Formally described by Rurangirwa et al., 1999, the type strain is W. chondrophila WSU 86-1044 which was isolated from pooled lung and liver tissues of an aborted bovine fetus [Dilbeck et al., 1990]. At first, the agent appeared to be a new member of the rickettsiae because it showed cross-reactions with antisera directed against Cowdria ruminantium [a tick-borne Rickettsiales agent of ruminants; the cross-reacting antigen was not identified].

Taxonomic Description of Waddliaceae fam. nov

Waddliaceae currently includes the type genus, Waddlia. The description of this family is identical at present to that of `micro-organism WSU 86-1044′ (Dilbeck et al., 1990; Kocan et al., 1990) which are obligate intracellular organisms resistant to penicillin. They grow well in BT producing multiple cytoplasmic vacuoles and Gram-negative, periodic acidï¿½Schiff negative and non-acid-fast inclusions.

The inclusions contain coccoid organisms ranging from 0ï¿½2 to 0ï¿½5 um in size. The BT infectivity is abolished by tetracycline and/or chloroform treatment. The organism multiplies by binary fission and has two developmental forms: the dense form which is infective, and the reticulated form, usually associated with mitochondria, which undergoes binary fission.

These organisms do not react with antisera used for typing chlamydiae or rickettsiae. The 16S rDNA of the Waddliaceae strains are>90% similar to ribosomal genes in WSU 86-1044T. The family Waddliaceae belongs to the order Chlamydiales and is a sister taxon of the Chlamydiaceae because the ribosomal genes are 80ï¿½90% similar to ribosomal genes in the Chlamydiaceae. Phylogenetic analyses of the Waddliaceae 16S rDNA sequence is presented here. At present this family comprises a single genus, the type genus Waddlia [Rurangirwa et al., 1999].

Taxonomic Description of Waddlia gen. nov.

Waddlia [Wadd’li.a. N.L. fem. n. Waddlia arbitrary name derived from the abbreviation WADDL (Washington Animal Disease Diagnostic Laboratory)]. Members of the genus Waddlia have 16S rDNA that is >90% similar to that of the type species, Waddlia chondrophila strain WSU 86-1044T [Rurangirwa et al., 1999].

Waddlia chondrophila

Taxonomic Description of Waddlia chondrophila sp. nov

Waddlia chondrophila (chon.dro’phi.la. Gr. n. chondros clump; Gr. adj. Philos, a friendly too; M.L. chondrophila liking clumps, in reference to the association of the organism with cellular mitochondria). The species Waddlia chondrophila currently includes only the type strain, WSU 86-1044T ( = ATCC VR 1470T). Waddlia chondrophila was isolated from the tissues of a first-trimester aborted bovine foetus.

The description of this species is identical to that of`microorganism WSU 86-1044T [Dilbeck et al., 1990; Kocan et al., 1990]. The full length of Waddlia chondrophila 16S rDNA sequence is 15 ï¿½ 25 % different from the 16S rDNA of Chlamydiaceae spp., fitting into the 80ï¿½90% identity range that makes this organism a member of the order Chlamydiales, but not a member of the family Chlamydiaceae. The Waddlia chondrophila 16S rDNA sequence is 15.8% different from that of Simkania negevensis strain ZT, while it is 12.8% different from that of Parachlamydia acanthamoebae strain Bn9 T, which excludes it from Simkaniaceae and Parachlamydiaceae families of the order Chlamydiales (Everett et al., 1999. For a newly identified strain to be described as a member of the Waddliaceae, a nearly full-length rDNA of the new strain may only differ from Waddlia chondrophila 16S rDNA by <10% [Rurangirwa et al., 1999].

As indicated by the official description above, organism WSU was originally isolated from the tissues of a first-trimester aborted bovine foetus [Dilbeck et al., 1990]. A cytopathic effect was observed within 2 – 3 days of inoculation of the pooled spleen and liver homogenate into bovine turbinate (BT) cell cultures. The organism was resistant to penicillin or gentamicin but sensitive to tetracycline.

Subsequently, an agent with similar properties and morphology was isolated from the heart of an aborted bovine foetus [Henning et al., 2002]. This latter organism was also resistant to penicillin and failed to react with antisera direct against Chlamydiaceae or Simkania negevensis. 16S and partial 23S ribosomal RNA sequences suggested that the isolate 2032/99 was W. chondrophila or a closely related organism. 16SrRNA sequencing has also suggested the presence of W. chonodrophila in an Australian mammal, the Gilbert’s Potoroo [Bodett et al., 2003].

Animal and human infections with W. chondrophila

W. chondrophila type strain WSU 86–1044 was implicated as an abortigenic agent in 1986 when it was detected in lung, liver, and other tissues of an aborted bovine foetus in the USA [Dilbeck et al., 1990] and was subsequently isolated in Germany from a septic, still born calf [Henning et al., 2002]. However, its overall significance as an agent of bovine abortion is still unclear.

In the USA a serological study indicated a highly significant association between antibody to W. chondrophila and bovine abortion (p<0.00001). However, a PCR-based study of the incidence of chlamydia-related abortions in cattle from the Graubunden region of Switzerland found chlamydia-like organisms in 43 of 235 cases. Sequencing the PCR products revealed no evidence of Wadllia infection although, surprisingly, 9 cases were associated with Parachlamydia acanthamoebae [Borel et al., 2006; 2007].

Field specimens can be screened for W. chondrophila and related organisms using a PCR test which is specific for all bacteria in the order Chlamydiales [Everett et al., 1999; See: Speciation PCR. Further details of PCR probes and of cell culture are given in the review of Corsaro and Greub, 2006.

See also: Evolutionary divergence of chlamydiae in the chlamydial evolution section.

[Klaus Henning, September 2003 updated by MEW March 2008]

Waddlia malayensis

During a search for the natural reservoir of Nipah virus encephalitis, urine was collected on plastic sheeting underneath roosting sites of the fruit bat Eonycteris spelaea at Gua Tempurong in northern Malaysia. From the urine 23 isolates of infectious agent capable of causing cytopathogenic effect (CPE) in Vero cells within 5 – 7 days of culture were obtained [Chua, 2003; Chua et al., 2005]. The organism grew rapidly in cell culture in the absence of cycloheximide [MEW comment: the authors say chlorhexidine]. Inclusions visible by phase-contrast microscopy could be detected within 48 to 72 h postinfection of Vero cells. These inclusions could be stained by both Giemsa and the Schiff reaction, but not with Microtrak C. trachomatis MOMP-specific monoclonal antibody. Transmission electron microscopy revealed a typical chlamydial dimorphic developmental cycle. The 16S rRNA gene, the 16S-23S rRNA intergenic spacer and part of the 23SrRNA gene were sequenced bidirectionally [Chua et al., 2005]. The gene signatures had 91% identity with W. chondrophila sequences AF346001 and AF042496. Like W. chondrophila the organism was able to grow in a variety of host cells, was resistant to penicillin and streptomycin but sensitive to tetracycline, and inclusions were surrounded by mitochondria. Unlike W. chondrophila the host was markedly different and its inclusions were intensely Schiff stain positive suggesting a glycogen-like matrix. It was suggested this is a distinct species within the Waddliaceae and the authors proposed the name W. malayensis [Chua et al., 2005].

[MEW comment: No formal taxonomic description of the proposed new species has been published in IJSEM or elsewhere. The requirement for the type isolate of the proposed species to be deposited in two culture collections in two different countries has not been met. W. malayensis is not included in the IJSEM validation lists to date. This is unlikely to be a formally valid species proposal; see TaxonomyRules].