STERILIZATION OF THE CATGUT

The intestine of sheep is infected with bacteria e.g. E-coli, Streptococcus faecalis and the dangerous anaerobic spore-forming organisms e.g. bacillus anthracis and those bacteria which cause tetanus and which cause Gas Gangrene.

METHODS USED FOR STERILIZATION:

1-CHEMICAL METHOD:

It employs a material which is sporocidal. The main chemicals used are Formaldehyde, Hydrogen Peroxide, Methyl Iodide, Iodine and Ethylene Oxide.

Iodine is the most commonly used chemical.

PROCESS:

It consists of emersion of standard length of catgut which is wound on a frame in a standardized aqueous solution of iodine and potassium iodide. The catgut is then transferred to a sterile solvent to remove the excess of iodine. The sterile strands are then transferred under aseptic conditions to the final container containing 95% ethanol and sealed.

2- RADIATION METHOD:

It is commonly employed method.

PROCEDURE:

Prepared gut is packed in aluminum foil envelope containing 90% Isopropyl Alcohol (I.P.A).

The envelopes are then passed through radiation area on a conveyer belt. The catgut is sterilized when it is sealed in the final container. The external surface of the envelope is sterilized before opening by emersion in a solution of 1% Formaldehyde and 90% Isopropyl Alcohol (I.P.A).

ELECTRON PARTICLES OR GAMMA RAYS:

Usually 2.5 megarad is used for the sterilization. Now-a-days this type of sterilization is done on the final sealed container, containing suture and ligatures.

HEAT STERILIZATION:

The raw catgut contains about 20% moisture. Heating above 80^oC results in hydrolysis of collagen which is then converted into gelatin and catgut becomes useless. Therefore before heat sterilization, moisture from the catgut is removed by slow drying.

PROCEDURE:

The process is as follow:

i)                   TUBING: Suitable length of the catgut is coiled and placed in glass tubes.

ii)                  DRYING: The tubes are placed in basket and are dried in oven in which the temperature is slowly raised until completely dried. The sterilization is done by one of the two methods.

METHOD 1:

The baskets of tubes are placed in an autoclave and catgut is covered with organic fluid (Toluene) of high boiling point and the temperature is raised to about 160^oC. No pressure is applied.

METHOD 2:

The tubes are subjected to the vapors of organic fluid (Toluene of Xylol) under pressure and the temperature is raised to 160^oC for suitable time period.

After sterilization, the tubes are allowed to cool and filled with a sterile tubing fluid e.g. hydrated sterile alcohol to put back the necessary moisture.

It is sealed by the fusion of glass and whole process is done aseptic conditions.