Serum reactivity toChlamydia trachomatisandC. pneumoniaeantigens in patients with documented infection and in healthy children by microimmunofluorescence and immunoblotting techniques

Chlamydia pneumoniae IgG serological status and venous thromboembolism: a cross-sectional hospital based study

OBJECTIVE

To search for a link between Chlamydia pneumoniae serological status and venous thromboembolic disease.

METHODS

From March 1992 to October 1999, we conducted a cross-sectional hospital-based study of consecutive unselected outpatients referred to us for clinical suspicion of venous thromboembolism. We compared the Chlamydia pneumoniae serological status with respectively, the venous thromboembolism, the deep vein thrombosis and the proximal deep vein thrombosis status.

RESULTS

Among 1193 patients registered for suspected venous thromboembolism, 1010 samples were available (499 negative and 511 positive patients for venous thromboembolism). Seventy-nine patients were Chlamydia pneumoniae positive. Our work failed to demonstrate any clear association between Chlamydia pneumoniae and venous thromboembolism status. Nevertheless, we identified a statistical difference regarding Chlamydia pneumoniae seropositivity and proximal vein thrombosis status (adjusted odds ratio of 1.70, CI95%: 1.05 to 2.77).

CONCLUSION

The presence of Chlamydia pneumoniae antibodies might be a minor risk factor for venous thrombosis.

Evidence for the presence of Simkania negevensis in drinking water and in reclaimed wastewater in Israel

Simkania negevensis is a recently discovered chlamydia-like intracellular microorganism which has been associated with bronchiolitis in infants and with community-acquired pneumonia in adults; a high seroprevalence of antibodies to the microorganism has been found in various population groups. S. negevensis can be grown in various cell lines as well as in free-living amoebae such as Acanthamoeba polyphaga. In this study, evidence for the existence of Simkania or Simkania-like microorganisms in drinking water and in reclaimed wastewater is presented for the first time. Detection of the microorganism was made possible by the development of a specific and sensitive filter membrane immunoassay and was confirmed by PCR detection of microbial DNA in the water samples. The common presence of S. negevensis in water sources together with the high seroprevalence of antibodies to it and early age of acquisition of infection may implicate water as a source of infection. The possible significance of this finding for public health and for municipal water testing and treatment needs to be further examined.

The growth cycle of Simkania negevensis

Simkania negevensis, a bacterium formerly referred to as 'the micro-organism Z' or 'Simkania Z', belongs to the order Chlamydiales, assigned to the family Simkaniaceae: The purpose of this study was to investigate the production of Simkania negevensis progeny in infected cells in comparison with the well-documented Chlamydiaceae developmental cycle. It was found that replicating Simkania negevensis in Vero cells resembled the reticulate bodies of all known chlamydial species: in electron micrographs they were reticulated, homogeneously staining, and often caught in the process of binary division. These replicative forms were found in low abundance shortly after infection, but by 3 days post-infection they were the most prevalent particles in host cells. Electron-dense forms of Simkania negevensis began to appear on the third day post-infection, but quantitatively did not account for the high titre of infectivity in extracts from these host cells. These had both electron-dense and electron-lucent areas, a characteristic seen only in a few chlamydial species. Simkania negevensis infectivity did not appreciably change during the ensuing 12 days required for host cell lysis, despite an eightfold increase in the proportion of electron-dense bacteria over this time. The emergence of electron-dense bodies, increase in infectivity and host-cell lysis were not synchronized developmental events. This is a novel finding in Chlamydiales spp. and suggests that Simkania negevensis will provide new perspectives in the mechanisms of chlamydial intracellular growth.

Diagnostic methods for intracellular pathogens

Diagnosis of infection with Chlamydia pneumoniae is difficult and the optimal diagnostic procedure has yet to be established. C. pneumoniae is more difficult to isolate in tissue culture than C. trachomatis. Attention must be paid to the site from which the specimen is taken, and all specimens should be processed within 24 h or stored at 4 C. Serologic diagnosis largely depends on microimmunofluorescence testing which, despite proposed criteria, still has a large subjective component. Serology has limitations in terms of both sensitivity and specificity and antibodies may be difficult to detect in individuals with positive C. pneumoniae cultures. Non-culture methods include enzyme immunoassays, fluorescent-antibody techniques and DNA probes. The most promising appears to be PCR. Co-infection of C. pneumoniae and other respiratory organisms seem to be common.