In this case-control study, we investigated the seroprevalence and molecular evidence of Chlamydia trachomatis and Waddlia chondrophila in ectopic pregnancies (EP) and uneventful control pregnancies in 343 women from Vietnam. Whereas presence of C. trachomatis IgG was strongly associated with EP [adjusted odds ratio (aOR) 5·41, 95% confidence interval (CI) 2·58–11·32], its DNA remained undetected in all tubal lesions. We confirmed an independent association between antibodies against Waddlia and previous miscarriage (aOR 1·87, 95% CI 1·02–3·42). Further investigations are needed to understand the clinical significance of Waddlia's high seroprevalence (25·9% in control pregnancies) in this urban population.

Insect cell lines provide useful in vitro models for studying biological systems, including interactions between mosquitoes and obligate intracellular endosymbionts such as Wolbachia pipientis. The Aedes albopictus Aa23 cell line was the first cell line developed to allow examination of Wolbachia infections. However, Wolbachia studies using Aa23 can be complicated by the presence of different cell types in the cell line and the substantial temporal variation in infection level. Two approaches were examined to ameliorate infection variability. In the first approach, multiple Aa23 passaging regimes were tested for an effect on infection variability. Fluorescence in situ hybridization (FISH) staining was used to characterize Wolbachia infection level over time. The results demonstrate an impact of passaging method on Wolbachia infection level, with some methods resulting in loss of infection. None of the passaging methods succeeded in effectively mitigating infection level variation. In a second approach, the clonal C7-10 A. albopictus cell line was infected with Wolbachia from Aa23 cells and Drosophila simulans (Riverside), resulting in cell lines designated C7-10B and C7-10R, respectively. Characterization via FISH staining showed greater stability and uniformity of Wolbachia infection in C7-10R relative to the infection in C7-10B. Characterization of the Aa23, C7-10B and C7-10R lines is discussed as a tool for the study of Wolbachia-host cell interactions.

The presence of intracellular bacteria in the dinoflagellate Gyrodinium instriatum Freudenthal & Lee has previously been described but the bacterial flora associated with this species has not been characterized. In this study, new results of transmission electron microscopy (TEM) and in situ hybridization using several bacterial group-specific oligonucleotide probes are presented. The long-term association of endocytoplasmic and endonuclear bacteria with G. instriatum has been confirmed. All endonuclear and most of the endocytoplasmic bacteria labelled were identified as belonging to the betaproteobacteria. Large clusters of Cytophaga-Flavobacterium-Bacteroides (CFB) were labelled and observed in the cytoplasm of the dinoflagellate cells, but were absent from the nucleus. Gammaproteobacteria were only observed outside the dinoflagellates. No alphaproteobacteria were detected either free-living or intracellular. Empirical observation of intracellular CFB reflected a degradation process of moribund dinoflagellate cells, whereas the systematic colonization of dinoflagellate nucleoplasm by betaproteobacteria suggested a true symbiotic relationship. Natural colonization may have occurred, perpetuated by vertical transmission of intracellular bacteria to the dinoflagellate daughter cells, via a pool of bacteria sequestered within the nucleus. Dividing bacteria were observed in the nucleus and equilibrium may be maintained by release of endonuclear bacteria to the cytoplasm through nuclear envelope constrictions.