Chemical Agents of Control: Antibiotics, Antiseptics, & Disinfectants
Kirby-Bauer Method
(1) Inoculate a plate with bacteria to create a lawn of growth. (2) Place antibiotic discs on the agar to determine susceptibility of a specific bacteria to a specific antibiotic. (3) Place antiseptic and disinfectant infused discs on the agar to determine susceptibility of a specific bacteria to a specific antiseptic or disinfectant
Mechanisms of resistance (7)
(1) Produce an enzyme that destroys or deactivates the drug. (2)Slow or prevent entry of the drug into the cell. (3)Alter target of drug so it binds less effectively. (4)Alter their metabolic chemistry. (5) Pump antimicrobial drug out of the cell before it can act. (6) Biofilms retard drug diffusion and slow metabolic rate. (7)Mycobacterium tuberculosis produces MfpA protein
What are antiseptics uses for?
(1)Oral hygiene (2)Preparing skin surfaces prior to injections or surgical procedures (3)Cleaning skin and/or wounds after injuries
Antibiotics
A substance or compound produced by a bacteria or a fungi that kills or inhibits the growth of bacteria
Broad-spectrum antibiotics
Affect a wide range of bacteria such as both G(+) and G(-) bacteria or both aerobic and anaerobic bacteria
Goal of antibiotics
Affect bacteria without affecting host
Listerine mode of action
Bacterial cell wall destruction, bacterial enzymatic inhibition, and extraction of bacterial lipopolysaccharides
How are antiseptic classified?
By their chemical structures. Either bacteriostatic or bactericidal
Disinfectants
Chemicals produced by humans that are used to prevent the growth of bacteria or fungi on inanimate object
Antiseptics
Chemicals produced by humans that are used to prevent the growth of bacteria or fungi on living tissues
Antibiotic classification
Classified based on lab behavior (as bactericidal or bacteriostatic) or target-specificity (narrow-spectrum or borad-spectrumP
Penicillin mechanism of action
Contains a B-lactam ring which inhibits cell wall synthesis by preventing peptidoglycan cross linking
Hibiclens mode of action
Damages the cell wall and then enters the cell where it damages the cytoplasmic membrane
95% ethyl alcohol mode of action
Denaturation of proteins
Isopropyl Alcohol mode of action
Denaturation of proteins
Bacdown mode of action
Disruption of cell membranes and denaturation of proteins and enzymes of the cell
Lysol mode of action
Disruption of cell membranes and denaturation of proteins and enzymes of the cell
Sentry Wound Cream mode of action
Disruption of intermolecular interactions causes dissociation of cellular membrane lipid bilayers, which compromises cellular permeability controls and induces leakage of cellular contents
Bacdown soap mode of action
Inhibition of bacterial glycolysis that leads to cell death
100% and 50% bleach mode of action
Inhibition of protein synthesis and depressed DNA synthesis
SXT
Inhibits amino acid synthesis by acting as a competitive inhibitor to PABA (p-aminobenzoic acid). PABA is required for folic acid synthesis and folic acid is required for amino acid & purine synthesis.
Tetracylcyine mechanism of action
Inhibits protein synthesis by binding to the 30S ribosomal subunit & inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex
Erthromycin mechanism of action
Inhibits protein synthesis by binding to the 50S ribosomal subunit & inhibiting aminoacyl transferase which is necessary to move tRNA from the A site to the P site
Clindamycin mechanism of action
Inhibits protein synthesis by inhibiting ribosomal translocation
gentamycin mechanism of action
Inhibits protein synthesis by interfering with proof-reading steps or by inhibiting aminoacyl transferase like erythromycin
Types of Antiseptics
Listerine, hydrogen peroxide, isopropyl alcohol, hibiclens, povidone iodine, sentry wound cream
Side effects of antibiotics
Mechanisms: exaggerated response, immunological reactions, toxic effects; host factors: genetic makeup, integrity of drug elimination mechanisms, concomitant medical disorders
Antibiotic resistance
Occurs when bacteria change in some way that reduces or eliminates the effectiveness of antibiotics designed to cure or prevent infections
How are disinfectants categorized?
Oxidizing and non-oxidizing
Povidone iodine mode of action
Penetrate the cell wall and the lethal effects are believed to result from disruption of protein and nucleic acid structure and synthesis
Amplicillin mechanism of action
Penicillin derivative with same mechanism of action
Hydrogen Peroxide mode of action
Produces destructive hydroxyl free radicals that can attack membrane lipids, DNA, and other essential cell components
Mueller-Hinton Agar Plates
Show acceptable batch-to-batch reproducibility for susceptibility testing, Support satisfactory growth of most non-fastidious pathogens
Narrow-spectrum antibiotics
Target specific bacteria such as only G(+), only G9-), only aerobic, or only anaerobic bacteria
Mechanism of action
The specific biochemical interaction through which a drug substance produces its pharmacological effect
Cephalothin mechanism of action
a β-lactam ring containing antibiotic with same mechanism of action
Types of bacteriostatic
clindamycin, erthryomycin, gentamycin, tetracycline, SXT
What do most disinfects do to be effective?
disrupt cellular metabolism by denaturing proteins or destroy the cell wall of microorganisms. Most are no effective on spores
Bactericidal
kills bacteria directly
Types of disnfectants
lysol, 50% bleach, 100% bleach, 95% ethyl alcohol, bacdon, bacdown handsoap
Types of Bactericidal
penicillin, ampicillin, cephalothin
Three ways antibiotic use promotes antibiotic-resistant bacteria
resistant bacteria may be left to grow and multiply, widespread use, not effective against viral infections
Bacteriostatic
slows or prevent cell division
