334
Diagnosis
Examination of gyrB sequences revealed a >99.6 % homology between US isolates
and the type strain leading to the development of a PCR to differentiate two genotypic groups, i.e. Edw. piscicida and Edw. piscicida -like organisms (Griffi n et al.
2014 ). Individual RT-PCRs were developed to detect Edw. tarda, Edw. piscicida and
Edw. piscicida -like organisms in channel catfi sh leading to sensitive (5 copies of the
DNA in a 15 μl reaction; 10
2 to 10
3 CFU in ~25 g amounts of kidney tissue, 35 ml
of pond water, or 20 l of broth culture), specifi c and reproducible assays (Reichley
et al. 2015 ).
Pathogenicity
Pathogenicity experiments utilized i.m. injection of 3 μl of suspensions containing
10
6 CFU/ml of the cultures into zebra fi sh with 11.1-100 % mortalities recorded
after 7-days (Abayneh et al. 2012 ).
Edwardsiella tarda (= Paracolobactrum anguillimortiferum,
Edw.an nguillimortifera)
Characteristics of the Disease
Edw. tarda has emerged with some frequency in the Far East, particularly Japan,
Taiwan (Wakabayashi and Egusa 1973 ; Miyazaki and Egusa 1976 ; Kou 1981 ) and
China (Xu and Zhang 2014 ; Qin et al. 2014 ; Mo et al. 2015 ). The history of
edwardsiellosis, as the disease is called, may be traced to two separate parallel
developments, i.e. those of Wakabayashi and Egusa ( 1973 ) in Japan, and Meyer
and Bullock ( 1973 ) in the USA. The situation is further complicated by an earlier
report of Hoshina ( 1962 ), who described Paracolobactrum anguillimortiferum as a
pathogen of pond-cultured eels. This organism is probably synonymous with Edw.
tarda.
Excellent descriptions of the clinical manifestation of Edw. tarda infections in
channel catfi sh were published by Meyer and Bullock ( 1973 ). These authors
reported that with mild infections, the only external signs of disease are the presence
of small cutaneous lesions of approximately 3–5 mm in diameter, which are located
in the postero-lateral region of the body. With progression of the disease, abscesses
develop in the muscle of the body and tail. These abscesses may enlarge, and
develop into gas-fi lled hollow areas. From the surface, these are seen as poorly
pigmented, convex swollen areas which, if punctured, emit a foul odour. This condition has given rise to the name emphysematous putrefactive disease of catfi sh.
6 Enterobacteriaceae Representatives
Diagnosis
Examination of gyrB sequences revealed a >99.6 % homology between US isolates
and the type strain leading to the development of a PCR to differentiate two genotypic groups, i.e. Edw. piscicida and Edw. piscicida -like organisms (Griffi n et al.
2014 ). Individual RT-PCRs were developed to detect Edw. tarda, Edw. piscicida and
Edw. piscicida -like organisms in channel catfi sh leading to sensitive (5 copies of the
DNA in a 15 μl reaction; 10
2 to 10
3 CFU in ~25 g amounts of kidney tissue, 35 ml
of pond water, or 20 l of broth culture), specifi c and reproducible assays (Reichley
et al. 2015 ).
Pathogenicity
Pathogenicity experiments utilized i.m. injection of 3 μl of suspensions containing
10
6 CFU/ml of the cultures into zebra fi sh with 11.1-100 % mortalities recorded
after 7-days (Abayneh et al. 2012 ).
Edwardsiella tarda (= Paracolobactrum anguillimortiferum,
Edw.an nguillimortifera)
Characteristics of the Disease
Edw. tarda has emerged with some frequency in the Far East, particularly Japan,
Taiwan (Wakabayashi and Egusa 1973 ; Miyazaki and Egusa 1976 ; Kou 1981 ) and
China (Xu and Zhang 2014 ; Qin et al. 2014 ; Mo et al. 2015 ). The history of
edwardsiellosis, as the disease is called, may be traced to two separate parallel
developments, i.e. those of Wakabayashi and Egusa ( 1973 ) in Japan, and Meyer
and Bullock ( 1973 ) in the USA. The situation is further complicated by an earlier
report of Hoshina ( 1962 ), who described Paracolobactrum anguillimortiferum as a
pathogen of pond-cultured eels. This organism is probably synonymous with Edw.
tarda.
Excellent descriptions of the clinical manifestation of Edw. tarda infections in
channel catfi sh were published by Meyer and Bullock ( 1973 ). These authors
reported that with mild infections, the only external signs of disease are the presence
of small cutaneous lesions of approximately 3–5 mm in diameter, which are located
in the postero-lateral region of the body. With progression of the disease, abscesses
develop in the muscle of the body and tail. These abscesses may enlarge, and
develop into gas-fi lled hollow areas. From the surface, these are seen as poorly
pigmented, convex swollen areas which, if punctured, emit a foul odour. This condition has given rise to the name emphysematous putrefactive disease of catfi sh.
6 Enterobacteriaceae Representatives