This was carried out in 10 runs each of hospital fabrics including registered nurse uniforms, patients' coats and pants, operation theatre towels, and hand towels.
se of K. M. Kam
Abstract A bacteriological study was carried out in a local hospital laundry to examine the effects of (a) lowering the wash temperature from 90 to 71°C, and (b) adding chlorine to the penultimate cycle. This was carried out in 10 runs each of hospital fabrics including registered nurse uniforms, patients' coats and pants, operation theatre towels, and hand towels. While there was considerable variation in the baseline bacterial counts, lowering of temperature did not appreciably increase the latter. In contrast, addition of chlorine lowered, the bacterial counts although the difference was not statistically significant because of small sampling. Most of the organisms isolated were gram-positive spore-forming rods; no pseudomonas or staphylococci were identified. We recommend that a heating step (71°C for 11 minutes) be retained for disinfection, that fresh water be used for the whole wash cycle, and sufficient drying be carried out before the laundered materials are distributed for use. Keywords: Hospital; Laundry; Low temperature wash
Introduction Laundry practices in Hong Kong hospitals have traditionally been following the standards adopted in Western countries.1 The applicability of such practices in Hong Kong, however, has not been studied. In developed countries, laundering at lower temperatures used to be less effective because the tallow-based soaps and other detergents required hot water for proper emulsificalion. Suggestions of transmission of bacterial and viral infections via contaminated laundry have been made.2-7 With the advent of less heat-durable textile fabrics and detergents that do not require hot water for their catalytic action, and particularly after the energy crises in the 1970s, studies have been carried out to investigate the use of lower temperature washing in hospital laundries, in particular, its effect on bacterial flora and hospital infection through crosscontamination.8,9 A local working group was formed to review the practices of hospital laundries and to investigate the feasibility of using lower temperatures for washing, which would prolong the useful life of the laundry
Public Health Laboratory, Institute of Pathology, Sai Ying Pun Polyclinic, Hong Kong K. M. Kam, MB, BS, ABMM Correspondence to: Dr K. M. Kam
56
fabrics and lower energy costs. The following goals were set for the public health laboratories: (1) to establish a set of baseline data concerning the bacterial flora of various laundry materials under the current practice of 90 °C temperature washing; (2) to compare the change in flora when a lower temperature of washing (71 °C) is used; (3) to assess the effects of using chlorine in the penultimate cycle of washing. This paper summarizes the results of the bacteriological experiments carried out by the working group.
Materials and methods A major public hospital laundry, Chaiwan Laundry (CWL), was selected to carry the study. Two types of washers were in use daily: a 'tunnel' type and a 'washer-extractor' type. For the purpose of the study, a designated washer of the latter type was chosen because the washing steps can be more easily modified and monitored. The laundry manager worked closely with the Electrical and Mechanical Department (EMD) in monitoring the temperature of the wash cycle during the course of the experiments. The baseline (90 °C) and test (71°C) runs, with and without added chlorine (150 ppm final dilution) comprised each of ten weekly randomly selected samples of hand towels (HT), operation theatre (OT) towels, patient (FT) coats and pants, and registered nurse
57
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RUNS OT TOWEL PT COATS
PT PANTS HAND TOWEL
Fig. 1. T.B.C. variation in different runs
(RN) uniforms, taken between the period December 1990 and March 1992. After the processes of washing, drying, and/or ironing were finished and thus ready for use, the samples were immediately packed in sterile plastic bags and transported to the public health laboratory for analysis. Two bacteriological methods were initially used to enumerate the bacterial flora, viz., an elution method10 and a contact plate method.11 However, as the former continued to show inconsistent results, it was subsequently abandoned. In the contact plate method, three random pieces (10 x10 cm each) were aseptically cut from each sample, and eluted in Ringer solution by stomaching for 10 seconds. Five ml of the eluent was pipetted into molten plate count agar and incubated at 37°C for 48 hours. A duplicate set of plates were put up for each sample. In addition, 0.5 ml of eluent was each placed on a Baird-Parker plate and a horse blood agar plate and read after 24 and 48 hours of incubation at 37°C. Colony forming units (c.f.u.) were counted on each plate in each 100 cm2 piece and expressed as total bacterial count (T.B.C.) for each sample type. Geometric means (GM) of the T.B.C. and the standard deviation (SD) of the 10 runs were computed for each type of laundry material. Suspicious looking colonies of P. aeruginosa and S. aureus were
picked and identification carried out according to standard methods.12, 13
Results The baseline T.B.C. for 10 runs of samples taken over a 10-week period showed considerable variation in between runs (Fig. 1). The general pattern showed that HT had the highest counts in all 10 runs, ranging from 105 to 106. PT coats and pants had the same pattern of variation, with T.B.C. values between 103 and 104. OT towels appeared to show some high counts, e.g. in runs 3 and 9. While these might be related to the texture of the sample material during the elution process, the rest showed a consistent count of between 101 and 102. The comparison of the GM of T.B.C. for 10 runs at 90 °C and 71 °C each for the different materials tested (Fig. 2) showed that HT again had the highest T.B.C., which was not significantly affected by the lowering of washing temperature from 90 °C to 71 °C. Also, no significant effect was found in PT coats and pants as well as RN uniforms. In contrast, OT towels showed a significant rise in T.B.C. when the washing temperature was lowered. However, under current practice, OT towels are sterilized further in the Cen-
J Hong Kong Med Assoc Vol. 46, No. 1, March 1994
58
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Kam: Low temperature washing
tral Sterilization Services Department of individual hospitals before use. This underlines the importance of monitoring the performance of sterilizers and autoclaves in individual institutions. The effect of addition of chlorine (150 ppm final dilution) to the penultimate cycle at 71 °C was to effectively lower the T.B.C. on all materials whatever its nature (Fig. 3). PT coats and HT showed the greatest drop in T.B.C., while PT pants and OT towels had a smaller decrease. This could be partly explained by the higher T.B.C. in the former specimens which allowed the chlorine to exert its action. The small number of runs for the different samples in our study renders statistical analysis difficult. The predominant organisms isolated belonged to the gram-positive spore-formers related to the Bacillus group. There was a significant number of B. cereus-related organisms and thermophiles, possibly related to the high running temperature of the washing machines and the ability of their spores to survive even in exceedingly high temperatures. Repeated samples and testings did not show any S. aureus or P. aeruginosa.
Discussion A major concern during the course of the experiments was whether hospital infections, and ultimately the mortality and morbidity of hospitalized patients, would be affected by the lowering of washing temperature. A number of studies overseas have failed to confirm that these would be adversely affected,14-17 but there has not been any reports that the same can be applied to developing countries, particularly in Hong Kong where hepatitis B and tuberculosis are still rife. Both these organisms cannot be easily detected using standard cultural methods. Furthermore, the significance of their presence in the laundry setting is not clear. The present method of counting the T.B.C., as used and accepted in other international studies, is thus at best a circumstantial indicator of the degree of hygiene which is acceptable. This brings in the second concern of what is the acceptable standard. Various criteria have been proposed, with many being based on the prevalent local practices, durability of the textile material, energy saving consideration, and cosmetic appearance to the end-user, rather than on the objective standard, i.e. the effect on hospital cross-infections. As such, counts as low as 10 min. or 71 °C for >3 min., prolonged up to 8 min. with heavy loading to allow for 'mixing time'.20 We found that it was much more important to monitor and ensure that the temperature reaches and is maintained at the required level. This may entail a second monitor by EMD in addition to the one already installed in the washer. The present study has not detailed the energy saving aspect of our experiments, although calculations would be of importance in the present cost-containment climate. Our preliminary observation from results obtained by EMD during the study suggests very little appreciable decrease in energy consumption, unless the wash cycle temperature is dramatically lowered, e.g. from 71 °C to room temperature. Savings, however, are obtainable from prolonging the useful life of the laundry fabrics. It is reassuring that the major hospital infection pathogens, viz. pseudomonas and staphylococci, were not isolated in any detectable levels. It has been proposed10 that the most significant laundering procedures that eliminate bacteria are the dilution process, the addition of bleach, and the drying process. Wash temperature is said not to be a critical factor in eliminating viable bacteria when otherwise standard hospital laundering techniques are used. However, we do not concur completely with this statement, especially when applied to our heavily loaded laundries (4.2 x 106 kg for CWL in 1991), our endemic levels of hepatitis and tuberculosis in our tropical environment. We would therefore support the more cautious recommendation of retaining a disinfecting step in the wash cycle (i.e. 71 °C for 11 min.), monitoring the wash to maintain the temperature carefully, using fresh rather than recycled water, and ensuring adequate drying before issuing the laundered materials for use.
Acknowledgements The author wishes to thank members of the Working Group for Low Temperature Water Washing in Hospital Laundries: Ms Cindy Wong, Mr Edwin Lo, Ms Fion Lee, Mr Tarn Yiu-wah, Ms Patricia Ching, Mrs Ho Ng Kwan-yee and Mr Chan Chor-bun; the technical staff in Public Health Laboratory, Sai Ying Pun Polyclinic, who processed the specimens; and Dr S. H.Lee, Director of Health, for permission to publish this report.
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J Hong Kong Med Assoc Vol. 46, No. 1, March 1994
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12. Balows A, Hausler WJ Jr, Herrmann KL, Isenberg HD, Shadomy HJ. Manual of clinical microbiology, 5th Ed. Washington DC: American Society for Microbiology, 1991. 13. Cowan ST. Cowan and Steel's manual for the identification of medical bacteria, 2nd ed. Cambridge: Cambridge University Press, 1974. 14. Bennett JV, Brachman PS. Hospital infections, 2nd ed, Boston: Little, Brown and Company, 1986. 15. American Hospital Association. Infection control in the hospital, 4th ed. Chicago: American Hospital Association, 1979. 16. McGowen JE Jr. Environmental factors in nosocomial infection — a selective focus. Rev Infect Dis 1981; 3: 760-9. 17. Maki DG, Alvarado CJ, Hassemer CA, Zilz MA. Relation of the inanimate hospital environment to endemic nosocomial infection. N Engl J Med 1982; 307: 1562-6. 18. Walter WG, Schillinger JE. Bacterial survival in laundered fabrics. Appl Environ Microbiol 1975; 29: 368-73. 19. Collins B, Cripps N, Spooner A. Controlling microbial decontamination levels. Hospital Laundry Manager 1974: 212-3. 20. Hospital laundry arrangements for used and infected linen. Health Circular HC(87)30. London: Department of Health and Social Security, 1987.
