Recovery of Bacillus mycoides, B. pseudomycoides and Aeromonas hydrophila from common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) with gill disease.

During a 3-month period from June to the end of August 2016, ~5% mortalities were observed in a farm with rainbow trout (Oncorhynchus mykiss Walbaum) and one farm of common carp (Cyprinus carpio L.) in Bulgaria. The disease was manifested by gill ulcers/rot, asphyxiation and bloody ascites. Aeromonas hydrophila was isolated from the internal organs of all the diseased fish. Bacillus mycoides or B. pseudomycoides were recovered from the gill lesions on diseased carp and rainbow trout, respectively, with identification achieved by conventional phenotyping and by sequencing of the 16S rRNA gene. In vivo experiments confirmed that all three organisms were pathogenic to rainbow trout.

Recovery of Hafnia alvei from diseased brown trout, Salmo trutta L., and healthy noble crayfish, Astacus astacus (L.), in Bulgaria.

Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4.

Identification and pathogenicity to rainbow trout, Oncorhynchus mykiss (Walbaum), of some aeromonads.

Twelve strains of fish pathogenic aeromonads were identified by 16S rRNA sequencing as Aeromonas bestiarum, A. hydrophila, A. hydrophila subsp. dhakensis, A. salmonicida subsp. salmonicida, A. sobria biovar sobria and A. veronii biovar sobria. Following intramuscular injection, A. hydrophila subsp. dhakensis caused dark liquefying, raised furuncle-like lesions in rainbow trout within 48 h. Extracellular products of all cultures contained gelatinase and lecithinase, and most revealed lipase. Congo red absorption and siderophore production was recorded, but not so the suicide phenomenon or slime production. Sodium dodecyl sulphate polyacrylamide gel electrophoresis profile of the outer membrane proteins (OMP) revealed 10-25 bands, of which major bands were seen in the region of 32.5-47.5 and 62-83 kDa. Marked heterogenicity of the OMP and whole cell protein (WCP) profiles within and among the species was observed. Polypeptides of 83-173 kDa were detected in the WCP profile of the cultures, but they were not expressed in OMP fractions.

Properties of Yersinia enterocolitica and Yersinia pseudotuberculosis in red blood cell concentrate of different ABO groups during 30-day storage at 4 degrees C.

OBJECTIVE: The present study aimed to investigate the psychrophilic properties of Yersinia enterocolitica and Yersinia pseudotuberculosis as contaminants of donated blood. METHODS: Bags with red blood cell concentrates (RBCCs) of A, B, and AB blood groups were inoculated with a bacterial suspension of Y. enterocolitica (0 : 3 and 0 : 8) and Y. pseudotuberculosis (serovars I and III) and stored at 4 degrees C for 30 days. Bacterial growth was measured at selected intervals after inoculation. Initial strains and their subcultures (isolated after 30 days' incubation at 4 degrees C) were tested for glycolytic activity and susceptibility to the bactericidal action of human serum. RESULTS: It was found that all strains grew well in the RBCCs of A, B, and AB groups. After incubation at 4 degrees C they increased their glycolytic activity and became more sensitive to the killing ability of human serum. CONCLUSIONS: The prolonged storage of contaminated Y. enterocolitica and Y. pseudotuberculosis RBCCs at 4 degrees C induces bacterial multiplication to high levels and stimulates glycolytic activity of bacterial cells.