Penaeus vannamei, white feces syndrome, Vibrio cholerae, pathogenicity, antibiotic susceptibility

Whiteleg shrimp Penaeus vannamei is an important commercial shrimp species cultivated in China and many other countries worldwide. Bacteriosis is a major economic problem that inhibits the farming of this species in fresh water. White feces syndrome is an emerging epidemic in freshwater cultured P. vannamei and has caused significant economic damage. Only scarce information is available on Vibrio cholerae as a possible causal agent for this disease. In this study, a virulent strain BB31 was isolated from diseased P. vannamei suffering from white feces syndrome, and identified as a V. cholerae isolate through phylogenetic analysis and phenotypic characteristics. A phylogenetic tree was constructed to examine the relationship of isolate BB31 to other V. cholerae isolates. Three genes encoding hemolysin, outer membrane protein, and cholera toxin transcriptional activator were present in the BB31 isolate confirming its potential pathogenicity. In addition, isolate BB31 is known to have developed resistance to penicillin, sulfonamides and cephalosporin antibiotics. This was demonstrated when screened against a range of common antibiotics for aquaculture and veterinary use. To the best of our knowledge, this is the first report of white feces syndrome caused by V. cholerae in freshwater farmed P. vannamei.