Isolation Listeria of fresh and smoked silver carp (Hypophtalmiss molitrix)

Listera was widely distributed in the general environment including fresh water, coastal water and live fish from this area. Listeria is the one of important bacteria that is caused food poisoning in hymen Listeriosis was a food-born disease which primarily affect people in particular risk-group (immune-suppressed, elderly, neonates) in which lethality was as high as 25% (Gram 2004). In this research, 30 samples of Silver carp (Hypophtalmiss molitrix) were studied for Listeria contamination and were examinated 15 samples were fresh and 15 samples smoked in 6 days. Sampling was done from muscle and after preparation suspension and plating in selective media; samples were incubated in 30oC for 48-72 hours. Finally, blue colonies were selected and examinated for primary and biochemical tests. Results showed that from 30 samples, 17 samples (56%) contaminated to Listeria that share of fresh fish, were 6 samples (35%) and share of were smoked 11 samples (65%). Tow species of Listeria are isolated (innocua and monocytogenes) that share of monocytogenes in fresh fish was 4 samples and is smoked fish was 4 samples and share of innocua in fresh fish was 3 samples and in smoked fish was 11 samples. From two species of Listeria, monocytogenes have important for pathogenicity in human and animal but innocua is second stage. Whole smoked Silver carp due to improper handling in smoking time, have high risk contamination to Listera. Time temperature of smoking (20-30oC), not only haven't inhibitory effect on Listeria but also is optimum temperature for this bacterium.