AUTHOR=Akgul Ali , Nho Seong Won , Kalindamar Safak , Tekedar Hasan C. , Abdalhamed Hossam , Lawrence Mark L. , Karsi Attila 

TITLE=Universal Stress Proteins Contribute Edwardsiella ictaluri Virulence in Catfish

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.02931

DOI=10.3389/fmicb.2018.02931

ISSN=1664-302X

ABSTRACT=<p><italic>Edwardsiella ictaluri</italic> is an intracellular Gram-negative facultative pathogen causing enteric septicemia of catfish (ESC), a common disease resulting in substantial economic losses in the U.S. catfish industry. Previously, we demonstrated that several universal stress proteins (USPs) are highly expressed under <italic>in vitro</italic> and <italic>in vivo</italic> stress conditions, indicating their importance for <italic>E. ictaluri</italic> survival. However, the roles of these USPs in <italic>E. ictaluri</italic> virulence is not known yet. In this work, 10 <italic>usp</italic> genes of <italic>E. ictaluri</italic> were in-frame deleted and characterized <italic>in vitro</italic> and <italic>in vivo</italic>. Results show that all USP mutants were sensitive to acidic condition (pH 5.5), and <italic>Ei</italic>Δ<italic>usp05</italic> and <italic>Ei</italic>Δ<italic>usp08</italic> were very sensitive to oxidative stress (0.1% H<sub>2</sub>O<sub>2</sub>). Virulence studies indicated that <italic>Ei</italic>Δ<italic>usp05</italic>, <italic>Ei</italic>Δ<italic>usp07</italic>, <italic>Ei</italic>Δ<italic>usp08</italic>, <italic>Ei</italic>Δ<italic>usp09</italic>, <italic>Ei</italic>Δ<italic>usp10</italic>, and <italic>Ei</italic>Δ<italic>usp13</italic> were attenuated significantly compared to <italic>E. ictaluri</italic> wild-type (<italic>Ei</italic>WT; 20, 45, 20, 20, 55, and 10% vs. 74.1% mortality, respectively). Efficacy experiments showed that vaccination of catfish fingerlings with <italic>Ei</italic>Δ<italic>usp05</italic>, <italic>Ei</italic>Δ<italic>usp07</italic>, <italic>Ei</italic>Δ<italic>usp08</italic>, <italic>Ei</italic>Δ<italic>usp09</italic>, <italic>Ei</italic>Δ<italic>usp10</italic>, and <italic>Ei</italic>Δ<italic>usp13</italic> provided complete protection against <italic>Ei</italic>WT compared to sham-vaccinated fish (0% vs. 58.33% mortality). Our results support that USPs contribute <italic>E. ictaluri</italic> virulence in catfish.</p>