Flashcards in Antibiotics 1 Deck (22):
What is virulence?
the ability of a bacterial cell to invoke an infection
What is antimicrobial pharmacodynamics?
the relationship of drug concentration to its anti-microbial effects
What is antimicrobial pharmacokinetics?
- drug absorption
- elimination from the body
When are oral drugs appropriate to treat the bacterial infection?
- chosen for infections that are mild and can be treated on an outpatient basis
When are IV drugs appropriate to treat a bacterial infection?
- chosen for the most serious infections (vancomycin is poorly absorbed by the intestine)
What patient factors must be taken into consideration when choosing an antibiotic?
- immune system (if a patient has a weakened IS, we want to tx more aggressively)
- renal function(can the kidney excrete it)
- hepatic function(can the liver metabolize it)
- poor perfusion (will it reach the target site)
- age (elderly and young have weakened IS)
What is empiric therapy?
choosing the antibiotic based on patient symptoms- only suspect that the bacterial infection is present, and we want to treat aggressively
What is directed therapy?
when we know what the bacteria causing the infection is, we can pick an antibiotic that directly targets the bacteria
When would you choose to use empiric therapy to treat an infection?
- in the case of a polymicrobial infection (can pick a broad spectrum Ab)
- severe headache, rigid neck, sensitivity to bright lights- suspect meningitis so we want to treat aggressively based on those symptoms
- low levels of neutrophils (neutropenia)
- hospital infections (hospitals know what kind of infections are going around in the hospital- so practitioners will tx based on this)
- age (want to treat young and old aggressively)
What are 3 cases that we use antimicrobials for?
1. prophylaxis - high risk so we want to dose them anyway
2. Therapy - want to kill bacteria (most common)
3. Suppression - do not want to kill all of the bacteria in the patients body, just want to suppress growth. Want to keep the infection localized and from becoming systemic
What does bactericidal mean?
- kills bacteria at concentrations achievable in the patient (bacterial number rapidly declines)
What does bacteriostatic mean?
- stops the growth and replication of organisms, limiting the spread of the infection (bacterial numbers plateau)
What is seen with concentration dependent killing?
- a significant increase in the rate of bacterial killing with higher concentrations of the drug
- useful property for rapid killing of infective pathogens
What is seen with time-dependent killing?
- require time to achieve effective killing
- higher concentration of the drug do not increase the rate of bacterial killing (increase in time, more bacteria is killed)
What do narrow spectrum antimicrobial agents cover? What is an example of this?
- act on a limited group of microorganisms
- isoniazid is an example- acts on mycobacteria
What does extended spectrum antimicrobial agents cover? What is an example of this?
- effective against 1 class of organisms as well as a significant number in a different class
- an example of this is ampicillin
What does broad spectrum antimicrobials cover? What is an example of this?
- acts to kill a range of antimicrobial species
- tetracycline is an example, and can be used to treat a polymicrobial infection
When would you use an antimicrobial combination?
- for an unknown organism
- a polymicrobial infection
- antibiotic synergy
- for certain patient/population factors
- used when it is known in the hospital
- also used in the case of dose related toxicity
What are the disadvantages of antimicrobial combinations?
- eradication of normal microflora
- resistance (MDR organisms)
- adverse effects (greater toxicity)
- patient adherence to therapy
- increased cost
What is synergism?
when the effect of 2 drugs in combination is greater than the sum of the effect when 2 drugs are administered independently
What is antagonism?
when the effect of 2 drugs in combination is less than the sum of the effect when 2 drugs are administered independently