Detection of piluslike structures on clinical and environmental isolates of Vibrio vulnificus

Twenty clinical isolates of Vibrio vulnificus were compared with 10 environmental strains by using electron microscopy and agglutination assays with human erythrocytes, guinea pig erythrocytes, and Saccharomyces cerevisiae. In addition, the isolates were tested for ability to adhere to the human epithelial cell lines HEp-2 and A549. When examined by electron microscopy, 16 (80%) of the 20 clinical isolates demonstrated the presence of piluslike structures; the composition of the bacterial populations ranged from 0 to 68% piliated cells. In contrast, only 3 (30%) of the 10 environmental isolates were piliated, with a range from 0 to 16% piliated cells. A significant association between the presence of piliated cells and the isolate source was found (P less than 0.05). None of the 30 strains agglutinated erythrocytes or yeast cells. V. vulnificus adherence results obtained with HEp-2 cells showed 10 (50%) of 20 clinical isolates and 0 (0%) of 10 environmental isolates with averages of greater than 10 adherent bacteria per cell, demonstrating a correlation between attachment and the isolate source (P less than 0.05). Selected strains were tested to determine whether methyl alpha-D-mannopyranoside, fructose, or alpha-L-(-)-fucose would inhibit bacterial adherence to HEp-2 cells. Multiple patterns of adherence inhibition were observed. Adherence to A549 cells showed 8 (40%) of 20 clinical isolates and 0 (0%) of 10 environmental strains with averages of greater than 10 adherent bacteria per cell. A statistical association between attachment and the isolate source was demonstrated (P less than 0.05). These data suggest that the presence of piluslike structures and the ability to adhere to human epithelial cell lines may be more closely associated with V. vulnificus isolates from clinical specimens than with environmental strains.