title: The virulence of Enterococcus to freshwater prawn Macrobrachium rosenbergii and its immune resistance under ammonia stress.
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 prawn Macrobrachium 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(-1) ammonia-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 (-1) ammonia-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 3.18mg (-1) ammonia-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.
authors.affiliation: Department of Aquaculture, National Pingtung University of Science and Technology, Pingtung, Taiwan, Republic of China.
authors.forename: Winton
authors.initials: W
authors.lastname: Cheng
authors.forename: Jiann-Chu
authors.initials: JC
authors.lastname: Chen
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D015169:Colony Count, Microbial; D003470:Culture Media; D004198:Disease Susceptibility / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D016983:Enterococcus / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D006434:Hemocytes / Q000187:drug effects*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000378:metabolism; D033541:Palaemonidae / Q000276:immunology / Q000382:microbiology*; D016897:Respiratory Burst / Q000187:drug effects; D016019:Survival Analysis; D014774:Virulence
chemical_list: D003470:Culture Media; D000641:Ammonia; D014442:Monophenol Monooxygenase