Pseudomonas anguilliseptica isolated from Baltic herring Clupea harengus membras with eye lesions

Abstract

Strains of Pseudomonas anguilliseptica were isolated from Baltic herring Clupea hdrpngus membras L. caught on the southwest coast of Finland and showing hernorrhages in the rvrs. When compared to the type strain of P anguilliseptica (NChlB 1949), the strains exdmined showed only minor biochemical differences. The strdins isolated from Bdtic herring \yere of low pathogenicity to rainbow troul Oncorhynchus mykiss. This is the first isolation of P anguilliseptica from wild fish, dnd the possibility of the wild fish sening ds a \.cctor of this pathogen lor farmed salmonlds 1s discussed K E Y WORDS Pseudomonds anguilliseptjca Clupea harengus membras . Baltic Sea Eyc lesion Pseudomonas anguilliseptica was originally isolated from pond-cultured Japanese eels Anguilla japonica suffering from 'Sekiten-byo', i.e. red spot disease (Wakabayashi & Egusa 1972). Later on, the infection occurred in eels farmed in Taiwan (Kuo & Kou 1978), Scotland (Nakai & Muroga 1982, Stewart et al. 1983), Denmark (Mellergaard & Dalsgaard 1986), and France (Michel et al. 1992). The bacteria were also isolated from cultured black sea bream Acanthopagrus schlegeli (Nakajima et al. 1983) and ayu Plecoglossus altivehs (Nakal et al. 1985). In Finland, Pseudomonas anguilljseptica caused disease outbreaks in farmed salmonid fish in 1986 (Wiklund & Dalsgaard 1987, Wiklund & Bylund 1990). An increasing number of Finnish fish farms have been suffering from the disease in recent years (unpubl. results). To our knowledge, however, there are no previous reports concerning isolation of P anguilliseptica from wild fish. This paper describes the characteristics of PseudoAddressee for correspondence monas anguilliseptica isolated from Baltic herring Clupea harengus membras L. with eye lesions. The fish were caught on the southwest coast of Finland. Material and methods. Fish sampling: Baltic herring to be examined were caught with standing gill nets and bow nets in May and June 1990 and 1991, near the town of Pan, In southwestern Finland. The fish were transported to our laboratory for bacteriological examination A total of 21 fish were examined. Bacteriological sampling: Bacteriological samples were taken from the eyes, liver, spleen, and kidney of the fish. The primary sola at ions were made on tryptic soy agar (Difco Laboratories, Detroit, MI, USA) supplemented with 5 '% bovine blood. The final NaCl concentration in the medium was 1.5 %,. The inoculated agar plates were incubated for 7 d at 20 C before being disca.rded. The type strain of Pseudornonas anguilliseptica, NCMB 1949, was included as a reference strain. Four strains of P angujll~septica recently isolated from wild and c.ultivated Atlantic salmon Salrno salar and sea trout Salmo trutta m trutta, obtained from the same sampllng area as the herring, were tested concurrently. Biochemical tests: The biochemical characteristics of the isolates were examined according to the methods described by Cowan (1974), MacFaddin (1983), and Wiklund & Bylund (1990). The O/F test was performed on a medium modlfled for marine bactena (MOF) (Leifson 1963). The ability of the strains to produce acid from carbohydrates was tested using the following sugars: arabinose, fructose, lactose, mannose, salicin, sucrose, and trehalose. The cytophaga agar was made according to Anacker & Ordal (1959) except that the amount of agar was increased to 15 g 1-' to facilitate streaking. The sensitivity of the isolates to different chemotherapeutants was 0 Inter-Research 1994 144 Dls. aquat. Org. Table 1. Pseudornonas anguilliseptica. Isolation rate from different organs of Baltic herring Organ No. infected / l%.