First description of nonmotileVibrio vulnificusstrains virulent for eels

Abstract

Nonmotile Vibrio vulnificus strains were isolated as pure cultures from body ulcers and internal organs of wild diseased European eels caught in a Mediterranean freshwater coastal lagoon. All 54 V. vulnificus isolates were nonmotile, indole-, ornithine decarboxilase-, mannitol- and cellobiose-positive, developed the opaque variant in culture, belonged to the O-antigenic serovar A and were highly virulent for eels by both intraperitoneal injection and immersion challenges. The nonmotile phenotype found in our V. vulnificus isolates was stable: nonmotile cells were always recovered from experimentally infected eels; no variation in the immobility of the V. vulnificus cells was observed for repeated subculture by daily passages on solid media, at different temperatures or incubation times and with or without magnesium sulfate. Many of the fla genes of Vibrio were present in the genome of the nonmotile strains (flaCDE and flaFBA for flagellins and flaH for the distal capping protein), although we observed by transmission electron microscopy that these V. vulnificus strains always lacked the polar flagellum. This is the first report on the existence of nonmotile wild-type V. vulnificus strains.

Seasonal recovery of Edwardsiella piscicida from wild European eels and natural waters: Isolation methods, virulence and reservoirs

“…Second, the historical series of edwardsiellosis at the L′Albufera Lake (2003, 2004, 2005, 2008 and 2014 surveys), with total prevalence values ranging from 5%-11.8% (Esteve & Alcaide, 2009;Esteve et al, 2017; present study), better indicated that edwardsiellosis could be a native bacterial disease. However, neither this long incidence period nor the prevalence values observed fit with the "outbreak" concept, in contrast to that observed for other bacterial diseases (Esteve et al, 2007(Esteve et al, , 2017.…”

Phenotypic and genotypic characterization of a new fish-virulent Vibrio vulnificus serovar that lacks potential to infect humans

“…The only exception was the motility characteristic, which was negative for two isolates from wild eels. The lack of motility has already been reported in other typically motile bacterial pathogens (Fouz et al, 2006b;Gardel & Mekalanos, 1996), including V. vulnificus (Esteve et al, 2007). The use of vaccination against V. vulnificus at farms (Esteve-Gassent et al, 2004) could have favoured the emergence of these non-motile strains by selective pressure against flagellar antigens, similarly to what has occurred with other motile fish pathogens (Fouz et al, 2006b).…”

Vibrio infection in freshwater fish in Poland

“…Biotype 1 is ornithine decarboxylase-and indole-positive, biotype 2 is orni-thine decarboxylase-and indole-negative, and biotype 3 is cellobiose-negative (Tison et al 1982, Bisharat et al 1999, Warner and Olivier 2008. In addition, Esteve et al (2007) described wild-type V. vulnificus biotype 2, serovar A strains, which were non-motile due to the lack of a sheathed polar flagellum. The literature indicates that three biotypes are potentially pathogenic for humans (Baker-Austin et al 2018).…”