Abstract
Enteric septicemia of catfish, columnaris disease and streptococcosis, caused by Edwardsiella ictaluri, Flavobacterium columnare and Streptococcus iniae, respectively, are the most common bacterial diseases of economic significance to the pond-raised channel catfish Ictalurus punctatus industry. Certain management practices are used by catfish farmers to prevent large financial losses from these diseases such as the use of commercial antibiotics. In order to discover environmentally benign alternatives, using a rapid bioassay, we evaluated a crude extract from the roots of muscadine Vitis rotundifolia against these fish pathogenic bacteria and determined that the extract was most active against F. columnare. Subsequently, several isolated compounds from the root extract were isolated. Among these isolated compounds, (+)-hopeaphenol (2) and (+)-vitisin A (3) were found to be the most active (bacteriostatic activity only) against F. columnare, with 24-h 50% inhibition concentrations of 4.0 ± 0.7 and 7.7 ± 0.6 mg/L, respectively, and minimum inhibitory concentrations of 9.1 ± 0 mg/L for each compound which were approximately 25X less active than the drug control florfenicol. Efficacy testing of 2 and 3 is necessary to further evaluate the potential for these compounds to be used as antibacterial agents for managing columnaris disease.
Highlights
Two common diseases of channel catfish Ictalurus punctatus grown in ponds in the southeastern part of the United States of America (USA) are columnaris disease and enteric septicemia of catfish (ESC) [1,2]
Columnare based on the minimum inhibitory concentration (MIC) results (100.0 mg/L and 10.0 mg/L, respectively), the bioassay was not repeated for this test bacterial species
F. columnare (60.8 mg/L and 100.0 mg/L, respectively) did not indicate strong activity compared to florfenicol, these results are typical for extracts that are compared to isolated pure active compounds because the active compounds are expected to be at lower concentrations in the initial crude extract
Summary
Two common diseases of channel catfish Ictalurus punctatus grown in ponds in the southeastern part of the United States of America (USA) are columnaris disease and enteric septicemia of catfish (ESC) [1,2]. Molecules 2018, 23, 2761 the backs of infected fish, with small ulcers and/or depigmented lesions Both diseases have high mortality rates and cost catfish producers millions of U.S dollars annually [2]. Another common problem in fish species is the bacterial disease Streptococcosis. The Gram-positive bacterium Streptococcus iniae is attributed as the cause of streptococcosis, which can result in very high mortality rates in freshwater fish. The potential treatments for columnaris disease with other inorganic agents such as potassium permanganate and copper sulfate pentahydrate have been cited [6] The disadvantages of these therapeutants are their broad-spectrum toxicity towards non-target organisms (such as channel catfish) [7]. Columnare, E. ictaluri and S. iniae, we evaluated crude extract and natural compounds from the roots of muscadine (Vitis rotundifolia Michx., family Vitaceae) using a rapid bioassay
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