Development of a quantitative real-time polymerase chain reaction assay specific for Orientia tsutsugamushi.
Two specific and sensitive polymerase chain reaction (PCR) assays were developed to detect and quantitate Orientia tsutsugamushi, the agent of scrub typhus, using a portion of the 47-kD outer membrane protein antigen/ high temperature requirement A gene as the target. A selected 47-kD protein gene primer pair amplified a 118-basepair fragment from all 26 strains of O. tsutsugamushi evaluated, but it did not produce amplicons when 17 Rickettsia and 18 less-related bacterial nucleic acid extracts were tested. Similar agent specificity for the real-time PCR assay, which used the same primers and a 31-basepair fluorescent probe, was demonstrated. This sensitive and quantitative assay determination of the content of O. tsutsugamushi nucleic acid used a plasmid containing the entire 47-kD gene from the Kato strain as a standard. Enumeration of the copies of O. tsutsugamushi DNA extracted from infected tissues from mice and monkeys following experimental infection with Orientia showed 27-5552 copies/microL of mouse blood, 14448-86012 copies/microL of mouse liver/spleen homogenate, and 3-21 copies/microL of monkey blood.
Jiang
Ju
J
Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland 20910-7500, USA. JiangJ@nmrc.navy.mil
Chan
Teik-Chye
TC
Temenak
Joseph J
JJ
Dasch
Gregory A
GA
Ching
Wei-Mei
WM
Richards
Allen L
AL
D000818:Animals; D000942:Antigens, Bacterial / Q000097:blood*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D008252:Macaca fascicularis; D051379:Mice; D012285:Orientia tsutsugamushi / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012612:Scrub Typhus / Q000382:microbiology; D012680:Sensitivity and Specificity
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial