Microorganisms, too embarrassed to ask others about！（Part 14）

In this part, I would like to describe sterilization.

Sterilization is employed widely in the drug product and medical device industries. You may have already known the basics of sterilization as part of your job. Or you may be about to start engaging in sterilization activities or your company may be about to participate in sterile medical device businesses.

In this part, I would like to start my descriptions from the elementary level closely so that even the beginners can understand.

In the first part, I would like to outline sterilization and sterilization assurance. Then descriptions of sterilization of medical devices follow. In most cases of sterilization of medical devices, either of radiation, moist heat, or ethylene oxide is used. Therefore, I will describe these three in details.
In order to perform sterilization, we need hardware: apparatus. Designing and control of the process largely relies on the hardware. Therefore, actual handling and procedures will vary depending on the manufacturer and the model of the apparatus. In my articles, I will show you an example of sterilization control, but this is just an example thus not everything. It is important for sterilization control at your company to communicate with engineers of the apparatus's manufacturer. These engineers are very important partners in sterilization assurance. You need to build a good relationship with them for highly reliable sterilization control.

1. What is Sterilization?

I have already shown the definition of sterilization as follows:

1. the process of killing or eliminating all microorganisms on an object. Sterilization results in a sterile product.

2. a validated process used for a product free of viable microorganisms.

The important thing in sterilization is to make sure that the object/product is sterile. As long as you state that you performed sterilization, you will need to eliminate all those microorganisms. An expression, "99.99% disinfected" is not accepted. It must be 100% when you claim that you did sterilization. Therefore, strict control is required in plants for certain products such as drug products, medical devices, and food products for achieving the sterility. 

By the way, why is sterilization necessary? Let's focus on sterile medical devices and discuss necessity of sterilization for these devices.

Sterilization should be a strict practice. You will naturally need apparatus for sterilizing a medical device. The price may vary depending on the size and the specifications, but the apparatus alone should cost you tens of millions of yen (hundreds of thousands of dollars). Purchasing apparatus is not enough for sterilization. You also need to secure necessary utilities such as electricity, water, steam, gas, and compressed air, to validate that the apparatus works properly, and to establish a process which ensures that your product is sterile. Also, you need to design your product so that it can undergo the sterilization process and remains intact. Package must ensure sterility and bear deterioration over time. Having a sterilization step in your manufacturing process means you need to have additional staffs for operation, inspection, maintenance, and so on. If you employ ethylene oxide for sterilization, you cannot release the product immediately after sterilization. You must store the product and wait until the residual level falls below the predefined criteria. Outsourcing the sterilization step is an idea but sterilization will increase your manufacturing cost drastically in either way. Also, you will need to recall the product once a defect is found in integrity of the sterilization process or a packaging material.

Why do you have to spent so much money and effort to sterilize your products? The answer is that you need to ensure safety of the patients who use your product. Only 150 years ago, we didn't have the very basic concept such as sterilization or disinfection which now supports modern medicine, and doctors performed surgeries and treatments with their bare hands and unclean tools (and without anesthesia!). Everyone knows what happened as results. Many of patients who treated in such a way died of infection (sepsis) caused by the treatment. It was the common sense at that time that surgery was dangerous and painful, and that wounds always festered during the healing process. In the mid-19th Century, the concepts of hygiene control, such as sterilization and disinfection, was finally recognized, which made surgery much safer. Nowadays, we practically won't have any patients who end up with suffering from sepsis due to contaminating microorganisms derived from medical devices used. *

Sterilization of medical devices is a critical process in order to minimize the risks of causing potential contamination (infection with microorganisms) during use of the devices. Sterilization is mandatory as criteria for approval for certain medical devices. In such cases, sterilization is a legal requirement, and sterilization control that conforms to the standards is mandatory. It is also necessary for the manufacturer to prove that in the unlikely event of a postoperative infection or other problem, the cause is not the medical device used.

*Note: Infections associated with medical procedures still often occur.  This is due to the fact that patients themselves carry microorganisms, that doctors, nurses, and other people intervene in medical procedures, and that microorganisms are present in the treatment setting. There are a numerous number of microorganisms in a human body. They exist in the environment i.e. outside the human body, too. Since microorganisms are invisible, no matter how careful we are, contamination and infection by microorganisms can occur as long as there is human intervention.

As to sterilization of medical devices, we have ISO standards. We need to design our processes for designing and manufacturing sterile medical devices in compliance with the related ISO standards.

The major ISO standards are as follows:

ISO 11135, 11137-1,11137-2, 17665-1, 14937, 20857, 11607-1, 11607-2, 11737-1, 11138-1, 11138-2, 11138-3, and 11140-1.