Battling microbial contamination

Elaine Gemmell, head of regulatory affairs, InnoScot Health, writes about the need to implement comprehensive measures with increasing prevalence of microbial contamination. 

Since the COVID-19 outbreak, two key questions have arisen – how does it spread and how can we help to stop it?

Subsequently, the potential for transmission of disease by contamination in clinical settings has been placed under the spotlight.

During care, medical devices and instruments will encounter infected patients. With a lot of patients requiring advanced care during a pandemic, meaning one device could be used multiple times in one day.

To prevent transfer, reusable medical devices must be sterilised or thoroughly disinfected between use, particularly point of contact devices that are used at the bedside. 

The Medical Device Regulation replaced the Medical Device Directive in Europe in 2021, which reflects the importance placed on contamination control. The definition of a medical device now includes products specifically intended for the cleaning, disinfection, or sterilisation of devices. These were previously considered accessories. It is anticipated that this definition will be incorporated in new UK legislation. 

Low risk class I devices don’t usually require assessment by a notified body unless they have a measuring function or are sterile. The new regulation requires a notified body assessment of the processes required to decontaminate reusable surgical instruments. Future UK legislation is expected to mirror these requirements.

Part of the approval process considers the safety of devices with respect to microbial contamination. The extent of contact with the body and the invasiveness of the device will determine the level of cleanliness required. For instance, a device which is intended to contact intact skin is required to be clean whereas a device which is invasive and enters the body though a surgical incision will be required to be sterile. Devices intended to be reused will be reprocessed in accordance with validated processes provided by the manufacturer. 

There are several measures designed to heighten cleanliness and identify contaminants: 

Microbial testing

This detects the presence of microbial contaminants and may include identifying bioburden levels, presence of endotoxin, and methods for sterility assurance. 

Reusable devices

The manufacturer is required to provide reprocessing instructions to return the device to its original condition. This includes pre-cleaning processes and packaging to maintain the cleanliness level of the product. This process must be validated. The device must not be damaged by the process and continue to perform as intended by the manufacturer. In some cases, degradation of materials due to the cleaning process may limit the lifetime of the product. 

Decontamination

The type of decontamination required depends on the risk to the patient. High risk devices which are introduced into sterile body areas or contact a break in skin or mucous membrane require sterilisation. Medium risk devices which contact intact mucous membrane or are contaminated with virulent or readily transmissible organisms require disinfection. Low risk devices which only contact intact skin or do not come in direct contact with the patient require cleaning.

Cleaning

Cleaning can be achieved by mechanical or chemical processes. Mechanical cleaning requires a cleaning fluid and mechanical action. The action can be friction e.g., rubbing, brushing or ultrasonic agitation. Fluid is required to remove debris loosened by the mechanical action. Chemical cleaning requires detergent with added enzymes to break down proteins, fats, or starches. 

Sterilisation

Sterilisation may be achieved in several ways. Steam sterilisation uses high temperatures to kill microorganisms. Autoclaves are steam sterilisers and operate at temperatures more than 121°C.

Ethylene oxide sterilisation disrupts the cellular metabolism and reproductive processes of microorganisms. It is used when other methods of sterilisation are not appropriate since it does not expose devices to excessive heat, moisture, or radiation. Devices can be sterilised in final packaging.

Gamma or electron beam sterilisation effectively kills microorganisms and will not leave residue. The amount of radiation received depends on the type of product and its dose requirements. 

The market for detection and destruction of microbial contamination is growing, but devices also need to be tested and approved – a big challenge for medical devices with compliance needing to be rapidly achieved amid stringent regulations.

The pandemic has underlined the need for rapid detection of microbes and of releasing products faster and is an undoubted area of future opportunity.