Comparison of Vietnamese and US isolates of Edwardsiella ictaluri

Abstract

We compared Edwardsiella ictaluri from striped catfish in Vietnam with US channel catfish isolates. Biochemical analyses and sequencing of the 16S rRNA gene confirmed that the Vietnamese isolates were E. ictaluri. Comparison using rep-PCR fingerprinting demonstrated no significant differences between the isolates, but plasmid analysis indicated that the Vietnamese isolates grouped into 4 plasmid profiles, each different from the typical pEI1 and pEI2 plasmid profile found in the US isolates. Sequencing plasmids representative of the 4 profiles indicated that all contained derivatives of the E. ictaluri plasmid pEI1, whereas only 1 contained a plasmid derivative of the E. ictaluri plasmid pEI2. The pEI2 encoded type III secretion effector, EseI, and its chaperone, EscD, were found to be present on the chromosome in isolates lacking a pEI2 derivative. In addition, 1 isolate carried a 5023 bp plasmid that does not have homology to either pEI1 or pEI2. Furthermore, Vietnamese isolates were PCR positive for the type III and type VI secretion system genes esrC and evpC, respectively, and the urease enzyme, but were PCR-negative for the putative type IV secretion system gene virD4. A monoclonal antibody against the lipopolysaccharide of E. ictaluri ATCC 33202 did not react with the Asian isolates or with the more recent US isolates. Antibiotic resistance patterns were variable and did not correlate to the presence of any particular plasmid profile. Finally, the Vietnamese isolates were avirulent and had a significantly reduced capacity for intracellular replication within head-kidney-derived channel catfish macrophages.

Concurrent infections of Flavobacterium columnare and Edwardsiella ictaluri in striped catfish, Pangasianodon hypophthalmus in Thailand

“…Sharing the same diseased pattern with channel catfish (I. punctatus) in the United States, E. ictaluri and F. columnare have been reported as the most highly pathogenic bacteria threatening the cultured striped catfish industry in Vietnam (Crumlish et al, 2002;Ferguson et al, 2001;Tien et al, 2012). Recent reports, however, have indicated that the genetic characterization and pathogenicity of E. ictaluri were different between Vietnamese and US isolates (Bartie et al, 2012;Rogge et al, 2013), where E. ictaluri catfish isolates from Vietnam were nonpathogenic to the US channel catfish (Rogge et al, 2013). The differences in clinical signs and histopathological manifestations caused by E. ictaluri in two different hosts may explain the inconsistency in originally described names as enteric septicemia of catfish (ESC) in US channel catfish and "bacillary necrosis in Pangasius" in Vietnamese striped catfish (Crumlish et al, 2002;Ferguson et al, 2001;Hawke et al, 1981).…”

Antimicrobial Usage and Antimicrobial Resistance in Animal Production in Southeast Asia: A Review

“…[21,77,78,79,80,81,82,83]. These publications included research related to fish (6) and shrimp farms (2).…”

“…These publications included research related to fish (6) and shrimp farms (2). All publications came from Thailand and Vietnam, even though four investigated aquaculture samples originating from several SEA countries (Thailand, Vietnam, Malaysia, and Indonesia) [78,79,80,82]. One study investigated AMR in isolates from imported aquaculture products from Thailand.…”

Oral Vaccination of Channel Catfish against Enteric Septicemia of Catfish Using a Live Attenuated Edwardsiella ictaluri Isolate

“…Another factor potentially affecting vaccine efficacy is antigenic variability among virulent isolates. Although E. ictaluri is for the most part considered a serologically homogenous species (Plumb and Vinitnantharat 1989;Bertolini et al 1990;Lobb et al 1993), recent evidence suggests isolates recovered from different host species and different geographical regions have variable genetic and antigenic profiles (Soto et al 2012;Hawke et al 2013;Rogge et al 2013). In addition, during cross-challenge studies, Channel Catfish immunized using a panel of E. ictaluri isolates did not exhibit uniform protection against all heterologous isolates used in the study .…”