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The article focuses on the invention of vaccines in the U.S. for immunizing catfish against enteric septicemia and columnaris. After studying the best way to administer them, researchers concluded that these vaccines can be given simultaneously--24 to 48 hours before hatching--during the eyed-egg stage of development. Current practice is to vaccinate newly hatched catfish, about 10 days old, while aboard the trucks that will deliver them to farm ponds for release. It takes workers just 10 to 15 minutes to treat the not-quite-hatched eggs with the two vaccines. And tests have shown that vaccinating catfish at this eyed-egg stage could provide immunity lasting at least 140 days.

Motile Aeromonas septicemia (MAS), caused by virulent Aeromonas hydrophila (vAh), has severely impacted catfish farming in the southeastern United States since 2009. Conditions that trigger the onset of MAS outbreaks remain largely unknown. In this study, the effects of nutrients and select microbes in water on proliferation of vAh and severity of MAS in channel catfish were assessed. Results of the study demonstrated that both nutrient-rich tryptic soy broth powder (TSBp, the microbiological growth medium) and the commercial fish feed supported vigorous growth of vAh in water. By addition of 6 g TSBp or 6 g fish feed to 15 L water (0.04%, w / v), vAh multiplied from 2.5 × 105 CFU/mL to approximately 4.7 × 108 CFU/mL and 2.0 × 108 CFU/mL, respectively, at 24 h post inoculation (hpi). Challenge of fish in the vAh-propagated water at 24 hpi resulted in approximately 96% and 73% mortality, respectively. Co-inoculation of vAh with a vAh-antagonistic Pseudomonas mosselii or a non-antagonistic Aeromonas veronii in water had no significant effects on vAh growth and infection; nevertheless, P. mosselii protected fish against vAh infection (with approximately 79% of relative percentage of survival) when fish were briefly pre-immersed in P. mosselii -propagated water prior to challenge. Culture of vAh in situ described in this study was shown to be a useful method for mimicking vAh growth dynamics in response to nutrients and probiotics in relatively natural environment. Findings of this study would help understand the mechanism of MAS outbreaks and facilitate research on control and prevention of MAS. • Commercial fish feeds supported vigorous proliferation of virulent A. hydrophila (vAh). • A method of culture of vAh in situ was developed for fish challenge. • A vAh-antagonistic isolate of Pseudomonas mosselii protected fish against vAh infection. [ABSTRACT FROM AUTHOR]

A polyphasic characterization of atypical isolates of Yersinia ruckeri (causative agent of enteric redmouth disease in trout) obtained from hatchery-reared brown trout Salmo trutta in South Carolina was performed. The Y. ruckeri isolates were biochemically and genetically distinct from reference cultures, including the type strain, but were unequivocally ascribed to the species Y. ruckeri, based on API 20E, VITEK, fatty acid methyl ester profiles, and 16S rRNA gene sequencing analysis. These isolates were nonmotile and unable to hydrolyze Tween 20/80 and were therefore classified as Y. ruckeri biotype 2. Genetic fingerprint typing of the isolates via enterobacterial repetitive intergenic consensus (amplified by polymerase chain reaction) and fragment length polymorphism showed biotype 2 as a homogeneous group distinguishable from other Y. ruckeri isolates. This is the first report of Y. ruckeri biotype 2 in the USA.