Chapter 9. Physical and Chemical Control of Microbes
Concepts:
1. disinfection: To kill pathogenic microorganisms (vegetative form)
2. sterilization: To kill all microorganisms, including .pathogenic & non-pathogenic , vegetative &spore.
3. asepsis: a state of sterility (no living bacteria) ,
asepsis / antiseptic technique: the technique to prevent bacteria entering human body and other matters.
Aseptic technique is used in a variety of research applications, including: Animal husbandry ( immuno-compromised / barrier animals)；Tissue and cell culture； Diagnostics and animal healthcare procedures；Survival surgical procedures
4. antisepsis: To inhibit the growth and reproduction of bacteria in vitro.
5. bacteriostasis: prevention of growth of bacteria, but without killing them.
Bacteriostat: agent causing bacteriostasis.
Section I. Physical methods
I. heat lethal
make bacterial protein denature. bacterial DNA degrade, injury cell membrane .
1. dry heat:
(1) flame
(2) burn
(3) hot air oven: 160---170°C, 2―3hrs
(4) infrared
vegatatine 80---100°C 1hr
spore 160°C 2hrs
2. moist heat :
1)advantages over dry heat:
Bacteria absorb H2O , proteinis easy to solidify and denature .
Strong penetration
Eg. 100 th layer: dry heat 130-140°C 4hrs。72.5°C/100 th
Moist heat 105°C 3hrs. 101°C/100 th
(3) lalent heat gas –liquid .
2) Methods:
(1) pasteurization 62°C 30′ 72°C ， 30″
(2) Boiling 100°C 5′
(3) Steaming and intermittent sterilization: Arnold 3times.
(4) Autoclaving ： 1.05 kg/ cm2， 121.3°C 15－30′－spore
II.radiation
1. ultraviolet light: 200---300nm
interfere DNA replication ,form dimmer of Thymine .
strongest spectrum 260nm, DNA absort specfurm,
weak penetration : definite time and intensity
stimulate skin, eyes,.
Application : air . operation room
2. ionizing radiation : eg ,x-ray, r-ray.
III. filtration
fiter heat－labile solution
eg. Serum . toxin .antibiotics. etc.
seitz filter: K>EK>EK-S
glassical filter: G1 G2 G3……6
thin membrane filter
IV. Other: low temperature ( preserve bacteria)
Section II Chemical disinfection
Disinfectant:
Antiseptic:
chemical agents and mechanism
heavy –metal salts
bind to –SH and destroy it, inhibit activity of enzymes.
Protein denature. Merbromin .thimerosal 0.1%disinfectant
0.01%antiseptic
Oxidizer
H2 O 2 KMnO 4 CHCOOH(过氧乙酸)
Halogen（iodine ，chlorinated lime）
(1) SH S—S— enzyme
(2) destroy amino group, indol group.
(3) denature protein
surfactant
combine with phospholipid
increast membrane permeability
bromogeramine(新洁尔灭)
domiphen（杜灭芬）
4） aldehyde（醛类）
farmaldehyde、
enzyme deactivity
5） alcohol 70％ alcohal protein denature。
6）phenol （酚类）protein denature ， destroy cell membrane.
2． Application
skin： 2.5％碘酒 70％酒精
mucosa 2％ 红汞 0.1％新洁尔灭
drinking water 漂白粉
patients excreta 5％ phenol 2％lyson
air: formalin spray
3． Affecting factors
(1) concentration and time
(2) properties and quantity
(3) temperature and PH
(4) antagonist: organs protein, excreta
