Principles of the treatment of infections Flashcards
What are the 3 factors that need to be considered when deciding which antibiotic to prescribe?
1) bacteria causing the infection
2) patient
3) antimicrobial itself
What are the criteria in which the treatment is decided?
clinical investigations - imaging techniques may be useful (e.g. CXR)
the information the patient gives
laboratory evaluations - some infections have obvious signs that indicate causative agent and where site of infection is
What can be useful in terms of thinking about what a patient could have been exposed to?
public health data and trend in infectious agents can be an indication of what the patient is most likely to have been exposed to recently
How can laboratory investigations be obtained?
Lumbar puncture- testing of CSF in illnesses such as bacterial meningitis
wound or throat swabs
What is sensitivity testing?
process of working out the level of resistance an organism may have to potential treatments
How is sensitivity testing assessed?
minimum inhibitory concentration (MIC)
- measured in mg/L is the dilution of antibiotics that just prevents growth - therefore at MIC treatment is effective
What is the difference between bactericidal and bacteriostatic?
if a drug is bactericidal the bacterial burden will decrease rapidly
if not in bacteriostatic drugs the bacterial burden is held constant and the immune system destroys the bacteria
When is bactericidal action required?
critical conditions - such as endocarditis, sepsis and meningitis
Other than the speed of action of the drug what is anther limitation of the drugs?
sensitivity of the drug target - determined by the presence or absence of the correct drug binding protein on the microorganism
What are the different ways drugs interact?
1) synergism is where the combined effect of both drugs is greater than one alone
2) antagonism is where the combined effect is less e.g. penicillin and chloramphenicol
3) indifference is where each drug is no better alone or together
What is another limitation of antimicrobials?
occurrence of adverse effects e.g. penicillin hypersensitivity, gentamicin nephrotoxicity
What are the different routes of administration of antimicrobials?
topical, oral, intravenous and intramuscular
- important as it will affect the volume of distribution of the drug and therefore impact rate of elimination
What must the drug be above to be effective?
must be above the MIC - drugs with longer half lives = more likely to have a higher area under the curve
Why is calculating the drug half life?
important in order to work out dose intervals, keeping the drug at a steady level in the blood, this elimination may be affected by renal disease
What is necessary before surgery?
one undergoes a course of prophylactic antibiotics to reduce surgical site infection - most commonly due to s.aureus, coagulase negative staphylococci, enterococcus and e.coli
- increasing proportions are caused by antimicrobial resistant bacteria
