Module 8: Antimicrobial Agents Flashcards
Antimicrobial Agent
compound capable of destroying or inhibiting microorganisms
Antibiotic
a chemical substance from one microorganism that can kill or inhibit another microbe
Prophylaxis
use of a drug to prevent imminent infection of a person at risk
Semisynthetic Drugs
drugs that are chemically modified in the laboratory after being isolated from natural sources
Synthetic Drugs
drugs produced entirely by chemical reactions
Narrow Spectrum
antimicrobial effective against a limited array of microbial types
Broad Spectrum
antimicrobial effective against a wide variety of microbial types
Goal for the ideal microbial drug
- administer to an infected person, which destroys the infective agent without harming the host’s cell
- disrupt the cell process or structure of bacteria, fungi, and protozoa
- inhibit virus replication
The Ideal Microbial Drug
- selectively toxin to microbe but not toxic to host cells
- microbicidal rather than microbistratic
- functions even when highly diluted in body fluids
- remain long enough to act and is not broken down or excreted prematurely
-doesn’t lead to the development of antimicrobial resistance - readily delivered to the site of infection
5 Modes of Action of Microbial Agents
- inhibition of cell wall synthesis
- inhibition of nucleic acid (RNA + DNA) structure and function
- inhibition of protein synthesis
- interference with cytoplasmic membrane structure or function
- inhibition of folic acid synthesis
Inhibition of Cell Wall Synthesis
- penicillins
- cephalosporins
- carbapenems
Inhibition of nucleic acid structure and function
- fluoroquinolones
inhibition of protein synthesis
- aminoglycosides (misreading of mRNA)
- tetracylines
- macrolides
interference with cell membrane structure or function
- polymyxins (membrane phospholipids)
inhibition of folic acid synthesis
- sulfonamides
Antifungal Agents
- fungi and human cels are both eukaryotic
Antifungal Agents - Macrolides Polyenes
bind to fungal membranes causing loss of selective permeability
Antifungal Agents - Azoles
interfere with sterol synthesis in fungi (cell membrane)
Antifungal Agents - Echinocandins
inhibit cell wall synthesis
Antifungal Agents - Allylamines
inhibit enzyme crucial for ergosterol synthesis (cell membrane)
3 modes of action for antiviral agents
- inhibition of virus entry
- inhibition of nucleic acid synthesis
- inhibition of viral assembly/release
Antiviral Agents - Interferon
- produced naturally by certain white blood cells
- induces the production of proteins which inhibit the viral replication
- important immune regulator of cytokines -> activate the development of white blood cells
Most Common Antiprotozoal Agent
Metronidazole
Drug Resistance
an adaptive response in which microorganisms being to tolerate an amount of drug that would ordinary be inhibitors
Drug Resistance 1
spontaneous mutation in critical chromosomal genes
Drug Resistance 2
acquisition of entire new genes or sets of genes via horizontal transfer from another species
Mechanisms of Drug Resistance (5)
- new enzymes are synthesized -> inactivates the drug
- permeability or uptake of drug into bacterium is decreased
- drug is immediately eliminated
- binding sites for drugs are decreased in number and/or affinity
- an affected metabolic pathway is shut down, or an alternate pathway is used
Human Role in Antimicrobial Resistance
- improper use of antibiotics
- less control in developing countries
- improper use of antimicrobial agents
Antimicrobial Resistance three hazard levels
- urgent threats
- serious threats
- concerning threats
