Disadvantages of UV Light
Sonication
High frequency sound (15,000-200,000 cycles/sec)
that raises temperature up to 80°C
- Explodes cells
- G- are more sensitive
- G+ cocci are sensitive
- Fungal spores are sensitive
- Used in dental and medical offices
- Clears debris and saliva from instruments
- Cavitation
A fluid (air or liquid) is strained through a layer of material with openings large enough for the fluid to pass through but too small for microbes to pass thru
Membranes
pore sizes range from 8 to 0.02 µm
Types:
Cellulose acetate
Polycarbonate
Teflon (nylon types)
Charcoal
Diatomaceous earth
Unglazed porcelain
Uses of Filtration
(microbial removal depends
of pore size)
- Separate mixture of microorganisms
- Enumerate bacteria in water
- Serum and blood products
- Vaccines
- Enzymes
- Drugs
- Media
- Air
Chemical Agents Used in Microbiological Control
There are more than 10,000 products in the market.
An excessive preoccupation!!
Usually advertised as products that
kill germs
disinfect
antisepticize
clean
destroy
sanitize
deodorize
fight plaque
purify water
etc......
Best Choices:
Glutaraldehyde
- sporicidal
- high level of activity
- irritates skin
- not inactivated by OM
- unstable
- sporicidal
- high level of activity
- toxic to eyes
- not inactivated by OM
- toxic if ingested stable
Factors Affecting Germicide
Action
- Nature of microbes to treat
- Nature of material being treated
- Degree of contamination
- Time of exposure
- Strength of germicide
- Chemical action of germicide
- Organic matter (OM) interferes in disinfection as it forms bonds and chemical complexes
Units of concentration in solutions:
1 ppm is equal to 1mg/1000ml or 1mg/liter
Also equal to 1µg/ml
Percent (%) units are also used: 75% ethanol
Concentration and Exposure
Time of some Chemical Agents used in Disinfection
Agent |
Concentration | Exposure |
| Chlorine | 0.1-50 ppm | 2-10 min |
| Aqueous iodine | 2% | 1-150 min |
| Phenol | 1:70 | 10 min |
| Ethyl alcohol | 70% | 2-10 min |
| H2O2 | 3% | 0.3-12 sec |
| Qtnry ammonium | 300-450 ppm | 10 min |
| Ag ions | 2-14 mg/ml | 48 hr |
| Glutaraldehyde | 2% | less than 10 min |
| Ethylene oxide | 500 mg - 10 g/L | 2 min-25 hr |
| Chlorhexidine | 1:10 | 15-30 sec |