Antimicrobials- L2 Flashcards
What are antimicrobials?
Drugs that destroy microbes, prevent their multiplication or growth, or prevent their pathogenic effect.
What needs to be known to treat a bacterial infection?
location, likely pathogens involved, which antimicrobials are likely to be effective for the pathogen at the particular site.
What other factors need to be considered for antimicrobial therapy?
Cost, safety, ease of use, and possible resistance
Who and when was penicillin discovered
Alexander Fleming 1928
What is an Antibiotic?
A chemical substance produced by a microorganism that inhibits the growth of or kills other microorganisms.
What is an Antimicrobial agent?
a chemical substance derived from a biological source or produced by chemical synthesis that kills or inhibits the growth of microorganisms.
These antimicrobials are produced by bacteria or fungus.
streptomycin, penicillin, tetracycline
Natural (true Antibiotic)
Semi-Synthetic antimicrobials are what?
Chemically-altered natural compound
ampicillin, amikacin
What are synthetic antimicrobials?
Chemically designed in the lab
sulfonamides, enrofloxacin, marbofloxacin
What are the classifications of Antimicrobial agents?
Chemical Family Structure
Mode of Action
Type of Antimicrobial activity
Spectrum of Antibacterial Activity
What does the clinician need to know to treat with antimicrobials?
The drugs,
The microbiology
The Patient
What are the modes of action?
inhibitors of cell wall synthesis inhibitors of protein synthesis inhibitors of membrane function inhibitors of nucleic acid synthesis (Anti-metabolites)
What are the two types of Antibacterial Susceptibility Testing?
1 Dilution (Broth/Agar) 2 Diffusion (Disk)
What is a susceptibility break point?
a drug concentration above which an organism is considered resistant and at or below this value organism is susceptible to that drug.
what are the three break point values?
Susceptible, Intermediate, and Resistant
What is Minimum inhibitory concentration (MIC)?
Minimum amount of drug required to inhibit bacterial growth.
Drugs with _____ MIC values are better choices to use.
Lower
What is the likelihood of therapeutic success with a susceptible rating?
High
what is the likelihood of therapeutic success with an Intermediate rating?
UNCERTAIN
what is the likelihood of therapeutic success with a resistant rating?
none, High likelihood of therapeutic failure
what is kirby bauer disk diffusion?
A bacterial isolate from pure culture spread on agar plate. single concentration Antimicrobial disks are added to the plate and the diameter of growth inhibition is measured.
Is kirby Bauer disk diffusion accurate for MIC?
NO
What is Broth dilution?
Multiple dilutions of antimicrobial agents, measure and report growth inhibition endpoint (MIC).
Gradient Diffusion or E-test
Agar plate with strips of Antimicrobial agents with varying concentrations ranging from high to low from outside of plate to the middle of the plate.
What are broad spectrum antibiotics?
Antibiotics that are active against a wide range of bacteria
what are narrow spectrum antibiotics?
Antibiotics which are only effective against a narrow range of bacteria.
What are some things to consider when selecting antimicrobial drugs for treatment?
Time dependent killing Concentration dependent killing AUC Pharmacokinetics Pharmacodynamics
Why would one use Antimicrobial combinations?
Mixed infections
Prevention of Antimicrobial resistance
Increase effectiveness in treating some infections
What are the two types of resistance?
Innate
Acquired
What is innate resistance?
preexisting genomic property
What is acquired resistance?
New genetically encoded trait not representative of the species. (acquired by mutation or horizontal gene transfer)
What are some mechanisms of resistance?
Enzymatic destruction or inactivation of drug
prevention of penetration to target sites within microbe
alteration of drugs target site
Rapid efflux of antibiotics
why is there an emergence of antimicrobial resistance?
Widespread antimicrobial use Microbial adaptation and change changes in demographics Medical advances Changes in ecosystems Cutbacks in public health systems
What is the potential impact of antimicrobial resistance
Increased mortality to infectious disease Veterinarian revisits High treatment costs Productivity loss and Economic Impact Zoonotic spread of resistant Microbes Increased nosocomial infections
What are some problematic bacterial organisms?
Vancomycin resistant Enterococcus (VRE)
Methicillin resistant Staphylococcus aureus (MRSA)
Extened spectrum Beta Lactamase (ESBL) producing E. coli and Klebsiella sp.
Fluoroquinolone resistant Campylobacter jejuni
Multiple drug resistant (MDR) E. coli and Salmonella
Organisms with innate resistance (Enterococcus, Enterobacter, Pseudomonas, Acinetobacter)
MDR and XDR Mycobacterium tuberculosis
How are Antimicrobials missused?
Providers- Over prescription use
Patients/clients- compliance, stockpiling, OTC
Industry- over promotion, competition between brands
Strategies to Reduce antimicrobial Resistance.
What does prudent Drug use mean?
Maximize efficacy of therapeutic regimens
Restrict extra-labe use to high risk patients
observe withdrawal period
Use antimicrobials of limited human health concern
use alternative therapies
strategies to reduce antimicrobial Resistance.
what is pathogen control?
Animal waste management
Reduce contamination in slaughter and processing
maintain herd health and infection control
Strategies to reduce antimicrobial Resistance
What does Policy mean?
control of drug use in food animals
National antimicrobial resistance monitoring system
educational efforts
Polyene Antifungal drugs what are they and what is their mechanism of action?
Amphotericin, Nystatin, and pimaricin
interact with sterols in the cell membrane
Azole antifungal drugs what are they and what is their mechanism of action?
Fluconazole, itraconazole, and Ketoconazole
inhibits cytochrome P450- dependent enzymes involved in the biosynthesis of ergosterol
Allylamine and Morpholine antifungal drugs what are they and what is their mechanism of action?
allylamines (naftifine, terbinafine) inhibit ergosterol biosynthesis
Antimetabolite antifungal drugs what are they and what is their mechanism of action?
5-Fluorocystosine, acts as an inhibitor of both DNA and RNA synthesis
