Sources of microbial contamination

As previously mentioned, polymer dispersions when first produced are infrequently contaminated save, occasionally, with the spores of bacteria and mould fungi. It can therefore be assumed that the majority of spoilage microorganisms must gain access subsequent to the completion of the polymerisation reaction. When a major outbreak of contamination does occur, initial responses tend to centre on methods of wiping out the immediate problem. Identification of the source of contamination is considered as an afterthought, if at all. 

The sources of contamination are limited and many are generally within the control of the manufacturer (Gillatt, 1993) (Table 11). Realistic action taken to identify these sources, quantify the potential risk from each and reduce or eliminate the degree of contamination at that point can save a great deal of time and expense later. 

1 Water. Water is the main raw material in the majority of aqueous formulations, including polymer dispersions. However, the process water is unlikely to be a primary source of microbial contamination, as any microorganisms present tend to be destroyed in the reactor. Nevertheless, as mentioned above, some spore-forming microorganisms and yeasts can survive the polymerisation process and these have been isolated from fresh polymer dispersions soon after production. It is therefore necessary to ensure that process water is treated before its use. 

Process water may originate from a number of sources including  

The microbiological quality of process water will vary according to its source and is often treated before use. Chlorination alone may not be totally effective, especially if organic matter is present, when residual 

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As described in earlier sections, there are several potential sources of microbial contamination which can enter the paper mill. Once in the paper processing plant, other factors can then influence the degree of contamination. The conditions within a plant are very often extreme, with high temperatures and humidity arising from the process itself. Hence perfect conditions exist for other microbiological problems to develop. 

There are a number of main sources of microbial contamination (Table 2) of paints and other products that are affected by microbial contamination in the wet-state. 

Several guidelines are available in the literature for the pharmacist who must extemporaneously prepare an ophthalmic solution. The USP contains a section on ophthalmic solutions, as do other compendia and several standard textbooks. Since the pharmacist does not have the facilities to test the product, he or she should dispense only small quantities, with an expiration date of no more than 30 days. Refrigeration of the product should also be required as a precautionary measure. To reduce the largest potential source of microbial contamination, only sterile purified water should be used in compounding ophthalmic solutions. Sterile water for injection, USP, from unopened IV bottles or vials is the highest-quality water available to the pharmacist. Prepackaged sterile water with bacteriostatic agents should not be used. 

A recently published book provides an excellent survey of issues that relate to contamination with endotoxins (present in both viable and nonviable bacteria), their released cell wall constituents, and also viable bacteria in the pharmaceutical industry [1]. It is important to know both the content of the work environment (e.g., indoor air) and the pharmaceutical products themselves. The former provides information on possible sources of microbial contamination and the latter the purity of the final commercial product (or precursors in various stages in its preparation). In some cases it is vital to know the actual bacterial species involved in contamination culture-based methods are standard microbiological techniques which were the focus of Jimenez [1] and thus will not be discussed further. Any contamination (e.g., with endotoxins), regardless of the species of origin, is of utmost of importance (e.g., in determining the safety of a batch of antibiotics to be administered intravenously). This is determined optimally by non-culture-based methods. 

The major source of microbial contamination of controlled environments is personnel. Since the major threat of contamination of product being aseptically processed comes from the operating personnel, the control of microbial contamination associated with these personnel is one of the most important elements of the environmental control program. Personnel training should be conducted before the qualification and validation practice [13]. 

Table 1 Most likely sources of microbial contamination in aseptic processing ...

Furthermore, a microbial survey should be performed on all packaging materials that come in contact with the product to ensure the absence of microbial contamination. Attention must also be given to details during packaging operations. For example, on small-volume orders, bottle closures, or tips for plastic squeeze-spray containers are often placed on the product by hand. This procedure can be a source of microbial contamination unless operators use gloves that are sterilized and disinfected periodically during use. 

Equipment seals are often sources of microbial contamination, therefore, it is advisable to avoid their use, however where necessary, teflon sealing is preferred... 

Fats, oils, waxes. Water-free fats, oils or waxes are generally not a source of microbial contamination, as they lack the biologically-available water necessary for the proliferation of micro-organisms. This group of compounds are typically used in emulsions or re-fatting agents in surfactant systems. Antioxidants, added to retard oxidation and prevent rancidity, can potentiate the efficacy of certain preservatives (5.9.4.3./Antioxidants and... 

Another potential source of microbial contamination that could lead to poor performance of the machines are the additives. Low bacterial counts are essential in starch, retention polymers, slurries, coating color and size. 

Another possible source of microbial contamination of hydraulic fluids may arise from water intrusion if leaks in the hydraulic system occur or when make-up water is added to maintain the proper water content. 

Eliminate or control all known and potential sources of microbial contaminants by prompt cleanup and repair of all areas where water collection and leakage has occurred. 

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