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Published on 1 January 2006

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Cleanroom disinfectant selection process


Georgina Froud
Communications Manager
Shield Medicare

Within the hospital environment, cleanliness is of utmost importance, and nowhere is more critical than in the pharmacy production area, where intravenous drugs or
parenterals are made for patients.

While hospitals in many European countries have found it difficult to adopt good manufacturing practice (GMP) standards fully, often because of budget constraints or resistance to change in working methods, many are seeing both the need and the benefits of controlling contamination. There is no doubt that increased pressure will come to bear on hospitals to conform to these guidelines, and the selection of the correct sterile disinfectant is a fundamental element.

Efficacy, performance and assured sterility are essential for controlling contamination. Current GMP (cGMP) states that “disinfectants in Grade A and B cleanrooms should be sterile prior to use”.(1)

Selection should not be left to chance, but should be made on the basis of:

  • An environmental survey of the facility and historical environmental data.
  • An understanding of the chemistry of disinfection.
  • Efficacy data supplied by the manufacturer and in-house generated.
  • Compliance with standard testing procedures.
  • Quality control, documentation and certification.
  • Performance in terms of ease of use and speed of action.
  • Health and safety.

The following case is an example of a recently conducted selection and validation process by a well-known major pharmaceutical facility in Europe, and their experience is relevant to any organisation operating cleanroom environments.

This facility was undergoing expansion of its manufacturing areas with a brand new Grade B cleanroom. The company was unhappy with the established disinfection protocol, and the microbiologist was under pressure to initiate a change, mainly on the basis of health and safety, but also because the existing contamination control procedure incurred lengthy lost production time. They had already been criticised in an FDA audit for not undertaking independent evaluation of their current disinfectants by standard methods and against facility isolates.

Current disinfection protocol
The procedure historically used by this facility was three weeks of using an amphoteric disinfectant at 0.5% v/v concentration and then, on week four, 1% v/v concentration of a formaldehyde/glutaraldehyde/quaternary ammonium compound mixture. When there were conditions of heavy soiling, the formaldehyde/glutaraldehyde/quaternary ammonium blend was utilised by fogging at a concentration of 8% v/v. This is much higher than the recommended 3% v/v because it was found to be ineffective against the Bacillus licheniformis isolate. The fogging process was costly in terms of production time and presented a considerable health hazard. Extensive rinsing was also required between the rotational products, because a sticky residue was being generated. The process of agreeing a new disinfection policy was divided into four steps.

Environmental history
Air and surface testing of an aseptic area is required under GMP. This information identifies the organisms present in the various areas of the aseptic manufacturing environment.

In this facility, the historical environmental data indicated routine observation of a Micrococcus species, Staphylococcus epidermidis and two Bacilli species, one of which appeared to be the particularly resistant B licheniformis. No moulds or fungi were observed.

Prime requirements from a disinfectant
Armed with the environmental information, the facility formulised the points they required of a disinfection protocol and what their ideal would be. Their requirements included:

  • A rotational system.
  • One of the rotations including a sporicide.
  • Safety for their operators.
  • Residues and compatibility of materials.
  • Ongoing manufacturer’s support.

What choice does the microbiologist have?
A shortlist of three rotational combinations was drawn up for further consideration:

  • The current disinfectants: an amphoteric and formaldehyde/glutaraldehyde/quaternary ammonium compound.
  • A rotational pair consisting of acid and alkaline phenolics, with occasional use of a hydrogen peroxide/peracetic blend as a sporicide.
  • A rotational pair consisting of a quaternary ammonium compound blended with a biguanide, and stabilised chlorine dioxide blended with a quaternary ammonium compound (this being a sporicidal substance).

Details of the chemistry and efficacy of these agents are shown in Table 1. The inclusion of a sporicide was important to this company. The advantage of the stabilised chlorine dioxide/quaternary ammonium blend is that it is very fast-acting and can be used at concentrations that are safe to handle. Thus, it could be used on a routine basis with little loss of production time.


In option 2, the peroxide/peracetic agent was found to be expensive and could only be considered for use on an occasional basis. Therefore, three agents would have to be approved. The formaldehyde/glutaraldehyde blend was considered to be harmful to the operators, and the company aimed to stop using the product.

Further technical information was requested from the manufacturers, and they found that the presentation of the material was of variable quality; in some cases, it was difficult to extract the relevant data. Technical information should include:

  • Product specifications.
  • Examples of certificates.
  • Sterility assurance.
  • Material safety data.
  • Raw materials specification.
  • The production process.
  • Validation.
  • Efficacy.
  • Residues.
  • Materials compatibility.

All shortlisted options were evaluated in-house to assess their effectiveness and ease of use. By far the most popular combination was option 3, the stabilised chlorine dioxide/ quaternary ammonium blend and the quaternary ammonium/biguanide blend. This option was considered to be much safer and more pleasant to handle than some of the other disinfectants available. A sporicide was part of the rotation, unlike option 2, which required an additional agent. Their preference was to move away from fogging, and this could be achieved with option 3. Elimination of fogging would significantly reduce lost production time.

The disinfectants were tested against European standard methods: EN1276 and EN1650. These are both suspension tests, carried out with an interfering substance of bovine serum albumin.

Under the conditions of EN1276, the disinfectant must demonstrate at least a log 5 reduction against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Enterococcus hirae. The contact time for the test was five minutes at a temperature of 20(˚)C.

To be considered fungicidal, the conditions of BS EN1650 require demonstration of at least a log 4 reduction against Candida albicans and Aspergillus niger. The test contact time was 15 minutes at a temperature of 20(˚)C.

The facility isolates submitted were identified as Micrococcus species, Staphylococcus epidermidis, Bacillus cereus and the resistant B licheniformis.

Against the referenced strains, the disinfectants achieved the required log reduction in viable count in five minutes. A log 5 reduction was also achieved against Micrococcus species and S epidermidis isolates.

At the time of testing, there was no European standard for determining sporicidal activity. However, considered opinion suggested that, for a disinfectant to be considered sporicidal, it should achieve a greater than a log 3 reduction within 15 minutes at 20(˚)C and in the presence of 0.3g/l bovine albumin in suspension. The Bacillus species were tested under these criteria but with a contact time of only five minutes. A log 3 reduction was achieved under these conditions.

The test clearly indicated not only that the product consisting of a stabilised chlorine dioxide blended with a quaternary ammonium compound was an extremely effective sporicide but also that it became effective quickly and at concentrations that presented no hazard to the operators.

Current testing scheme
At the time this study was carried out, there was no published European surface test method. The EN testing programme has now been extended to include a suspension test for spores (EN13704). There is now a surface test that can be used for bacteria and fungi/moulds, EN13797, but still no surface test for sporicidal activity. A testing programme should now include surface testing, as well as the suspension tests mentioned above, as it gives a more accurate representation of how the product would be used in practice.

Having received a comprehensive test report and considered all the issues, the pharmaceutical facility concluded that option 3 was the most effective – namely the rotational pair consisting of a quaternary ammonium blended with a biguanide and stabilised chlorine dioxide blended with a quaternary ammonium compound.


  1. Eudralex. Volume 4, Good Manufacturing Practice, Annex 1 – Manufacture of Sterile Medicinal Products, 38.

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