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      First Detection of Spotted Fever Group Rickettsiae in Ixodes ricinus from Italy

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          Ixodes ricinus from Italy were examined for the first time to detect whether rickettsiae were present. Using molecular methods, we detected three different spotted fever group rickettsiae, including Rickettsia helvetica. Our results raise the possibility that bacteria other than R. conorii are involved in rickettsial diseases in Italy.

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          Most cited references 19

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          Laboratory diagnosis of rickettsioses: current approaches to diagnosis of old and new rickettsial diseases.

           B. La Scola,  D Raoult (1997)
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            Citrate synthase gene comparison, a new tool for phylogenetic analysis, and its application for the rickettsiae.

            Using PCR and an automated laser fluorescent DNA sequencer, we amplified and sequenced a 1,234-bp fragment of the citrate synthase-encoding gene (gltA) of 28 bacteria belonging to the genus Rickettsia. Comparative sequence analysis showed that most of the spotted fever group (SFG) rickettsiae belonged to one of two subgroups. The first subgroup included Rickettsia massiliae, strain Bar 29, Rickettsia rhipicephali, "Rickettsia aeschlimanni," and Rickettsia montana, which have been isolated only from ticks. The second subgroup was larger and included the majority of the human pathogens and also rickettsiae isolated only from ticks; the members of this subgroup were strain S, Rickettsia africae, "Rickettsia monglotimonae," Rickettsia sibirica, Rickettsia parkeri, Rickettsia conorii, Rickettsia rickettsii, the Thai tick typhus rickettsia, the Israeli tick typhus rickettsia, the Astrakhan fever rickettsia, "Rickettsia slovaca," and Rickettsia japonica. The sequence analysis also showed that the tick-borne organisms Rickettsia helvetica and Rickettsia australis and the mite-borne organism Rickettsia akari were associated with the SFG cluster, that Rickettsia prowazekii and Rickettsia typhi, two representatives of the typhus group, clustered together, and that Rickettsia canada; Rickettsia bellii, and the AB bacterium probably represent three new groups. We compared the phylogenetic trees inferred from citrate synthase gene sequences and from 16S ribosomal DNA (rDNA) sequences. For rickettsial phylogeny, the citrate synthase approach was more suitable, as demonstrated by significant bootstrap values for all of the nodes except those in the larger subgroup defined above. We also compared phylogenetic analysis results obtained in a comparison of the sequences of both genes for all of the representatives of the domain Bacteria for which the gltA sequence was determined. We believe that comparison of gltA sequences could be a complementary approach to 16S rDNA sequencing for inferring bacterial evolution, especially when unstable phylogenetic models are obtained from ribosomal sequences because of high levels of sequence similarity between the bacteria studied.
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              Endosymbionts of ticks and their relationship to Wolbachia spp. and tick-borne pathogens of humans and animals.

              The presence, internal distribution, and phylogenetic position of endosymbiotic bacteria from four species of specific-pathogen-free ticks were studied. These included the hard ticks Ixodes scapularis (the black-legged tick), Rhipicephalus sanguineus (the brown dog tick), and Haemaphysalis longicornis and the African soft tick Ornithodoros moubata. PCR assays for bacteria, using two sets of general primers for eubacterial 16S and 23S rRNA genes (rDNAs) and seven sets of specific primers for wolbachial, rickettsial, or Francisella genes, indicated that I. scapularis possessed symbiotic rickettsiae in the ovaries and that the other species harbored eubacteria in both the ovaries and Malpighian tubules. Phylogenetic analysis based on the sequence of 16S rDNA indicated that the symbiont of I. scapularis belonged to the alpha subgroup of proteobacteria and was closely related to the members of the genus Rickettsia. The other species had similar microorganisms in the ovaries and Malpighian tubules, which belonged to the gamma subgroup of proteobacteria, and formed a monophyletic group with the Q-fever pathogen, Coxiella burnetii. O. moubata harbored another symbiont, which formed a monophyletic group with Francisella tularensis and Wolbachia persica, the latter a symbiont previously isolated from Malpighian tubules of the soft tick Argas (Persicargas) arboreus. Thus, the symbionts of these four tick species were not related to the Wolbachia species found in insects. The two symbionts that live in the Malpighian tubules, one closely related to C. burnetii and the other closely related to F. tularensis, appear to be of ancient origin and be widely distributed in ticks.

                Author and article information

                Emerg Infect Dis
                Emerging Infect. Dis
                Emerging Infectious Diseases
                Centers for Disease Control and Prevention
                September 2002
                : 8
                : 9
                : 983-986
                [* ]Università degli Studi di Milano, Italy
                []National Institute of Agrobiological Sciences, Tsukuba, Japan
                []Università di Camerino, Macerata, Italy
                [§ ]Centro di Ecologia Alpina, Trento, Italy
                Author notes
                Address for correspondence: Nathan Lo, Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Università di Milano, Via Celoria 10, 20133 Milano, Italy; fax: 39 02 5031 8095; e-mail: nathanlo@

                Infectious disease & Microbiology

                tick-borne diseases, glta, ixodes ricinus, rickettsia, ompa, italy, 17 kda


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