OBJECTIVETo develop a real-time quantitative polymerase chain reaction(PCR) assay for detecting Rickettsia rickettsii.

METHODSThe primers and TaqMan-MGB probe were designed according to the ompB gene of R. rickettsii. A DNA fragment of ompB gene amplified from R. rickettsii by PCR was used as a standard template for the development of the method.

RESULTS5 copies of ompB fragments of R. rickettsii were detected. The genomic DNA of R. rickettsii was detected by the developed quantitative PCR assay. However, the genomic DNA from another rickettsial or bacterial agent was not determined. Through this developed method, the positive results were obtained from the animals and cells, artificially infected with R. rickettsii.

CONCLUSIONThe real-time quantitative PCR assay seemed to be highly sensitive and specific which might be used to rapidly detect R. rickettsia DNA in various samples and to early diagnose patients infected by R. rickettsii.

DNA Primers ; Humans ; Polymerase Chain Reaction ; methods ; Rickettsia rickettsii ; genetics ; Rocky Mountain Spotted Fever ; diagnosis ; Sensitivity and Specificity

OBJECTIVETo explore the existence of spotted fever group Rickettsiae (SFGR) in Guangdong province.

METHODSSera were tested to find the SFGR in population and host animals. The target samples were screened by polymerase chain reaction (PCR), and Rickettsiae was isolated with embryonated hen eggs and identified by serological tests.

RESULTSEight hundred and sixty people in natural condition and 321 of mice were determined. The mean positive rate of healthy population was 3.84%. To compare results among elected places, Fisher's exact test was applied. The difference was suggestive (P < 0.01), and there was no significant difference between mountain and plain areas. There was also no significant difference between mountain and plain areas (P > 0.05). Positive rate of mice was 4.67%, with Rattus fulvescens, Rattus edwardsi, Bandicota indica 11.59%, 12.90%, 3.13% respectively. It was the first time that SFGR antibodies in Rattus fulvescens, Rattus edwardsi, Bandicota indica were reported. A total number of 321 mice spleens and 394 ticks from the surface of mice body were collected. Two strains of SFGR, GDFK58-2000 and GDFK59-2000, were isolated in the ticks from the body surface of 2 Rattus fulvescens. They were identified as Rickettsia sibirica by serological tests. Five hundred thirty-three bp OmpA gene fragments of the two strains were cloned and sequenced. Compared with other relevant strains in Genbank, the rates of homology of nucleotide sequences of GDFK58-2000 and GDFK59-2000 and other Rickettsia sibirica strains were from 99.6% to 100%, and the homology of amino acid speculated was 100%.

CONCLUSIONIt has been proved that epidemic areas of north Asia tick-transmitted SFGR, did exist in Guangdong province confirmed by hostanimals, transmission vectors and aetiology.

Adolescent ; Adult ; Aged ; Animals ; Child ; China ; epidemiology ; Disease Reservoirs ; Female ; Humans ; Male ; Mice ; Middle Aged ; Rats ; Rickettsia rickettsii ; classification ; genetics ; isolation & purification ; Rocky Mountain Spotted Fever ; epidemiology ; microbiology ; Rodentia ; microbiology ; Sequence Homology, Amino Acid ; Ticks ; microbiology