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What is an antimicrobial drug?
a drug that kills or inhibits replication of microorganisms
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What is a "cidal" drug?
kills microorganisms
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What is a "static" drug?
prevents replication of microorganisms
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How does the patient rid himself of microorganisms if the static drug does not kill them?
the patient needs a competent immune system to finish killing off the microorganisms
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List 4 general categories of microorganisms. Do other categories exist?
bacteria, viruses, protozoa, fungi. yes, other categories exist
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Why do we care about the staining characteristics of bacteria? Name the staining characteristics in question
bacteria with similar Gram stainging characteristics tend to be susceptible to the same drugs. Gram positive and Gram negative.
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What color is a gram-positive bacterium? Name a few.
blue - staphylococcus, streptococcus, clostridium, etc
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What color is a Gram negative bacterium? Name a few
pink to red - E. Coli, Brucella, Pasteurella, Salmonella, etc
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What are you more likely to see with a light microscope - bacteria or viruses?
bacteria
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Can viruses replicate on their own, or do they have to be inside a host cell to replicate?
inside a host cell
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Does having a lipid envelope make a virus harder or easier to kill outside of the patient, with a disinfectant?
easier to kill
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List 3 kinds of protozoa.
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List 2 types of pathogenic fungi.
yeast - candida, dermatophyte - ringworm - Microsporum canis
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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
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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.
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Can all antibiotics be classified as antimicrobials?
yes
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Can all antimicrobials be classified as antibiotics?
no
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What is the goal of antimicrobial therapy?
to kill microorganisms causing disease without harming the patient
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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
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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
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Are all bacteria susceptible to all drugs?
no
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List the 2 methods of selecting an antimicrobial drug to use for a particular patient's infection.
- empirical method
- culture and sensitivity
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What is the "empirical" method of drug selection?
an educated guess by the doctor, based on experience
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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
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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
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List 2 ways to test sensitivity of a strain of bacteria to drugs.
agar diffusion test, broth dilution test
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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
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Is the MIC the same for each strain of bacteria and for each drug?
no
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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.
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Can a bacterial strain be naturally resistant to a particular drug?
yes
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Can a bacterial strain originally be susceptible to a particular drug, but develop resistance over several generations fo exposure to that drug?
unfortunately, yes
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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.
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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.
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Does inappropriate drug therapy directly cause most cases of bacterial resistance?
no - it most often selects for naturally occurring genetic changes in the bacteria
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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
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What is a "mechanism of action"?
how something works
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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
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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.
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