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Title of article :
The virulence of Enterococcus to freshwater prawn Macrobrachium rosenbergii and its immune resistance under ammonia stress
Author/Authors :
Cheng، نويسنده , , Winton and Chen، نويسنده , , Jiann-Chu، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2002
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Abstract :
Growth of pathogen bacterium, Enterococcus was not affected in tryptic soy broth (TSB) medium containing ammonia-N concentration in the range of 0–5·14 mg l−1. Giant freshwater prawnMacrobrachium rosenbergii (8–12 g) were challenged with Enterococcus which had been incubated for 24 h in TSB medium containing different concentrations of ammonia-N at 0–5·14 mg l−1. Cumulative mortality of M. rosenbergii was higher for the bacteria incubated in TSB medium having ammonia-N at 0 and 0·26 mg l−1, than those incubated in TSB medium having 1·28, 2·57 and 5·14 mg l−1ammonia-N after 24 h of challenge. However, cumulative mortality of prawn was significantly higher for the bacteria incubated in TSB medium with no ammonia added after 120 h of challenge. The prawns (8–12 g) were challenged with Enterococcus previously incubated in TSB medium for 24 h, then placed in water having concentrations of ammonia-N at control (0·06 mg l−1), 0·55, 1·01, 1·68 and 3·18 mg l−1. Mortality of prawns increased directly with ammonia-N concentrations after 72 h challenge. The pranws (20–30 g) which had been exposed to control, 0·55, 1·68 and 3·18 mg l−1ammonia-N for 7 days were examined for the total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase activity and respiratory burst of haemocytes. Phenoloxidase activity decreased when the prawns were exposed to ammonia-N greater than 0·55 mg l−1. The respiratory burst increased significantly at 0·55 mg l−1, but decreased significantly at 1·68 and 3·18 mg l−1ammonia-N. No significant difference in haemocyte count was observed among the prawns at different ammonia-N concentrations. It is suggested that ammonia in water decreases the virulence of Enterococcus, and reduces the immune resistance of M. rosenbergii.
Keywords :
virulence , haemocyte count , phenoloxidase activity , Macrobrachium rosenbergii , Enterococcus , Ammonia , Challenge , Superoxide anions
Journal title :
Fish and Shellfish Immunology
Journal title :
Fish and Shellfish Immunology
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