Greub, Gilbert

Summary Accumulating evidence supports a role for Chlamydia ‐related organisms as emerging pathogens for human and animals. Assessment of their pathogenicity requires strain availability, at least for animal models and serological studies. As these obligate intracellular species are able to grow inside amoebae, we used co‐culture with Acanthamoeba castellanii in an attempt to recover new Chlamydia ‐related species from river water. We isolated two strains from eight water samples. The first strain is a new Parachlamydia acanthamoebae strain that differs from previously described isolates by only two bases in the complete 16S rRNA gene sequence. The second isolate is the first representative of a new Chlamydiales family, as demonstrated by genetic and phylogenetic analyses of the 16S rRNA, 23S rRNA, ADP/ATP translocase and RnpB encoding genes. Using fluorescent in situ hybridization and electron microscopy, we demonstrated that it grows in high numbers in amoebae, where it exhibits a Chlamydia ‐like developmental cycle with reticulate bodies and star‐like elementary bodies. Based on these results, we propose to name this new species ‘ Criblamydia sequanensis ’. This work confirmed that amoebal co‐culture is a relevant method to isolate new chlamydiae, and that it can be successfully applied to ecosystems colonized with a complex microbial community.

ABSTRACT We report on a new Actinobaculum species, “ Actinobaculum massiliae ,” isolated from the urine of an elderly woman with recurrent cystitis. Its phenotypic pattern was similar to those of both of the other Actinobaculum species described to date. On 16S rRNA sequencing, the Marseille isolate shared 95% homology with Actinobaculum suis , 92 to 93% homology with Actinobaculum schaalii , 91 to 92% homology with Arcanobacterium spp., and 87 to 90% homology with Actinomyces species. A bootstrap value of 99% supports the node separating the Actinobaculum sp. from its closest neighbor ( A. suis ). In conclusion, on the basis of phenotypic, genotypic, and phylogenetic assessments, we show that the Marseille isolate is a previously unrecognized organism within the Actinobaculum genus, and we propose placement of the organism in the taxon “ Actinobaculum massiliae .”