Isolation and biochemical properties of Aeromonas hydrophila hydrophila in rainbow trout
Baltić, Milan Ž.
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Aeromonas hydrophila spp. is commonly present in water and in certain incidences they might cause diseases in fish and amphibians. Humans are infected by ingestion of these bacteria with contaminated food or water. Aeromonas hydrophila spp. might cause gastro-intestinal disorders and poisoning in humans. One of the major issues associated with Aeromonas hydrophila and incidence of gastro-intestinal diseases is accurate identification of aeromonades at the species level. Therefore, there is a need for a clear phenotypic scheme and biochemical characterization of the mentioned species. Objective of this paper was to study the presence of Aeromas hydrophila in trout samples and to test biochemical characteristics of isolated strains. For isolation of Aeromonas hydrophila species, 120 samples of rainbow trout, commercially available, were studied. Aeromonas hydrophila was isolated from fish muscle tissue and skin according to "Microbiological Methods for the Meat Industry", second edition ...(1991) Biochemical studies were performed on Aeromonas hydrophila medium, followed by oxidase test (+), catalase test (+), staining according to Gram (-) and vibriostat test agar (0/129, vibriostatic), as well as biochemical tests API 20E and API 20NE. From the 120 studied rainbow trout samples, 12 strains of Aeromonas hydrophila were isolated, out of which seven strains (58.3%) of Aeromonas hydrophila belonged to group 1, whereas five strains (41,6%) belonged to Aeromonas hydrophila group 2. Out of 12 isolated strains, 11 (91.7%) had β-galactosidase. They were citrate and indol positive, sorbitol negative, arabinose positive, NO2 - producing and reducing it to N2. Then (83.3%) of 12 twelve isolated strains were Voges-Proskauer positive and melibiose negative, whereas eight (66.7%) were amigdalin and lysine-decarboxylase positive. It was established that seven of 12 twelve strains (58.3%) ferment glucose. The obtained results demonstrate the need to supplement phenotypic schemes for identification of Aeromonas hydrophila strains originating from fish at the species level.
Keywords:Aeromonas hydrophila / Biochemical characterization / Rainbow teout (Oncorhynchus Mykiss)
Source:CEFood 2012 - Proceedings of 6th Central European Congress on Food, 2012, 364-369
- University of Novi Sad, Faculty of Technology