Fibronectin and alpha5beta1 integrin mediate binding of Pseudomonas aeruginosa to repairing airway epithelium.

Initial infection of the airway by Pseudomonas aeruginosa may occur through a variety of bacterial strategies including binding to epithelial receptors present at the surface of the respiratory epithelium. In order to characterize the adherence sites for P. aeruginosa in damaged and repairing bronchial tissue, an ex vivo model of airway epithelial injury and repair was developed using primary cell cultures of nasal cells from 14 subjects with polyposis. P. aeruginosa strongly adhered to flattened dedifferentiated (FD) bronchial and nasal cytokeratin 13-positive epithelial cells in the process of migration for repair. In in vitro experiments, competitive binding inhibition assays demonstrated that alpha5beta1 integrins and cellular fibronectin, in particular the RGD sequence, are receptors involved in P. aeruginosa adherence to FD nasal epithelial cells. Fluorescent cell sorting analysis and immunofluorescence techniques revealed that the alpha5beta1 integrins are overexpressed and apically exposed in FD nasal epithelial cells. One 50 kDa outer membrane protein was identified in piliated and nonpiliated strains of P. aeruginosa that was involved in binding to cellular fibronectin and alpha5beta1 epithelial integrins. These results demonstrate that Pseudomonas aeruginosa adherence is related to the dedifferentiation of airway epithelium during the repair process which unmasks and upregulates the alpha5beta1 integrin expression and induces active synthesis of cellular fibronectin. These epithelial receptors are then used by a Pseudomonas aeruginosa 50 kDa outer membrane protein as sites of bacterial adherence.

Pseudomonas aeruginosa internalization by human epithelial respiratory cells depends on cell differentiation, polarity, and junctional complex integrity.

Internalization of Pseudomonas aeruginosa by epithelial respiratory cell lines has been suggested to be dependent on the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Because we have observed intracellular (IC) P. aeruginosa only in cells that do not express apical CFTR, we addressed the question of whether bacterial internalization by epithelial cells depends on the degree of cell differentiation and polarity. Internalization of piliated P. aeruginosa PAO-1 and PAK by human epithelial respiratory cells in primary culture and by the 16 human bronchial epithelial 14o- cell line cultured either on thick collagen gels or on thin collagen films was evaluated by the gentamicin exclusion assay. Cells cultured on thick gels were differentiated, polarized, and tight. They exhibited CFTR at their apical membranes, expressed beta1 integrins at their basal membranes, excluded lanthanum nitrate, and uniformly expressed ZO-1 protein. In contrast, in cells cultured on thin films, CFTR was present mainly in the cytoplasm, whereas beta1 integrins were detected at apical membranes. Most cells cultured on thin films did not exclude lanthanum nitrate and rarely expressed ZO-1 protein. Cells grown on thick and thin collagen substrates differed markedly in bacterial internalization: no IC bacteria could be detected in cells cultured on gels, whereas high IC bacterial concentrations were isolated from cells cultured on thin films. Treatment of cells cultured on thin films with ethylenediaminetetraacetic acid, to disrupt intercellular junctions further, significantly enhanced P. aeruginosa internalization. Our results suggest that P. aeruginosa internalization by epithelial respiratory cells does not depend on CFTR protein expression at the epithelial cell surface but rather on cell polarity and junctional complex integrity.

[Epidemiology of hospital bacteremias in eastern France. Eastern CCLIN Network]. / Epidémiologie des bactériémies nosocomiales dans l'Est de la France. Reseau CCLIN Est.

Bacteremia occurs frequently among critically ill patients. The aim of this study carried out in Eastern France was to describe the epidemiology of nosocomial bacteremia and to assess the methicillin-resistance of Staphylococcus aureus (SA). Data were collected during a 4 months prospective survey (09/96-12/96) carried out among 44 hospitals. We counted 2633 episodes of bacteremia classified as contamination (684), nosocomial bacteremia (970) and community bacteremia (979). Incidence rate of nosocomial bacteremia was 30.7 per 100 beds in the intensive care units. When documented, the origin of the nosocomial bacteremia was the most often catheter blood related infection or urinary tract infection. Gram positif cocci were predominant among nosocomial bacteremia (53.8%). Among Gram negative bacteria (enterobacteria) (31.6%), Escherichia coli was the most frequently isolated. SA was methicillin-resistant in 18.3% of community bacteremia and in 26.5% of nosocomial bacteremia. Coagulase negative Staphylococcus were methicillin-resistant in 25.4% of community bacteremia and in 60.1% of nosocomial bacteremia. Measures to prevent catheter blood related infections and urinary tract infections may be started.

[Breast tuberculosis. A case of a diffuse inflammatory form]. / Tuberculose mammaire. A propos d'un cas à forme inflammatoire diffuse.

We report a case of inflammatory tuberculosis of the breast in a 83-year-old French Caucasian woman. She presented with a diffuse inflammatory tuberculosis of the breast and an axillary enlarged lymph node but no tumor was palpable in the breast. A carcinoma was firstly suspected. The diagnosis was accessed after repeat punction of a lymph node, as a Mycobacterium tuberculosis was identified after culture. A medical treatment was sufficient in our case.

Asialo GM1 is a receptor for Pseudomonas aeruginosa adherence to regenerating respiratory epithelial cells.

We investigated the implication of asialo GM1 as an epithelial receptor in the increased Pseudomonas aeruginosa affinity for regenerating respiratory epithelial cells from cystic fibrosis (CF) and non-CF patients. Human respiratory epithelial cells were obtained from nasal polyps of non-CF subjects and of CF patients homozygous for the delta F 508 transmembrane conductance regulator protein (CFTR) mutation and cultured according to the explant-outgrowth model. At the periphery of the outgrowth, regenerating respiratory epithelial cells spreading over the collagen I matrix with lamellipodia were observed, characteristic of respiratory epithelial wound repair after injury. P aeruginosa adherence to regenerating respiratory epithelial cells was found to be significantly greater in the delta F 508 homozygous CF group than in the non-CF group (P < 0.001). In vitro competitive binding inhibition assays performed with rabbit polyclonal antibody against asialo GM1 demonstrated that blocking asialo GM1 reduces P. aeruginosa adherence to regenerating respiratory epithelial cells in delta F 508 homozygous cultures (P < 0.001) as well as in non-CF cultures (P < 0.001). Blocking of asialo GM1 was significantly more efficient in CF patients than in non-CF subjects (P < 0.05). Distribution of asialo GM1 as determined by preembedding labelling and immunoelectron microscopy clearly demonstrated the specific apical membrane expression of asialo GM1 by regenerating respiratory epithelial cells, whereas other cell phenotypes did not apically express asialo GM1. These results demonstrate that (i) asialo GM1 is an apical membrane receptor for P. aeruginosa expressed at the surface of CF and non-CF regenerating respiratory epithelial cells and (ii) asialo GM1 is specifically recovered in regenerating respiratory epithelium. These results suggest that in CF, epithelial repair represents the major event which exposes asialo GM1 for P. aeruginosa adherence.

Pseudomonas aeruginosa selective adherence to and entry into human endothelial cells.

The pathogenesis of Pseudomonas aeruginosa disseminated infections depends on bacterial interaction with blood vessels. We have hypothesized that in order to traverse the endothelial barrier, bacteria would have to adhere to and damage endothelial cells. To test this hypothesis, we studied the adherence to human endothelial cells in primary culture of the piliated P. aeruginosa strain PAK and of two isogenic nonpiliated strains: PAK/p-, which carries a mutation in the pilin structural gene, and PAK-N1, a mutant defective in the regulatory rpoN gene. PAK adhered significantly more than did the pilus-lacking strains. P. aeruginosa was also taken up by endothelial cells, as determined by quantitative bacteriologic assays and by transmission electron microscopy. This internalization of P. aeruginosa seems to be a selective process, since the piliated strain was taken up significantly more than the nonpiliated bacteria and the avirulent Escherichia coli DH5 alpha, even following bacterial centrifugation onto the cell monolayers. A significant fraction of the internalized P. aeruginosa PAK was recovered in a viable form after 6 h of residence within endothelial cells. Progressive endothelial cell damage resulted from PAK intracellular harboring, as indicated by the release of lactate dehydrogenase. An increasing concentration of PAK cells was recovered from the extracellular medium with time, suggesting that ingested bacteria were released from endothelial cells and multiplied freely. We speculate that in vivo the ability of some P. aeruginosa strains to resist intracellular residence would afford protection from host defenses and antibiotics and that the release of viable bacteria into bloodstream may represent a central feature of the pathogenesis of bacteremia in compromised patients.

Cytotoxicity of Pseudomonas aeruginosa internal lectin PA-I to respiratory epithelial cells in primary culture.

Pseudomonas aeruginosa is the most important bacterial pathogen associated with chronic airway infection, especially in cystic fibrosis. We addressed the question of whether the galactophilic internal lectin of P. aeruginosa (PA-I) could represent a virulence factor for the respiratory epithelium. PA-I lectin was localized in all the bacteria of P. aeruginosa ATCC 33347 as determined by immunofluorescence staining. We investigated the dose-dependent effect of P. aeruginosa PA-I lectin on the growth, the ciliary beating frequency, and the morphology of human respiratory cells in primary culture of nasal polyps collected from non-cystic fibrosis patients. PA-I lectin significantly (P < 0.01) inhibited the growth of respiratory cells at a concentration of > or = 10 micrograms/ml. The percentage of active ciliated cell surface of the cultures decreased significantly (P < 0.05) at a PA-I lectin concentration of 50 micrograms/ml. Exposed to a low concentration of PA-I lectin (10 micrograms/ml), respiratory epithelial cells showed intracytoplasmic vacuoles when examined by light and transmission electron microscopy. At a higher concentration of PA-I lectin (100 micrograms/ml), major cell damage and severe epithelial shedding occurred. These results demonstrate that the P. aeruginosa internal PA-I lectin has a dose-dependent cytotoxic effect on respiratory epithelial cells in vitro. The P. aeruginosa PA-I lectin may represent a virulence factor by contributing to the respiratory epithelial damage during P. aeruginosa respiratory infections.

Protection of human respiratory epithelium from Pseudomonas aeruginosa adherence by phosphatidylglycerol liposomes.

The ability of phosphatidylglycerol (DSPG) liposomes to prevent adherence of Pseudomonas aeruginosa to primary cultures of non-cystic fibrosis (CF) and delta F508 homozygous CF human respiratory epithelium was studied. The culture model was characterized by the simultaneous presence of various cellular phenotypes: well-differentiated respiratory epithelial cells, ciliated and nonciliated cells, and migrating cells which can be assimilated into a regenerating epithelium after injury. DSPG liposomes significantly decreased the binding of P. aeruginosa to migrating cells of both non-CF and delta F508 homozygous CF cultures compared with control cultures (35.5 x 10(-3) +/- 8.1 x 10(-3) bacteria per micron 2 versus 23.9 x 10(-3) +/- 2.5 x 10(-3); P < 0.01 for non-CF cultures and 88.8 x 10(-3) +/- 17.2 x 10(-3) bacteria per micron 2 versus 29.1 x 10(-3) +/- 0.6 x 10(-3), P < 0.001 for CF cultures). After treatment with DSPG liposomes, the size of P. aeruginosa aggregates bound to migrating cells in both non-CF cultures and delta F508 homozygous CF cultures was significantly decreased (14.4 +/- 3 bacteria per aggregate versus 11.9 +/- 2.5 bacteria per aggregate [P < 0.05] and 29.9 +/- 8.4 bacteria per aggregate versus 17.3 +/- 2.3 bacteria per aggregate [P < 0.01], respectively). Moreover, the control cultures were characterized by a differential P. aeruginosa adherence according to both the cellular phenotype and the mutation. The migrating cells bound more bacteria than the stationary cells of both non-CF and delta F508 homozygous CF cultures. The CF migrating cells bound significantly more bacteria than the non-CF migrating cells (88.8 x 10(-3) +/- 17.2 x 10(-3) bacteria per microns 2 versus 35.5 x 10(-3) +/- 8.1 x 10(-3) bacteria per micron 2, P < 0.001). These results suggest that DSPG liposomes are able to decrease P. aeruginosa adherence to CF and non-CF respiratory epithelium, particularly to migrating cells, which mimic a regenerating epithelium after injury. DSPG liposomes could also represent a hydrophobic barrier limiting the deleterious action of P. aeruginosa exoproducts.

Cellular and molecular mechanisms of bacterial adhesion to respiratory mucosa.

Different bacterial species adhere avidly to respiratory mucus. Such adhesion, when followed by ciliary clearance, represents an important stage of the airway defense system. However, in pathological conditions, the mucociliary clearance may be severely reduced, and mucus-associated bacteria may multiply and infect the underlying epithelium. Only a few bacteria have been shown to adhere to ciliary membranes of functionally active ciliated cells. Therefore, the first way in which most of the respiratory pathogens associate with the airway epithelium is likely to be by their adhesion to mucus. Some bacteria also secrete products that may affect ciliary function and/or cause cell death and epithelial disruption. Respiratory pathogens that do not bind to normal ciliated cells may readily adhere to injured epithelial cells, or to the unmasked extracellular matrix. Furthermore, following injury, epithelial respiratory cells in the process of migration, in order to repair the wounds, may present receptors to which bacteria adhere. The adhesion to all of these epithelial receptors may contribute to the chronicity of many bacterial respiratory infections.

Evaluation of the efficacy of prophylactic intravenous antibiotherapy with ceftriaxone in post-chemotherapy agranulocytic patients.

A prospective study was carried out in 44 patients treated by intensive chemotherapy inducing a prolonged neutropenia (granulocytes less than 0.5.10(9)/l). All the patients were isolated in protected rooms, received a pathogen-free diet and nonabsorbable oral antibiotics. After double-blind randomization, 22 patients received 2 g of Ceftriaxone (Cef) in a daily infusion beginning on the first day of chemotherapy; and 22 patients received 2 g of placebo (P) under the same conditions. Prophylaxis was continued until the neutropenia resolved (granulocytes greater than 0.5.10(9)/l) or until the onset of infectious symptoms. 19 patients in each group developed febrile episodes, occurring significantly later in the Cef group (16.6 days versus 10.6 days in the P group). No Cef-resistant organism was isolated. Finally, the time at which apyrexia was obtained after the beginning of curative antibiotherapy was the same in both groups. The routine intravenous administration of Cef in combination with nonabsorbable antibiotics is a useful approach in reducing the risk of infection in the neutropenic host.