Antimicrobials Flashcards
microbobes in human body
100 trillion
weight of microbes in human body
1-3 lbs
bacterial genes and # human genes
3.3 million and
22,000
Antibiotic
low molecular substance produced by a
microorganism that inhibits or kills other microorganisms
while (ideally) causing little or no damage to itself.
Antimicrobial
any substance of natural (i.e.,
penicillin and alkaloids), semisynthetic (i.e., methicillin and
amoxicillin) or synthetic (i.e., sulfonamides and quinolones)
origin that kills or inhibits the growth of microorganisms while
(ideally) causing little or no damage to the host.
All antibiotics are antimicrobials
but not all antimicrobials are antibiotics
microorganisms drugs are active against
viruses, bacteria, fungal (antifungal/mycotic), protozoans (antiprotozoal), helminths (antihelmintic)
Classification
class and spectrum of microorganisms it effects
the biochemical pathway or target
chemical structure
***pattern of activity (type I,II,III)
Broad specturm
drugs are active against wide range * not the same as its useful therapeutic range
Narrow specturm
limited activity and primary only useful against particular species
Spectrum of activity
no antimicrobial is effective against all microbes, tetracycline have very broad spectrum, isoniazid has narrow specture
Clinical considerations before prescribing antimicrobial therapy (AMT)
be very careful, don’t guess! Culture and test, consider drug route and if effective
most effective, least toxic, narrowest spectrum, least expensive, patients immune status
ID the pathogen
collect and culture specimens, treatment should be ASAP for serious infections (Handbook of Antimicrobial Therapy HATs)
Disc diffusion test
Estimates minimal inhibitory conc (MIC) of antimicrobials
MIC is lowest conc of an antibiotic that will inhibit the growth of a bacterial stain
Broth dilution test
determines both MIC (no more turbidity) and MBC (minimum bactericidal conc) no more bacterial growth
Bactericidal antibiotics usually have very similar MIC and MBC values
Bacteristatic antibiotics have much higher (if any) MBC than MIC values.
Prophylactic
no infection
Definitive
pathogen isolated
Pharmacokinetics
absorption, distribution, metabolism, and excretion of drug
dosing regimen
serum conc
Pharmacodynamics
he relationship of the drug concentration at the site of action and the resulting effects, including the time course and intensity of therapeutic and adverse effects.
conc in tissues and body fluids
- pharm and toxic effects
conc at infection site
- antimicrobial effect
choosing a dose regimen
Must keep in mind that although MIC is compared to plasma
concentrations, these concentrations may or may not reflect drug concentration at site of infection.
want OVERKILL without causing toxicity
Goals in dose regimen
GOAL #1: achieve a bactericidal concentration at the site.
GOAL #2: discourage emergence of resistant bacteria.
Growth curve
log phase of bacterial growth is the most sensitive to antimicrobial intervention, want to target this
Bacteriacidal vs Bacteriostatic drug growth curve
bacteriostatic plateaus and will increase if Rx stopped
bactericidal decreases log # of bacteria
Bactericidal antibiotics kill bacteria, while bacteriostatic antibiotics stop bacteria from growing or reproducing.
body still plays a role in removing last bit
Antimicrobial Patterns
pharmacodynamic properties:
conc-dependence (I)
time-dependence (II)
time-dependence with persistent effects (III)
Rate of effect determined by II and III
