Comparison of nine antigen detection kits for diagnosis of urogenital infections due to Chlamydia psittaci in koalas

Recent advances in understanding the biology, epidemiology and control of chlamydial infections in koalas

The koala (Phascolarctos cinereus) is recognised as a threatened wildlife species in various parts of Australia. A major contributing factor to the decline and long-term viability of affected populations is disease caused by the obligate intracellular bacteria, Chlamydia. Two chlamydial species infect the koala, Chlamydia pecorum and Chlamydia pneumoniae, and have been reported in nearly all mainland koala populations. Chlamydial infections of koalas are associated with ocular infections leading to blindness and genital tract infections linked to infertility, among other serious clinical manifestations. Diagnosis can be based on clinical presentation alone, however, it is complicated by the observation that many koala chlamydial infections occur with no overt signs of clinical disease. Instead, accurate diagnosis requires detailed clinical assessment and confirmatory testing by a range of PCR-based assays. Antibiotic treatment for koala chlamydial infection is possible, however, results on its success are mixed. A more practical solution for the protection of diseased populations is the application of a koala Chlamydia vaccine, with recent trials indicating promising results. Interestingly, molecular epidemiology studies of koala C. pecorum infections and recent comparative genomic analyses of koala C. pneumoniae have revealed potential differences in their origin that will have wider ramifications for our understanding of human chlamydial infections and host adaptation of the chlamydiae. This review summarises changes to the taxonomy of koala chlamydial infections and recent advances in our understanding of the epidemiology, diagnosis, treatment, control and evolution of Chlamydia infections in this iconic wildlife species.

Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus)

The gold standard method for detecting chlamydial infection in domestic and wild animals is PCR, but the technique is not suited to testing animals in the field when a rapid diagnosis is frequently required. The objective of this study was to compare the results of a commercially available enzyme immunoassay test for Chlamydia against a quantitative Chlamydia pecorum-specific PCR performed on swabs collected from the conjunctival sac, nasal cavity and urogenital sinuses of naturally infected koalas (Phascolarctos cinereus). The level of agreement for positive results between the two assays was low (43.2%). The immunoassay detection cut-off was determined as approximately 400 C. pecorum copies, indicating that the test was sufficiently sensitive to be used for the rapid diagnosis of active chlamydial infections.

Detection of bacterial and viral organisms from the conjunctiva of cats with conjunctivitis and upper respiratory tract disease

A variety of pathogens are involved in conjunctivitis in cats. In this study, the prevalence of feline herpesvirus (FHV), Chlamydophila felis, mycoplasmas, and aerobic bacteria on the conjunctival surface of cats with conjunctivitis and upper respiratory tract disease was investigated by polymerase chain reaction (PCR), immunofluorescent assay (IFA), and aerobic bacterial culture of ocular swabs. Forty-one cats were included of which 37 were found to be infected with an ocular organism. Single and multiple infections were present in 15 and 22 cats, respectively. FHV, mycoplasmas, and C felis were detected by PCR in 11 (27%), 20 (49%), and 23 (56%) cats, respectively. IFA detected 10 cats as positive for C felis. Mycoplasma felis, Mycoplasma canadense, Mycoplasma cynos, Mycoplasma gateae, Mycoplasma lipophilum, and Mycoplasma hyopharyngis were identified by genetic sequencing. The most common aerobic bacteria cultured included Staphylococcus species, Streptococcus species and Micrococcus species. The prevalence of mycoplasmas in cats with conjunctivitis was higher than previously reported, and four of the Mycoplasma species have not been described in cats so far.

Flow cytometric quantification of chlamydial infection in cell culture

A flow cytometric method was developed, which allows fast and efficient analysis of cell cultures infected with chlamydiae. The proportion of positive cells increased with the infectious dose and correlated with chlamydia copy numbers calculated from real-time PCR. While retaining the advantages of single-cell analysis, flow cytometry allows handling of large sample numbers and counterstaining for additional marker proteins.

Recent developments in the laboratory diagnosis of chlamydial infections

There are two main approaches to diagnosing infections by Chlamydia and Chlamydophila spp. in mammals and birds. The first involves the direct detection of the agent in tissue or swab samples, while the second involves the serological screening of blood samples for the presence of anti-chlamydial antibodies. Ultimately, the test that is used is dependent on the types of samples that are submitted to the diagnostic laboratory for analysis. The present paper gives an overview on methodologies and technologies used currently in diagnosis of chlamydial infections with emphasis on recently developed tests. The performance characteristics of individual methods, such as the detection of antigen in smears and in pathological samples, the isolation of the pathogen, various antibody detection tests and DNA-based methods utilising conventional and real-time PCR, as well as DNA microarray technology are assessed, and specific advantages and drawbacks are discussed. Further, a combination of a specific real-time PCR assay and a microarray test for chlamydiae is proposed as an alternative reference standard to isolation by cell culture.

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.

Detection of chlamydial antibody by fetal serology--an aid to the diagnosis of ovine abortion

Two serological tests (indirect immunofluorescence and enzyme-linked immunosorbent assay) were developed for the detection of fetal antibody to Chlamydia psittaci. Fetal blood and thoracic fluid from 126 field cases of suspected ovine chlamydial abortion were examined using both tests. Placenta and fetal tissues (lung, liver, and kidney) from the same animals were also examined by the following conventional diagnostic methods: isolation in McCoy cells, detection of chlamydial lipopolysaccharide (LPS), modified Ziehl-Nielsen staining, and direct fluorescent antibody staining of chlamydia in frozen cryostat sections. Seventy cases were positive by fetal serology, and of these, 68 were also positive by isolation and/or LPS detection. The remaining 56 cases had negative fetal serology, and of these, 39 were positive by isolation and/or LPS detection. Results indicate that fetal serology, although less sensitive than either isolation in McCoy cells or detection of chlamydial LPS antigen, may be of particular use when placenta is not available.

Epizootiology of Chlamydia infections in two free-range koala populations

The prevalence of Chlamydia pecorum and Chlamydia pneumoniae infections in two free-range koala populations was assessed using genus-specific PCR combined with species-specific DNA probe hybridisation. Population A had a very high overall level of chlamydial infection (85%) with significantly more of these infections being due to C. pecorum (73%) compared to C. pneumoniae (24%). The second population had a much lower prevalence of infection (10%) with equal levels of both species. An important finding of this study was that. while five of 24 C. pecorum-infected koalas had clinical signs of the disease (both ocular and urogenital sites), none out of seven C. pneumoniae-infected koalas had signs of clinical disease. This suggests that C. pecorum may be the more pathogenic of the two chlamydial species infecting this host. The level of infection (assessed by intensity of the specific hybridisation signal) also differed between chlamydial species, with C. pecorum infections ranging from low to high grade whereas C. pneumoniae infections were always low grade. When the age of infected koalas was examined, 58% of young, sexually immature koalas were found to have C. pecorum infections, increasing to 100% of koalas in the older age groups. This suggests that, in this population at least, young koalas are readily infected with C. pecorum from their mothers. While the infection levels with C. pneumoniae were too low to be statistically significant, again, sexually immature koalas were found to be infected. The recent separation of chlamydial infections in koalas into two species is beginning to indicate different epizootiologies for koala C. pecorum compared to koala C. pneumoniae.

Polymerase chain reaction for the detection of Chlamydia psittaci in the feces of budgerigars

The polymerase chain reaction (PCR) targeting the ompA gene of Chlamydia psittaci was evaluated for its ability to detect chlamydiae in fecal specimens of budgerigars as compared with isolation procedures using cell culture and embryonated egg inoculations. Several procedures for PCR template DNA preparation were compared so as to determine their detection levels for chlamydiae propagated in cell culture in the presence of fecal materials. Tween-20 and proteinase K treatments followed by centrifugation of the template DNA were found to be an appropriate procedure for DNA preparation for primary PCR. Subsequent nested PCR was shown to detect 4.8 IFU/ml or 84 particles/ml of chlamydiae. Chlamydiae in 50 fecal specimens from apparently healthy budgerigars were examined by nested PCR and several other methods. Nested PCR detected chlamydiae at a higher rate (12/50, 24%) than the isolation procedure in embryonated eggs (6/50, 12%). Primary PCR combined with the isolation procedure in cell culture gave a detection rate (5/50, 10%) similar to that of isolation from embryonated eggs. Detection rates by primary PCR (1/50, 2%) and in cell culture (0%) were inferior to the other procedures.

Comparison of polymerase chain reaction, direct immunofluorescence, cell culture and enzyme immunoassay for the detection of Chlamydia psittaci in bull semen

The polymerase chain reaction (PCR), direct immunofluorescence (DIF; JMAGEN Chlamydia, DAKO Diagnostics, UK), cell culture (CC) and enzyme immunoassay (EIA; Syva Micro Trak) were evaluated for detection of Chlamydia psittaci in bull semen. Three specimens were collected from each of 47 bulls at 3-6 month intervals (134 samples). Judging by the number of samples tested (n = 134), PCR showed a sensitivity of 90.9%, DIF of 93.9%, CC of 72.7% and EIA of 81.8%. PCR, DIF, CC and EIA were 100% specific, respectively. Of the 47 bulls the maximum number of chlamydia-positive animals (n = 14) was revealed when repeated tests were made by PCR. PCR detected 21.4% more positives than DIF and CC and 35.7% more than EIA. Although CC was less sensitive judging by the number of samples tested, it was as sensitive as DIF (78.6%) when judged by the number of bulls investigated. All bulls found to be chlamydia-positive remained so throughout the investigation, which lasted 18 months.

Chlamydia psittaci infection and associated infertility in sheep

Nineteen ewes were injected subcutaneously with the agent of enzootic ovine abortion, Chlamydia psittaci serovar 1, at 50 days gestation. Placental and fetal tissues were examined at 15 days postinfection and thereafter at ten day intervals. Placental infection was detected at 15 days postinfection. Only postinoculation sera collected from postinfected ewes contained antibodies reactive to C. psittaci. Five (26%) chlamydial infected ewes experienced inapparent fetal loss before day 105 of gestation. This finding is significant since C. psittaci infection in sheep is commonly associated with abortion and not infertility.