First isolation and identification of Vibrio vulnificus (biotype 2) from cultured beluga, huso huso in Iran

By decreasing sturgeon stocks in the Caspian Sea, rearing different sturgeon species especially Huso huso was increased in Iran. Under stress conditions the sturgeon can easily be infected by several opportunistic pathogens. In June 2011, mortality happened in 25 - 28°C water temperature, in one of the most important cultured sturgeon farms in Mazandaran province, north of Iran. The mortality rate was 15%. The first clinical signs in moribund fish were lethargy and anorexia. A total of 20 moribund fish was transferred to a central laboratory for more bacteriological examination. Clinical signs including several deep ulcers on body surface, around the head, under operculum, ulcers at the base of the pectoral fins, hemorrhage around the anus, operculum, and pale gills were observed in moribund fish. The main internal signs were hepatomegaly and splenomegaly, liquid accumulation in the intestine and diffuse visceral hemorrhage. The results of morphology and microscopic characterizations and also biochemical tests indicated that Vibrio vulnificus (biotype 2) was the etiological agent of mortality in infected fish. This study was the first report of V. vulnificus in cultured H. huso in Iran

The effect of nisin A and sodium benzoate on behavior of Listeria monosytogenes and some microbial and chemical parameters in silver carp (Hypophtalmichtys molitrix) fillet stored at 4˚C

The effect of nisin A and sodium benzoate on Listeria monocytogenes, as well as some microbial (mesophilic, psychrotrophic and lactic acid bacteria) and chemical (peroxide and TVN) in silver carp (Hypophtalmichtys molitrix) fillet during storage period (0, 3, 6, 9 and 12 days) at 4˚C were evaluated. For this, Listeria monocytogenes (4 logCFU/g) was inoculated to the fillets and were dipped into 2% sodium benzoate solution for 15 min and left to stand for 10 min at 4˚C. Subsequently nisin A was added to the fillet (0/15 g/kg) and samples were kept at 4˚C while packaged in vacuum condition. The results showed that, application of nisin A and sodium benzoate decrease the number of Listeria monocytogenes from 4/12 to 3/66. However, in control groups the number of bacterium was increased from 4/43 to 5/14. Moreover, the number of mesophilic bacteria in treatment and control groups was increased from 4/39 to 6/79 and 4/48 to 7/93, respectively. The number of psychrotrophic bacteria in treatment and control groups was increased from 4/16 to 6/72 and 4/34 to 7/92, respectively. The similar result was achieved for lactic acid bacteria in which the number of these bacteria was increased from 2/74 to 4/08 and 2/9 to 4/78, respectively. Moreover, different peroxide value and TVN for treatment and control groups was achieved. In conclusion, application of nisin A and sodium benzoate showed different inhibitory effects on Listeria monocytogenes in culture media and silver carp