Role of Waddlia chondrophila placental infection in miscarriage.

Waddlia chondrophila is an intracellular bacterium suspected to cause human and bovine abortion. We confirmed an association between antibodies against W. chondrophila and human miscarriage and identified this organism in placenta or genital tract of women who had had miscarriages. These results suggest a possible role of W. chondrophila infection in miscarriage.

Role of Chlamydia trachomatis in miscarriage.

To determine the role of Chlamydia trachomatis in miscarriage, we prospectively collected serum, cervicovaginal swab specimens, and placental samples from 386 women with and without miscarriage. Prevalence of immunoglobulin G against C. trachomatis was higher in the miscarriage group than in the control group (15.2% vs. 7.3%; p = 0.018). Association between C. trachomatis-positive serologic results and miscarriage remained significant after adjustment for age, origin, education, and number of sex partners (odds ratio 2.3, 95% confidence interval 1.1-4.9). C. trachomatis DNA was more frequently amplified from products of conception or placenta from women who had a miscarriage (4%) than from controls (0.7%; p = 0.026). Immunohistochemical analysis confirmed C. trachomatis in placenta from 5 of 7 patients with positive PCR results, whereas results of immunohistochemical analysis were negative in placenta samples from all 8 negative controls tested. Associations between miscarriage and serologic/molecular evidence of C. trachomatis infection support its role in miscarriage.

Histone deacetylase inhibitors impair innate immune responses to Toll-like receptor agonists and to infection.

Regulated by histone acetyltransferases and deacetylases (HDACs), histone acetylation is a key epigenetic mechanism controlling chromatin structure, DNA accessibility, and gene expression. HDAC inhibitors induce growth arrest, differentiation, and apoptosis of tumor cells and are used as anticancer agents. Here we describe the effects of HDAC inhibitors on microbial sensing by macrophages and dendritic cells in vitro and host defenses against infection in vivo. HDAC inhibitors down-regulated the expression of numerous host defense genes, including pattern recognition receptors, kinases, transcription regulators, cytokines, chemokines, growth factors, and costimulatory molecules as assessed by genome-wide microarray analyses or innate immune responses of macrophages and dendritic cells stimulated with Toll-like receptor agonists. HDAC inhibitors induced the expression of Mi-2ß and enhanced the DNA-binding activity of the Mi-2/NuRD complex that acts as a transcriptional repressor of macrophage cytokine production. In vivo, HDAC inhibitors increased the susceptibility to bacterial and fungal infections but conferred protection against toxic and septic shock. Thus, these data identify an essential role for HDAC inhibitors in the regulation of the expression of innate immune genes and host defenses against microbial pathogens.

Antibiotic susceptibility of Waddlia chondrophila in Acanthamoeba castellanii amoebae.

Waddlia chondrophila is an emerging cause of miscarriage in bovines and humans. Given the strict intracellular growth of this Chlamydia-like organism, its antibiotic susceptibility was tested by amoebal coculture, cell culture, and real-time PCR. W. chondrophila was susceptible to doxycycline and azithromycin but resistant to beta-lactams and fluoroquinolones.

Waddlia chondrophila enters and multiplies within human macrophages.

Waddlia chondrophila is an obligate intracellular bacterium of the Chlamydiales order. W. chondrophila has been isolated twice from aborted bovine foetuses and a serological study supported the abortigenic role of W. chondrophila in bovine species. Recently, we observed a strong association between the presence of anti-Waddlia antibodies and human miscarriage. To further investigate the pathogenic potential of W. chondrophila in humans, we studied the entry and the multiplication of this Chlamydia-like organism in human macrophages. Confocal and electron microscopy confirmed that W. chondrophila is able to enter human monocyte-derived macrophages. Moreover, W. chondrophila multiplied readily within macrophages. The proportion of infected macrophages increased from 13% at day 0 to 96% at day 4, and the mean number of bacteria per macrophage increased by 3logs in 24h. Intracellular growth of W. chondrophila was associated with a significant cytopathic effect. Thus, W. chondrophila may enter and grow rapidly within human macrophages, inducing lysis of infected cells. Since macrophages are one of the major components of the innate immune response, these findings indirectly suggest the possible human pathogenicity of W. chondrophila.

The Neff strain of Acanthamoeba castellanii, a tool for testing the virulence of Mycobacterium kansasii.

Virulent Mycobacterium kansasii (mainly subtype 1) may cause lung infections, whereas certain other strains (essentially subtype 3) are commonly non-pathogenic mycobacteria colonizing the human lower respiratory tract of patients. Determining the clinical significance of a strain isolated from a respiratory sample represents a major challenge for clinicians. Since some mycobacteria may use free-living amoebae as a training ground to select virulence traits, we wondered whether the Acanthamoeba castellanii amoeba could be used to determine the virulence of these intracellular bacteria. We investigated whether the growth and cytopathic effect of M. kansasii in A. castellanii correlate with the virulence of M. kansasii determined clinically and by subtyping. Pathogenic subtype 1 M. kansasii strains grew better in A. castellanii than non-pathogenic subtype 3 strains when considering both the number of bacteria per amoeba and the percentage of infected amoebae. Moreover, a subtype 3 M. kansasii strain isolated from blood culture, and thus considered pathogenic, was revealed to grow in A. castellanii similarly to pathogenic subtype 1 strains. These results suggest that amoebae may represent useful tools for testing the virulence of intracellular mycobacteria and other amoeba-resisting bacteria. This is important, since identification of novel bacterial virulence factors relies largely on in vitro assessment of virulence.

'Candidatus Rhabdochlamydia crassificans', an intracellular bacterial pathogen of the cockroach Blatta orientalis (Insecta: Blattodea).

The genus Rickettsiella comprises various intracellular bacterial pathogens of arthropods, exhibiting a chlamydia-like developmental cycle. Species may be divided into two main groups, the R. popilliae-R. grylli group and the R. chironomi group. Previous phylogenetic studies based on the 16S ribosomal RNA encoding gene showed that two Rickettsiella species, one from each group, belong in reality to two distantly related lineages, the gamma-Proteobacteria (R. grylli) and the Chlamydiales ('Candidatus Rhabdochlamydia porcellionis', a pathogen of terrestrial isopods). In the present work, the 16S rDNA sequence of another Rickettsiella-like species, causing abdominal swelling to its cockroach host Blatta orientalis, was determined and phylogenetic analysis performed. Identical 16S rDNA sequences of 1495 nucleotides were obtained from fat body and ovary tissues of both healthy and diseased cockroach individuals. The sequence shared only 73% of similarity with R. grylli, but 82-87% with most Chlamydiales, and even 96.3% with 'Candidatus Rhabdochlamydia porcellionis'. Phylogenetic analyses confirmed the affiliation of the cockroach pathogen within the order Chlamydiales, and based on ultrastructural characteristics and genetic analyses, we propose its inclusion in the 'Candidatus Rhabdochlamydia' as a distinct taxon, 'Candidatus Rhabdochlamydia crassificans'. These results extend our knowledge of the phylogenetic diversity of the Chlamydiales.