title: Edwardsiella ictaluri as the causative agent of mortality in cultured Nile tilapia.
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 naive tilapia, reproducing clinical signs and mortality, thereby establishing Koch's postulates.
authors: Department of Pathobiology, School of Veterinary Medicine, Ross University, Basseterre, St. Kitts, West Indies. esoto@rossvet.edu.kn
authors: Esteban
authors: E
authors: Soto
authors: Matt
authors: M
authors: Griffin
authors: Maziel
authors: M
authors: Arauz
authors: Andres
authors: A
authors: Riofrio
authors: Alexis
authors: A
authors: Martinez
authors: Maria Eugenia
authors: ME
authors: Cabrejos
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017756:Aquaculture; D023681:Cichlids; D004196:Disease Outbreaks / Q000662:veterinary; D024881:Drug Resistance, Bacterial; D020610:Edwardsiella ictaluri / Q000187:drug effects / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000453:epidemiology / Q000382:microbiology / Q000401:mortality / Q000662:veterinary*; D005393:Fish Diseases / Q000453:epidemiology / Q000382:microbiology* / Q000401:mortality / Q000473:pathology; D010802:Phylogeny
chemical_list: D000900:Anti-Bacterial Agents