Pseudomonas aeruginosa adhesion to normal and injured respiratory mucosa

Human nasal polyps outgrowth culture were used to study the adhesion of Pseudomonas aeruginosa to respiratory cells. By transmission electron microscopy, bacteria associated with ciliated cells were identified trapped at the extremities of cilia, usually as aggregates of several bacterial cells. They were never seen at the interciliary spaces or attached along cilia. Bacteria were also seen to adhere to migrating cells of the periphery of the outgrowth culture. Using a model of repair of wounded respiratory epithelial cells in culture, we observed that the adhesion of P. aeruginosa to migrating cells of the edges of the repairing wounds was significantly higher than the adhesion to non-migrating cells and that adherent bacteria were surrounded by a fibrocnectin-containing fibrillar material The secretion of extracellular matrix components is involved in the process of epithelium repair following injury. To investigate the molecular basis of P. aeruginosa adhesion to migrating cells, bacteria were treated with a fibronectin solution before their incubation with the respiratory cells. P. aeruginosa treatment by fibronectin significantly increased their adhesion to migrating cells. Accordingly, we hypothesize that during cell migration, fibronectin secreted by epithelial cells may favour P. aeruginosa adhesion by establishing a bridge between the bacteria and the epithelial cell receptors. Such a mechanism may represent a critical step for P. aeruginosa infection of healing injured epithelium.

Prevalence of antibodies to Hepatitis C virus in populations at low and high risk for sexually transmited diseases in Rio de Janeiro

In order to investigate the sexual transmission of the Hepatitis C Virus (HCV), the prevalence of specific antibodies in populations at high and low risk for sexually transmitted diseases (STDs) was evaluated. The population at low risk for STDs was composed of persons who voluntarity donated blood at the Hospital Universitário Clementino Fraga Filho (HUCFF) between July and November, 1990 (n = 2494). The population at high risk for STDs was drawn from an ongoing study on the natural history of Human Immunodeficiency Virus (HIV) infection (n = 210, 187 with sexual risk factors for HIV infection). All samples were screened using a first generation ELISA. Repeat reactive samples were then tested in a second generation RIBA. For all ELISA positive samples, two sex and age-matched ELISA negative controls were selected. Data pertaining to the presence of antibodies to the Hepatitis B core antigen (anti-HBC antibodies) and to Treponema pallidum were abstracted from the medical records. The prevalence of RIBA 2 confirmed HCV infection among the blood donors was 2.08%, which is well above the reported prevalence in similar populations from developed western countries. Among the HIV infected homosexuals, the encountered prevalence was 7.96% (p < 0.0005). For the whole group with sexually acquired HIV infection, the prevalence was 8.02% (p < 0.000005). Anti-HBc antibodies were more frequently present in anti-HCV RIBA-2 confirmed positive blood donors than in controls (p < 0.001). 33.3% of the HCV-positive blood donors and 11.04% controls were found to be anti-HBc positive (p < 0.0005). As for the FTA-ABs, 17.6% HCV-positive donors and 4,9% controls were positive (p < 0.01). 5.9% samples from blood donors were both anti-HBc and FTA-ABS positive, whereas none of the controls reacted in both tests (p < 0.05). The association between HCV, Hepatitis B infection and syphilis in individuals at low risk for parenterally transmitted diseases suggests that sexual transmission contributes to the maintenance of the endemicity of HCV in the local population.

Trypanosoma cruzi infection in the opossum Didelphis marsupialis: absence of neonatal transmission and protection by maternal antibodies in experimental infections

The high rate of natural Trypanosoma cruzi infection found in opossums does not always correlate with appreciable densities of local triatomid populations. One alternative method which might bypass the invertebrate vector is direct transmission from mother to offspring. This possibility was investigated in five T. cruzi infected females and their litters (24 young). The influence of maternal antibodies transferred via lactation, on the course of experimental infection, was also examined. Our results show that neonatal transmission is probably not responsible for the high rate of natural T. cruzi infection among opossums. In addition antibodies of maternal origin confer a partial protection to the young. This was demonstrated by the finding of a double prepatency period and 4,5 fold lower levels of circulating parasites, in experimentally infected pouch young from infected as compared to control uninfected mothes. On the other hand, the duration of patent parasitemia was twice as long as that observed in the control group.

Dengue in Brazil - situation, transmission and control: a proposal for ecological control

This article discusses dengue in terms of its conceptual and historical aspects, epidemiological and clinical/pathological nature, and evolution up to the present situation in Brazil. The author discusses the ecological relationship in both the production of dengue and its control. Comparison is made between traditional dengue-control programs and a proposed socially-controlled program of an ecological nature without the use of insecticides. Stress is placed on interdisciplinary technical and scientific activity, broadbased participation by communities in discussing methodological aspects involving them, and prospective evaluation comparing the communities selected for intervention and control communities with regard to clinical and subclinical dengue cases and vector infestation rates in relation to climatic, socio-economic, and behavioural factors.