BS EN ISO 11737-1 is the standard for sterilization of medical devices. Microbiological methods. Determination of a population of microorganisms on products
BS EN ISO 11737 Part 1 specifies the requirements to be met in the determination of bioburden. The requirements are the normative parts of this part of ISO 11737 with which compliance is claimed. The guidance given in the informative annexes is not normative and is not provided as a checklist for auditors.
The guidance provides explanations and methods that are regarded as being a suitable means for complying with the requirements. Methods other than those given in the guidance may be used, if they are effective in achieving compliance with the requirements of this part of BS EN ISO 11737.
BS EN ISO 11737-1 specifies requirements and provides guidance for the enumeration and microbial characterization of the population of viable microorganisms on or in a medical device, component, raw material or package. NOTE 1 The nature and extent of microbial characterization is dependent on the intended use of the bioburden data.
BS EN ISO 11737-1 does not specify requirements for the enumeration or identification of viral or protozoan contaminants.
Furthermore, the requirements specified in this part of BS EN ISO 11737 are not intended to address the removal and detection of the causative agents of spongiform encephalopathies such as scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease.
Part 1 of BS EN ISO 11737 does not specify requirements for the microbiological monitoring of the environment in which medical devices are manufactured.
A sterile medical device is one that is free of viable microorganisms. International standards that specify requirements for validation and routine control of sterilization processes, require, when it is necessary to supply a sterile medical device, that adventitious microbiological contamination of a medical device prior to sterilization be minimized. Even so, medical devices produced under standard manufacturing conditions in accordance with the requirements for quality management systems (see, for example, ISO 13485) may, prior to sterilization, have microorganisms on them, albeit in low numbers. Such products are non sterile. The purpose of sterilization is to inactivate the microbiological contaminants and thereby transform the non-sterile products into sterile ones.
The kinetics of inactivation of a pure culture of microorganisms by physical and/or chemical agents used to sterilize medical devices can generally best be described by an exponential relationship between the numbers of microorganisms surviving and the extent of treatment with the sterilizing agent; inevitably this means that there is always a finite probability that a microorganism may survive regardless of the extent of treatment applied. For a given treatment, the probability of survival is determined by the number and resistance of microorganisms and by the environment in which the organisms exist during treatment. It follows that the sterility of any one product in a population subjected to sterilization processing cannot be guaranteed and the sterility of a processed population is defined in terms of the probability of there being a viable microorganism present on a product item.
Generic requirements of the quality management system for design and development, production, installation and servicing are given in ISO 9001 and particular requirements for quality management systems for medical device production are given in ISO 13485. The standards for quality management systems recognize that, for certain processes used in manufacturing, the effectiveness of the process cannot be fully verified by subsequent inspection and testing of the product. Sterilization is an example of such a process. For this reason, sterilization processes are validated for use, the performance of the sterilization process is monitored routinely and the equipment is maintained.
International Standards specifying procedures for the validation and routine control of the processes used for the sterilization of medical devices have been prepared (see, for example, ISO 11135, ISO 11137 series and ISO 17665). However, it is important to be aware that exposure to a properly validated and accurately controlled sterilization process is not the only factor associated with the provision of assurance that the product is sterile and, in this respect, suitable for its intended use. Furthermore, for the effective validation and routine control of a sterilization process, it is important to be aware of the microbiological challenge that is presented in the process, in terms of number, characteristics and properties of microorganisms.
The term bioburden is used to describe the population of viable microorganisms present on or in product and/or a sterile barrier system. A knowledge of bioburden can be used in a number of situations as part of:
- Validation and revalidation of sterilization processes
- Routine monitoring for control of manufacturing processes
- Monitoring of raw materials, components or packaging
- Assessment of the efficiency of cleaning processes
- An overall environmental monitoring programme.
Bioburden is the sum of the microbial contributions from a number of sources, including raw materials, manufacturing of components, assembly processes, manufacturing environment, assembly/manufacturing aids (e.g., compressed gases, water, lubricants), cleaning processes and packaging of finished product. To control bioburden, attention must be given to the microbiological status of these sources.
It is not possible to enumerate the bioburden exactly and, in practice, a determination of bioburden is made using a defined method. Definition of a single method for use in the determination of bioburden in all situations is not practicable because of the wide variety of designs and materials of construction of medical devices. Nor is it possible to define a single technique to be used in all situations for the removal of microorganisms in preparation for enumeration. Furthermore, the selection of conditions for enumeration of microorganisms will be influenced by the types of microorganism likely to be present on or in medical devices.
Contents of BS EN ISO 11737-1 contain
- Normative references
- Terms and definitions
- Quality management system elements
- Management responsibility
- Product realization
- Measurement, analysis and improvement — Control of nonconforming product
- Selection of product
- Sample item portion (SIP)
- Methods of determination and microbial characterization of bioburden
- Determination of bioburden
- Microbial characterization of bioburden
- Validation of method for determining bioburden
- Routine determination of bioburden and interpretation of data
- Maintenance of the method of determination of bioburden
- Changes to the product and/or manufacturing process
- Changes to the method of determination of bioburden
- Revalidation of the method of determination of bioburden
- Guidance on determination of a population of microorganisms on product
- Guidance on methods of determination of bioburden
- Validation of bioburden methods
- Relationship between this European Standard and the Essential
- Requirements of EU Directives 90/385/EEC concerning active implantable medical devices, 93/42/EEC concerning medical devices and 98/79/EC concerning in vitro diagnostic medical devices