Vibrio fluvialis in Patients with Diarrhea, Kolkata, India

Goutam Chowdhury, Gururaja P. Pazhani, Devarati Dutta, Sucharita Guin, Sanjucta Dutta, Santanu Ghosh, Hidemasa Izumiya, Masahiro Asakura, Shinji Yamasaki, Yoshifumi Takeda, Eiji Arakawa, Haruo Watanabe, Asish K. Mukhopadhyay, Mihir K. Bhattacharya, K. Rajendran, Gopinath Balakrish Nair, and Thandavarayan Ramamurthy

Author affiliations: National Institute of Cholera and Enteric Diseases, Kolkata, India (G. Chowdhury, G.P. Pazhani, D. Dutta, S. Guin, S. Dutta, S. Ghosh, A.K. Mukhopadhyay, M.K. Bhattacharya, K. Rajendran, G. Nair, T. Ramamurthy); National Institute of Infectious Diseases, Tokyo, Japan (H. Izumiya, E. Arakawa, H. Watanabe); Osaka Prefecture University Graduate School of Life and Environmental Sciences, Osaka, Japan (M. Asakura, S. Yamasaki); and National Institute of Cholera and Enteric Diseases Collaborative Research Center of Okayama University for Infectious Diseases in India, Kolkata (Y. Takeda).

Abstract

We identified 131 strains of Vibrio fluvialis among 400 nonagglutinating Vibrio spp. isolated from patients with diarrhea in Kolkata, India. For 43 patients, V. fluvialis was the sole pathogen identified. Most strains harbored genes encoding hemolysin and metalloprotease; this finding may contribute to understanding of the pathogenicity of V. fluvialis.

Many members of the family Vibrionaceae cause diarrheal disease; among these, Vibrio cholerae O1/O139 and V. parahaemolyticus are responsible for several epidemics and pandemics (1,2). In Indonesia, >20% of diarrheal infections are caused by pathogenic Vibrio spp (3). Some of these Vibrio spp. can grow in thiosulfate–citrate–bile salts–sucrose agar as yellow colonies and do not agglutinate with V. cholerae O1 antiserum. These species are broadly defined as nonagglutinating (NAG) vibrios.
The emerging etiologic agent V. fluvialis has caused sporadic cases and outbreaks of diarrhea in several countries (4–6). Species-specific minimal biochemical tests, e.g., lysine decarboxylase, ornithine decarboxylase, arginine didydrolase, and L-arabinose, are used to identify V. fluvialis; without these tests, it may be confused with NAG vibrios, V. cholerae, and even Aeromonas spp. In most resource-poor countries, these tests are not performed, which may lead to labeling of V. fluvialis as a NAG vibrio.
Although V. fluvialis is known to cause diarrhea, the mechanisms involved in its pathogenicity are not well established. To evaluate the prevalence of V. fluvialis in India and possible mischaracterization as an NAG vibrio, we examined cases in which isolates from hospitalized patients with diarrhea were identified as NAG vibrios and characterized the strains using phenotypic and genetic methods.