Broth fills

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. 

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. 

Broth fills should be a major part of the operational qualifieation of a new BPS machine to demonstrate aseptie processing capability prior to product manufacture (typically three sueeessful eonseeutive broth fills are required) and should be carried out at defined intervals thereafter. 

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. 

During the course of a broth fill, operator activity is as necessary as with routine manufacture. However, additional aetivities can be carried out to eover all permissible activities in order to provide evidenee that product sterility is not affected. Such interventions should be plaimed and documented for each batch. 

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. 

Broth fill data from various BFS users were studied in a survey carried out in 1998 by the Pharmaceutical BFS Operators Association. These results, together with some more recent data are shown in Table 2. 

It is clearly impractical to produce a very high number of broth filled units on a routine basis, but if unpreserved products are manufactured, it is good practice to fill broth directly following product batches with no further machine flushing or sterilization. 

The first step in the process is gasification of wood followed by conditioning and cleaning of the synthesis gas to give a mixture rich in CO and H2. The synthesis gas is sparged into a broth-filled tank fermentor where bacteria Clostridium ljungdahlii, for example) convert CO and CO2 to ethanol via the following two reactions ... 

The use of nutrient media that support microbial growth in trials to simulate aseptic operations (sterile media fills, "broth fills ) is a valuable part of overall validation of an aseptic process. Such trials should have the following characteristics ... 

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. 

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