What do we mean when we say that an antimicrobial drug has a "broad spectrum" or a "narrow spectrum"?
broad spectrum: affects a wide range of microorganisms
narrow spectrum: affects only a few types of microorganisms
What is the difference between an antibiotic, and antibacterial, and an antimicrobial?
an antibiotic is a substance produced by a microorganism that kills or inhibits growth of other microoganisms
an antibacterial is a substance that kills or inhibits growth off bacteria that is synthetic or produced by microbes
an antimicrobial is a substance that kills or inhibits growth of microoganisms. broadest category.
Can all antibiotics be classified as antimicrobials?
Can all antimicrobials be classified as antibiotics?
What is the goal of antimicrobial therapy?
to kill microorganisms causing disease without harming the patient
What 3 conditions must be met in order to achieve this goal?
the microbe must be susceptible to the drug, the drug must get to the site of infection at the proper concentration to affect the microbe, and the patient must be able to tolerate this drug concentration
What is "bacterial susceptibility?
when a particular strain of bacteria is susceptible to a particular drug, it means that the bacteria can be killed or inhibited by that drug
Are all bacteria susceptible to all drugs?
List the 2 methods of selecting an antimicrobial drug to use for a particular patient's infection.
culture and sensitivity
What is the "empirical" method of drug selection?
an educated guess by the doctor, based on experience
What is "culture & sensitivity" (C&S)?
taking a sample of the microorganism causing the infection, growing it, identifying the strain of microorganism, and determining which drug is specifically best for that strain of microorganism
Which method takes the most time, money, and effect - empirical or C&S? Which gives the mest results?
C&S - it also gives the best results
List 2 ways to test sensitivity of a strain of bacteria to drugs.
agar diffusion test, broth dilution test
The broth dilution test will give us the MIC of a particular drug to a particular strain of bacteria. What does "MIC" mean?
minimum inhibitory concentration - the lowest drug concentration that inhibits bacterial growth
Is the MIC the same for each strain of bacteria and for each drug?
What is "bacterial resistance"?
resistance of a particular strain of bacteria to a particular drug means that that strain of bacteria is not affected by that drug at a level that the patient can tolerate.
Can a bacterial strain be naturally resistant to a particular drug?
Can a bacterial strain originally be susceptible to a particular drug, but develop resistance over several generations fo exposure to that drug?
What is "inappropriate drug therapy"?
the drug is not given in the proper way, which speeds up the rate at which bacteria develop resistance to that drug.
List 4 kinds of inappropriate drug therapy.
dose not high enoug, drug not given long enough, drug given by wrong route of administration, low level long term antimicrobials in livestock feed. all of these result in drug levels that are not adequate to kill all of the microorganisms.
Does inappropriate drug therapy directly cause most cases of bacterial resistance?
no - it most often selects for naturally occurring genetic changes in the bacteria
How does inappropriate drug therapy select for and speed upt he development of resistant strains of bacteria?
"survival of the fittest" - the weaker bacteria are killed off, and the stronger, harder bacteria live to reproduce
What is a "mechanism of action"?
how something works
List 5 mechanisms of action of drugs against microorganisms
inhibit cell wall formation, damage cell membrane, block protein synthesis, interfere with metabolism, interfere with DNA or RNA
What is a drug residue in food? Can drug residues usually be destroyed by cooking?
detectable amount of drug in meat, milk, or eggs. no - usually cannot be destoyed by cooking.