|To detect and characterize the full range of chlamydial infections in cats with ocular disease, Dr. Wolf von Bomhard from the Veterinary Faculty, University of Zurich, and colleagues used polymerase chain reaction (PCR) assays, performed cytologic examination and immunohistochemical analysis and evaluated clinical information including status for feline herpesvirus-1 (FeHV-1).
As sample population the scientists extracted DNA from 226 conjunctival samples obtained from cats with clinically diagnosed keratitis or conjunctivitis and 30 conjunctival samples from healthy cats.
Then they performed PCR assays for the 16S rRNA gene specific for the order Chlamydiales and a new Chlamydophila felis (formerly Chlamydia psittaci) species-specific 23S rRNA gene. Seventy-four conjunctival samples they prepared with Romanowsky-type stain, grouped on the basis of inflammatory pattern, and screened them for chlamydial inclusions by use of immunohistochemical analysis. Clinical information and FeHV-1 status were recorded.
As results 26 (12 percent) specimens had positive results for the only known feline chlamydial pathogen, C felis. Surprisingly, an additional 88 (39 percent) were positive for non-C felis chlamydial DNA. Identification of non-C felis chlamydial DNA by direct sequencing revealed 16S rRNA gene sequences that were 99 percent homologous to the sequence for Neochlamydia hartmannellae, an amebic endosymbiont. Chlamydial prevalence was significantly higher in cats with ocular disease.
Application of a broad-range detection method resulted in identification of a new agent associated with ocular disease in cats. Finding chlamydia-like agents such as N hartmannellae in coinfections with their obligate amebic host, Hartmannella vermiformis, raises questions about the potential role of these microorganisms in causation or exacerbation of ocular disease in cats, the scientists concluded.
Source: American Journal of Veterinary Research 2003, Vol. 64, No. 11, pp. 1421 - 1428.
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