Acute spotted fever rickettsiosis among febrile patients, Cameroon.
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Although potential arthropod vectors are abundant in Cameroon, acute febrile illnesses are rarely evaluated for arboviral or rickettsial infections. Serum samples from 234 acutely febrile patients at clinics in Tiko and Buea, Cameroon, were examined for antibodies to Rickettsia africae and African alphaviruses and flaviviruses. These serum samples did not contain antibodies against typhoid, and blood malarial parasites were not detected. Serum samples of 32% contained immunoglobulin M antibodies reactive with R. africae by immunofluorescence assay and were reactive with outer membrane proteins A and B of R. africae by immunoblotting. These findings established a diagnosis of acute rickettsiosis, most likely African tick-bite fever. Hemagglutination inhibition testing of the serum samples also detected antibodies to Chikungunya virus (47%) and flaviviruses (47%). High prevalence of antibodies to arboviruses may represent a major, previously unrecognized public health problem in an area where endemic malaria and typhoid fever have been the principal diagnostic considerations. (+info)
Spotted fever group rickettsiae from ticks captured in Sudan.
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Ticks were collected from ruminants in various areas of Sudan in 1998 and 2000. Primer pairs of rickettsial citrate synthase gene (gltA) and a spotted fever group (SFG) rickettsial 190-kDa surface antigen gene (rompA), respectively, were used for identification. Polymerase chain reaction (PCR)-positive products were used for DNA sequencing. The gltA gene was detected in 55% of the ticks examined (57/104). Among the 57 ticks studied, 19 were positive for the rompA gene. Thus, 18% of the ticks examined were found to be infected with SFG rickettsiae. The nucleotide sequences of the amplified rompA gene fragment of Hyalomma spp. and Amblyomma spp. were similar to those of Rickettsia aeschlimannii and Rickettsia africae, respectively. In this study, we succeeded in detecting the SFG rickettsiae gene in ticks, and established that there were at least two species of SFG rickettsiae in field ticks in Sudan. (+info)
Comparison of Western immunoblotting and microimmunofluorescence for diagnosis of Mediterranean spotted fever.
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One-hundred serum samples from 41 patients suffering from Mediterranean spotted fever (MSF) were tested by microimmunofluorescence (MIF) and Western blot (WB; immunoblot). Immunoglobulin G (IgG), IgM, and IgA antibody-specific responses to the high-molecular-mass species-specific protein antigens (115 kDa and 135 kDa) of Rickettsia conorii, as well as to cross-reactive lipopolysaccharide (LPS) antigens, were observed. The WB assay detected IgM-type antibodies earlier than did the MIF assay. These antibodies were often directed against nonspecific LPS and may have a questionable positive predictive value. In addition, an IgG reaction to a 60-kDa protein was observed in four cases of malignant forms of MSF but was never observed in cases of mild forms. This reaction could be correlated with a marker of the severity of the development of MSF. From a previous MIF survey of blood donors, 9 negative, 11 IgG-positive, and 6 IgM-positive serum samples were selected for comparison by WB. Sera negative by MIF were also negative by WB. MIF IgG-positive sera showed a specific response to R. conorii in the WB assay, but the six serum samples from this seroepidemiological study positive for IgM by MIF were almost all negative by the WB assay. One was positive for IgM against the LPS but was considered a false positive. The WB is shown to provide a new tool for serodiagnosis. (+info)
Effect of blocking the CXCL9/10-CXCR3 chemokine system in the outcome of endothelial-target rickettsial infections.
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Rickettsiae cause systemic infections such as Rocky Mountain spotted fever and boutonneuse fever. The main cellular target of these obligately intracellular bacteria is the endothelium. T lymphocytes are the most important effectors of immunity, and the CXCR3 ligands CXCL9 and CXCL10 may play an important role in the T cell-mediated clearance of rickettsiae from the infected vasculature as suggested by recent expression studies. Here we showed that antibody-mediated neutralization of CXCL9 and CXCL10, and CXCR3 gene knockout, had no effect on survival or bacterial loads of mice infected with rickettsiae. We also demonstrated that rickettsiae triggered the endothelial expression of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 in vivo. These findings suggested that antigenic presentation by endothelial cells together with an endothelial inflammatory phenotype induced by the rickettsial infection may be sufficient to arrest T cells and trigger their anti-rickettsial effector mechanisms without the need for chemokines. (+info)
Use of highly variable intergenic spacer sequences for multispacer typing of Rickettsia conorii strains.
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By use of the nearly perfectly colinear genomes of Rickettsia conorii and Rickettsia prowazekii, we compared the usefulness of three types of sequences for typing of R. conorii isolates: (i) 5 variable coding genes comprising the 16S ribosomal DNA, gltA, ompB, and sca4 (gene D) genes, which are present in both genomes, and the ompA gene, which is degraded in R. prowazekii; (ii) 28 genes degraded in R. conorii but intact in R. prowazekii, including 23 split and 5 remnant genes; and (iii) 27 conserved and 25 variable intergenic spacers. The 4 conserved and 23 split genes as well as the 27 conserved intergenic spacers each had identical sequences in 34 human and 5 tick isolates of R. conorii. Analysis of the ompA sequences identified three genotypes of R. conorii. The variable intergenic spacers were significantly more variable than conserved genes, split genes, remnant genes, and conserved spacers (P < 10(-2) in all cases). Four of the variable intergenic spacers (dksA-xerC, mppA-purC, rpmE-tRNA(fMet), and tRNA(Gly)-tRNA(Tyr)) had highly variable sequences; when they were combined for typing, multispacer typing (MST) identified 27 different genotypes in the 39 R. conorii isolates. Two batches from the same R. conorii strain, Malish (Seven), with different culture passage histories were found to exhibit the same MST type. MST was more discriminatory for strain genotyping than multiple gene sequencing (P < 10(-2)). Phylogenetic analysis based on MST sequences was concordant with the geographic origins of R. conorii isolates. Our study supports the usefulness of MST for strain genotyping. This tool may be useful for tracing a strain and identifying its source during outbreaks, including those resulting from bioterrorism. (+info)
Isolation of an agent of the spotted fever group rickettsia from tick eggs in Madrid, Spain.
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Ticks recovered from dogs in rural villages around Madrid (Spain) were processed to isolate rickettsiae. One sample containing mixtures of ticks and four containing eggs, in which rickettsiae had been detected by indirect immunofluorescence with a human serum highly reactive to Rickettsia conorii, were decontaminated, homogenized and inoculated onto Vero cells. Two egg samples yielded a cytopathic agent that reacted positively by immunofluorescence. One sample (14H) was successfully subcultured and identified as a member of the spotted fever group rickettsia. Tick eggs provide suitable material for isolation of rickettsia. (+info)
Presence of Rickettsia conorii subsp. israelensis, the causative agent of Israeli spotted fever, in Sicily, Italy, ascertained in a retrospective study.
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A retrospective analysis by molecular-sequence-based techniques was performed to correctly identify the etiological agent of 24 Mediterranean spotted fever cases occurring in Western Sicily, Italy, from 1987 to 2001. Restriction analysis of a 632-bp PCR-amplified portion of the ompA gene allowed presumptive identification of five clinical isolates as belonging to Rickettsia conorii subsp. israelensis, the etiological agent of Israeli spotted fever (ISF). The remaining 19 rickettsial isolates were Rickettsia conorii subsp. conorii, the only pathogenic rickettsia of the spotted fever group reported in Italy until the present. Sequence analysis of the ompA gene confirmed the identification of all the R. conorii subsp. israelensis isolates and demonstrated that rickettsiosis caused by R. conorii subsp. israelensis can be traced back to 1991 in Sicily. The recorded clinical data of the five ISF patients support the idea that these strains could correlate to more-severe forms of human disease. Three of five patients experienced severe disease, and one of them died. (+info)
Laboratory-confirmed Mediterranean spotted fever in a Japanese traveler to Kenya.
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A Japanese traveler returning from Kenya became ill, presenting with fever and a prominent, generalized rash without an eschar. Results of the immunofluorescence antibody assay of the patient's sera performed in Japan were compatible with illness due to a spotted fever group (SFG) rickettsia, and a presumptive diagnosis of African SFG rickettsiosis, probably either Mediterranean spotted fever (MSF) or African tick-bite fever (ATBF), was rendered. To further define the disease diagnosis, sera were examined in France by Western immunoblotting combined with cross-adsorption, which confirmed the diagnosis of MSF but not of ATBF. Because of the need to further characterize the epidemiologic and clinical features of the two African SFG rickettsioses, clinicians are encouraged to contact a specialized laboratory when encountering such cases. (+info)