Sterilization biological monitoring

List of parameters (Shelf-to-Shelf Temperature Uniformity, Steam Sterilization Study — Shelf Monitoring, Steam Sterilization Study — Chamber Monitoring — Last 15 minutes of Exposure, Steam Sterilization Study — Eg Minutes, Steam Sterilization — Biological Indicator Test Results, Leak Rate Test, Vacuum Pump Down Test) Acceptable Limits, and Study Results... 

Pinto, T.J.A. Saito, T. lossif, M. Ethylene oxide sterilization III—influence of carrier nature in a biological monitor performance. PDA J. Pharm. Sci. Technol. 1994, 48 (3),... 

Sterilization by exposure to ethylene oxide is bounded by at least four variables gas concemratton, time of exposure, temperature, and humidity. It is also affected by product design, packaging design, and the composition of packaging materials. The shape, size, and materials of construction of individual sterilizers, the location of gas entry ports, and the presence or absence of forced circulation may all influence sterility assurance. There is no theory to describe these interactions. Validation and routine control of ethylene oxide sterilization processes boils down finally to the integration of all of these variables by reference to biological monitors. 

The first of these is where to place the microbiological monitor in the product. The ruling is that it should be placed in the location most difficult to sterilize. To some extent this is a reflection of professional judgement. It is a curious anomaly that most ethylene oxide sterilizers of hypodermic products judge the most difficult position within the product to be between the two lands or ribs of the plunger tip because this is an enclosed cavity. However, at the same time, it is also the location where ethylene oxide is most likely to persist longest because of its preferential absorption into rubber. The location most difficult to sterilize may not be amenable to placement of biological monitors. In these circumstances it is usually recommended to use some other product or device packed in a similar or identical manner to simulate the actual product. 

Pattinson, D. H. (1986). Rehumidification of biological indicators. In Proceedings of EUCOMED Workshop on Biological Monitoring of Sterilization. Kerkrade, Netherlands, April 21-23, 1986. 

Biological indicators for steam sterilization utilize bacillus stearothermophilus. In monitoring industrial cycles, a sufficient number of preparations each having a known degree of resistance are added to the load and retrieved after exposure, and cultured. 

Monitoring of the sterilization process canbe achieved by the rrse of physical, chemical or biological indicators of sterilizer performance. Such indicators are frequently employed in combination. 

Table 23.2 Biological indicators for monitoring sterilization processes ...

The USP also recommends the use of biological indicators, whenever possible, to monitor all sterilization methods except sterile filtration. Biological indicators are generally of two types. If a product to be sterilized is a liquid, microorganisms are added directly to carefully identified representative samples of the product. When this is not practical, as with solids or equipment to be sterilized, the culture is added to strips of filter paper. The organism chosen varies with the method of sterilization. 

A typical ETO sterilization cycle is shown in Fig. 10. As discussed at the beginning of this section, it is important to determine and monitor the bioburden level of the product entering the sterilizer. Also, the load configuration in the sterilizer is important in achieving uniform and reliable sterilization. Unfortunately, commercially available biological indicators used in ETO sterilization are often unreliable. Hopefully, progress will be made in this field in the years ahead. 

Based on these chemosensors, biosensors can be set up such as glucose or H2O2 sensors. In this case the appropriate biological compound (glucose oxidase or catalase) must be immobilized on the chemosensor. Different optical sensors are also used as transducer elements for the production of biosensors, especially of immuno-sensors. Here the affinity component is immobilized on the tip of the fiber and all available immuno-sensing assays can be performed using this transducer element. Since these sensors cannot be sterilized and used for on-line monitoring in a bioprocess we refer to other publications [25-27]. 

Institute a documented monitoring system primarily relying on biological indicators, with lesser reliance on end-product sterility testing. 

Assay methods for monitoring any degradation products may be used to justify the time limits for bulk storage. This time would include the period from when the product is formulated to the end of the filling operation. Because most lyophilized formulations do not contain a biological preservative, microbiological quality before sterilization by filtration must also be monitored. The unfiltered solution bioburden would include microorganisms and endotoxin levels. 

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