Putting Disinfectants Under A Microscope
Microbial Solutions
Joan O'Malley

Putting Disinfectants Under A Microscope

How and why companies need to be preemptive about performing disinfectant efficacy studies

We all know how unpleasant it can be killing germs in bathrooms and kitchens. Companies that manufacture and test pharmaceutical products face the same challenges. If anything, the work is even harder and more critical as contaminated products can easily erupt into a public health and public relations nightmare. (Witness the case at the now defunct New England Compounding Pharmacy, where tainted steroid medications sparked an unprecedented fungal meningitis outbreak that killed 64 people and sickened over 680 others.)

To prevent events like this from happening, companies employ a range of sanitizers, sporicides and disinfectants to kill, inactivate, remove or at least reduce certain deadly microorganisms to levels acceptable by the relevant international standards. But one area that sometimes gets overlooked is adequately qualifying the disinfection agents and procedures used in sterile suites and other critical areas; in other words, vetting products (e.g. quaternary ammonium compounds, aldehydes, chlorine and sodium hypochlorite, hydrogen peroxide, etc.) and procedures that we rely upon to help keep our pharmaceuticals and medical devices free from contamination.

Disinfection qualification studies are a kind of biological white-glove test designed to measure how capably products and procedures minimize the threat of microbial contamination. The Pharmacopeial Convention, the FDA and implementers of the EudraLex (the EC legislation governing medicinal products) are increasingly focused on making sure that manufacturers of pharmaceuticals and medical devices not only qualify the disinfection agents and procedures used in these clean environments, but that they also provide specific guidelines on how they want the efficacy tests to be performed.

Disinfectant efficacy tests are typically carried out using a suspension method and or surface method on non-porous surfaces described below.

  • Suspension method: Inoculating a liquid disinfectant with a fairly high concentration of a known microorganism, removing samples of the liquid substance after a pre-determined period of time, neutralizing it and seeing how the concentration of “surviving’ organisms compare to that of an untreated sample acting as the control.   
  • Surface test method:The test method closely simulates the practical conditions of application. The chosen conditions (contact time, temperature and organisms on surfaces (i.e. coupons)) reflect the parameters which are found in practical situations as supplied by the client.

Pre-saturated or impregnated towelettes when used as a hard surface method can also be evaluated for antimicrobial activity.

Some suppliers of disinfectant products do their own suspension tests and supply the data to their clients, who unfortunately often take it at face value. Rather than conduct their own preemptive study, companies often wait until a problem occurs in their facility or worse, when regulatory audits flag deficiencies in Good Manufacturing Practice (GMP).

During regulatory audits, inspectors scrutinize all of the company’s disinfection procedures used in GMP operations, particularly in clean (sterile) rooms, so companies have to be able to supply these agencies with efficacy data that supports claims that the disinfectants have been qualified (checked against in-house isolates.)

Whatever route a company takes to conduct these disinfectant efficacy studies, it’s important that the disinfectants, their concentrations and the surfaces included in the study match those being used in the facility. Consideration should also be given to the need for organic challenge to test the efficacy of the product in adverse conditions.

Even more important is the selection of the microbes used in the study. The microbial controls should be clinically significant, include the US Pharmacopoeia or other reference standard cultures and should include Gram-positive, Gram-negative, fungal and spore-forming organisms. It is imperative that one must include actual cultures isolated from the facility as part of the environmental monitoring program.

Some companies conduct their disinfectant efficacy studies in-house. However, if they don’t have the manpower, time, skill and expertise to do this it probably makes more sense to send their in-house environmental isolates to a contract lab for culture, storage and determination of population levels and analysis. Our facility has helped clients develop and execute disinfectant qualification studies specific to their facilities and methods and so we know, from experience, how difficult it can be to execute such studies properly. We have highly skilled operators trained and experienced in the conduct of these studies.   

In either case, being combat-ready against microbial forces goes a long way in protecting a company’s customers and bottom line. It pays to be preemptive.