Virulence determination of bacterial isolates through culture in India ink including broth

Virulency is the degree of pathogenicity exhibited by most of the pathogens and it is a measure that effectively differentiates pathogenic and non-pathogenic strains. In the present study, culture of bacteria for 10 to 12 h (overnight) at 37°C in 10% India ink included broth that can be used as marker test for initial virulence identification while screening a number of bacterial isolates. These results were further confirmed by the in vivo virulence tests. Although, this is the first report, there is no clear explanation to the degradation of India ink by virulent bacteria which was obtained but this could act as a marker for initial screening of isolates for their virulence. Moreover, India ink is used as a suitable capsular stain and capsule act as a virulence factor for most of the bacteria. So virulence test by 10% India ink including broth acts as a simple, low cost and easy method for initial screening of virulent from non virulent strains.   Key words: Aeromonas hydrophila, bacteria, India ink, pathogens, virulence