Chapter 20: Antimicrobial Drugs (EXAM 3) Flashcards
The use of drugs to treat a disease
Chemotherapy
Interfere with the growth of microbes within a host
Antimicrobial Drugs
A substance (small, organic) produced by a microbe that, in small amounts, inhibits another microbe
A substance produced by a microorganism that slows growth or kills bacteria
Antibiotic
Killing harmful microbes without damaging the host
Selective Toxicity
Bactericidal
kill bacteria directly
Bacteriostatic
Prevent bacteria from growing
An antibiotic that is effective aginst a wide range of both gram-positive and gram-negative bacteria
Broad-spectrum antibiotic
Some drugs have a _____ ______ __ _______ ______, or range of different microbial types that they affe
Narrow spectrum of microbial activity
in 1928: _____ discovered penicillin, produced by Penicillium
Fleming
in 1940: ____ _____ and ____ _____ performed first clinical trials for penicillin
Howard Florey
Ernst Chain
Innate Immunity
Phagocytic immune cells that have “eaten” bacterial invaders
Top 3 killers before Antibiotics (Infectious)
- Pneumonia
- Tuberculosis
- Diarrhea
Top 3 killers after Antibiotics (chronic)
- Heart Disease
- Cancer
- Diabetes
5 modes of action of antibiotics
- Inhibition of Cell Wall Synthesis
- Inhibition of Protein Synthesis
- Inhibition of Nucleic Acid replication
- Injury to Plasma Membrane
- Inhibition of Essential Metabolite synthesis
Peptidoglycan (cell wall) inhibitors
- Vancomycin (inhibits gram +, can’t get through outer membrane of gram -)
- Penicillin (B-lactam)
- Bacitracin
Selectively hydrolyzes the B- lactam ring of antibiotics such as penicillin and amoxicillin
Enzyme beta-lactamase
Breaks down and inactivates Chloramphenicol
Chloramphenicol acetyltransferase (CAT)
Neosporin contains
- Polymyxin B- damages gram - outer membranes causing cell leakage
- Bacitracin- inhibits cell wall synthesis
- Neomycin - inhibits protein synthesis
An agar-diffusion test to determine microbial susceptibility to chemotherapeutic agents
Kirby-Baur Disk-Diffusion Method
The lowest concentration of a chemotherapeutic agent that will prevent growth of the test microorganisms
Minimal inhibitory concentration (MIC)
_______ and ______ ______ arise to antibiotic resistant strains
Mutations and Natural Selection
Mutations that confer resistance arise by spontaneous mutations that are transferred vertically or by horizontal transfer of resistance genes
Antibiotics kill defenseless bacteria leaving behind (selecting) antibiotic resistant bacteria which then multiplies, passing the resistance gene on to their offspring
5 Cellular Mechanisms used to resist antibiotics
- Decreased Cell Permeability (altered surface charges, thickened peptidoglycan, altered membrane proteins involved in transport)
- Antibiotic Efflux Pumps
- Antibiotic Degradation
- Antibiotic Modification
- Target Alteration
Misuse of antibiotics selects for resistance mutants
Misuses include:
- using outdated or weakened antibiotics
- using antibiotics for the common cold and other inappropriate conditions
- using antibiotics in animal feed
- failing to complete the prescribed regimen
- using someone else’s leftover prescription
