Chronic asymptomatic carriage of T. whipplei occurs in humans. Bacterial loads are lower in asymptomatic carriers, and the prevalence of carriage increases with exposure to sewage.

BackgroundObligate intracellular bacteria of arthropods often exhibit a significant role in either human health or arthropod ecology.Methodology/Principal FindingsAn obligate intracellular gamma-proteobacterium was isolated from the actively questing hard tick Ixodes ricinus using mammalian and amphibian cell lines. Transmission electron microscopy revealed a unique morphology of the bacterium, including intravacuolar localization of bacteria grouped predominantly in pairs and internal structures composed of electron-dense crystal-like structures and regular multilayer sheath-like structures. The isolate 20B was characterized to determine its taxonomic position using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that this strain belongs to the family Coxiellaceae, order Legionellales of Gamma-proteobacteria, and the closest relatives are different Rickettsiella spp. The level of 16S rRNA gene sequence similarity between strain 20B and other recognized species of the family was below 94.5%. Partial sequences of the rpoB, parC and ftsY genes confirmed the phylogenetic position of the new isolate. The G+C content estimated on the basis of whole genome analysis of strain 20B was 37.88%. On the basis of its phenotypic and genotypic properties, together with phylogenetic distinctiveness, we propose that strain 20B to be classified in the new genus Diplorickettsia as the type strain of a novel species named Diplorickettsia massiliensis sp. nov.Conclusions/SignificanceConsidering the source of its isolation (hard tick, often biting humans) the role of this bacterium in the pathology of humans, animals and ticks should be further investigated.

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The culture of Tropheryma whipplei, the bacterium responsible for Whipple's disease, has been established only recently. Our objective is to describe, based on our experience, the culture of T. whipplei in HEL cells detected by immunofluorescence staining. Over 3 years, we received 18 samples for T. whipplei culture from 15 patients with Whipple's disease. Ten duodenal biopsy specimens from 10 patients with digestive symptoms were available. Five cardiac valves and three blood samples from five patients with endocarditis were also available. We correlated the results of culture with the type of sample and the culture procedure. Seven isolates were obtained, and three were subsequently established for more than 4 passages. The mean delay for the primary detection was 30 days. The bacterium was isolated more frequently from sterile specimens (5 of 8) than from duodenal biopsy specimens (2 of 10), but the difference (P ‫؍‬ 0.14) was not significant. Decontamination of digestive samples containing colistin, amphotericin B, and cephalotin or ciprofloxacin did not impair the isolation of T. whipplei. The use of vancomycin precludes the primary isolation (7 of 12 versus 0 of 6; P ‫؍‬ 0.08) and the establishment of T. whipplei (3 of 12 versus 0 of 6; P ‫؍‬ 0.5). Omitting samples cultured with vancomycin, the establishment of the strain was significantly higher when antibiotics were prescribed for no more than 7 days (3 of 4 versus 0 of 8; P ‫؍‬ 0.03). Our results demonstrate that samples must be collected within 1 week of an antibiotic regimen's initiation for the successful establishment of the bacterium.