Protein characterization of Australian spotted fever group rickettsiae and monoclonal antibody typing of Rickettsia honei

Spotted Fever Rickettsiosis in a Wildlife Researcher in Sabah, Malaysia: A Case Study

We present evidence for a case of spotted fever rickettsiosis with severe complications in a young adult male. Although spotted fever group rickettsiae (SFGR) have been reported as the most prevalent cause of rickettsiosis in rural areas of Sabah, Malaysia since the 1980s, this is the first detailed case report of suspected SFGR in the state. Current data on the prevalence, type, and thorough clinical reports on complications of SFGR and other rickettsioses in Sabah is lacking and required to raise the awareness of such diseases. There is a need to emphasize the screening of rickettsioses to medical personnel and to encourage the use of appropriate antibiotics as early treatment for nonspecific febrile illnesses in this region. Suspected rickettsioses need to be considered as one of the differential diagnoses for patients presenting with acute febrile illness for laboratory investigations, and early treatment instituted.

Comparison of different media for preservation and transport of viable rickettsiae

Rickettsiae tend to have a rapid decrease of viability outside living cells. Therefore, the transport of samples containing viable rickettsiae for culturing in cell culture for diagnostic purposes is challenging. The viability of rickettsiae in different transport media (commercially available transport medium COPAN "UTM-RT transport medium for viruses, chlamydia, mycoplasma, and ureaplasma," minimal essential medium (MEM) with and without 10% foetal calf serum) at various time points at 4 °C and at ambient temperature (22 °C) was compared. Rickettsia honei was used as model organism. After 2 weeks of storage at room temperature, no viable rickettsiae were detectable any more while storage at 4 °C kept rickettsiae viable for up to 4 weeks. The commercially available COPAN medium showed similarly good or slightly better stabilizing effects on rickettsiae compared with MEM + 10% foetal calf serum, pure MEM demonstrated the poorest results. It is important to transport and store media with potentially rickettsiae-containing samples at 4 °C to prevent inactivation. MEM + 10% foetal calf serum can be used if no commercial medium is available with similarly good results.

Phylogenetic Analysis of Spotted Fever Group Rickettsiae Based on gltA, 17-kDa, and rOmpA Genes Amplified by Nested PCR from Ticks in Japan

In order to understand the natural situation of rickettsiae in the ticks in Japan, the rickettsial genes, gltA gene, rOmpA gene, and 17-kDa gene, were amplified from the ticks by nested PCR. The prevalences of rickettsial gltA genes among Haemaphysalis formosensis, H. longicornis, H. megaspinosa, Ixodes ovatus, H. flava, H. kitaokai, and I. persulcatus were 62, 57, 24, 24, 19, 13, and 10%, respectively; 26% (186/722) being the average. The gltA genes amplified from the ticks were classified into 9 genotypes (I to IX) by the difference in nucleotide sequences. Genotype I was detected from 7 species of ticks. Genotype II mainly was detected from H. longicornis and H. formosensis. Genotypes III and VII mainly were detected from H. flava and I. ovatus. The polarization in the distribution of genotypes among regions where the ticks were collected was not clear. Based on the phylogenetic analysis of the three genes presented here, genotypes I, III, and IV (detected from H. formosensis, H. hystricia, and I. ovatus ) are genetically close with each other, but rickettsiae of the same property still have not been isolated from ticks anywhere in the world. These genotypes should be considered as new species among SFG rickettsiae. Genotype II was identical with strain FUJ-98, genetically close to R. japonica which has been isolated from ticks in China. Genotype V was identical with R. felis and strain California 2 isolated from the cat flea. This is the first report on the detection of R. felis from ticks. Genotype VI detected from Ixodes sp. did not seem to belong to genus Rickettsia. Based on the previous antigenic data and the phylogenetic analysis presented here, Genotype VII should be considered a variant of R. helvetica and genotype VIII detected from I. ovatus and I. persulcatus were identical with R. helvetica. Genotype IX detected from I. nipponensis was genetically close to the strains IRS3, IRS4, and IrR/Munich isolated from I. ricinus in Slovakia and German.

Phylogenetic analysis of spotted fever group Rickettsiae isolated from ticks in Japan

Eight spotted fever group (SFG) rickettsiae isolated from ticks in Japan were classified by phylogenetic analysis based on the nucleotide sequences of both the citrate synthase-encoding gene (gltA) and 190-kDa antigen-encoding gene (rOmpA). In the phylogenetic tree of gltA, strains DT-1 and FLA-1 isolated from the Dermacentor taiwanensis and Haemaphysalis frava ticks, respectively, were placed as Rickettsia japonica, and strains IO-1, IO-2, IO-25, IM-1 and IP-2 from genus Ixodes ticks were placed as Rickettsia helvetica. Strain AT-1 isolated from the Amblyomma testudinarium belonged to the cluster including Rickettsia akari, Rickettsia australis and Rickettsia felis. In the phylogenetic tree of the rOmpA, strains DT-1 and FLA-1 were placed as R. japonica, and strain AT-1 belonged to the cluster including Rickettsia cooleyi and the symbiont of Ixodes scapularis. The rOmpA fragments of 5 Ixodes isolates could not be amplified by PCR. The present study showed that strains DT-1 and FLA-1 were genotypically identical to R. japonica, and 5 Ixodes isolates were associated with the R. helvetica. Based on previous genotypic and antigenic data, and the phylogenetic analysis presented here, strain AT-1 should be considered as a new species among SFG rickettsiae.

Phenotypic and genotypic homogeneity of the strains of Rickettsia japonica isolated from patients with Oriental spotted fever

Nine pathogenic strains of Rickettsia japonica isolated from patients with Oriental spotted fever were compared phenotypically and genotypically. Constitution and antigenicity of the proteins demonstrated to be the same among strains. Polymerase chain reaction (PCR) amplification of the two major outer membrane protein genes (ompA and ompB) and an intracellular spotted fever group-common antigen protein gene (rps120) produced the same sizes of products for all strains. Restriction fragment length polymorphism of the PCR products showed the same pattern among strains with each endonuclease. Thus, these strains belong to a single type, the same as the type strain YH (=ATCC VR-1363).

Taxonomic relationships among spotted fever group rickettsiae as revealed by antigenic analysis with monoclonal antibodies

The spotted fever group (SFG) is made up of more than 20 different rickettsial species and strains. Study of the taxonomic relationships among the group has been attempted by phenotypic, genotypic, and phylogenetic analyses. In this study, we determined taxonomic relationships among the SFG rickettsiae by comparative analysis of immunogenic epitopes reactive against a panel of monoclonal antibodies. A total of 98 monoclonal antibodies, which were directed against epitopes on the major immunodominant proteins or on the lipopolysaccharide-like antigens of strains of Rickettsia africae, Rickettsia conorii, Rickettsia massiliae, Rickettsia akari, Rickettsia sibirica, and Rickettsia slovaca, were used in the study. The distribution and expression of the epitopes among 29 SFG rickettsiae and Rickettsia bellii were assessed by determination of reaction titers in a microimmunofluorescence assay. The results were scored as numerical taxonomic data, and cluster analysis was used to construct a dendrogram. The architecture of this dendrogram was consistent with previous taxonomic studies, and the implications of this and other findings are discussed.