Pathogenic potential of Aeromonas hydrophila isolated from surface waters in Kolkata, India

1 Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India 2 National Institute of Cholera and Enteric Diseases, P-33 C.I.T. Road, Scheme-XM, Beliaghata, Kolkata 700 010, India Correspondence Prasanta K. Bag pkbbioc{at}caluniv.ac.in Received July 14, 2009 Accepted August 24, 2009 Members of the genus Aeromonas (family Aeromonadaceae ) are medically important, Gram-negative, rod-shaped micro-organisms and are ubiquitous in aquatic environments. Aeromonas species are increasingly recognized as enteric pathogens; they possess several virulence factors associated with human disease, and represent a serious public health concern. In the present study, putative virulence traits of Aeromonas hydrophila isolates collected from different natural surface waters of Kolkata, India, were compared with a group of clinical isolates from the same geographical area using tissue culture and PCR assays. Enteropathogenic potential was investigated in the mouse model. Of the 21 environmental isolates tested, the majority showed cytotoxicity to HeLa cells (81 %), haemolysin production (71 %) and serum resistance properties (90 %), and they all exhibited multi-drug resistance. Some of the isolates induced fluid accumulation (FA ratio 100), damage to the gut and an inflammatory reaction in the mouse intestine; these effects were comparable to those of clinical strains of A. hydrophila and toxigenic Vibrio cholerae . Interestingly, two of the isolates evoked a cell vacuolation effect in HeLa cells, and were also able to induce FA. These findings demonstrate the presence of potentially pathogenic and multi-drug-resistant A. hydrophila in the surface waters, thereby indicating a significant risk to public health. Continuous monitoring of surface waters is important to identify potential water-borne pathogens and to reduce the health risk caused by the genus Aeromonas . Part of this work (Abstract) has been presented at the US–Japan Cooperative Medical Science Program (CMSP) 13th International Conference on Emerging Infectious Diseases in the Pacific Rim (Kolkata, India, 6–9 April 2009). Tables of PCR primers used in this study, and of correlation of variable biochemical characteristics with cytotoxin production and adherence for environmental isolates are available with the online version of this paper.