Application of molecular biology in the detection pathogens and medical arthropods in Southern Vietnam

Some general information about molecular biology technology

Molecular biology is a part of biology; based on physiology, genetic and biochemical. Molecular biology studies about the shape, structure, and function of macromolecules that have important roles in the life, such as nucleic acids, proteins…. Molecular biology techniques are very diverse and also applied in many different fields, such as molecular diagnostics (PCR, molecular hybridization); production of active substances detecting or treating diseases (producing monoclonal antibodies, making proteins with biological activity ...); gene therapy (recombinant ...). The molecular biology applications which the earliest and most visible are the medical fields. Based on genetic engineering, medicine not only relies on clinical symptoms but also impacts to directly the true reason that cause the disease: genetic abnormalities. Molecular biology pervate almost the medicine field; inside, the most potents are diagnostic and preventive.

Historically, following the traditional methods, to determine the cause of the disease, the test will be did through direct or indirect methods, such as stain and examination specimen, chemical properties, culture, experimental disease, the presence of specific antibodies in the blood .... However, these techniques almost spend a lot time, and some cases, It is not only expensive but also low about the sensitivity and the specificity. An essential requirement for these techniques is that they require large amounts of microorganisms to be detectable under microscope or microorganism grown on artificial media. In fact, many cases have the low number specimens, or the bacteria died, or grow very slowly ..., the determination of these techniques encountered many difficulties, even impossible. Meanwhile, if the application of molecular biology techniques, the results of microorganisms will be faster, many cases will be cheaper. In particular, these techniques give high sensitive and high specificity. In addition, molecular biology techniques can also reveal the mechanisms of microorganisms by determining the presence of genes that regulate the microbial activity microorganisms and indirectly indicate their 'pathogenic mechanisms' or the resistance drug of microorganisms will also be identified. Beside, sequencing a nucleotide fragment and comparing on the gene bank, can give information that microorganism has been studied or is a microorganism that is unknown.

In addition, molecular biology techniques have not only characteristics of accurate and fast results but also very convenient which difference sample such as blood, faeces, phlegm, urine ... contribute to the task of caring and protecting people's health is better and better.

Application Molecular Biology technique in Institute of Malariology -Parasitology - Entomology in Ho Chi Minh City (Impe HCM)

With the current trend , the Impe HCM has applied molecular biology techniques in pathogen testing and vector control in the management Institue such as malaria, helminths, pathogens on vectors ... to provide the National Program with the necessary data on disease prevention.

Research subjects applied molecular biology techniques in IMPE HCM are very diversity, depending on the purpose example pathogens or vectors, we will collect different types of samples, such as blood samples for parasites, fecal samples for helthmin, external parasite ...

For pathogen testing

Applying the protocol of IMPE about Nested PCR, Real time PCR and LAMP techniques to amplify the target genome for malaria parasites, the helminth such as tapeworms, the Ricketsia in the external parasite… . Thereby, databases have been provided to having the prevent plan to control the specific disease.

With agents that have low density in sample, molecular biology techniques have found infection rates higher than traditional techniques. In a study of active case detection (ACD) in the high risk malaria area in 2015, the Nested PCR technique detected infection rates to 14.7% compared with 0.7% the parasite be detected by RDT. Another study in 2017, with Real time PCR, detected 4.4% parasites compared to 0.52% of RDT-detected parasites.

Also in 2017, the Institute also detected 4.43% parasite prevalence rate by LAMP technique compared to 0.5% parasite detected by the traditional method with the same sample collected in the field.

In the investigation of pathogens on external parasite in the South Vietnam - Lam Dong, a 2015-2017 study, on pathogenic parasites including ticks, mite, chigger mite has been tested for Ricketsia bacteria cause fever, the results showed that the rate of 1.57% positive for DNA with O. tsutsugamushi.

For identification medical arthropods

IMPE HCM has also successfully established a protocol to identify species of external parasites such as ticks, mites, chigger mites, etc. by PCR and sequencing.

In a study from 2015 to 2017, the Institute used PCR techniques and sequencing to identify vector such as ticks, mites, chigger mites. The research showed that identification medical vectors by molecular biology techniques in Vietnam has not been applied much, so that provide a general view to further research into identification by genetics for external parasite in Vietnam.

The experience lesson

- To detect the rate prevlence malaria parasite by PCR, real time PCR, compared result with the traditional method shown that about 3,91% to 14% parasite omitted if not apply the molecular biology to detetct. With the LAMP technique, which have the threshold less than the PCR , have the sensitive and specificity higher than traditional technique ( such as RDT, Giemsa..) and can apply this method in the field. This difference may be caused by the high threshold of Giemsa and RDT, while this community belong to the high risk malaria area, persistent malaria, the asymptomatic patient carry out low density parasite, the people in this community have immune response who can’t detect by Giemsa and RDT.

- Tests to find the prevelence rate of Ricketsia bacteria (caused scrub typhus) in external parasites, have not been published in Vietnam yet. The research report that the medical arthropods have pathogens and this can be a source of disease causing diseases affecting people's health.

- For external parasites, the results of gene identification, sequencing of ticks, mites and chigger mites are initially to give an overview of the identification external parasites in the south of Viet Nam compare the worl. This reaearch is also the premise for further research into the specific identification ticks, chigger mites and mites in Vietnam both morphologically and genetically. And in the future, we need construct specific gene sequences on the external parasite, that is confirmed by morphologically in VietNam, can be published in the Gene Bank.

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