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. (1/25)

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)

Identification of nine species of the Chlamydiaceae using PCR-RFLP. (2/25)

The family Chlamydiaceae contains two genera and nine species. Rapid and easy identification of these species is essential for taxonomic, epidemiological and clinical determinations. Currently, DNA sequence analysis is the only accepted method that decisively distinguishes all nine species. In this study, a simple and rapid PCR-RFLP procedure was developed by which laboratory-cultured chlamydial specimens could be identified. To accomplish this, conserved oligonucleotide primers and restriction sites were deduced from 16S and 23S rRNA sequence data from > 50 chlamydial strains representing all nine species. DNA from 25 previously characterized chlamydial strains were tested with these primers and restriction enzymes. All nine chlamydial species were reliably distinguished in the tests. The procedure was optimized by adjusting the annealing temperature using both a standard and a heat-activated DNA polymerase to reduce mismatch PCR amplification of mycoplasmas and other bacteria. The result was that a PCR method for species identification of chlamydial isolates and for distinguishing mycoplasmas and chlamydiae was created. This method can be used to rapidly identify known species of the family Chlamydiaceae.  (+info)

Simkania negevensis strain ZT: growth, antigenic and genome characteristics. (3/25)

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)

Chlamydophila abortus in a Brown skua (Catharacta antarctica lonnbergi) from a subantarctic island. (4/25)

On Bird Island, South Georgia, a new strain of Chlamydophila abortus was detected in one Brown skua out of 37 specimens from six different seabird species. Phylogenetic analysis of the rnpB and omp1 genes indicated the strain to be more closely related to C. abortus than to 6BC, the type strain of Chlamydophila psittaci.  (+info)

Molecular evolution of the Chlamydiaceae. (5/25)

Phylogenetic analyses of surface antigens and other chlamydial proteins were used to reconstruct the evolution of the Chlamydiaceae. Trees for all five coding genes [the major outer-membrane protein (MOMP), GroEL chaperonin, KDO-transferase, small cysteine-rich lipoprotein and 60 kDa cysteine-rich protein] supported the current organization of the family Chlamydiaceae, which is based on ribosomal, biochemical, serological, ecological and DNA-DNA hybridization data. Genetic distances between some species were quite large, so phylogenies were evaluated for robustness by comparing analyses of both nucleotide and protein sequences using a variety of algorithms (neighbour-joining, maximum-likelihood, maximum-parsimony with bootstrapping, and quartet puzzling). Saturation plots identified areas of the trees in which factors other than relatedness may have determined branch attachments. All nine species were clearly differentiated by distinctness ratios calculated for each gene. The distribution of virulence traits such as host and tissue tropism were mapped onto the consensus phylogeny. Closely related species were no more likely to share virulence characters than were more distantly related species. This phylogenetically disjunct distribution of virulence traits could not be explained by lateral transfer of the genes we studied, since we found no evidence for lateral gene transfer above the species level. One interpretation of this observation is that when chlamydiae gain access to a new niche, such as a new host or tissue, significant adaptation ensues and the virulence phenotype of the new species reflects adaptation to its environment more strongly than it reflects its ancestry.  (+info)

Chlamydia species as a cause of community-acquired pneumonia in Canada. (6/25)

Chlamydia pneumoniae has been implicated as a cause of community-acquired pneumonia (CAP) in several studies. However, there has been no comprehensive study of the role of Chlamydia species (C. pneumoniae, C. psittaci (avian and feline strains) and C. pecorum) as a cause of CAP. The aim of the present study was to determine the role of C. pneumoniae, C. psittaci and C. pecorum as causes of CAP. A prospective cohort observational study of CAP was conducted at 15 teaching centres in eight Canadian provinces between January 1996-October 1997. Acute (n=539) and convalescent (n=272) serum samples were obtained for determination of antibody titres to C. pneumoniae, C. psittaci, C. pecorum, C. trachomatis, Mycoplasma pneumoniae, Legionella pneumophila serogroups I-VI, Streptococcus pneumoniae and various respiratory viruses. Twelve of 539 (2.2%) patients had acute C. pneumoniae pneumonia and an additional 32 (5.9%) had possible acute infection. C. pneumoniae was the sole pathogen in 16 of 42 (38.1%) of these patients. The most common copathogens were S. pneumoniae, respiratory syncytial virus and influenza virus type A. C. pneumoniae pneumonia patients were older and more likely to show congestive heart failure compared to bacteraemic S. pneumoniae patients. The latter had a lower mean diastolic blood pressure, a higher white blood cell count and a lower arterial carbon dioxide tension. Two patients had antibody titres suggestive of recent infection with the feline strain of C. psittaci. Although numerically Chlamydia pneumoniae is an important cause of community-acquired pneumonia, no distinctive clinical features associated with this pathogen were detected in the present study. Feline Chlamydia psittaci may cause a few cases of community-acquired pneumonia. Avian Chlamydia psittaci should be considered only if there is a compatible epidemiological history.  (+info)

DNA vaccination against Chlamydiaceae: current status and perspectives. (7/25)

DNA vaccination (also called genetic vaccination) recently celebrated its ten years of existence. This new method of immunization presents several advantages, including the induction of both humoral and cellular immune responses. This vaccination strategy has been very successful and has served as a basis for numerous experiments that had the aim of resolving parasitic, viral, and bacterial infections. In particular, DNA vaccination has been evaluated against Chlamydiaceae, small obligate intracellular bacteria, that induce many pathologies in humans and animals. Despite promising protective effects obtained in murine and turkey models with genes encoding outer membrane proteins and heat shock proteins, DNA vaccination against Chlamydiaceae must be optimized by further investigations and could benefit from the genomic sequencing in terms of the identification of new antigens.  (+info)

Exposure to Chlamydia pneumoniae infection and progression of age-related macular degeneration. (8/25)

Recent studies have found an association between exposure to Chlamydia pneumoniae infection and risk of age-related macular degeneration (AMD). To assess a potential risk of AMD progression posed by exposure to C. pneumoniae, the authors reexamined Australian residents in 2001-2002 who were aged 51-89 years with early AMD at baseline (1992-1995). Examination included macular photography and an enzyme-linked immunosorbent assay to determine antibody titers to the elementary bodies from C. pneumoniae AR39. AMD progression was assessed quantitatively, using both coarse and fine progression steps following an international classification for AMD grading, and also qualitatively, by side-by-side comparison of baseline and follow-up macular photographs. Serologic data were available for 246 of 254 (97%) subjects. AMD progression was associated with a higher antibody titer. After adjustment for age, smoking, family history of AMD, history of cardiovascular diseases, and source study, the subjects in the upper tertiles of antibody titers were 2.1 (95% confidence interval: 0.92, 4.69), 2.6 (95% confidence interval: 1.24, 5.41), and 3.0 (95% confidence interval: 1.46, 6.37) times more at risk of progression than those in the lowest tertile, using three definitions of progression, respectively. The fact that seroreactivity to C. pneumoniae was independently associated with the risk of AMD progression suggests that C. pneumoniae infection may be an additional risk factor for AMD progression.  (+info)

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