Antimicrobials Flashcards
Why do we administer antimicrobials in combinations?
Obtain antimicrobial synergism
Treat polymicrobial infections
Decrease the emergence of resistance
Reduce drug toxicity
Beta Lactams and Aminoglycosides given together to give a ____________ effect.
Beta Lactams and Aminoglycosides given together to give a synergistic effect.
Classes of antimicrobials that act on the cell wall/ cell membrane
Beta Lactams
Glycopeptides
Bacitracin
Polymyxin
Types of antimicrobial resistance
Innate Resistance
Acquired Resistance
Mechanism of action of antimetabolite antifungal drugs
Act as an inhibitor of both DNA and RNA synthesis
Examples of natural antibiotics
Streptomycin
Penicillin
Tetracycline
Semi-Synthetic Antibiotics
Chemically altered natural compound
Antimicrobial
Drugs that destroy microbes, prevent their multiplication or growth or prevent their pathogenic effect
Susceptibility result - R
High likelihood of therapeutic failure
Bacteriostatic
Inhibit bacteria
Susceptibility result - S
High likelihood of therapeutic success
Factors to consider in antimicrobial therapy
Cost
Safety
Ease of Use
Possible Emergence of Resistance
Classes of antimicrobials that act on protein synthesis
Tetracyclines
Macrolides
Aminoglycosides
Chloramphenicol
Lincosamides
Streptogramins
Mechanism of action of polyene antifungal drugs
Interact with sterols in the cell membrane
Susceptibility Break Point
Drug concentration above which an organism is considered resistant and at or below this value organism is susceptible to the drug
Tetracycline is a ________ spectrum antibiotic
Tetracycline is a broad spectrum antibiotic
Acquired Resistance
Acquired resistance by mutation or horizontal gene transfer
Bacteriocidal
Kills bacteria
Alexander Fleming
Discovered penicillin
To proceed with antimicrobial treatment, the veterinarian should know
Location of the infection
Likely pathogen
Antimicrobials effective against particular pathogen in particular site
Antimicrobial Agent
Chemical substance derived from a biological source or produced by a cheical synthesis that kills or inhabits the growth of microorganisms
Susceptibility result - I
Uncertain therapeutic outcome
Examples of synthetic antibiotics
Sulfonamide
Enrofloxacin
Marbofloxacin
Examples of semi-synthetic antibiotics
Ampicillin, Amikacin
Classes of antimicrobials that act on nucleic acid synthesis
Sulfonamides/Trimethoprim
Nitroimidazoles/ Nitrofurans
Fluroquinolones
Novobiocin
Rifampin
Classification of Antimicrobial agents is based on
Chemical family structure
Mode of action
Type of antimicrobial activity
Spectrum of antimicrobial activity
Innate Resistance
Pre-existing genomic property that causes resistance
Examples of Antifungal Drugs
Polyens
Azoles
Three break point values are
Susceptible
Intermediate
Resistant
Natural (True) Antibiotics
Produced by bacteria or fungus
Antibiotic
Chemical substance produced by a microorganism that inhabits the growth of or kills other microorganisms
Pharmacodynamics
Effect of the drug on the body, mechanism of action and efficacy
Synthetic Antibiotics
Chemically designed in the lab
Disk Diffusion (Kirby Bauer)
Bacterial isolate in pure culture
Spread on agar plate
Single-concentration antimicrobial disks used
Growth inhibition zone diameter measured
Compared to published reference break points
Mechanism of action of azole antifungal drugs
Inhibit cytochrome P450 dependent enzymes involved in the biosynthesis of ergosterol
Antifungal drugs target ________.
Antifungal drugs target ergosterols.
Narrow Spectrum Antibiotic
Affect only a narrow range of bacteria
Minimum Inhibitory Concentration (MIC)
Minimum amount of drug required to inhibit bacterial growth
Mechanisms of Resistance
Enzymatic destruction or inactivation
Prevention of penetration to target sites within microbe
Alteration of drug target site
Rapid efflux of antibiotics
Penicillin is a _________ spectrum antibiotic
Penicillin is a narrow spectrum antibiotic
Pharmacokinetics
Fate of the drug in the body
_______________________
Absorption, Transformation, Distribution and Elimination
Broad Spectrum Antibiotic
Active against a wide variety of bacteria
Mechanism of action of allyamine and morpholine antifungal drugs
Inhibit ergosterol biosynthesis
Broth Dilution
Multiple dilutions of antimicrobial agents
Published reference breakpoints to interpret
Measure and report growth inhibition endpoint
