Topic 6: Control of Growth Flashcards
Sterilization
Killing all microbial life
Asepsis
Absence of contamination by unwanted organisms
Disinfection
Killing the microbes that cause disease on inanimate objects
Antisepsis
Disinfection on living tissue
Thermal death point
Lowest temperature needed to achieve sterilization within a certain time
Thermal death time
Time needed to completely eliminate a certain bacteria at a certain temperature
Decimal reduction time
Only kills 90%
Autoclaving
Steam under pressure and kills endospores
Pasteurization
Kills pathogens but not endospores
Ionizing radiation
Short wavelength, high energy damages DNA
Non-ionizing radiation
Low energy with thymine dimers
Use-dilution test
Metal rings dipped in bacteria are dried and placed in disinfectant to see whether the bacteria survive
Disk-diffusion test
Soak paper disks in chemical to be tested
Phenol
Disrupts membranes and proteins
Halogens used for disinfecting
Iodine or chlorine
Iodine
- Surface disinfectant
- Forms complexes with amino acids & fatty acids which inhibits protein synthesis
Chlorine (hypochlorous acid)
Disrupts enzymes associated with the membrane
Biguanides
- Chlorhexidine
- Attacks membranes, particularly gram positive
Heavy metals used for disinfecting
Copper, zinc, silver
Emulsifiers
- surface acting agents (like soap_
- Degerming
Quaternary ammonium compounds (quats)
- Modifications of ammonia
- Against gram positives
- Alters plasma membrane
(does not work against Pseudomonas)
Aldehydes
Link functional groups on proteins
Sterilizing gasses
Replace protein functional groups with alkyl groups
- Denatures proteins
Most resistant prokaryote
Prions
Least resistant prokaryotes
Viruses with lipid envelopes
