Growth of Flavobacterium psychrophilum in fish serum correlates with pathogenicity

Abstract

Flavobacterium psychrophilum isolates, obtained from ayu, Plecoglossus altivelis, three species of salmonids and two species of cyprinids in Japan, were used in this study. Bacteria were inoculated to serum prepared from ayu or red spotted masu trout (RSMT), Oncorhynchus masou ishikawae, and incubated at 18 °C for 24 h. All isolates (n = 19) from ayu grew well with a 9- to 116-fold increase of CFU in ayu serum, while CFU decreased markedly in RSMT serum. In contrast, isolates (n = 17) from fish species other than ayu exhibited no growth in ayu serum, but some isolates from salmonids survived or grew (1.2-23.5 fold increase of CFU) in RSMT serum. The isolates that could not survive or grow in ayu and RSMT sera grew well in both heat-inactivated sera of ayu and RSMT. Experimental infection by intraperitoneal injection showed that ayu isolates examined were all pathogenic to ayu but not to RSMT, while none of the isolates from salmonids and cyprinids were pathogenic to ayu but some showed pathogenicity to RSMT. These results indicate that the in vitro growth ability of F. psychrophilum isolates in fish serum correlates well with their pathogenicity to fish, particularly in ayu.

Population structure of the fish pathogen Flavobacterium psychrophilum at whole-country and model river levels in Japan

“…Institutions that provided these isolates and previous publications on these isolates are listed [11,14,16,44-47]. …”

A Review of Flavobacterium Psychrophilum Biology, Clinical Signs, and Bacterial Cold Water Disease Prevention and Treat

“…However, F. psychrophilum infections have been reported in a wide range of both anadromous and non-anadromous salmonids of various sizes [34][35][36][37][38][39][40][41][42]. In addition, F. psychrophilum has either caused disease or been detected in Japanese eel Anguilla japonica [43], European eel Anguilla anguilla [44], common carp Cyrpinus carpio [44], crucian carp Carassius carassius [44], tench Tinca tinca [44], ayu Plecoglossus altivelis [27,29], pale chub Zaco platypus [28], perch Perca fluviatilis [45], and roach Rutilis rutilis [45].…”

“…There are also a number of distinct genetic lineages, with the number appearing to increase with the refinement of molecular DNA techniques [19,20,40,79] with considerable genetic variation and variation in virulence among strains [19,25,45,80,81]. Strain virulence may also be fish species specific [42]. Based on RAPD (Random Amplification of Polymorphic DNA) results, Chakroun et al [83] suggested that North America was the source of F. psychrophilum in Asia, and a separate strain from Europe was transferred to Australia and then back to Europe.…”

Complete genome sequence of the fish pathogen Flavobacterium psychrophilum ATCC 49418T

“…In addition, molecular analysis of the population structure of this bacterium suggests that there are a number of distinct lineages [ 7 ]. It has been speculated that some strains are species specific [ 9 ] while others are location specific [ 10 ]. Some strains have also been observed to cause only either BCWD or RTFS [ 7 ].…”