UNDER CONSTRUCTION: MORE ISOLATES TO COME AND MORE DETAILS
There are at least 3 generally accepted prototypical strains of O. tsutsugamushi. These prototypical isolates include the Gilliam, Karp, Kato. The Karp and Gilliam strains were isolated in 1943 and 1944, during World War II. The Kato strain appears to have been isolated in about 1952. Given the importance of these isolates, information concerning the origins of the strains deserve some mention. Each isolate is given an individual subpage, below.
The Gilliam and Karp strains were among several strains cultured from cases of scrub typhus among military personnel in the Pacific region infected during World War II. U.S. Army medical staff became aware of the problems posed by scrub typhus when a significant number of personnel were affected in areas such as New Guinea, Assam and Burma. The first scrub typhus isolates were thus obtained from infected Americans (including infected medical personnel such as Alexander Gilliam). Other isolates in this group include the Kostival and Calcutta isolates.
In addition to the three prototypical strains, other isolates have become important because of their role in defining Orientia tsutsugamushi. These include especially the Kuroki, Kawasaki and Shimokoshi isolates from which 16S rRNA gene sequences were important in defining the genus. Also important because it appears to represent a significant phylogenetic subclade (as determined using the 56kDa type specific antigen gene) is the isolate TA763.
Subsequently, as research on scrub typhus expanded, additional strains were developed and analyzed. Some strains, such as the Boryong and Ikeda strains are important because they represent the first isolates for which an entire genome sequence was obtained. Molecular methods have greatly expanded the number of isolates being examined, but the original strains retain their importance, especially when it can be shown that many of them individually represent a significant subset of isolates from throughout the geographical range of scrub typhus.
Another aspect of the initial importance of many of the prototypical strains derives from mammalian host immune responses to these strains. In developing antisera for diagnostic purposes it was found that antibodies to each of the strains either do not overlap or only partially overlap. Thus antisera for diagnostic purposes could be developed and used to classify different patients infected with scrub typhus.
The history of individual strains is given on a series of associated pages. The prototypical strains include:
Additional strains for which history is provided include:
In addition to these protypical strains, other strains have become important. Their importance derives either from their place in the history of research on scrub typhus or on the recognition that they represent a significant subset of isolates that differ from the prototypical strains. These non-prototype strains include:
Ikeda, AFC3,
(additional strains are to be included as this site continues to develop).
A number of strains were isolated during or immediately after World War II. Karp and Gilliam strains are among these. There are other strains for which information is limited, and which have not been extensively studied. However, these strains still exist in some inventories especially the inventory at NMRC (Naval Medical Research Center) in Silver Spring, Maryland.
Among these “forgotten” isolates are the following:
(additional strains are to be included as this site continues to develop).
Other strains: Kostival, Boryong, Ikeda, AFC3, Kawasaki, Kuroki, Shimokoshi