Broth fills contamination

There is no appropriate defined sterility confidence level which can be translated directly into acceptance criteria for broth fill contamination for BFS processes. The most commonly recognized acceptance criterion is a sterility assurance level (SAL) of 10 although modem aseptic filling techniques such as BFS can achieve a higher SAL. This should be reflected by broth fill results and acceptance criteria for this advanced technology. 

During a more controlled study carried out within an environment artificially contaminated with high levels of individual nebulized spores of Bacillus subtilis [2], a level of contamination within the environment was achieved which led to the contamination of broth-filled units. The results were extrapolated to suggest a contamination rate of 1 unit in 4 X 10 with a smrounding environmental contamination of 1 cfu/ml... 

Extensive process simulation (broth fill) results for BFS effectively demonstrate that high levels of sterility confidence can be obtained with a properly configured and validated machine. However, in order to maintain high levels of sterility assurance, it is important that levels of microbial contamination are controlled within the filling environment. 

Broth fills should be earried out under conditions that are representative of those during normal operation. A deviation from routine processes should only be in the direction of presenting a higher rather than a lower challenge to the proeess. Due to the level of automation of BPS teehnology, it is extremely diffieult to take extra care in order to reduee the ehanee of container contamination during a broth fill, and results are therefore not as operator dependent as other less automated aseptie manufacturing processes. 

Por a new facility, some baekground environmental monitoring data are desirable. It is important that environmental monitoring data are obtained during the eourse of broth fill batches to demonstrate a normal level of environmental contamination. The validity of broth fills earried out in an environment of consistently lower contamination levels than those obtained during routine bateh manufacture eould be questioned. 

It can also be useful to retain and ineubate rejeet units filled during the course of a broth fill batch (again, excluding those that leak) for additional information. Again, these should be separated from aeeeptable units and labelled accordingly. Although such imits would be rejeeted during normal produetion, microbial contamination foimd in such imits may indicate a problem whieh requires attention. 

Prequency and size of broth fills must be clearly defined. The size of fill is usually based upon the statistical probability of detecting an acceptably low incidence of microbial contamination. Tables have been published to this effect [4], but the BPS operator has to decide both size and frequency of broth fills based upon their speeifie facility, routine product batch sizes, and operation. Por high speed BPS maehines used for filling routine produet batehes in excess of 100,000 units, broth fill batehes larger than traditional aseptic filling lines are both feasible and appropriate. 

The internal surfaces of broth filled units should be fully wetted to ensure capture of any contaminants within the broth. This is commonly achieved by agitation or inversion of the imits before or during the incubation period. 

It is recommended that at least 3000 units of production be induded in each broth-fill trial. The target should be zero growth and anything above 0.1% of units contaminated should be considered unacceptable. Any contamination should be investigated. Broth fills should be repeated at regular intervals, and whenever a significant alteration in the product, premises, equipment, or process warrants revalidation. 

The broth fill is a validation procedure that challenges both operator and facilities. The purpose of broth fills is to simulate routine aseptic operations in such a way as to produce broth filled units that can be tested for microbiological contamination. 

Continuous processes have an even better productivity, especially for slow fermentations. Their disadvantages are their sensitivity to contamination by unwanted microorganisms, and to accumulation of side products, which can interfere with the fermentation. In the continuous mode, the starting culture and medium are filled into the reactor and more nutrients are added continuously as the cells are growing. Part of the fermentation broth is removed at a suitable rate to keep the volume constant. All media must be sterilized before they enter the reactor, which can lead to problems during routine operation. 

Next, Pasteur examined the sick fermentation vats. Instead of yeast globules, he saw tiny, rod-like things cavorting in the broth, which instead of alcohol was filled with lactic acid. Pasteur managed to transfer some of the rod-like creatures into a clean container, and he went on to demonstrate that, when they are given appropriate nutrients, they multiply. The rods were alive, and they busily converted sugar to lactic acid. These microbes had contaminated the beet-sugar vats, killed off the yeast, and terminated the production of alcohol. 

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