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AOD - Antimicrobials (exam 2)
Terms in this set (66)
Broad goal of chemotherapy
5 goals of chemotherapy
Achieve an adequate concentration (1) of an appropriate drug (2) at the site of infection (3) for a sufficient length of time such that the targeted cells or organisms are eliminated.
To accomplish the aim above without (4) producing adverse effects in the patient or (5) promoting drug resistance in the targeted, disease-causing cells
Drugs work together w/ host immunity to...
Reduce pathogen numbers at infection sites
Host immunity to clear a pathogen
Common mechanisms of chemotherapeutics
Interfere w/ metabolism
Denature generic apparatus
Interfere w/ protein synthesis & replication
Compromise pathogen barriers
Interfere w/ neural or muscular functions
Arrest cell growth --> decrease rate of pathogen population expansion
Kill pathogens --> reduce pathogen population
Minimum inhibitory concentration (MIC)
Lowest drug concentration that completely inhibits visible microbial growth in a bacterial isolate after an overnight incubation
The MIC value is a measure of...
Minimum bactericidal concentration (MBC)
Lowest drug concentration required to kill a pathogen. At the MBC, the microbial population grown on a plate is reduced by 99.9% (3 log units, relative to #s in the starting inoculum)
In order for a drug to be considered bacteriostatic...
MBC/MIC must be greater than 4
In order for a drug to be considered bactericidal...
MBC/MIC must be less than or equal to 4
A desirable chemotherapeutic drug targets..
Unique characteristics of a pathogen & has a high margin of safety in the host
A drug's therapeutic window is determined by the...
Degree of drug toxicity in the target organism relative to host cells
Methods of drug resistance used by pathogens
Drug inactivation, pumping the drug out of the cell, altering the drug target
Traits of a drug-sensitive infection
Effective drug concentration in serum & tissues is safe for the host
Drug dosing regimen is sufficient to produce desired therapeutic outcome
Traits of a drug-resistant infection
Drug concentrations needed to effectively inhibit growth or kill the pathogen may be unsafe or toxic for the host
Father of chemotherapy
With drug-resistant organisms, the drug's dose-therapeutic effect curve shifts...
Right, w/ no change in the dose-adverse effect curve
Prophylactic & metaphylactic (pre-emptive) treatment
Used to prevent or limit a subclinical infection, but w/ increased risk of drug resistance
Empirical drug treatment
Drug selection & dosing are based on presumed pathogen(s) involved in common body sites. Narrow spectrum drugs should be chosen that will reach high concentrations at the infection site
Definitive drug treatment
Rational drug choice & dosing based on defined pathogen isolate(s). Initial samples should be collected before drug treatment <-- seems obvious but it was in the notes so now it's on here.
Drugs in food-producing animals
Drug therapy must adhere to state & federal guidelines. Only certain drugs, given in approved doses by approved routes can be given.
It is best to know the causative organisms through ___ testing of sample isolates before treatment
Culture & sensitivity
Condition of reduced body functions. Can be due to hibernation or estivation. Some parasites undergo hypobiosis w/ their hosts or w/n actively metabolizing hosts
What the hell is estivation?
It's hibernating in hot weather.
I want to learn how to do that. I hate summer.
MOST IMPORTANT THING TO REMEMBER in shouty caps and featuring a picture of a cute dog and a not cute (yeah, I discriminate against helminths, deal with it)
Worms & arthropods are eukaryotic like their host friends
Anthelmentics (against worms & flukes)
Insecticides against arthropods
Active against internal AND external parasites. Magical.
Goal for both small & large animal patients
Chemotherapy should remove 95% or more of the parasites (FDA requirement) w/o causing toxicity
Methods by which anti-parasitic drugs help get rid of protozoa
Inhibit replication or change protozoal metabolism
Methods by which anti-parasitic drugs help to get rid of worms or arthropods
Inhibit replication, change parasite metabolism, disrupt the nervous system, degrade parasite defenses
Apparent reason that we want our pets to be clear of parasites
Because of potential zoonoses.
I thought we didn't want them to have parasites because that sucks for them and we care about their welfare, but I'm glad this course will correct my misunderstanding and show me that it's really for purely selfish reasons.
Reasons we want large animals to be clear of parasites
Again, NO MENTION OF THEIR WELL-BEING?
Minimize subclinical disease (okay, that's kind of their well-being), prevent pasture buildup of worms, minimize drug resistance
When host is no longer able to compensate for parasitic load & animal is showing overt signs of disease
Animal is not showing overt signs of disease, but there are subtle cues of parasitism
Clinical signs of parasitism
Anemia, poor hair coat, bottle jaw, jaundice, diarrhea
Clinical signs of sub-clinical parasitism
Reduced weight gain, decreased milk production, reproductive performance, & weaning weight, increased susceptibility to other diseases
Ways to minimize pasture buildup of worms
Strategic dewormings; before turning out in the spring & before putting on a rested pasture
Ideal anti-parasitic drug application
High convenience, low frequency
Ideal anti-parasitic drug cost
Low cost per treatment
This is obvious but just in case anyone really likes spending all their money, this is to clarify that most people do not. Although ramen is delicious.
Ideal anti-parasitic drug safety
Environmentally friendly, high handler safety
Ideal anti-parasitic drug toxicity
Minimal adverse effects, no genotoxicity or teratogenicity
Ideal anti-parasitic drug efficacy
High worm count reduction & egg count reduction
Ideal anti-parasitic drug activity
Broad spectrum of parasites, all disease-relevant development stages
Ideal anti-parasitic drug for livestock
Does not affect food quality, no tissue residues, short withdrawal time
Examples of short-acting anthelminthics
Benzamidazoles (albendazole, fenbendazole, oxfendazole)
Imidazothiazoles/tetrahydropyrimidines (levamisole - Levasole, Tramisole, pyrantel, & morantel)
Advantages of short-acting anthelminthics
Cheaper, kill at that moment in time
Disadvantages of short-acting anthelminthics
Not efficacious to hypobiotic worms (larvae having a snooze in the tissues)
Longer-acting anthelminthics work for...
Can longer-acting anthelmenthics target hypobiotic worms?
Aw yis, they don't discriminate and let sleeping worms lie
Longer-acting anthelminthic examples
Drug resistance is more frequently due to changes in ____ than appearance of new ones
90-95% of infective larvae/eggs live on...
Clinical definition of drug resistance
<90-95% reduction when the normal therapeutic dose is used
How do we measure drug resistance in helminths?
Use quantitative fecal examination to perform a fecal egg count reduction test
Principles of fecal egg count reduction tests
Performed during transmission season
Collect at minimum of 2 time points
Pre-treatment sample: use 20 random fecal samples
Post-treatment sample: 10-14 days after pre-treatment, 20 more random fecals are collected
Systems used for fecal egg count reduction test
Wisconsin or McMaster's
Fecal egg count reduction equation
Efficacy = (pre-treatment epg - post-treatment epg) / pre-treatment epg
Then to get the percentage, multiply it by 100, but I got tired of trying to make math look pretty on quizlet.
Less than ___ efficacy is considered possible resistance for the drug used
Reasons for resistance in bacterial & parasitic communities
Deworming too frequently
Use antibiotics inappropriately or too frequently
Rely on a single compound
Use the compound for inappropriate duration
Failure to achieve adequate drug concentrations at infection sites
Methods by which bacteria acquire resistance
Conjugation, transformation, transduction, or mutation
Example of endectocides
Examples of bacteriostatic drugs
Chloramphenicol, erythromycin, clindamycin, sulfonamides, trimethoprim, tetracyclines
Examples of bactericidal drugs
Aminoglycosides, beta-lactams, vancomycin, quinolones, rifampin, metronidazole