Molecular Characterization of Orientia From Patients

By Manigandan C Manigandan

Scrub typhus is a zoonotic infection spread by vectors and can manifest as an acute febrile illness with a potentially severe outcome. The causative agent, Orientia tsutsugamushi, is an obligate intracytoplasmic bacterium that is transmitted by the larval stage of trombiculid mites. There are nymphal and adult trombiculid mites in the soil. There is only one life stage that can transmit the disease to humans. After a chigger bites you, you may develop an eschar, a type of lesion that may cause fever, headache, myalgia, nausea, vomiting, diarrhoea, cough, or breathlessness. Tsutsugamushi O., unlike many other bacterial pathogens, can only survive within a host cell, and thus it can only infect phagocytic cells. The organism also infects non-phagocytic cells, such as endothelial cells, fibroblasts, and phagocytic cells, such as macrophages and polymorphs. Scrub typhus is an important rickettsial infection, but is often under-recognized. Weitzel et al. estimate that more than a million cases are affected annually. Furthermore, over a billion cases are at risk for this febrile illness worldwide. Despite the availability of serological tests, they fail to diagnose typhus at an early stage due to insufficient production of antibodies and need for frequent follow-up tests. It can take at least a month for the results of the isolation of O. tsutsugamushi.
Thus, isolation in culture is not appropriate for the routine diagnosis of scrub typhus (Koh et al., 2010). There is still a possibility of missing out on the diagnosis, which is why there is a need for an alternative diagnostic method. PCR makes the DNA of the agent millions of times stronger. This means that O. tsutsugamushi DNA can be detected in blood and tissue samples with great sensitivity using PCR. The sensitivity of this assay has been enhanced by the development of the nested PCR (nPCR) assays, which are performed using two separate amplification steps. Several recent studies from India (Kumar et al., 2014 and Sinha et al., 2014) and elsewhere (Ruang-areerate et al., 2011 and Izzard et al., 2010) have shown that nPCR targeting the 56kDa type-specific protein gene is effective. The 56kDa gene is a type-specific protein antigen gene, which is specific to O. tsutsugamushi.
This protein has four hypervariable domains that are responsible for the antigenic variation (Blacksell et al., 2008). The 56kDa type-specific antigen (TSA) is a major outer membrane protein of the organism and is involved in penetration into the host cells. It induces strong humoral immunity. It contains both group-specific and type-specific epitopes, which may be useful for the diagnosis of scrub typhus. To diagnose typhus from the study population, we planned to target the 56kDaProtein antigen gene.

• Format: Paperback
• Language: English
• ISBN: 9927068913
• ISBN13: 9789927068911
• Release Date: December 2022
• Publisher: Aruna Publishing House
• Length: 166 Pages
• Weight: 0.51 lbs.
• Dimensions: 0.3" x 6.0" x 9.0"