title: Molecular identification and virulence of three Aeromonas hydrophila isolates cultured from infected channel catfish during a disease outbreak in west Alabama (USA) in 2009.
abstract: Three isolates (AL09-71, AL09-72, and AL09-73) of Aeromonas hydrophila were cultured from infected channel catfish Ictalurus punctatus during a disease outbreak in west Alabama, USA, in August 2009. Sequence analysis of the 16S-23S rDNA intergenic spacer region (ISR), cpn60, gyrB, and rpoD genes of the 3 strains revealed that the 3 strains were closely related to each other, sharing 97 to 99% nucleotide sequence similarities. However, ISR sequences of the 3 isolates from 2009 shared only 64% nucleotide sequences with AL98-C1B, a 1998 isolate of A. hydrophila cultured from diseased fish in Alabama. Sequences of cpn60, gyrB, and rpoD from the 3 isolates from 2009 shared 91 to 95% homologies with AL98-C1B. Based on both LD50 and LD95 values of intraperitoneal injection assays, the virulences of the 3 isolates from 2009 were not significantly different from each other, but were at least 200-fold more virulent than AL98-C1B, indicating that the 3 west Alabama isolates of A. hydrophila from 2009 were highly virulent to channel catfish.
authors.affiliation: Aquatic Animal Health Research Unit, USDA-ARS, 990 Wire Road, Auburn, Alabama 36832, USA. julia.pridgeon@ars.usda.gov
authors.forename: Julia W
authors.initials: JW
authors.lastname: Pridgeon
authors.forename: Phillip H
authors.initials: PH
authors.lastname: Klesius
mesh_terms: D016980:Aeromonas hydrophila / Q000235:genetics* / Q000472:pathogenicity*; D000407:Alabama / Q000453:epidemiology; D000818:Animals; D004196:Disease Outbreaks / Q000662:veterinary*; D005393:Fish Diseases / Q000453:epidemiology / Q000382:microbiology*; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D007059:Ictaluridae; D014774:Virulence