|
|
|
|
Articles: Science | Chemical Control
- Mr. ThummalaSanathReddy Reddy
| |
Chemical Control Of Microorganisms
Sterilization - killing all organisms in or on something
Disinfection - reduction of pathogens till harmless
• Antiseptic - used externally on tissue to destroy or inhibit organisms
• Disinfectant - used on surfaces (don't kill spores)
• Sanitizer - used on food prep equipment / utensils to reduce number
Bacteriocidal - kill bacteria
Bacteriostatic - prevent growth
Factors that affect death rate:
o Number of bacteria present (more means longer)
o Environmental factors (temp, pH)
o Dosage of agent used
o Presence of other inhibitory stuff (organic material)
o Bacterial factors (resistance)
Relative resistance of Microorganisms
Highest resistance Spore forming organisms
Moderate resistance Protozoan cysts
Hepatitis B
Poliovirus
Mycobacterium tuberculosis
Staph. aureus
Pseudomonas
Least resistance Most bacteria
Yeasts
Phenol Coefficient
• Use Salmonella typhi and Staph aureus as test organisms
• Compare agent's effectiveness against phenol (1)
• Higher numbers, more effective than phenol
Choosing agents:
• Fast acting
• Work on bacteria w/o being poisonous to people (even solvent)
• Penetrate material without staining
• Be stable when stored
• Inexpensive
• Smell good
Mechanisms of action
Attack cell wall/membrane - (soaps, alcohol)
Attack proteins - denature
Temporary - Bacteriostatic
Permanent - Bacteriocidal
Specific Agents
Soaps & Detergents
Solubilize membranes, mildly alkaline
• Bars of soap in public restrooms is bad idea
• 100+ strains isolated once
Quaternary ammonium compounds
• Many detergents
• Clean and disinfect
Halogens
• Chlorine- active ingredient in bleach
• Iodine - topical antisepsis
• Bromine - used in hot tubs (doesn't smell like chlorine does)
Heavy metals
• Silver nitrate - gonococcus
• Merthiolate (mercury)
• Silver and gold
• Copper sulfate in pipes - prevents algae growth
• Selenium - dandruff shampoo to kill fungi
Alcohols
• Solubilize membranes and denature proteins
• 70% works better than 95%
Phenols
• Solubilize membranes and denature proteins
• Lysol - action remains on surfaces for days
• Creosote has phenol derivative
Oxidizing agents
H2O2 is used to kill anaerobes in wounds
Aldehydes
• Formaldehyde, Glutaraldehyde
• Quickly inactivates enzymes
• Good on most resistant organisms
• Toxic to tissues, not good antiseptic
Gaseous compounds
• Ethylene oxide - only accepted chemical sterilant
• Used in special autoclave like machine
• Very toxic
• Used on spices, drugs, surgical supplies, plasticware
| Be first to comment on this Article!
| |
|
|
|
 |
| Advertisements |
|
|
|
|
| Advertisements |
|
.gif)
