Effect of benzalkonium chloride stress on immune resistance and susceptibility to Lactococcus garvieae in the giant freshwater prawn Macrobrachium rosenbergii.
Addition of benzalkonium chloride (BKC) at 0, 0.3, 0.6 and 1.0 mg l(-1) to tryptic soy broth (TSB) had no effect on growth of Lactococcus garvieae, a bacterial pathogen of the giant freshwater prawn Macrobrachium rosenbergii. However, injection of the cultured cells into prawns at a dose of 4 x 10(6) colony-forming units (cfu) prawn(-1) resulted in significantly higher mortality at 120 h (p < 0.05) in prawns injected with cells grown in the absence of BKC than in prawns injected with cells grown in the presence of BKC. In other experiments, prawns were injected with TSB-grown L. garvieae (4 x 10(6) and 3 x 10(5) cfu prawn(-1)) and then held in water containing BKC at 0, 0.3, 0.6 and 1.0 mg l(-1). After 120 h, mortality was significantly higher in all the BKC treatments than in the control without BKC. Prawns showed no significant differences in total hemocyte count (THC) or differential hemocyte count (DHC) amongst treatment and control groups. However, 96 h exposure to 0.3 mg l(-1) BKC or more resulted in a decrease in phenoloxidase activity and an increase in respiratory burst to levels considered to be cytoxic. In summary, exposure of L. garvieae to BKC at 0.3 mg l(-1) or more decreased its virulence to M. rosenbergii, while exposure of M. rosenbergii to BKC at 0.3 mg l(-1) or more increased its susceptibility to L. garvieae infection.
Cheng
Winton
W
Department of Aquaculture, National Pingtung University of Science and Technology, Pingtung, Taiwan 912, ROC.
Wang
Ching-Hsien
CH
Chen
Jiann-Chu
JC
D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004198:Disease Susceptibility / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D006434:Hemocytes / Q000187:drug effects; D017045:Lactococcus / Q000254:growth & development / Q000472:pathogenicity*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009026:Mortality; D033541:Palaemonidae / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology*; D016897:Respiratory Burst / Q000187:drug effects; D016019:Survival Analysis
D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds; D014442:Monophenol Monooxygenase