Putting disinfectant to the test: Designing a field trial


Cleaning and disinfection is a process that can become very elaborate in cleanrooms. Tim Sandle in conjunction with Ecolab Life Sciences discusses designing a thorough and reliable field trial to test this process

Putting disinfectant to the test: Designing a field trial

Cleaning and disinfection are critical steps for achieving pharmaceutical facility contamination control and an important point of environmental control, as captured in the recent revision to EU GMP Annex 1. The frequency and application of detergents and disinfectants is just as important as knowing that they are efficacious, and this is established through efficacy testing. However, there is no guidance for the final aspect of efficacy testing to prove that the disinfectant works in the cleanroom, the 'field trial'.

Disinfection refers either to the inactivation or destruction of microorganisms. To be effective, pharmaceutical-grade disinfectants need to be validated against international standards (commonly either US or European norms). The validation process is typically a joint approach between the disinfectant manufacturer (who will, as a minimum, perform the basic suspension test) and the user (who will undertake surface efficacy testing). Ecolab Life Sciences uses the Validex methodology, where there is a comprehensive data set looking at common cleanroom isolates against typical pharmaceutical facility surfaces.

One point of commonality is that personnel are a variable that is hard to control

The final stage of disinfectant efficacy testing is the field trial. This is where the disinfectant(s) under qualification are studied during in-use conditions in facility cleanrooms. As disinfectants are used in rotation and they are affected by different factors, all variables need to be captured in the field trial. The challenge for many users is that the field trial has not been standardised (there is no European standard in existence, for example). Nevertheless, the importance of field trials is referenced as part of the hierarchy of European Standards (phase I basic screening [suspension] tests, phase II suspension and surface tests, phase III field trials) and in USP General Chapter of Disinfectants and Antiseptics <1072>. This reference means that conducting a disinfectant field trial is a regulatory expectation.

A field trial can apply to:

  • A new facility start-up
  • An existing facility, where one or both disinfectants are set to be changed
  • A retrospective study, where no formal field study has been performed

To aid facilities in drawing up a field trial, Ecolab together with the author, have drawn up a protocol for executing a field trial. This article outlines the basis for conducting such a trial.

Variables affecting performance

The principle reason why a disinfectant field trial is required is that the process of using a disinfectant in a cleanroom can be very different to assessing a disinfectant under laboratory conditions. Variables include:

  • Different numbers of microorganisms
  • Different types of microorganisms
  • Microorganisms in different physiological states
  • Different physicochemical forces binding microorganism to surfaces
  • Surfaces of different age and being subject to different degrees of abrasion
  • Variations in temperature, humidity and pH
  • Potential for soiling to remain, and soil of a different types used in efficacy studies

While robust, surface efficacy testing can provide a degree of confidence that the disinfectant is effective, the above variables are not easy to assess within the laboratory setting. Furthermore, the field trial needs to be conducted within each facility because the types of cleanroom vary; there are geographical variations with the types of microorganisms; and the cleaning techniques will differ.

One point of commonality is that personnel are a variable that is hard to control, and the field trial also examines how well personnel are using and applying disinfectants.

Objectives of a field trial

The reasons for running a disinfectant field trial are to show effective disinfection as part of overall environmental control, with environmental monitoring being the main assessment tool. Through undertaken targeted monitoring, a successful field trial can demonstrate:

  • That the microbial bioburden present before application of the disinfectant has been reduced post-application (if the disinfectant is a sporicide, special attention needs to be paid to spore-forming organisms).
  • That the activity of disinfection results in an acceptable level of bioburden when compared with environmental monitoring alert and action levels applicable to the cleanroom area.
  • That the application of the disinfectant to cleanroom surfaces results in a similar average bioburden level in relation to the other disinfectant used in rotation during the trial.
  • Difficult to clean and disinfect locations within the cleanroom can be effectively disinfected.

With environmental monitoring, the scope should be for surface samples only, using contact plates (and swabs, if appropriate). The agar used should contain an appropriate neutraliser. There is no value in taking air samples as part of the evaluation.

Designing the field trial

Before designing the field trial, it is important to ensure that all health and safety considerations have been covered. This includes putting in place a risk assessment; checking safety data sheet requirements; issuing personnel with suitable personal protective equipment; and putting in place a system to assess the occupational exposure levels.

The design of the disinfectant field trial should be outlined in a pre-approved protocol. The protocol will need to include the following actions:

Putting disinfectant to the test: Designing a field trial

Determining rotation frequency: Given that any field trial will need to include two disinfectants (even if only one of the disinfectants is changing), either the existing rotational pattern is used, or a new rotational pattern is required. As an example, this could be 3 weeks of disinfectant X, followed by one week of disinfectant Y, and then repeating.

Selecting cleanrooms: The number of cleanrooms to be used in the study will depend on the facility and the different types of operations and cleanroom uses. As examples, corridors will receive a high level of footfall; aseptic areas will be different to early-stage processing; wet areas will have different microorganism challenges; and processing rooms will present a greater product risk than non-processing areas.

Determining the number of samples to take: To develop a large enough data set for analysis, the number of samples should be a minimum of 100 or determined by statistical analysis for both disinfectant rotations.

Determining the trial run time: The length of time that the trial needs to run for needs determining. This should be sufficiently long so that the rotational pattern can be assessed more than once (otherwise the results obtained might be due to chance). To ensure data reliability, three rotational patterns or more are recommended.

Determining sampling times: In order to show the effectiveness of disinfection, the environmental monitoring samples should be taken prior to cleaning or disinfection and after cleaning and disinfection. Time limits need to be set for the 'before' and 'after' categories, so that the sampling times are meaningful in relation to the disinfection of the rooms. Surfaces should also be dry prior to sampling.

Setting the locations for monitoring: The locations for the surface environmental monitoring need to be set in advance and remain the same through the study. Locations should include both working height and non-working height surfaces; areas of high traffic; close to where product is processed; and some potentially hard to clean spots, such as underneath items of fixed equipment.

Disinfection technique: The disinfectant application techniques should be standardised in an SOP and consistently practiced by all cleaning staff. Cleaning using a detergent may be required prior to disinfection.

Sample incubation: Environmental monitoring samples need to be incubated at a determined temperature range designed to recover a range of cleanroom microbiota.

Data review

When reviewing the data from the field trial it is important to give equal attention to the counts obtained and the microorganisms recovered. While the ideal is no rise in typical microbial counts (especially rises above the action level) or even a decrease; the disinfectant could still be classed as ineffective if a high proportion of undesirable microorganisms are recovered. For example, Burkholderia cepacia complex organisms in a non-sterile facility or high levels of spore formers, especially when evaluating a sporidical disinfectant could lead to a disinfectant being classed as ineffective.

For counts recorded, the data should be subject to significance testing and a comparison made of alert and action level excursions. This involves ensuring there is no significant change with the new disinfectant compared with the previous regime.

If the field trial is unsuccessful, a thorough review is required looking at the different variables. A worst-case outcome will require a return to laboratory surface studies, in order to consider factors such as the contact time or targeted microflora.

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The disinfectant field trial represents the final step in the disinfectant qualification process and it is the most important, as the exercise provides real-world data to support the efficacy of disinfection within the facility - something that is assessed within the user's cleanrooms, using locally determined techniques and frequencies, and as assessed against the typical microorganisms unique to the facility. This article has presented why the field trial is important and some of the key aspects to consider and Ecolab can provide a more detailed field trial protocol.

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