Ethylene oxide sterilisation--is it safe?

Tests show that ethylene oxide penetrates and can sterilise long narrow tubes in a hospital ethylene oxide steriliser. Residual ethylene oxide levels in plastic tubing after sterilisation have been estimated. Although initially the levels were very high, storage for four days at room temperature reduced them to a safe level. If adequate controls of the sterilising process and storage are carried out, sterilisation by ethylene oxide is considered to be safe for new plastics and clean equipment.

Autoclaves and their dangers and safety in laboratories.

Using a laboratory downward displacement vertical autoclave with the help of thermocouples recorded on a 12 point multichannel strip recorder, the risk of failing to sterilize laboratory discard buckets has been demonstrated. The use of proper temperature and time controls can prevent this risk. A load in a bucket with perforated sides is more easily sterilized than in a solid bucket. Wire baskets, where appropriate, facilitate the sterilizing practice. The addition of water to a bucket does not reduce the time of heating up. It is desirable that sealed bottles of media should not be sterilized in simple downward displacement autoclaves, but if used, strict monitoring of temperatures and times is essential both in the heating up stage and especially in the cooling stage. The temperatures in bottles are slow to rise and very slow to fall. Bottles at high temperature 80-105 degrees C. or over have a high internal pressure which can allow the bottles to explode when subjected to thermal shock if removed too early. It is suggested that all laboratory autoclaves should have a load temperature simulator or similar device to control the temperature of the load during the cycle automatically. For the sterilization of fluid media, it is suggested that, in addition to a simulator there should be accelerated cooling to reduce damage to the media and, what is more important, to rapidly bring down the temperature and thus the internal pressure in the bottles to a safe level. The opening of the sterilizer door or lid should be automatically controlled by the load temperature simulator.

Non-toxigenic Corynebacterium diphtheriae in a boarding school.

A non-toxigenic strain of Corynebacterium diphtheriae var. gravis was isolated from 31 boys during an outbreak of sore throats at a boarding school of 15 staff and 134 pupils. Despite the non-toxigenicity of the strain involved, conventional isolation procedures were observed and all boys at the school were treated with antibiotics. Restrictions on the school were only relaxed when no further carriers were detected. The rationale of such management of an episode involving a non-toxigenic strain is discussed.