Microbiological cultural methods

MIC depends on the complex structure of corrosion products and passive films on metal surfaces as well as on the structure of the biofilm. Unfortunately, electrochemical methods have sometimes been used in complex electrolytes, such as microbiological culture media, where the characteristics and properties of passive films and MIC deposits are quite active and not fully understood. It must be kept in mind that microbial colonization of passive metals can drastically change their resistance to film breakdown by causing localized changes in the type, concentration, and thickness of anions, pH, oxygen gradients, and inhibitor levels at the metal surface during the course of a... 

Regarding the components of bulk fermentation processes, the strain of the organism used to manufacture the drug substance for the clinical study should be compared with the strain to be used in commercial production. Strain identification includes microbiological, cultural, and biochemical characteristics. A comparison of the media composition and method of sterilization, sterilization parameters, and the pH of the medium after sterilization should be done. All fermentation stages, parameters, and conditions should be described in detail (i.e., temperature, pH) and documented. 

As the human population of the earth continues to grow and the resulting crisis in world food supplies becomes more critical, utilization of wood cellulose and cellulosic waste materials as sources of food for animals or even for human consumption may become imperative. Food processors already are experimenting with fermentation methods and treatments with cellulolytic enzymes as means to increase the nutritive value of wood and other refractory food materials or waste products. It is conceivable that cellulolytic enzymes produced in microbiological cultures could be ingested by man or other animals together with foods... 

On the other hand, contaminants are substances that have not been intentionally added to food. These substances may be present in food as a result of the various stages of their production, packaging, transport, or holding, or might result from environmental contamination. In this area, Palenzuela et al. proposed an excellent CE method for the detection of bacterial contamination. The method was based on the interaction of ions with biocolloids that allows for their reliable separation of eight different types of bacteria by CE in only 25 min—a dramatic reduction in the analysis time resulted (7 h of enrichment vs. the 24-48 h typically required by culturing methods) compared with classical microbiological analyses. 

When selecting a suitable test method, the predominant factor must be that it is applicable in practice. This means that already known and proven microbiological laboratory methods cannot be adopted without further modification. Thus, for example, the use of selective pure cultures, or of mixed cultures preadapted to the substrate in the case of specific problems, can give interesting results, without solving any problems closely related to the natural conditions in effluent treatment and surface waters. 

Culture-dependent methods to characterize antibiotic resistance in the environment are essentially based on the guidelines developed for clinical and veterinary microbiology (e.g. [20, 66-69]). Nevertheless, several adaptations have been introduced. 

Figure 5. Effect of actinomycin D and cycloheximide on the induction of MnP activity. Mn-deficient cultures were grown for 4 days after which MnSO (180 //M) was added alone (triangles), simultaneously with actinomycin D (50 //g/mL) (solid circles), or with cycloheximide (50 //g/mL) (open circles). Extracellular enzyme activity was assayed at the indicated intervals after the additions, by the ABTS method 13,32). (Reproduced with permission from Ref. 32. Copyright 1990, mencan Society for Microbiology.)...

Chapin, K., and M. Musgnug. Evaluation of Three Rapid Methods for the Direct Identification of Staphylococcus aureus from Positive Blood Cultures. Journal of Clinical Microbiology 41 no. 9 (2003) 4324-4327. 

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. 

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