Orientating investigation of the inactivation of Staphylococcus aureus in the laundry process
BACKGROUND: The trend to washing processes with reduced water volume and small temperatures (below 40 °C), which is quite meaningful for environmental protection reasons, has to be regarded more differentiated from a hygienic-microbiological point of view. In particular the simultaneously increasing number of persons in need of domestic care and the early discharge of predisposed patients from the hospital make a sensitisation of hygiene strategies in the domestic environment – this includes laundry washing – necessary. Frequently arising reinfections with Staphylococcus aureus with Atopic Dermatitis (AD) in the domestic environment led to the cause to look critically at the modern wash processes in private households. In the present study selected detergents in combination with different washing processes were examined for their effectiveness against S. aureus. The reduction effect and a possible cross contamination during the washing process were examined. METHODS: The test organism was S. aureus ATCC 6538. The tests of the different wash processes were carried out accordingly to the “DGHM Standardmethoden” (2001), method 17. To simulate practical conditions the test dirt was shifted with defibrinated sheep blood in order to make allowances for remaining organic contaminations. The investigations took place with a smaller industrial washing machine (5 kg capacity). All wash processes consisted of a main washing cycle, while 3 of 21 tests consisted of an additional pre wash and a main wash cycle. A bleach containing detergent, a colour detergent and a detergent without bleach were used. The test-temperatures of the washing processes took place at 30 °C, 40 °C, 60 °C or 80 °C. The effectiveness of hygienic supplements and disinfectant additives was examined randomly. RESULTS: Wash processes with 30 °C in combination with colour detergents or detergents with optical brightener led to cross contamination and reached a reduction (r) of maximal 2.54 log10 units and were therefore not able to reduce the cell count sufficiently. At a temperature of 40 °C the full detergent (with bleach) inactivated the test organisms completely (r = 8.06 to log10-units). The colour detergent in contrast showed even at 60 °C an insufficient inactivating of the test organisms. An additional pre wash even strengthened cross contamination with this setting. CONCLUSIONS: The available study clarifies that the present development of washing processes and the simultaneous rise of the domestic patient necessitate a sensitization of the view on daily washing processes in households. It is recommended to examine the reduction abilities of different procedures regarding process (pre and main wash), detergent (colour and full detergent) and temperature (30 °C – 80 °C). In the available study a practicable model was presented for the characterisation of these processes with consideration of cross contamination. Hygiene & Medizin 2011;36:1/2.
Publication Type: Journal article
Publisher: Hygiene & Medizin