Control infection

In a report released in early January two thirds of NHS hospitals were slated for inadequate cleanliness. Possible cross infection via the hospital laundry service was only one of a very wide range of issues considered. Despite the fact that organisations processing hospital linen have had strict regimes in place for a number of years, now is the time for these to be audited and reviewed.

For many years the standard technique for disinfecting hospital linen during laundering has relied on implied thermal disinfection, maintaining work in the hot wash above 710C for at least three minutes giving a kill which is virtually total for all except a few spore- forming micro-organisms such as anthrax.

For polyester and polyester cotton this requirement is modified to a temperature of 650C held for a minimum of ten minutes to avoid problems with polyester at higher temperatures.

Recently, there has been increasing use of chemical disinfection, mainly for fabrics which cannot be safely taken up to thermal disinfection temperatures. Chemical disinfection becomes important for fabrics containing acrylic and modacrylic fibres.

Throughout Europe

The latter are used for their inherent flame retardancy but both types of fabric shrink excessively if taken to disinfection temperatures. For these, sterilisation using sodium hypochlorite bleach solutions at 150 parts per million in the rinse has generally proved acceptable.

Meanwhile throughout Europe there have been tremendous strides in developing systems for general use based on thermo-chemical disinfection, generally at temperatures around 600C.

These can be used for all fabrics including cotton and are designed not only to give greater assurance of total kill but also to make substantial contributions to reducing energy consumption and hence carbon dioxide emissions. In the UK the Central Sterilising Club has formed a Laundry Group to review and advise on the changes, and research needed, to update the Department of Health guideline on disinfection in laundering (HSG (95) 18) and this brings together laundry engineers both from the private sector and NHS trusts. It is chaired by Nigel Cripps of the Estates Business Agency.

The recent report on hospital cleanliness and cross infection risks will doubtless prompt a response from this group.

Machine sterilisation

For laundries using washer-extractors there are no sterilisation requirements because the entire machine is taken up to main wash temperature so any internal growth of micro-organisms is deemed to be killed at this point. However, good practice demands that where hospital work is still being processed in ordinary washer-extractors rather than in barrier machines then those parts of the machine with which linen can come into contact during unloading and which might carry bacteria are wiped down regularly during the working day.

Continuous batch washers pose far more serious problems because when these stand overnight, bacteria breed from end to end as well as in the press and in the various tanks.

This means that proper steam sterilisation at the start of the working day is an essential pre-requisite that should not be skimped.

Machines through which hospital work is to be processed must be fitted with the appropriate steam sterilisation lances to enable this to be achieved quickly and automatically and all reputable machine suppliers are familiar with these requirements and have systems which comply.

Where a hospital infection control officer is investigating a cross infection problem, the adequacy of daily sterilisation is one of the first things to be checked.

Removing the nutrients for growth of micro-organisms: Bacteria and viruses require nutrition and poor removal of protein soiling and staining is a major contribution to allowing reinfection of clean linen during handling in the laundry and on the ward. Total removal of proteins calls for adequate time at low temperature with proper detergency in the wash process followed by time and plenty of mechanical action at high temperature with good detergency in the main wash.

Overloading, shortening the stage time, allowing front-end temperatures on a tunnel washer to rise, skimping detergent addition and failing to control water flows will all contribute to poor protein removal. The result is invisible accumulation of bacteria within a day or two of laundering, usually accompanied by an unpleasant odour in the ward linen store.

The same problem arises if the suspending power of the detergent is not sufficient to prevent redeposition of the soiling back onto the fabric. It is no good washing all the proteins off if they are then redeposited in a layer a few molecules thick, the bugs simply have to walk further to get their nutrition but they thrive nevertheless. The odours they generate usually come from their excrement.

Why does hospital work carry so much protein? All human body fluids tend to be protein based and one of the main functions of hospital linen is to absorb these - blood, skin sebum, body oils, perspiration, urine, faeces and vomit are all rich in protein and require total removal.

No patient wants to be sleeping between sheets covered with a thin layer of what should have been washed off and flushed down the drain in the laundry.

Monitoring and control of cross infection risks in the laundry: Until quite recently most hospital laundries relied on regular checks by the engineer to ensure that the temperature gauge on the washing machine was working properly and giving the correct signal and that the thermocouple probe was actually dipping in the water whose temperature it was supposed to be measuring.

Regular cleaning of the probes under planned preventative maintenance systems also improves matters markedly. This will no longer be adequate in the future and hospital laundries specifying new equipment are now calling for recording of temperature to enable batch traceability.

In this way it should be possible to call for a set of temperature records from a bank of washer-extractors or from a continuous batch washer to verify that work processed last Tuesday and Wednesday was actually disinfected and so could not have been contributing to problems on Thursday, Friday, Saturday and Sunday with an infection outbreak on a particular ward.

Feedforward

Some engineers back up feedforward control of implied thermal disinfection with feedback control using dip slides. A dip slide is a lollipop enclosed in a small perspex tube. One side of the lollipop is coated with blood agar to enable any bacteria to grow and the other provides a check on fungi.

The slide is exposed to the linen being tested and then incubated in its sterile plastic cylinder for two days in the case of bacteria or seven days in the case of fungi. Although an incubator at 350C is the best way of doing this, for most purposes the dip slide in its container can be left on top of a filing cabinet in the office. Any serious failure to disinfect properly will result in more than just one or two colonies growing on one slide or the other (or both). Hospital control of infection committees tend to use much more precise cultures on petri dishes for identifying particular micro-organisms that are giving rise to problems.

MRSA is a particular problem, especially in geriatric wards, intensive care units and nursing homes. If soiling in the wash liquor has redeposited onto the linen this can be detected using a laundry reflectometer. White cotton flatwork should score over 90% - any lower reading points to greying which will involve redeposition of soiling including proteins.

This is why hospital linen contracts usually involve quality control based on minimum reflectance scores.

Finally, the ward sister’s nose is the best monitor of all. If the ward linen cupboard smells then there is almost certainly a problem with micro-organic growth on unremoved soiling. It is difficult to argue with this and most laundry engineers are best advised to get in and sort it out.

What about the future?

So are things going to get easier in the future? Quite definitely not. The recent report means that cross infection is likely to become a very hot issue in all private and trust hospitals over the next twelve months and beyond. Laundry engineers can expect to see much higher levels of monitoring and much more stringent application of standard requirements.

To this has to be added the progressive impact of the new theatre wear regulations to comply with European Union requirements. New surgical gowns and drapes are now regarded as medical devices and as such they have to comply with strict criteria regarding air permeability (to limit passage of airborne bacteria which might be riding on lint or particles), blood permeability (to prevent infection of the patient by the surgeon and vice versa), blood absorbency and a whole host of other requirements.

The key requirement for the laundry which has been taxing may suppliers for the last four or five years is that reusable gowns and drapes must comply with the legal requirements after every laundering cycle, not just when they are new. This represents a very significant increase in requirement over gowns and drapes based on cotton balloon cloth and many trusts have still not come fully to grips with this. The recent report is likely to accelerate the adoption of appropriate policies in this area also.

The laundry engineer has a pivotal role to play in the entire area of healthcare disinfection which goes well beyond machinery and extends to assured chemistry, process control, greatly improved monitoring and future alertness. Some control of infection committees still do not ask for appropriate risk assessments in these areas from hospital laundries.

That is all set to change with short shrift given to the unprepared.