Chemical disinfection now on agenda

1 August 1999



Improvements in fuel consumption, disinfection chemistry and permanent anti-microbial agents need to be reviewed together when tackling cross-infection problems, says Richard Neale.


Over the past two years there has been a steady increase in concerns regarding disinfection in hospital laundering and the ever present possibility of cross infection leading to a disease outbreak.

These concerns are prompted in part by some modern bacteria and unusual viruses which can be much more resistant to conventional disinfection methods. Ward managers sometimes find it frustrating that elderly and very weak patients become infected with debilitating diseases such as MRSA only a few days after total ward cleaning.

The time has gone when the hospital laundry manager can simply state that all wash processes assure implied thermal disinfection. Control of infection officers are looking for a much more positive reaction.

This is set against a background of concerns at government level regarding fossil fuels and a commitment via the UK government to reduce carbon dioxide emissions over the next ten years.

This policy is cascading down through all government departments, including the Department of Health and one result has been to put chemical and thermo-chemical disinfection alongside implied thermal disinfection as areas which merit attention. So what exactly is happening?

This Coventry based organisation is currently reviewing the provisions of the well established NHS guidelines contained in HSG (95) 18. This calls for implied thermal disinfection of virtually all hospital work by requiring the main wash stage to include at least three minutes above 71°C.

For heat sensitive polyester cottons, this can be reduced to ten minutes above 65ºC and for the very small proportion of fabrics such as modacrylic curtaining, where thermal disinfection would ruin the article, it is permissible to use sodium hypochlorite in the final rinse with a minimum of 150 parts per million, again for three minutes.

Concerns are arising within the CSC because when routine checks are carried out on linen which has supposedly been through a process involving thermal disinfection there are sometimes still viable micro-organisms left on the work or in the final rinse water. A far more proactive management control of bio-contamination on finished linen is clearly required.

One problem of linking disinfection with control of carbon dioxide emissions from burning fossil fuels is that in most laundries these are considered under entirely different budget headings. Few managers require their detergent suppliers to optimise the total cost of washing, taking into account heat energy, machine time, linen damage, water consumption, effluent quality and so on. There is a mistaken belief that if the cost per bag of soap can be minimised then all the others will somehow look after themselves and valuable opportunities are being lost.

A rather more wide ranging approach is being taken in Germany where disinfection is being considered in the light of total washing cost. This immediately brings into play the relative merits of chemical disinfection as opposed to implied thermal disinfection. Work by the Robert Koch Institute in Berlin for the German Federal Health Authority has resulted in wide ranging approvals for many individual laundry products. The use of these is generally combined with wash temperatures appreciably below 71°C, striking a balance between killing micro organisms with heat and with effective wash chemistry.

The result in principle of thermo-chemical disinfection now appears to have become widely accepted across Europe and it is probably time for the NHS in the UK to take a lead in encouraging exploration in this area for all UK laundry processors of hospital textiles.

One question which immediately arises is whether chemical disinfection results in trace amounts of bactericides and viricides being left on the finished article, so hindering reinfection—for example in the membrane press—and also minimising long term odour formation.

A major breakthrough in recent years has been the inclusion of TAED (Tetra Acetyl Ethylene Diamine) into laundry detergent formulations. This is not only a very good activator for generating, in the wash, chemicals for removing bleachable stains at low temperatures but it also provides a major contribution to hygiene.

In a paper to the 38th International Detergency Conference at WFK in Germany last year, Carol Sheane from the UK organisation Warwick International, demonstrated that colonies of microbial growth can survive within washing machines and large colonies of this bio-filim can be dislodged and transferred onto linen during the wash or rinse cycle. Carol Sheane found that formulations containing TAED can reduce the formation of bio-filim in a washing machine and give significant improvements in disinfection and in residual odour.

Other excellent research carried out in the UK includes that by Dr Kathy Orr at the Freeman Hospital, Newcastle Upon Tyne which refers to the use of fabrics impregnated with anti-microbial agents for the latest design of hospital theatre wear, itself subject to new EU regulations.

Checks

It should be self evident that any manager processing hospital linen can no longer rely solely on implied thermal disinfection without taking into account some of the latest developments. At the very least, a hospital laundry should be undertaking regular checks for micro-organic growth on supposedly disinfected linen coming out of a washing machine to ensure that not only has the disinfection stage worked properly but also that the linen has not been reinfected in rinsing or hydro-extraction.

Some managers work with control of infection officers and hospital laboratories using appropriate cultures in petri dishes which are able not only to indicate the presence or otherwise of micro organisms but also to identify which ones might be lethal.

Other managers are using cheap and cheerful dip slides such as those available from Knoll, which give a rough and ready estimate of total micro organic activity. The sterile dip slide, which usually costs less than £5, gives a good indication of bacteria on one side and fungi on the other side and can be incubated quite satisfactorily on the top of a normal office filing cabinet for two to seven days. It is not necessary to have a degree in microbiology to assess whether a problem exists or not. Obviously if a dip slide result does reveal that disinfection is incomplete you then need to seek expert assistance.

Technology does not stand still and over the next few years launderers are going to have to consider a range of changes for wash processes, not least in terms of more and more pressing demands for reductions in alkali discharged to drain. The improvements in fuel consumption, disinfection chemistry and permanent anti microbial agents all need to be reviewed together if the potential cross infection problems outlined in this article are to be brought under firm management control.



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