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Antiviral drugs work by being... |
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Definition
analogs of components of viral DNA or RNA |
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Acyclovir and AZT (azidothymidine) are nucleotide analogs in treatment of |
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HIV Acyclovir treats Herpes virus |
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When nucleotide analogs become incorporated into the pathogen’s DNA: |
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Distorts the shape of pathogen’s DNA and RNA Which prevents replication, transcription, or translation |
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Nucleotide analogs make potent antiviral and anticancer drugs because… |
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Viruses and cancer cells typically replicate faster than normal cells. |
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Viruses are _______ more likely to incorporate an analog into the viral DNA or viral RNA than host the cell. |
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The number of different kinds of pathogens a drug acts against |
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Diffusion susceptibility test AKA... |
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Diffusion susceptibility test procedure |
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Definition
1. Uniformly inoculate Petri plate w/pathogen 2. Small disks of drugs are firmly arranged on the plate 3. Plate is incubated for _____ hours and examined 4. Plates are examined for zones of inhibition 5. Larger the zone of inhibition = more effective drug |
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Researchers classify drugs as: |
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Susceptible, Intermediate, Resistant to each drug |
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Diffusion Susceptibility Test tells us: |
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1. Which drug is the drug of choice. 2. Which drug is the microbe most susceptible to. |
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Definition
lowest dosage of that the drug of choice will most be effective |
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Definition
Series of dilutions of the drug of choice is place in nutrient broth Standard amount of bacteria is added to each broth tube. After incubation, clear broth indicates that bacteria were either inhibited or killed |
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determines the dosage of the drug to be an effective bacteriocidal. |
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MBC Samples are taken from and transferred to: |
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clear MIC tubes or zones of inhibition of Diffusion Susceptibility Test = Kirby Bauer, to plates containing a drug-free growth medium |
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Term
Any growth of bacterial colonies on a MBC plate indicates that concentration of antimicrobial drug is… |
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Definition
Only bacteriostatic not bactericidal |
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Term
List routes of drug administration: |
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Topical or Local Orally Intramuscularly (IM) Intravenously (IV) |
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Definition
Application of drug if infection is external |
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Definition
Lower drug concentrations No reliance on health care provider Patients do not always follow prescribing information Patients may quit taking the drug |
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Definition
Requires needle for administration Some patients refuse shots Reaches a higher drug concentration faster than oral administration Drug concentration diminishes as liver and kidneys remove drug from circulation Concentration never as high as IV administration |
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Definition
Requires needle or catheter Drug in blood is initially very high drug concentration Remains high, constant delivery |
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What are three main categories of side effects? |
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Definition
Toxicity Allergies Disruption of normal microbiota |
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Definition
Ideally antimicrobials drugs are toxic to pathogens and harmless to humans; however many drugs have toxic side effects Exact cause of many adverse reactions poorly understood Many Drugs may be toxic to kidneys, liver, or nerves |
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Flagyl may cause a harmless temporary condition called |
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Toxicity in pregnant women causes: |
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side effects to the fetus (accutane) |
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Allergies: Some drugs trigger allergic: |
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Definition
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Although allergic reactions are rare, they may be: |
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life threatening and may cause Anaphylactic shock |
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.1% of Americans have anaphylactic reactions to: |
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Definition
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Disruption of Normal Microbiota/Flora |
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Definition
May allow opportunistic pathogens to increase and result in secondary infections |
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Long term use of broad spectrum antimicrobials often result in: |
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Definition
explosion of overgrowth of normal flora: Candida albicans |
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Term
Candida albicans of the vagina and mouth: |
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Definition
causes vaginitis yeast infection and thrush after long term |
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Term
Superinfections or multiplication example: |
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Definition
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Clostridium difficile normally resides ______ is held in check by _________. |
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Definition
in the colon; normal microbiotica/normal flora |
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If normal flora is destroyed by long term treatment of antibiotics; C. difficle can multiply and causes a potentially fatal condition called: |
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Definition
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Secondary infections like C. difficile are of greatest concern for hospitalized patients that are already: |
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Definition
immumocompromised and exposed to resistant pathogens |
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Not all microbes of the _________ are equally sensitive to a given drug |
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Definition
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Definition
naturally partially or completely resistant to a given drug |
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In the absence of antimicrobial agents, the resistant (mutant) cells are: |
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Definition
in the minority and usually less efficient than normal cells |
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When antimicrobial agent is present, sensitive cells are _______ while the resistant cells |
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Definition
inhibited or die continue to grow |
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Resistant cells then replace: |
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sensitive cells as the majority in the population |
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Antimicrobials do not produce: |
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Definition
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Bacteria can acquire resistance in 2 ways: |
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Definition
1. New mutations of chromosomal genes 2. Acquisition of R-plasmids via transformation, transduction, and conjugation |
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What are 5 ways bacteria develop resistance? |
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Definition
1. Can mutate their DNA to produce enzymes 2. Can mutate their DNA to alter the shape of proteins called porins 3. Can alter receptors that so that drug can no longer attach to it or drug binds less effectively to microbe 4. Can alter their metabolic pathways that the drug targets 5. Pump the drug out of the cell before the drug can act |
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Term
Resistant Microbes mutate their DNA to produce enzymes such as beta-lactamase (Penicillinases enzyme) that destroys (it opens the B-latam ring) or deactivates the beta-lactam of drug- ex: |
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Definition
Penicillinases enzyme renders penicillin inactive (MRSA) |
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Term
Resistant Microbes mutate their DNA to alter the shape of proteins called porins in microbe’s cell membrane- ex: |
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Definition
These mutated porin slows or prevents entry of drug into the cell. Mutated porins give bacteria resistant to penicillin and tetraclycine |
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Resistant Microbes alter receptors that so that drug can no longer attach to it or drug binds less effectively to microbe - ex: |
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Definition
(HIV and Trypanosoma brucei alter their receptors through mutation) |
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Resistant Microbes alter their metabolic pathways that the drug targets- ex: |
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Definition
Example: Resistance against Sulfa Drugs 1. Produce more PABA 2. Resistant microbes abandon synthesis of folic acid and absorb it from the environment |
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Antimicrobials facilitate replication of resistant cell that were: |
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Definition
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What is Multiple Resistance? |
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Definition
Pathogen can fight off to more than one drug at a time Especially when different R-plasmids are exchanged |
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Multi-resistant strains of bacteria develop in: |
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Definition
Hospitals and nursing homes, where the constant use of many kinds drugs eliminates sensitive cells and allows the growth of resistant strains |
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What is Cross Resistance? |
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Definition
When one antimicrobial agent can fight more than one drugs Especially when drugs have similar structures |
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Examples of Cross Resistance |
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Definition
Streptomycin, Neomycin, Gentamicin, Kanamycin |
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Multiple Resistance and Cross Resistance create: |
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pathogens that are resistant to many drugs |
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Definition
Staphylococcus, Streptococcus, Enterococcus, Pseudomonas, Plasmodium |
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Four ways to Retard the Develop of Resistance: |
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Definition
High concentrations of drug maintained in patient for long enough time to kill all the pathogen’s sensitive cells and inhibit resistant cells long enough for immune system to destroy them. Use a combination of antimicrobial agents so that pathogens resistant to one drug will be killed by another drug Limit use of antimicrobials to necessary cases Develop new variations of existing drugs to resistant strains Second-generation drugs then Third-generation |
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Definition
one drug enhances the effect of a second drug Example: Penicillin and streptomycin |
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Penicillin inhibits the formation of the: |
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Definition
cell wall and makes it easier for streptomycin to get inside the pathogen and interfere with protein synthesis |
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Term
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Definition
drugs that interfere with each other Example: Drugs that slow bacterial growth are antagonistic to drugs that act only against growing and dividing cells |
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