Molecular evidence for the existence of additional members of the order Chlamydiales. (1/76)

Respiratory tract infections in man may be caused by several members of the genus Chlamydia and also by two Chlamydia-like strains, 'Simkania negevensis' (Z-agent) and 'Parachlamydia acanthamoebae' (Bng). To facilitate diagnostic procedures a PCR assay able to detect all known Chlamydiaceae sequences in one reaction was developed. For this purpose, primers were selected to amplify a fragment of the 16S rRNA gene. Characterization of the amplified fragments was done by hybridization with specific probes and by sequencing. PCR assays were carried out using DNA isolated from nose/throat specimens or from peripheral blood mononuclear cells of patients with respiratory tract infections, and from vessel wall specimens of abdominal aneurysms. Six of the 42 nose/throat swab specimens analysed yielded strong bands and one yielded a faint band. Three of these bands were identified as Chlamydia pneumoniae and one as Chlamydia trachomatis by sequencing. Analysis of the three other bands yielded two different new sequences. DNA isolated from peripheral blood mononuclear cells of one patient yielded a third new sequence. DNA isolated from peripheral blood mononuclear cells of four healthy controls was negative. One of the abdominal aneurysm specimens also yielded a strong band. Sequencing revealed a fourth new sequence. All negative controls included during specimen processing and PCR analysis remained negative. The typical secondary structure of microbial 16S genes was present in all four new sequences indicating the validity of the sequence data. All four new sequences were distinct from other bacteria and clustered together with known Chlamydiaceae sequences. Phylogenetic analysis suggested a new lineage, separating the four new sequences, 'S. negevensis' and 'P. acanthamoebae' from the genus Chlamydia with the four known chlamydial species. In conclusion, this study provides evidence for the existence of several new members of the order Chlamydiales. Since the source of the Chlamydia-like strains has not been identified and serological and/or molecular cross-reactivities may be expected, results of identification of infecting recognized organisms should be interpreted cautiously.  (+info)

Seroprevalence of IgG antibodies to the chlamydia-like microorganism 'Simkania Z' by ELISA. (2/76)

The newly described microorganism 'Simkania Z', related to the Chlamydiae, has been shown to be associated with bronchiolitis in infants and community acquired pneumonia in adults. The prevalence of infection in the general population is unknown. A simple ELISA assay for the detection of serum IgG antibodies to 'Simkania Z' was used to determine the prevalence of such antibodies in several population samples in southern Israel (the Negev). The groups tested included 94 medical and nursing students, 100 unselected blood donors, 106 adult members of a Negev kibbutz (communal agricultural settlement), and 45 adult Bedouin, residents of the Negev. IgG antibodies to 'Simkania Z' were found in 55-80% of these presumably healthy individuals, independently of antibodies to Chlamydia trachomatis and Chlamydia pneumoniae. The Bedouin had a seropositivity rate of 80%, while all other groups had rates of between 55 and 64%. These results indicate that 'Simkania Z' infection is probably common in southern Israel.  (+info)

Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms. (3/76)

The current taxonomic classification of Chlamydia is based on limited phenotypic, morphologic and genetic criteria. This classification does not take into account recent analysis of the ribosomal operon or recently identified obligately intracellular organisms that have a chlamydia-like developmental cycle of replication. Neither does it provide a systematic rationale for identifying new strains. In this study, phylogenetic analyses of the 16S and 23S rRNA genes are presented with corroborating genetic and phenotypic information to show that the order Chlamydiales contains at least four distinct groups at the family level and that within the Chlamydiaceae are two distinct lineages which branch into nine separate clusters. In this report a reclassification of the order Chlamydiales and its current taxa is proposed. This proposal retains currently known strains with > 90% 16S rRNA identity in the family Chlamydiaceae and separates other chlamydia-like organisms that have 80-90% 16S rRNA relatedness to the Chlamydiaceae into new families. Chlamydiae that were previously described as 'Candidatus Parachlamydia acanthamoebae' Amann, Springer, Schonhuber, Ludwig, Schmid, Muller and Michel 1997, become members of Parachlamydiaceae fam. nov., Parachlamydia acanthamoebae gen. nov., sp. now. 'Simkania' strain Z becomes the founding member of Simkaniaceae fam. nov., Simkania negevensis gen. nov., sp. nov. The fourth group, which includes strain WSU 86-1044, was left unnamed. The Chlamydiaceae, which currently has only the genus Chlamydia, is divided into two genera, Chlamydia and Chlamydophila gen. nov. Two new species, Chlamydia muridarum sp. nov. and Chlamydia suis sp. nov., join Chlamydia trachomatis in the emended genus Chlamydia. Chlamydophila gen. nov. assimilates the current species, Chlamydia pecorum, Chlamydia pneumoniae and Chlamydia psittaci, to form Chlamydophila pecorum comb. nov., Chlamydophila pneumoniae comb. nov. and Chlamydophila psittaci comb. nov. Three new Chlamydophila species are derived from Chlamydia psittaci: Chlamydophila abortus gen. nov., sp. nov., Chlamydophila caviae gen. nov., sp. nov. and Chlamydophila felis gen. nov., sp. nov. Emended descriptions for the order Chlamydiales and for the family Chlamydiaceae are provided. These families, genera and species are readily distinguished by analysis of signature sequences in the 16S and 23S ribosomal genes.  (+info)

Analysis of the 16S rRNA gene of micro-organism WSU 86-1044 from an aborted bovine foetus reveals that it is a member of the order Chlamydiales: proposal of Waddliaceae fam. nov., Waddlia chondrophila gen. nov., sp. nov. (4/76)

The structural gene encoding the 16S rRNA of the new obligate intracellular organism presently designated WSU 86-1044T was sequenced and analysed to establish its phylogenetic relationships. The 16S rDNA sequence was most closely related to those of chlamydial species, having 84.7-85.3% sequence similarity, while it had 72.4-73.2% similarity with rickettsia-like organisms. When the sequences of the four species of chlamydiae (Chlamydophila psittaci, Chlamydia trachomatis, Chlamydophila pneumoniae and Chlamydophila pecorum) were compared, they had > 93% sequence similarity indicating that WSU 86-1044T was not close enough to be in the same family as current Chlamydiaceae members. However, based on the 84.7-85.3% 16S rDNA sequence similarity of WSU 86-1044T and other previously described characteristics, WSU 86-1044T belongs to a novel family within the order Chlamydiales; hence, the proposal of Waddliaceae fam. nov., Waddlia chondrophila gen. nov., sp. nov.  (+info)

Simkania negevensis strain ZT: growth, antigenic and genome characteristics. (5/76)

Simkania negevensis is the type species of Simkaniaceae, a recently proposed family in the order Chlamydiales. In the current study, growth, antigenic and genomic characteristics of this intracellular bacterium were investigated and compared to those of members of the family Chlamydiaceae. Growth of the organism, as assessed by infectivity assays, reached a plateau in 2-3 d although by light microscopy the cytopathic effect on the host cells increased for 12 or more days after infection. S. negevensis growth was unaffected by sulfadiazine. Cells infected by S. negevensis strain ZT were not recognized by either of two monoclonal antibodies specific for Chlamydiaceae LPS and several specific Chlamydiaceae ompA primers were unable to PCR amplify a S. negevensis gene. The S. negevensis genome contained one copy of the ribosomal operon. The genome size of S. negevensis strain ZT was determined by PFGE to be 1.7 Mbp, and the G + C content was 42.5 mol%. These data, taken together with other published data, are consistent with the proposal that S. negevensis belongs to a distinct family in the order Chlamydiales.  (+info)

An unspliced group I intron in 23S rRNA links Chlamydiales, chloroplasts, and mitochondria. (6/76)

Chlamydia was the only genus in the order Chlamydiales until the recent characterization of Simkania negevensis Z(T) and Parachlamydia acanthamoebae strains. The present study of Chlamydiales 23S ribosomal DNA (rDNA) focuses on a naturally occurring group I intron in the I-CpaI target site of 23S rDNA from S. negevensis. The intron, SnLSU. 1, belonged to the IB4 structural subgroup and was most closely related to large ribosomal subunit introns that express single-motif, LAGLIDADG endonucleases in chloroplasts of algae and in mitochondria of amoebae. RT-PCR and electrophoresis of in vivo rRNA indicated that the intron was not spliced out of the 23S rRNA. The unspliced 658-nt intron is the first group I intron to be found in bacterial rDNA or rRNA, and it may delay the S. negevensis developmental replication cycle by affecting ribosomal function.  (+info)

Characterization of the rnpB gene and RNase P RNA in the order Chlamydiales. (7/76)

The sequence of the RNase P RNA gene (rnpB) was determined for 60 strains representing all nine species in the family Chlamydiaceae and for the related Chlamydiales species, Parachlamydia acanthamoebae and Simkania negevensis. These sequences were used to infer evolutionary relationships among the Chlamydiaceae. The analysis separated Chlamydophila and Chlamydia into two lineages, with Chlamydophila forming three distinct clusters: the Chlamydophila pneumoniae strains; the Chlamydophila pecorum strains; and a third cluster comprising the species Chlamydophila psittaci, Chlamydophila abortus, Chlamydophila caviae and Chlamydophila felis. The Chlamydia line of descent contained two clusters, with the Chlamydia suis strains distinctly separated from strains of Chlamydia trachomatis and Chlamydia muridarum. This analysis indicated that the rnpB sequence and structure are distinctive markers for species in the Chlamydiaceae. It was also demonstrated that the RNase P RNA derived from Chlamydia trachomatis is able to cleave a tRNA precursor in the absence of protein. These findings are discussed in relation to the structure of Chlamydia RNase P RNA.  (+info)

Phylogenetic diversity among geographically dispersed Chlamydiales endosymbionts recovered from clinical and environmental isolates of Acanthamoeba spp. (8/76)

The recently proposed reorganization of the order Chlamydiales and description of new taxa are broadening our perception of this once narrowly defined taxon. We have recovered four strains of gram-negative cocci endosymbiotic in Acanthamoeba spp., representing 5% of the Acanthamoeba sp. isolates examined, which displayed developmental life cycles typical of members of the Chlamydiales. One of these endosymbiont strains was found stably infecting an amoebic isolate recovered from a case of amoebic keratitis in North America, with three others found in acanthamoebae recovered from environmental sources in North America (two isolates) and Europe (one isolate). Analyses of nearly full-length 16S rRNA gene sequences of these isolates by neighbor joining, parsimony, and distance matrix methods revealed their clustering with other members of the Chlamydiales but in a lineage separate from those of the genera Chlamydia, Chlamydophila, Simkania, and Waddlia (sequence similarities, <88%) and including the recently described species Parachlamydia acanthamoebae (sequence similarities, 91.2 to 93.1%). With sequence similarities to each other of 91.4 to 99.4%, these four isolates of intra-amoebal endosymbionts may represent three distinct species and, perhaps, new genera within the recently proposed family Parachlamydiaceae. Fluorescently labeled oligonucleotide probes targeted to 16S rRNA signature regions were able to readily differentiate two groups of intra-amoebal endosymbionts which corresponded to two phylogenetic lineages. These results reveal significant phylogenetic diversity occurring among the Chlamydiales in nontraditional host species and supports the existence of a large environmental reservoir of related species. Considering that all described species of Chlamydiales are known to be pathogenic, further investigation of intra-amoebal parachlamydiae as disease-producing agents is warranted.  (+info)

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