Measuring cleanliness in the hospital environment
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February 2006
Hospital-acquired infection is a serious cause of morbidity and mortality in the clinical setting. Here, Fiona Macrae discusses some ways in which hospitals can assess and monitor the microbial cleanliness of critical areas.
Hospital-acquired, or nosocomial, infection is a serious cause for concern. In the UK alone, it affects around 300,000 people each year, causing an estimated 5000 deaths. To combat this, a tough new hygiene code is being proposed. Hospitals will be monitored for compliance, and sanctions will be taken against those that do not comply. Environmental cleanliness is one of several factors that have been identified as important in the control of hospitalacquired infection.
Hospital-acquired infections (HAIs) are a significant drain on resources for health services around the world. In most developed countries, 6û10% of patients will acquire an infection during their stay in hospital.1 This has resulted in increases in patient morbidity and mortality, the need for additional therapeutic intervention and infection control measures and prolonged hospitalisation, with subsequent impact on bed availability and waiting lists. In the UK alone, the cost of such infections is estimated to be in the region of ú1 billion a year.2
Several factors have been identified as contributing to the increase in HAIs (Table 1),2 some of which are the result of the increasing population of vulnerable individuals in our hospitals, and are therefore difficult to control. Others, however, such as hygiene compliance and environmental cleanliness, have become the focus of action for the NHS3 and have been placed at the heart of inspection regimes.1
At a recent meeting,4 which met to discuss the harnessing of science to combat HAIs, Professor Gary French, from King's College and Guy's and St Thomas' NHS Trust, acknowledged that direct evidence linking HAIs to environmental cleanliness is still lacking. However, he went on to stress that there is considerable indirect evidence that the environment may contribute to cross-contamination. For example:
ò many nosocomial organisms survive for weeks/months in a dry environment
ò the environment around affected patients is often extensively contaminated, providing a potential source for hand transfer
ò some outbreaks appear to have been controlled by environmental cleaning
ò routine cleaning does not always eliminate contamination.
It was also revealed at the meeting that, in one study, surface swabbing of isolation rooms, ward bays and bathrooms found extensive contamination with methicillin-resistant Staphylococcus aureus (MRSA). Similar findings with a different contaminant were also discussed, and one delegate reported that an unusual strain of Acinetobacter species reappeared at his hospital one month and four months after the index patient had been discharged, suggesting that the organism had persisted in the environment, despite rigorous cleaning.
Environmental monitoring in hospitals
The new Matron's Charter states that the patient environment will be well maintained, clean and safe.5 However, as we have seen, visual cleanliness does not necessarily indicate the absence of microbial contaminants. The Department of Health report, Towards cleaner hospitals and lower rates of infection1 states that "preventing infections requires more than simple cleanliness". Among the actions required to reduce reservoirs of infection are the cleaning and monitoring of environmental surfaces, in addition to the prevention of air and waterborne infection.2
Despite the best cleaning regimes, the traffic of people through every hospital makes it impossible to ensure a sterile environment, particularly in general wards and corridors. There are certain high-risk areas, however, where the monitoring of cleanliness can serve to protect the most vulnerable of patients: for example, in operating theatres, intensive care units, special care baby units, and treatment and isolation rooms. In such areas, the efficiency of cleaning procedures can be monitored by testing the air and certain surfaces (particularly those that will come in contact with patients) for the presence of microorganisms that can cause disease or infection.
Testing surfaces
Once a surface has been cleaned, the effectiveness of the cleaning procedure can be tested by using a contact plate (Fig 1). In a contact plate, the surface of the culture medium is above the sides of the plate. An area is sampled by gently pressing the domed surface of the agar on the test surface. If microbial contaminants are present, they will grow on the culture medium and form distinct colonies. These can be counted and identified, if required, allowing invisible dangers to be visualised easily.
Oxoid contact plates are manufactured using a special automated procedure to ensure a smooth, evenly distributed layer of agar on each plate. The new plate design ensures that the plates are easy to manipulate and stable to store in a stack. In addition, the new grip-lock lid helps to prevent accidental exposure of the agar, thus helping to ensure the integrity of the medium during use. A grid on the base of the plate subdivides the growing area for accurate, semi-quantitative colony counts. Inaccessible or uneven surfaces and equipment can be sampled using swabs. The swab tip is moistened and then wiped across the test surface. This can then be used to inoculate a culture plate directly, or put in a transport medium (eg Oxoid Stuart, Oxoid Amies or Oxoid Cary Blair transport medium) and take back to the laboratory for testing.
Testing the air
Some microorganisms may be carried in the air, on dust and other airborne particles. It is, therefore, important that the quality of air in critical areas be monitored routinely. This can be achieved by placing settle plates (Fig 2) in strategic positions around a designated area. A good position would be near doors or air vents, as these are potential sources of contaminated air. Settle plates are simply culture plates that are left exposed to the atmosphere for a specified time and then incubated in the laboratory to grow any airborne microorganisms that settle on the surface of the agar. Oxoid standard (90 mm) settle plates are available in a deep-fill format to avoid desiccation of the medium while exposed to the air.
Air quality is a good index of the overall sanitary condition of an area. Records from the routine monitoring of air quality can build a picture of the general standard of air hygiene in a hospital. These data are a valuable tool for the detection of potential hazards in critical areas or lapses in hygiene standards. Any problem areas can then be addressed accordingly.
Testing water
Contamination of the hospital water supply with a microorganism such as Legionella sp. may pose a serious threat to the health of immunocompromised patients, in particular. This can be avoided by appropriate building design and maintenance, cleaning water storage tanks, maintaining sufficiently high temperatures in hot water supplies, keeping cold water systems cold and minimising water storage.2 The effectiveness of such measures can be assured by regularly testing water samples for the presence of Legionella sp. and other potentially harmful microorganisms.
Laboratory analysis
Once samples have been taken and inoculated on an appropriate culture medium, the plates should be covered, incubated appropriately and examined for growth. A wide range of culture media is available from Oxoid, from generalpurpose media to more selective products, depending on the intended purpose. These can be supplied in dehydrated format or, for enhanced speed and convenience, as ready-poured plates. Oxoid prepared media products are quality-control tested using a low-dose inoculum to ensure optimum performance.
General purpose media, such as Oxoid tryptone soya agar and Oxoid Sabouraud dextrose agar (for yeasts and moulds), can be used to obtain an overall colony count. Each colony represents one microorganism on the area sampled, which gives a good indication of the microbial cleanliness of the environment tested. The laboratory is then able to report on whether or not the results fall within predefined acceptable limits.
In some cases the laboratory may perform an investigation for a particular problem microorganism, such as MRSA, Clostridium difficile or Legionella sp. In such instances, samples are inoculated on a medium with selective and diagnostic properties for identification purposes. For example, Oxoid oxacillinresistant screening agar (ORSA) and the new Oxoid chromogenic MRSA agar (Fig 3) are useful for the identification of MRSA colonies, with confirmation using the Oxoid PBP2' test; Oxoid BCYE agar with and without L-cysteine is used to identify colonies of Legionella species, which can be confirmed using the Oxoid Legionella latex test (Fig 4); and Oxoid Clostridium difficile moxalactam/ norfloxacin (CDMN) agar is used to detect the presence of C. difficile.
Role of the microbiologist
The conclusion of the recent science summit meeting was that many more studies are required to demonstrate the importance of the environment in the control of HAIs. Nevertheless, this aspect of hospital hygiene currently is receiving much attention and will, undoubtedly, be central in the formulation of future strategies for the reduction and prevention of these infections. Necessarily, there is a call for closer working relationships between biomedical scientists, medical staff and cleaners.1 Each has a responsibility to understand the importance of the other's role, as well as their own.
Strict monitoring
In regulated industries, such as the pharmaceutical and food industries, there is an obligation on manufacturers to ensure the safety of the products they sell. As part of this, they are very strict in monitoring the manufacturing and processing environments for potential contaminants. Environmental monitoring is regarded as an essential exercise to protect the consumer. Surely, we should be no less diligent in protecting the health of patients in hospital and in reducing the huge costs involved in treating HAIs.
References
1 Department of Health. Towards cleaner hospitals and lower rates of infection û a summary of action. July 2004.
2 Department of Health. Winning ways û working together to reduce hospitalacquired infections in England. December 2003.
3 Department of Health. Press release 2004/0375. 19 October 2004.
4 Department of Health. Science summit û harnessing science to combat hospitalacquired infections. December 2004.
5 Department of Health. Matron's charter 2004.
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