Laboratory‎ > ‎Anticeptics and Disinfectants

PURPOSE

Antimicrobial chemicals have killing effect on microorganisms. Anticeptics have killing effect on living organisms, whereas disinfectants are used to sterilize instruments.In this experiment we have examined the elimination effects of anticeptics (zeption, formaldehyde and ethyl alcohol) on the growth of Staphylacoccus aureus and E.coli bacterias.

THEORY

‘Antimicrobial agents’ are pesticides that control unwanted microbes on inanimate objects, in water, and on selected foods under certain circumstances. These pesticides are almost always chemicals, and they act by killing or inactivating microbes that are pests. Antimicrobial pesticides include the disinfectants used in swimming pools, drinking water supplies, and in hospitals to control microbes that can cause disease.

“Antimicrobial agents” means:

1.     Disinfectants intended to destroy or irreversibly inactivate infectious or other undesirable bacteria, pathogenic fungi, or viruses on surfaces or inanimate objects;

2.     Sanitizers intended to reduce the number of living bacteria or viable virus particles on inanimate surfaces, in water, or in air;

3.     Bacteriostats intended to inhibit the growth of bacteria in the presence of moisture;

4.     Sterilizers intended to destroy viruses and all living bacteria, fungi, and their spores, oninanimate surfaces; or

5.     Fungicides and fungistats intended to inhibit the growth of, or destroy fungi (including yeasts) pathogenic to man or other animals on inanimate surfaces;

6.     Commodity preservatives and protectants intended to inhibit the growth of, or destroy bacteria in or on raw materials (such as adhesives or plastics) used in manufacturing, or manufactured products (such as fuel, textiles, lubricants, and paints); or

7.     General use algicides labeled for use in:

i. Swimming pools, hot tubs, whirlpools, spas, ornamental ponds, fountains, fish tanks, and waterbeds;
ii. Water, wastewater and sewerage treatment plants, but only where there is a controlled inlet and outlet; and

iii. Industrial, commercial, and manufacturing processes.

ALCOHOLS – Ethyl or isopropyl at a concentration of 50-70% are used for some surfaces where a rapid evaporation of the chemical and leaving no residue may be important, such as on laboratory equipment, etc. Alcohols are low in sporocidal activity and must remain wet on the surface for several minutes to achieve any reasonable disinfection.

ALDEHYDES – Formaldehyde or more usually glutaraldehyde are used as instrument and catheter disinfectants. The glutaraldehyde is the basic chemical for various trademarks, such as Cidex, or Sonacide and newer ones such as Sporocidin or Glutacide or Totacide, etc. These are used for disinfectants or sterilization of instruments and catheters but not for environmental surfaces. They may also be used for pipettes and clinical thermometers, etc.

DETERGENTS
– The term detergent refers to a removal of soil or dirt and various types of detergents are available. The anionic detergent such as soap and sodium lauryl sulfate and its close chemical relative which are the ingredients in the various dish and laundry detergents have very low level in antimicrobial activity and work by the removal of dirt and microorganisms and rinsing them down the drain.

GASEOUS
AGENTS – Ethylene oxide as a gaseous agent may best be used as a sterilant, but has been used in liquids for antimicrobial action. The use of formaldehyde as a liquid at the 8% level in alcohol (for many hours) may have sterilizing capability as well as 20% 0 aqueous formalin and formaldehyde with low temperature steam (75 C).

MATERIALS AND METHODS

·E.coli and S.aureus cultures

·Nutrient agar

·Petries

·0,5%  Zeption (1)

·5% formaldehyde
(2)

·70% ethyl alcohol
(3)

PROCEDURE

·Petri was divided into 3 parts and numbers were given to each part as 1 ,2 and 3.

·0,2 ml of E.coli was inoculated on Nutrient agar by spread plate technique

·E.coli was spreaded on plate

·Then sterile small spherical shaped filter paper was immersed 0,5 % zeption solution and the put on the number 1 on the plate

·Another filter paper was immersed in 5% formaldehyde and put on number 2 on plate

·The last fitler paper was immersed into 70% ethyl alcohol and then put on number 3 on plate

·The plate was incubated at 37°C for 24 hours

·The effectiveness of anticeptics was compared after incubation

Indication of effectiveness of anticeptics

No growth = +++

Poor growth = ++

Excellent growth = 0 (none)

RESULTS

1 = ++

2= +++

3=+

DISCUSSION

In this experiment we have examined the effectiveness of anticeptics.We have seen that the effectiveness of anticeptics are 2>1>3.It means that the effectiveness of formaldehyde on the growth of E.coli is greater than that of zeption and ethly alcohol.These anticeptics are low level anticeptics so they dont have a strong killing effect on microorganisms.In food industry,anticeptics and disinfectants can be used to sterilize the equipments and for the elimination of microorganisms.There are some physical disinfection methods used in industries such as 

PASTEURIZATION

Pasteurization for wine and dairies for milk (62+ C for 30 minutes) has been adapted for disinfecting laboratory and health care facilities heat labile instruments that might be damaged by some temperatures. This consists, essentially, of a washing process to remove 99+% of the organic matter and organisms followed by immersing into water at 60 C-65 C for at least 30 minutes.

RADIATION

Ultra-violet lights as it is used in laboratories and health care facilities may reduce the number of organisms to low level in the air and on surfaces but it is not a sterilizing process. It must be well engineered and installed very carefully to prevent burning of skin and eyes.

FILTRATION

The filtration in the laboratory of fluids that are heat labile such as antibiotics, vitamins and other growth factors may be carried out with very fine pore membrane filters below 0.45 microns in diameter. These fluids should be checked for sterility by subculture before use.The HEPA filtration reduces the number of organisms but does not achieve real sterilization.

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