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Clinical detection of pathogenic microorganisms: the past and the future

A long long time ago people found out that some disease can be transmitted, but they did not know why or how, and thus imagined all kinds of magic reasons.。Only in the 17th century the invention of a microscope helped us to discover the existence of microorganisms. And thus, microbiological testing began.

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The initial microbiological detection was morphology-based. After the collection of a sample (e.g. sputum) there was a certain method of dilution, after which culturing the sample under certain conditions followed (such as: medium composition, culture time and temperature, a PH value, etc.), and then the final product would be observed under the electron microscope or microscope. Colony color, morphology and biochemical indicators were used to distinguish the microorganisms. This is a low-cost, classic method of microbial detection. In spite of its advantages, this method is also time-consuming, the workload is huge,some strain variations are difficult to distinguish. Therefore, this method was slowly abandoned with new advanced forms of detection.

As the enzyme systems as well as decompositions abilities of many substances of various microorganisms are not identical, thus the use of different metabolites produced by microorganisms can indirectly detect different enzymes, determine the presence or absence of these organisms. This is the application of biochemical methods for the detection of pathogenic microorganisms. Based on this discovery, immunological methods (specific antigen-antibody reaction), such as components and metabolites of microorganisms detected directly or indirectly by enzyme immunoassay, fluorescence immunoassay, radioimmunoassay, chemiluminescence immunoassay) can also be used to identify the presence of microorganisms. This method saves test time, improves test efficiency, and is the most commonly used rapid test for detection of microorganisms.

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In the fast river of time, the technology keeps on developing as well: nowadays, as the PCR technique is becoming common, new technologies are developed on the basis of it. For example, new generation fragment analysis technology uses PCR as a base, and then couples it with capillary electrophoresis to separate quantified pathogens of a particular sequence. Thus, pathogens and even pathogen subtypes can be distinguished. The method boasts both high sensitivity and high specificity. In addition, the classic technique can only detect one pathogen, whereas this technique can detect even above ten different pathogens in one time. Additionally, the technique can also quantify different agents tested. Therefore, the technology can identify cross-infection and quantitative information for clinical diagnosis and provide good guidance for treatment.

Even though we do not have massive attacks of horrible disease such as plague in the Middle Ages, there are still scary viruses out there: a strong example of it would be the SARS epidemic in 2003, or the raging Ebola. Also, the irrational use of antibiotics is resulting in bacterial resistance, coupled with a whole bunch of other complicating factors. Therefore, the development of pathogenic microorganism detection technology is still very necessary; the latest molecular biology methods, such as a new generation of fragment analysis for detection of pathogens, are very meaningful.

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