Psychrobacters and Related Bacteria in Freshwater Fish

Abstract

Three phenotypic identification systems were employed to identify 106 strains of gram-negative, nonmotile, aerobic bacteria obtained during iced storage of wild (Salmo trutta and Esox lucius) and farmed (Oncorhynchus mykiss) freshwater fish. Using diagnostic tables and computer-assisted identification, the isolates were Psychrobacter (64 strains), Acinetobacter (24 strains), Moraxella (6 strains), Chryseobacterium (5 strains), Myroides odoratus (2 strains), Flavobacterium (1 strain), Empedobacter (1 strain), and unidentified (3 strains). Overall similarities of all strains were determined for 108 characters by numerical analysis (simple matching coefficient of similarity [S] and clustering by unweighted pair group average linkage [UPGMA]). At the 77% similarity level, 92 strains formed nine major clusters (3 or more strains) and four small clusters (2 strains). Cluster 1 (25 isolates divided into two main subclusters) could be assigned to Psychrobacter phenylpyruvicus, clusters 2 and 3 (26 isolates) were designated as Psychrobacter immobilis, and clusters 4 (3 isolates) and 7 (4 isolates) were identified as Psychrobacter urativorans and Psychrobacter spp., respectively. Clusters 5 (five isolates), 6 (three isolates), and 9 (five isolates) were labeled as Acinetobacter spp., Acinetobacter johnsonii, and Acinetobacter lwoffii, respectively. Cluster 8 (12 isolates), with a high resemblance to Thornley's phenon 4 (a heterogeneous group of bacteria isolated from poultry and related to Acinetobacter), remained unnamed. The restriction pattern was identical for strains grouped into clusters 2 and 3 (P. immobilis) but was different for the remaining Psychrobacter isolates. A large proportion of isolates belonging to the family Moraxellaceae were closely related. Psychrobacters and A. johnsonii were present in freshly caught fish and river water. In the latter stages of storage, P. phenylpyruvicus and acinetobacters tended to decrease, whereas P. immobilis increased.

Diversity and antibiotic resistance of Acinetobacter spp. in water from the source to the tap

“…Acinetobacter spp. have been isolated from contaminated soils (Vanbroekhoven 2004), freshwater fish (Gonzalez 2000), raw milk (HantsisZacharov and Halpern 2007), or human skin (Seifert 1997).…”

The Bacterial Microflora of Fish

“…The bacteria from the surface of freshwater fish have been reported to include Acinetobacter johnsonii [58], aeromonads (notably Aeromonas hydrophila, A. bestiarum, A. caviae, A. jandaei, A. schubertii, and A. veronii biovar sobria [59]), Alcaligenes piechaudii, Enterobacter aerogenes, Escherichia coli, Flavobacterium [25], Flexibacter spp., Micrococcus luteus, Moraxella spp., Pseudomonas fluorescens, psychrobacters [58], and Vibrio fluvialis [23,56,60]. To some extent, the presence of aeromonads reflected whether or not the water in which the fish occurred was polluted or clean [59].…”

Acinetobacter johnsonii and Acinetobacter lwoffii - the emerging fish pathogens

“…The members of Acinetobacter are widely distributed in the nature. They occur commonly in soil, marine fish, and water (2,8,15), freshwater fish (13), and vegetables (4,12).…”