To sample or not to sample

Can the health sector learn from the food industry when it comes to improving hygiene? Professor Chris Griffith, head of the Food Research & Consultancy Unit at the University of Wales Institute, argues yes

Healthcare associated infections (HCAIs) and the role of cleaning in their prevention have, and continue to receive a high level of media attention. However, the link between environmental cleanliness and HCAIs is the subject of debate.^1,2,3 The UK guidelines for infection control⁴ recommend that the hospital environment “must be visibly clean” with routine bacteriological sampling rarely indicated unless there is an outbreak of infection.⁵ The rationale behind this approach is based on the assumption that the inanimate hospital environment is of “little importance in the spread of endemic infections but may occasionally have a role in outbreaks”.⁵

This belief and approach is in direct contrast to views held by the food industry, which believes the contamination of the inanimate food processing environment is important and is highly likely to lead to the same organisms contaminating the foods being produced.^6,7 The food industry in the 1980s and 1990s attracted the type of adverse media attention concerning cleanliness and risk management currently being received by hospitals.

In response, the food industry put in place a range of corrective risk management strategies including Hazard Analysis Critical Control Points (HACCP), which could be combined with independent third party auditing in relation to standards and practices.⁸ While the food manufacturing industry is not perfect, hygiene standards and practices have improved as a result of the measures taken.

Although not identical, there are interesting parallels in the survival, transfer and spread of pathogens in both food and healthcare environments. It has been argued in healthcare³ that it is the patients that contaminate the environment and not the reverse. If transmission one way is possible, it is difficult to believe the reverse cannot take place and studies have shown that reducing environmental contamination can lead to a reduction in infection rates⁹ and that contaminants from the environment can contaminate patients and ultimately lead to an infection.¹⁰

But the problem is complex and likely to involve many additional factors, including hand hygiene compliance rates, patient movement and bed occupancy levels.

The potential for an environmental pathogen to contaminate foods is well recognised and has led to a much more organised and scientific approach to environmental monitoring.⁶ Environmental monitoring (see Table 1) is used in the food industry for plant commissioning, validation and bench marking of cleaning methods, as well as the more routine monitoring and verification of cleaning and is predicated on the belief that isolation of pathogens from the environment is a cause for concern.

Another difference between the monitoring of cleaning in food and healthcare environments is how it is undertaken (Table 1). It is highly unlikely a major food processor would rely solely on visual measurement of cleanliness and would, for British Retail Consortium (BRC) certification, be required to have documented evidence of a monitoring programme and its results.

Table 1: Comparison of approaches to monitoring cleaning efficacy between food and healthcare industries

Monitoring cleanliness in the food industry starts with visual assessment (if visually dirty there is no point in other forms of measurement), but may then involve the measurement of residual soil using adenosine triphospahte (ATP). ATP is found in living cells and cell debris and is widely used in the food industry.6 While used by the top five world food manufacturing companies it has had only limited use in healthcare.^11,12,13 These studies have shown clearly that visual assessment alone is an inaccurate measure of cleanliness and produces an verly optimistic indication of cleaning efficiency. Such findings should question the value of the development of elaborate methods of assessing cleanliness based solely on visual assessment.¹⁴

ATP provides a very rapid (10-20 seconds) measure of residual surface soil i.e. cleanliness, if cleaning is defined as the removal of soil. ATP can be used on its own and as a preliminary step prior to microbiological sampling. ATP and microbiological assessments measure different things (the latter measures only residual viable organisms). Although sometimes undertaken,¹⁵ there is therefore little value in trying to directly correlate one with another.

For a strong correlation to exist, the ratios between organic debris and micro-organisms would need to be constant and there are many reasons why this might not be the case.⁶ Of much greater benefit is comparing the results obtained using both approaches in relation to pass/fail limits following properly implemented cleaning.^12,13 Surfaces passing ATP are much more likely to correlate with and achieve microbiological limits than those assessed visually (Table 2).

*ACC= Aerobic Colony Count

There is no ideal method for monitoring cleaning efficiency and in reality, as they measure different things ATP and microbiology should be used together as part of an integrated cost-effective assessment strategy.6 This considers not just the costs of testing but the costs of cleaning (which can be considerable and consider staff time, chemicals/equipment costs etc) as well as failure costs. Cleaning should deliver value for money (quality in relation to cost), and ATP can help to achieve this.⁶

However, not all ATP instruments are the same and some are more sensitive and reproducible than others and benchmark values obtained with one instrument/test are not applicable to values from other instruments/test combinations. Benchmark values after cleaning have been proposed and can be used in routine monitoring to improve the management of cleaning and in adopting a more scientific approach to decisions on cleaning frequency, as well as the validation of new cleaning methods.

Evidence is growing that poor cleaning can result in increased environmental surface contamination and this may contribute to pathogen reservoirs^16,17 and some cases of nosocomical infections caused by specific pathogens. An improved, more scientific assessment strategy may help to achieve better value for money from cleaning in healthcare as with the potential benefit of a reduction in infection rates caused by some pathogens.

References

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2. Dettenkofer M, Spencer RC. J Hosp Infect 2007; 65 (Supp2): 55-57. doi:10.1016/S0195-6701(07)60016-4

3. Fraise AP. J Hosp Infect 2007; 65 (Supp2): 58-59. doi:10.1016/S0195-6701(07)60017-6

4. Pratt RJ, Pellowe CM, Wilson JA, et al. J Hosp Infect 2007; 65 (supp 1): 1-29. doi: 10.1016S0195-6701(07)60002-4

5. Ayliffe GAJ, Fraise AP, Geddes AM, Mitchell K. Control of Hospital Infections: a practical Handbook. 4th edn. London: Hodder Arnold; 2002.

6. Griffth CJ. Improving surface sampling and detection of contamination, Handbook of Hygiene Control in the Food Industry. Cambridge: Woodhead Publishing; 2005.

7. Cordier JL. Assessing Microorganisms in Food and Factory. 3rd IAFP European Symposium on Food Safety. Rome: October 2007.

8. British Retail Consortium. Global Standard for Food Safety. Issue 5. TSO Stationary Office.

9. Denton M, Wilcox MH Parnell P, et al. J Hosp Infect 2004; 56: 106-110.

10. Hardy KJ, Oppenheim BA, Gossain S, Gao F, Hawkey PM. Infect Cont Hosp Epidemiol 2006; 27: 127-132.

11. Griffith, C.J., Cooper, R.A., Gilmore, J, Davies, C and Lewis M. (2000). Journal of Hospital Infection. 45(1): 19-28.

12. Griffith C.J., Obee P., Cooper R.A., Burton H.F., Lewis M (2007) Journal of Hospital Infection. June 66(4): pp352-359

13. Cooper R.A., Griffith C.J., Malik R.E., Obee P. and Looker N (2007) American Journal of Infection Control. 35 (5): pp 338-341

14. National Patient Safety Agency Report. The National Specifications for Cleanliness in the NHS: a framework for setting and measuring performance outcomes. NHS; April 2007.

15. Department of Health. Evaluation of ATP bioluminescence swabbing as a monitoring and training tool for effective hospital cleaning. Crown Copyright; 2007.

16. Sattar SA. Journal of Hospital Infection. 56, Supplement 2, April 2004: pp64-69

17. Sexton T, Clarke P, O'Neill E, Dillane T and Humphreys H (2006) Journal of Hospital Infection, 62(2): 133-260, February.