Comparison of DNA-spot hybridization, cell culture and direct immunofluorescence staining for the diagnosis of avian chlamydiae

Detection of Chlamydophila (Chlamydia) abortus and Toxoplasma gondii in smears from cases of ovine and caprine abortion by the streptavidin-biotin method

Fetal membranes from 59 cases of ovine and six of caprine abortion from a total of 52 flocks or herds were collected. Immunohistochemical examination of cotyledons fixed in formalin and embedded in paraffin wax detected Chlamydophila abortus in 44 (68%) cases. Immunocytochemical examination of smears made from the surface of fetal membranes detected the organism in 37 (57%) cases. Light microscopical examination of such smears stained by Stamp's method detected C. abortus in 26 (40%) cases. The streptavidin-biotin method described proved to have 100% specificity and 84% sensitivity in the detection of C. abortus in cotyledon smears. Sensitivity could probably be increased still further by the simultaneous examination of smears made from the cut surface of several cotyledons. In five cases Toxoplasma gondii was detected in the cotyledons by immunohistochemical examination. In three of these cases the presence of T. gondii was revealed also by immunocytological examination. In four cases, simultaneous C. abortus and T. gondii infection of the cotyledons was observed. The two pathogens and the lesions caused by them occurred in separate locations.

Methods of detection of Chlamydia psittaci in domesticated and wild birds

OBJECTIVE

To study the occurrence of Chlamydia psittaci in domesticated and wild birds and compare the sensitivity of molecular detection with cell culture isolation.

DESIGN

Study of cell culture isolation and PCR detection of C psittaci in avian samples.

PROCEDURE

Samples were obtained from 485 birds. Domesticated birds were selected at random from pet shops, private aviaries and zoos, while wild birds were captured locally, sampled, and immediately released. Swabs were collected from choanal slit, conjunctiva and cloaca of each bird and pooled. Samples were divided into equal portions for use in PCR dot-blot and cell culture detection. PCR and dot-blot detection was based on the ompB gene.

RESULTS

Prevalence of infection varied markedly between flocks of captive birds. It was highest where there were frequent changes in the flock members or where there were many birds confined in small areas. C psittaci was not detected in wild birds or water birds. The sensitivity of cell culture compared to PCR dot-blot detection was 68%. All samples positive by cell culture were also positive by PCR.

CONCLUSIONS

PCR-dot blot detection of C psittaci in birds appears to be more sensitive than cell culture isolation in this study. C psittaci infection of birds may occur in clinically normal captive birds.

Chlamydia psittaci infections: a review with emphasis on avian chlamydiosis

In the first part of this article the general characteristics of Chlamydia psittaci namely the history, taxonomy, morphology, reproductive cycle, metabolism and genetics are reviewed. For the taxonomy in particular, a considerable amount of new information has become available in recent years, following the application of monoclonal antibodies and restriction enzymes. Using these techniques isolates of Chlamydia psittaci from birds have been subdivided in different serovars, a number of isolates have been classified in a new species (Chlamydia pecorum) and isolates from animals have been classified as Chlamydia trachomatis. In the second part of the article, the current knowledge on avian chlamydiosis is summarized. Emphasis is put on clinical signs, lesions, pathogenesis, epizootiology, immunity, diagnosis, prevention and treatment. Also the public health considerations are reviewed. It is concluded that the diagnosis of avian chlamydiosis is laborious and that there is still a need for more accurate, simple and rapid diagnostic tools, both for antigen and antibody detection in various species of birds.

Evaluation of five immunoassays for detection of Chlamydia psittaci in cloacal and conjunctival specimens from turkeys

Five commercially available immunoassays were evaluated for the detection of Chlamydia psittaci in cloacal and conjunctival swabs from industrially raised turkeys: IMAGEN (DAKO Diagnostics, Ely, Cambridgeshire, United Kingdom), Chlamydia CEL-VET IF (Cellabs, Brookvale, Australia), IDEIA (DAKO Diagnostics), CELISA (Cellabs), and CLEARVIEW (Unipath, Bedford, United Kingdom). Results were compared with isolation in Buffalo Green Monkey cells as a reference method. For the conjunctival samples, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 66, 0, 0, and 0%, respectively, as compared to the reference test. Also for the conjunctival samples, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, and the IDEIA were found to be 100, 11, and 92.8%, respectively. For the cloacal specimens, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 93.3, 26.6, 0, and 53.3%, respectively. Also for the cloacal specimens, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, and the CLEARVIEW test were found to be 92, 12, 100, and 88%, respectively. The IMAGEN test was the most sensitive and specific direct chlamydia antigen detection test for cloacal and conjunctival samples from turkeys.

Diagnosis of avian chlamydiosis: specificity of the modified Giménez staining on smears and comparison of the sensitivity of isolation in eggs and three different cell cultures

For the diagnosis of chlamydiosis in dead and live birds different methods were compared for their sensitivity and specificity. The specificity of the modified Giménez staining and the direct immunofluorescence (DIF) test for direct demonstration of Chlamydia psittaci in organ, cloacal and/or conjunctival smears was examined. The sensitivity of the isolation of Chlamydia psittaci in 6 days embryonated specific pathogen free (SPF) chicken eggs, Buffalo Green Monkey (BGM) cell line, McCoy cell line and Vero cell line was compared. On smears, the direct immunofluorescence test was more specific than the modified Giménez staining. The concordance between the results of both detection methods was 80%. The BGM cell culture was the most sensitive artificial host for isolation of Chlamydia psittaci, followed by the embryonated eggs, the Vero cell line and the McCoy cell line. The concordance between the results of isolation in BGM cell culture and eggs was 96.5%, while it was 86% between the results of isolation in BGM cell culture and Vero cell culture and only 65.5% between the results of isolation in BGM cell culture and McCoy cell culture. For dead bird species, chlamydiosis could be diagnosed more often using DIF on smears than with isolation. The concordance between the results of the DIF on smears and isolation followed by DIF was 91%.

Detection of Chlamydia psittaci in free-ranging koalas (Phascolarctos cinereus): DNA hybridization and immuno-slot blot analyses

DNA-slot hybridization and immuno-slot blot analyses were compared for the detection of Chlamydia psittaci in crude swab material from free-ranging koalas. Immuno-slot blot analysis detected chlamydiae in 43 out of 68 koalas, with the sensitivity of the assay varying from 52 to 73% depending on the site of infection. Gene probe analysis was also used employing a genus-specific probe pCKO-10 isolated from a koala chlamydial gene library (ocular strain) and a plasmid probe pCKU cloned from a urogenital strain. The sensitivity of these two assays was comparable and they were considerably more efficient than the immuno-slot blot method for the detection of chlamydiae. Comparison of these data with a cell-culture method of detection, previously used with the same samples, demonstrated that gene probe analysis detected more positives than observed with cell culture. However, this appears to reflect more on the condition of the swab material rather than the sensitivity of the method.