Aquaculture 2022

February 28 - March 4, 2022

San Diego, California

PHENOTYPIC CHARACTERIZATION OF Edwardsiella piscicida ISOLATES FROM CATFISH AQUACULTURE

Ashmita Poudel* , Lester Khoo, Mark Lawrence,  Ganesh Kumar,  John Hawke,  Larry Dorman,  Grace Ramena, and Suja Aarattuthodi

Thad Cochran National Warmwater Aquaculture Center

Mississippi State University

127 Experiment Station Road

Stoneville, Mississippi-38776, U.S.A

ap2751@msstate.edu

 



 Catfish  industry  is the largest aquaculture sector in the U. S. contributi ng 74% of the total finfish production. Hybrid catfish (? channel catfish (Ictalurus punctatus) × ? blue catfish (I. furcatus))  is preferred in intensive production systems due to  its superior production traits.  Edwardsiellosis caused by the gram- negative bacteria, Edwardsiella piscicida is  a major threat  to catfish culture  causing significant production losses (Figure 1) .  Food-sized hybrid catfish are  reported to be  more vulnerable to E. piscicida evidenced by the case submissions to the diagnostic laboratories.  Fish loss at this stage caus es signific ant economic burden as most of the production costs  would have been incurred.  Although the archived E. piscicida isolates (2013-2018) have been categorized into five genetic clades, these are not phenotypically profiled. Phenotypic characterization of these genetically  and temporally  distinct E. piscicida isolates will  provide relevant insights on their adaptations to changing environments and resources . This study analyzed the growth characteristics of representative  E. piscicida isolates at different  incubation temperatures. In addition, the salt tolerance, nutrient preferences, motility, and aerotolerance of these isolates were evaluated . Growth of the bacterial strains was significantly low at 12ºC and 45ºC when compared to other tested temperatures. Trypticase soy agar (TSA) and Mueller-Hinton agar with 5% blood supplementation significantly augmented bacterial growth (Figure 2) compared to Salmonella-Shigella and MacConkey agar . Growth of E. piscicida isolates were significantly inhibited in media with >3% salt levels. The studied bacterial strains revealed a facultative anaerobic growth pattern in thioglycol late broth.  No significant phenotypic variations among the studied isolates representing different genotypes were observed. Further studies of bacterial isolates (temporally and spatially distributed) covering a much wider geographical area and host species will provide pertinent information on these deleterious pathogens. A comprehensive phenotypic characterization will be  beneficial  during disease diagnosis and to develop efficient management strategies against these bacteria.