Lecture 6 Flashcards
Sterilization
killing all microorganism
Growth Inhibition
disinfection (inanimate surface) and antisepsis (surfaces of living tissues)
Heat sterilization
effect: denatures macromolecules & lose structure and function
Decimal reduction time (D)
from heat sterilization
amount of time to reduct population by 10%
Increase temp = decrease D
Thermal death time
from heat sterilization
how much heat and time it takes to kill things
Autoclave
sealed heating device
steam under high pressure (cell penetration power and reduces resistance of spores)
reaches 121C
variable time 10-15 min
Flash pasteurization
does not kill all microbes, but reduces their number
is rapid heating (71C, 15 sec) and rapid cooling (4C)
extends shelf life
UV radiation
exposure to UV waves
energy that modifies or breaks DNA
adv: practical and safer
dis: skin exposure cancerous and high levels UV shatters DNA; surface sterilization only, cannot penetrate solid objects
Ionizing radiation
exposure to electromagnetic radiation and radiation particles create radicals
radicals that disrupt proteins and lipids (shred the interior of the cell)
adv: cold sterilization & penetrates solids and liquids
dis: dangerous, requires special equipment
HEPA filters
are depth filters
borosilicate (glass) fibers
microbes trapped in fiber network
removes 99.97% of 0.3um particles
Membrane filters
strong polymers (e.g. cellulose)
microbes trapped on surface
Nucleopore filters
polycarbonate film
microbes trapped on surface
Antimicrobial agent
chemical that kills or inhibits microbial growth
classified by target organism (bacterio-, fungi-, and viri-) and action (-static, -cidal, and -lytic)
Bacterio/fungi/viri- static
stop growth
binds to ribosomes
prevents protein synthesis
ex streptomycin
Bacterio/fungi/viri- cidal
kills cells
cells dead but intact
bind to specific cellular targets
ex. formaldehyde
Bacterio/fungi/viri- lytic
kills cells
cells lyse and are destroyed target cell wall and membranes
ex. lysozyme
Minimum inhibitory concentration
amount of chemical needed to inhibit growth
Disc diffusion technique
zone of inhibition
Sterilants
inanimate surfaces
used in hospital and laboratory instruments
kill all microbial cells and endospores
ex. ethylene oxide (gas), formaldehyde (liquid)
applications: heat-sensitive equipment
Disinfectants
inanimate surfaces
used in hospital and laboratory instruments
kills all microbial cells but not endospores
delivery through electrostatic spray
applications: airplanes and hotels
Antiseptics (germicides)
hand washing and treating surface wounds
kill microbial cells or inhibit growth (non-toxic)
ex. ethanol and iodine (liquids)
Antimicrobial drugs
kill and inhibit growth inside the human body
classes: structure, function, and spectrum (how broad is the drug?)
categories: synthetic and natural
filter sterilization
effect: sterilization without heat and filters exclude passage of microbes
adv: useful for heat-sensitive items and very safe
dis: limited applications (liquid and gas)
Selective toxicity
Paul Ehrlich’s “magic bullet”
introduce something to the body to kill pathogens but not harm the body
Synthetic Drugs
selective toxicity and Paul Ehrlich
Sulfa drugs
are broad spectrum; affect gram +/- bacteria
mechanism: interfere with folic acid
folic acid is precursor to DNA (FA-> nucleic acids-> DNA)
Quinolones drugs
are broad spectrum; Mechanism: interfere with DNA Gyrase
Spectrum: gram +/-
synthetic
Isoniazid drugs
narrow spectrum
Mechanism: interfere with mycotlic acid -> component of cell wall in mycobacterium
Natural drugs
took thousands of years to develop
“tailored” by natural selection
Antibiotics
produced by microorganism
thousands known, 1% useful (selective toxicity)
Semi-synthetic
artificially modified antibiotics (enhances efficiency of antibiotic)
beta-lacatam
mechanism: interfere with cell wall
prevent peptidoglycan synthesis
spectrum: gram +/- and intracellular
ex. penicillin (accounts for 1/2 of all antibiotics used in medical setting) is produced by fungi & there are semi-synthetic penicillin’s
macrolids
mechanism: interfere with protein synthesis
binds to 50S subunit of ribosome
spectrum: gram +/-
ex. Erythromycin which is produced by bacteria
anti-viral drugs
have to target something that is not in human body bc antiviral drugs can also affect host cells
ex Azidothymidine (AZT)
anti-fungal drugs
fungi being eukaryotic organisms leads to anti-fungals can affect host cells
have to be fungi specific or topical
Ex. Ergosterol targets components of cytoplasmic membrane and replaces cholesterol found in animals
antibiotic resistance mechanisms
impermeability, efflux, inactivation, mutation in target, absence of target
and alternative of biochemical pathway
drug discover
new analogs, computer design
natural products
drug combinations
bacteriophages
Azidothymidine (AZT)
resembles Thymidine (T)
HIV treatment
nucleoside analog resemble nucleotides but prevent reverse transcription
