Low metabolic activity of biofilm formed by Enterococcus faecalis isolated from healthy humans and wild mallards (Anas platyrhynchos)

It is widely known that Enterococcus faecalis virulence is related to its biofilm formation. Although Enterococci are common commensal organisms of the gastrointestinal tract, the difference between commensal and pathogen strains remain unclear. In this study, we compare the biochemical profile of the biofilms formed by two groups of medical and two groups of commensal strains. The medical strains were isolated as pathogens from infections of urinary tract and other infections (wounds, pus and bedsores), and the commensal strains were taken from faeces of healthy volunteers and faeces of wild mallards (Anas platyrhynchos) living in an urban environment. The properties of biofilms formed by medical and commensal strains differed significantly. Commensal strains showed lower metabolic activity and glucose uptake and higher biofilm biomass than the medical ones. Consistent with glucose uptake experiments, we found that the glucose dehydrogenase gene was more expressed in medical strains. These results indicate that higher metabolic activity and lower protein concentration of E. faecalis cells within biofilms are formed during infections.This work was supported by the Medical University of Gdansk research grant (GUMed W-65) and was financed partly by University of Gdansk research grant (BW 1440-5-0099-7). We are grateful to Katarzyna Zolkos for her help in catching mallards and Magdalena Remisiewicz for correcting the English. Catarina Seabra helped in preparing assays

Cytotoxic activity of clinical Stenotrophomonas maltophilia

Aims: To determine the potential virulence factors produced by culture supernatants of clinical isolates of Stenotrophomonas maltophilia. Methods and Results: Culture supernatants of clinical isolates of S. maltophilia were assayed for haemolytic, enzymatic (lipase, protease and phospholipase) and cytotoxic activity. Cytotoxic activity was assayed in Vero (African green monkey), HeLa (human cervix) and HEp-2 (human larynx epidermoid carcinoma) cells. Microscopic analyses revealed intensive rounding, loss of intercellular junctions and membrane alterations (blebbing) followed by death of HEp-2 cells. In Vero and HeLa cells, the cytotoxic effects were characterized by vigorous endocytosis and cell aggregation. The viability of cultured mammalian cells was determined with neutral red and demonstrated that the sensitivity among the cells was different. This activity was inactivated by heating at 56 degrees C for 15 min and protease inhibitors did not inhibit cytotoxic activity. The clinical S. maltophilia presented a cell-free haemolytic activity similar to the 'hot-cold' haemolysins. Conclusions: S. maltophilia culture supernatants caused vigorous endocytosis and cell aggregation in HeLa and Vero cells, produced haemolytic and enzymatic activities. Significance and Impact of the Study: This work revealed the presence of putative virulence factors that could be associated with human infections involving Stenotrophomonas maltophilia strains.43444344