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Edwardsiella ictaluri as the Causative Agent of Mortality in Cultured Nile Tilapia
Author(s) -
Soto Esteban,
Griffin Matt,
Arauz Maziel,
Riofrio Andres,
Martinez Alexis,
Cabrejos Maria Eugenia
Publication year - 2012
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1080/08997659.2012.675931
Subject(s) - edwardsiella ictaluri , nile tilapia , catfish , biology , oreochromis , 16s ribosomal rna , microbiology and biotechnology , outbreak , tilapia , polymerase chain reaction , infectivity , bacteria , gene , veterinary medicine , virology , ictalurus , fishery , genetics , fish <actinopterygii> , medicine , virus
Abstract Edwardsiella ictaluri was consistently isolated from the spleens, livers, and head kidneys of diseased Nile tilapia Oreochromis niloticus from a farm experiencing mortality events in several culture ponds. We describe the first published outbreak of E. ictaluri –induced edwardsiellosis in Nile tilapia. Pure cultures of the isolated bacteria were characterized both biochemically and molecularly. Biochemical analysis was performed using the API‐20E and RapID One systems, and antimicrobial susceptibility was determined by the broth microdilution method. Molecular analysis involved sequencing of the 16S rRNA gene, species‐specific real‐time polymerase chain reaction (PCR), and PCR‐mediated genomic fingerprinting (rep‐PCR). Pairwise sequence analysis of the 16S rRNA gene identified the case isolates to be a 100% match to E. ictaluri cultured from channel catfish in the southeastern United States. However, rep‐PCR analysis identified the case isolates to be genetically different from representative strains isolated from disease outbreaks in cultured channel catfish in Mississippi. Infectivity challenges (intraperitoneal injection and immersion) demonstrated that a representative E. ictaluri strain isolated from tilapia was pathogenic to naïve tilapia, reproducing clinical signs and mortality, thereby establishing Koch's postulates. Received August 30, 2011; accepted January 30, 2012