A comparison of three methods for assaying hydrophobicity of pathogenic vibrios

The surface hydrophobicity of strains of Vibrio alginolyticus, V. carchariae, V. damsela, V. harveyi and V. vulnificus , isolated from either diseased cultured grouper ( Epinephelus malabaricus ) or penaeids ( Penaeus monodon and P. japonicus ) was determined using three different methods:the salt aggregation test (SAT), bacterial adhesion to hydrocarbons test (BATH), and adherence to nitrocellulose filters test (NCF). The results obtained indicate that all the strains tested showed some degree of hydrophobicity with the type strain of V. harveyi (ATCC 25919) showing strong hydrophobic properties in all the methods. The SAT method used in the present study was modified to a microtitre tray test, an easier test to read than the conventional in glass slide methodology. All the 13 test strains were positive in the BATH test when n -octane was used as the solvent, but only one strain was positive when n -hexadecane was used as the solvent. It is suggested that this method using n -octane as solvent is suitable for assaying the hydrophobicity of pathogenic vibrios isolated from diseased aquatic animals.