Microbiological methods are used for detection of microbial organisms in processes and procedures that require a sterile environment free of microorganisms. The procedures in the pharmaceuticalindustry and in clinical research especially in areas where microbiological methods are needed to ensure quality, safety, and a clean environment.
Defects of traditional microbiological methods
Microbiological methods have traditionally relied on the cell culture in plate method, where samples are tested on culture plates. An example of one of the earliest traditional methods is gram staining used to discover the type of bacteria, whether gram positive or gram negative. Another example is the sterility test where the product (a pharmaceutical product for instance) is tested to destruction by heating to a temperature that can kill most microbes. Any abnormal result will be known only at the end where the product is not reusable or re-testable. Since all traditional methods require growing microbes on media and require scientists to manually examine them, these methods are time-consuming and labor-intensive. Such methods are also subjective because manual examination will not always be standardized and accurate.
Rapid microbiological methods have emerged as an alternative to traditional methods due to the latter’s defects and the former’s quick results. There are generally three types of RMM. They are qualitative, quantitative, and identification methods.
These methods are used to detect the presence of microorganisms in the product in quick time which indicates contamination. These methods can also measure other types of changes that signal microbial presence, such as a change in CO2 levels, change in pressure (headspace), etc. Polymerase chain reaction (PCR), flow cytometry, Adenosine triphosphate (ATP), and endotoxin tests are a few examples of qualitative RMM.
This type of RMM provides a numerical result which shows the number of microorganisms that are present in a given sample. PCR is again useful to provide quantitative results, but more commonly reverse transcription PCR (RT-PCR) is used. Digital imaging of samples to quantify microbial contamination is also being used more frequently in the form of tests such as direct laser scanning, light scattering, ATP bioluminescence, and autofluorescence tests.
These methods aim to identify the type of microorganisms detected in the sample. Some of these methods profile the detected microorganisms against a protein profile or ‘fingerprint’ to quickly determine their species. One such method is the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF). Although MALDI-TOF provides an inexpensive and fast method of testing, microbial contamination, its large outlay cost may be too expensive for smaller laboratories to utilize them. Other identification methods try to detect microbes by profiling against a particular gene or genetic material such as 16sDNA.
Adoption of RMM by pharmaceutical industry
With respect to adoption of RMM by the pharmaceutical industry, adoption has been slow mainly due to a perception that using RMM may lead to uncertainty in obtaining regulatory approval. This is actually untrue and is reducing rapidly since regulators are the ones leading the push for adoption of RMM over traditional methods.
Another concern among pharmaceutical players is that RMMs may reveal a higher degree of contamination than when using traditional methods and hence can result in rejection by regulatory agencies. But this concern can also be taken positively because pharmaceutical players will be forced to adhere to higher standards of preventing microbial contamination.