Microbial contamination: potential sources

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. 

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. 

It is essential that emulsions are formulated to resist microbial attack, as this not only can affect the physicochemical properties of the formulation, causing color, odor, or pH changes and even phase separation, but may also constitute a health hazard. The potential sources of contamination can be from raw materials (especially if these are natural products), water. 

Materials for components of an HVAC system should be selected with care so that they do not become the source of contamination. Any component with the potential for liberating particulate or microbial contamination into the air stream should be located upstream of the final filters. 

The use of manure as a potential source of fertilisation should not pose particular problems in organic farming. It is also commonly used in non-organic farming and should not pose any particular problems with microbial contamination if carried out according to good practices. ... 

Validation of disinfectants should be concentrated on two aspects of their potential to create problems in aseptic manufacture. First, they may themselves be sources of microbiological contamination second, they may not be effective against microbial contaminants. 

Closed systems provide for complete separation between the environment in which personnel (uniformly accepted as the primary source of contamination in aseptic environments) are located from that in the materials are processed. Theoretically, if a sterile BPC could be processed in its entirety within closed systems, there would no possibility of microbial contamination. In marked contrast to the closed system is the open system , perhaps best defined by what it is not. Essentially, an open system lacks one or more of the features of a closed system, thus leaving it vulnerable to the potential ingress of contamination. One substantial issue associated with these definitions is establishing that a system remains closed over the length of the production campaign. 

Sources can only be generally linked to specific chemical or microbial contaminants and their potential effects on human and environmental health. The picture at local, regional, and national scales may be blurred by chemical contaminants, which appear in several categories (e.g., benzene or trichloroethylene which have been associated both with landfill leachates and leaking storage tanks). Also, natural biodegradation processes act on primaiy contaminants to yield transformation products (e.g., vinyl chloride and dichloroethylene from trichloroethylene or perchloroethylene). 

The potential for beer spoilage occurs prior to the production of wort (see below). Water supplies and all raw materials, as well as any exposure to air or surfaces that come into contact with wort or beer, may carry wild yeast, molds, and/or bacteria that may cause downstream processing problems. These sources can also be addressed in sensory programs if their key microbial contamination indicators are based on sensory perception. Air will also carry a multitude of microorganisms that are taken advantage of for spontaneously fermented beer production. 

Mixing vessels and storage tanks. Microbially contaminated vessels and bulk storage tanks, at either the manufacturer or the end user, may be an important source of potential infection. 

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. 

Personal items, such as coats, hats, rainwear, overshoes, umbrellas, and purses, do not belong in the laboratory. These articles should be stored elsewhere (491). Plants, cut flowers, aquaria, and pets of any kind are undesirable sources of yeast, molds, and other potential microbial contaminants of biological experimental materials (491). 

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. 

---