Induction of Hemagglutinating Activity of Edwardsiella tarda by Sodium Chloride

Abstract

ABSTRACT-The hemagglutinating activity (HA) of Edwardsiella tarda, which had been isolated from cultured fish and culture environments, was investigated in relation to NaCl concentration of the growth medium. E. tarda cells were cultured in a peptone-yeast extract broth supplemented with 3% NaCl (3%-NaCl culture) and without NaCl (0%-NaCl culture). Hemagglutination assays with guinea pig erythrocytes classified the strains into three HA patterns. Seventeen strains exhibited HA only with the 3%-NaCl culture (type A). A more frequent type (35 strains) displayed HA in both 0%-and 3%-NaCl cultures but the 3%-NaCl culture showed higher HA activity than the 0%-NaCl culture (type B). No HA was detected in both cultures of the other three strains (type C). The NaCl-induced HA was well correlated with the expression of a 19.3 kDa protein, a fimbrial major subunit (FimA). Infection experiments with a selected strain (type A) of E. tarda revealed that the 3%-NaCl culture was more virulent to Japanese flounder Paralichthys olivaceus than the 0%-NaCl culture, when fish were challenged by an oral route. This induction of the fimbrial protein under higher NaCl concentration may play an important role in the virulence of E. tarda in marine environments.

Sodium chloride-enhanced adherence of Edwardsiella tarda to HEp-2 cells

“…In the present study, we demonstrated that the adhesive patterns of E. tarda strains to HEp-2 cells well correlated with their HA patterns against guinea pig erythrocytes described previously, where the HA of E. tarda FK1051 and KG8401 was enhanced by the increase of NaCl concentration in the culture media (Yasunobu et al, 2006). The NaClinduced adherence was also described in Salmonella typhi (Tartera and Metcalf, 1993), in which the adherence ability to Henle 407 epithelial cells increased under higher osmolarity (until 0.3 M NaCl) of the culture medium.…”

“…The NaClinduced adherence was also described in Salmonella typhi (Tartera and Metcalf, 1993), in which the adherence ability to Henle 407 epithelial cells increased under higher osmolarity (until 0.3 M NaCl) of the culture medium. Our previous infection experiments with E. tarda FK1051 showed that the 3%-NaCl culture was more virulent to Japanese founder than the 0%-NaCl culture, when fish were challenged orally, and thus we speculated that NaCl-induction of HA is important for adherence of E. tarda to the intestinal epithelial cells of fish (Yasunobu et al 2006). The present result, i.e.…”

“…Three strains of E. tarda, representing the different types of HA described previously (Yasunobu et al 2006), were used: strain FK1051 (type A) isolated from diseased Japanese flounder Paralichthys olivaceus, strain KG8401 (type B) from diseased Japanese eel Anguilla japonica, and a non-clinical strain SU166 (type C). These strains were pre-cultured on Trypto-Soya Agar (TSA, Nissui) at 30∞C for 24 h. According to the method described before (Yasunobu et al, 2006), each of the pre-cultured E. tarda strains was inoculated into 10 mL of a liquid medium consisted of 1% peptone-0.5% yeast extract (pH 6.5).…”

“…These strains were pre-cultured on Trypto-Soya Agar (TSA, Nissui) at 30∞C for 24 h. According to the method described before (Yasunobu et al, 2006), each of the pre-cultured E. tarda strains was inoculated into 10 mL of a liquid medium consisted of 1% peptone-0.5% yeast extract (pH 6.5). The bacterial suspension was diluted 100-fold in the same medium, and then 100 mL of the dilution was inoculated into 10 mL of the liquid medium supplemented with 3% NaCl or without NaCl.…”

“…Recently, Sakai et al (2003Sakai et al ( , 2004 reported that a fimbrial major subunit (19.3 kDa protein) is associated with the mannose-resistant hemagglutinating activity (HA) in E. tarda. Furthermore, our previous study revealed that the HA of E. tarda was induced by high (3%) NaCl concentration in the culture medium and E. tarda strains were classified into three types; type A showed HA only with the 3%-NaCl culture, type B exhibited HA in both 0%-and 3%-NaCl cultures, and type C demonstrated no HA in both the cultures (Yasunobu et al, 2006).…”