Exam 2 deck 2 Flashcards
1
Q
Disk Diffusion method
A
Put filter paper soaked in a chemical on a culture
The bigger the zone of inhibition, the more affective the chemical agent
2
Q
Phenols
A
- Injure lipids in plasma membranes
- can be bacteriostatic or bactericidal
- active for a long time–> doesn’t break down fast
- antiseptic, but burns
- e.g. lysol
3
Q
Bisphenols
A
- disrupt plasma membrane
- Hexachlorophene is affective against G-
- Triclosan used to be common, but it leaves behind super resistant bacteria with no competition
4
Q
Essential Oils
A
- hydrocarbon mixtures from plants
- effective due to phenolics and terpenes
- e.g. oregano and oranges (flavor + preservatives)
- weaken cell wall of bacteria?
5
Q
2 Halogens discussed in class
A
Iodine and chlorine
6
Q
Iodine
A
- Impairs protein synthesis and alters membrane
- Tincture Iodine is a solution in aqueous alcohol
- Iodophor is combined with organic molecules (doesn’t stain)
7
Q
Chlorine
A
- oxidizing agent –> shuts down cellular enzyme systems
- bleach easily enters cell wall (HOCl)
- chloramine = chlorine and ammonia
8
Q
Alcohol
A
- denatures proteins and dissolves lipids
- no effect on endospores or non-enveloped viruses
- ethanol and isopropyl require water to be affective
- methanol is toxic
9
Q
Heavy metals
A
- Ag, Hg, Cu, Zn
- very small amount exert antimicrobial activity
- They denature proteins and act on -SH groups of proteins
- e.g. put silver nitrate in babies’ eyes
10
Q
Surface-Active Agents
A
Soap
-degerming through emulsification (not really antiseptic)
11
Q
Quaternary Ammonium Compounds
A
- Quats
- Denature proteins and disrupt the membrane
- effective on most things except endospores
12
Q
Chemical Food Preservatives
- what do they do?
- what are some examples?
A
- they inhibit metabolism in microbes, but humans can metabolize them
- sorbic acid, benzoic acid, and calcium propionate
- sodium nitrate
- nisin and natamycin
13
Q
Sorbic acid, benzoic acid, calcium propionate
A
control molds and bacteria in food and cosmetics
14
Q
sodium nitrate
A
prevents endospore germination
- in hot dogs, sausage, bacon, ham
- there’s some worry that it reacts with amino acids to cause cancer
15
Q
Nisin and natamycin
A
antibiotics solely used to prevent cheese spoilage
16
Q
Aldehydes
A
- one of the most affective antimicrobials
- inactivate proteins by cross-linking their functional groups
- formaldehyde preserves specimen
- glutaraldehyde is one of a few liquid chemical sterilizing agents (used for medical equipment)
17
Q
Chemical sterilization
A
- gaseous sterilant cause alkylation which replaces proteins’ hydrogen atoms with free radicals
- cross links nucleic acids and proteins
- used for heat-sensitive materials
- e.g. ethylene oxide which is affective, but toxic and explosive
18
Q
Are chemical and physical methods of microbial control specific?
A
NO! chemotherapeutic drugs are, though
