Detection of Chlamydia trachomatis by in situ hybridization with sulphonated total DNA

Chlamydia pneumoniae in vitro and in vivo: a critical evaluation of in situ detection methods

AIMS

There is a considerable discrepancy between data from the detection of Chlamydia pneumoniae in atherosclerotic lesions obtained by means of immunocytochemistry and data obtained using the polymerase chain reaction. This study evaluated methods for the in situ detection and assessment of the viability of C pneumoniae bacteria.

METHODS

Chlamydia pneumoniae membrane protein, heat shock protein 60, and lipopolysaccharide were detected by immunocytochemistry, and genomic DNA and 16S rRNA by in situ hybridisation in paraffin wax embedded sections of cultured HEp2 cells infected with C pneumoniae and of lungs from mice infected intranasally with C pneumoniae.

RESULTS

Inclusions reactive for all three antigens, DNA, and 16S rRNA were seen in infected HEp2 cells, in all positive bronchus and alveolar epithelial cells, and in some of the positive infiltrate cells in the lungs of mice up to seven days after infection. In all alveolar macrophages and in the infiltrate cells positive for antigens only, the staining pattern was granularly dispersed throughout the cytoplasm up to seven days after infection. At 21 days after infection, only this granular staining pattern was seen for antigens in infiltrate cells and macrophages in the alveoli and bronchus associated lymphoid tissue. At this time point, DNA or 16S rRNA were detected sporadically, but always as inclusion-like staining.

CONCLUSIONS

Because antigens with an inclusion-like staining were detected only together with DNA and 16S rRNA, this type of staining pattern suggested the presence of viable bacteria. Thus, the granular staining pattern of antigens in the absence of staining for DNA and 16S is most likely caused by non-viable bacteria. In conclusion, these methods are suitable for the in situ detection of C pneumoniae and the assessment of its viability.

In situ hybridization for the detection and localization of swine Chlamydia trachomatis

Gnotobiotic piglets were inoculated intralaryngeally with swine Chlamydia trachomatis strain R33 or orally with swine C. trachmatis strain R27. Archived formalin-fixed, paraffin-embedded tissues from piglets euthanatized 4-7 days postinoculation were examined by in situ hybridization for C. trachomatis nucleic acid using a nonradioactive digoxigenin-labeled DNA probes that targeted specific ribosomal RNA or omp1 mRNA molecules of the swine C. trachomatis strains. Positive hybridization signals were detected in bronchial epithelial cells, bronchiolar epithelial cells, pneumocytes, alveolar and interstitial macrophages, and jejunal and ileal enterocytes. Chlamydia-infected cells had a strong signal that was confined to the intracytoplasmic inclusions. Positive hybridization signals were not detected in tissue sections from an uninfected control piglet or in C. psittaci-infected sheep placenta. The morphology of host cells was preserved despite the relatively high temperature required in parts of the incubation procedure. The data indicate that in situ hybridization can be used to detect swine C. trachomatis in formalin-fixed, paraffin-embedded tissue specimens.

Case report: in situ hybridization for detection of inapparent infection with Chlamydia trachomatis in synovial tissue of a patient with Reiter's syndrome

The authors have shown that protein antigens, RNA, and DNA from Chlamydia trachomatis are present in synovial tissues of patients with Reiter's syndrome (RS). However, those studies gave no insight into the host cell type involved or the precise tissue location of the bacteria. To address such issues, the authors developed an in situ hybridization system to detect chlamydia, and they used that system to examine synovial biopsies from a patient with RS and a patient without RS. The in situ system uses a previously described digoxigenin-labeled DNA probe that hybridizes with chlamydial 16S rRNA sequences in paraformaldehyde-fixed samples. Control studies with chlamydia-infected and uninfected HeLa cells confirmed that the in situ system is as sensitive as is direct fluorescence cytology for detection of the organism. Morphology of host and chlamydia cells is preserved after hybridization. Studies using synovial tissue from an osteoarthritis patient produced no in situ hybridization signal, but similar hybridization to tissue from a culture-/direct fluorescence cytology- negative RS patient had a strong intracellular signal for chlamydia within a subsynovial cell layer. These in situ hybridization results confirm the extensive presence of chlamydia in synovia and extend the authors' earlier observation that chlamydia RNA is present in the synovia of patients with RS. The data also confirm their electron microscopy studies, indicating that chlamydia are intracellular in synovial tissue, and they further show that infected host cells are located beneath the synovial lining.

An Atypical Acidophil Cell Line Tumor Showing Focal Differentiation Toward Both Growth Hormone and Prolactin Cells

We report a case of giant pituitary adenoma in a child. Computerized tomography (CT) scan revealed a suprasellar extension tumor mass with hydrocephalus. There was no clinical evidence of acromegaly, gigantism, and other hormonal symptoms. Endocrinologic studies showed within normal value of serum growth hormone (GH: 4.2 ng/mL) and slightly increased levels of prolactin (PRL: 78 ng/mL) and other pituitary hormone values were within normal range. On suppression test by bromocryptin, both GH and PRL levels were reduced. Histopathological findings revealed that the tumor consisted of predominantly chromophobic and partly eosinophilic adenoma cells. Immunohistochemical staining detected GH and PRL in a small number of distinctly different adenoma cells, respectively. Nonradioactive in situ hybridization (ISH) also showed GH and PRL mRNA expression in identical immunopositive cells. Electron microscopy (EM) demonstrated adenoma cells with moderate or small numbers of two types of dense granules and without fibrous body which are characteristic of sparsely granulated GH-cell adenomas. The adenoma does not fit into any classification but may be an atypical acidophil cell line tumor showing focal differentiation toward both GH and PRL cells.

Intracellular location of inapparently infecting Chlamydia in synovial tissue from patients with Reiter's syndrome

Culture of Chlamydia trachomatis from synovial tissues/fluids from Reiter's syndrome (RS) patients frequently yields negative results. However, we have identified chlamydial RNA at that site in such patients, suggesting that viable organisms may be present. Here we define the cellular location of chlamydia within the synovium via in situ hybridization. Using a chlamydial ribosomal RNA-directed probe, we show that synovial tissue from culture-negative RS patients gives strong hybridization which is often localized to a subsynovial cell layer, rather than to the synovial lining; in some cases, hybridizing cells are dispersed through the synovium. All hybridization signal is located within host cells, indicating that infectious extracellular elementary bodies are rare or absent. These data confirm the extensive intracellular presence of inapparent chlamydia in the synovia of RS patients and provide some insight into the usual culture negativity of synovial tissues for the organism.

Staining of surface antigens of Chlamydia trachomatis L2 in tissue culture

Surface labeling of chlamydial elementary and reticulate bodies in L929 cells infected with Chlamydia trachomatis serotype L2 was monitored by using monoclonal antibodies (MAb) against the major outer membrane protein and lipopolysaccharide (LPS). Different staining and fixation procedures were used to detect these surface antigens during the developmental cycle. Anti-major outer membrane protein MAb yielded a clear staining pattern of exclusively chlamydial inclusions independent of the fixation or staining technique used. Anti-LPS MAb gave a faint staining pattern of reticulate bodies when methanol fixation was used and showed that LPS was released from chlamydiae into the host cell cytoplasm and into the surroundings of the infected host cell. However, when paraformaldehyde-glutardialdehyde fixation was used, extracellular LPS staining was not observed. The data show that chlamydial LPS is loosely bound in the bacterial outer membrane but suggest that shedding of LPS is a fixation artifact.

Laboratory techniques for the diagnosis of chlamydial infections

Yolk-sac inoculation of embryonated eggs was superseded 25 years ago by the use of cell cultures (often McCoy) for the isolation of Chlamydia trachomatis. Centrifugation of specimens onto the cell monolayers was shown to increase sensitivity, but little of late has further improved sensitivity which is at least ten-fold greater than that of eggs. However, culture is slow and labour intensive so that non-cultural techniques without these drawbacks have come to dominate. Direct fluorescent antibody (DFA) tests are rapid and have sensitivities that range from 70% to 100% for men and 68% to 100% for women, and specificities that range from 87% to 99% for men and 82% to 100% for women; if the tests are read by competent observers the values are at the top end of the ranges. The detection rate may be enhanced even further by relatively low-speed centrifugation of specimens before staining. Skilled reading is not a feature of enzyme immunoassays (EIAs) which according to the literature have sensitivities that range from 62% to 97% for men and 64% to 100% for women, and specificities that range from 92% to 100% for men and 89% to 100% for women. However, comparison against poor reference tests is responsible for most of the higher values and the clinician should not be misled into believing that EIAs have excellent sensitivity; the lower values in the ranges are closer to reality. Furthermore, EIAs that are being designed for use by general practitioners should be regarded with the greatest caution since lack of sensitivity means that chlamydia-positive patients will go undetected. The polymerase chain reaction (PCR) is not bedevilled by insensitivity but it is no more sensitive than the most sensitive cell culture or DFA tests. PCR is unsuitable for routine diagnosis but has a place as a research tool. For men, examination of "first-catch" urine samples by the best of the non-cultural procedures provides an acceptable non-invasive approach to diagnosis; for women, the value of examining urine may be less, but needs to be thoroughly tested. However, there is little doubt that a Cytobrush used to obtain cervical specimens holds no practical advantage over a swab. Serological tests are reliant on the provision of paired sera for making a diagnosis; high antibody titres in single sera may be suggestive of an aetiological association in deep-seated chlamydial infections (epididymitis, arthritis, salpingitis, etc), but unequivocal interpretation is unusual, particularly in an individual case, since the distinction between a current and past infection is problematical.

A polymerase chain reaction (PCR) protocol for the specific detection of Chlamydia spp

The polymerase chain reaction is an in vitro procedure for primer-directed enzymatic amplification of specific template nucleic acid sequences. This technique was used to detect and differentiate Chlamydia trachomatis and Chlamydia psittaci in laboratory samples of infected McCoy cells. The polymerase chain reaction was shown to be both sensitive, detecting in the order of one chlamydial DNA molecule in 10(5) cells, and specific. No cross reaction (amplified product) was detected when a variety of mammalian cell and bacterial DNAs were used as template with the Chlamydia-specific oligonucleotide primers.

Identification and classification of Campylobacter strains by using nonradioactive DNA probes

Acetylaminofluorene-labeled genomic DNA probes were used for the identification and classification of Campylobacter strains. Relationships among 17 well-known strains of Campylobacter species and subspecies were studied by comparing acetylaminofluorene- or 32P-labeled probes. Results obtained with both methods were closely correlated and were in agreement with those already reported. In an identification experiment, hybridization with nonradioactive probes was performed on 60 strains isolated from stool samples after subculturing and quick DNA extraction; conventional biochemical tests were conducted in parallel. A good correlation was found between the results obtained by nonradioactive hybridization and by biochemical tests. Thus, the acetylaminofluorene-labeled genomic DNA probe method is an interesting alternative for laboratories without access to radioisotopes for the identification and classification of bacteria.

Specific amplification of a DNA sequence common to all Chlamydia trachomatis serovars using the polymerase chain reaction

Enzymatic DNA amplification was applied to DNA and elementary bodies of C. trachomatis. Oligonucleotide primers were chosen in a sequence of a conserved domain of the major outer membrane protein to generate the amplification of a 129-base pair fragment. This sequence was amplified in the 15 serovars of C. trachomatis; however, serovar J gave a weaker signal than the others. The specificity was controlled by EcoRI restriction enzyme digestion and Southern analysis using an internal probe of the amplified sequence. No cross-reaction was shown with DNA of 11 other bacteria. Thus, enzymatic DNA amplification by the polymerase chain reaction appears to be a potential tool for the specific detection of C. trachomatis.