Consequences of microbial contamination

The consequences of microbial contamination have been classified into five categories (1) problems caused by the physical presence of microbial growth, (2) problems caused by microbial metabolism, (3) problems caused by microbial metabolites, (4) problems caused by contact with sludge and (5) microbially induced corrosion. These problems are pertinent for aircraft, marine vessels, road vehicles and ground fuel storage. 

Under most conditions, the contact time between the fuel and microbial contamination in the water bottom phase is too short and too limited for chemical changes to occur in the fuel (Herbert et al., 1987). There is a high volume of fuel to water and the fuel is deficient in the essential nutrients needed for microbial growth. The microorganisms for the most part are limited to the relatively small area of the water bottom and the fuel/water interface. However with prolonged fuel storage, especially in a poorly maintained storage tank, the fuel chemistry could be affected. 

---

Biogenic amines can be found in processed meat products as a consequence of microbial activity related to the fermentation involved in their processing, but amines can be also found in poor-quality raw materials as a consequence of microbial contamination. Therefore the BA content in cooked meat (not fermented) products might serve as a useful indicator of the hygienic quality of the meat employed for its elaboration. However, this relationship for ripened meat products is rather complex, since the ability to produce BAs of the fermentative microflora need to be well known before limits can be set. According to the few studies performed on BAs in meat products,... 

The spoilage of medicines as a result of microbial contamination, although obviously undesirable, has as its main consequence financial loss rather than ill health on the part of the patient. The other major problem posed by microbial contamination of medicines, that of the risk of initiating infection, although uncommon, is far more important in terms of risk to the patient and possible loss of life (Chapters 7 and 16). Infections arising by this means also have financial implications, of course, not only in additional treatment costs but in terms of product recalls, possible litigation and damage to the reputation of the manufacturer. 

Antibiotics are required to prevent microbial growth consequent to accidental microbial contamination. Supplemental serum (often bovine or fetal calf serum, or synthetic serum composed of a mixture of growth factors, hormones and metabolites typically found in serum) is required as a source of the often ill-defined growth factors required by some animal cell lines. 

Although such reactions and the consequences with respect to contaminant fate have primarily focused on soluble humic materials (Carter Suffet, 1982 Madhun et al., 1986 Traina et al., 1989 Morra et al., 1990 Puchalski et al., 1992 Engebretson von Wandruszka, 1994), the participation of microbial products in similar reactions is possible. Dohse and Lion (1994) showed that extracellular bacterial polymers enhanced the transport of phenanthrene in sand columns. The mobilization of contaminants might be beneficial to bioremediation if degradation reactions are not inhibited and substrate bioavailability is increased. Conversely, increased contaminant transport may increase the potential for contaminant movement and likewise the extent of environmental contamination. 

In natural environments, surfaces have often been found to be major sites of microbial activity (13). However, reduced substrate utilization rates have been observed for substrates sorbing onto a solid phase (14). This reduction is probably a consequence of decreased substrate concentration in solution. Much has been learned in recent years individually about microbial transformation of HOCs in soil and in the subsurface and about the processes of NAPL contaminant behavior in soil and aquifer materials. However, comparatively little is known about the combined effects of desorption-solubilization and microbial degradation on HOC fate and transformation (14, 15). 

The USP describes two general methods for conducting the test the direct transfer, or direct inoculation, method and the membrane filtration method. As the name indicates, the direct inoculation method involves the aseptic transfer of a sample of test product solution into the sterility test growth medium. To use this method, it must first be demonstrated that the product solution itself does not inhibit the growth of typical indicator microorganisms specified in the USP method. It should be self-evident why it is important to perform testing to negate the chance of product inhibition of possible microbial contaminants, as this is the purpose of the sterility test. The direct inoculation method, while not theoretically complex, requires the utmost technical precision and aseptic manipulation techniques for proper execution. As a consequence of the repetitive motions involved, it is prone to human error. 

---