Description of Providencia vermicola isolated from diseased Indian major carp, Labeo rohita (Hamilton, 1822)

• Identification of Providencia vermicola in Labeo rohita
• First report in fish from India, 16S rRNA bases submitted in GenBank, KF155518.1

A strain of Gram-negative, urease-positive, motile, Providencia bacteria, with colony size of 1.8–2.2 mm was isolated from trypticase soy agar (TSA)-medium, originally isolated from diseased Indian major carp, Labeo rohita (rohu) during the survey period from August, 2012 to July, 2013 at a commercial fish farm in Nerinjipettai-village, near Mettur Dam, Tamil Nadu, India. The diseased rohu showed ulcerative lesions on the abdomen surface and bases of the pelvic fin with reddish coloration. The present study investigated the species through biochemical reaction and PCR amplification of 16S rRNA locus. Experimental infection assays with reproduced isolate was conducted and pathogenicity (by immersion, intramuscular and oral route) was demonstrated in healthy rohu fish. Histopathological analyses of the pathogen exposed gill, liver and skin showed moderate structural variations. Since no Providencia was detected in fish feedstuffs and pond water as the source of this pathogen remains unknown, our study revealed that the Providencia-infection may be due to the handling methods and from the poultry feces aside from the human feces from nearby ponds. Hence, Providencia isolate is regarded as an opportunistic pathogen for rohu. This is the first report of Providencia which can cause disease in cultured fish, L. rohita.