article focuses on two important issues - maintaining a spore-free environment and preventing spore contamination from the use of disinfectants. Many experienced cleanroom operatives do not realise that alcohol does not kill spores and that a dedicated sporicide is needed.
Maintaining A Spore-Free Cleanroom
This article focuses on two important issues - maintaining a spore-free environment and preventing spore contamination from the use of disinfectants. Many experienced cleanroom operatives do not realise that alcohol does not kill spores and that a dedicated sporicide is needed.
The trouble with spores…
The control of bacterial spores is one of the most difficult requirements in a life science cleanroom. Spores can enter the cleanroom on people and on components at a surprisingly high rate. Annexe 1 of Good Manufacturing Practice (GMP) confirms that “Transfer of materials into and out of the unit is one of the greatest potential sources of contamination” 1.Research has shown that around 40% of consumables are contaminated with bacterial spores2. The same study also identified that if the transfer disinfection procedure employed was spraying with alcohol, only 27.6% of the spores would be removed.
Reduce initial bioburden
There are two ways in which initial bioburden and therefore risk of spores can be reduced:
Using a spray and wipe protocol has been shown to significantly improve the effectiveness of the transfer procedure 2. However, this can be time consuming.
Paper packaging should be eliminated where possible because, in addition to creating unwanted particulates, it harbours contamination and is difficult and time consuming to spray and wipe effectively.
Multi-packs of consumables in polythene packaging are an excellent way of achieving both these aims. As well as being paper free, they significantly speed up the transfer process as they are quick and easy to spray and wipe. They also reduce the amount of alcohol that needs to be used. Consider multi-packs for any bulk items, such as pens, waste bags, bins, swabs, needles and syringes.
Alcohol doesn't kill spores
The main problem with spores is their resistance to many of the standard disinfectants that are used. Traditional disinfectants, such as alcohols, quaternary ammonium compounds, phenols and amphoteric surfactants, are effective against bacteria in their vegetative state but useless against spores.
So what do we do if our environmental results show spores as one of the facility isolates?
Safe, effective solution
Biocides that have sporicidal activity, including aldehydes, hypochlorites and hydrogen peroxide/peracetic acid blends, are often toxic, irritant, corrosive, leave residues or need a long contact time. Many sporicides are oxidising agents and the environmental impact of using these in a cleanroom containing expensive equipment has to be taken into account. A review of the available corrosion data on materials used in cleanrooms, isolators and laminar flow cabinets should be a fundamental part of every validation programme.
However, a new sporicide has recently become available which is not as aggressive. Premier Klercide-CR Biocide B is an alcohol-free blend of a quaternary ammonium compound and stabilised chlorine dioxide. It is non-toxic, non-hazardous and non-corrosive, with a contact time of just five minutes to meet CEN standards.
Whilst efficacy is important, it is also crucial to consider the final specification of the sporicide. The user must ensure it can be transferred easily into the cleanroom and that it meets the required standards for sterility. Current GMP states that "disinfectants in Grade A and B cleanrooms should be sterile prior to use" 1.
Preventing spore contamination from disinfectants
Yes, FROM disinfectants.
In most cases, disinfectants are delivered by either trigger sprays or aerosols. Trigger spray systems offer significant advantages over aerosols and these include:
They have an adjustable nozzle so liquid can be dispensed as a jet or a spray
They are environmentally friendly as they contain no propellants
All of the liquid can be dispensed from a trigger spray, so there is no wastage.
However, there is a significant potential drawback with some trigger sprays, as contaminated air can be drawn back into the bottle, compromising the sterility of the liquid. Validation work in the licensed pharmacy unit of the Queen Elizabeth Hospital in Birmingham identified that a trigger spray alcohol, used to spray items into an isolator, had been contaminated with fungal spores only 8 hours after opening.
The unique SteriShield Delivery System solves this problem, providing the benefits of a trigger spray whilst guaranteeing the integrity of the contents.
The design operates as a closed system, preventing air being drawn back into the bottle and so eliminating the possible chance of contamination of the liquid. The liquid is held inside a medical grade bag within the bottle. All points of entry into the bag, including the dip-tube, are completely sealed, thereby creating the closed system.
To validate the system, rigorous testing was carried out at an independent laboratory3. The trigger spray was filled with nutrient broth and stored on the floor of a grade D cleanroom. Broth was dispensed through the nozzle to mimic in-use conditions and tested to show that the integrity of the trigger spray had not been compromised.
At each time point a negative control was tested, and a positive control to ensure that the broth had not deteriorated. Results show that the integrity of the sterile broth was maintained for six months.
So, to prevent spore contamination from the application of the disinfectant, use a fully validated trigger spray system.
If all these areas are acted upon then it should be possible to maintain a spore free environment in the cleanroom.
MCA: Rules and Guidance for Pharmaceutical Manufacturers and Distributors 2002.
Validation of liquid transfer disinfection techniques for transfer of components into hospital pharmacy cleanrooms: Hospital Pharmacist Sept 2001: MG Cockcroft et al.
Shield Medicare Technical Report Number TR0403R: Revalidation of the SteriShield Delivery System, Nov 2004.