Evaluation of alcohol wipes used during aseptic manufacturing

Aseptic manufacturing can be described as a multiple step process by which many materials, equipments, medicinal products and containers are transferred into (and manipulated in) an environmentally controlled workspace to produce a sterile product. Items used for product preparation
usually start with some surface bioburden and as such need to be disinfected, usually by a combination of spraying with alcohol and wiping prior to and during transfer(s) into the isolator cabinet where the final product is manufactured (Hiom et al. 2004; Beaney 2006; Jackson and Wilson 2006)
In hospital aseptic units, high quality assurance (QA) standards have been introduced to maximize patient safety [e.g. ISO 13408-1; ISO 14644: Beaney 2006; Medicines and Healthcare products Regula- tory Agency (MHRA) 2007]. Examples of typical aseptic products would include intravenous (IV) cytotoxic drugs, trans-parenteral nutrition (TPN) and central intravenous additive (CIVA).

Transfer disinfection is usually based on a combination of 70% alcohol sprays and sterile wipes (Hiom 2000; Cockcroft et al. 2001; Hiom et al. 2004; Beaney 2006), where sterile wipes may be pre-alcohol impregnated, dry and ⁄ or alcohol wetted just before use. Current practice to validate transfer disinfection consists of contact plate enumeration of a flat surface before and after disinfection procedures. This is somewhat qualitative in nature, is exposed to the variabilities in efficacy of con- tact plate performance (Pinto et al. 2009) and is not accurate enough to accurately assess wipe efficacy. Indeed individual technique for trigger spraying and wiping dif- fers between end users and there is no universal standard procedure for doing this. As alcohol is not a sporicidal agent there is also the postulation that to remove spores a wipe procedure is essential. Thus transfer disinfection remains a major QA issue when dealing with aseptic manufacturing.

The aim of this study was to evaluate the most effective wipe systems used during aseptic manufac- turing to (1) remove, (2) kill and (3) to prevent transfer between surfaces of surface bacterial contaminants. Staphylococcus epidermidis (NCIMB 8853), Bacillus sub-tilis (ATCC 6051), and clinical isolates of methicillin resistance Staphylococcus aureus (MRSA; University Hos- pital of Wales, Cardiff, UK) were used in this study. Slope  cultures of Staph. epidermidis and MRSA were prepared from freezer stocks onto Tryptone  Soya  Agar  (TSA;  Ox-  oid Ltd, Basingstoke, UK). Secondary slopes  were  pre-  pared and incubated at 37°C overnight and washed with 5 ml   of   Tryptone   Sodium   Chloride   [TSC;   8Æ5 g   l)1 sodium chloride (Fisher Scientific, Loughborough, UK) and  1 g  l)1  Tryptone  (Oxoid)].  Working  cultures  were prepared  by  centrifuging  the  suspension   at   4200 g   for 10 min  and  resuspension  in  fresh  TSC.  Viable  counts were performed on TSA using the pour plate method.
Spores of Bacillus subtilis (ATCC 6051) were prepared according to BSEN14347 (Anonymous 2005). Spore sus- pensions  containing  1Æ23 · 109  spore  ml)1  were  main- tained in distilled water and stored at 4°C until used.