a patient? What must we consider?
This will depend on patient factors: Weight, Renal Function, Age and Liver Function, Severity of Infection
As kidney or liver will get rid of the AB
Also depends on the Susceptibility of the Organism causing infection
It also depends on the pharmacodynamic properties of the antibiotic i.e. which determine if we can give a concentration higher that the MIC
What are the two pharmacodynamic properties of ABs?
The pharmacodynamic properties of ABs that describe killing activity are:
- Time-Dependence which is the time spent over the MIC ? idk
- Concentration-Dependence which is the Area Under Concentration (AUC) that is above the MIC?
What is stage 1 of AB therapy?
Stage 1 - Day 0 -2: patient is unstable due to infection, we are unaware of site and pathogen so prescribe empirically with parenteral broad spectrum drugs
What is stage 2 of therapy?
Day 2 - 7: patient now stabilising, now know the pathogen and site so now change therapy so more efficient so parenteral monotherapy or oral narrow spec drugs depending on stability improvement of pt
What is stage 3 of therapy?
Day 7 - 10: patient stable, now start oral ABs
Factors that affect drug-host-microbe
Who decides which AB to give, and how decide?
This is decided by Specialists, Medical Microbiologists and Local Policies.
Depends on drug characteristics.
Depends on how drug distributes in body - must be similar to bacteria distribution: - Some drugs aren’t absorbed from gut (but useful for treat gut infection), dont cross the BB barrier, don’t penetrate abscess, some drugs accumulate inside cells.
Also depends on drug characteristics
What factors must we consider when deciding which AB to give a patient?
Spectrum of activity - Cidal vs Static, Toxicity, Excretion, Patient Age - Renal Capacity, Route of Administration - Oral / i.v / i.m / Topical, Clinical Condition, Type of Bacteria, Sensitivity of Bacteria - Resistance? / Which MOA, Cost
When do we give combinations of ABs?
Before an organism is identified in life-threatening conditions
To give less toxic doses to an individual as possible
Polymicrobial Infections such as in GI Perforations where there may be both Aerobes and Anaerobes which require different treatments
Some ABs work in Synergy with one another such as:
Penicillin and Gentamycin
Why may AB therapy not work/failure?
Issue with drugs, host, bacteria and/or lab
