Microbiology 9 - Antimicrobials Flashcards
List the 7 main groups of antibiotics
- Penicillins
- Cephalosporins
- Macrolides
- Fluoroquinolones
- Sulfonamides
- Tetracyclines
- Aminoglycosides
Antibiotics must be more ____ to _____ than ____-
toxic
microorganism
host
What do all B-lactams have?
B-lactam ring
Sulphonamides inhibits _____
DHPS
enzyme involved in folate synthesis
What do bacteriostatic agents do?
They halt growth, but bacteria recover when drug stopped e.g. tetracycline
What do bactericidal agents do?
They kill bacteria for a period of time e.g. b-lactam
Conc dependent drugs rate of kill becomes _____
constant
What is broad spectrum?
Effective against a wide range of bacterial species
What is narrow spectrum?
Effective against a limited number of bacterial species
What needs to be considered when choosing antibiotics?
- Selectivity (treat what needed?)
- Toxicity (will it poison?)
- Therapeutic index (Toxic dose/ effective dose?)
What is disinfection?
Removes microbes from inanimate surfaces e.g. ethanol
Broad spec
What is antisepsis?
Removes microbes from living surfaces
Used to reduce microbial populations
Broad spec
What is preservation?
Substance added to product to prevent growth + degradation by microbes/ unwanted chemical changes
Used to increase shelf life in pharmaceuticals
What is osmosis?
Net movement of a solvent from high to low concentrations through a membrane
What is water activity (Aw)?
Proportion of uncomplexed water available to support microbial growth
What are the Aw values for bacteria & yeasts?
Bacteria = 0.9-0.95
Yeasts & moulds: 0.8-0.88
No microbial growth ≤0.6
Name and describe the process that can reduce Aw
Desiccation - removal of water vapour from products
What is minimum inhibitory concentration (MIC)?
Lowest concentration of chemical which prevents visible growth of a bacterium
What is minimum bactericidal concentration (MBC)?
Lowest conc of an antibacterial agent required to kill a particular bacterium
What is innate resistance?
Inherent ability of bacterial to resist a particular antibiotic (e.g. lack of cell wall)
What is acquired resistance and name 3 ways in which this can occur?
Result of changes to normal genome of bacteria
- transformation
- transduction
- conjugation
List 3 types of antibiotic resistance mechanisms
- Exclusion
- Inactivation
- Target modification
List alternatives to antimicrobial agents
- Natural products
- Bacteriophages & derived products
Give an example of antibiotics that work as an antibiotic & disinfectant
Efflux pumps
What type of inhibitor are sulphonamides?
competitive
In concentration dependent bactericidal drugs, why does the rate of kill eventually become constant?
limited by agent diffusion
When is Isoniazid a bacteriostatic drug?
Lag phase and dormant mycobacteria
When is Isoniazid a bactericidal drug?
Log phase mycobacteria
Misuse of antibiotics leads to risk of _______
resistance
Antiseptics must be non-____
non-toxic
The concentration of the active ingredient in antiseptics is lower/higher than in disinfectants
lower
Where can resistance genes come from?
- bacteria having survived antibiotic treatment
- antibiotic producers
- bacteria that exist alongside antibiotic producers
What are the 3 main ways in which bacteria obtains acquired resistance?
- transformation
- transduction
- conjugation
